Solar receivers and methods for capturing solar energy

Thermal receivers, systems, and methods are disclosed that efficiently capture concentrated solar energy into a plurality of heat absorption bodies for conversion into thermal energy. In an embodiment, the thermal receivers, systems, and methods enable simultaneous electricity conversion and thermal energy capture. The receiver design enables a high penetration of concentrated sunlight deep into the thermal receiver to increase light trapping and reduce thermal losses. The thermal receiver is integrated with a photovoltaic (PV) receiver platform that converts some of the incident light to electricity while passing the remaining light to the thermal receiver. In another embodiment, other thermal receivers, systems, and methods are disclosed that efficiently capture concentrated solar energy into a sheet of falling particles. In an embodiment, the thermal receivers, systems, and methods enable simultaneous electricity conversion and thermal energy capture.

FIELD

The present disclosure is generally directed to solar energy. The present disclosure is more particularly directed to solar thermal systems that integrate a photovoltaic system with a thermal receiver.

BACKGROUND

Solar power systems offer much promise for clean energy, with few, or zero, carbon emissions. These systems collect incident sunlight and convert this sunlight into a usable form of power, such as heat or electricity. Solar energy offers a clean, inexhaustible, sustainable solution to energy demands and has the potential to supply a very significant fraction of U.S. and global electricity consumption. While the U.S. and global solar power potential is known to be immense, solar power systems have not been economically competitive without government support, to date. Challenges remain to devise solar technologies that can lower installation costs, increase power output, and lower the marginal cost per unit energy produced, for a lower levelized cost of energy. An important metric is the overall system efficiency, that is, the electric power output per incident solar power collected.

Solar power systems include photovoltaic (PV) systems, solar thermal systems, and others. PV systems utilize photovoltaic solar cells that convert sunlight directly into electricity by the photovoltaic effect. These solar cells are expensive, and their efficiencies are limited because they can exploit only a portion of the solar spectrum. These systems are also characterized by a large energy-payback period, i.e., the time they must be exposed to sunlight and produce electricity, to return the energy required to produce and install them.

Solar thermal systems convert sunlight into heat and either use this heat directly or convert the heat to generate electricity. Examples of solar thermal systems include solar power towers, parabolic trough systems, and dish-Stirling systems. Solar power towers utilize a large number of steerable, planar, or near-planar mirrors that reflect and direct rays of sunlight to a central tower where a heat-transfer fluid is heated. The heat collected is typically transferred to rotating machinery, such as a steam turbine, that is used to drive an electric generator. These systems suffer from low efficiencies because of high optical losses, such as cosine and other optical losses, solar-receiver losses, as well as temperature and power losses from long fluid-flow loops to and from the tower. Cosine losses refer to the energy lost when light rays from the sun do not strike the mirror perpendicular to its surface. To reflect rays of sunlight to the central tower, individual mirrors form an acute angle to the sun, therefore requiring more mirror surface than when the mirror is perpendicular to the sun's rays. Collection efficiency is increased and mirror cost is less when the mirror is perpendicular to the sun.

Volumetric solar receivers have been developed and implemented in concentrating solar power towers. The objective is to irradiate a honeycomb or waffle pattern of channels while pulling air through the channels to heat the air. The air is then used to heat a storage material or to generate steam for electricity production. Current designs of the channels do not allow for deep penetration of the irradiance, and the receiver surfaces get hot near the aperture, maximizing radiative heat loss. None of the previous volumetric receiver designs integrates PV.

Solar receivers have also been used to heat particles, both inert and thermochemically reactive particles for additional energy storage. Although no commercial solid particle receivers exist, a significant amount of research has been performed to develop efficient solid particle receivers for energy storage and electricity production. None of these previous concepts has included the use of a light-transmitting PV array at the aperture to generate electricity while mitigating convective and radiative heat losses.

The need remains, therefore, for a solar thermal system that efficiently converts sunlight into heat. The need also remains for solar power systems that combine the efficiencies of solar thermal systems and PV systems. The need also remains for solar power systems that combine the efficiencies of thermochemical particle systems and PV systems.

