Patent application title: DEVICE FOR HARNESSING SOLAR ENERGY WITH VAPOR INSULATING HEAT TRANSFER CORE
Mark W. Miles (Atlanta, GA, US)
IPC8 Class: AF24J232FI
Class name: Solar heat collector with means to convey fluent medium through collector having evaporator and condenser sections (e.g., heat pipe)
Publication date: 2011-05-26
Patent application number: 20110120451
A solar collector is provided, in one embodiment. The solar collector
comprises a heat core to convert incident radiation into heat; a wicking
layer spaced from the heat core to absorb infrared radiation emitted by
the heat core due to the conversion of incident radiation into heat; an
inlet to introduce a heat transfer fluid into the wicking layer; wherein
the absorption of the infrared radiation is by the heat transfer fluid in
the wicking layer and causes a portion of the heat transfer fluid to
enter into a vapor phase thereof which propagates into the heat core
where it undergoes heating; and an outlet to transport the heated vapor
phase of the heat transfer fluid out of the collector.
1. A method for heating a heat transfer fluid, comprising: exposing a
heat core to incident radiation to cause heating of said heat core,
whereupon the heat core emits infrared radiation; introducing a heat
transfer fluid into a wicking layer spaced from the heat core to absorb
the infrared radiation emitted by the heat core, whereupon at least some
of the heat transfer fluid is converted into a vapor that enters the heat
core; heating the vapor in the heat core; and extracting the heated vapor
to perform work.
2. The method of claim 1, wherein heating the vapor comprises superheating the vapor.
3. The method of claim 1, further comprising controlling a rate at which the heat transfer fluid is introduced into the wicking layer to ensure wetness of all portions of the wicking layer.
4. A solar collector, comprising: a heat core to convert incident radiation into heat; a wicking layer spaced from the heat core to absorb infrared radiation emitted by the heat core due to the conversion of incident radiation into heat; an inlet to introduce a heat transfer fluid into the wicking layer; wherein the absorption of the infrared radiation is by the heat transfer fluid in the wicking layer and causes a portion of the heat transfer fluid to enter into a vapor phase thereof which propagates into the heat core where it undergoes heating; and an outlet to transport the heated vapor phase of the heat transfer fluid out of the collector.
5. The solar collector of claim 4, wherein heat transfer fluid lost from the wicking layer through conversion into the vapor phase is replaced through a capillary action that pumps more heat transfer fluid into the wicking layer through the inlet.
6. The solar collector of claim 5, which is tuned in terms of ability of the heat core to convert incident radiation into heat, wicking capacity of the wicking layer, properties of the heat transfer fluid, separation distance between the heat core and the wicking layer, and cross-section of the inlet to ensure that all portions of the wicking layer remain wet with heat transfer fluid during operation.
7. The solar collector of claim 4, further comprising a housing for the heat core, and the wicking layer lines an internal surface of the housing.
8. The solar collector of claim 7, wherein the housing is planar.
9. The solar collector of claim 7, wherein the housing is cylindrical.
10. The solar collector of claim 7, wherein a portion of the housing that is operatively exposed to incident radiation in the form of solar flux is transparent to the incident radiation thereby to define a window.
11. The solar collector of claim 10, wherein said window is treated with an anti-reflective material.
12. The solar collector of claim 4, wherein the wicking layer comprises a porous material.
13. The solar collector of claim 12, wherein the porous material comprises film laced with a network of continuous interconnected passages to create a wicking action through capillary forces.
14. The solar collector of claim 4, wherein the wicking layer comprises a surface structured material.
15. The solar collector of claim 14, wherein the surface structured material comprises surface grooves to facilitate a capillary pumping action.
16. The solar collector of claim 5, wherein the wicking material facing the housing is transparent to visible light and has an index of refraction that is matched to that of the heat transfer fluid.
11. The solar collector of claim 4, wherein the heat core comprises a thermally conducting metal or a carbon foam matrix.
18. The solar collector of claim 17, wherein the heat core is treated to make it light absorbing.
19. The solar collector of claim 4, wherein the heat core comprises a thermally conductive fill material having interstitial spaces to promote conductive heat transfer to the vapor phase of the heat transfer fluid.
20. The solar collector of claim 17, wherein the heat core comprises an axial passage extending through the fill material.
21. The solar collector of claim 18, wherein the heat core comprises a pair of metal plates each comprising interstitial spaces to promote conductive heat transfer to the vapor phase of the heat transfer fluid, the fill material being located within the metal plates.
