CA3146745C - Method for the preliminary use of an at least partially constructed lower reservoir for an underwater pumped-storage power plant - Google Patents

Abstract

A method for the preliminary use or test operation of an at least partially constructed lower reservoir for an underwater pumped-storage power plant, wherein the at least partially constructed lower reservoir is located in a dry but floodable ground depression, the method comprising: constructing at least one preliminary upper reservoir above the at least partially constructed lower reservoir, the upper reservoir not being identical to the dry ground depression, and connecting the at least partially constructed lower reservoir to the preliminary upper reservoir via a penstock so that the lower reservoir can be used on a preliminary basis in such a way that electrical energy is generated when water is admitted into the lower reservoir from the preliminary upper reservoir and electrical energy is stored when water is pumped from the lower reservoir into the upper reservoir.

Description

METHOD FOR THE PROVISIONAL USE OF AN AT LEAST PARTIALLY CONSTRUCTED

LOWER RESERVOIR FOR AN UNDERWATER PUMPED STORAGE POWER PLANT

FIELD OF INVENTION

The invention relates to the provisional use of an at least partially constructed lower reservoir for an underwater pumped storage power plant, which is built in a dry but floodable ground depression, in particular in an abandoned or still operated open pit mine. The invention is particularly suitable for test operation and for energy generation during the construction of an underwater pumped storage power plant in the Hambach open pit mine or other lignite mining areas.

BACKGROUND OF THE INVENTION

The energy transition requires short- and long-term storage facilities The "energy turnaround" includes the almost complete coverage of the electric power supply by regenerative energies (RE) and here primarily by wind and photovoltaics (PV), whereby at the same time the use of electricity is also to be extended to the heat sector and the transport sector (sector coupling). Due to the uneven supply of RE caused by weather and astronomy, whereby even short- lived regular "dark lulls" can occur, the energy turnaround can only be implemented with the use of storage. In contrast to deterrent calculations, which exclusively assume short- term storage (such as pumped storage power plants (PSKW) and then warn of an "energy transition to nowhere" (/Sinn 2013/), the storage problem can only be managed by a combination of short-term and long-term storage (in the form of P2G gas storage). This combination was modeled using the "two-storage model" (e.g. /LuSchm13_2014/; /AKE2014F/, /Lu2016/, /DOren 2017/). It was found that a short-term storage capacity of only 0.20 to 0.30 full load days will be sufficient for Germany (/Lu2016/), unless extreme cost increases are assumed.

However, the assumption was always made that the spoking time would be around 5 or 6 hours, which has been typical for PSKWs up to now. If it were possible to significantly reduce the partial specific costs for the pure storage volume, one could also think about keeping larger volumes in reserve, which would be used less frequently, but would then continue to use the turbines of short-Date Recue/Date Received 2022-01-10 CA03146745 2022-01-10 term storage facilities that have already been emptied of energy. Reference is made to the corresponding considerations on "reserve storage" in (/LuSchmB Bergei2/) and there in particular in the chapter: "3.3 Reserve deep storage lb: - Blind shafts for somewhat longer storage periods".

The current electricity consumption of the Federal Republic of Germany is about 600 [TWh/a]. Due to sector coupling, we assume a significant increase in electricity consumption for the completed energy turnaround - despite all efforts to save energy - and base our calculations on a German annual consumption of Q_a= 1000 [TWh/a], which corresponds to an average daily consumption of Q_d= 2.74 [TWh/a]. The average output is then 114 GW.

Opencast lignite mining as a site for PSKW

Overall, it can be said that there is strong research activity in Germany in the field of underground PSKWwith reference to hard coal mining, but only isolated publications on the subsequent use of opencast lignite mines. This is also reflected, for example, in the entries on the Underground PSKW topic page ihttp://www.upsw.de/index.php/de/startseite.html).

However, the great potential of abandoned areas of opencast lignite mining as sites for pumped storage power plants was also recognized at an early stage. For example, Siol (/Siol 1995/) describes in DE19513817B4 a pumped storage power plant characterized by the fact "that the lower and upper storage basins are located in an existing or cleared lignite deposit".

The state of the art up to 2012 is comprehensively presented in two research reports of the Forschungszentrum Mich. In the STE -Research Report 08/2011 (/Baufume e.a. 2011/), a short synopsis on "underground pumped storage", chapter 111.2 is dedicated to PSKW in opencast lignite mining. Two basic concepts are distinguished: (1.) In the underfloor PSKW concept according to (/Schreiber e.a. 2010/), the pipes, cavities and installations that will be required later can already be built on the lowest level and the machine .. components can be equipped during the operation of the open pit. This is followed by a covering with overburden material and finally the upper basin is designed as a residual lake on the cover. 2 Date Recue/Date Received 2022-01-10 CA03146745 2022-01-10 (2.) In the concept "PSKW in an open pit residual lake" according to /Schulz 2009/, two partial lakes are separated from each other by a dam. The sub-lake located in the shallower area serves as the upper basin; the sub-lake located considerably deeper serves as the lower basin, the level of which is lowered to such an extent that the difference in level to the upper lake is as great as possible, and the remaining residual volume can be pumped into the initially empty upper lake.

In the STE -Research Report 03/2012 /Stenzel ea. 2011/, "Unconventional Energy Storage", the two basic concepts are further elaborated in Chapters IV 1.5 and IV 1.6, respectively, variations and projects are given and, in particular, the operating characteristics are investigated.

The following chapter IV 1.7 of this report is dedicated to the principle of hollow sphere storage, in which hollow spheres are lowered from the sea surface to the seabed. Here, the possible use of these reservoirs in the marine area is discussed and the "open" coastal areas are surveyed.

Anew study by the Wuppertal Institute /Thema 2019/ shows in a simple rough calculation for a large-scale pumped storage plant in the current opencast mines Hambach, Garzweiler and Inden that there is a significant technical storage potential of -in their calculation- up to 400 GWh available; this corresponds to about ten times the capacity of all current German PSKWs combined.

The authors' approach is to use a large and deep open pit as the lower basin and a smaller open pit as the upper basin. During energy storage, the water of the lower basin is completely pumped up into the upper basin, which is initially largely empty, except for a small residual amount.

This conventional idea is applied to the currently deepest and largest opencast lignite mine Hambach as the lower basin and the neighboring smaller opencast mines Garzweiler and Inden, which are to be hydraulically connected to each other, as the upper basin. To operate the PSKW, it is assumed that a minimum height difference of 100 m is maintained in every operating condition.

In the case of a realization, one would probably have to critically object that the operation-related alternate almost complete emptying of the basins represents a maximum brutal landscape intervention and cancels the requirement of recultivation. The sight of the "open pit holes," once 3 Date Recue/Date Received 2022-01-10 CA03146745 2022-01-10 approved as temporary, would continue unchanged; the groundwater that has flowed into the open pit hole up to now would also have to continue to be pumped out.

Underground and submarine PSKW

The "Sea Egg Principle": The "Sea Egg Principle" of moving an artificially created cavity to the seabed and using it there as the lower basin of a PSKW with the sea itself as the upper basin was published independently of each other and complementing each other by Alexander Slocum and co- workers /Slocum/ on the one hand and by Schmidt-Bocking and Luther (/Meerei_1/ and /Meerei_2/ on the other. The "Sea Egg "idea found resonance in the daily press /KOffner FAZ2011.0401/ and was taken up in Germany by a consortium led by Hochtief as the StEnSea (=

Stored Energy in the Sea) project (/StEnSea/). The results of the preliminary planning were presented by Hochtief-Solutions AG in a paper at the 7th International Storage Conference, 7th IRES

Conference November 7-12, 2012, and published as ppt- slides in the proceedings of this conference /Garg e.a.2012/. As a result, a planned pilot project for a "sea egg" was presented with the following data: = Hollow sphere with inner diameter of about 30 [m]. = Wall thickness. approx.- 3 [m] = Storage volume approx.: 12,000 [m3] = Storage capacity of approx. 20 MWh at a water depth of 700 [m]. = Pump turbine for approx. 5-6 [MW]; if we interpret the smaller power figure as turbine power, this results in a withdrawal time of 4 [h].

Construction Target Costs ("CTC") were submitted for this facility based on the following unit prices: = Concrete costs incl. formwork and reinforcement = 225 [Ã/m3]; this corresponds to a specific cost of 413 [Ã/kW] in relation to the installed power. = Pump-turbine and electromechanical accessories = 525 [Ã/kW].

In addition, significant costs were calculated for the installation of the hollow sphere on the seabed, which amounted to 300 Ã/kW when normalized to the installed capacity. Even with these costs, the sea egg would be competitive with other PSKW. 4 Date Recue/Date Received 2022-01-10 As can be seen, for example, when comparing the inner diameter with the specified volume, the data are rough and "round" calculated values on several levels, which do not always strictly fit together mathematically. In the following, we will often refer to the data provided under the name of "the StEnSea sphere" and - in order to facilitate recalculation - we will relate all volume-dependent values to the specified inner diameter of 30 m, which corresponds to an "ideal" volume of 14,100 [m3].

Furthermore, it was shown that the development goal consists in the deployment and interconnection of very many individual spheres to a large PSKW. The "Norwegian Channel" was indicated as a possible area of application, see e.g. /BMWi2017/.

In /LuSchmB 2011+13 -Bergei1+2/ an application within a mine constructed for storage purposes is further described, where deep-lying blind shafts are used as storage reservoirs, large-dimensioned shafts as penstocks with intermediate stations for the pump turbines and a surface water body as upper reservoir. In /LuSchmB 2014 -langeSaar/, a method is presented by which federal waterways can significantly increase their capacity as the upper reservoir of a large PSKWwith underground mine storage by proactively operating their impoundments.

In a report by Ruhr Uni /Ruhr Uni 2013/, several individual contributions deal with the structural design and optimization of concrete structures as a lower basin at the bottom of a residual lake built in a former opencast lignite mine, which serves as an upper basin. All designs are characterized by having a central tower for aeration, supply, and access to a cavern below. The water from the extensive storage structure flows together in this cavern, where it is fed to the pump turbines.

Various designs are being investigated as subbasins. Sanio and Mark investigate a dome-shaped shallow storage subbasin supported by cross walls or piers and anchored by piles in the subsoil. (see page 151 from /Sanio-Mark2013/).

Perau and Korn /Perau-Korn 2013/ investigate somewhat more general geotechnical issues in the construction of subsurface pumped storage reservoirs. They want to prevent resulting uplift forces of the storage structure by overfilling the entire storage structure with sediments. (see page 141 and page 144 of /Perau-Korn 2013/). 5 Date Recue/Date Received 2022-01-10 Object of the invention Object of the invention is supporting the construction of a large-scale pumped storage power plant in order to provide the necessary short-term storage capacity for the energy turnaround while keeping the ecological impact as low as possible despite the enormous storage capacity. The pumped- storage power plant should be as fault-friendly and safe as possible; in particular, test operation should be made possible during construction. Furthermore, it should be possible to use the pumped storage power plant for energy storage already during the construction phase, which may last several years.

GENERAL DESCRIPTION OF THE INVENTION

The invention relates to a method for the provisional use, in particular for test operation, of an at least partially constructed lower reservoir for an underwater pumped storage power plant, wherein the at least partially constructed lower reservoir is located in a dry-lying but floodable ground depression, in particular in an abandoned or still operated open pit mine, e.g. on a lower or the lowest floor of the open pit mine. The dry-lying ground depression is a depression that is at least not substantially filled with water, but can in principle be flooded in such a way that an artificial lake can be formed therein.

The at least partially constructed lower reservoir for the future subsea pumped storage power plant is designed or arranged to be operable, when the dry bottom well is flooded, such that electrical energy is generated when water is admitted into the lower reservoir from the flooded bottom well and electrical energy is stored when water is pumped out of the lower reservoir into the flooded bottom well.

According to the invention, a temporary upper reservoir is constructed above the at least partially constructed lower reservoir, which is not identical to the bottom depression and, in particular, is smaller than the dry bottom depression and/or has a smaller depth than the dry bottom depression, thus preferably has a smaller volume than the entire dry bottom depression.

Multiple upper reservoirs may also be constructed. Further, according to the invention, the lower reservoir, which 6 Date Recue/Date Received 2022-01-10 CA03146745 2022-01-10 has been built or will be built while the soil depression is still dry, is connected to the temporary upper reservoir via a (temporary) pressure line.

With the temporary upper reservoir and the (temporary) pressure line, the at least partially constructed lower reservoir can be provisionally utilized such that electrical energy is generated when water is admitted from the temporary upper reservoir (via the temporary pressure line) into the lower reservoir, and electrical energy is stored when water is pumped from the at least partially constructed lower reservoir (via the temporary pressure line) into the upper reservoir.

The process described above is also further explained with reference to figures and is referred to as the "interim process".

There are different possibilities to build a temporary upper reservoir.

According to one method variant, a temporary upper reservoir can be constructed by dividing the dry- lying ground depression, in particular the open pit, in such a way that a first partial area is created in which the at least partially constructed lower reservoir is arranged, and a second partial area is created which forms the temporary upper reservoir.

Such a division of the dry-lying soil depression into at least two subareas, one forming the higher- lying upper reservoir, may be accomplished in particular by the construction of a dam, a dam wall, or some other delineation. The temporary upper reservoir is thus in particular delimited from the dry- lying soil depression The temporary upper reservoir can, for example, be located on the slope of the still dry ground .. depression, preferably as far up as possible. For example, an upper reservoir can be created in the shallow part of the open pit by means of a dam that is flooded with water, leaving the actual deep open pit dry. The already assembled part of the lower reservoir can be connected to this upper basin by pipes, so that parallel to the lignite mining in the open pit, the lower basin-upper basin system can already be put into operation as a water pumping storage plant.

According to another process variant, which can be provided alternatively or additionally, a temporary upper reservoir can also be constructed by excavating or providing another soil 7 Date Recue/Date Received 2022-01-10 CA03146745 2022-01-10 depression next to the dry-lying soil depression, which forms the temporary upper reservoir, or by constructing a container or a basin next to the dry-lying soil depression, which forms the temporary upper reservoir. In general, in both process variants, the preliminary upper reservoir can be designed in particular as a container or as a basin.

According to a preferred process variant, the dry-lying ground depression, in particular the open pit, or the partial area in which the at least partially constructed lower reservoir is located, is further widened and/or deepened while the at least partially constructed lower reservoir is in test operation.

In other words, after the at least partially constructed lower reservoir has been connected to the preliminary upper reservoir and/or it has already been used or tested on a preliminary basis, the bottom depression may be further widened and/or deepened. Further widening and/or deepening can be done in particular with already existing open pit mining machines and/or for further extraction of mineral resources in open pit mining operations.

The test operation of the at least partially constructed lower reservoir makes it possible to gain experience and to adapt the further construction measures accordingly, in particular to ensure a high level of safety and fault tolerance of the subsequent underwater pumped storage power plant.

Accordingly, it can be provided that the at least partially constructed lower reservoir and/or the temporary upper reservoir is rebuilt and/or extended after it has been connected to the temporary upper reservoir and has preferably already been used or tested on a temporary basis, i.e. in particular experience from a test operation is already available.

The invention further relates to a method for converting a lower reservoir set up for provisional use, in particular for test operation, which is connected via a pressure line to a provisional upper reservoir (in particular as described above) into a subsea pumped storage power.

