Solar thermal power generation system

Abstract

The solar thermal power generation system includes a thermal energy storage container containing a thermal mass composition capable of storing thermal energy, a solar energy collection system, and a power generation system. The collection system comprises a first closed-flow loop including a solar thermal collector that absorbs solar energy to heat a first working fluid. The heated first working fluid is recirculated through the first closed-flow loop to heat the thermal mass composition. The power generation system consists of a second closed-flow loop including a turbine generator. The second closed-flow loop recirculates the second working fluid through the thermal mass composition, absorbing thermal energy to heat the second working fluid, which is then fed to a turbine to generate electricity in the generator. The second working fluid is water / steam or a compressible gas. The thermal mass composition consists of a mixture of a phase-change material, such as a salt, and a metallic material.

Description

Technical Field

[0001] (Cross - reference to Related Applications) This application claims priority to U.S. Application No. 18 / 451,235, filed on August 17, 2023, and U.S. Provisional Application No. 63 / 507,467, filed on June 11, 2023, the entire contents of which are hereby incorporated by reference.

[0002] The present invention relates to a system for generating electricity, and more particularly, to a system that utilizes solar energy to heat a mass composition and generate steam for generating electricity by a Rankine cycle.

Background Art

[0003] The thermal energy reaching the Earth from the sun is extremely vast. However, it has been difficult to utilize it for useful purposes. For over 200 years, fossil fuels mined from the ground have been the mainstay of the energy supply necessary to support human civilization. Solar energy exists everywhere in the equatorial and subtropical regions of the Earth (between the lines of Cancer and Capricorn), and despite being visibly powerful, it received little attention until the second half of the 20th century when the relationship between the carbon released into the environment by the combustion of fossil fuels and the global climate breakdown became undeniable. Power generation by solar energy, which had rarely been the subject of scientific research for a long time, has now leaped into the central areas of academic and industrial research.

[0004] There is a need to improve renewable thermal energy systems that reduce dependence on fossil fuels, simultaneously reduce emissions of greenhouse gases that cause global warming, and store the solar thermal energy collected during the day for use whenever needed.

Summary of the Invention

[0005] Here, a renewable solar thermal power generation system is presented that replaces reliance on fossil fuels by efficiently capturing solar radiant thermal energy incident on a solar thermal collector and converting the captured heat into a useful form for generating electricity, high-enthalpy steam for process or district heating, or, as an example, portable hydrogen fuel, but not limited to these uses. In other embodiments, the captured solar heat can also be used to heat compressible gases, as described herein.

[0006] A solar thermal power generation system in one embodiment generally includes a solar energy collection system and a power generation system, which are operable and thermally coupled via an intermediate thermal energy storage system including a “green boiler,” which in one embodiment may be formed by a thermal energy storage (TES) container. The solar energy collection system recirculates a first heat transfer working fluid (hereinafter abbreviated as “first working fluid”) in a first closed flow loop between a solar thermal collector and a TES container, transferring the captured solar heat, i.e., thermal energy, to a thermal mass composition contained in a TES container that is operable to absorb heat. The power generation system may in one embodiment be a steam power generation system that recirculates a second heat transfer working fluid (hereinafter abbreviated as “second working fluid”), including water, through a second closed flow loop between the thermal energy storage container and a steam turbine generator set that is operable to generate electricity in a conventional manner. The turbine generator set (also abbreviated as turbine generator in the art) may form part of a Rankine steam power generation cycle. The first and second flow loops are fluidically separated from each other. The portions of the first and second closed flow loops located inside the TES vessel and extending through it are formed by respective bundles or banks of heat transfer tubes that transport the first and second working fluids through the thermal mass composition within the TES vessel. The TES vessel releases stored thermal energy as needed, heating the second working fluid to generate steam. The second working fluid (e.g., water) flows through the second closed flow loop that drives the power generation system (e.g., Rankine) cycle.

[0007] The first working fluid, heated by solar energy and circulating within the first closed-flow loop of the solar energy collection system, may be a molten salt, or in one embodiment, a eutectic salt mixture. Other suitable salts useful for capturing and transferring thermal energy can also be used. Suitable synthetic heat transfer oils can be used as alternative working materials or fluids instead of salts, such as DOWTHERM®, available from Dow Chemical Inc. Heat transfer oils are particularly useful for low-temperature applications, such as when the working fluid temperature is below 400 degrees Celsius. Therefore, for convenience of reference, the descriptions provided herein with respect to molten salts also apply to synthetic heat transfer oils.

[0008] The TES container of the thermal energy storage system can be a highly insulated container comprising first and second plurality of heat exchanger tubes, which are an integral component of the container and are advantageously supported by a single external housing that can be efficiently installed on a single concrete foundation at the installation site. This is in contrast to using multiple separate components, each having a separate housing and requiring separate foundations. Each of the first and second plurality of heat exchanger tubes is associated with each of the first and second closed flow loops, defining a plurality of heat exchangers that constitute its integrated fluid flow component. The first and second plurality of heat exchanger tubes are fluidly separated from each other within the TES container. Each heat exchanger comprises a tube bundle formed by heat exchanger tubes that are directly embedded in and conformally in contact with the thermal mass composition within the TES container, as further described herein. In short, the first group of heat exchangers, comprising heat exchanger tubes associated with the first closed flow loop of the solar energy collection system, transfers heat obtained from solar radiation to the thermal mass composition. A second group of heat exchangers, each comprising heat exchanger tubes associated with a second closed-flow loop of a steam power generation system, is configured in some embodiments to define a separate steam generator, capable of absorbing heat from a thermal mass composition and converting a second working fluid (e.g., water) into steam for driving a steam turbine.

[0009] Inside the TES vessel is a “captive” bed of thermal mass composition designed to absorb and store heat from an embedded heat exchanger tube, which circulates a first working fluid, heated by solar energy, through a bed via a first closed flow loop. Conversely, the bed supplies the stored thermal energy on demand to an embedded heat exchanger tube, which circulates a second working fluid (e.g., water) of the Rankine cycle, converting the liquid-phase water into steam to drive a steam turbine. The term “captive” as used above means that, in contrast to the first and second working fluids, the thermal mass composition remains stationary and does not flow into or out of the vessel.

[0010] In one non-limiting embodiment, the thermomass composition may include a mixture comprising a combination of a phase change material (PCM) and one or more other metallic materials, as further described herein, all of which have thermal absorption properties that function to absorb and retain heat over a period of time. Both the PCM and metallic materials in the mixture may be in the form of solid granular particles at room temperature when not heated by the thermomass composition. In one embodiment, the PCM material preferably has a lower melting point than the metallic material, so that the metallic material remains in a solid granular state, while the PCM material melts when first heated by a first working fluid (e.g., molten salt or heat transfer oil).

[0011] The TES container in a solar thermal power system allows for the storage of solar energy obtained from solar collectors during periods when sunlight is available. This enables the system to generate power simultaneously during these times to meet grid demand, or to generate power during periods when the sun is not shining, such as in the evening. This versatility makes it advantageous for solar thermal power systems to operate continuously as base-load units or intermittently as peak-load units.

[0012] In the case of peak load power generation, a TES vessel with a heat exchanger associated with a second working fluid is configured to function to boil the feedwater / feedwater to generate the high-pressure superheated steam required for the Rankine power generation cycle, and to generate power "on demand" whenever the power grid faces a power shortage to meet current load demand. Thus, when the power grid faces a power shortage, the solar thermal power generation system disclosed herein can function as a peak power generation unit to replace conventional small natural gas or diesel peak power generation units (often installed on the premises of large baseload fossil fuel power plants) that have traditionally been used as peak power during periods of electrical load fluctuations in the power grid.

[0013] As used herein, the term “closed flow loop” is defined as a fluid flow path in which a fluid can recirculate and flow within the loop, and does not exclude the inflow and outflow of various fluids into or from the flow loop.

[0014] It should be noted that the terms “first working fluid” and “second working fluid” as used herein may refer to different fluids in a claim, depending on the order in which the fluids are described in the claim. For example, in a claim, the first working fluid may refer to a working fluid related to a power generation system, while the second working fluid may refer to a working fluid related to a solar energy collection system. Therefore, these terms must be interpreted within the context in which they are discussed and presented.

[0015] According to one embodiment, a solar thermal power generation system comprises: a thermal energy storage container defining an internal space containing a thermal mass composition operable to store thermal energy; a solar energy collection system comprising a first closed-flow loop including a solar thermal collector configured to absorb solar energy and heat a first working fluid, wherein the first closed-flow loop is configured to circulate the heated first working fluid within the thermal energy storage container to heat the thermal mass composition; a power generation system comprising a second closed-flow loop including a turbine, wherein the second closed-flow loop is configured to circulate the second working fluid through the thermal energy storage container to absorb thermal energy from the thermal mass composition and heat the second working fluid for introduction into the turbine; and a generator operably connected to the turbine to generate electricity. In some embodiments, the first working fluid is a molten salt or a heat transfer oil, and the second working fluid is water that enters the thermal energy storage container in a liquid state and exits as vapor. In other embodiments, the second working fluid may be a gas such as carbon dioxide.

[0016] In another embodiment, a method for generating electricity using solar energy includes the steps of: preparing a thermal energy storage container containing a thermal mass composition having a formulation capable of storing thermal energy; heating a first working fluid using solar radiation; heating the thermal mass composition by flowing the heated first working fluid through it; flowing a second working fluid through it; heating the second working fluid by causing it to absorb heat from the thermal mass composition; and flowing the heated second working fluid through a turbine generator capable of operating to generate electricity. In some embodiments, the first working fluid is a molten salt or a heat transfer oil, and the second working fluid is water that enters the thermal energy storage container in a liquid state and exits as vapor. In other embodiments, the second working fluid may be a gas such as carbon dioxide. [Brief explanation of the drawing]

[0017] Exemplary embodiments of the present invention are described with reference to the following drawings, in which similar elements are denoted by the same symbols.

[0018] [Figure 1] This is a schematic diagram of a conventional Rankine power generation cycle system that uses fossil fuel boilers, which emit pollutants, to generate steam.

[0019] [Figure 2] This is a schematic flowchart of the solar thermal power generation system according to this disclosure, including a solar energy collection system, a power generation system, and a thermal energy storage system.

[0020] [Figure 3] This is a perspective view of one embodiment of a power tower for a concentrating solar thermal collector in a solar energy collection system.

[0021] [Figure 4] This is a perspective view of the thermal receiver in the power tower.

