OA21970A - Method And Device For Water Purification. - Google Patents

Abstract

The present invention relates to a method and a device for purifying unpurified water such as seawater, wherein the water is heated so that it evaporates and the water vapour is condensed to obtain purified water, wherein the purified water is allowed to flow downward via a turbine (13), (24) that drives a generator (14), (25) in order to convert the potential gravitational energy thereof into electrical energy, wherein preferably water is pumped to a higher level (III) on a raised base (2) for energy storage as potential gravitational energy and water vapour is led to a higher level (III) and after condensation is captured at a higher level (III).

Description

METHOD AND DEV ICE FOR WATER PURIFICATION

The présent invention relates on the one hand to a method for purifying water with salts and/or contaminants dissolved therein, wherein a stream of unpurified water is supplicd and is heated so that the water evaporates at least partialiy and water vapour is obtained, and wherein at least a proportion of the water vapour is captured and is condensed to obtain purified water.

The présent invention also relates on the other hand to a device for water purification, comprising supplying means for supplyîng a stream of unpurified water with salts and/or contaminants dissolved therein, heating means for heating the water supplied and evaporating it at least partially so that water vapour is formed, and a condenser for condensing the water vapour to purified water.

In this patent application, purified water means water from which at least a proportion of the salts and/or contaminants présent in the unpurified water hâve been removed.

The présent invention relates to, among other things, a method and a device for water purification by a distillation process, wherein sait water, such as among other things seawater or brackish groundwater, is desalinated. In particular, the present invention relates to a method and a device for producing purified water that is suitable as drinking water and/or may be used for irrigation in agriculture or for making dry régions fertile or for use as industrial process water.

Among the existing methods of desalination, the distillation process is the simplest method. The water is evaporated and the dissolved substances therein, such as salts, remain behind and the water vapour is captured and condensed as purified water. However, this technique requires a considérable amount of energy. Application of solar energy for this is known. Another known desalination technology makes use of reverse osmosis. This method is more complex and because the water must be placed under a high pressure, the energy consomption is still very high. Among other things, owing to the low energy efficiency of the existing methods of desalination, their application is considered to be unattainable from the économie viewpoint in a good many régions of the world, so that problems of extreme drought and drinking water shortage hâve yet to be solved.

One aim of the present invention is to overcome these disadvantages by providing a method and a device for water purification that can be implemented with simple tcchnical means, which hâve a l

higher energy efficiency than the existing methods of desalination, and which make the production of clean water starting from unpurified water (e.g. such as seawater) feasible and economically attainable in more régions of the world.

This aim is achieved by providing a method for purifying water with the features stated in the first paragraph of this description, wherein, according to the présent invention, the purified water is allowed to flow downward (to a iower level) via a turbine that drives a generator, to convert the potential gravitational energy thereof into electrical energy.

In this way, the potential gravitational energy of the condensed water is used as an energy source that is available at any time and can be converted into electrical energy at a chosen time point. This electrical energy may for example be used for the operation of the device according to the invention and/or may be made available via an electricity grid for other consumers of electrical energy. A consumer of electrical energy means, in this patent application, any device or installation, apparatus, motor, etc., that uses electrical energy during its operation. The purified water that has flowed to a lower level may be made available, for example in a réservoir, to one or more customers of purified water. When purified water must be supplied at a time point when the consumers of electrical energy do not need ail the energy that is generated by the generator during the downward flow of the purified water, the excess electrical energy can be stored in a battery or in the fonn of potential gravitational energy for example by supplying unpurified water and moving it to a higher level.

The method according to the présent invention comprises in particular a system for production and distribution of purified water based on the purification of unpurified water combined with a system for production and distribution of electrical energy on the basis of energy stored as potential gravitational energy. The water purification preferably comprises water desalination and/or the stored energy is preferably obtained from a renewable energy source.

This unpurified water may then be purified further or for example be sold.

According to the présent invention, preferably at least a proportion of the water vapour is led to a higher level and after condensation is captured at a level that is higher than the level at which the water vapour was formed.

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The natural upward motion ofthc hot water vapour ensures that relativcly little energy is required for this movement of the water vapour, and that the increase in potcntial gravitational energy obtained thereby is always greater than the energy consumption for moving the water vapour to a higher level. This ineans that the thermal energy that we add during this method to evaporate the water also contributes partly to the buildup of potential gravitational energy.

According to a preferred method, the stream of unpurified water is moved from a first level to a higher level and during this movement is hcated so that the water evaporates at least partially and water vapour is obtained.

Moving the stream of unpurified water to a higher level provides energy storage in the form of potential gravitational energy. In this way, electrical energy can be stored temporarily when it cannot be used immediately. For example when energy is obtained from an intermittent renewable energy source, for example such as wind energy or solar energy, this energy can be stored temporarily in the form of potential gravitational energy. The water vapour that is obtained during this movement is then preferably also led to the second level so that the potential gravitational energy thereof increases.

Preferably, a proportion of the water will not evaporate during this upward movement and will arrive at the higher level as unpurified water and will be purified further there, for example by a distillation process or by application of another desalination method, so that after this condensation, an additional amount of purified water is obtained at this higher level. This additional amount of purified water thus increases not only the water production but also the available amount of potential gravitational energy.