Here, a dry-lying ground depression in which the lower reservoir is located is flooded with water so that an artificial lake is formed therein which forms a final upper reservoir for the underwater pumped storage power. In other words, the dry-lying soil depression is later flooded with water to replace the temporary upper reservoir with an upper reservoir formed as an artificial lake in the soil depression, thereby completing the final underwater pumped storage power plant. 8 Date Recue/Date Received 2022-01-10 After flooding, the underwater pumped storage power can be operated such that electrical energy is generated when water is admitted from the flooded bottom depression into the lower reservoir and electrical energy is stored when water is pumped out of the lower reservoir into the flooded bottom depression.

Flooding of the dry-lying bottom pit, especially the open pit, can take a long time, sometimes years.

Even during flooding, the lower reservoir can initially continue to be used provisionally or tested by maintaining the provisional condition, i.e. by letting water from the provisional upper reservoir into the lower reservoir and/or pumping water from the lower reservoir into the upper reservoir.

Furthermore, it may be advantageous to already generate energy with the turbines, pumps and/or pump turbines that are already present during the flooding of the bottom cavity. It may therefore be advisable to flood the bottom cavity with water in such a way that the water is first let into one or more of the pressure vessels via a pressure line provided for this purpose, while supplying electrical energy, and then pumped out of the pressure vessel(s) into the bottom cavity, while absorbing electrical energy, in order to flood the bottom cavity step by step and thereby (net) generate electrical energy.

After or, if necessary, during flooding of the dry-lying soil depression, e.g., toward the end of flooding, the pressure line to the temporary upper reservoir may be disconnected and/or removed.

Furthermore, after or, if necessary, during the flooding of the dry-lying soil depression, and in particular after the pressure line to the temporary upper reservoir has been released, the temporary upper reservoir can be transformed into a reclamation lake.

The invention further relates to a preliminary pumped storage power plant. The preliminary pumped storage power plant comprises an at least partially constructed lower reservoir for an underwater pumped storage power plant, which is arranged in a dry-lying but floodable ground depression, in particular in an open pit, and which, when the dry-lying ground depression is flooded, is operable to generate electrical energy when water is admitted from the flooded bottom cavity into the lower reservoir and to store electrical energy when water is pumped out of the lower reservoir into the flooded bottom cavity. 9 Date Recue/Date Received 2022-01-10 Further, the preliminary pumped storage power plant comprises a preliminary upper reservoir arranged above the at least partially constructed lower reservoir, which is not identical with and in particular smaller than dry bottom well, wherein the at least partially constructed lower reservoir is connected to the preliminary upper reservoir via a (preliminary) pressure line, so that the lower reservoir can be used provisionally in such a way that electric energy is generated when water is admitted from the provisional upper reservoir into the lower reservoir and electric energy is stored when water is pumped from the lower reservoir into the upper reservoir.

In the following, further aspects are given concerning the method according to the invention mentioned at the beginning for the provisional use, in particular for the test operation, of an at least partially constructed lower reservoir for an underwater pumped storage power plant. Accordingly, the following further aspects also apply to the preliminary pumped storage power plant.

According to a further aspect, the at least partially constructed lower reservoir may comprise a plurality of pressure vessels arranged side-by-side and/or on top of each other in the dry-lying bottom cavity, e.g., on a lower floor of the open pit. Then, the or some of the pressure vessels forming the lower reservoir arranged in the bottom cavity may be connected to the temporary upper reservoir via the (temporary) pressure line.

Alarge number of pressure vessels can be provided or built on site, in particular a large number of similar pressure vessels that are or will ideally be mass-produced for cost reasons. The construction or mass production of the large number of pressure vessels is carried out in particular in the dry- lying soil pit, so that they are preferably available directly at the bottom of the soil pit. In the case of an open pit, for example, the pressure vessels can be built on a lower level of the open pit or even on the lowest level.

Thus, the many pressure vessels can be/are arranged side by side and/or on top of each other in the dry bottom cavity in order to form there the lower reservoir for the underwater pumped storage power plant to be built. In case of an open pit, the pressure vessels are/will be preferably arranged on a lower bottom or also on the lowest bottom side by side and/or one above the other. In this case, the pressure vessels can be/are arranged in such a way that the pressure vessels are/is arranged next to each other, in particular directly adjacent to each other, Le., that the pressure Date Recue/Date Received 2022-01-10 CA03146745 2022-01-10 vessels are/are arranged, for example, along one direction in a row next to each other or also along two directions in a grid or matrix next to each other. In addition, the pressure vessels may also be/be arranged one above the other, for example in a plurality of layers, which in turn may in particular be directly adjacent to one another, so that the pressure vessels are in contact with one another or are supported against one another.

Arranging the pressure vessels in the bottom cavity while it is still dry has numerous advantages.

For example, the pressure vessels can be built directly at the position where they are to be arranged, i.e. the process steps of building and arranging can form a common step. However, even if the pressure vessels are initially built at a different location, the subsequent arrangement can be carried out very precisely as long as the soil depression is still dry. In addition, machines working in the dry can be used for construction, processing and/or arrangement of the pressure vessels in the dry-lying depression, in particular open-pit mining machines, which may already be on site anyway.

The arrangement in the dry also makes it possible to conveniently link or equip the pressure vessels with connecting pipes, turbines, pumps, pump turbines, shafts, or other structural elements. It should also be noted that larger and more compact arrangements of pressure vessels can be erected in the dry than would be possible to subsequently sink them. Last but not least, the arrangement of pressure vessels in the still dry ground cavity is particularly cost-effective and flexible.

The use of a large number of pressure vessels, in particular a large number, has the advantage, among other things, that the pressure vessels can be built in mass production, which in turn saves costs and makes it possible to use pressure vessels with as simple or geometrically simple a shape as possible, which are not very susceptible to defects and are very reliable in terms of their statics.

As the lower reservoir of the pumped storage power plant to be built is composed of a large number of pressure vessels, a high degree of safety is also achieved because, in the event of a defect, only individual pressure vessels are affected, which then temporarily or permanently no longer contribute to the lower reservoir. At the same time, the use of many, especially similar, pressure vessels allows a high degree of design flexibility and subsequent expandability. 11 Date Recue/Date Received 2022-01-10 In particular, it can be provided that the at least partially constructed lower reservoir is modified and/or extended in such a way that further pressure vessels are arranged next to and/or above the already existing pressure vessels. This will be discussed in more detail below.

Preferably, the pressure vessels are designed, constructed or machined such that they each have at least one flow-through opening for admitting and/or discharging water so that they can serve as a lower reservoir for the underwater pumped storage power plant to be built.

Particularly preferably, the pressure vessels are also designed, constructed or, as the case may be, machined in such a way that they are sufficiently pressure-resistant to be able to be pumped empty in a dimensionally stable manner against a hydrostatic water pressure acting on them from the outside when the bottom depression is flooded with water, i.e. an artificial lake is formed therein which covers the pressure vessels.

The plurality of pressure vessels is/are preferably equipped with one or more turbines, pumps, and/or pump turbines so that, when the dry-lying bottom depression is flooded with water, the underwater pumped storage power plant can be operated in such a way that electrical energy is generated when water is let into the pressure vessels from the flooded bottom depression and electrical energy is stored when water is let out of the pressure vessels into the flooded bottom depression. In this regard, it may be provided that the pressure vessels are equipped with one or more turbines, pumps, and/or pump turbines after they are already arranged. On the other hand, the equipment with turbines, pumps and/or pump turbines can also already be carried out on a pressure vessel itself before this is/are arranged at its desired position.

With regard to equipping the pressure vessels with turbines, pumps and/or pump turbines, various options are available.

One possibility is that of the plurality of pressure vessels, individual pressure vessels are/will be set up as independent pressure vessels in that these pressure vessels are/will each be equipped with their own turbine, pump and/or pump turbine via their at least one flow opening. Even in the case of several flow openings, a pressure vessel can be/is set up as an independent pressure vessel, e.g. in that one flow opening is/are connected to a turbine and another flow opening is/are connected to a pump. The setup of a pressure vessel as a stand-alone pressure vessel is also referred to as a "self- 12 Date Recue/Date Received 2022-01-10 CA03146745 2022-01-10 sufficient case" in the context of the present disclosure. It may be provided, for example, that at least one of the pressure vessels, at least some of the pressure vessels, the majority of the pressure vessels, or even all of the pressure vessels are/will be set up as stand-alone pressure vessels.

According to another possibility, which can be considered additionally or alternatively, several of the plurality of pressure vessels can be set up as a pressure vessel group in that these pressure vessels are connected to each other via at least one pressure line or several pressure lines between respective flow openings and are equipped with a common turbine, pump and/or pump turbine. The several pressure vessels connected to form a group may, for example, be two or more adjacent pressure vessels, in particular arranged directly next to each other and/or one above the other. The arrangement of a plurality of pressure vessels as a group is also referred to in the context of the present disclosure as an "oligotarchic case" or a "central case", as will be discussed in more detail below. In particular, it may be advantageous to set up several pressure vessel groups, e.g., in that some adjacent pressure vessels are/will be connected to form a group in each case.

As already explained, use can be made of a plurality, in particular a large plurality, of pressure vessels. In principle, for example, at least 4 or at least 10 pressure vessels may be provided.

Preferably, especially after the lower reservoir has been converted and/or expanded, at least 100 pressure vessels may be comprised, preferably at least 1000 pressure vessels may be comprised, and more preferably at least 10000 pressure vessels may be comprised.

In particular, where there are a plurality of pressure vessels contributing to the total volume of the lower reservoir, the pressure vessels may have relatively small volumes.

Accordingly, it is envisaged that the or at least one pressure vessel has a volume of less than 600,000 cubic meters, preferably of less than 100,000 cubic meters, more preferably of less than 15,000 cubic meters. On the other hand, the pressure vessels should also not be too small. This is because it is advantageous, especially in the case of spherical pressure vessels, if bottlenecks of free spaces between the pressure vessels do not become too small. One reason is that turbines, pumps and/or pump turbines can then be better arranged, operated or maintained in the free spaces, in particular because the free spaces between the pressure vessels can serve for water flows or pump turbines remain easily accessible in case of inspection. Another reason is to ensure a favorable cost-benefit ratio of pump turbines. Accordingly, it is intended in particular to have a volume of at least 1000 13 Date Recue/Date Received 2022-01-10 CA03146745 2022-01-10 cubic meters, preferably of at least than 5000 cubic meters, particularly preferably of at least 10,000 cubic meters. Overall, it may accordingly be useful, for example, for one, some or all of the pressure vessels to have a volume of between 5000 and 600,000 cubic meters, preferably between 5000 and 100,000 cubic meters, and particularly preferably between 5000 and 15,000 cubic meters.

In order to be able to arrange the pressure vessels suitably next to each other and/or on top of each other, many different shapes can be considered. For example, tubular or toroidal pressure vessels can be provided. For static reasons, pressure vessels with a sphere-like shape are particularly suitable. Accordingly, it may be provided that the or at least some of the pressure vessels have a shape which fills a smallest possible (hypothetical) enveloping sphere by volume at least 25 percent, preferably at least 50 percent, more preferably at least 75 percent, and most preferably at least 90 percent. By the shape of the pressure vessels is meant here, in particular, the outer shape of the components of the pressure vessels that ensure the pressure resistance.

Specifically, the or at least some of the pressure vessels can be designed in particular as a pressure- resistant sphere, egg shape, ellipsoid or polyhedron.

Pressure vessels with sphere-like or spherical geometry are particularly advantageous because they are stabilized by the pressure from outside. Even if, for example, cracks should already be present, the pressure vessels often remain functional because such cracks are compressed by the pressure from the outside. This can lead to a very long service life of the pressure vessels, which can be e.g. over 100 or over 1000 years. Furthermore, the pressure vessels can be made e.g. by a concrete without iron reinforcement. By using a concrete e.g. for off-shore installation, which is without iron reinforcement, there is no rust formation, which also favors the aforementioned long service life.

Due to a lifetime of more than 100 or more than 1000 years, very long depreciation periods for the concrete spheres are possible and thus an investment in the future energy supply from which many generations will benefit. The invention is therefore characterized in particular by great sustainability.

As will be explained in more detail below, the wall thickness of the pressure vessels can be estimated using various factors. In a favorable case, however, the pressure vessels each have a wall thickness of between 5% and 15%, preferably between 7.5% and 12.5%, e.g. of 10% of the equivalent sphere diameter of the storage volume. This can also advantageously compensate for the buoyancy of the empty pressure vessel. 14 Date Recue/Date Received 2022-01-10 As already explained, the pressure vessels can be/are positioned next to each other and/or on top of each other in the dry bottom cavity, e.g. on a lower bottom of the open pit. In this case, the pressure vessels are/is preferably regularly arranged next to each other and/or one above the other.

Apreferred possibility is that the pressure vessels are/is arranged in the dry-lying soil recess in such a way that a lower pressure vessel layer with regular arrangement of pressure vessels lying directly on the substrate is/is formed, which is preferably suitable as a base for a second pressure vessel layer with regular arrangement lying above it, in such a way that the pressure vessels of the second pressure vessel layer can be arranged stably in recesses of the lower pressure vessel layer lying below. This means in particular that pressure vessels of a second layer cannot easily slip or slide sideways.

Alower layer of pressure vessels preferably comprises at least 100, more preferably at least 500, even more preferably at least 1000 pressure vessels in a regular arrangement.

This again shows the advantage of arranging the pressure vessels already in the dry state of the depression, because it would be much more difficult to create a regular arrangement of pressure vessels in the form of a lower layer by subsequent sinking in an already existing lake. This is also due to the fact that in the dry-lying condition the subsoil can be leveled more easily beforehand, as will be explained further below. In this context, however, reference is made to the special procedure of "lake-based spreading" described in more detail further below.

Preferably, in particular as long as the bottom recess is still dry, a second pressure vessel layer is/are arranged on the lower pressure vessel layer lying on the substrate and, particularly preferably, a third pressure vessel layer is arranged thereon and, if necessary, further pressure vessel layers are arranged thereon, the pressure vessel layers - as described above - in turn each preferably being suitable as a base with recesses for a respective pressure vessel layer lying above.

In most of the shapes chosen for the pressure vessels, in particular in the case of sphere-like or spherical pressure vessels, free spaces remain between the pressure vessels when they are arranged. Preferably, the many pressure vessels are/will be arranged in the dry-lying bottom cavity next to each other and/or on top of each other, in particular arranged as lower, second and third pressure vessel layers, in such a way that free spaces remain between the pressure vessels which Date Recue/Date Received 2022-01-10 CA03146745 2022-01-10 extend from the top, preferably in a straight line from the top, to the substrate, in particular through all layers, and preferably in such a way that the free spaces occur in a regularity defined by the arrangement of the pressure vessels. Such free spaces can advantageously form water-bearing accesses to the flow openings or turbines, pumps and/or pump turbines.

In this case in particular, but also independently of this, one or more free spaces remaining between pressure vessels can be designed as continuous shafts projecting upwards, if necessary.

As will be discussed and illustrated in more detail below by means of examples, the pressure vessels can be/are arranged in particular according to the structure of a densest, in particular hexagonally densest, sphere packing, preferably in that pressure vessels of the lower and optionally of the second pressure vessel layer are/is arranged according to the structure of a densest sphere packing and optionally the pressure vessels of the third pressure vessel layer are/are arranged according to the structure of a hexagonally densest sphere packing (and thus again congruent with the lower layer).