SUMMARY OF THE DISCLOSURE

In an embodiment of the disclosure, a solar receiver is disclosed that includes a thermal receiver and a photovoltaic receiver attached to the thermal receiver. The thermal receiver includes a housing having an opening for receiving concentrated solar energy and a plurality of heat absorbing bodies defining a passageway. The passageway includes an opening and an exit opening. The photovoltaic receiver includes openings for allowing air to pass through the photovoltaic receiver to the opening of the passageway of the thermal receiver. The photovoltaic receiver is configured to allow concentrated solar light passing through the photovoltaic receiver to illuminate the plurality of heat absorbing bodies

In another embodiment of the disclosure, a method of capturing concentrated solar energy is disclosed that includes illuminating a photovoltaic receiver with concentrated solar energy, capturing a portion of the concentrated solar energy with the photovoltaic receiver to generate electricity, absorbing a portion of the concentrated solar energy passing through the photovoltaic receiver into a plurality of heat absorbing bodies, and heating air passing over the plurality of heat absorbing bodies.

In another embodiment of the disclosure, a thermal receiver system is disclosed that includes a housing having an opening for receiving concentrated solar energy, and a plurality of heat absorbing bodies defining a passageway within the housing. The passageway comprising an opening for receiving air and an exit opening for discharging heated air. Concentrated solar energy received in the opening of the housing is directed into the opening of the passageway.

In another embodiment of the disclosure, a method of capturing solar energy is disclosed that includes passing concentrated solar energy through a window, absorbing a portion of the concentrated solar energy passing through the photovoltaic receiver into a plurality of heat absorbing bodies, and heating air by contacting the air with the plurality of heat absorbing bodies.

In another embodiment of the disclosure, a solar receiver is disclosed that includes a falling particle receiver and a photovoltaic receiver attached to the falling particle receiver. The photovoltaic receiver captures a portion of the solar spectrum for conversion to electricity while being transmissive to another portion of the solar spectrum that is absorbed by particles falling through the falling particle receiver.

In another embodiment of the disclosure, a method for capturing solar energy is disclosed that includes illuminating a photovoltaic receiver with concentrated solar energy, capturing a portion of the concentrated solar energy with the photovoltaic receiver to generate electricity, and absorbing a portion of the concentrated solar energy passing through the photovoltaic receiver into a plurality falling particles passing through a thermal receiver.

In another embodiment of the disclosure, a thermal receiver system is disclosed that includes a falling particle thermal receiver comprising an opening for receiving concentrated solar energy, and one or more heliostats for directing concentrated solar energy into the opening. The falling particle thermal receiver is configured to flow particles in a sheet having a thickness of between having a thickness between 0.5 cm and 5 cm.

In another embodiment of the disclosure, a method of capturing solar energy is disclosed that includes directing concentrated solar energy into an opening of a falling particle solar receiver, and heating a falling sheet of particles with the concentrated solar energy passing though the opening.

In another embodiment of the disclosure, a solar receiver is disclosed that includes a thermal receiver and a PV receiver attached to the thermal receiver. The PV receiver includes openings for allowing light to pass through the PV receiver to the thermal receiver, and the PV receiver is cooled by air flowing to the thermal receiver.

In an embodiment of the disclosure, a solar receiver is disclosed that includes a falling particle receiver and a PV receiver attached to the falling particle receiver. Light passing through the PV receiver heats particles passing through the falling particle receiver.

In an embodiment of the disclosure, a solar collection system is disclosed that includes a concentrating solar collection system and a solar receiver for receiving concentrated solar energy from the concentrating solar collection system. The solar receiver includes a thermal receiver and a PV receiver attached to the thermal receiver. The PV receiver includes openings for allowing light to pass through the PV receiver to the thermal receiver, and the PV receiver is cooled by air flowing to the thermal receiver.