[0022] [Figure 5] It is a perspective view of a thermal energy storage (TES) container of a thermal energy storage system.

[0023] [Figure 6] It is a side sectional view thereof.

[0024] [Figure 7] It is an enlarged detailed view of the upper part of the TES container of FIG. 6.

[0025] [Figure 8] It is an enlarged detailed view of the lower part of the TES container of FIG. 6.

[0026] [Figure 9] It is a schematic flow diagram showing one heat exchanger of the TES container for explaining the circulation pattern of the heat transfer fluid of the power generation system.

[0027] [Figure 10] It is a schematic flow diagram of an alternative second embodiment of a solar energy collection system equipped with a heat transfer fluid preheater.

[0028] [Figure 11] It is a schematic flow diagram of an alternative embodiment of a solar power generation system incorporating an optional Goswami bottoming cycle.

[0029] [Figure 12] It is a schematic flow diagram of the Goswami bottoming cycle.

[0030] All drawings are schematic and not necessarily to scale. A part numbered in one drawing may be specifically labeled with a different part number and, for the sake of brevity, is considered the same part appearing in other unnumbered drawings unless otherwise specified herein. Integers referenced herein may include multiple symbols with different alphabetical suffixes for the same integer, but unless otherwise specified, they are interpreted as a general term for all symbols sharing the same integer. [Modes for carrying out the invention]

[0031] Features and advantages of the present invention are shown and described herein with reference to exemplary embodiments. This description of exemplary embodiments is intended to be read in conjunction with the accompanying drawings, which are considered to be part of the whole description. It is therefore clear that the disclosure should not be limited to exemplary embodiments showing several possible non-limiting combinations of features, which may exist individually or in combination with other features.

[0032] In the description of embodiments disclosed herein, references to directions or orientations are for illustrative purposes only and are not intended to limit the scope of the invention. Relative terms such as “downside,” “upside,” “horizontal,” “vertical,” “upwards,” “down,” “top,” “bottom,” and their derivatives (e.g., “horizontally,” “downwards,” “upwards,” etc.) should be interpreted as referring to the orientation being described at that time or the orientation shown in the drawings discussed. These relative terms are for illustrative purposes only and do not require the device to be constructed or operated in a particular direction. Terms such as “attached,” “fixed,” “connected,” “joined,” and “interconnected” refer to relationships in which structures are movable or fixed and fixed or indirectly fixed or attached to each other, either directly or indirectly through intervening structures, unless explicitly stated otherwise.

[0033] Throughout this specification, the scope disclosed herein is used in abbreviated form to describe all values ​​within that scope. Any value within the scope can be selected as the endpoint of the scope. Furthermore, all prior patent or patent application documents cited herein are incorporated herein by reference in their entirety. In the event of any conflict between the definitions of the cited documents and this disclosure, this disclosure shall prevail.

[0034] Figure 1 shows a conventional Rankine steam power generation cycle with a large fossil fuel boiler that generates the steam necessary for power generation. The basic cycle equipment (excluding auxiliary systems) includes a fossil fuel boiler (coal, oil, natural gas, etc.), a steam turbine generator set, a steam condenser that condenses the steam discharged from the steam turbine back into a liquid, and a boiler feedwater pump that takes steam from the condenser and circulates it as boiler feedwater (heat transfer fluid) through a closed flow loop formed by piping that fluidly connects the components, as shown in the figure. The generator is mechanically coupled to the steam turbine and electrically connected to the power grid (represented by the power transmission towers shown). The steam generated in the boiler rotates the turbine shaft via a row of turbine blades, and then rotates the rotor of the generator in the stator (magnet), converting mechanical energy into electrical energy in known ways. The Rankine cycle power generation system and the operation of its power generation are well known to those skilled in the art and do not need further explanation.

[0035] While Rankine systems fossil fuel boilers convert liquid boiler feedwater into high-pressure steam, such boilers and their associated auxiliary equipment cannot be started up immediately for on-demand power generation and are therefore traditionally used for base load operation to meet the base load demands of the power grid. In fact, the entire start-up process for fossil fuel baseload power plants takes many hours to raise all equipment and systems to operating conditions of maximum pressure and maximum temperature and reach maximum load.

[0036] Figure 2 is a schematic system flow diagram showing a solar thermal power generation system 300 according to one embodiment of the present invention. Part of the system may include a Rankine steam power generation cycle, which captures solar thermal energy instead of fossil fuels to obtain input energy and generates steam necessary for power generation.

[0037] In one embodiment, the solar thermal power generation system 300 generally comprises a solar energy collection system 310 including a photovoltaic collector 312, a power generation system 340 including a steam turbine 341 and a generator 342, and a thermal energy storage system 100 that is operably and thermally coupled to these systems 310 and 340. However, systems 310 and 340 are fluidly separated from each other. As further described herein, the intermediary thermal energy storage system 100 comprises a “green boiler” 120, which in one embodiment can be formed by a thermal energy storage (TES) vessel 130 containing a thermal mass composition M specially configured to operate such as absorbing thermal energy and, if necessary, generating steam to drive the power generation system 130.

[0038] The solar energy collection system 310 is configured to circulate a first heat transfer working fluid (hereinafter, "first working fluid") within a first closed flow loop 311 between a solar thermal collector 312 and a TES container 130, and the solar heat, i.e., thermal energy, captured from the collector is used to heat a thermal mass composition M contained in the TES container. A flow path 318 forms an integrated outer portion of the first flow loop 311 and circulates the first working fluid between the solar thermal collector 312 and the TES container 130. In one embodiment, the flow path 318 can be formed by piping made of a material suitable for handling the temperature, pressure, and chemical properties of the first working fluid. In some embodiments, the flow path is insulated and, if necessary, can be heat traced to minimize heat loss from the first working fluid. The first closed flow loop 311 includes at least one recirculation pump 319 that provides the power to recirculate the first working fluid through the first closed flow loop. As shown in Figure 2, the pump 319 can be located in the first closed flow loop 311, upstream of the power tower 316 and downstream of the TES vessel 130.

[0039] As previously stated herein, in some embodiments the first working fluid may be a molten salt or a heat transfer oil. However, other suitable heat transfer working fluids may also be used, if appropriate.

[0040] In one embodiment, the solar collector 312 may be a concentrated solar power (CSP) collector comprising a circular array of heliostats 313 surrounding a centrally located power tower 316 (for simplicity, only one heliostat is shown in Figure 2). Heliostats are commercially available from several suppliers in various sizes and curvatures. The power tower 316 receives thermal energy supplied from the heliostats. Each heliostat 313 typically includes a support frame 314, which is mounted to the ground (or another available support surface), and an adjustable reflector 315 configured to capture and reflect incident solar radiation or light. In one embodiment, each reflector may be formed by a concave mirror with a radius of curvature set to concentrate the solar energy incident on its surface onto a heat receiver 317 mounted on top of a tall cylindrical power tower. This solar radiant energy (heat) is collected by a concave mirror mounted on a drive mechanism, which causes the mirror to perform an indexing motion to continuously orient itself towards the sun as it crosses the sky throughout the day, optimizing the amount of solar radiation captured. Receivers can be positioned at multiple heights within a sufficiently tall power tower 316, thereby enabling more efficient capture of solar radiant thermal energy from a wide heliostat field. Receiver 317 is an integrated fluid component of the first closed loop 311, which transfers the thermal energy received from the sun to the TES vessel 130, which acts as an intermediary with the power generation system 340. Receiver 317 is a heat exchanger with heat exchanger tubes, as further described herein, which serves as the inlet for the thermal energy input to the solar energy collection system, heating the recirculating first working fluid to a desired target temperature.

[0041] The CSP system disclosed herein can utilize an optimization algorithm that maximizes the total amount of sunlight irradiated onto an array of heliostats on a given plot of land. This optimization takes into account the plot size and latitude of the plant's location. The size and spacing of the heliostats are modifiable parameters to achieve a configuration that maximizes solar energy capture. Calculations suggest that in the region between the lines of Capricorn and Cancer, a daily energy capture density (ECD) of up to 5 MWh per acre (4047 square meters) of land planted with heliostats can be achieved. In warmer regions of the Earth, the ECD may be as low as approximately 4 MWh per acre (4047 square meters).

[0042] Figures 3 and 4 show further details and features of the power tower 316 and the heat receiver 317. The power tower 316 includes a vertically elongated structural support tube 321, which is configured to be attached to the ground, such as a suitable concrete foundation F, to which the tube is bolted or otherwise secured. The support tube may be cylindrical with a circular cross-sectional shape in one embodiment, as shown, but other suitable shapes, including various polygons, are also available. At least a portion of the interior 321a of the support tube 312 can be hollow, thereby providing a path for the “cold leg” fluid riser tube 322 and the “hot leg” fluid downcomer tube 323 to run inside the support tube and between them and the multiple heat receivers 317 mounted on the top of the support tube. The internal routing of the risers and downcomers within the support tube 321 has the advantage of mitigating the effects of heat dissipation sources such as wind and rain. The riser tube 322 and downcomer tube 323 are insulated, heat-traceable as needed, and fluid-coupled directly or indirectly to each receiver 317. In some embodiments, a suitable piping manifold (not shown), such as a circular one, can be used to distribute the cold first working fluid to each receiver and then collect the heated first working fluid from the receivers.

[0043] The terms "cold leg" and "hot leg" refer to the relative temperature when the first working fluid (e.g., molten salt or heat transfer oil) enters the solar thermal collector 312 after releasing heat to the thermal mass composition M within the TES container 130 (cold leg), and the relative temperature before the fluid releases the heat obtained from the solar thermal collector 312 to the thermal mass composition, respectively.

[0044] The prismatic power tower structure allows for the construction of very tall columns, enabling the installation and operation of multiple rows of thermal receivers. The cylindrical cross-section of the power tower allows for the installation of multiple thermal receivers 317 in a circular direction, thereby ensuring that solar radiant energy is adequately captured in locations where its orbit in the sky is suitable for such a project. In some embodiments, radiant solar energy can be captured even more efficiently from the large array of heliostats 313 by arranging the receivers 317 at multiple heights within a sufficiently tall power tower 316.

[0045] In one embodiment, the recirculation pump 319 can be located in a first closed flow loop 311 upstream of the riser tube, near its bottom, as shown in Figure 2. While this configuration is acceptable, the recirculation pump is disadvantageous because it operates against the hydrostatic pressure difference, i.e., the head, due to the density difference between the high-temperature and low-temperature first working fluid columns (such as molten salt columns, if used) in the riser tube and downcomer tube. This increases the horsepower requirements and energy consumption of the pump motor.