If the pressure vessels are/will be arranged in layers, e.g. in tightest spherical packing, but also independently thereof, a pressure vessel to be or to be set up as an independent pressure vessel may - with reference to the "self-sufficient" case - e.g. be arranged or processed in such a way that a flow-through opening for admitting and/or discharging water into the pressure vessel is arranged at the bottom or laterally at the bottom of the pressure vessel, preferably in such a way that the flow- through opening reaches the lowest point inside the pressure vessel.

Alternatively or additionally - with reference to the "oligo" or "central" case - it can be provided that several pressure vessels to be set up or set up as a pressure vessel group are/is arranged or processed in such a way that at least one flow-through opening of one or preferably of each pressure vessel of the pressure vessel group is arranged at the bottom or laterally at the bottom of the pressure vessel, in particular in such a way that the flow-through opening in the interior of the pressure vessel reaches the lowest point, and wherein preferably two pressure vessels arranged one above the other are/is connected to one another via pressure lines between a flow-through opening arranged at the bottom or laterally at the bottom of the pressure vessel arranged further up 16 Date Recue/Date Received 2022-01-10 CA03146745 2022-01-10 and a flow-through opening of the pressure vessel arranged further down.

In accordance with the consideration that free spaces between the pressure vessels can serve as water-carrying accesses, it can be expedient - with reference to the "self- sufficient" case - that an own turbine, pump and/or pump turbine of an independent pressure vessel is/are connected with a flow opening of the pressure vessel in such a way and/or is/are arranged in a free space formed between pressure vessels in such a way, that, when the dry bottom recess is flooded with water, water which is let into the pressure vessel is drawn preferably from above, particularly preferably in a straight line from above, via the free space and/or water which is let out of the pressure vessel is discharged preferably upwards, particularly preferably in a straight line upwards, via the free space.

Alternatively or additionally - with reference to the "oligo" or "central" case - it can also be provided that a common turbine, pump and/or pump turbine of a pressure vessel group is/are connected to a flow opening of a pressure vessel or to a pressure line connecting the pressure vessels in such a way and/or is/are arranged in a free space formed between pressure vessels in such a way that, when the dry bottom recess is flooded with water, water which is let into the pressure vessel group is drawn preferably from above, particularly preferably in a straight line from above, via the free space and/or water which is let out of the pressure vessel group is discharged preferably upwards, particularly preferably in a straight line upwards, via the free space, wherein the common turbine, pump and/or pump turbine is/are preferably arranged on the subsoil or recessed in the subsoil.

With regard to the arrangement of the pressure vessels, it can be favorable if at least some of the pressure vessels, in particular the pressure vessels of the lower pressure vessel layer, are/will be arranged in the dry bottom cavity, e.g. on a lower bottom of the open pit, in such a way that adjacent pressure vessels are each supported laterally against each other and/or marginal pressure vessels are preferably supported laterally against a wall or a part of the dry bottom cavity.

In order to provide lateral support for pressure vessels at the edges, walls and/or a channel bounded by walls can be provided or produced in the dry bottom cavity, in particular the open pit, so that pressure vessels, in particular those of the lower layer, can be supported laterally against them.

Here, again, advantage can be taken of the fact that the bottom cavity is dry, i.e. the construction of retaining walls can be carried out with normal construction machinery, or, in the case of an open pit, 17 Date Recue/Date Received 2022-01-10 CA03146745 2022-01-10 also with open pit mining machinery already present on site. Preferably, retaining walls and/or a trench are constructed in the ground cavity before the pressure vessels are placed therein.

Incidentally, the subsoil for the pressure vessels can also be leveled in the same course.

It is advantageous if the pressure vessels remain at the bottom of the bottom cavity without substantial weighting or anchoring, or even entirely without weighting or anchoring, when the bottom cavity is flooded with water. Therefore, at least some of the pressure vessels preferably have a mass that is greater than, or at least not substantially less than, the mass of water displaced by the pressure vessel when the dry bottom cavity is flooded with water.

Independently of this, it can be provided that at least some of the pressure vessels, in particular the pressure vessels of a lower pressure vessel layer, are/is fixed or anchored to the substrate and/or that at least some of the pressure vessels, in particular the pressure vessels of an upper pressure vessel layer, are/is weighted down with ballast, in particular with excavated material from the ground depression. On the one hand, these measures can serve to ensure that the pressure vessels remain on the ground when the ground cavity is flooded with water, but can also be provided if the pressure vessels would already remain on the ground due to their mass, e.g. to stabilize the pressure vessels against slipping.

As has already been mentioned, free spaces usually remain between the pressure vessels arranged side by side and/or one above the other, especially if the pressure vessels are sphere-like or spherical in shape. While such free spaces - as described above - can serve as a connection between the later artificial lake and the turbines, pumps and/or pump turbines, not all free spaces are necessarily necessary or suitable for this purpose.

Accordingly, it can be provided that remaining free spaces between pressure vessels, which do not serve as access to turbines, pumps and/or pump turbines, are filled or poured with excavated material or building material (e.g. sand, stones, rubble and/or cement). This can be done, for example, with a view to stabilization or also to influence the flow behavior of the water.

Aweighting of the pressure vessels and/or a filling of free spaces between the pressure vessels should preferably be designed or carried out in such a way that the weighting material or filling 18 Date Recue/Date Received 2022-01-10 CA03146745 2022-01-10 material remains stationary and is not washed away by flowing water, contaminates the water or damages turbines, pumps / pump turbines. For this purpose, the material can be/is fixed with cement, for example.

In a particular embodiment of the invention, the plurality of pressure vessels can also be/be set up as a pressure vessel assembly in that these pressure vessels communicate with each other via respective flow openings and are/is closed off to the outside with a common casing, the common casing having at least one flow opening to the outside in order to be able to equip the pressure vessel assembly with a common turbine, pump and/or pump turbine.

It may be worthwhile to first further widen and/or deepen the bottom pit, especially if it already exists as an open pit, preferably with open pit mining equipment already on site.

This can be done in particular after the lower reservoir is connected to the preliminary upper reservoir. In particular, the bottom pit can be further deepened and/or widened in such a way that a depth (Te Tiefe) of more than 100 meters, preferably more than 300 meters, even more preferably more than 400 meters, even more preferably more than 500 meters, especially preferably more than 700 meters and possibly even more than 1000 meters is reached.

Even if the ground depression does not already exist as a natural depression or as an open pit, it may be worthwhile to initially construct it on the "green meadow" or on the "yellow desert sand".

Accordingly, it may be envisaged that the dry-lying ground depression is first created for the construction of the underwater pumped storage power plant, in particular in such a way that a depth (depth) of more than 100 meters, in particular more than 200 meters, preferably more than 300 meters, even more preferably more than 400 meters, even more preferably more than 500 meters, .. especially preferably more than 700 meters and possibly even more than 1000 meters is reached.

In a preferred process variant, a cavity, e.g. a shaft or a tunnel, for the installation of technical equipment such as cables, pressure lines, turbines, pumps and/or pump turbines can be provided or created in the dry-lying soil cavity under a floor planned as a subsoil for the arrangement of the pressure vessels. This will be further described and illustrated below. 19 Date Recue/Date Received 2022-01-10 Alternatively or additionally, however, it can also be provided that an accessible and/or drivable cavity, e.g. a shaft or a tunnel, in particular for the supply and/or maintenance of technical equipment, is/are provided or created in the dry soil recess under a soil planned as a subsoil for the arrangement of the pressure vessels, if necessary again under a cavity - as described above - for the installation of technical equipment. Such an accessible and/or drivable cavity can preferably be/be connected to an external access, which is provided or created in particular in a slope or on a slope of the ground cavity.

In particular, the at least partially constructed lower reservoir created within the scope of the present invention can be operated without connections to the outside air. Accordingly, in particular, it is not necessary to construct corresponding connections, e.g., towers up to the surface of the artificial lake planned later in the depression. This has the advantage, in particular, that greater depths (depths) of the bottom deepening can be considered. Air in the cavities also has the disadvantage of reducing the efficiency of energy storage, since it does not condense when the pressure in the cavities is increased, but builds up a counterpressure and heats up in the process. This thermal energy can be a major loss factor in the type of energy storage proposed here.

The at least partially constructed lower reservoir or the or at least some of the pressure vessels is/are thus preferably designed, arranged, equipped with one or more turbines, pumps and/or pump turbines and/or connected to each other via pressure lines between respective flow openings in such a way that when water is discharged from the pressure vessel, no air flows into the pressure vessel, but rather a vacuum is preferably created in the pressure vessel, limited only by the partial pressure of the water vapor.

Furthermore, it can be provided that when water is let into the pressure vessel, the pressure vessel is not completely filled with water, but preferably a certain residual volume remains with a vacuum limited in particular only by the partial pressure of the water vapor. Such a residual volume can be very small, for example a residual volume of less than 100 cubic meters, preferably of less than 10 cubic meters or even a residual volume of less than 1 cubic meter can be provided.

If the pressure vessels are/will be arranged in multiple layers, a "sea-based deployment" of the pressure vessels may possibly be suitable. In particular, it may be envisaged that the plurality of Date Recue/Date Received 2022-01-10 CA03146745 2022-01-10 pressure vessels are/will be arranged in the dry bottom cavity, e.g. on a lower bottom of the open pit in such a way that first a lower pressure vessel layer of pressure vessels lying directly on the subsoil is formed in the dry-lying bottom recess and then the bottom recess is filled with water to such an extent that pressure vessels for a second pressure vessel layer can be conveyed in a floating manner to respectively provided positions above the lower pressure vessel layer, and the second pressure vessel layer is formed by conveying the pressure vessels for this layer in a floating manner to the respectively provided positions, e.g. by making them buoyant.e.g. by making them buoyant, and lowering them onto the lower pressure vessel layer, e.g. by making them submersible or submersible again.

In an analogous manner, the bottom recess can then of course be filled with water step by step to such an extent that pressure vessels for a third pressure vessel layer and, if necessary, further pressure vessel layers can each be floated to designated positions and lowered.

Such a "sea-supported deployment" of pressure vessels represents a special method to be able to place very heavy pressure vessels in particular in a targeted and simple manner with specially selected water filling of the bottom backfill.

According to another continuation of the invention, it may be provided to subsequently expand a lower reservoir of pressure vessels that is already under water. For this purpose - after the plurality of pressure vessels has/have been arranged in the bottom cavity and the bottom cavity has been at least partially flooded with water in such a way that an artificial lake serving as an upper reservoir is formed - one or more further pressure vessels can be lowered from the surface of the lake onto the already arranged pressure vessels.

Preferably, the already arranged pressure vessels are thereby arranged as one or more pressure vessel layers so that the further lowered pressure vessels can be stably arranged in recesses of one of the pressure vessel layers. The further lowered pressure vessels are set up in particular as independent pressure vessels with their own turbine, pump and/or pump turbine. 21 Date Recue/Date Received 2022-01-10 BRIEF DESCRIPTION OF THE FIGURES

It is show in:

Fig. 1 a schematic diagram of a storage lake which, during energy storage, transports water with the volume Vob = Ff0I1* Vu from the middle depth hu the lower basin built as a structure on the bottom of the lake to the middle depth h of the upper basin, Fig. 2 the reservoir from Fig. 1 with installation section / underground connection level, e.g. with channel for power line, water connection pipes or access / access section, Fig. 3 a schematic representation of an open pit channel with embedded cavity spherical reservoirs in a regular arrangement, Fig. 4 a schematic top view of an open pit mine, e.g. the Hambach Gully, with embedded cavity spheres in hexagonal tight packing. The spheres are shown only two- dimensionally by their horizontal cross-sectional great circles. One can see the second uppermost layer covering the entire surface and a partial area of the uppermost layer on the left side. For reasons of symmetry, the hexagonally densest sphere packing shown results in continuous vertical free spaces 24 and 22 from bottom to top, one half of which (namely 24) can be used as access or connecting shafts with a clear bottleneck shaft 4, as shown.

In the hexagonally tightest sphere packing, the spheres of every third level again lie exactly above the spheres of a first level, Fig. 5a a cross-section in plane A-A# from the plan view in Fig. 4 in schematic, coarsened view, where the small circles are not to scale and indicate only the location where the lateral ball ends lying directly in front of and behind the cross-sectional plane touch. A channel is shown with embedded cavity reservoirs 3 arranged in hexagonal tightest sphere packing and clear access shafts 4 to the pump turbines, Fig. 5b a cross-section in plane B-B# of the top view in Fig. 4 again in schematic, representation as in Fig. 5a, whereby the backfill space 22 can be filled with stones, gravel and sand, Fig. 6 an enlarged section of Fig. 4, showing a top view of a small section of the top layer and a slightly larger section of the second top layer, Fig. 7 a schematic cross-section of an open pit, e.g. the Hambach trench, with pump turbines 7 installed directly in the cavity spheres, whereby sufficient access to the seawater is ensured by the free space 24 between the spheres 3, 22 Date Recue/Date Received 2022-01-10 Fig. 8a a schematic cross-section of an open pit, e.g., the Hambach channel, with connecting pipes 6 from the storage spheres 3 to bunkers installed on the lake bottom 1, containing a common pump turbine 77 for a group of storage spheres, Fig. 8b a schematic cross-section of an open pit mine, e.g. the Hambach trench, with short connecting pipes 61 from storage spheres to storage spheres and bunkers installed on the lake bottom, which contains the common pump turbine 77 for a larger group of storage spheres, whereby the 2*8=16 spheres, which are located just behind and just in front of the cross-sectional plane shown and are only indicated in the figure, can also be connected to the distribution pipework 6, which can also extend perpendicularly to the cross-sectional area shown on or in the bottom 1, Fig. 9a schematic cross-section of an open pit, e.g., the Hambach channel, with connecting pipes 6 from storage spheres to bunkers installed on the lake bottom, containing the common pump turbine 77 for a larger group of storage spheres, Fig. 9b schematic cross-section of an open pit, e.g., the Hambach flume, with short connecting pipes 61 from storage sphere to storage sphere and bunker installed on the lake bottom containing the common pump turbine 77 for a larger group of storage spheres, Fig. 10 a schematic cross-section of an open pit mine, with the storage facility having at least one connecting pipe 44 between free lake 0 and PT station 77 and otherwise being completely embedded, Le., the space shown in the previous figures as free access space 24 is now also backfilled, so that access to the lake is through pipe 44, which is open at the top.

Maintenance and eventual replacement of the pump turbine can be accomplished - as in a mine- through a line 67 laid in the bottom of the lake, which may be connected to a central supply and manhole 5 (see Fig. 11), Fig. 11 a schematic cross-section of an open pit mine with a drivable roadway 67 running in the lake bottom 1 and connected to a supply and personnel shaft 5, whereby this can also run as a drivable and watertight tunnelled mountain road on the slope of the lake and can already be constructed in the dry before the lake is flooded, Fig. 12 a schematic cross-section of an open pit mine with an operating storage system from Fig. 10 and subsequently installed self-sufficient storage spheres ("in situ" installation), Fig. 13 a schematic representation of an open pit mine in interim operation with only partially constructed lower lake-egg basin 83 with oligo pump turbines and pipe connection 86 to 23 Date Recue/Date Received 2022-01-10 CA03146745 2022-01-10 the interim upper basin 80 at the later lake promenade, the interim upper basin being sealed off from the later working lake by a dam 84.