According to a much preferred method, on an existing base, a bearing area is formed that is located higher than the base, and a condenser for condensing the water vapour is placed on the bearing area thus formed and the captured water vapour is led to the condenser. To form the bearing area, for example a building or any carrying structure can be erected on the base. Preferably, however, on the existing base, a raised base will be created by means of soil materials, for example such as earth or sand or stones or a mixture thereof, and the condenser is placed on the raised base thus formed. This raised base may take the form of a hîll.

According to another much preferred method, the heat energy that is rcleased during condensation ofthe water vapour is used at least partially for moving and/or heating the stream of unpurified water. This provides an additional increase in the energy efficiency of this method.

When carrying out this method, the unpurified water is preferably also evaporated in an évaporation space in which, above the water, an air pressure is provided that is lower than the atmospheric pressure, preferably at most 0.5 bar.

In this way, the boiling point of the water is low^rered and it can be distilled at a lower température. Therefore less thermal energy is required to evaporate the water. Thus, at a pressure of about 0.3 bar, the boiling point of water can be reduced to 70°C. The pressure in the évaporation space is preferably changed as a function of the availability of thermal energy for heating the water.

If for example the water is heated directly by solar energy, if relatively iittle solar energy is availabié, more energy may be used for crcating a low pressure in the évaporation space so that a lower pressure is created and thus less thermal energy is required, and conversely, if a lot of solar energy is available, less energy is used for creating a low pressure in the évaporation space so that a pressure that is less low is created and thus more thermal energy is required. This optimum between energy to lower the pressure in the évaporation space and thermal energy for évaporation may for example also be adjusted automatically during the process, on the basis of information about the available thermal energy. For lowering the pressure in the évaporation space, preferably electrical energy is also used, which is obtained by means of the turbine and the generator from the potential gravitational energy ofthe purified water. For this it is of course also possible to use electrical energy that is obtained from a renewable energy source, such as electricity obtained from solar energy by means of solar panels or from wind energy by means of wind turbines.

According to a more especially preferred method, at least for supplying and/or heating the stream of unpurified water, energy is used that is obtained from at least one renewable energy source, for example such as solar energy, wind energy, hydraulic energy, tidal energy, geothermal energy.

In a much preferred method, a combination of wind energy and solar energy is used, so that in the periods when one renewable energy source produces Iittle or no energy, the energy derived from the other renewable energy source is used so as to obtain greater continuity of the supply of renewable energy.

According to a very advantageous method, the generator is connected to one or more consumers of electrical cnergy, the purified water is collected in a container and the purified water is allowed to flow from the container to a lowcr level at a time point that is determined by an expected or indicated energy need of at least one of said consumers of electrical energy.

The generator may be connected for example via an electricity grid to a large group of consumers of electrical energy, which are provided for moving and/or heating the stream of unpurified water when using the method according to the présent invention. At a time point that is determined as a fonction of an expected or indicated energy need of one or more consumers of electrical energy, the potential gravitational energy of the condensed water is converted by means of the turbine and the generator into electrical energy and is made available to this or these consumer(s) of electrical energy. Determination of the time point of supply of the electrical energy takes place for example automatically. When electrical energy is supplied, the volume of purified water flowing downward is also available immediately for one or more customers of purified water, for example via a water tank that is connected to a network of water mains of a water distribution network.

The aim stated above is also achieved by providing a device with the features indicated in the second paragraph of this description, comprising a turbine that can be driven by a stream of water and a generator drivable by the turbine, and is envisaged to allow the water obtained in the condenser to flow via the turbine to a lower level in order to convert the gravitational energy thereof into electrical energy.

The potential gravitational energy of the condensed water is used as an energy source that is available at any moment and can be converted into electrical energy at any time point. The purified water that has flowed to a lower level may be made available, for example in a réservoir, to one or more customers of purified water. When purified water has to be supplied at a time point when the consumers of electrical energy do not need ail the energy that is generated during the downward flow of the purified water, the excess electrical energy may be stored in a battery or in the form of potential gravitational energy by moving unpurified water to a higher level.

The device according to the présent invention is in particular a device that on the one hand is provided for the production and distribution of purified water on the basis of unpurified water and on the other hand is also provided for the production and distribution of electrical energy on the basis of energy stored as potential gravitational energy. For water purification, the device preferably comprises a desalination plant. The device preferably comprises an energy conversion device to couvert the energy from a renewable energy source into electrical energy.

Further particular features of this device are presented in claims 11 to 28. The advantages of a number of these particular features are similar to or follow directly from the aforementioned advantages of corresponding features of the method according to the present invention and therefore are not always repeated hereunder.

In a preferred embodiment of this device, the stream of unpurified water is delivered to or made available at a first level, and is moved from this first level to a higher second level so that the gravitational energy thereof increases, and the device is provided for evaporating at least a proportion of the unpurified water at the second level by means of one or more thermal solar collectors, preferably making use of one or more mirrors or lenses.

An efficient embodiment of the device according to the present invention comprises guiding means, to guide at least a proportion of the water vapour, from the level at which the water vapour was formed, to a higher level and bring it into the condenser, and a condenser that is provided for capturing the condensation water at a level that is higher than the level at which the water vapour was formed.