[0046] Figure 10 discloses an enhanced first closed flow loop 311' configured and designed to mitigate the effects of the aforementioned pressure difference and reduce energy consumption for delivering the cold first working fluid to the top of the power tower 316 and reaching the heat receiver 317. As shown in this figure, a portion of the hot first working fluid heated and discharged by the power tower receiver 317 (only one is shown in this figure for brevity and clarity) is extracted and flows through a bypass piping loop 324 to a preheater 325. The preheater 325 is used to preheat the cold first working fluid returning from the TES vessel 130 and entering the tower after entering the riser tube 322. In one embodiment, the preheater 325 is a heat exchanger that can be located inside the support tube 321, but in other embodiments, the heat exchanger can be located outside the support tube.

[0047] In one non-limiting configuration, the preheater 325 is a shell-and-tube heat exchanger well known in the art, and its shell 322a houses an array of first heat exchanger tubes 324a fluid-coupled to a tube-side bypass piping loop 324 that forms a high-temperature side heat transfer medium. The cold or cooled first working fluid in the riser tube 322 flows through the shell-side heat exchanger, which is in contact with the outside of the tubes 324a that form the cold side heat transfer medium. This flow arrangement may be reversed in other embodiments. The heat exchanger is counterflow in some embodiments, as shown, but a parallel flow design may also be used in some cases. It is advantageous that the cold first working fluid in the riser is heated in the preheater 325 and enters each heat receiver 317 partially heated before reaching the heat receivers 317. In this way, the temperature difference of the first working fluid column in the riser tube and downcomer tube (e.g., a molten salt column when used as the first working fluid) is reduced, and the resulting hydrostatic pressure difference is mitigated. This enhanced flow recirculation loop is particularly effective when using synthetic heat transfer oils such as DOWTHERM® as the heat transfer fluid. Other types of heat exchangers can also be used. It should be noted that the heat exchanger 325 and the bypass piping loop 324 form an integrated fluid section of the first closed flow loop 311.

[0048] In other embodiments, the preheater may be configured as a double-tube heat exchanger (e.g., a pipe within a pipe).

[0049] Referring to Figures 3 and 4, the multiple heat receivers 317 forming the integrated fluid section of the first closed flow loop 311 each comprise multiple heat exchanger tubes 326 fluid-coupled between an upper outlet header 327 and a bottom inlet header 328. The first working fluid flows through the receivers between the headers and through the tube-side interior of the tubes 326. The inner surface of the half-tubes may be given a conical fine-roughness pattern to enhance heat transfer between the tube surface and the fluid flowing inside the tubes. The headers can be configured, if necessary, to form multipath first working fluid passages through the tube bundles, providing the required amount of heating to the first working fluid.

[0050] In one embodiment, the heat exchanger tubes 326 of each receiver may be arranged in a tube wall that includes a pair of end tube walls 329 angled to each other and an intermediate tube wall 330 located between them and angled to the end tube walls. This arrangement gives each receiver 317 a nearly (but not perfectly) C-shaped structure that forms an outward-opening cavity as shown in the figure, in order to reduce heat loss from the receiver to the surrounding environment.

[0051] Therefore, in one embodiment, each heat receiver 317 is a curved structure that mimics a plate heat exchanger. In one embodiment, the heat transfer surface that absorbs solar radiation can be made of a corrugated profile metal sheet welded to a thick flat plate with an insulated back surface. Each corrugated portion of the sheet functions as an autonomous heat transfer space that forms a heat exchanger tube 326 having a cross-section approximating a half-tube tube (such as a semicircle). A first working fluid flows inside the “half-tube” and absorbs solar radiation heat stored on its outward-facing surface by the heliostat 313. The surface of the receiver tube facing the heliostat may be coated with a material that has high absorptivity in the solar wavelength range and low emissivity in the infrared wavelength range. The receivers 317 may be arranged in a circumferential array adjacent to one another to receive the solar energy radiation (i.e., light) flux reflected and focused from the heliostat across the entire 360 ​​degrees of the solar field in the low-latitude regions of the world. At high latitudes, the receiver is designed to receive concentrated radiant flux from the north side of the tower in the Northern Hemisphere and from the south side of the tower in the Southern Hemisphere. Therefore, various variations are possible to adjust to the conditions and location of the solar thermal power site and maximize its potential.

[0052] The power tower 316 may further include an expansion tank 320 positioned above the thermal receiver 317 to accommodate the temperature-dependent density changes of the first working fluid. In one non-limiting embodiment, the expansion tank 320 may be fluidically coupled to each receiver at a suitable fluid connection point, such as an upper header (see, for example, the dashed line in Figure 3). Other suitable fluid connection locations with the receivers may also be used.

[0053] Referring to Figure 2, the power generation system 340 of the solar thermal power generation system 300 is a steam power generation system and generally includes, but is not limited to, a conventional steam turbine generator set including a steam turbine 102, a generator 103 mechanically coupled thereto and operably connected to the power grid, a steam condenser 105 that condenses steam into condensate, and a boiler feedwater pump 106. These components (except the generator, of course) together with the heat exchange section of the green boiler 120 (TES vessel 130) form an integrated fluid section of a second closed flow loop 341, which carries a second working fluid to absorb heat from the thermal mass composition M and drive the steam turbine generator set to generate electricity. The generator generates electricity in a conventional manner via a stator and rotor assembly well known in the art. The feedwater pump 106 circulates boiler feedwater through the second closed flow loop 341, which is partially formed by a flow path 319 such as piping that fluidly connects the Rankine cycle and the water holding section of the TES vessel, as shown in the figure. Aside from this green boiler, the remaining plant components of the clean energy Rankine cycle necessary to form a complete power generation system are supplied in the same well-known manner as conventional Rankine cycle components and can operate and generate electricity.

[0054] Notably, the TES vessel 130 can generate steam at a maximum pressure of approximately 3000 psi (20.68 MPa) to meet a variety of steam power generation needs and applications.

[0055] Referring to Figures 2 and 5, the thermal energy storage system 100 includes the green boiler 120 described herein, which comprises a highly insulated TES vessel 130. The vessel 130 includes a first plurality of fluidly separated heat exchanger tubes and a second plurality of heat exchanger tubes that form a heat exchanger, which is a part incorporated into the vessel. The first plurality of heat exchanger tubes 331 is an integrated fluid part of a first closed flow loop 311 associated with the solar energy collection system 310. The second plurality of heat exchanger tubes 211 is an integrated fluid part of a second closed flow loop 341 associated with the power generation system 340. The heat exchanger tubes will be described in more detail after an overview of the structure of the TES vessel.

[0056] The TES container 130 has a vertically elongated and oriented structure, and in one embodiment, it may have a generally box-shaped body and structure. For example, the TES container 130 may have a rectangular cuboid configuration, as shown in the non-limiting embodiment shown. Other shapes of containers can also be used, including, but are not limited to, hexagonal, cylindrical, and the like. The shape of the container does not limit the concepts or inventions disclosed herein.

[0057] The TES container 130 defines a vertical centerline axis CA that passes through the geometric center of the container. This axis defines a reference point that facilitates the description of the other components of the container and the relative orientation of the components to each other.

[0058] A TES vessel typically comprises an outer housing 134 defining a top 131, a bottom 132, and a plurality of vertical side walls 133 extending between the top and bottom along axis CA. The side walls are flat and, in one embodiment, are formed by a plurality of suitable metal side plates 133-1 (e.g., steel or aluminum) attached to a steel framework for the internal structure (not shown to illustrate the internal components of the vessel in operation). Four side walls 133 are provided, each side wall perpendicular to the adjacent side wall that intersects at a 90-degree angle 133-2. The internal structural framework consists of appropriately vertical, horizontal, and angled structural steel members and braces as needed to support the vessel and its attachments.

[0059] The TES container 130 further comprises a structural support base 138 positioned on the bottom 132 of the container housing 134. The mounting base 138 is a substantially horizontal, wide, linear structure configured to be positioned and fixed onto a flat support structure such as a concrete foundation F slab. In one embodiment, the base can be fixed to the slab using a number of threaded fasteners or anchors (not shown) that can be inserted into holes provided in gusset mounting plates 138-1 on all four sides of the base. The mounting base 138 is formed by welding and / or bolting together horizontal and vertical flat metal plates of moderate strength and structural members such as steel of appropriate thickness, forming the illustrated mounting base configuration in a manner that supports the entire weight of the TES container from the foundation slab and stably fixes the container to resist crosswind loads.

[0060] The TES vessel 130 further comprises a substantially flat horizontal upper closure plate 136 at the top 131 of the vessel and a substantially flat horizontal lower closure plate 137 at the bottom 132 of the vessel. The plates 136 and 137 are formed of a suitable thickness of metal, such as steel. The upper and lower closure plates are arranged parallel to each other and perpendicular to the vessel's central axis CA. Both plates extend sufficiently from end to end between the vessel 130 and the outer housing 134, as shown in the figure. Thus, the upper closure plate 136 and the lower closure plate 137 can each have a substantially linear (i.e., square or rectangular) shape, in contrast to the cylindrical structure of the upper header 201 and lower header 203 associated with the power generation system 340, as will be further described herein. The lower closure plate 137 is fixedly coupled and supported to the aforementioned vessel's support base 138.

[0061] The TES container 130 (e.g., housing 134) defines an open, continuous vertical internal space, or cavity 135, which extends vertically along the central axis CA between the horizontal upper closure plate 136 and the lower closure plate 137, and laterally / horizontally between the four side walls 133 (i.e., side plates 133-1) of the TES container housing 134. Thus, in the illustrated embodiment, the cavity 135 extends over at least a large portion of the height of the container housing 134, substantially the entire height (excluding the thickness of the upper and lower closure plates of the housing).

[0062] The internal cavity 135 of the TES vessel 130 is filled with an operational thermal mass composition M (further described herein) designed to absorb and retain heat from a heater embedded in the material. The thermal mass composition is contained "confined" within the vessel 130 so that no material flows into or out of the TES vessel 130 during operation of the green boiler 120. As further described herein, only the heat transfer fluids on the tubular side (i.e., the first and second working fluids) flow through the vessel.