Fig. 14 a schematic representation of an open pit mine with underwater pumped storage power plant according to a further embodiment, Fig. 15 a schematic cross-section of the lower reservoir of Fig. 14, Fig. 16 a schematic longitudinal section of the lower reservoir of Fig. 14, Fig. 17 a schematic top view of the lower reservoir of Fig. 14, Fig. 18 a schematic representation of an open pit with underwater pumped storage power plant according to a further embodiment with fill material, Fig. 19 a map of the Hambach open pit mine in the dry state, Fig. 20 a map of the Hambach open pit mine with dam in interim operation, Fig. 21 a map of the Hambach open pit mine with dam after flooding, Fig.22 another map of the Hambach open pit mine with dam after flooding.

DETAILED DESCRIPTION OF THE INVENTION

Expansion of an existing open pit mine as a PSKW

The following section deals with the expansion of an existing open pit mine as a PSKW and the special conditions of a large open pit mine that is being phased out. However, the remarks apply generally to any existing or to-be-constructed dry-land ground depression. As will be discussed in more detail below, if the geology is suitable, a PSKW facility can be constructed on a "greenfield" (or "yellow desert") site without the preliminary work of an expiring open pit mine.

Thus, the following deals with the approach of optimally and extensively developing an existing open pit mine for energy storage as an "unconventional PSKW ", using the lake provided by reclamation as the upper basin and a suitable cavity structure to be created at the bottom 1 of the lake as the lower basin. This is shown schematically in the Fig. 1. The lower basin 200 has the gross volume V u, but only the part of this volume characterized fuliby the filling factor F can be used as a usable net volume during energy storage. This net volume lifts the water level of the upper basin 300, i.e. the free lake water 0 (without buildings), during pumping out, so that, on balance, the lift volume V obis filled with water there. Depending on the requirements, power cables, - but also water connection 24 Date Recue/Date Received 2022-01-10 CA03146745 2022-01-10 pipes or an access or even a convenient driveway - can be laid below the lake bottom 1 in a connection level 66, as shown in Fig. 2. The lower reservoir 200 is constructed on the subsoil 110 of the bottom cavity 100. Below this, there may be a cavity 66 which may serve as an installation route, underground connection level, e.g. with channel for power line, water connection pipes or even access/access route.

Depending on the embodiment, the present invention may realize one or more of the following features: = the entire volume available as "sub-basin" can be used for energy storage as far as possible. = The facility consists of independent elements, each of which remains accessible from the outside. = Safety: In the event of an accident, the effects are limited to a part of the overall plant with a manageable risk potential and, in particular, a "chain reaction" of further accidents is ruled out. = Installation of the storage system remains possible - at least after installation of a technical cabling level 66 on or in the ground and a first layer of the storage level - in principle even after the lake has been filled. = Compensation of the possible remaining buoyancy of the elements emptied of water (i.e. energetically charged) takes place in the immediate vicinity of each element, and the symmetry of the forces acting on the storage element also prevents the occurrence of torques as far as possible. = The inflows and outflows of the lake water to the pump turbines are distributed over a large area over the surface of the plant, so that only very low flow velocities result in the water body of the lake. At constrictions within the storage facility, the unavoidably somewhat higher water velocities can be adjusted in terms of flow by continuously narrowing (or widening) transition sections. = The pump turbines are installed in the lower part of a cavity or, in the case of cavity bodies resting directly on the bottom, possibly also in caverns in the lake bottom in order to manage without upstream pressure during pumping. = The construction and partial operation of the PSKW plant can take place in parallel with the phasing out of coal mining.

Date Recue/Date Received 2022-01-10 Depending on the embodiment, the invention is based on one or more of the concepts listed below for using a large abandoned open pit mine recultivated into a lake as a pumped storage power plant.

Still other embodiments are given below. (1.) Memory Basic cell: Hollow sphere memory (SeaEgg) Preferably, a hollow sphere storage tank (here now called "SeeEi") is used as the basic storage cell, which is generally referred to as a pressure vessel. In principle, the shell thickness must be only as thick as required due to the water pressure, since buoyancy safety can also be achieved by embedding (see (8.)); on the other hand, it may be more practical and simpler in some cases to stick to an intrinsically buoyancy-compensated "unit sphere" even at small depths.

Furthermore, the following should be noted: = Large-volume "pipe bundles" can also be used as water storage shafts in horizontal or vertical arrangements. However, the initially still free and above-ground access in the abandoned open pit allows the use of large series-produced spheres, which provides advantages in the filling factor and a smaller (approx. half as thick) wall thickness. = More precise structural considerations will probably reveal improvements due to small deviations from the spherical shape to more "egg-shaped" hollow bodies.

However, we continue to use the term "hollow sphere" as an idealized designation also for such structures and base the capacitance calculations on a sphere. = Suitable polyhedra are also conceivable, provided they offer manufacturing advantages. (2.) Pump turbine (PT) Three cases in particular can be distinguished when equipping the storage facility with pumps and turbines: 1. Case: Self-sufficient, PT to each storage base cell, no other pipe connections. 2. Case: Oligotark: A few neighboring basic cells are connected by short connecting pipes; a new unit cell is created from the connected elementary basic cells by a symmetrical arrangement. Only one pump-turbine unit is used for this unit cell. Note: "Oligotark" refers to the independence of the composite unit cell, which consists of several basic cells. 26 Date Recue/Date Received 2022-01-10 CA03146745 2022-01-10 3. Case: Central: Several basic cells or unit cells are combined and connected to a powerful central pump-turbine unit.

The selection is based, for example, on the cost structure of the pump turbines depending on their capacity and on considerations of inflow, safety, and environmental impact.

The water - as shown in point (5.) - can reach the pump turbines from the lake quickly and with low resistance due to the geometrical arrangement of the base cells (storage spheres). (3.) Trough, for holding the storage units Achannel is constructed on the bottom of the open pit to accommodate the primarily spherical storage bed cells in an orderly and symmetrical arrangement. The channel can extend over the entire available lake bottom. If necessary, it can also be "parceled out" in sections, e.g., by an earthen embankment.

Fig. 3 shows the easily understandable principle according to which the pressure vessels 3 ("SeeEi"; elementary storage basic cell, primarily a hollow sphere storage) are regularly arranged in the bottom recess 100 defined by the bottom 1 on its base 110 and, if necessary, can be supported laterally by walls 120. The can be imagined, for example, as if spheres were arranged in a large box with sloping walls. Between the spheres there usually remains an intermediate space/clearance 2, which at least in partial areas can be filled with embedding material (excavated sand, gravel, smaller rock fragments, possibly also lightweight concrete for stabilization), e.g. to serve for buoyancy prevention so that a sufficient average density results, and in other partial areas (particularly pronounced in the case of a hexagonal sphere arrangement) is kept clear as a connecting space from the lake to the lower spheres or to installations on the ground, as will be explained in more detail below.

The cross-sectional plane shown in Fig. 3 may not yet have optimal symmetry of the sphere packing: each upper sphere sits on only two lower spheres. It is more convenient to use the optimal hexagonally tightest sphere packing of the memory base cells, as we will illustrate in the following figures. The difference consists in a more effective offset of the horizontal sphere planes, where 27 Date Recue/Date Received 2022-01-10 CA03146745 2022-01-10 then each upper sphere sits in the trough between 3 lower spheres, and will be considered in the following figures (Fig. 4 and following figures). (4.) Installation sections 66 Channels may be constructed below the channel receiving the storage elements to receive the power cables, which are then routed up the side of the subbasin or in a shaft.

In some embodiments (see below), these installation sections are developed as an access to oligotrophic pump-turbine units installed on the ground. In dry construction, an access pipe may be constructed along the slope of the upper and lower basins to provide convenient access for personnel and material handling to the technical equipment on or in the bottom of the lower basin. As in underground mining, the production facilities are then easily accessible, but the tedious underground roadway driving there can be done in advance in the convenient dry open pit. (5.) Geometric arrangement of sea eggs: hexagonal densest sphere packing The sea eggs are preferably arranged in hexagonally tightest ball packing. The spheres of the following level are fixed in half of the troughs of the level below. Two successive horizontal planes are offset by a fraction of the sphere diameter determined by symmetry, so that identical packages of two of the offset successive planes are formed. Thus, in every third plane, the spheres again lie exactly above the spheres of the first plane. This distinguishes the hexagonally densest sphere packing from the equally dense "cubically densest" sphere packing, in which only every fourth plane lies exactly above the first plane again.

An advantage of the hexagonal densest sphere packing is that continuous vertical free spaces result here. For a particularly vivid and detailed description of these symmetry forms, please refer to the homepage "Understanding Chemistry" by M. Schmidt /Schmidt 2019/, otherwise, of course, one can also refer to the textbooks of crystallography. For the spatial imagination it might be helpful to "see" in the following figures not only the single spheres but also the tetrahedra of 4 spheres, namely those where 3 spheres abut in a (vertical or horizontal) plane and the 4th sphere is in the hollow of the first three. 28 Date Recue/Date Received 2022-01-10 Fig. 4 shows a top view of the bottom recess 100 or trough with embedded pressure vessels 3 designed as cavity spherical accumulators in hexagonal tightest packing, leaving free spaces 2 between the pressure vessels 3. Each sphere is shown here only two- dimensionally by its horizontal cross-sectional great circle. You can see the second uppermost layer covering the entire surface and a partial area of the uppermost layer on the left side.

Free spaces result between the spheres. These free spaces 2 can be divided into two classes according to the criterion of "perpendicular access" to the lake above. They are: = Either an "access space" (22 and 24), which has a free vertical access to the free sea above, and which, depending on its function, can still be distinguished as a o "backfilled" access space 22 when filled, for example, with sand, gravel, or stones, or as a o open or open water access space 24, if it remains open = Or a "blind shaft space" 27 - as we want to call a contiguous "trapped" space between the spheres, when no vertical access to the lake is possible from it.

Thus, for reasons of symmetry, the hexagonally tightest sphere packing shown results in continuous vertical access spaces 22 and 24 from bottom to top, the constrictions of which remain visible in the plan view. Some of these free spaces can remain open and ensure access of seawater to the pump turbines (free-water access space 24) and thus also be used as access or connecting shafts in the event of maintenance, and some of them can be backfilled with stones, gravel and sand as "backfilled access spaces" 22 as buoyancy barriers. In Fig. 4, the vertical volume element given by the geometry of the superimposed constrictions is marked as "clear bottleneck shaft" 4 in the open water access spaces 24; this is thus an imaginary subspace of the open water access space 24.

This "clear geometric bottleneck shaft" 4, results in this example from the hexagonal geometry of the sphere arrangement and is located in the part 24 of the open spaces 2 that is not backfilled.

Preferably, each sphere has direct access to three access spaces (22 or 24) adjacent to it, and three adjacent spheres in each level can be directly accessed from an access space. Therefore, access from the spheres to the access spaces can be selected so that a portion of the access spaces is not used as access to the lake at all and therefore can be backfilled, for example. In Fig. 29 Date Recue/Date Received 2022-01-10 CA03146745 2022-01-10 4, exactly half of the access spaces were selected as open water access space 24, which is also suggested for symmetry reasons.

It can also be seen from Fig. 4 that each sphere is surrounded by three blind shafts 27. It is obvious to fill these blind shafts with sand, gravel or stones in the course of installation of the system, i.e. as long as they are not yet covered by the sphere level above and therefore still accessible from above.

The small remaining lateral holes to open water access rooms 24 can be closed with binding material (e.g. lightweight concrete) or also with construction textiles or simply beveled during filling.

It is possible to provide a hollow sphere with a balancing (bead) so that it fits well on the spheres below it, in particular on the three spheres below it ("three" - because of the hexagonal symmetry, see Fig. 4) on which it is placed. If necessary, the direct contact surfaces can also be provided with bonding materials or a mortar to compensate for small-area pressure points (otherwise see also below on "Embedding"). In addition, balancing can be applied in such a way that the lateral access to the cavities intended for backfilling later is covered.

Now we consider a cross-section to the plan view of Fig. 4 (e.g., of the Hambach flume) in a plane A--A# where the open water access spaces 24 to the pump turbines are located (Fig 5a). The section passes through the vertical great circle of one third of the spheres and touches the lateral tips of the other 2/3 of the sphere, which lie both behind and in front of the drawing plane, but which we have indicated only by a single bold dot for clarity.

Open spaces 4, open at the top, are shown between the pressure vessels 3, which are designed as cavity storage tanks, and can serve as access to the pump turbines. In general, an open water .. access space 24 can be provided between the pressure vessels 3, a free space between the spheres in which sufficient access to the seawater can be ensured.

It can be seen that there is plenty of space in the shaft level and the associated space between the spheres for access to their lower side inlets/outlets. In principle, this space can be kept open for the sea water; then we call it "open water access space" 24. However, it can also be partially filled as well, e.g. with stone materials, especially provided that a sufficiently large space for free access of Date Recue/Date Received 2022-01-10 CA03146745 2022-01-10 the water to the openings of each sphere remains guaranteed. Here one should also think of maintenance work up to a replacement of the pump turbine, which is certainly due at some point.

In principle, a cross-sectional plane shifted by one sphere radius (see section line B-B# in Fig. 4) looks the same (see Fig. 5b), except that here, if necessary, no access to the spheres is provided and therefore the entire space, which we now refer to as backfill space 22, could be filled with sand, gravel and stones.

One aspect of the entire storage facility, therefore, consists in particular in the fact that it results, as if from building blocks, from the symmetrically ordered arrangement of stable and statically optimal elementary hollow bodies (especially hollow spheres). Just as one can assemble a simple wall from clinker bricks set in a bond, so we build a storage facility from hollow spheres in the hexagonal densest sphere packing, whereby the storage space is then located in the extraordinarily stable interior of the hollow spheres and the symmetry of the arrangement provides for access spaces open to the lake and, if necessary, also for suitable embedding spaces for ballast material.

Further below, some more advanced embodiments and details on the construction and design of a storage system will be discussed, as well as more advanced and alternative considerations. Before that, however, the enormous economic and energetic potential will be discussed.

Energetic potential of an open pit mine converted to a PSKW

In particular, the invention provides for the optimal and extensive development of an existing open pit mine for energy storage as an "unconventional PSKW ", using the lake provided by the reclamation as the upper basin and a suitable cavity structure to be created at the bottom of the lake as the lower basin (cf. Fig. 1).

The volume V of spthe cavity structure available for the storage process is obtained from the geometrically stressed volume Vuby multiplying it by a filling factor Ffuli:

Vsp= Ffuli - Vu (1) 31 Date Recue/Date Received 2022-01-10 The fill factor can be calculated from the wall thickness required for the stability of the containers and from the gaps between the containers. For the arrangement of hollow spheres in hexagonally tightest packing (see below), which is primarily considered for us, a filling factor in the order of 0.45 results, depending on the wall thickness.

The storage water is in the upper basin after injection, so it applies:

Vob= Vs p (2) The potential energy of the water body is thus reduced by AE= g = pw = VSp ' (hu - hob) (3) where we use the acceleration due to gravity g= 9.81 [m/s2] and the water density pw = 1000 [kg/m3 ]. Strictly speaking, h uand hob denote the heights of the centers of gravity of the storage water in the lower basin and the volume Vob in the upper basin, respectively. In order not to dwell on trivialities, in the following we calculate with effective values for the geometrical dimensions of the reservoir, which result from the fact that we work with a rectangular cross-section in the actual working area (i.e. in the lower basin and in the lifting area of the water level).

Then, as a stroke of the water level simply results in:

Stroke = 2 = hob (4) Be now Aob = the area of the actual lake, and Au = the area of the channel supporting the storage body, and H= the height of the storage body, which we assume to be uniform throughout the range.