In an embodiment of the disclosure, a solar collection system is disclosed that includes a concentrating solar collection system and a solar receiver for receiving concentrated solar energy from the concentrating solar collection system. The solar receiver includes a falling particle receiver and a PV receiver attached to the falling particle receiver. Light passing through the PV receiver heats particles passing through the falling particle receiver.

In an embodiment of the disclosure, a method for capturing solar energy is disclosed that includes capturing a portion of the solar energy by a PV array, and allowing another portion of the solar energy to pass through the PV array to be captured by a solar thermal receiver.

In an embodiment of the disclosure, a method for capturing solar energy is disclosed that includes capturing a portion of the solar energy by a PV array, and allowing another portion of the solar energy to pass through the PV array to heat particles.

An advantage of the present disclosure is to provide a solar power system that combines solar thermal and PV systems.

Another advantage of the present disclosure is that the integration of a volumetric air receiver and a PV system enables cooling of the PV system for higher efficiency operation and preheating of the air before it enters the volumetric receiver. Another advantage of the present disclosure is the radial design of the volumetric receiver surfaces that allows a greater penetration of the solar irradiance, reducing the radiative heat loss near the aperture.

An advantage of integrating a PV array at the aperture (and along the spillage boards surrounding the aperture) of a falling particle receiver system is that electricity and thermal energy can be simultaneously generated. The PV array can have holes or slots to enable a small amount of ambient air flow into and out of the receiver to keep the PV array cooler for improved efficiency. The PV array will also minimize convective and radiative heat losses from within the cavity receiver.

Other features and advantages of the present disclosure will be apparent from the following more detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the disclosure.

DETAILED DESCRIPTION

The present disclosure is directed to a thermal receiver that includes a plurality of thermal panels for capturing solar energy from concentrated sunlight and transferring the captured energy to air. A light focusing device focuses and concentrates light on the thermal receiver to capture heat. Air is pulled through the thermal receiver and heat is transferred from the thermal receiver to the air to generate heated air. The heated air can be used for other applications, such as, but not limited to in a heat exchanger for thermal storage (e.g., in solid media, particles, or molten salt) or electricity generation (e.g., generate steam for Rankine power cycle).

In an embodiment, the light focusing device may be a mirror or array of mirrors. In an embodiment, the thermal or solar receiver is disposed on top of a tower surrounded by a field of heliostats. In another embodiment, the light focusing device may include a dish collector system, where the thermal or solar receiver are attached to a truss and located near the focal point of the dish. In an embodiment, the dish collector tracks the sun during normal operation.

In an embodiment the thermal receiver may include a PV array to generate electricity. The PV array is disposed in the light focusing device. The PV array includes gaps or opening so that light can transmit through to the thermal receiver (the cells themselves can also be transmissive at particular wavelengths) to generate heat. The air pulled through the thermal receiver also serves to cool the PV array so that it can operate more efficiently at lower temperatures.

The present disclosure is also directed to methods for capturing solar energy that includes capturing solar thermal energy and transferring that energy to air. In an embodiment, the method also includes the generation of electrical energy.

The present disclosure is further directed to solar receivers and methods for capturing solar energy using a solar receiver having a veil, curtain or sheet of falling particles that absorb the solar energy.

FIG. 1shows a cross-section of an embodiment of thermal receiver10according to an embodiment of the disclosure. The thermal receiver10includes a heat exchange unit18and a solar collector unit19. The solar collector unit19, which may be referred to as a secondary concentrator, includes a housing24having a conical geometry having a first end20having a first diameter D1that tapers to a second end22having a second diameter D2, where D1>D2. The housing24includes an inner surface24A that directs or channels concentrated sunlight towards the second end22. The inner surface24A that may be any reflective surface to direct the light toward the aperture of the thermal receiver. In such a manner, the shape of the solar receiver10exploits the converging/diverging rays from a dish collector or other solar concentrator. The inner surface24A is cooled by the incoming air flow. In this exemplary embodiment, the solar collector unit19has a conical geometry, however, in other embodiments, the solar collector unit19may have a conical, parabolic, or other geometry that focuses and/or concentrates solar energy into the opening27.