As already pointed out above, the natural upward motion of the hot water vapour ensures that no or relatively little energy is required for this movement of the water vapour, and that the increase in potential gravitational energy generated thereby is always greater than the energy consumption for moving the water vapour to a higher level.

In this device, the stream of unpurified water is preferably delivered to or made available at a first level, and the device comprises displacing means for moving the unpurified water from this first level to a higher second level so that the gravitational energy thereof increases, and the device comprises heating means for heating at least a proportion of the unpurified water during this movement to the second level so that the water evaporates at least partially and water vapour is obtained.

Moving the stream of unpurified water to a higher level provides energy storage in the form of potential gravitational energy. In this way, electrical energy can be stored temporarîly when it cannot be used immediateiy. This is especially useful when energy is obtained from an intermittent renewable energy source. The water vapour that is obtained during this movement is then preferably also led to the second level so that the potential gravitational energy thereof also increases further.

Preferably, a proportion of the water will not evaporate during this upward movement and will arrive at the higher level as unpurified water and will be purified further there, for example by a distillation process or by application of another desalination method, so that after this condensation, an additional amount of purified water is obtained at this higher level. This additional amount of purified water thus increases not only the water production but also the available amount of potential gravitational energy that is stored in the form of purified water.

This device preferably comprises at least one évaporation space, is provided for bringing unpurified water into an évaporation space and evaporate it thercin, and comprises a vacuum generator that is provided for creating an air pressure in the évaporation space that is lower than the atmospheric pressure, which is preferably at most 0.5 bar.

In this way, the boiling point of the water is lowered and the water can be evaporated at a lower température. Therefore less thermal energy is required to evaporate the water. Thus, at a pressure of about 0,3 bar, the boiling point of water can be reduced to 70°C. The pressure in the évaporation space is preferably changed as a fnnction of the availability of thermal energy for heating the water.

In this device, the stream of unpurified water may be moved to a higher level with any pumping system, but an electrically driven pump, preferably a screw-type pump, more specifically a pipe conveyor, is preferred. The pipe conveyor then preferably comprises a screw-shaped body that is rotatable in a cylindrical tube and is configured so that the unpurified water, through rotation of the screw-shaped body, according to the principle of an Archimedes screw, is transported in the gaps between the screw blades and is moved upwards. Said movement of a liquid takes place without swirling and turbulence in the liquid. Much more efficient évaporation is obtained as a resuit.

In a very interesting embodiment, the device comprises a water channel for moving unpurified water by the action of the pump, the water channel extends from the first level to the second level, the device comprises heating means to heat the water présent in the water channel so that it evaporates at least partially, the device comprises an inclined water vapour channel that is in communication with the condenser and that is also in communication with the water channel so that water vapour that is formed in the water channel can move to the water vapour channel.

The angle of slope of the water vapour channel is preferably at most 45°, preferably between 10° and 40°, more preferably between 15° and 30°, most preferably between 15° and 25°. An angle of slope of about 20° provides optimal transport of water vapour to the condenser at the higher location.

When the water vapour channel and the water channel hâve an angle of slope as indicated in the previous paragraph, preferably an angle of slope of at most 45°, there is a rclatively large contact area between the surface of the liquid displaced in the pipe conveyor and the air located above that surface. Even quicker évaporation is obtained as a resuit. Therefore the desired évaporation of the water can be obtained over a relatively short distance and the water channel, and thus the whole pipe conveyor, may hâve a relatively small length and yet be very efficient.

In a particular embodiment, the water vapour channel is separated from the water channel by a partition wall over at least a part of the length of the water channel, preferably over almost the entire length of the water channel, and one or more openings are provided in the partition wall so that water vapour that has formed in the water channel can move to the water vapour channel via the opening(s). Said openings are preferably distributed uniformly over the entire length of the partition wall. At least one portion of the water vapour channel is preferably located above the water channel, so that the water vapour, rising following a straight path, can reach the water vapour channel via the opening(s) in the partition wall.

In a very advantageous embodiment of this device, a heat pipe is provided in the water channel and the device is provided for allowing a heated fluid, preferably a fluid heated by thermal solar energy, to flow through the heat pipe to heat the water présent in the water channel.

The device preferably also comprises a vacuum generator that is provided for creating an air pressure in the water channel that is lower than the atmospheric pressure, preferably is at most 0.5 bar. Owing to the reduced pressure, the température at which water vapour is formed can be lowered, so that the amount of thermal energy required can be reduced. The reduced pressure may for example be created by means of a vacuum pump, which is connected to one open end preferably the upper end - of the water channel. As a resuit, an air flow develops in the water channel from the other open end of the water channel to the end to which the vacuum pump is connected. This air flow over the water surface in the water channel causes even quicker and even more efficient évaporation of the water présent in the water channel.

In a much preferred embodiment ofthe device according to the présent invention, this comprises a raised bearing area formed on an existing base, which is located at a second level higher than the level ofthe base surface, a condenser placed on the bearing area for condensing the water vapour, and guiding means for leading the captured water vapour to the condenser and for bringing it into the condenser. On the existing base, for example a raised base may then be formed from one or more soil materials, such as earth or sand or stones, and said bearing area is provided on this raised base.

In a very energy-efficient embodiment, the device comprises means for transferring the heat energy that is released during condensation of the water vapour at least partially to the supplied unpurîfied water, for the heating thereof.

