ES2540427A2 - Methods and apparatus for thermal energy storage control optimization - Google Patents

Abstract

Concentrating solar power (CSP) systems and methods are disclosed featuring the use of a solid-liquid phase change heat transfer material (HTM). The systems and methods include a solar receiver configured to receive concentrated solar flux to heat a quantity of the solid HTM and cause a portion of the solid HTM to melt to a liquid HTM. The systems and methods also include a heat exchanger in fluid communication with the solar receiver. The heat exchanger is configured to receive liquid HTM and provide for heat exchange between the liquid HTM and the working fluid of a power generation block. The heat exchanger further provides for the solidification of the liquid HTM. The systems and methods also include a material transport system providing for transportation of the solidified HTM from the heat exchanger to the solar receiver.

Description

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Material contains a phase change material that has a higher melting temperature than the phase change materials contained in other cubes of the cascade series.

Another embodiment is a solar power generation system as described in general above, but further comprising an input to one or more cubes selected from the thermal energy storage system in direct communication through a secondary branch of the circuit. heat transfer fluid with an outlet from a power block component. In addition, an output from the one or more selected cubes is in direct communication through the heat transfer fluid circuit with the solar energy concentrator or the power block. This configuration allows the heat transfer fluid flow to be preheated after at least one cube of the thermal energy storage system has been substantially discharged but before the thermal energy system is recharged. In this embodiment, the cubes of the thermal energy storage system in communication with the output of the power block can be cubes with a cooler temperature containing a phase change material having a lower melting temperature than the materials of phase change contained in at least one other cube of the cascading series.

A related embodiment includes a cascade thermal energy storage system as described generally above, but further comprising at least one secondary branch of the heat transfer fluid circuit that connects an output from the power block to the entrance to one or more cubes of the cascade thermal energy storage system.

A related embodiment includes a preheating method of a solar energy system comprising the step of flowing the heat transfer fluid from an output of the power block through one or more partially discharged cubes of the thermal energy storage system. before charging the thermal energy storage system. In this way, the process allows the heat transfer fluid to be preheated, which can then be flowed to the solar energy concentrator and the power block before the active energy generation begins.

An alternative embodiment includes solar power generation system as described generally above, but also comprising multiple branches.

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Charge the thermal energy storage system.

In the previous embodiment, the one or more cubes of the thermal energy storage system in communication with the output of the power block may be cubes with a cooler temperature containing a phase change material having a lower melting temperature than the phase change materials contained in other cubes of the cascading series.

A related embodiment includes a cascade thermal energy storage system as described generally above, but further comprising one or multiple secondary branches of the heat transfer fluid circuit that connect the power block to an inlet to one. or more cubes during periods of insufficient sunshine to load the thermal energy storage system.

A related embodiment is a method of utilizing solar energy which comprises the step of partially discharging the thermal energy storage system during periods of insolation too low to charge the thermal energy storage system by flowing the heat transfer fluid from the output of the power block through one or more cubes of the thermal energy storage system.

Another embodiment includes a solar power generation system such as the one generally described herein, comprising any combination of secondary branches of the heat transfer fluid circuit that extend between the selected phase change material cubes and / or any combination of secondary branches of the heat transfer fluid circuit that extend between the selected phase change material cubes and the solar field.

A related embodiment is a cascade thermal energy storage system as generally described above, further comprising any combination of secondary branches of the heat transfer fluid circuit that extend between the cubes of phase change material selected and the selected steam train components and / or any combination of secondary branches of the heat transfer fluid circuit that extend between the selected phase change material cubes and the solar field.

Brief description of the drawings

Fig. 1 is a schematic representation of a solar power generation system

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by concentration of the prior art that works in charge mode.

Fig. 2 is a schematic representation of a system for generating solar energy by concentration of the prior art operating in discharge mode.

Fig. 3 is a schematic representation of an improved system of generating solar energy by concentration that functions to produce energy.