[0063] First, a second set of heat exchanger tubes 211 associated with the power generation system 340 are described, extending through the thermal mass composition M within the cavity 135 of the TES container 130. The tubes 211 receive a second working fluid, which is water in a liquid state at the bottom, and exit the tubes as vapor at the bottom. Thus, the water is heated by the thermal mass composition and changes phase as it rises through the tubes.

[0064] In one non-limiting embodiment, the heat exchanger tubes 211 may be organized into several individual heat exchangers 200 of the TES vessel 130 and directly integrated into the vessel housing 134, forming a single green boiler unit. Advantageously, this provides a modular boiler unit that occupies less space at installation and is easily shipped / transported as a single unit that can be manufactured in the factory, including all internal piping and tubing connections (e.g., welded, flanged / bolted, screwed, etc.). This improves reliability and reduces installation time at the installation site. Thus, the single-unit structure of the green boiler 120 differs from physically separate, individual thermal storage vessels and heat exchangers that need to be assembled and piped at the site.

[0065] Referring to Figures 2 and 5-9, in one embodiment, one heat exchanger 200 can be placed in each of the four quadrants (viewed from above) of the thermal energy storage vessel to form four fluid heating zones for heating water to steam. As will be further described herein, the heat exchangers 200 are fluidically separable from one another within the TES vessel 130 to form individual fluid heating passages, so that each heating zone can operate independently of one another to heat and boil the second working fluid (i.e., water). This has the advantage of providing considerable operational flexibility, as in various situations only some of the heat exchangers may be needed to supply the steam necessary to power the steam turbine 102 and generate electricity to meet the power demands of the power grid.

[0066] Each of the second working fluid heat exchangers 200 generally comprises an upper channel, or header 201, including an upper tube sheet 202, and a lower channel, or header 203, including a lower tube sheet 204. The upper header 201 is located at the top 131 of the TES vessel 130, and the lower header 203 is located at the bottom 132 of the vessel. Each tube sheet 202, 204 may be circular in one embodiment.

[0067] Each heat exchanger 200 further comprises a tube bundle 210 including a plurality of elongated heat exchanger tubes 211 extending vertically between the upper tube sheet 202 and the lower tube sheet 204. The tubes 211 may be straight, linear tubes in one embodiment, as shown in the illustration. The tube sheets are of a relatively thick construction, for example, about 4 inches (10.16 centimeters) thick in one embodiment. The upper ends of the tubes are sealed and joined to the upper sheet 202 by circumferential seal welding. It should be noted that the tubes 211 pass through complementaryly configured holes in the upper plate 136, but are not fixedly attached therein, but are slidable relative to the upper plate.

[0068] Similar to the vanes of the upper tube sheet 202, the lower end of the tube 211 is fixed to the bottom tube sheet 204 in the same manner and sealed with a seal weld. The tube 211 extends completely through the upper and lower tube sheets within complementaryly configured through-holes 211-1 (see, for example, Figure 8 showing the interface between the lower tube sheet and the tube). Similar structures with through-holes are also used for the upper end of the tubes and the upper tube sheet 202. This allows each heat exchanger tube 211 to fluidically communicate with both the upper header 201 and the lower header 203, through which the heat exchange transfer fluid flows (see, for example, Figure 9 showing the circulation pattern of the second working fluid on the tube side through the TES container 130, indicated by flow arrows).

[0069] The upper header 201 defines an open internal space that forms the upper flow plenum 201-1 of the heat exchanger. Similarly, the bottom header 203 defines an open internal space that forms the bottom flow plenum 203-1. The second working fluid (e.g., water) flows through the tubes 211 of the tube bundle 210, tube-side. The bottom flow plenum 203-1 receives the second working fluid in a cooled liquid state and distributes it to the bottom inlet of each tube 211 in the tube bundle 210. Similarly, the top flow plenum 201-1 receives and collects the second working fluid, which is heated by the thermal mass composition M in the TES container 130, converted from liquid to vapor, and enters the container, from the upper outlet of each tube 211. Thus, as shown in the flow diagram of Figure 9, the flow of the heat transfer fluid in the tubes 211 in this embodiment is vertically upward from the bottom header 203 to the upper header 201 within the container.

[0070] The heat exchanger tubes 211 are embedded in a thermal mass composition M that fills the gaps or voids between the tubes in the tube bundle 210, and the thermal mass composition is in direct conformal contact with the outer surface of the tubes to achieve optimal heat transfer. The thermal mass composition M will be described further herein.

[0071] In one non-limiting embodiment, the upper header 201 and lower header 203 may comprise a generally tubular, hollow cylindrical metal body structure formed by vertically arranged annular shells 201-3 and 203-3, respectively. The shells define vertical sides extending circumferentially from the header, as shown in the figure. The shell 203-3 of the bottom header 203 extends vertically and is welded and sandwiched between the upper part of the bottom tube sheet 204 and the bottom of the bottom closure plate 137 of the TES container housing 134. Thus, the upper and lower ends of the shell 203-3 are seal-welded to the bottom tube sheet and bottom closure plate of the housing, respectively, forming a leak-free bottom flow plenum 203-1 inside the bottom header 203. This fixes the bottom tube sheet 204 in place within the container.

[0072] The shell 201-3 of the upper header 201 protrudes upward from the upper closing plate 136 of the TES vessel housing. The dome-shaped head 201-2 is seal-welded to the upper end of the shell 201-3, forming a leak-free upper flow plenum 201-1 inside the upper header 201. In some embodiments, the head is elliptical or hemispherical, but other dome-shaped structures are also available. The dome-shaped head of each upper header is provided with a fluid outlet 212 in the form of a protruding short pipe section, which discharges the heated second working fluid (e.g., water in the vapor phase) from the top header. The vapor flow from the TES vessel 130 is controlled by a fluid outlet valve 212-1 (see, for example, Figure 22). In one embodiment, the fluid outlet 212 may be located in the center of the top of the head to collect the heat transfer fluid of the liquid or vapor phase that is discharged from the TES vessel 130 after being heated. The fluid outlets from each heat exchanger 200 can be fluidically coupled to form a single steam fluid stream (Schematicly shown in Figure 2) that exits the container and enters the second closed flow loop 341 of the power generation system 340.

[0073] According to another aspect of the present invention, the TES container 130 that converts water to steam on the tube side of the heat exchange tube 211 of the tube bundle 210 may include a demister 213. Figure 7 is an enlarged cross-sectional view of the upper header 201 and the demister 213. The demister serves to regulate and dry the steam before it is discharged from the upper header 201 through the fluid outlet 212, thereby improving the "steam quality" (the proportion of saturated steam present in the saturated liquid / steam mixture). Generally, higher steam quality is desirable because it leads to higher heat transfer efficiency.

[0074] In one embodiment, the demister 213 can be formed by an expanded metal mesh panel 213-1 with multiple openings between mesh wires through which steam can pass and flow. Carryover water droplets mixed with the steam and collected condense on the metal mesh and fall downward from the demister by gravity to the upper tube sheet 202 in the upper header 201 / flow plenum 201-1 (see Figure 9). The collected water (e.g., condensed water) is discharged from the upper header by a vertical downcomer 214 fluidly coupled to the upper header 201 via a drain outlet 215 coupled to the shell 201-3 of the header as shown. The downcomer may be formed by a pipe in one non-limiting embodiment and located outside the housing 134 of the TES vessel adjacent to the side wall 133 of the housing. The lower end of each downcomer 214 is fluidly coupled to the lower header 203 / flow plenum 203-1 via a header fluid inlet 217 to return the drain thereto. The fluid inlet may be formed by a short pipe section. Therefore, as shown in Figure 9, a fluid circulation loop is formed between the upper header 201 and the lower header 203 and the tube bundle 110 by the downcomer 214. In the circulation loop, some of the heated heat present at the upper end of the tubes in the upper header 201 is recirculated to the lower header 203 via the downcomer 214, as will be further described herein. The drain outlet 215 of the upper header 201, located above the downcomer 214, could also be formed from a short pipe section, but is positioned at a height close to the top surface of the upper tube sheet 202 for reasons that will become apparent below.

[0075] It should be noted that the condensed water collected in the header 201 accumulates, forming a shallow condensed water pool P with a defined surface level 216 (see, for example, Figure 22). To prevent steam discharged from the heat exchanger tubes 211 to the upper header 201 from remixing with the accumulated water and becoming wet again, each heat exchanger tube 211 can project upward (or have a tube extension) by a sufficient length (e.g., height) from the upper tube sheet 202, such that its upper opening 220-1 is positioned higher than the surface level 216 of the condensed water pool P. When setting the height of the extension tube, the expected fluctuations in the surface level 216 of the condensed water pool P in the upper header can be taken into consideration. The lower end of the extension tube 220 is welded to the upper surface of the upper tube sheet 202 around each heat exchanger tube 211, and projects vertically upward by a certain length from there. Circumferential seal welds are formed on the upper surface of the tube sheet 202 surrounding the upper end of each heat exchanger tube 211 and its respective extension tube 220, so that the tubes are in direct fluid communication with them. The drain outlet 215 of the upper header 201 is positioned at a height such that accumulated water enters the upper end of the discharge pipe and is discharged from the outlet before it mixes with the steam flowing upward and outward. Thus, the height of the upper end 220-1 of the extension tube 220 is higher than the surface level 216 of the condensate pool P, which is set and fixed by the height of the upper header drain outlet 215 as described above.

[0076] In one embodiment, a second working fluid (e.g., condensed water) is discharged from the upper header 201 of each heat exchanger 200 through its respective downcomer 214 to the bottom header 203, thereby generating a natural passive convection thermal siphon circulation flow loop resulting from heating the heat transfer fluid in the heat exchanger tubes 211 within the TES vessel 130 (see, for example, the second working fluid flow arrow in Figure 9). This generates a natural fluid circulation by gravity and heating on the tube side between the upper header 201 and the bottom header 203 through the tube bundle 210 of each heat exchanger 200, which is not driven by a mechanical pump. The heated fluid becomes less dense and rises, promoting the circulation flow. The principle of the thermal siphon effect is well understood by those skilled in the art without further explanation.

[0077] The flow of the second working fluid through the tube bundle 210 of the TES container 130 and the second closed flow loop 341 may, in one embodiment, be a vertically upward linear path formed by linear heat transfer tubes 211, as shown in Figure 9. This arrangement utilizes the natural thermal siphon effect and gravity to drive a recirculation flow of condensate through the downcomer 214 between the upper and bottom flow plenums of the heat exchanger 200, as described above. The rising second working fluid (e.g., water) is heated within the tubes 211 of the tube bundle 210 and passively draws the condensate flowing in from the downcomer into the fluid inlet 217 and bottom header 203 without the need for or use of a pump.