Then, from a simple geometric consideration and using Eq(1), we get:

Vet, = Aob = stroke (5) 32 Date Recue/Date Received 2022-01-10 Vs= Ff011 Au = H (6) Using Eq(2), we then obtain for the maximum stroke of the lake between storage and retrieval:

Stroke = H = Ffoli = A I Aob (7) And for the recoverable storage energy, Eq(3) calculates to for a turbine efficiency q T= 0.90:

AE= (g = pw = qT) = Ffoli = Au = H = [ - hob] (8) Eq(7) and Eq(8) describe the "landscape" effort and the energy-economic potential of the storage operation. For estimations, it is sufficient to use a computational value of F fon= 0.45 for the fill factor.

In the following, however, we will still fooderive a determining equation for F.

The fill factor The fill factor Ffoli , i.e. the proportion of the usable storage volume in the total hole to be excavated for this purpose, is the product of two factors.

Ffoli = x_V = x_Pack (9) The first factor, the wall thickness volume factor x_V, describes the ratio of the inner volume of the hollow sphere, i.e. the storage volume V_Sp available for storage, to the total volume of the hollow sphere V_a . The second factor, the packing factor x_Pack, takes into account that hollow spheres cannot be packed together arbitrarily tightly.

The cavity available for storage purposes, we call it the "usable hole" or the storage volume, must be embedded in a stable structural envelope and secured against floating. For a spherical structure with usable inner diameter D_i and wall thickness acalculate a usable storage volume of V_Sp = Tr/6 - D_i3 (10) 33 Date Recue/Date Received 2022-01-10 CA03146745 2022-01-10 and an external "gross" volume of V_a = Tr/6 = (D_i + 2 = di)3 (11) from which the wall thickness volume factor x_V results: x_V = V_Sp / V_a = (1+ 2 = di/ D_i)-3 (12) If we convert Eq(12) to the outside diameter, D_a = D_i + 2 = di, we obtain x_V = (1+ 2 = di/ D_i) -3= [ D_i / (D_i + 2 = di) ] 3= [ (D_a = 2 -di) /D_a] 3, thus: x_V = [ 1 - 2 = di/ D_a ] 3 (12a) For the wall thickness di of the sphere, a minimum value results from the calculation of the strength and stability against the hydrostatic pressure prevailing at the depth. For a sphere of 30 m inner diameter and a hydrostatic pressure at 700 m sea depth, a value di = 3 [m] was determined in the StEnSea project (see above). Then, according to Eq(12a), the following results for the wall thickness volume factor for this environment x_V= 0.579 for project StEnSea (12b) In addition, we have to take into account that spheres cannot be nested next to and on top of each other without empty spaces. We call the ratio of the space occupied by the spheres to the total space of an enclosing cuboid the packing factor x_Pack. For an infinite crystal in hexagonal tightest sphere packing, the geometry gives the value (see e.g.: !Schmidt 2019/) x_Pack = 0.74 (13) The product of Eq(12b) and the constant value Eq(13) then yields, according to Eq(9), the filling factor already defined in Eq(1) Ffuli = x_V = x_Pack (9) 34 Date Recue/Date Received 2022-01-10 For the StEnSea sphere, this gives the numerical value of the fill factor to:

Ffuli = 0.43. for the StEnSea sphere (14) At lower depths, smaller wall thicknesses are sufficient. For this reason - and because of the uncertainties - we often use a rounded-up value for the filling factor:

Ffuli = 0.45 (calculated value for more general considerations) (15) .. However, the joy of higher filling factors with thinner walls is sometimes clouded by the necessity to compensate for a resulting buoyancy of the empty hollow sphere by additional ballast. The next section shows that the StEnSea sphere in fresh water can just manage without additional ballast.

Buoyancy and ballast We obtain an interesting characteristic value if we require that the buoyancy of the empty hollow sphere should not be greater than its weight. This requirement is optional, because a resulting buoyancy could also be compensated by anchoring or ballast. The buoyancy of the empty sphere is:

V_a - g - Rho_W and its weight: (V_a -V_Sp) - g - Rho_Concrete, where Rho_W = 1000 [kg/m 3] and Rho_Concrete = 2400 [kg/m 3] are the densities of water and concrete. If both forces are set equal, using Eq(12), the following is obtained Rho_W / Rho_Concrete = 1/ 2.4 = (1-V_Sp/V_a) = 1- x_V and finally for the wall thickness volume factor of the equilibrium between buoyancy and gravity, which we denote by the index "0" as x_Vo x_Vo = 1 - Rho_W / Rho_Concrete = (2400 -1000) / 2400 =1 A I 2.4 x_V o= 0.5833 (16) As long as the wall thickness volume factor x_V of a hollow concrete sphere calculated according to Eq(12) remains smaller than x_Vo, the empty sphere will remain at the bottom of the lake by its own Date Recue/Date Received 2022-01-10 CA03146745 2022-01-10 weight. A comparison with Eq(14) shows that this is just the case for the StEnSea sphere in freshwater.

Now we would like to apply these relationships to the Hambach open pit mine in its current planning on the one hand and in a desirable further expansion variant with the aim of using storage facilities on the other.

Here, we consider the subbasin as a structure resulting from multilayered layers of elementary hexagonal close-packed hollow spheres, and the spaces resulting from the symmetry are used as: (t) Hydraulic access to the upper lake (and if necessary as inspection shaft). (2.) or as backfill space to reduce buoyancy.

The lowest layers and the slope stabilization are conveniently made in drywall.

Energetic potential using the example of the Hambach Gully: planned recultivation lake Currently, according to the entry in Wikipedia /Wikipedia #Hambacher Tagebau/, a residual lake of 4200 [ha] = 42 [km2] surface and up to 400 m depth is planned for the Hambach open pit mine. This area can be reduced a little bit because of the slope in the area of the lift of the upper basin (see V obin Fig. 1), so that we can calculate with vertical boundaries. So we take as calculation value:

Aeb = 40 km2 = 40 = 106 [m2] (21) An own rough measurement of the Google-Map of the Hambach open pit mine results in a deepest bottom, which we want to call "Hambach gully", of Au = 4 - 1 km2. This channel may have a depth of 400 m at any point. For the storage structure we assume a height H of 130 m, which corresponds to about 4 layers with densely packed spheres of 30 m inner diameter. Then, with vertical walls, the average depth h of the lower basin is (400 - H/2) = 335 [m]. We summarize:

Au = 4 = 106[m2] (22) H= 130 [m] (23) h u= 335 [m]. (24) 36 Date Recue/Date Received 2022-01-10 According to Eq(7), with a fill factor of Ffoii= 0.45, the lift in the upper basin is given by Stroke = 130 0.45 1/10 = 5.8 [m] (25) and thus an average depth hob of the upper basin of h ob= 2.9 [m] (26) From these data and the constants defined above, the storage energy (which can be stored out) is calculated according to Eq(8) as follows AE= 191 [GWh] (27) Given the future German annual consumption of Q_a= 1000 [TWh/a] we assumed above for the completed energy transition, which corresponds to an average daily consumption of Q_d= 2.74 [TWh/a], the storage capacity according to Eq(27) would correspond to only 7% of the daily consumption; this is already almost 5 times the current total capacity of German PSPs, but with a somewhat more generous expansion of the daily construction site with regard to a future use as the backbone of the energy transition, capacities higher by more than one order of magnitude can be achieved. This is shown by the example in the next section.

Energetic potential: Deeply dredged and widened channel in the lake In the next section, we will show that it can be worthwhile to use the existing lignite mining infrastructure to further develop the open pit mine for the purposes of the PSKW.

The approved operating area for the Hambach open pit mine is 85 km 2. The residual lake, which was previously 2p1anned at 42 km, could therefore easily be doubled in size.

The geology of the Lower Rhine Bight is characterized by a sediment package up to 1300 m thick (/Wikipedia #Tagebau Hambach/). The reservoir could therefore be dredged much deeper. We currently do not 37 Date Recue/Date Received 2022-01-10 CA03146745 2022-01-10 have exact planning documents for the Hambach open pit mine. Therefore, we limit ourselves to estimates and cautious and rough assumptions.

For our second example calculation, we make the following choice: = We set a much greater depth of the channel of 1000 m - instead of the current depth of 400 m. In addition, we are massively increasing the base area of the channel from the previously planned 4 km2to 20 km 2, which is about half the area that was planned for the planned residual lake. = The new lake is divided into two parts. Only an effective area the size of the previously planned residual lake, i.e. 40 km2, serves as the actual upper basin for the PSKW. This basin, which is now to be used only for operational purposes, is hydraulically separated from the entire lake by a dam and therefore allows a large stroke of its water surface. The area beyond this dam, i.e. the part of the overall lake not used for the operation of the PSKW, represents the lake for recreational use promised as a recultivation measure and will be created in the area of the approved operational area. (see below for the procedure for the phased construction of the large-scale PSKW). = The sub-basin consists of 8 layers of standard hollow spheres with 30 m inner diameter. For this we adopt the data from the StEnSea project (see above). Because of the greater depth, the wall thickness is slightly thicker than in the previous chapter and is 3 [m]. This affects the fill factor Ffuli, which we now set somewhat lower. But we do not have to worry about the resulting buoyancy of the empty sphere. As total height H of the basin we calculate 280 m.

This results in the following parameters of the PSKW:

Aeb = 40 km2= 40 = 10 6[m 2] (28) Au = 20 106[m2] (29) H= 280 [m] (30) h= 860 [m]. (31) 38 Date Recue/Date Received 2022-01-10 According to Eq(7), with a fill factor of now F full= 0.43, the lift in the upper basin results in considerable but still expandable and, because of the bordering by the reclamation lake, by no means repulsive:

Stroke = 60 [m] (32) According to Eq.(8), the storage energy (which can be stored out) results in AE= 4.927 [TWh] (33) For classification: At the beginning, we assumed a future average daily consumption in Germany of Q_d= 2.74 [TWh/a] and a short-term storage demand of 20 to 30% of this daily demand. A comparison shows that it would be possible to build a power plant with an order of magnitude larger capacity in the Hambach Lake. Theoretically, one could supply the whole of Europe. The popular excuse of the opponents of the energy transition, that Germany does not have sufficient geographical resources for short-term storage for the energy transition, is therefore inapplicable - indeed, it is fundamentally wrong.

Note: Since - as already mentioned - no planning documents were available, the above figures are to be regarded as provisional. The inventors hope that a cooperation with the operator of the opencast mine will result; then more exact specifications can be expected.

However, this will hardly shake the basic statement about the enormous short-term storage potential.

Economic potential per m of 3u5ab1e cavity With the Hambach open pit mine, the largest and deepest open pit mine in Germany, a hole suitable for the construction of PSKW is already available. But beyond that, a powerful and proven mining installation is available that can further enlarge, deepen and otherwise shape the hole at the lowest possible cost. Previous efforts and models are aimed only at putting the hole, which is available anyway, to an optimal subsequent use. 39 Date Recue/Date Received 2022-01-10 But that is only a short leap. The obvious question is whether the existing infrastructure, which is optimal and proven for earthworks of any kind and on a large scale, and the relevant experienced employees can be used to expand or prepare the open pit mine in such a way that it can be expanded and converted even more efficiently and on an even larger scale for the new operating purpose of a "pumped storage power plant".

The objective here is twofold: the channel in which the hollow sphere accumulators are to be embedded can be used to = be deepened to allow higher operating pressures and thus better utilization of the cavity volume and/or = be widened in order to achieve an even greater number of efficiently operating hollow sphere accumulators and thus an increase in capacity The key technical-economic argument here is the low additional cost of constructing an additional hole on the floor of the open pit. Since we have not found a handy publicly available quote for this, we first present a somewhat bumpy estimate of our own and then draw far- reaching conclusions from the low value obtained of just under 20 [Ã/m3] per free void volume at the working level.

What is the cost of producing 1 m3hole at great depth H in open pit lignite mining.

In the brochure "WAS BRAUNKOHLESTROM WIRKLICH KOSTET" (/Greenpeace 2018/), published by Greenpeace, the market price for lignite is estimated at 13.8 Ã/t, based on the 2016 annual financial statements of LEAG (formerly Vattenfall Europe Mining). With a density of lignite of rho_BK = 1250 [kg/m3 ], -by the way, there are also smaller values in the literature- this results in a lignite volume price of approx.: 17.5 [Ã/m3]. According to Wikipedia /Wikipedia #Lignite/, open pit lignite mining results in a volume ratio of overburden to coal of about 6.2 to 1. Unfortunately, in the same article, the same value is also given as the ratio of production and overburden quantities in [t].

We therefore choose for the "hole factor", which indicates the ratio of the total hole from coal + overburden to the pure coal volume, a round calculated value Hole factor = 6 (41) Date Recue/Date Received 2022-01-10 The extraction of 1 m of 31ignite therefore creates a total hole of 6 m3.

Unfortunately, we do not know exactly where contributions to this total hole are made everywhere in opencast mining, because the dead rock occurs not only in the immediate vicinity of the extracted product, but also in higher-lying overburden layers, whose removal is what makes access to the lignite possible in the first place. In underground coal mining, where dead rock but no higher-lying access overburden accumulates, it can be assumed that the proportion of tailings in the raw production coal is approx. 50% (/Reuther 2010/, Fig. 351, upper drawing). Based on this value, we assume that for each meter of 31ignite, about 1 meter of 3waste rock is extracted from the same depth; this results in a gross hole of 2 meters at the same depth. 3 TaubesGesteinFactor = 2 (42) Further above it was shown that for the hexagonally densest sphere packing a filling factor of about 0.45 is to be expected. At a value of 1/2, the fill factor would exactly offset the effect of the above TaubesGesteinFactor, Eq(42). Given the coarseness in estimating the TaubesGesteinFactor, we can therefore make a descriptive statement.

Interim conclusion: Active lignite mining generates - according to our rough estimate - for each cubic meter of lignite = an access hole of about 4 m in3the upper part. = a hole of about 2 m in3 the depth of the open pit, which 3results in a useful hole of 1 m that can be used directly as a storage volume.

After these considerations, we can answer the question about the cost of a memory hole.

Conclusion: A usable hole that can be used directly as a storage volume in the excavation stage costs approx. 17.5 [Ã/m3], rounded up to approx. 20 [Ã/m 3]. So: Compared to the specific volume construction costs of 225 Ã per m of 3concrete used (!), as presented above for the StEnSea project, the costs for the construction of the usable hole are hardly significant. 41 Date Recue/Date Received 2022-01-10 But if the production of the storage hole is so relatively inexpensive, then it might even be attractive to dig deeper for storage extraction alone, even without lignite production.

Therefore, we ask ourselves the question: Is it worthwhile at all to build directly on the bottom already?