Fig. 4 is a schematic representation of an improved system of generating solar energy by concentration during heating operations before loading and after discharge.

Fig. 5 is a schematic representation of an improved solar power generation system by concentration that operates in a discharge mode.

Fig. 6 is a schematic representation of an improved solar power generation system by concentration that operates in a partial discharge mode.

Fig. 7 is a schematic representation of a solar power generation system by concentration that presents a combination of improvements.

Detailed description

Unless otherwise indicated, all numbers that express quantities of ingredients, dimensions, reaction conditions, etc., used in the specification and the claims should be considered to be modified in all cases by the term "approximately" .

In the present application and in the claims, the use of the singular includes the plural, unless specifically indicated otherwise. In addition, the use of "or" means "and / or", unless otherwise indicated. In addition, the use of the expression "that includes", as well as other forms, such as "includes" and "included", is not limiting. In addition, terms such as "element" or "component" encompass both the elements and the components that constitute a unit and the elements and components that comprise more than one unit, unless specifically indicated otherwise.

A conventional solar power generation system 100 is illustrated schematically in Figs. 1 and 2. Various embodiments of solar-powered generation systems, which have improved thermal energy storage control procedures and apparatus, are described herein and illustrated.

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described as "charged" or fully charged. After leaving the cube 125 of colder phase change material, the then cooled heat transfer fluid can be routed back to the solar energy concentrator 102 to be reheated by solar energy.

A solar-powered power generation system 100 may be operated in charging mode at the discretion of the system operator, provided sufficient insolation is available to heat the heat transfer fluid flowing through the power concentrators 102 solar at a temperature high enough to melt the phase change material in each cube.

The thermal energy storage system 104 provides the system 100 with the ability to generate power for a period of time after the sun has set, or when the sun is hidden by a cloud cover. Here, when the solar power generation system 100 is operated without solar input, it is said that the system is operating in a "discharge" mode. The operation of the basic system in the discharge mode is schematically illustrated in Fig. 2. As shown in Fig. 2, the heat transfer fluid flowing in the heat transfer fluid circuit 108 flows through of the components 110 of the steam train in the same direction to achieve the same steam and energy production steps described above. However, in the discharge mode, the high temperature heat transfer fluid is obtained by flowing the flow of cooled heat transfer fluid in reverse order through the cascades of phase change material. In particular, the refrigerated heat transfer fluid is flowed through the bucket 126 of cold phase change material, the bucket 124 of intermediate temperature phase change material and the bucket 122 of hot phase change material, in that order. As the phase change material in each hub solidifies, heat is transferred to the heat transfer fluid. When all phase change materials in all the cubes have solidified, the thermal energy storage system can be described as fully "discharged" and, typically, it is inefficient or impossible to extract more sensible heat from the system for the generation of additional energy

As described above, day-to-day repeatability presents a significant difficulty in the operation of a thermal energy storage system, as shown in Figs. 1 and 2. In particular, the transient load response of the

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system is quite different from the transient download response. This becomes a problem when attempting to design a system such as that illustrated in Fig. 1 and Fig. 2 that will properly utilize the beneficial energy characteristics of the phase change in almost 100% of the phase change material provided.

Fig. 3 schematically illustrates an improved method and apparatus for optimizing the control of a thermal energy storage system 104 to improve transient performance. The improved process illustrated in Fig. 3 includes addressing part or all of the heat transfer fluid flow from the solar field through a cube of phase change material before the heat transfer fluid is addressed to power block 106. This re-addressing occurs during active energy production. In particular, part or all of the heat transfer fluid extracted from the outlet 130 of the solar field for a selected period of time can be routed through the hub 122 of hot phase change material before sending it to the power block. When this strategy is used, the hot hub 122 can be fully charged, even when the temperature difference that drives the load is much smaller than the temperature difference that drives the discharge. The implementation of the control improvement strategy illustrated in Fig. 1 requires at least one branch secondary to the heat transfer fluid circuit, for example, a tube 132 or other additional conduit and valves associated with the transfer fluid circuit. heat between an outlet from a hub, for example, the hot hub 122, and the inlet of the steam train 110, for example, before the super-heater element 118.