A very advantageous embodiment is obtained if the device comprises energy converting means for converting energy from one or more renewable energy sources, for example such as solar energy, wind energy, tidal energy and geothermal energy, into electrical energy and for using this energy for supplying and/or moving it to a higher level and/or heating the stream of unpurified water. In a most advantageous embodiment the device may also comprise one or more thermal solar collectors, preferably making use of one or more mirrors or lenses, in order to use the thermal solar energy from solar radiation directly to heat the stream of unpurified water. It is also further preferred to configure this device so that the generator is connected to one or more consumers of electrical energy, so that the device comprises a condensation water réservoir for collecting the purified water, a discharge orifice through which the water can flow out of the container and can flow via the turbine to a lower level, a closing device with an open State and a closed state for closing or opening said discharge orifice, and a control device that is provided for bringing, at a time point that is determincd as a function of an expected or indicated energy need of one or more consumers of electrical energy, the closing device from the closed State to the open State in order to allow purified water to flow from the container to a lower level and on the one hand produce electrical energy thereby and make it available to the consumer(s) and on the other hand also make purified water available to one or more customers of purified water.

The device for water purification according to the présent invention may for example also be provided for evaporating a proportion of the water during movement to the higher second level and supply it as water vapour to the condenser, and for evaporating at least part ofthe remaining unpurified water at the second level by means of one or more thermal solar collectors, preferably making use of one or more mirrors or lenses.

The device is then preferably also provided with a second turbine that can be driven by a stream of water, and a generator drivable by the second turbine, wherein the device is also provided with means to allow a remaining part ofthe unpurified water at the second level to flow via the second turbine to a lower level in order to couvert the gravitational energy thereof into electrical energy.

The invention is now explained in more detail on the basis of the following more detailed description of a possible embodiment of a device for desalination of unpurified water according to the présent invention.

It is emphasized that the device described hereunder is only one example of the general principle ofthe invention and so is not to be regarded in any way as a limitation ofthe scope of protection, or ofthe field of application of the invention. In this detailed description, reference is made to the appended drawings by means of reference numbers, where • Fig. I shows a schematic vertical cross-section of a first embodiment of a device for desalination of seawater according to the présent invention, and • Fig. 2 shows a schematic vertical cross-section of a second embodiment of a device for desalination of seawater according to the present invention.

It is emphasized that the drawings are only schematic and that various components and their dimensions are often not drawn to scale and are not shown with the correct relative proportions.

The device presented in Fig. I comprises a raised base (2) mounted on an existing base (l), hereinafter called hill or energy hill, which has a height (h) of about 20 métrés relative to the level (II) ofthe existing base ( l ), and at the top has a length of about 400 métrés and a width (b) of about 40 métrés. The figures show a cross-section according to the transverse direction of the hill (2). The hill has opposite sloping flanks (2a), (2b) and an upper surface that is roughly horizontal and has been made almost fiat and tonus a rectangular bearing area (3) about 400 métrés long and about 40 mètres wide. On this bearing area (3), five ofthe installations described hereunder for desalination of sait water are placed next to each other in the longitudinal direction of the hi11 (2). One of these installations is described in detail hereunder.

Near the hill (2), a large number of solar panels (4) are installed, the number and the capacity of which are coordinated with the energy requirement of the five desalination plants taken together. The hill (2) is located next to a sea (5), which contains sait water.

A sait water réservoir (6) is placed on the bearing area (3) of the hill. A pipe conveyor (7) is provided, which is drivable by means of an electric motor (8) to move seawater from level (I) of the water surface of the sea to the sait water réservoir (6) that is placed at level (III) of the bearing area (3) of the hill (2). The motor (8) of the pipe conveyor (7) is driven by electrical energy that is generated by means of the solar panels (4). The pipe conveyor (7) comprises a screw-shaped body, based on an Archimedes screw, which is rotatable in a cylindrical closed tube. This pipe conveyor (7) is supported by the sloping flank (2a) of the hill (2). With this pipe conveyor it is possible for example to raise 5000 litres of water per hour. We emphasize that any pumping system may be used to raise the seawater.

The sait water réservoir (6) is a closed space and the air pressure in this space is brought by means of a vacuum pump (9) to about 0.3 bar, so that the boiling point of the water is lowered to about 70°C. The lower the pressure, the lower is the boiling point.

The pressure in the sait water réservoir (6) is changed automatically as a function of the avaiiabiiity of thermal energy for heating the water. If the energy yield from the solar panels (4) is relatively high and exceeds a certain threshold value, the pressure can be kept relatively high so that less energy is used for lowering the pressure and more thermal energy is required for heating the seawater, but if the energy yield from the solar panels is relatively low and goes below a certain threshold value, a lower pressure is realized so that less thermal energy is required for heating the seawater. The pressure in the sait water réservoir (6) is adjusted automatically during the process on the basis of information about the available thermal energy. The vacuum pump opérâtes with electrical energy that is generated by the generator (14), but may of course also operate with electricity that is obtained from a renewable energy source.