We consider a 100 m high sub-basin constructed from standard hollow spheres according to the StEnSea project (see above) and built on the current bottom of the flume at a depth of 400 m. For the useful volume V_Sp, an external volume V_a is used according to Eq(12) with V_a = V_Sp / x_V , with x_V = 0.579 (43) .. The unit price of 225 ern given on the concrete volume (V_a-V_Sp)3 can be converted to a reference to the storage volume V_Sp with a factor depending only on x_V. Then the pure construction costs K_400 for the lower basin per m result in3 K_400 = (V_a -V_Sp) = 225 [ Ã1 K_400 = V_Sp = [(1 - x_V ) / x_V ] = 225 [ Ã] .. (44) where for the "StEnSea sphere" applies: [(1 - x_V ) / x_V] = 0/28 Now we sink the lower basin mentally by 100 m downwards; as additional costs for this construction measure only the above mentioned about 20 Ã per m of3the storage volume V_Sp arise. Thus, we obtain for the structure at the greater depth the costs K_500 at K_500 = V_Sp' ([(1 - x_V) / x_V] .225 + 20) [ Ã] (45) This increases the construction cost of the "buried" subbasin by a factor:

K_500 / K_400 = (225 = [(1 - x_V ) / x_V] + 20) / (225 = [(1 - x_V ) / x_V ] ) (46) K_500 / K_400 = 1 + (20 /225) = [ x_V /(1 - x_V)] = 1,12 (46a) 42 Date Recue/Date Received 2022-01-10 CA03146745 2022-01-10 thus only by 12 %. On the other hand, according to Eq(6), the storage content increases by a factor of x_h = [ h LIE 100- obh 1 / [ hu - h obi = approx. 450/350 = 1.29 (47) thus by 29 %. So digging in can pay off significantly.

Now one could object that the higher spheres could be built with thinner walls. This is correct in principle and would lead to a proportionality of the required wall thickness with the pressure when using the boiler formula, which can actually only be used for thin-walled spheres. However, additional ballast would then have to be added for buoyancy safety. In addition - and this is the decisive argument - the unit price of 225 Ã/m3 primarily includes the costs for the formwork and ancillary costs, and not much could be saved there. If, for example, a fixed amount of 125 Ã for the formwork etc. is deducted from the unit price and the concrete costs are reduced by a factor of 1/x_h, then a consideration analogous to Eq. 46 results in K_500 while retaining the costs:

K_500 / K_400 = (225 / 0/28 + 20) / ((125 + 100/x_h) / 0/28) = 1.18 The 29% increase in storage capacity is therefore offset by an 18% increase in costs. This also remains attractive, although no costs have yet been calculated for the additional ballast.

Conclusion: It may therefore be worthwhile to dig even deeper at the depth already reached using existing production technology and to develop new and deeper storage volumes.

Energetic potential per m 3 In the following, we compare the cumulative electrical withdrawal current from 1 m of3 storage volume with the one-time electricity generation from the amount of lignite mined at the same effort and cost.

In the previous chapter, we have stated as a conclusion that a useful hole that can be directly used as a storage volume in the mining stage costs approx. 17.5 [Ã/m3]. Likewise, it was shown there 43 Date Recue/Date Received 2022-01-10 CA03146745 2022-01-10 that the estimated lignite production price is 13.8 Ã/t, which corresponds to a volume price of 17.5 [Ã/m3]. So, the production of one m3 of lignite and one m of 3usefu1 hole costs about the same in open pit mining. We have calculated above with a lignite density rho_BK= 1250 [kg/m3] and therefore there are 1.25 tons of lignite in one m of3 lignite. For a modern lignite-fired power plant, the specific fuel input is given as 0.9 [kg/kWh] (/Wikipedia #KraftwerkNiederauflem/), which corresponds to a volume-related input of 0/2 [m 3/MWh]. So: A storage hole (= useful hole) of 1 m 3costs as much as 1 m 31ignite; this lignite produces 1.39 [MWh/m 3] in a modern power plant.

At a depth of 500 [m] and a turbine efficiency of 90%, a storage well provides 1.24 kWh/m3_h0hl.

Conclusion: The storage hole would therefore have to store 1120 cycles of electricity until it reaches the one-time combustion power of lignite. Depending on the annual number of full-load cycles, this should be reached in 5 to 10 years.

Further embodiments and details on construction and design In the following, some further embodiments and details on the construction and design of the storage system according to the invention are given; whereby we continue the numbering started above. (6.) Widening of the bottlenecks Fig. 6 shows a section of Fig. 4 with the top layer of pressure vessels 3 and the second top layer 3".

Of importance is the shape and size of the bottleneck: In a preferred embodiment, the horizontal great circles of adjacent spheres abut at 6 points in each sphere plane. If one considers a particular sphere (see Fig. 6), at each of these points of contact with the neighboring spheres there is a free equilateral triangle whose sides are segments of circles. If we look at the triangles of this type which follow each other along a horizontal line in the x- or y-direction, we see that they exist in two orientations A and B which are mirror-symmetrical with respect to the lines. 44 Date Recue/Date Received 2022-01-10 In the hexagonally densest sphere packing, the individual sphere planes are identical, but adjacent sphere layers are offset from each other and only the next but one sphere planes lie congruently on top of each other again. If we now look at the overlap of the triangles of the lower layer with the great circles of the upper layer, we see that half of the lower triangles lie completely under an upper sphere and the other half of the lower triangles lie under a triangle of the upper layer, but the triangles lying on top of each other are of different orientation, i.e. above a lower triangle of orientation "A" lies in the upper plane a triangle of orientation "B". and so on:

In each equilateral triangle a largest possible circle can be inscribed. These circles do not change with mirroring, so that for symmetry reasons all triangles lying on top of each other always have the same circle at the same place despite their 2 different orientations. These circles can be extended mentally to a virtual vertical tube, which results in a completely free vertical "clear" connection through the whole sphere arrangement. Through this virtual "bottleneck pipe" 4 one could for example lower an object (e.g. a not too big turbine) freely on a rope to the ground.

Since the triangles assume only two fixed orientations, the actual "clear" space through the sphere arrangement is even slightly larger and "frayed" into a rhombus, as can be seen in Fig. 6.

The "clear" rhombus is available as a limit for the transport in the case of strictly vertical movement; however, if a small horizontal movement or rotation is allowed in front of the narrow points, the sphere arrangement can transport all objects which fit through the clear triangles of the individual sphere planes. It can be seen from Fig. 6 that with an inner sphere diameter of 30 m, objects with dimensions of 4 to 5 m still fit through.

If one wishes to widen the bottleneck cross sections without making any changes to the spherical shell, this can be achieved during embedding by adding a spacer layer of filler material between the spheres; this spacer layer can then be removed again locally at the critical bottleneck locations.

But there are other ways to widen the bottleneck a bit: = local flattening of the spheres at the bottleneck, which is compensated for structurally by structural reinforcement of the concrete at this point (e.g. by reinforcement, metal plates or rings). = Use of a second type of cavity balls, which have a smaller diameter than the standard balls.

Date Recue/Date Received 2022-01-10 CA03146745 2022-01-10 = Omitting selected spheres so that a sinuous shaft with the desired cross- section can be constructed in the void space thus initially kept free. The space not used for functional purposes can then be backfilled as the installation of the spheres progresses.

In addition, there is also a "software" alternative to avoid too high flow velocities in a bottleneck: after all, one does not have to operate all pump turbines, which have a common access to the upper water reservoir limited by bottlenecks, at full load at the same time, but can distribute the required water flows as evenly as possible to all accesses. .. (7.) Accessibility of the pump turbines The pump turbines should preferably remain accessible for maintenance or replacement via a sufficiently large free channel. This can be done - depending on the concept of equipping with pump turbines (see point (2): self-sufficient, oligotark or central) e.g. with the following two concepts: = The pump turbines 7 are installed at the bottom, laterally in and at the lowest points of the spheres, and use a vertical shaft 24 accessible to several spheres and open at the top as a pre-flood (Fig. 7). (Self-sufficient, possibly also small oligo PT). = Groups of balls are connected via pressure lines 6 to a larger pump turbine 77 responsible for the entire group (oligo / central pump turbine). These pressure lines can lead directly from the sphere via an external independent manifold 6 (Fig. 8a), although it is also possible to group several spheres together in series via short connecting lines from sphere to sphere (i.e. between adjacent spheres) and then connect, for example, the lowest sphere in a series to the pump turbine (Fig. 8b). Note that Fig. 8a and Fig. 8b combine different elements for supplying a pump turbine.

Of course, other variations in the association of storage elements and oligo pump turbines are possible; an example of a comprehensive summary is shown in Fig. 9a.

Similarly, of course, this can be done via direct ball-to-ball connection, as seen in Fig 9b. Other mixed forms are also possible.

In general, it may be suitable that the pressure vessels 3 are regularly arranged in layers next to each other and/or on top of each other in the dry bottom cavity 100 (e.g. in hexagonally tight sphere 46 Date Recue/Date Received 2022-01-10 CA03146745 2022-01-10 packing), with free spaces 2 remaining between the pressure vessels 3 (which at least partially remain as non-adjacent free space 24), which preferably extend from the top to the subsoil 110 through all layers (clear channels 4). In this context, a pressure vessel 3 can be equipped, for example, with an independent turbine 7, pump 7 and/or pump turbine 7, which can be installed in the pressure vessel 3, for example, at the bottom and/or laterally.

Alternatively or additionally, pressure vessel groups may be provided comprising two or more pressure vessels 3 connected to each other via pressure lines 6, 61 and equipped with a common turbine 77, common pump 77 and/or common pump turbine 77. In this case, directly adjacent pressure vessels 3 can be connected via a direct pressure line 61 (short connecting pipe from ball to ball). Furthermore, .. bunkers with common turbine, pump and/or pump turbine 77 can be constructed on or in the subsoil 110 and pressure lines 61, 6 from the storage spheres 3 can be laid there. (8.) Embedding and securing against buoyancy (8a) A first layer of the storage base cells (i.e. the hollow spheres) can be deposited in a dense packing on the bottom of the channel - still in the dry state. (8aa) For stabilization and protection against buoyancy, these elements can then be embedded and/or "slurried" with sand, gravel or stones - whatever is available on site.

Preferably, this is done initially only to the level at which a second layer of hollow spheres can be placed. This embedding can achieve a weighting and a firm suction of the hollow spheres. (8b) A second layer of balls can be placed in the troughs between the balls of the lowest and already partially embedded layer. In this case, the inflow and outflow paths to the pump turbines in the lowest layer can be kept free by pipes (possibly also elastic pipes). Now the hollow spheres and tubes can be embedded by ballast materials according to step (8aa). (8c) In the same way as in step (8b), further layers with hollow spheres can be spread and embedded. 47 Date Recue/Date Received 2022-01-10 CA03146745 2022-01-10 (8d) If one wishes to deploy additional spheres still above the top of the channel, these hollow spheres can be given their own buoyancy control; e.g. either by their own weight (shell thickness) or additional ballast.

Embedding the spheres also serves, among other things, to distribute the pressure when stacking the hollow spheres. Since the embedding is done in the (edged) channel, simple sand can be used.

Because of the walls of the channel, it cannot drift away. (9.) Generator operation during refilling (e.g. of the Hambach lake) During the filling of an open pit mine (e.g. Hambach open pit mine) into a lake, which may take many years, part of the pump turbines can be used as an electricity generator.

Here, for example, the inflow water coming from the Rhine (or elsewhere) can be fed into the turbines. The outflow from the hollow sphere can be done, for example, through an independent outlet spout, which is then .. closed again later. Alternatively, one (or many) oligo unit cells can be used and the inflow can be arranged in a first basic storage cell and the outflow in a second basic storage cell. (10.) Use of the existing infrastructure of the open pit mine:

For earthworks, the existing large-caliber machines of the lignite open-pit mine that is coming to an end are preferably available. These can be used for excavation of the channel, further grading of the lake bottom, relocation in the later lake bed and filling of the cavities between the spheres. (11.) Widening of the channel, steepness With the large-caliber machines that are preferably available (see (10.)), towards the end of opencast mining and even before the lake is filled, the opencast mine, e.g. the Hambach channel, can also be expanded in its footprint. These construction measures can be partially linked to further lignite mining, but they should also be carried out with the independent objective of "preparing the largest possible storage channel". 48 Date Recue/Date Received 2022-01-10 The entire channel can be covered with storage balls up to its edge and filled with excavated material in sections in the course of this installation. This results in a fortification of the slope against any kind of slipping - even after the lake has been filled with water.

During the construction phase, the spheres can also be used to erect temporary support devices in places. This allows an unusually steep shape of the channel wall in the final construction.

Further / alternative considerations Limitation of the storage stroke in the upper basin According to current planning, Lake Hambach will become the second largest lake in Germany in terms of volume after Lake Constance, but the potential of the PSKW is so great that there may be a considerable water level lift at the lake surface. If one wants to reduce this, one can envisage: (12.) Entire lake district as upper basin.

By integrating neighboring opencast mines, a hydraulically connected lake plate can be created so that the water level of the lake plate can be lowered or raised together. By means of sluices or controllable gate valves, the storage lift of the different lakes can be set at different levels, so that different types of use of the individual lakes or even small differences in the levels of the different lakes can be taken into account. (13.) The Rhine as another upper basin The Rhine is about 40 m above sea level and thus about 60 [m] below the level of the fully filled Hambach Lake according to previous planning. The depth of the SeeEi installation in the Hambach Gully of (currently) 400 m is thus still 340 m below the Rhine. It has already been proposed to use water from the Rhine to fill Lake Hambach. If one were to build a large- dimensioned tunnel to the Rhine at the same time as reducing the area of Lake Hambach and lowering it by about 60 m, Lake Hambach and the Rhine would be permanently hydraulically connected and both could serve together as the upper basin of the PSKW. 49 Date Recue/Date Received 2022-01-10 Astrong hydraulic connection between the two receiving waters would buffer the level fluctuations, so that the level of Lake Hambach could be smaller or at least would not have to be extremely low for a long time.

However, if the entire potential of the Hambach Gully were to be served by a Rhine tunnel, unusually large tunnel cross-sections would have to be provided. Note that only a comparatively small cross-section is needed to fill Lake Hambach, which is expected to take years or even a decade. "Mining" access to PT stations through supply lines 67.

It often leads further to approach a problem from a completely different side.

We now ask ourselves: can accessibility to the pump turbines also be achieved from the side instead of from above?

The lake bottom 1 is initially dry, freely accessible and can be worked with large and heavy equipment. Referring to Fig. 10, we can therefore make the PT bunkers accessible by a suitable roadway network 67 and, if necessary, also sink a deep shaft 5 down to the later bottom of the lake (see Fig. 11). Then a pipe 44 can be provided from a PT station 77 to the free lake 0, which serves to transport water, but no longer necessarily has to serve as access for maintenance and repair. In general, a connecting pipe or an intermediate space 2 designed as a shaft 44 can be provided between common pump/turbine/pump turbine 77 and free lake 0. Later, after the lake has been flooded, this then functions like a mining development of stations in an invert: the roadways contain the power lines and access for material and personnel and are connected to the outside world - as in a mine - via one (or even several) shafts 5 (Fig. 11). In particular, a drivable roadway 67 may be provided that runs in the lake bottom 1 and connects the PT stations 77 to a central supply and/or personnel shaft 5.

Shaft 5 provides an external connection to one or more lines 67; in addition to a supply and passenger shaft, this can also be realized by a steep but still passable tunnel tube. Instead of a shaft 5, the access to route 67 can also run as a passable and watertight tunnelled mountain road on the slope of the lake and be constructed in the dry long before the lake is flooded. Then it can also be used during the construction period of the PSKW plant.

Date Recue/Date Received 2022-01-10 Subsequent expansion "in situ" by self-sufficient storage elements 30 Assume that a PSKW plant, e.g. as shown in Fig. 10, is already in operation and is now to be expanded when the lake is full. This can be accomplished by adding additional pressure vessels 30 by lowering them onto the already arranged pressure vessels 3 located at the bottom. In particular, self-sufficient pressure vessels 30 (hollow spheres) can be superimposed (so to speak "epitaxially") on the existing system in the already existing troughs (Fig. 12).