In another embodiment, the solar collector unit19may be omitted. In an embodiment where the solar collector unit19is omitted, a high temperature window (not shown) may be placed over the opening27. The high temperature window is formed of a high temperature, solar spectrum transmissive material, such as, but not limited to quartz.

In this exemplary embodiment, the solar collector unit19includes an optional PV panel or receiver14. The PV receiver14includes a PV cell or array40disposed upon the PV receiver14. In this exemplary embodiment, the PV array40covers the surface of the PV receiver14. In other embodiments, the PV receiver may include one or more PV arrays40that may cover all or a portion of the surface of the PV receiver or be otherwise integrated into the PV receiver14. In other embodiments, the PV receiver14may be omitted. The PV receiver14is a transmissive, semiconductor structure that allows thermal spectrum to pass through while capturing other portions of the solar spectrum for conversion to electricity. In an embodiment, the percentage of light that passes through the PV receiver14to the thermal receiver can vary between 10%-90% depending on the need and value for thermal storage. In this exemplary embodiment, the PV receiver14is shown conforming to the housing24. In other embodiments, the PV receiver14may be separated from or partially separated the housing24to allow air to pass between the PV receiver14and the housing24.

The PV receiver14includes a plurality of openings42that allow for concentrated light and pass through and be absorbed the heat exchange unit18thereby heating the thermal receiver12. Note that this light is in addition to the light passing through the PV receiver14. The openings42also allows for air to pass through and cool the PV receiver14, increasing the efficiency thereof. In this exemplary embodiment, the openings are square, however, in other embodiments, the openings42may be, but are not limited to circular, oval, square, and rectangular shapes.

The PV receiver14includes electrical leads, conductors, connections and other elements (not shown) that collect electrical energy from the PV receiver14. These components are not shown for simplicity however, the structure and function thereof are well understood in the art. In another embodiment, the PV receiver14may have fins or other heat exchange members extending from the rear side of the PV array40to improve cooling of the PV array.

In other embodiments, the solar collector unit19may include a high temperature window similar in shape and in place of the PV receiver14. The high temperature window may be made of a high temperature, solar transmissive material, such as, but not limited to quartz. When the thermal receiver10includes the PV receiver14, the thermal receiver10may be referred to as a solar receiver. The combination of the thermal receiver10and PV receiver14allows the solar receiver to utilize the full spectrum of solar irradiance to generate electricity and heat.

The heat exchange unit18includes a housing26. The housing26includes an opening27that corresponds to the second end22of the solar collector unit19. The opening27is positioned so as to also be or is proximate to the focal plane for concentrated sunlight that has been focused upon the thermal receiver10.

The heat exchange unit18further includes a heat absorbing unit28and heat transfer zone30disposed within the housing26. The heat absorbing unit28includes a plurality of radially extending heat absorbing bodies or fins32disposed around passageway34. The fins32have inner or passageway surfaces33that define passageway34. The fins32also define radial spaces36between adjacent fins32. The passageway34and the radial spaces36enable air to flow between the opening27and the collection space38while in contact with the fins3, enabling heat to be transferred to the air from the fins. Heat is also transferred to the air from the fins32while the air is in the collection space38.

The fins32are formed of a high temperature material such as metal, ceramic and cermet. In an embodiment, the fins32may be formed of a metal, such as, but not limited to stainless steel, Inconel 625, or Haynes 230 The fins32may have surfaces or coatings on the fin surfaces33and/or surfaces facing adjoining fins that have features or perforation to enhance the penetration and/or trapping of light and to enhance the heat transfer to the flow air. The fins32are oriented to allow deep penetration of the light rays for volumetric heat absorption while minimizing re-radiation (thermal emittance) out of opening27, and in particular back to the PV receiver14.