[0078] In some embodiments, instead of an external downcomer 214, the downcomer can be defined by several heat exchanger tubes 211 located inside the TES container 130, in a colder region of the container.

[0079] The second working fluid, heated by the thermomass composition M in the TES vessel 130, is discharged from the TES vessel 130 as steam via the fluid outlets 212 of each heat exchanger 200, generating thermal energy for power generation via the turbine generator set. After this, the cooled heat transfer fluid is pumped back to the TES vessel via the second closed flow loop 341 described herein (see, for example, Figures 2 and 9). The cold or cooled fluid (i.e., feedwater) returning in the closed flow loop 341 can be directly piped to each downcomer 214 of the four heat exchangers 200 via a return fluid inlet 219 that is fluidly connected to each downcomer (see Figure 9). The flow of the second working fluid to the TES vessel 130 is controlled by a fluid inlet valve 219-1 (see, for example, Figure 9). The cold heat transfer fluid returning from the closed flow loop 110 is mixed with the heated condensate circulating downward through the downcomer from the upper header 201 of each heat exchanger 200, and then enters the bottom header 203 via a connection to a fluid inlet 217. Since a single fluid stream containing the condensate recirculation flow and the feedwater flow enters the bottom header 204, each bottom header requires only one connection to a fluid inlet 217. Furthermore, because the temperature of the heat transfer fluid mixed upstream of the bottom header is obtained, a uniform temperature of heat transfer fluid enters the bottom header, eliminating fluid temperature variations in different parts of the bottom flow plenum 203-1 within these headers. However, in other embodiments, a separate, independent return fluid inlet 219 may be directly fluid-connected to each heat exchanger bottom header 204, and this return fluid inlet 219 is separate from and in addition to the downcomer piping return fluid inlet connection (i.e., the fluid inlet 217 connection) formed in the bottom header. Both fluid return configurations are possible.

[0080] Each of the four heat exchangers 200 shown in the illustrated non-limiting embodiment is fluidically isolated from one another on the tubular side that carries the heat transfer fluid through the thermal mass composition M in the TES vessel 130. Advantageously, this allows one heat exchanger to be taken out of service for maintenance / repair (e.g., tubular blockage) while the remaining heat exchangers continue to function fully, thereby allowing the TES vessel 130 to continue operating. Furthermore, for significant operational flexibility, the demand for the heat transfer fluid (heated liquid or steam) may not always require all four heat exchangers 200 to be operating. Therefore, it is advantageous that each heat exchanger 200 and its associated discharge and inlet piping network be configured to be fluidically isolated from all other heat exchangers so that each heat exchanger can operate independently of the others.

[0081] Now, returning to the heat exchanger 200 and referring to Figures 2 and 5-9 in general as needed, the tube bundles 210 of each heat exchanger, which define the effective heat transfer area of ​​each heat exchanger, can be arranged in a linear, one-pass flow pattern on the tube side through a thermal mass composition M, which is stationary or “captured” mass that does not flow into or out of the TES vessel 130 (see the flow diagram in particular of Figure 9). The heated heat transfer fluid discharged from each heat exchanger (e.g., a second working fluid containing water in the steam phase) can be fluidically coupled and piped after exiting the upper header 201 of each heat exchanger to form a single steam flow for power generation or other applications such as district steam heating or industrial use.

[0082] It should be noted that the thermal mass composition M is a non-flowing, static / captive mass within the TES container 130, since the internal cavity 135 of the TES container is at atmospheric pressure and therefore unpressurized. Consequently, the tubes 211 of the tube bundle 210 form a pressure boundary for the heat transfer fluid flowing through them, and the heat transfer fluid is heated and pressurized by the thermal mass composition.

[0083] Each heat exchanger 200 is provided with at least one manway 240 to allow access to the upper header 201 and the lower header 203. The manway comprises an openable hatch 241 hinged to the vertical shell of the headers 201, 203. The hatch is configured to fluidly seal the access opening to the header by incorporating appropriate gasket material. Since it is not uncommon for heat exchanger tubes to crack and leak over time due to the chain of temperature and pressure, the manway 240 allows workers easy access to the upper or lower tube sheets 202, 204 for maintenance such as plugging leaking tubes in the tube sheets and for periodic inspection of cracks in the tube ligaments of the tube sheets.

[0084] The TES container 130 further includes a plurality of filling ports 245 at its top, extending through the upper closing plate 136. The filling ports allow the addition of the thermal mass composition M to the internal cavity 135 of the container. In one embodiment, four filling ports are provided, one at each upper corner of the container (see, for example, Figure 5). Each filling port may consist of a short section of capped piping that is in fluid communication with the internal cavity 135 of the container 130, as shown.

[0085] Of particular note is that the internal cavity 135 of the TES vessel 130 defines a common space or volume shared by the tube bundle 210 of all heat exchangers 200. Thus, the outer surface of the heat transfer tubes 211 of each heat exchanger is in physical direct and conformal contact with the same undivided / unseparated bed of thermal mass composition M within the cavity 135. Advantageously, this ensures that the heat transfer fluid flowing through the tube side of each heat exchanger 200 is uniformly heated by a single thermal mass. Therefore, there are no physical partitions or dividers subdividing the internal cavity 135 of the vessel, thereby further reducing manufacturing costs. In contrast, the tube sides of the heat exchangers are fluidically separated from one another, as described elsewhere in this specification.

[0086] The components of the heat exchanger 200, including the upper header 202, the bottom header 204, and the tubes 211, are all of a metallic structure. These parts are preferably made of steel, and more preferably, at least the wetted parts are made of a suitable corrosion-resistant metal such as stainless steel. However, other types of tube materials may also be used. An appropriate type of tube material can be selected considering its compatibility with and use with the specific type of thermal mass composition M used, so that it is not affected by corrosion due to the chemical properties of the phase change components of the material. Depending on the specific application, other metallic materials may also be used for the components of the heat exchanger.

[0087] Next, a first set of heat exchanger tubes 331 associated with the solar energy collection system 310 are described, extending through the thermal mass composition M within the internal cavity 135 of the TES container 130. The tubes 331 receive a first working fluid heated from the solar thermal collector 312. This first working fluid may be a molten salt or heat transfer oil in some embodiments. The tubes 331 can be scattered among the heat exchanger tubes 211 associated with the second closed flow loop 341 of the power generation system 340 described herein. Preferably, the tubes 331 are uniformly dispersed throughout the thermal mass composition to heat the composition material as uniformly as possible.

[0088] The heat exchanger tube 331 is fluidically coupled to at least one fluid inlet 336 and at least one fluid outlet 337, which are accessible from outside the TES vessel 130 as shown in Figure 5 and are fluidically coupled to the rest of the first closed flow loop 311. The fluid inlet 336 is part of the "hot" leg (high temperature side) of the first closed flow loop that delivers the heated first working fluid to the vessel 130. The fluid outlet 337 is part of the "cold" leg portion of the first closed flow loop, receiving the cooled first working fluid from the vessel, releasing its heat into the thermal mass composition M, and then sending the cooled fluid back to the solar thermal collector 312 for reheating. In one embodiment, the inlet 336 and outlet 337 may be formed by short stub portions of pipe. As shown in the illustration, in one embodiment the inlet 336 and outlet 337 are located on the side wall 133 of the TES container 130 and extend through the side wall, or alternatively, they are located on the upper and bottom closing plates 136, 137 and extend through the closing plates 136, 137, or, depending on the internal route and arrangement of the heat exchanger tubes 311 passing through the inside of the container, they can be located on a combination of the side wall and the upper and bottom plates and extend through them.

[0089] In one embodiment, the heat exchanger tube 331 is positioned vertically within the TES vessel 130 and fluid-coupled to an upper inlet header 335a and a bottom outlet header 335b, as schematically shown in Figure 10. The headers may be internal, as shown, or external to the outer housing of the TES vessel. In the illustrated embodiment, the tube 331 is a straight tube. In other embodiments, the tube 331 may be oriented horizontally and aligned in a straight line, or arranged in a U-shaped tube bundle, but these designs are well known in the art and will not be described in further detail here. Thus, any suitable arrangement and orientation of the heat exchanger tube 331 within the TES vessel 130 is possible, as long as the thermal mass composition M is heated uniformly and interference with the heat exchanger tube 211 of the second closed flow loop 341 that carries the second working fluid is avoided.

[0090] The heat exchanger tubes 331, which form an integrated fluid component of the first closed flow loop 311, can be made of any suitable metallic material designed to suit the expected operating conditions associated with the first working fluid (e.g., molten salt or heat transfer oil). In some embodiments, stainless steel may be used.

[0091] In some embodiments, the TES container 130 may optionally be equipped with an auxiliary heat input function in the form of an electric immersion heater 150 that can draw power from the power grid to heat the thermal mass composition M, preferably when electricity is inexpensive, such as during off-peak load demand periods on the power grid. However, if auxiliary heat is needed at other times to heat the thermal mass composition to its operating temperature, the heater can be energized during peak hours or normal operation of the power grid to allow the solar thermal power system to continue generating power.

[0092] Alternatively, the power source for the electric immersion heater 150 may be a wind farm equipped with one or more wind turbine generators 480 electrically connected to the heaters (see, for example, Figure 2). In various embodiments, the wind turbine generator unit may be used in combination with or instead of the solar collector 312 described herein. The wind power option is advantageous when installing a hybrid power system in a location where sufficient solar radiation may not be available to fully load (i.e. heat) the thermal mass composition M in the TES vessel 130 (green boiler) to a degree sufficient to increase the enthalpy of the second working fluid (steam in the case of a Rankine cycle, gas in the case of a Brayton cycle) to operate the turbine generator set of the power generation system 340. Referring to Figures 5 and 6, an array of electric immersion heaters 150 can be embedded in the thermal mass composition M held within the internal cavity 135 of the vessel. The heaters are configured to be electrically connected to an available power source via suitable commercially available electrical contacts or connectors as required for the intended application. The power source may be a local power grid managed by a public utility, and / or an on-site local power source such as a power plant that generates electricity using renewable energy sources (solar, wind, biomass, etc.) or nuclear power. The heater 150 converts the electricity received from the power source (regardless of its nature) into thermal energy used to heat the thermomass composition.