Electrically, the self-sufficient storage elements can first be grouped together on the upper side of the lower basin and led down to the section 67 at one or more points - e.g. using connecting pipes 44 of the existing plant. It is advisable to prepare the electrical connection to the section 67 already during the "dry" installation of the storage system or to carry it out already.

Procedure for the phased construction of the large-scale PSKW

Germany's largest open-pit lignite mine would have the potential to accommodate more than 10,000 cavity reservoirs as sub-basins for a combined large-scale PSKW. One might not want to wait long until open pit mining is completed, then install the substructure and all the cavity spheres, then fill the lake, and only after many years put the PSKW into operation.

There is, however, an elegant procedure for erecting some of the facilities earlier, testing them extensively, expanding them section by section and, if necessary, putting them into operation before coal production ceases. This slow process, which can be perfected through experience and technical improvements, may be desirable for such a large-scale project.

The simple basic idea to be exploited here is the following: The elaborate pressure-resistant lower basin with its built-in pump turbines does not necessarily have to be operated with the entire water body of the reclamation lake that will later be used as the upper basin.

Basically, any other available large or small basin at the top of the open pit can be used for this purpose, provided only that the hydraulic connection intrinsically given by the lake later is replaced by temporary pressure pipes 86 (Fig. 13). 51 Date Recue/Date Received 2022-01-10 For example, a procedure with one or more of the following process steps may be considered. 1. especially in the shore zone of the later lake (e.g. Hambach Lake), an interim upper basin 80 is built, which is separated from the current open pit by a dam 84 (dam wall, basin wall). 2. for example, one first builds only a small part of the already exploited channel (partially built sea- egg sub-basin 83) and, if necessary, advances further afterwards. In other words, for the interim solution, the already arranged pressure vessels 3 are connected via a pressure pipeline 86 to a vessel 80 or basin 80 forming a temporary upper reservoir delimited from the bottom cavity 100.

Thus, in particular, a pressure pipeline is established as a hydraulic connection between the interim upper reservoir and the already arranged pressure vessels 3, i.e., the first construction sections of the SeeEi subbasin. For example, the "clear geometric bottleneck shaft 4" in the "open water access room 24" can be replaced by an internal pressure pipe and connected to an interim pressure pipe 86, which runs to the aforementioned interim upper basin (see 1.). One can, for example, create a unit consisting of several hydraulically coupled cavity spheres with an oligo- powered pump turbine, but one can also connect only a single self-sufficient sphere with a built-in pump turbine to such an interim pressure pipe for test purposes. 3. The interim upper basin 80 can be sized to accommodate the storage water of the initially planned lower basins, but it can also be expanded as they continue to be added. While open pit mining is still active, the interim PSKW created in this way can not only be tested but also already operated commercially ("interim operation"). 4. after the end of coal mining and further development of the open pit to its final shape, the other sub-basins can be built or pressure vessels can be arranged in the whole planning area. Then the bottom depression can be filled to form an artificial lake, which will replace the interim one as the final upper reservoir. During the filling period, the part of the sub-basins already connected to the interim upper reservoir can continue to operate as before.

When the entire lake is filled with water, the interim pipe connection 86 can be released. The part of the subbasin previously assigned to the interim PSKW can then be used as a "lake egg" in the same way as the later installations according to the invention. 52 Date Recue/Date Received 2022-01-10 The interim upper basin 80, which is separated from the actual "working lake" by dam 84, can be used (later) as a reclamation lake for recreational activities and the like (recreational lake). For example, one can row (or swim) to the dam wall as in a large "infinity pool" and take a look at the working lake. 7. the working lake, which corresponds to what was previously referred to as the upper basin or free lake water 0, because of the hydraulic and access separation from the reclamation lake (the former interim upper basin 80), can now be operated essentially along engineering lines and, for example, have an unusually large lift.

Depending on the size and seasonal variation in use of the interim upper basin, it could of course also be used for a modest and controlled drawdown; after all, people also go swimming in the North Sea despite the ebb and flow of the tide.

Figs. 19 to 22 again show various stages in the construction of an underwater PSKWin a depression 100, in this case the Hambach open pit mine. Fig. 19 shows the Hambach 100 open pit mine in a dry state before the start of construction of the PSKW plant.

In Fig. 20, a lower reservoir 83 (with hollow bodies) has been constructed at least in part in the ground depression 100 and connected to a temporary upper reservoir 80 (interim lake/assembly lake) via pressure lines 86 (pipe connections during the assembly period). The interim upper reservoir 80, which is higher than the lower reservoir 83, is also located in the bottom cavity 100, in particular at the edge of the bottom cavity 100, and is separated from the rest of the open pit by a boundary 84 (dam/separation dam/basin wall). For cost reasons, it may be desirable that the interim lake 80 and the dam 84 be relatively low. Preferably, the dam 84 may be constructed on a contour line of the ground depression through the ground depression 100 (in this case, the Hambach Hole) in order to securely base it. In Fig. 20, the dam 84 is constructed approximately on a terrace of the open pit; this allows the interim lake 80 to have a concave shape desired in terms of pressure and to conform nicely to the landscape. At the stage shown in Fig. 20, the already partially constructed lower reservoir 83 can already be used and/or tested to gain experience for further construction of the lower reservoir 83. In the process, the preliminary upper reservoir 80 undergoes a level lift. 53 Date Recue/Date Received 2022-01-10 Referring to Fig. 21, once the lower reservoir is completed, the bottom depression 100 may be flooded so that the lower reservoir remains at the bottom and is covered by the artificially formed lake that forms the final upper reservoir 300 with level lift. The pressure lines 86 to the interim lake 80 can be disconnected. Eventually, the interim lake 80 can be transformed into a recreational lake, which no longer has a level lift. The top of the dam can be transformed into a boardwalk between recreational lake 80 and working lake 300, which is also popular for bicyclists, for example. Fig. 22 shows an embodiment in which the boundary 84 is built circumferentially in the bottom depression at its edge, so that the temporary upper reservoir 80 (or possibly later the recreational lake) runs annularly around the part of the bottom depression in which the lower reservoir is built.

Method for sea-based deployment of the hollow bodies Compared to the deployment of a sea egg on the high and deep seas, the installation of a hollow sphere reservoir in an open pit that is dry or to be flooded can be much less costly. One possibility .. is, for example, an approach involving one or more of the following process steps: (1) Construction of the installation section 66 and preparation of the foundation soil. (2) Construction of the 1st level of the sea eggs primarily as a structure on site. Installation of the connections to the installation sections 66. The construction site access, for example, is via the still .. undeveloped bottom. It is therefore possible to proceed in the same way as for the construction of a new settlement area. (3) Flooding the channel and the hollow bodies with water. (4) Further flooding with covering of the structural facility so that the channel becomes a "navigable" waterway. (5) Establishment of a central construction site for the mass production of the hollow bodies as a shipyard on the edge of the waterway. (6) Launching of the hollow hulls, which may be made buoyant by means of laterally attached floats ("air cushions"). (7) the floating hollow bodies are towed on site, where they are slowly and gently lowered by controlled inflow of water so that they rest in the correct orientation in the designated troughs of the lower tier. 54 Date Recue/Date Received 2022-01-10 CA03146745 2022-01-10 (8) In analogous repetition of steps 4 to 7, the second and then likewise the further floors of the subbasin are created.

Note on step (2): As an alternative to step (2), the lowest hollow body level could already be excavated using the floating method analogous to steps 3 to 7 after suitable preparation of the foundation soil.

Further remark: The channel can be divided into construction sections by earth walls (and/or other suitable measures of site equipment). The pump turbines of the already installed equipment are available for empty pumping and filling (see further above).

Note on the above calculation examples: We consider this combination of floating on-site approach and "dry" hydraulic and electrical connection described here to be minor compared to the corresponding effort for a sea egg installation on the high seas. Therefore, we have not included the calculated high installation costs of the StEnSea project (see above) in our rough cost estimate.

Note on sphere diameter: The diameter of a hollow sphere is limited by the dimensions of the manufacturing shipyard and by restrictions on transportation from the shipyard to the docking site.

The water-based method of deploying the hollow sphere described above, with its alternation of "shallow" sinking after the floating approach and "dry" electrical (and possibly hydraulic) docking, appears to make it possible to build really large spheres. In the Stensea project, one already had the courage to build 30m spheres, now one could perhaps be even bolder.

Large and small balls: Then it becomes worth considering also a construction of spheres with different diameters. This becomes interesting when, for intrinsically buoyancy- compensated spheres, suitable crystallographic gaps of a basic lattice of large spheres are filled by small spheres.

This increases the packing density and thus leads to a higher filling factor Ffill of the entire subbasin.

Process for generating energy when filling the lake.

The procedure described above for the phased construction of the large-scale PSKWmakes preferential use of an infrastructure consisting of interim upper basin 80, pressure pipeline 86 and Date Recue/Date Received 2022-01-10 CA03146745 2022-01-10 storage units 83 in the lower basin already installed and equipped with pump turbines. Thus, the technical devices are already in place that can also be used to run the feedwater for filling the reclamation lake via the existing turbines. A simple way would be to fill and empty the already installed SeeEi storage units in a periodic batch operation, which can consist of three stages: = The feed water is first discharged into the interim upper basin 80. = From there, it flows via pressure line 86 into already installed sea-egg units 83 until they are filled. = the water is pumped from the already installed SeeEi sub-basins 83 into the lake, which only rises slowly as it fills up.

If several SeeEi units are already installed, the process can be quasi- continuous, with the filling and pumping out of individual units taking place with a time delay.

If there is not enough above-ground feed water available and recourse is made to an underground tapping of the Rhine, the Rhine water can first be pumped up to the level of the intake of the penstocks in the interim upper basin 80. It may also make sense to install an intake at the level of the Rhine level, which would be about 60 [m] below the later level of the reclamation lake (see above), on the penstocks 86 laid in open cut construction from the outset. It would also be possible to design the interim upper basin from the outset so that it has the necessary depth at the appropriate point.

Two remarks on the construction and gentle operation of the storage spheres.

No frictional compressive stress: The hollow spheres are designed in particular for the externally acting pressure of the water column of the (later) lake. An analogous internal pressure, theoretically possible via the pressure pipe in interim operation, cannot occur if - as envisaged - the hollow sphere is operated without an enclosed air cushion and, when filling with water, the inlet valve of the turbine closes just before 100% filling; then only the pressure of the local water volume always prevails in the sphere and there is no pressure surge. The hollow sphere is therefore not subjected to tensile stress (inside to outside) during interim operation, in particular due to the non- compensated water pressure from the pipeline, but acts hydraulically more like an open basin. 56 Date Recue/Date Received 2022-01-10 Even during subsequent sea operation, it is ensured that there is no frictional pressure connection with the deep water inside the sphere and that the pressure on the hollow sphere does not change continuously between deep pressure and pressure equalization (fatigue due to cyclic pressure relief). During the test operation, a safety valve can be used to ensure the correct procedure.

Comment on a continuous 3-D printing of the hollow sphere formwork: Efforts will be made to make the mass production of the hollow spheres as inexpensive as possible, so that ultimately only the pure concrete costs really come into play. The wall thickness of the hollow spheres is unusually thick, e.g. 2-3 m, and this opens up the possibility of using 3D printing processes, if necessary without external formwork. For this purpose, we imagine that during a step-by- step construction of the hollow sphere, a formwork collar is first created at each of the inner and outer edges of the flat cross-sectional surface of the spherical shell using a suitable concrete or other material, which is then filled with the structural concrete after solidification. In this way, it could be possible to print or cast the entire hollow sphere layer by layer under computer control.

Design with storage tubes With reference to Figs. 14 to 17, the pressure vessels 3 arranged in the bottom recess 100 can also be designed as tubular pressure vessels 30 (storage tube elements). In the example shown, the tubular pressure vessels 30 have a circular cross-section and are arranged vertically next to each other in the floor recess in such a way that they form a single plane in which the pressure vessels 30 are arranged in the densest spherical packing (see Fig. 17). Further levels are not provided in this example. The pressure vessels 30 are connected via pressure lines 6 to common pump turbines 77, which are connected (via a valve 78) to connecting pipes 44, 44 leading to the sea.

As shown, connecting pipes 44 (water-carrying pipes from the upper lake to the turbine) may be arranged vertically and between the pressure vessels 30. The vertical connecting pipes 44 to the sea may in turn lead to the pump turbines 77 via horizontal connecting pipes 44, which may run underground. As can be seen in Fig. 15 and Fig. 16, the pump turbines can each be arranged in an accessible and/or drivable supply shaft 67 below the subsoil 110. For this purpose, a concrete substructure 68 can be provided in which the supply shaft 67 or even several such shafts 67 run (substructure with turbines, valves, cables, etc.). 57 Date Recue/Date Received 2022-01-10 Fig. 17 shows a top view of the tubular pressure vessels 30 and connecting pipes 44 arranged between them to the sea, in which the arrangement in the densest spherical packing can be clearly seen. Several, in particular adjacent, vertically arranged tubular pressure vessels are operated by a common pump turbine 77 as a pressure vessel group. In the example shown, the pressure vessels 30 form a group, the pressure vessels 30" form a group, and the pressure vessels 30'" form a group, each of which is operated via a common pump turbine 77 and is connected to the sea via a common connecting pipe 44.

Specifically, in the example shown, a pump-turbine unit is provided to supply nine storage pipes 30, 30, 30. Each storage pipe in the example is approx. 300m high (height h) and has an outer diameter of 30m and an inner diameter of 25m.

This results in the following exemplary estimate: internal volume: Tr = r2 = h = 3,14 = 12,5 2 m2 = 300 m = 147.187 m3; volume per turbine unit 9 = 147,187 m3 = 1,320,000 m3;

At 1000m depth, the storage energy per turbine unit is about 2.0 = 9 = 147,187 m3 = 2,600,000 kWh; turbine power 200 kW, Le., this unit can provide 200 kW of power over about 13h; Since at 800m depth, 1 m 3per second provides 2.0 kW, 200 kW of power is generated when 100m 3per second passes through the turbine. 600 turbines of 200 kW each can thus generate 120 GigaW of power over 13 hours, i.e. one such turbine alone can supply all of Germany with electricity for a full day. The amount of water per second would then be 60,000 m3 per second. If the area of the flooded lake is 40 km2, the water surface of the lake sinks about 1 mm per second or by 50 m per day.

Some advantages of the invention Depending on the embodiment, some or more of the following advantages may result.

Advantages of size and depth = Due to the still existing availability of the (powerful) open pit infrastructure, the current operation can be redirected to a different target fulfillment with basically the same mode of 58 Date Recue/Date Received 2022-01-10 CA03146745 2022-01-10 operation; therefore, there are one-time favorable costs for the creation of empty space, which can later be built on with cavity structures for storage purposes. = It is therefore worthwhile for PSKW to produce unusually large storage capacities and height differences. = Greater depth of the "lower basin" reduces the level lift per MWh of storage energy, Design and operational advantages = By using similar elementary basic cells, the advantages of mass production can be exploited. = The edges of the channel are stabilized by filling with hollow spheres, so that a steep slope angle and therefore a wide channel can be achieved. = Very compact plant with a high fill factor and therefore low loss of height = Free access to pump turbines for maintenance, repair and replacement. = Compared to an erection in an existing inland lake or on the seabed, a first layer can be erected in the dry, with a level subsoil being created beforehand if necessary. This would not be possible with hollow spheres on the seabed.