FIG. 1A illustrates an embodiment of a fin62according to an embodiment of the disclosure. In this exemplary embodiment, the fin62includes an internal channel or micro-channel64in fluid connectivity with a secondary fluid system66for the heating of a secondary fluid, such as, but not limited to gases, liquids, and supercritical fluids. The micro-channel64has an input68and output70for receiving and outputting a fluid from the micro-channel64. In other embodiments, the fin62may have one or more channels or micro-channels. In this exemplary embodiment, the input68is shown providing fluid to a portion of the fin62closest to the opening27. For example, the secondary fluid may be a gas such as, but not limited to helium: a liquid such as, but not limited to water, liquid metals, molten salts, hydrocarbons; and supercritical fluids such as, but not limited to supercritical CO2. In another embodiment, the fin62may include one or more cavities for containing a secondary fluid.

The heat transfer zone30includes open space or airways in contact with the fins32and includes passageway34, radial spaces36between the fins32, and a collection space38. In this exemplary embodiment, the passageway34has a conical geometry. In another embodiment, the passageway34may have other geometries, such as, but not limited to cylindrical or tubular with a circular, square, hexagonal or other cross-section. The passageway34includes opening34athat is fluidly connected to opening27. In this exemplary embodiment, the opening34asmoothly transitions to opening27of housing26so as to allow light entering opening27to be unobstructed in penetrating into passageway34. The passageway also includes exit opening35. The passageway34is defined by fin surfaces33of fins32. The conical geometry of the passageway34provides a light-trapping geometry with low radiative view factors and thermal emittance back to the collector support panel14and to the environment.

As discussed above, the passageway34receives air from the opening27and allows for that air to either flow into the radial spaces36between the fins32or to flow though the passageway34and into the collection space38via an exit opening35. The radial spaces36are also open to the collection space38so as to allow the air flowing in the radial spaces36to flow into the collection space38. The air flowing through the passageway34and is heated by the fin surfaces33. The passageway34allows for focused sunlight passing through the opening27to be absorbed by the fin surfaces33as the sunlight diverges and travels down the conical passageway34.

Also as discussed above, the collection space38is a volume that receives air from the passageway34and radial spaces36. The collection space38is fluidly connected to an outlet39that allows air to exit the collection space38. In such a manner, air is drawn into the opening27, heated by fins32that have been heated by concentrated sunlight, collected in the collection space38and provided to another system via the outlet39that utilizes the heated air for a secondary purpose. In another embodiment, a fan or other air moving device or system may be connected to the outlet39to assist the flow of air through the thermal receiver10. The heated air may be used in a secondary system, such as, but not limited to systems to heat thermochemically reactive particles, drive power generation equipment, heat secondary fluids, heat particles from a falling particle receiver, or heat any other working fluid for thermal or electrical power generation.

In an embodiment, the thermal receiver10can translate along the axis of the collector focal length X to allow variable power to reach the thermal receiver12and PV receiver14. This may be important when the direct normal irradiance (DNI) is changing and/or when more or less thermal capture and/or storage is desired relative to PV power generation. For example, during off-peak, low-load times, it may be more desirable to generate thermal energy for storage rather than electricity. Then, the PV receiver12would be moved further away from the thermal receiver12(and focal plane) so that more of the concentrated solar flux can reach the thermal receiver10. In an embodiment, the thermal receiver10is a component of a solar collection system that includes a mirror or array of mirrors to focus and concentrate sunlight onto the receiver.

FIG. 1Billustrates a thermal receiver system (system)150according to an embodiment of the disclosure. As can be seen inFIG. 1A, the system150includes a thermal receiver151mounted atop a tower152. The thermal receiver151receives ambient air160and produces heated air162. The system also includes heliostats153that direct concentrated solar light156at the thermal receiver151. In this exemplary embodiment, four heliostats are shown, however, in other embodiments, the system150may include one or more heliostats. The thermal receiver151may be the receiver shown inFIG. 1and described above. Other embodiments may include the thermal receiver shown inFIG. 2and described below.