The water in the sait water réservoir (6) is heated by means of a lens (9) placed above the water surface - shown schematically in Fig. I - which concentrâtes sunlight on the sait water réservoir (6) and its contents. In the vicinity of the hill, for example on the flanks of adjacent hills, in addition solar collectors are also installed (not shown in the figure), which concentrate the solar radiation by means of mirrors and/or lenses onto the walls of the sait water réservoir (6), so as to supply additional thermal energy.

As a resuit, the température of the seawater in the sait water réservoir (6) is increased until the boiling point is reached at the prevailing pressure. As a resuit, water vapour is formed, which is led to a condenser (10) and is brought into the condensation space of the condenser (10), where the water vapour is condensed by known techniques and is captured in a condensation water réservoir (11). During this condensation, heat is released, which by means of a heat exchanger and retum lines (not shown) is partly recovered and is used for heating the seawater in the sait water réservoir (6). A sait solution with a high concentration is left behind in the condensation water réservoir (11), and a layer of salty mud or sludge ( 17) is formed at the bottom. The condensation water that is captured m the condensation water réservoir ( 11 ) is suitable, optionally after further processing and/or addition of products, and after testîng, to be made available as drinking water.

At the moment when a need for electrical energy is expected or is indicated, a shut-off valve (12a) is opened automatically, by a control device that is not shown, to open the discharge orifice (12) of the condensation water réservoir (11) and allow the drinking water présent thereîn to be discharged via a discharge orifice (12). The discharge orifice (12) is connected to the inlet (13a) of a water turbine (13) that is provided for driving a generator (14) by the flowing water. This turbine is a so-called screw turbine (13) and comprises an elongated cylindrical tube in which a screw-shaped body is mounted rotatably and extends over almost the entire length of the cylindrical tube. The screw turbine (13) extends on a sloping flank (2b) of the hill (2), so that the inlet (13a) ofthe turbine (13) is located approximately at level (III) of the bearing area (3) of the hill (2) and the outlet ( 13b) is located approximately at level (II) of the existing base ( 1 ). After the shut-off valve (12a) is opened, the water flows through the screw turbine (13) and leaves this via the outlet ( 13b) and is captured in a drinking water tank (15). The potential gravitational energy of the drinking water at level (III) of the bearing area (3) is converted thereby into kinetic energy of the flowing water and this energy causes the rotation of the screw-shaped turbine body, which is then transferred to the generator (14), which converts this kinetic energy into electrical energy. The downward flowing drinking water has for example a flow rate of 5000 litres per hour.

Thus, a system for production and distribution of purified water on the basis of water desalination is combined with a system for production and distribution of electrical energy on the basis of energy stored as potential gravitational energy that is obtained from a renewable energy source.

In a second possible embodiment of a device for water purification according to the présent invention (Fig. 2), in the same way as in the first embodiment (Fig. i ), a raised base (2), called hill or energy hill hereinafter, is created on an existing base (1). The hill (2) has in this case a height (h) of about 30 métrés relative to the level (II) of the existing base ( 1 ), and at the top it has a length of about 500 métrés and a width (b) of about 50 métrés. The hill also has sloping flanks (2a), (2b) and at the top it has a rectangular, approximately fiat and horizontal bearing area (3), on which five of the installations described hereunder for desalination of sait water are also placed next to each other in the longitudinal direction of the hill (2). One of these installations is described in detail hereunder.

A large number of solar panels (4) and wind turbines (30), the number and the capacity of which is coordinated with the energy requirement of the five installations taken together, are installcd in the vicinity of the hill (2). The hill (2) is in this case also located near a sea (5) that contains sait water. On the bearing area (3) of the hill (2), there is a sait water réservoir (22) with a discharge orifice (22a) that is closable by means of a valve (22a 1 ) that can be placed in an open and a closed state, and a condenser (21 ) in which a condensation water reservoir is provided with an outlet (21 a) at the bottom. In this outlet (21 a), a valve (21 a 1 ) is provided, which may be placed in an open state and a closed state.

This second embodiment (Fig. 2) differs from the first (Fig. 1 ) in particular in that heating and évaporation of seawater now (also) take place during displacement of the seawater from the seawater level (I) to the higher level (III) of the bearing area (3) of the hill (2).

For this purpose, use is made of a conveying and heating device (20) with an inlet that is located just below the seawater level (I) and an outlet that extends approximately to level (III) of the bearing area (3) and is supported in an inclined position, for example with an angle of slope of about 20°, by a sloping flank (2a) of the hill (2).

The conveying and heating device (20) comprises an elongated cylindrical outer jacket (20a) in which, roughly concentrically relative to the outer jacket (20a), a pipe conveyor (20b, 20c, 20d) is placed. The pipe conveyor comprises a cylindrical tube (20b) in which an elongated body (20c) with a helical outer vane is mounted rotatably about a hollow shaft (20d) provided centrally in the cylindrieal tube (20b). The elongated body (20c) is rotatable by means of an electric motor (20h). Said helical outer vane is formed in such a way that through this rotation, a continuous movement of water can be achieved from one end of the pipe conveyor to the other end, according to the principle of an Archimedes screw. The space (20b 1 ) that is cnclosed by the tube (20b) of the pipe conveyor is used here as a water channel for conveying seaw'ater.

The diameter of the cylindrieal tube (20b) of the pipe conveyor is smaller than the diameter of said outer jacket (20a) so that a gap (20f) is formed between the outside wall of the tube (20b) of the pipe conveyor and the inside wall of the cylindrieal outer jacket (20a).