[0093] In one embodiment, each heater 150 may have a modular structure including a panel or box-shaped heater housing 151 and a plurality of horizontally elongated heating elements 152 mounted on the housing (see also Figures 7 and 8). The housing 151 is configured to support the heating elements and forms a freestanding heater that can be treated as a single unit and installed / removed. In one embodiment, the housing 151 includes a plurality of vertical heating element support plates 151-2 arranged horizontally at intervals, each plate having a hole for receiving and supporting horizontally elongated elements. The housing 151 may have a rectangular parallelepiped configuration in one embodiment as shown, but other polygonal or non-polygonal (e.g., cylindrical) heater housings are also provided. The heating elements 170 may be oriented horizontally and rod-shaped. Each element is in direct physical contact with the internal cavity 135 of the thermal mass composition M of the TES container 130. In one non-limiting embodiment, the heating elements may have a cylindrical configuration.

[0094] The heaters 150 can be inserted horizontally, removable, and slidably into the internal cavity 135 of the TES vessel between the vertical heat exchanger tubes 211 of the tube bundle 210 of each heat exchanger 200. In one non-limiting configuration, banks of heaters 150 may be located on two opposite side walls 133 of the TES vessel 130. The units 150 are spaced apart from each other vertically and horizontally on each side wall, as shown in the figure. A sufficient number of heaters 150 are provided, which are preferably arranged substantially along the entire height, over most of the height of the internal cavity 135 of the TES vessel and the bed of the thermal mass composition M contained therein, to uniformly heat the bed of material from top to bottom. In Figure 2, for simplicity, only a single cluster, i.e., one group of heaters 150, at one height of the TES vessel 130 is shown, but in implementation, as shown in Figure 6, the heaters can extend along the height of the vessel and consist of multiple groups of heaters at multiple heights. In one embodiment, each heater 150 may have a horizontal width exceeding 40% of the width of the TES container housing 134 measured between opposing side walls 133. Thus, the width of each heater 150 is slightly less than half the width of the container housing, preferably greater than the horizontal / lateral range of each heat exchanger tube bundle 210, to ensure that the thermal mass composition adjacent to each heat exchanger tube 211 of the bundle is properly heated by the heating element 152 of the heater (see, for example, Figure 25).

[0095] As shown in the figure, pairs of heaters 150 can be arranged end-to-end facing each other at each height of the container 130 in which the heaters are located, with each unit inserted from either of the two opposite container side walls 133. Any appropriate number of heaters 150 can be provided to sufficiently heat the thermal mass composition M to a desired maximum temperature, thereby determining the maximum temperature at which the second working fluid of the power generation system 340 flowing through the heat exchanger tubes 211 embedded in the thermal mass can be heated.

[0096] The heater 150 can be removably coupled to the side plate 133-1 of the opposite side wall of the TES container by any suitable fastening means (e.g., including, but not limited to, welding, screw fasteners, or other methods). Complementarily configured mounting holes are provided in the TES container housing 134 (i.e., the side plate 133-1 of the side wall 133) to allow the elongated heating element 152 of the heater 150 to slide into the internal cavity 135 of the container and embed into the thermal mass composition. The thermal mass composition M can be added to the internal cavity of the container after the heater 150 has been installed in stages at each height from the bottom to the top of the container. Other methods of installing the heater and thermal mass composition can also be used. It is preferable to provide a relatively close interface between the container housing mounting holes 153 and the outermost exposed portion of the heater housing 151 that protrudes laterally / horizontally outward from the side wall 133 of the TES container 130.

[0097] When the heater is installed in the thermal energy storage container 130, the thermomass composition M, which is generally composed of granular solid particles in its unheated state, fills the gap between the heating element 152 and the heat exchanger tube 211 before the element is energized. When the heating element is energized, the phase change material (PCM) particles, which were previously granular solids, melt and are converted into a flowable liquid, i.e., a molten state, filling the gaps between the non-molten components of the thermomass composition (i.e., the metallic materials further described herein). The thermomass composition is in direct conformal contact with the heating element 152 and the tube 211, ensuring that heat transfer to the heat transfer fluid flowing through the tube 211 of the heat exchanger 200 is maximized.

[0098] To retain the heat of the thermal mass composition M inside the TES container 130, the housing 134 has a strong insulating structure. Figure 8 shows the insulated TES container, including an insulating outer layer 160 schematically represented by dashed lines wrapped around the side walls 133 of the container. Other parts of the container and apparatus are insulated and may be heat-traceable as needed (e.g., exposed parts of the top plate).

[0099] Let's further explain the thermal-mass composition M.

[0100] Any suitable thermal mass composition M can be used and can be customized and selected to match the heat load and operating parameters required to heat the heat transfer fluid (water / water mixture or other fluid) from the inlet temperature into the TES (Thermal Energy Storage) container 130 to the desired outlet temperature. In one preferred embodiment, the thermal mass composition may be a mixture of at least one first base metal material and a second phase change material (PCM), though not limited to these. Both the base metal material and the PCM of the thermal mass composition mixture are in granular particle form (i.e., solid) at room temperature and are fluidizable to fill the internal cavity 135 of the TES container through an openable and closable filling port 245 (see, for example, Figure 5) through the container housing 134. Both the base metal material and the PCM are materials configured to generate a thermal mass capable of absorbing and storing heat and releasing that heat on demand when it is necessary to heat the heat transfer fluid flowing through the tubes 211 of the tube bundles 210 in each heat exchanger 200.

[0101] Preferably, at least one base metal material constitutes the majority of the mixture or composition and has a melting point or temperature Tbm higher than the melting point or temperature TPCM of the PCM. The temperature TPCM is preferably lower than the normal operating temperature Tnm of the thermal mass composition M, and the thermal mass reaches the normal operating temperature Tnm (by heat or thermal energy supplied by the heater 150) so that when the thermal mass is heated, the PCM melts and changes to a liquid or molten state. At room temperature, the PCM is in the state of solid particles.

[0102] In contrast, at least one base metal material preferably has a melting point Tbm higher than the normal operating temperature Tmm, and preferably a melting point Tbm higher than the maximum temperature Tmax of the thermomass composition when heated by the heater, so that the base metal material always remains in a solid particle state regardless of whether the heater is fully energized or offline. In some representative but non-limiting examples, the base metal material may have a melting point Tbm above 1,000°C (Celsius), or in some embodiments above 2,000°C, while the PCM may have a melting point TPCM below 1,000°C. The metal material may include iron and / or non-ferrous metal particles, alone or in combination, selected to optimize heat retention and satisfy the aforementioned melting point criteria.

[0103] When used for storing thermal energy, first, the TES container 130 (i.e., the internal cavity 135) is filled with the thermal mass composition M to the highest or topmost point in the container, i.e., to a final height or level that at least covers the heater 150. Both at least one base metal material and the PCM are in a solid granular particle state at ambient temperature before the thermal mass is heated by the electric heater 150. Next, the heater 150, which was initially "off", is energized and the entire bed of thermal mass composition M is heated to its normal operating temperature Tnm (which may be lower than the maximum temperature Tmax in some cases). While at least one base metal material remains in the form of solid granular particles, the PCM melts and thereby flows out to fill the gaps / voids between the base metal material particles. This has the advantage that the thermal mass composition M can be heated more efficiently and completely than when all metal materials are used, as the air-filled pockets or voids between the material particles are filled with conductive liquid PCM, improving the thermal retention properties of the thermal mass. From another perspective, this might be seen as somewhat similar to damp sand with water filling the gaps between the grains. The combination of molten PCM and still solid base metal material particles allows the thermal mass composition mixture to further enhance conformal contact with both the heating element 152 of the heater 150 and the outer surface of the tubes 211 of each heat exchanger 200, thereby further improving heat transfer. When the heat input is removed from the thermal mass composition by turning off the power to the heater 150, the PCM returns to a solid state.

[0104] In a preferred, non-limiting embodiment, the PCM used may be a salt that, when energized by power extracted from an available power source such as a power grid or other power source and heated by an electric immersion heater 150, can be converted from a granular solid particle state at ambient temperature to a liquid / molten state. A suitable salt can be used, selected according to the required heat load.

[0105] The following table shows examples of salts that can be used to form the PCM bed B in each thermal energy storage container 121. TIFF2026519861000002.tif166157

[0106] The melting point and latent heat properties of salt are influential characteristics and factors when selecting the type of salt depending on the required heat load and temperature rise of the heat transfer fluid. Therefore, it should be noted that the type of salt used in the energy storage container 130 for the green boiler 120 may be customized and different. It will be apparent to those skilled in the art that, regardless of the application, including simply heating water for district heating or other applications, the heat load and performance of the thermal energy storage container 121 can be highly customized to meet the required temperature rise targets of its thermal energy system.

[0107] It should be noted that during the operation of the TES container 130 when the heater 150 is energized, any suitable PCM other than the salts listed above can be used, as long as the melting point Tpcm of the PCM is lower than the normal operating temperature Tnm (as specified herein) of the thermomass composition.

[0108] The thermal energy storage (TES) containers 130, 121 disclosed herein are described non-limited in one embodiment as heating water (a second working fluid) through a thermal mass composition layer and converting it to a steam phase to operate a steam turbine, but the present invention is not limited thereto. Thus, the TES container 130 can also be used to heat other types of fluids that can flow through the heat exchanger tubes 211 of the container. Thus, a variety of applications are possible for the “green” thermal energy storage system 100, and these are within the scope of this disclosure.

[0109] The general operation of the TES container 130, which stores thermal energy and heats a heat transfer fluid, can be summarized as follows, first with reference to Figure 2. The process or method can begin by heating the thermal mass composition M in the container by circulating a first working fluid from a solar thermal collector 312 through a first closed flow loop 311 and heat exchanger tubes 318 embedded in the thermal mass composition. The high-temperature first working fluid (e.g., molten salt or heat transfer oil) heats the thermal mass composition, is cooled, and returns to the solar thermal collector for reheating. The solar thermal collector heats the first working fluid through solar radiation incident during daylight hours when the sun is shining, as previously described herein.

[0110] A second working fluid in a cooled state (which may be boiler feedwater in a preferred embodiment) flows through a second closed flow loop 341 to the inlet header 203 of the heat exchanger 200, and then through heat exchanger tubes 211 embedded in the thermal mass composition M. The second working fluid absorbs heat from the composition, raising the fluid temperature above its boiling point and converting the water into steam, which is collected at the outlet header 201. The steam flows through the second closed flow loop to the steam turbine 103, where it generates electricity by electromagnetic induction via a generator 103 operably coupled to the turbine in a well-known manner. The steam enters the turbine at a pressure higher than the pressure it exits, and the thermal energy is converted into electrical energy via the steam turbine generator set. The low-pressure steam is condensed by a condenser 106 and returned to the TES vessel 130 via the second closed flow loop 341, thereby repeating the process.