FIG. 2illustrates an embodiment of a solar receiver100according to the present disclosure. The solar receiver100includes a thermal receiver112and a PV receiver114. The thermal receiver112includes a heat exchange unit118and a solar collector unit119. The solar collector unit119, which may be referred to as a secondary concentrator, has a housing124having a conical geometry having a first end120having a first diameter D3that tappers to a second end122having a second diameter D4, where D3>D4. The housing124includes an inner surface124A that directs or channels concentrated sunlight towards the second end122. The inner surface124A may be any reflective surface to direct the light toward the aperture of the thermal receiver. The inner surface124A will be cooled by the incoming air flow. In another embodiment, the solar collector unit119may have a conical, parabolic, or other geometry that focuses and/or concentrates solar energy into the opening127.

In another embodiment, the solar collector unit119may be omitted. In an embodiment where the solar collector unit119is omitted, a high temperature window (not shown) may be placed over the opening127. The high temperature window is formed of a high temperature, solar spectrum transmissive material, such as, but not limited to quartz.

The heat exchange unit118includes a housing126. The housing126includes an opening127that corresponds to the second end122of the solar collector unit119. The opening127is positioned so as to also be or is proximate to the focal plane for concentrated sunlight that has been focused upon the solar receiver100.

The heat exchange unit118further includes a heat absorbing unit128and heat transfer zone130disposed within the housing124. The heat transfer zone130includes open space or airways in contact with the fins132and includes a passageway134, radial spaces136and a collection space138. In this exemplary embodiment, the passageway134has a cylindrical geometry. In another embodiment, the passageway34may have another geometry, such as, but not limited to conical. In this exemplary embodiment, the passageway134has a circular cross-section, however, in other embodiments the cross-section may be, but is not limited to circular, square, and hexagonal. The passageway134is fluidly connected to opening127and includes exit opening135. The passageway134is defined by fin surfaces133of fins132. The cylindrical geometry of the passageway134provides a light-trapping geometry with low radiative view factors and thermal emittance back to the PV receiver114and to the environment.

The passageway134receives air from the opening127and allows for that air to either flow into the radial spaces136between the fins132or to flow though the passageway134and into the collection space138via an exit opening135. The radial spaces136are also open (not shown) to the collection space138so as to allow the air flowing in the radial spaces136to flow into the collection space138. The air flowing through the passageway134is heated by the fin surfaces133. The passageway34allows for focused sunlight passing through the opening127to be absorbed by the fin surfaces133as the sunlight diverges and travels down the conical passageway134.

The heat absorbing unit128includes a plurality of radially extending bodies or fins132disposed around passageway134. As discussed above, the fins132have fin surfaces133and radial spaces136between adjoining fins that allow for the passage of air from the passageway134to the collection space138. The fins132are formed of a high temperature material such as metal, ceramic and cermet. In an embodiment, the fins132may be formed of a metal, such as, but not limited to stainless steel, Inconel 625, or Haynes 230. The fins132may have surfaces or coatings on the fin surfaces133and/or surfaces facing adjoining fins that have features or perforation to enhance the penetration and/or trapping of light and to enhance the heat transfer of the flow air. The fins132are oriented to allow deep penetration of the light rays for volumetric heat absorption while minimizing re-radiation (thermal emittance) out of opening127, and in particular back to the PV receiver114. In this exemplary embodiment the fins132include a leading edge137. In an embodiment, the leading edge may be light absorbing and/or include a light absorbing coating. In another embodiment, the leading edge may be omitted and the surface133may taper to the opening127. In such a manner, the shape of the heat absorbing units exploits the converging/diverging rays from a dish collector or other solar concentrator.

As discussed above, the collection space138is a volume that receives air from the passageway134and radial spaces136. The collection space138is fluidly connected to an outlet139that allows air to exit the collection space138. In such a manner, air is drawn into the opening127, heated by fins132that have been heated by concentrated sunlight, collected in the collection space138and provided to another system via the outlet139that utilizes the heated air for a secondary purpose.