The hollow central shaft (20d) of the pipe conveyor is configured for being connected to a supply of a heated fluid, such as water or steam, derived from a device (3 1 ), (32) in which a fluid is heated to a high température by means of thermal solar energy, as is described hereunder. The heated fluid that flows through the hollow central shaft (23a) of the pipe conveyor is provided for heating the seawater while this is moved by means of the pipe conveyor to a higher level (III).

In the top (20g) of the cylindrieal tube (20b) of the pipe conveyor, perforations (20e) are provided, which are distributed uniformly over almost the entire length thereof. This top (20g) is a partition wall (20g) between on the one hand the space (20b 1) inside the tube (20b) of the pipe conveyor and on the other hand the gap (20f). The water vapour that is formed through heating of the seawater in the inner space (20b I) of the pipe conveyor can move via thèse perforations (20e) to the aforementioned gap (20f). The gap (20f) is connected to the condenser (21) that is placed on the hill (2). This gap (20f) is thus used as a water vapour channel for conveying the water vapour to the condenser (21 ). The condensation water is captured in the condensation water réservoir that is provided in the condenser (21 ).

Through this heating and évaporation in the inner space (20b 1) of the tube (20b) of the pipe conveyor, the water that leaves the pipe conveyor via the outlet opening at the top, is converted to sait water with a very high sait concentration. This sait water ends up in the sait water réservoir (22).

The conveying and heating device (20) has an inlet that is located under the seawater surface of the sea (5), via which the seawater can be taken up by the pipe conveyor and moved in the cylindrieal tube (20b) by the aforementioned outer vane. The seawater is heated by the hot fluid that flows through the hollow central shaft (20d) so that water vapour is formed, which moves via the perforations (20e) in the top of said tube to said gap (20f) between the tube (20b) ofthc pipe conveyor and the outer jacket (20a) of the conveying and heating device (20).

In order to lower the température at which the water evaporates, a vacuum pump (23) is connected via a connecting line to said gap (20f), which in its tum is also in communication via the perforations (20e) with the inner space (20b l) inside the tube (20b) of the pipe conveyor. Thus, both the gap (20f) and the inner space (20b l ) of the pipe conveyor are brought to a lower pressure, so that less thermal energy is required to evaporate the seawater.

The conveying and heating device (20) is preferably placed at an angle of slope of about 20° (although for practical reasons this is not shown as such in the drawings). This optimizes the hydraulic yield of the pipe conveyor and ensures that the evaporating water moves optimally upwards owing to the natural upward motion of the hot water vapour. The potential gravitational energy that is generated thereby thus does not require any additional energy for displacing this water vapour.

The electrical energy for operating this installation is generated by means of a combination of both soiar panels (4) and wind turbines (30). Through the combined use of two different renewable energy sources (soiar energy and wind energy), there are smaller variations in the energy yield, and on average there is a higher energy yield compared to a situation where we are dépendent on the yield from a single renewable energy source. The electrical energy thus generated is stored with high efficiency in the form of potential gravitational energy by moving seawater to a higher level (III). This electrical energy is also used for operating the vacuum pump (23).

For heat supply to this installation, a sait water tower (31 ) is provided, in which there is a large volume of sait water, and a so-called Concentrated Soiar Power installation or CSP installation, wherein soiar collectors (32) such as among other things mirrors and/or lenses are installed so that they concentrate the soiar radiation onto the walls of the tower (31 ), to heat the sait water therein. The sait water in the tower (31 ) is thus heated to a température of 90°C. Sufficient mirrors (32) are installed so that heated sait water can be obtained at a flow rate of 10 m³/s sait water with a température of 90°C. This seawater is used as a means for heating and evaporating seawater pumped in from the sea in the conveying and heating device (20). Before this, this heated sait water is allowed to flow through the hollow central shaft (20d) of the pipe conveyor in order to heat the seawater conveycd in this pipe conveyor to a température of at least 70°C. This is approximately the boiling point of the water when a vacuum of about 0.3 bar or less is created in this inner space by means of the vacuum pump. For heating the seawater to 70°C, we need heated sait water with a température of 90°C, to take account of heat losses and to ensure that the seawater moved by the pipe conveyor is heated to a température of at least 70°C over the largest possible portion of its path through the pipe conveyor.

As stated, the water vapour is fed via said gap (20f) to the condenser (21) on the hill (2) and the water vapour is condensed in the inner space of the condenser (21 ). During this condensation, heat is released, which in this case too is partly recovcred by means of a heat exchanger and retum lines (not shown) and is used for heating the seawater. The condensation water that is captured in the condensation water reservoir in the condenser (21) is suitable to be made available as drinking water, optionally after further processing and/or addition of products, and after testing.

Several such desalination plants may be placed next to each other on thc same hill, or several hills may be provided next to each other or in line. An identical CSP installation may be used for bringing seawater to high température in one or more towers, in order to provide several desalination plants with the necessary supply of heated sait water.