[0111] If sufficient thermal energy is exhausted to heat the second working fluid in the thermal mass composition M, which is associated with the power generation system 340, to the desired steam operating conditions (e.g., steam pressure and temperature) necessary to generate electricity, the auxiliary electric immersion heater 150 can be used as a backup. This scenario may occur when power generation is needed at night after sunset when solar energy is unavailable and the layer of thermal mass composition M cannot be reheated. This is a very realistic scenario, especially in hot regions such as the desert climate states of the southwestern United States, where periods of high electricity demand for cooling during the day can persist, potentially keeping summer temperatures above 100 degrees Fahrenheit even after sunset.

[0112] Next, the bank of electric immersion heaters 150 is energized by drawing power from the public power grid (or other power source) to heat the thermal mass composition M to the operating temperature required to generate electricity.

[0113] In another scenario, depending on the location where the solar thermal power system 300 is installed, cloud cover may prevent sufficient solar radiation from reaching the solar collector 312 to heat the layer of thermal mass composition M to the required operating temperature. The electric immersion heater 150 can be operated during off-peak demand periods of the power grid, when energy costs are lowest, provided that it is possible to reheat the thermal mass composition. Power is supplied to the heater until the thermal mass composition M is heated to a temperature that is its normal operating temperature Tnm and to its optimal heat retention capacity. Power is then removed from the power source. The thermal mass composition is now fully thermally heated and in a standby state, ready to be operated at any time as needed to generate steam or hot water (or other heated heat transfer fluid) when required by the thermal energy system in Figure 1B or 1C.

[0114] The following describes and summarizes a method or process for heating a heat transfer fluid using a green boiler 120. This method involves providing a thermal energy storage container 130 that contains a thermal mass composition M comprising a mixture of a metallic material and a phase change material, each initially in the form of solid particles. The melting point of the metallic material is higher than that of the phase change material. This method continues to heat the thermal mass composition to a temperature that melts the phase change material, while the metallic material remains as solid particles. This method continues to store heat in the thermal mass composition. In this method, one heat transfer fluid (e.g., a second working fluid) associated with the power generation system 340 is circulated through the thermal mass composition to continue heating the heat transfer fluid. The heating step may include (1) passing another transfer fluid (e.g., a first working fluid) through the thermal mass composition, or (2) energizing a plurality of electric heaters embedded in the thermal mass composition. The circulation step may include passing the second working fluid through a tube bundle embedded in the thermal mass composition. The tube bundle may be part of at least one heat exchanger 200 incorporated into the thermal energy storage container. The heated second working fluid may be in the form of vapor or phase. The heating step may further include the flow of molten phase-change material filling the gaps between solid particles of the metallic material.

[0115] According to another aspect of the present invention, a hybrid power generation system can be used to operate a Brayton power generation cycle using air, carbon dioxide (CO2), or other suitable compressible gas. In some embodiments, supercritical CO2 may be used. The gas is the second working fluid in the power generation system portion of the hybrid system. The gas is first compressed by a compressor replacing the nuclear steam supply system (NSSS) 400 and flows through a second closed flow loop 341 to the TES vessel 130 (green boiler). The gas is heated by a thermal mass composition M heated by solar or wind energy, increasing the enthalpy of the gas. The gas then passes through a turbine generator set similar to a turbine generator set 102, but operated by compressed gas instead of steam. The Brayton system can be visualized in Figure 2 by inserting a gas compressor 435 (schematically represented by a dashed line) into the second closed flow loop 341 between the steam turbine 102 and the inlet of the TES vessel 130. The steam condenser 105 and feedwater pump 106 associated with the Rankine cycle are naturally omitted. The Brayton power generation cycle system and apparatus are well known in the art. Based on the information provided in this disclosure, it is within the scope of the art to form a hybrid power generation system using the Brayton gas power generation cycle instead of the Rankine steam power generation cycle.

[0116] It is noteworthy that, unlike battery energy storage systems, the green boiler 120 disclosed herein does not use any rare earth elements or environmentally harmful substances. Furthermore, unlike battery materials, the thermal mass composition M is not at risk of degradation due to aging, thus guaranteeing a long service life.

[0117] Furthermore, while the 24 / 7 solar thermal power generation system shown in Figure 2 exhibits a classical Rankine cycle (steam-based), the system can instead be a gas-driven (e.g., carbon dioxide / CO2 or other gas) Brayton cycle, at the plant owner's discretion, resulting in higher thermodynamic efficiency. Alternatively, the system could utilize the bottoming Goswami cycle, known in the art and disclosed in Chapter 7, "The Goswami cycle and its applications," by G. Demirkaya, M. Levini, RVPadilla, and D. Yogi Goswami. Choosing either of these options would further increase thermodynamic efficiency.

[0118] [Goswami Cycle]

[0119] Figure 11 is a modified system flow diagram to include an optional Goswami bottoming cycle operably connected to the main Rankine cycle power generation system 340 (including turbine generators 102-103) of Figure 2. Figure 12 is a schematic flow diagram showing the Goswami cycle in more detail. The Goswami cycle is a cogeneration cycle that circulates a two-component mixed working fluid (hereinafter referred to as "G working fluid" for brevity) in a flow loop 510 via a separate Goswami cycle system 500 that combines a separate second Rankine cycle and an absorption refrigeration cycle, thereby obtaining both power generation and refrigeration in some embodiments. Any suitable two-component mixed working fluid having a first component and a second component that is more volatile than the first component can be used. In one embodiment, a solution containing a mixture of ammonia and water can be used as the two-component G working fluid, for example.

[0120] The condenser 105 in the Rankine cycle in Figure 2 is replaced by a boiler 501 of the Goswami cycle system 500, which extracts a second heated working fluid (e.g., steam if water is used, or a gas such as CO2 if a Brayton cycle is used) from the turbine 102. The system further comprises an absorber 506, a heat recovery heat exchanger 507, a rectifier / separator 502, an optional superheater 503, a turbine 504, and a refrigeration heat exchanger 505, all of which are operably fluidly connected within the flow loop 510.

[0121] In short, the operation of the Goswami cycle is as follows: The Goswami working fluid is sent from the absorber 506 via the pump 508 through the heat recovery exchanger 507 to the boiler 501 in the flow loop 510. The Goswami working fluid exits the absorber 506 as a saturated liquid. The heat recovery heat exchanger 507 preheats the liquid Goswami working fluid, raising its temperature before it enters the boiler. The saturated liquid Goswami working fluid is preheated in the heat exchanger 507 by absorbing heat from the hotter Goswami working fluid (already heated in the boiler 501) extracted from the rectifier / separator 502.

[0122] During operation, the boiler heats the Goswami working fluid via a heated second working fluid extracted from the turbine 102, further increasing its temperature and creating a two-phase flow stream containing a heated liquid phase and a heated steam phase of the working fluid. The two-phase mixture of the heated Goswami working fluid flows into the rectifier / separator 502, where the mixture is separated into a heated steam component and a heated liquid component, the latter of which passes through the heat recovery heat exchanger 507 (as described above) to first increase the temperature of the Goswami working fluid from the absorber 506. In some embodiments, the steam may be partially cooled within the rectifier / separator 502 by passing another fluid cooling medium that is colder than the steam (and fluidically separated from the steam) through the rectifier / separator 502. This causes any residual liquid mixed with the steam in the rectifier / separator to condense.

[0123] The heated liquid component of the Goswami working fluid from the rectifier / separator 502 transfers heat to the Goswami working fluid entering the heat recovery heat exchanger 507 from the absorber 506, where it is cooled. The cooled liquid exiting the heat recovery heat exchanger 507 is sprayed into the absorber. A throttle valve 509 can be used to restrict the flow of liquid from the heat recovery heat exchanger 507 into the absorber.

[0124] The vapor phase of the heated Goswami working fluid simultaneously exits the rectifier / separator 502 and flows as vapor through the flow loop 510 to the refrigeration heat exchanger 505. Optionally, in some embodiments, the heated steam may first pass through the superheater 503 to heat the steam to a superheated state. In any case, the vapor Goswami working fluid expands in a turbine 504, which may be equipped with an associated generator to produce electricity. The steam exiting the low-pressure section of the turbine is condensed in the refrigeration heat exchanger 505. The cooled condensate flows to the absorber 506, and this cycle is repeated.

[0125] The features of the solar thermal power generation system disclosed herein can be summarized as follows:

[0126] In one embodiment, the Green Boiler 120 can use a eutectic salt in a thermomass composition that has a large energy release capacity before undergoing a phase change (solidification) when heated to a sufficiently high temperature (e.g., 600°C).

[0127] If necessary, salt species that enhance radiant heat transfer can be added to the salt eutectic.

[0128] The layout and size of the heliostats are optimized to maximize the energy capture density of the land occupied by the power plant.

[0129] The power tower's thermal receiver is positioned at a height that accommodates the optimized heliostat layout. The receiver is housed in a hollow, columnar column called the power tower and is fluidly connected to the first working fluid recirculation pump, which has an upper expansion tank and thermally constrained stresses minimized using appropriately sized insulated riser piping and expansion joints.

[0130] Each receiver may be a curved plate-like structure made of corrugated metal plates, integrally welded to a thick backup plate to form a pair of parallel "half-tubes." The heat absorption region of the receiver device is the area surrounding the fluid by headers at both ends (upper and lower).

[0131] The inner surface of the half-tube is treated with a conical, finely textured pattern to improve heat transfer between the tube surface and the fluid flowing inside the tube.

[0132] The receiver header can be configured to create a multi-pass first working fluid (e.g., molten salt or heat transfer oil) to obtain the amount of heat required for the cycle, as needed.

[0133] The expansion tank is a molten salt from which oxygen has been removed and which is partially filled with the first working fluid, providing heat trace and preventing the fluid in the solar thermal collector system from becoming solid.

[0134] A key component of the solar thermal power generation system is the green boiler 120, which has two separate, fluidically separated tube bundles. One tube bundle is fluidically coupled to the solar thermal collector and carries a first working fluid to heat the thermal mass composition, while the other tube bundle heats a second working fluid to generate high-pressure steam (Rankine cycle) or high-temperature carbon dioxide (Brayton cycle) to produce electricity.