In another embodiment, the fins132may include channels or micro-channels in fluid connectivity with secondary systems for the heating of a secondary fluid, such as, but not limited to gases, liquids, and supercritical fluids. For example, the secondary fluid may be a gas such as, but not limited to helium; a liquid such as, but not limited to water, liquid metals, molten salts, hydrocarbons; and supercritical fluids such as, but not limited to supercritical CO2.

As discussed above, the solar collector unit119concentrates sunlight into the opening127. In this exemplary embodiment, the solar collection unit includes an end substrate or cap131supported by the housing124. The end cap131has a central opening137. In an embodiment, all or part of the end cap131may be translucent or allow for the transmittance of light. In an embodiment, the end cap131may have one or more PV arrays integrated with or attached to the end cap131. In another embodiment, the end cap131may have one or more openings. The PV receiver114is supported by the end cap131in the central opening.

The PV receiver114includes a PV cell or array140disposed upon the surface of the PV receiver114. In other embodiments, the PV receiver114may include one or more PV arrays140that may cover all or a portion of the surface of the PV receiver114. Electrical connections to and from the PV receiver114are not shown for clarity, however, the structure and function thereof are well understood in the art. The PV receiver114allows for at least a portion of light incident to the PV array to pass through the PV receiver114and thus be collected and used for thermal heating in the thermal receiver112. In an embodiment, the percentage of light that passes through the PV array to the thermal receiver can vary between 10%-90% depending on the need and value for thermal storage.

The PV receiver114includes openings142. The openings142allow for concentrated light and air to pass through the PV array140and be collected and used for thermal heating in the thermal receiver112. In this exemplary embodiment, the openings142are slots and have a rectangular cross-section, however, in another embodiment, the openings42may be of any suitable geometry, such as, but not limited to circular, square, oval, and rectangular. The air passing through the openings142of the PV receiver112cool the PV array, increasing efficiency thereof. In this exemplary embodiment, the PV receiver114includes heat transfer members143that extend from the PV receiver towards the opening127that cool the PV receiver114by transferring heat from the PV receiver114to air passing through the solar collection unit19to the thermal receiver112.

In an embodiment, the thermal receiver112and PV receiver114can translate along the axis of the collector focal length X to allow variable power to reach the thermal receiver112and PV receiver114. This may be important when the direct normal irradiance (DNI) is changing and/or when more or less thermal capture and/or storage is desired relative to PV power generation. For example, during off-peak, low-load times, it may be more desirable to generate thermal energy for storage rather than electricity. Then, the PV receiver112would be moved further away from the thermal receiver112(and focal plane) so that more of the concentrated solar flux can reach the thermal receiver112.

FIGS. 3 and 4illustrate an embodiment of a solar receiver300according to another embodiment of the disclosure. The solar receiver300includes a housing310having a window312. The housing310surrounds a an interior space or cavity311. The window312allows for concentrated sunlight to enter the cavity311. In this exemplary embodiment, the window312includes a PV cell or array314disposed upon the surface thereof. In another embodiment, the window312may include one or more PV cells and/or arrays. The PV array314is a transmissive, semiconductor structure that allows thermal spectrum to pass through while capturing other portions of the solar spectrum for conversion to electricity. In an embodiment, the percentage of light passing through the PV array314can vary between 10%-90% depending on the need and value of the remaining light spectrum passing through the PV array314.