Safety and error-friendliness = The wide-area flow from the lower basin to the upper basin caused during operation; which are fed from many decentralized inlets and outlets, ensures low flow velocities even in the area of inflowing or oufflowing water. The funnel-shaped channel to the constrictions also results in a calming of the flow. = Safe damage limitation in a "worst case scenario": In the self-sufficient case, in the event of a rupture of an empty pumped sphere, the collapsing volume remains limited to the sphere cavity (i.e. there can be no "tsunami" in the working lake!). = Fault-friendliness: in the event of leaks, only a small self-contained part of the "cellular" entire storage system is affected at any one time, so that in the worst case, this part can simply fail and be abandoned without interfering with the operation of the rest of the system.

Advantages during construction = A part of the PSKW plant can already be erected and tested in a provisional manner as an interim structure in parallel with the coal mining operations that are being phased out. This 59 Date Recue/Date Received 2022-01-10 CA03146745 2022-01-10 part can also be used to generate electricity from the potential energy of the feedwater when the lake is filled = the interim installation can be used to generate energy during the initial filling of the lake = The sea-based deployment of the hollow bodies and the "dry" electrical and hydraulic integration into the overall system result in a comparatively simple and cost- effective installation - even for large storage bodies.

Ecological and social benefits = The amount of water in the lake remains unchanged, therefore the weight of the lake also remains constant. = Long service life: Since, in the case of spheres, these are essentially subjected to compressive stress and there is also very little dynamic loading during operation, iron reinforcement of the concrete can be dispensed with if necessary. This can extend the service life (no rusting of the steel reinforcement) to hundreds or thousands of years (Roman buildings), so that a sustainable investment is made in future energy supply from which many generations will benefit. = Despite enormous storage capacity, the requirement for recultivation and recreational use is maintained = The construction and partial commissioning of this PSKW can take place in parallel with the phase-out (e.g. by 2038 of lignite mining), so that none (or only very few) of the existing jobs are destroyed Outlook: "Cavity open pit mining" only for the purpose of PSKW construction.

In the Rhenish lignite mining area, and in particular in the Hambach open pit mine, a huge depression is already available; in order to set up a large-scale PSKW, most of the excavation has already been carried out under other objectives, and we can also expand this large hole and make it even deeper.

In the case of underground PSKW, too, one looks first to a rededication and adaptation of the existing mines of the expired hard coal mining industry, although the question has already been Date Recue/Date Received 2022-01-10 CA03146745 2022-01-10 raised there whether it would not be simpler to construct new and very large underground storage facilities exclusively according to the requirements of PSKW operation (/LuSchmB Bergei2/).

So let us ask ourselves whether it is not also possible to build large-scale PSKWplants directly "on the greenfield" (or "on the yellow sandy desert") from the upper edge, independently of any lignite production that is being phased out. So what has to be considered if one wants to create a deep lake in a suitable environment with the proven production methods of an open pit mine as a combined upper and lower basin for a large-scale PSKW somewhere in the world.

This question is particularly interesting for arid and sunny locations, for example in North Africa.

There, the question of intermediate storage of PV electricity is easier than here in the temperate climate zones. Because of the great uniformity of solar irradiation, one can assume a high demand for short-term storage for daytime smoothing and bridging of the night hours, which, with suitable dimensioning, allow a largely predictable almost daily utilization. Bieringer was able to show that in Morocco, with a largely PV-supported power supply in the future and constant demand over time, even large short-term storage facilities with a storage capacity of 13 full- load hours can still be expected to achieve a full-load cycle rate of about 300/a and more /Bieringer 2019/. This is about twice as much as calculated with the same model for short-term storage in Germany. However, this means that at the same electricity price, the cost per stored kWh may be twice as high.

Considering again the cost structure of the StEnSea storage sphere (see above "Underground and subsea - PSKW") and the considerations made in the chapter "Economic potential per m 3u5ab1e cavity", the following costs per m usable 3ho1e (denoted as [m 3_11A) apply for the large-scale PSKW in deep opencast mining at a depth of about 500 m, using the concrete costs from Eq(45) and the used volume factor from Eq(44). (pos. 1): Concrete costs (incl. formwork etc.): approx. 165 Ã/m3_hohi( =0.728 '225) (pos. 2): Creation of the useful hole: approx. 20 Ã1 m 3_hohi Together, this results in 185 Ã/m3_hohifor a 100 m high sub-basin with base point at 500 m depth. 61 Date Recue/Date Received 2022-01-10 Now, we have to separately set up and add the preliminary workings of the open pit up to 400 m depth. For 1 [m 3_honi] usable hole we needed a gross hole of 2 m 2area and 1 m height in the usable depth. For the considered subbasin of 100 [m] height, we therefore need a base area of also 2 [m2] for 100 m usable 3ho1e and have to add a direct excavation volume on 2 = 400 = 800 [m 3] for this from the top edge. To this must be added the proportionate excavation for the embankment, for which we apply a flat rate of 25%, resulting in a total excavation of 1000 [m3relation to a unit storage volume of 1 [m], an 3_hohiadditional 10 [m] 3gross hole must therefore be excavated.

Further above we have stated that one 3produces an average total hole of 6 m per m of 3extracted lignite in total (i.e. at different heights of the open pit). At a lignite price of 17.5 ern, the 3excavation cost is therefore approx. 3 Ã /m3, which means 30 Irn 3_hond in relation to the unit useful hole.

We can therefore add a 3rd item to the above cost summary. For the erection of a comparable large-scale PPP (500m invert, 100m high lower basin) on a "greenfield" site, we add: (pos.3) Additional excavation of the surface course: 30 Im3_honi]

The costs for pump turbine and electrical system are estimated at 525 [Ã/kW] in the StEnSea project. With an electrical storage density of approx. 1 kWh/ m3_hohi(corresponding to a height difference of approx. 400 [m]) and an on/off storage time of approx. 5 h, the following electrical expenditure is added in both cases: (pos. 4) Pump turbine + electric: 105 Im 3_hohi] at 5 h turnaround time You can tell: = The additional construction costs for building a large and deep PSKW plant on a greenfield site instead of on the bottom of an abandoned opencast lignite mine are relatively low; in our roughly calculated example, they were about 15%. = A large and deep PSKW can also be built "on the yellow sand" if the utilization is favorable - as is to be expected in sunny areas with PV as a power source - and if the geology of the site is favorable for opencast mining (comparably favorable as in opencast lignite mining). = The above calculation underlines the importance of the height of the lower basin, to which, after all, the excavation of the deck faces can be apportioned. 62 Date Recue/Date Received 2022-01-10 When used in arid or even semi-arid areas, evaporation from the reservoir can be reduced by using a floating cover unless a body of water is available for refilling. 63 Date Recue/Date Received 2022-01-10 BIBLIOGRAPHY /Baufume e.a-2011/

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Date Recue/Date Received 2022-01-10 DE10 2014 007 184/. verfOgbar Ober: http://vvvvvv.fze.uni-saarland.de/Speicher.htm /LuSchmB 2014/

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Wikipedia (aufgerufen am 1.3. 2019) https://wwv.wikiwand.com/de/Tagebau Hambach 69 Date Recue/Date Received 2022-01-10 REFERENCE LIST 0 Seawater 1 Bottom 2 Gap between pressure vessels 22 "Backfilled" access room 24 "Open" or "open water" access space 27 Blind shaft 3 pressure vessel 30 Tubular pressure vessel, 4 "Light geometric bottleneck shaft" 44 Connecting pipe to the sea 5 Shaft 6 Junction pipe, distribution pipe work 61 Connecting pipe from pressure vessel to pressure vessel 66 Connection level 67 Accessible/drivable route 68 Concrete substructure 7 Pump turbine 77 Community pump turbine 78 Valve 80 Preliminary upper reservoir 83 Partially constructed lower reservoir 84 Dam 86 Penstock 90 Fill material 100 Soil depression in the ground 110 Subsoil of the ground depression 120 Wall of the bottom depression 200 Lower reservoir 300 Upper reservoir Date Recue/Date Received 2022-01-10

Claims (15)

1. A method for the provisional use, preferably for test operation, of an at least partially constructed lower reservoir for an underwater pumped storage power plant, wherein an at least partially constructed lower reservoir is provided, which is arranged in a dry but floodable bottom depression, preferably in an open pit mine, and which, when the dry bottom depression is flooded, is operable in such a way that electrical energy is generated when water is admitted from the flooded ground depression into the lower reservoir and electrical energy is stored when water is pumped out of the lower reservoir into the flooded bottom depression, and wherein at least one temporary upper reservoir is constructed above the at least partially constructed lower reservoir, the upper reservoir being smaller than the dry bottom depression, and wherein the at least partially constructed lower reservoir is connected to the temporary upper reservoir via a pressure line so that the lower reservoir can be temporarily utilized such that electrical energy is generated when water is admitted from the temporary upper reservoir into the lower reservoir and electrical energy is stored when water is pumped from the lower reservoir into the upper reservoir, and wherein preferably the at least partially constructed lower reservoir is provisionally used or tested by admitting water from the provisional upper reservoir into the lower reservoir and/or pumping water from the lower reservoir into the upper reservoir.

2. Method according to the preceding claim, wherein a preliminary upper reservoir is constructed by dividing the dry bottom depression, preferably the open pit mine, in such a way that a first partial area is formed in which the at least partially constructed lower reservoir is arranged, and a second partial area is formed which constitutes the preliminary upper reservoir.

3. A method according to the preceding claim, wherein the dry bottom depression, preferably the open pit mine, is partitioned by erecting therein a dam, a retaining wall or other delimitation. 71

4. A method according to any one of the preceding claims, wherein a temporary upper reservoir is constructed by excavating or providing a further bottom depression adjacent to the dry bottom depression, the further bottom depression forming the temporary upper reservoir, or constructing a basin adjacent to the dry bottom depression, which forms the temporary upper reservoir.

5. Method according to any of the preceding claims, wherein the dry bottom depression, preferably the open pit mine, or the partial area in which the at least partially constructed lower reservoir is arranged, is further widened and/or deepened, preferably with open pit mining machines already present on site, after the at least partially constructed lower reservoir has been connected to the preliminary upper reservoir and has preferably been provisionally used or tested, wherein the further widening and/or deepening is carried out preferably for the further extraction of mineral resources in open pit mining operations.

6. A method according to any one of the preceding claims, wherein the at least partially constructed lower reservoir is converted and/or expanded after it has been connected to the preliminary upper reservoir and preferably provisionally used or tested and/or wherein the preliminary upper reservoir is reconstructed and/or expanded after being connected to the at least partially constructed lower reservoir.

7. A method according to any one of the preceding claims, wherein the at least partially constructed lower reservoir comprises a plurality of pressure vessels which are arranged next to one another and/or above one another in the dry bottom depression, e.g. on a lower floor of the open pit mine, and/or wherein the at least partially constructed lower reservoir is rebuilt and/or extended in such a way that further pressure vessels are arranged next to and/or above the already existing pressure vessels and/or wherein preferably after the lower reservoir has been rebuilt and/or extended, at least 100 pressure vessels are comprised, preferably at least 1000 pressure vessels are comprised and even more preferably at least 10,000 pressure vessels are comprised. 72

8. Method according to the preceding claim, wherein at least some of the pressure vessels have a shape which fills at least 25 percent, preferably at least 50 percent, particularly preferably at least 75 percent, of the volume of a smallest possible envelope sphere and/or wherein at least some of the pressure vessels are formed preferably as a pressure- resistant sphere, egg shape, ellipsoid or polyhedron and/or wherein at least some of the pressure vessels each have a volume of less than 600,000 cubic meters, preferably less than 100,000 cubic meters, particularly preferably less than 15,000 cubic meters.

9. A method according to any one of the preceding claims, wherein the pressure vessels are arranged regularly side by side and/or one above the other in the dry bottom depression and/or wherein the pressure vessels are arranged in the dry bottom depression in such a way that a lower pressure vessel layer with regular arrangement of pressure vessels lying directly on the subsoil is formed, which layer is preferably suitable as a base for a second pressure vessel layer with regular arrangement lying above it, in such a way that the pressure vessels of the second pressure vessel layer can be stably arranged in recesses of the lower pressure vessel layer lying below it, and wherein a second pressure vessel layer is preferably arranged on the lower pressure vessel layer lying on the subsoil and a third pressure vessel layer is particularly preferably arranged thereon and further pressure vessel layers are optionally arranged thereon, wherein the pressure vessel layers are in turn each preferably suitable as a base for a respective pressure vessel layer lying thereabove.

10. Method according to one of the preceding claims, wherein the pressure vessels are arranged next to one another and/or one above the other in the dry bottom depression, preferably are arranged as lower, second and third pressure vessel layers, in such a way that free spaces remain between the pressure vessels which extend from above, preferably in a straight line and/or perpendicularly from above, to the subsoil, preferably through all layers, and preferably in such a way that the free spaces occur in a regularity defined by the arrangement of the pressure vessels, and/or 73 wherein one or more free spaces remaining between pressure vessels are designed as continuous upwardly, optionally upwardly projecting, shafts, and/or wherein the plurality of pressure vessels are arranged according to the structure of a densest, preferably hexagonally densest, sphere packing, preferably in that pressure vessels of the lower and optionally of the second pressure vessel layer are arranged according to the structure of a densest sphere packing and optionally the pressure vessels of the third pressure vessel layer are arranged according to the structure of a hexagonally densest sphere packing.

11. Method for converting a lower reservoir, which is set up for provisional use, preferably for test operation, and which is connected via a pressure line to a provisional upper reservoir, preferably according to one of claims 1 to 10, into an underwater pumped storage power plant, wherein a dry bottom depression in which the lower reservoir is arranged is flooded so that an artificially formed lake is created therein which forms a final upper reservoir for the underwater pumped storage power plant so that the underwater pumped storage power plant can be operated in such a way that electrical energy is generated when water is admitted from the flooded bottom depression into the lower reservoir and electrical energy is stored when water is pumped out of the lower reservoir into the flooded bottom depression.

12. A method according to claim 11, wherein during the flooding of the dry bottom depression, the lower reservoir is initially continued to be temporarily used or tested by admitting water from the temporary upper reservoir into the lower reservoir and/or pumping water from the lower reservoir into the upper reservoir.

13. The method of any one of claims 11 or 12, wherein during or after flooding of the dry bottom depression, the pressure line to the temporary upper reservoir is released.

14. A method according to any one of claims 11 to 13, wherein during or after flooding of the dry bottom depression, preferably after the pressure line to the temporary upper reservoir has been released, the temporary upper reservoir is transformed into a reclamation lake.

15. Preliminary pumped storage power plant comprising an at least partially constructed lower reservoir for an underwater pumped storage power plant, which is arranged in a dry but floodable bottom depression, preferably in an open pit mine, and which, when the dry bottom depression is flooded, is operable in such a way that electrical energy is generated when water is admitted from the flooded bottom depression into the lower reservoir and electrical energy is stored when water is pumped out of the lower reservoir into the flooded bottom depression, and a temporary upper reservoir located above the at least partially constructed lower reservoir, the upper reservoir being smaller than the dry bottom well, wherein the at least partially constructed lower reservoir is connected to the temporary upper reservoir via a pressure line so that the lower reservoir can be temporarily utilized in such a way that electrical energy is generated when water is admitted from the temporary upper reservoir into the lower reservoir and electrical energy is stored when water is pumped from the lower reservoir into the upper reservoir.