[0135] To prevent the first working fluid (e.g., molten salt) from freezing during periods of prolonged cloud cover, all vessels and piping within the first closed flow loop 311 can be heat-trace and heavily insulated to minimize heat loss to the environment.

[0136] The Green Boiler 120 may have an auxiliary heat input function in the form of an electric immersion heater that can draw power from the power grid when electricity is inexpensive, or it may be equipped with a wind turbine generator on the premises.

[0137] The pressure and temperature of the steam produced by the green boiler can be selected to suit the plant owner's needs. For example, the generated steam can be used to supply process steam to nearby industrial plants, power hydrogen production facilities, or for other purposes.

[0138] The rectangular prism-shaped power tower structure allows for the construction of extremely tall columns, making it possible to install and operate multiple rows of receivers at different elevations. Since the riser piping is housed within the power tower, the effects of heat dissipation factors such as wind and rain are reduced.

[0139] The cylindrical cross-section of the power generation tower allows for the installation of multiple receivers in a circular pattern, enabling more complete capture of solar heat in a celestial orbit suited to its design.

[0140] To more efficiently capture heat from a large heliostat field, it may be more efficient to place receivers at multiple heights within a sufficiently tall power tower.

[0141] One of the key characteristics of solar thermal power systems is their ability to supply power "on demand" or continuously, depending on the owner's choice. Therefore, they can function as either base-load units or "peakers" (peak power units) to best meet consumer needs.

[0142] Figure 2 shows a single green boiler 120 (TES vessel 130) that is 60 feet (18.29 meters) tall, but heat can also be transferred from a first working fluid (e.g., molten salt or heat transfer oil) to a thermomass composition contained in the green boiler array using multiple green boiler arrays in which each green boiler operates in parallel via a parallel flow fluid coupling.

[0143] When the steam pressure and temperature requirements are relatively moderate, a suitable synthetic oil can be used as the heat transfer fluid. Synthetic oil can be used effectively when the maximum temperature limit can be maintained below 400 degrees Celsius. Solar thermal collectors using synthetic oil have a low freezing point, which may eliminate the need for heat tracing of the system's piping and containers.

[0144] While the foregoing description and drawings represent exemplary embodiments of the present disclosure, it will be understood that various additions, modifications, and substitutions can be made without departing from the spirit and scope of the appended claims and their equivalents. In particular, it will be obvious to those skilled in the art that the present invention can be embodied in other forms, structures, arrangements, proportions, sizes, and other elements, materials, and components without departing from its spirit or essential features. Furthermore, numerous variations can be made to the methods / processes described herein within the scope of the present disclosure. Those skilled in the art will further understand that embodiments can be used with many modifications to the structure, arrangement, proportions, sizes, materials, and components, etc., used in the implementation of the present disclosure to suit specific environmental and operating requirements without departing from the principles described herein. Accordingly, the embodiments currently disclosed should be considered in all respects to be exemplary and not limiting. The appended claims should be broadly interpreted to include variations and embodiments other than those disclosed that can be made by those skilled in the art without departing from the scope of their equivalents.

Claims

1. It is a solar thermal power generation system, A thermal energy storage container defining an internal space containing a thermal mass composition capable of operating to store thermal energy, A solar energy collection system comprising a first closed-flow loop including a solar thermal collector configured to absorb solar energy and heat a first working fluid, wherein the first closed-flow loop is configured to circulate the heated first working fluid in a thermal energy storage container to heat the thermal mass composition, A power generation system comprising a second closed-flow loop including a turbine, wherein the second closed-flow loop is configured to circulate a second working fluid through a thermal energy storage container to absorb thermal energy from the thermal mass composition and heat the second working fluid for introduction into the turbine, A generator that is operably connected to the turbine to generate electricity, A system characterized by comprising the following features.

2. The system according to claim 1, characterized in that the first closed flow loop is fluidically separated from the second closed flow loop.

3. The system according to claim 2, characterized in that each portion of the first and second closed flow loops extends through the thermal energy storage container.

4. The system according to claim 3, wherein the first closed flow loop comprises a first plurality of first heat exchanger tubes embedded in the thermal mass composition within the thermal energy storage container, and the second closed flow loop comprises a second plurality of second heat exchanger tubes embedded in the thermal mass composition.

5. The system according to claim 4, characterized in that the first heat exchanger tube is arranged at a distance from the second heat exchanger tube in the internal space of the thermal energy storage container.

6. A system according to claim 5, characterized in that the first heat exchanger tube transfers heat from the first working fluid to the thermomass composition, and the second heat exchanger tube absorbs heat from the thermomass composition.

7. A system according to any one of claims 1 to 6, wherein the first working fluid is a molten salt or a heat transfer oil, and the second working fluid is water that flows into the thermal energy storage container in a liquid state and is discharged from the thermal energy storage container as vapor.

8. A system according to any one of claims 1 to 7, wherein the thermomass composition comprises a mixture of a metallic material and a phase change material, each of which is in the form of solid particles at room temperature.

9. The system according to claim 8, characterized in that the metallic material has a higher melting point than the phase change material.

10. A system according to any one of claims 1 to 9, wherein the solar collector is a concentrating solar thermal power generation unit comprising a plurality of heliostats, each having a reflector, and a centrally located power tower having a plurality of heat receivers that form a fluid portion of the first closed flow loop, wherein the reflectors are operable to direct sunlight toward the heat receivers and heat the first working fluid that flows through the heat receivers.

11. The system according to claim 10, wherein each heat receiver comprises a plurality of heat exchanger tubes coupled between an upper outlet header and a bottom inlet header, and the first working fluid is capable of flowing through the heat exchanger tubes of the receiver.

12. The system according to claim 11, characterized in that the heat exchanger tube of each heat receiver is arranged as a tube wall including a pair of end tube walls that are angled obliquely to each other and an intermediate tube wall between them.

13. The system according to claim 12, characterized in that each of the heat receivers is substantially U-shaped.

14. A system according to any one of claims 11 to 13, wherein the power tower comprises an expansion tank fluidly coupled to the heat receiver.

15. A system according to any one of claims 10 to 14, wherein the first closed flow loop comprises a recirculation pump that circulates the first working fluid through the first closed flow loop through the heat receiver and the thermal energy storage container.

16. The system according to claim 1, wherein the first closed flow loop comprises a feed pump that circulates the second working fluid through the turbine and the thermal energy storage container via the second closed flow loop.

17. The system according to claim 16, wherein the second closed flow loop of the power generation system is configured to operate a Rankine power generation cycle.

18. A system according to any one of claims 10 to 17, further comprising a preheater configured to preheat the cooled first working fluid, which is returned from the thermal energy storage container to the solar thermal collector, using a portion extracted from the heated first working fluid, which is drawn out from the first closed flow loop and discharged from the solar thermal collector.

19. The system according to claim 18, wherein the preheater is fluidly coupled to a bypass piping loop configured to pass the extracted portion of the heated first working fluid into the preheater and heat the cooled first working fluid as it passes through while being fluidly isolated from the extracted portion.

20. The system according to claim 19, characterized in that the cooled first working fluid flows through a riser pipe fluidly coupled to the heat receiver on the power tower.

21. A system according to claim 19 or 20, wherein the preheater is a shell-and-tube heat exchanger, the heated first working fluid flows along the shell side of the heat exchanger, and the cooled first working fluid preheater flows along the tube side of a plurality of heat exchanger tubes extending through the preheater.

22. A system according to any one of claims 18 to 22, characterized in that the heated first working fluid flows downward through the preheater and the cooled first working fluid flows upward through the preheater.

23. A method of generating electricity using solar energy, A step of preparing a thermal energy storage container comprising a thermal mass composition having a formulation capable of operating to store thermal energy, A step of heating a first working fluid using solar radiation, The steps include: heating the thermomass composition by flowing the heated first working fluid through it; The steps include flowing a second working fluid through a thermal mass composition, A step of heating the second working fluid by causing it to absorb heat from the thermomass composition, The steps include: flowing the heated second working fluid to a turbine generator capable of generating electricity; A method characterized by including the following.

24. A method according to claim 23, characterized in that the first working fluid is recirculated in a first closed flow loop between a solar thermal collector that heats the first working fluid and the thermal energy storage container, and the second working fluid is recirculated in a second closed flow loop between the turbine generator set and the thermal energy storage container.

25. A method according to claim 24, characterized in that the first and second closed flow loops are fluidly separated from each other.

26. A method according to claim 23, characterized in that the heated second working fluid is vapor.

27. A method according to any one of claims 23 to 26, characterized in that the step of flowing the heated first working fluid through the thermomass composition includes flowing the heated first working fluid through a first plurality of heat exchanger tubes embedded in the thermomass composition, and the step of flowing the second working fluid through the thermomass composition includes flowing the second working fluid through a second plurality of heat exchanger tubes embedded in the thermomass composition.

28. A method according to claim 27, characterized in that the first and second plurality of heat exchanger tubes and the thermal mass composition are housed in a single outer housing of the thermal energy storage container.

29. A method according to any one of claims 23 to 28, wherein the thermomass composition comprises a mixture of a metallic material and a phase change material, each in the form of solid particles, and the metallic material has a higher melting point than the phase change material.

30. A method according to claim 29, characterized in that the thermomass composition is heated by the heated first working fluid to a temperature between the melting point of the metal material and the melting point of the phase change material, thereby melting the phase change material while the metal material remains in a solid state.

31. A method according to claim 30, characterized in that the molten phase change material flows and fills the gaps between the solid particles of the metal material.

32. A method according to claim 30 or 31, characterized in that the phase change material is a salt.

33. A method according to any one of claims 23 to 32, characterized in that the phase change material is a salt and the second working fluid is water.

34. A method according to claim 24, wherein the solar collector is a concentrating solar collector comprising a plurality of heliostats, each heliostat including a reflector, and a plurality of heat receivers located in the center that form a fluid portion of the first closed flow loop, wherein the reflector directs sunlight to the heat receivers and heats the first working fluid that flows through the heat receivers.

35. A method according to claim 24, further comprising energizing a plurality of electric heaters embedded in the thermomass composition to heat the thermomass composition.

36. A method according to claim 24, further comprising extracting a portion of the heated first working fluid and preheating the cooled first working fluid returning from the thermal energy storage container using the extracted portion of the first working fluid.

37. A method according to claim 23, further comprising the step of extracting steam from the turbine of the turbine generator set to heat the working fluid of the Goswami cycle system.

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