In another embodiment the window312may not include a PV array314, and may be formed of a high temperature, solar spectrum transmissive material, such as, but not limited to quartz. In this exemplary embodiment, the window312may have a flat front facing surface as shown inFIGS. 3 and 4. In another embodiment, the front facing surface of the window312may be not be flat, but may be undulating, wavy or of other light trapping or guiding geometries, which may reduce the reflective losses relative to a flat window. For example,FIG. 3Aillustrates an embodiment of a window312A having an undulating front facing surface that includes a plurality of parallel open concave channels. In an embodiment, the open concave channels have a channel width of between about 2 cm and 50 cm. In this exemplary embodiment, the window312A is formed of a plurality of half-cylinders of quartz tubes330having the concave side facing the incoming solar radiation. In an embodiment, the quartz tubes may have a diameter of between about 2 cm and 50 cm. In another embodiment, the quartz tubes may have a diameter of between about 5 cm and 50 cm. In yet another embodiment, the quartz tubes may have a diameter of between about 5 cm and 20 cm. In other embodiments, the undulating window312A may be formed of a single cast quartz panel or from other joined structures that create a light trapping or guiding surface. In other embodiments, the window312may be omitted and an opening remaining in its place. In this exemplary embodiment, the window312is solid. In other embodiments, the window312and/or PV array314may include holes, slots, gaps or other openings for allowing air and light to pass through and cool the window312an/or the PV array314. In another embodiment, the window312may be deleted and replaced with an open space.

As can further be seen inFIGS. 3 and 4, the solar receiver (receiver)300further includes an opening316for receiving a plurality of particles or particle steam into a particle heating zone318within the housing310. In this exemplary embodiment, the opening316is a rectangular opening or slot that allows for the particles to fall through the receiver in a thin veil, sheet or curtain of particles320. The thickness of the particle sheet or curtain320can range from about 0.5 cm to about 20 cm, depending on the desired mass flow rate and opacity of the particle curtain, which impact particle temperature rise and thermal efficiency. In another embodiment, the thickness of the particle sheet or curtain320may range from about 0.5 cm to about 5 cm The solar receiver300further includes a particle collector and exit (not shown) where the particles are collected and exit from the particle heating zone318.

The particles may be, but are not limited to silica sands, ceramic particles, sintered bauxite, pervoskites, and thermochemically reactive particles (e.g., particles that can undergo a reduction/oxidation reaction for increased heat capacitance and heating of the working fluid.

Solar spectrum (light) passing through the window312, PV array314and openings (when present) are used to illuminate and heat falling particles320. A benefit of this design is that the window312and PV array314serve to mitigate convective and radiative heat loss from within the cavity311. Also, the air movement within the cavity311from the falling particles and air passing through the PV array314can serve to cool the PV array. The ambient air that enters the cavity311may also leave the cavity311through the openings in the PV array or become entrained with the particles. In other embodiments, air may also be deliberately blown along the window or PV array to cool the window or PV array.

Particles heated in the portion of the cavity311that the particles pass through or particle heating zone318may be used for thermochemical processes. For example, the particles may be reduced and absorb extra energy beyond the sensible heating energy required to raise the temperature of the particle. The particles could then be later oxidized by an air stream to recoup the sensible and thermochemically stored energy.

FIG. 5is an illustration of another thermal receiver system (system)550system according to another embodiment of the disclosure. As can be seen inFIG. 5, the system550includes a thermal receiver551mounted atop a tower552. The thermal receiver551is as described above in discussingFIGS. 3 and 4. The thermal receiver551receives a particulate material via particulate material input stream560, and discharges heated particles via particulate material output stream562. The system550also includes heliostats553that direct concentrated solar light556at the thermal receiver551. In this exemplary embodiment, four heliostats are shown, however, in other embodiments, the system550may include one or more heliostats.

In other embodiments, concentrated sunlight may be directed and focused upon the solar receiver300by known solar concentrator systems and methods, such as, but not limited to the use of heliostats, parabolic mirrors, or other reflecting elements. The focal plane is located at the aperture or opening of the receiver (not shown, but as shown and described regardingFIGS. 3 and 4) into the cavity or particle heating portion of the solar receiver300. The incident light converges to this plane and then diverges within the cavity.

The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the appended claims. It is intended that the scope of the invention be defined by the claims appended hereto. The entire disclosures of all references, applications, patents and publications cited above are hereby incorporated by reference.

In addition, many modifications may be made to adapt a particular situation or material to the teachings of the disclosure without departing from the essential scope thereof. Therefore, it is intended that the disclosure not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this disclosure, but that the disclosure will include all embodiments falling within the scope of the appended claims.