An alternative control enhancement method and apparatus is schematically illustrated in Fig. 4. This embodiment includes preheating system 100 in the morning or when the system is cold by a more complete discharge of one or more relatively more temperature cubes. cold, for example, the bucket 126. Because the melting temperatures of the one or more cold buckets are too low to sufficiently heat the heat transfer fluid to operate the power block after the bucket has been completely discharged 122 hot, typically, the thermal energy storage system 104 and the power block 106 should be turned off when there is still some latent energy available in the cooler buckets. This energy can be used to improve the overall performance of the plant by discharging it to preheat the solar field and power block 106 before the start of power generation operations.

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of the corresponding component of the steam train. For example, the melting temperature of the phase change material in a given hub may be approximately equal to the designed operating temperature of the corresponding component of the steam train.

As illustrated in Fig. 5, this embodiment can be implemented with one or more branches secondary to the heat transfer fluid circuit, for example, tubes 136 and 138 leading from the intermediate hubs to the corresponding components of the train of steam. In addition, secondary heat transfer fluid tubes 140 and 142 may be needed that lead from the steam train to the next hottest hub.

An alternative control improvement method and apparatus is schematically illustrated in Fig. 6. This embodiment performs a partial discharge of the thermal energy storage system 104 during periods of low sunshine. In this way, as the sun sets but still provides some light to the solar concentrators or as the clouds partially obscure the sun, the flow of heat transfer fluid from the solar field to the power block 106 is complemented by the Heat transfer fluid flow from the thermal energy storage system 104 to maintain the optimum flow rate of the power block. Because, typically, the cooler cubes in a thermal energy storage system 104 (for example, cubes 124 and 126) have excess energy stored compared to hot cube 122, it is possible to discharge cubes 124, 126 more cold first, while maintaining the full load in the hot bucket. In this way, this embodiment realizes a direction of the heat transfer fluid flow from the steam train outlet through one or two cold buckets to preheat it before sending it to the solar field for final solar heating at an operating temperature. The implementation of this improvement requires one or more branches secondary to the heat transfer fluid circuit, for example, the pipes 144 and 146, as shown in Fig. 6. The tube 144 leads from the outlet of the hub 124 to the entrance 128 of the solar field and the tube 146 leads from the exit of the hub 126 to the entrance 128 of the solar field.

Each of the embodiments for an improved control of the thermal storage system described above could be implemented individually, or in combination with other alternative embodiments. For example, Fig. 7 schematically illustrates a system 100 presenting each of the control improvements

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described herein in combination. The embodiment of Fig. 7 includes, but is not limited to, a solar power generation system or a thermal energy storage system, comprising the primary heat transfer fluid circuit of Figs. 1 and 2, in particular, element 108 of the heat transfer fluid circuit and various secondary branches of the heat transfer fluid circuit. The secondary branches of the heat transfer fluid circuit may be implemented in any combination and include, but are not limited to, tubes 132, 134, 136, 138, 140, 142, 144 and 146. The implementation of each improvement described herein any combination provides an operator of a system of

10 generation of solar energy by concentration a great flexibility on the management of the load and the unloading of a thermal energy storage system with cascade phase change material.

Various embodiments of the description could also include permutations of the various elements indicated in the claims, as if each claim

The preceding dependent was a multiple dependent claim incorporating the limitations of each of the preceding dependent claims, as well as the independent claims. Such permutations are expressly included within the scope of this description.

Although the embodiments described herein have been shown and described.

20 particularly with reference to a series of alternatives, people with knowledge in the field will understand that changes in form and details can be made to the various configurations described herein without departing from the spirit and scope of the description. The various embodiments described herein are not intended to act as limitations on the scope of the claims. All

25 references indicated herein are incorporated in their entirety, by reference.

Claims (1)

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