When a need for electrical energy is expeeted or indicated and at the same time we also want to or hâve to make drinking water available in a reservoir (28) provided for that purpose, which is placed on the base ( l ), then by opening the valve (21 al ) that closes the outlet (21a) of the condensation water reservoir, condensation water is allowed to flow via a first screw turbine (24), which drives a first generator (25), downward to level (II) of the base ( l ). As a resuit, on the one hand electrical energy is generated by the first generator (25), and on the other hand drinking water is also made available to one or more customers of drinking water, in the drinking water tank (28). When we only want to produce electrical energy, we can select allowing sait water to flow downwards via a second screw turbine (26), which drives a second generator (27). This is achieved by opening the valve (22a I ), which closes the discharge orifice (22a) of the sait water reservoir.

The two screw turbines (24), (26) used are manufactured by FishFlow Solutions NV. The first has a flow rate of 9 m³/s and a capacity of 3l20kW and the second has a flow rate of l m³/s and a capacity of 344kW. The sait water may then be desalinated further or used for other purposes.

Claims (29)

1. I. Method for purifying water with salts and/or contaminants dissolved therein, wherein a stream of unpurified water is supplicd and is heated so that the water evaporates at least partially and water vapour is obtained, and wherein at least a proportion ofthe water vapour is captured and is condensed to obtain purified water, characterized in that the purified water is allowcd to flow, via a turbine (13),(24), which drives a generator ( 14),(25), to a lower level (II), in order to couvert the potential gravitational energy thereof into electrical energy.
2. 2. Method for purifying water according to claim 1, characterized in that at least a proportion of the water vapour is led to a higher level (111) and after condensation is captured at a level (III) that is higher than the level at which the water vapour was formed.
3. 3. Method for purifying water according to claim 1 or 2, characterized in that the stream of unpurified water is moved from a first level (I) to a higher level (III) and during this movement is heated so that the water evaporates at least partially and water vapour is obtained.
4. 4. Method for purifying water according to one of the preceding claims, characterized in that on an existing base ( 1), a bearing area (3) is formed that is located higher than the base surface, and in that a condenser (21 ) for condensing the water vapour is placed on the bearing area (3) thus formed, and the captured water vapour is led to the condenser (21).
5. 5. Method for purifying water according to claim 3, characterized in that, on the existing base (1), a raised base (2) is created from one or more soil materials, such as earth or sand or stones, and in that said bearing area (3) is provided on the raised base (2).
6. 6. Method for purifying water according to one ofthe preceding claims, characterized in that the heat energy that is released during condensation of the water vapour is used at least partially for heating the stream of unpurified water.
7. 7. Method for purifying water according to one of the preceding claims, characterized in that the unpurified water is evaporated in an évaporation space (6), (20f, 20b 1 ) in which an air pressure that is lower than the atmospheric pressure, preferably at most 0.5 bar, is provided above the water.
8. 8. Method for purifying water according to one of the preceding daims, characterized in that, at least for supplying and/or heating the stream of unpurifîed water, energy is used that is obtained from a renewable energy source, for example such as solar energy, wind energy, tidal energy and geothermal energy.
9. 9. Method for purifying water according to one of the preceding daims, characterized in that the generator (14), (25) is connected to one or more consumers of dectrical energy, in that the purified water is collected in a container (11), and in that the water is allowed to flow from the container ( 11 ) to a lower level (I) at a time point that is determined as a fonction of an expected or indicated energy need of a consumer of dectrical energy, while purified water is also made available to one or more customers of purified water.
10. 10. Device for water purification, comprising supplying means (7), (20) for supplying a stream of unpurifîed water with salts and/or contaminants dissolved therein, heating means (16); (31), (32), (20d) to heat the water supplied and evaporatc it at least partially so that water vapour is formed, and a condenser (10), (21) for condensing the water vapour to purified water, characterized in that the device comprises a turbine ( 13); (24) which can be driven by a stream of water, and a generator (14); (25) drivable by the turbine (13); (24), and in that the device is configured to allow water obtained in the condenser ( 10); (21) to flow via the turbine (13); (24) to a lower level (11) in order to convert the gravitational energy thereof into dectrical energy.
11. 11. Device for water purification according to daim 10, characterized in that the stream of unpurifîed water is delivered to or is available at a first level (I), and is moved from this first level (1) to a higher second level (III) so that the gravitational energy thereof increases, and in that the device is configured to evaporate at least a proportion of the unpurifîed water on the second level (III) by means of one or more thermal solar collectors (16), preferably making use of one or more mirrors or lenses.
12. 12. Device for water purification according to daim 10 or 11, characterized in that the device comprises guiding means (20f) for guiding at least a proportion of the water vapour, from the level at which the water vapour was formed, to a higher level (III) and bring it into the condenser (21), and in that the condenser (21) is configured for capturing the condensation water at a level (111) that is higher than the level at which the water vapour was formed.
13. 13. Device for water purification according to one of daims 10 to 12, characterized in that the stream of unpurified water is delivered to or is available at a first level (1), in that the device comprises displacing means (20) for moving the unpurified water from this first level (I) to a higher second level (IiI) so that the gravitational energy thereof increases, and in that the device comprises heating means (31 ),(32), (20d) for heating at least a proportion of the unpurified water during this movement to the second level (III) so that the water evaporates at least partially and water vapour is obtained.
14. 14. Device for water purification according to one of daims 10 to 13, characterized in that the device comprises at least one évaporation space (6); (20b 1), (20f), in that the device is configured for bringing the unpurified water into an évaporation space (6); (20b 1), (20f) and evaporating it therein, and in that the device comprises a vacuum generator (9), (23) that is provided for creating an air pressure in the évaporation space (6); (20b 1), (20f) that is lower than the atmospheric pressure, and preferably is at most 0.5 bar.
15. 15. Device for water purification according to daim 14, characterized in that the stream of unpurified water is moved to the second level (111) by means of an electrically driven pump (7), preferably a screw-type pump, more specifically a pipe conveyor.
16. 16. Device for water purification according to one of daims 10 to 15, characterized in that the device comprises a water channel (20b I) for moving unpurified water by the action of the pump, in that the water channel (20b 1) extends from the first level (I) to the second level, in that the device comprises heating means (20d) for heating the water présent in the water channel (20b 1) so that it evaporates at least partially, in that the device comprises an inclined water vapour channel (20f) that is connected to the condenser (21 ) and that is also connected to the water channel (20b 1 ) so that water vapour that is formed in the water channel (20b 1) can move to the water vapour channel (20f).
17. 17. Device for water purification according to daim 16, characterized in that the water vapour channel (20f) is separated by a partition wall (20g) from the water channel (20b 1), over at least a part of the length of the water channel (20b 1 ), preferably over almost the entire length of the water channel (20b I ), and in that one or more openings (20e) are provided in the partition wall (20g) so that water vapour that is formed in the water channel (20b 1 ) can move via the opening(s) (20e) to the water vapour channel (20f).
18. 18. Device for water purification according to claim 16 or 17, characterized in that the openings (20e) arc distributed uniformly over the entire length of the partition wall (20g).
19. 19. Device for water purification according to one of daims 16 to l 8, characterized in that at least one portion of the water vapour channel (20f) is located above the water channel (20b l ).
20. 20. Device for water purification according to one of daims 16 to I9, characterized in that a heat pipe (20d) is provided in the water channel (20b l ) and in that the device is configured to allow a heated fluid, preferably a fluid heated by thermal solar energy, to flow through the heat pipe (20d) in order to heat water présent in the water channel (20b l ).
21. 21. Device for water purification according to one of daims 16 to 20, characterized in that the device comprises a vacuum generator (23) that is provided for creating an air pressure in the water vapour channel (20f) that is lower than the atmospheric pressure, and preferably is at most 0.5 bar.
22. 22. Device for water purification according to one of daims 10 to 21, characterized in that the device comprises a raised bearing area (3) formed on an existing base ( l ) that is located at a second level (III) higher than the level (II) of the base surface, a condenser ( 10) placed on the bearing area (3) for condensing the water vapour, and guiding means (20f) for leading the captured water vapour to the condenser ( 10) and for bringing it into the condenser.
23. 23. Device for water purification according to daim 22, characterized in that a raised base (2) is formed on the existing base ( l) from one or more soil materials, such as earth or sand or stones, and in that said bearing area (3) is provided on this raised base (2).
24. 24. Device for water purification according to one of daims 10 to 23, characterized in that the device comprises means for transferring the heat energy that is releascd during condensation of the water vapour at least partially to the unpurified water supplied, for the heating thereof.
25. 25. Device for water purification according to one of daims 10 to 24, characterized in that the device comprises energy converting means (4), (30) for converting energy from one or more renewable energy sources, for example such as solar energy, wind energy, tidal energy and geothermal energy, into electrical energy and use it for supplying and/or moving to a higher level and/or heating the stream of unpurified water.
26. 26. Device for water purification according to one of daims 10 to 25, characterized in that the device comprises one or more thermal solar collectors (32), preferably making use of one or more min-ors or lenses, in order to use the thermal solar energy from solar radiation directly to heat the stream of unpurified water.
27. 27. Device for water purification according to one of daims 10 to 26, characterized in that the generator (14) is connected to one or more consumers of electrical energy, in that the device comprises a condensation water réservoir (11) for coliecting the purified water, a discharge orifice ( 12) through which water can tlow away from the container and can flow via the turbine to a lower level (II), a closing device ( 12a) with an open State and a closed State for closing or opening said discharge orifice ( 12), and a control device that is provided for bringing the closing device ( 12) from the closed State to the open state, at a time point that is determincd as a function of an expected or indicated energy need of one or more consumers of electrical energy, in order to allow purified water to flow from the container (l l ) to a lower level (11) and moreovcr on the one hand to produce electrical energy and make it available to the consumer(s) and on the other hand also to make purified water available to one or more customers of purified water.
28. 28. Device for water purification according to one of daims 13 to 27, characterized in that the device is configured for evaporating a proportion of the water during movement to the higher second level (III) and feed it as water vapour into the condenser, and is configured to evaporate at least part of the remaining unpurified water on the second level (III) by means of one or more thermal solar collectors, preferably making use of one or more mirrors or lenses.
29. 29. Device for water purification according to one of daims 13 to 28, characterized in that the device comprises a second turbine (26) that is drivable by a stream of water, and a generator (27) drivable by the second turbine (26), and in that the device is configured to allow a remaining part of the unpurified water on the second level (III) to flow via the second turbine (26) to a lower level (II) in order to convert the gravitational energy thereof into electrical energy.