22. The solar collector of claim 4, wherein the heat core comprises a non-porous hollow cylinder filled with a porous material having interstitial spaces to promote conductive heat transfer to the vapor phase of the heat transfer fluid.
23. The solar collector of claim 22, wherein the hollow cylinder is metallic and is able to withstand pressures at least 20 bar.
24. The solar collector of claim 23, wherein the heat core comprises an egress end that is hermetically sealed with the outlet.
25. The solar collector of claim 23, wherein the heat core comprises an ingress end through which the vapor phase of the heat transfer fluid enters the heat core, said ingress end being plugged by a capillary pump.
26. The solar collector of claim 25, wherein the capillary pump comprises a porous material designed to perform a pumping action on the heat transfer fluid due to variations in pore size.
27. The solar collector of claim 24, wherein the porous material comprises at least two layers in contact with each other, each layer having pores of a different size.
28. An energy system, comprising: an array of solar collectors; a first heat transfer loop coupled to the array to provide a recirculation path for heated heat transfer fluid from and to the array; and a second heat transfer loop comprising at least one heat exchanger to extract heat from the heated heat transfer fluid in the first heat transfer loop to perform work; wherein at least one solar collector, comprises: a heat core to convert incident radiation into heat; a wicking layer spaced from the heat core to absorb infrared radiation emitted by the heat core due to the conversion of incident radiation into heat; an inlet to introduce a heat transfer fluid `into the wicking layer; wherein the absorption of the infrared radiation is by the heat transfer fluid in the wicking layer, and causes a portion of the heat transfer fluid to enter into a vapor phase thereof which propagates into the heat core where it undergoes heating; and an outlet to transport the heated vapor phase of the heat transfer fluid out of the collector.
29. The energy system of claim 28, wherein the first heat transfer loop comprises an energy accumulation device to store heat from the heated heat transfer fluid in the first heat transfer loop.
30. The energy system of claim 28, wherein the energy accumulator selectively adds heat to the heated heat transfer fluid in the first heat transfer loop.
31. An energy system, comprising: an array of solar collectors; a heat transfer loop coupled to the array to provide a recirculation path for heated heat transfer fluid from and to the array; and at least one heat exchanger positioned within the heat transfer loop to extract heat from the heated heat transfer fluid; wherein at least one solar collector in said array comprises: a heat core to convert incident radiation into heat; a wicking layer spaced from the heat core to absorb infrared radiation emitted by the heat core due to the conversion of incident radiation into heat; an inlet to introduce a heat transfer fluid into the wicking layer; wherein the absorption of the infrared radiation is by the heat transfer fluid in the wicking layer, and causes a portion of the heat transfer fluid to enter into a vapor phase thereof which propagates into the heat core where it undergoes heating; and an outlet to transport the heated vapor phase of the working fluid out of the collector.
32. The energy system of claim 31, wherein the heat transfer loop comprises an energy accumulation device to store heat from the heated working fluid in the first heat transfer loop.
33. The energy system of claim 31, wherein the energy accumulator selectively adds heat to the heated working fluid in the heat transfer loop.
 This application is a continuation-in-part of U.S. Ser. No.
12/623,337 and U.S. Ser. No. 12/830,273.
 Embodiments of the invention relate to devices and methods to harness solar radiation as an energy source.
 Solar collectors are devices designed to convert solar radiation into heat that can be used to perform work.
 One new design of a solar collector was described in co-pending U.S. patent application Ser. No. 12/623,337, and U.S. Ser. No. 12/830,273 the specifications of which are hereby incorporated by reference. The improved performance of this collector derives from the fact that a light absorbing heat transfer core (HTC) resides within the volume of an infrared absorbing heat transfer or working fluid, including but not limited to water or other synthetic fluids similar in composition to the "Dowtherm" line of heat transfer fluids manufactured Dow Chemical Corporation. A primary requirement of the fluid is that it be substantially transparent in the visible region of light, and highly absorbing in the infrared region. The HTC includes a light absorption component that converts incident solar flux into heat, which is transferred to the heat transfer or working fluid as it passes towards and through the body of the HTC. Heat that radiates from the HTC in the form of infrared radiation is absorbed by the working fluid and thus prevented from escaping to the ambient environment. The lower radiative losses result in overall improved performance of the collector. A design for a solar thermal energy conversion system was described in co-pending U.S. patent application Ser. No. 12/396,336 which is hereby also incorporated by reference.
BRIEF DESCRIPTION OF THE DRAWINGS
 FIG. 1 of the drawings shows two plots which illustrate the infrared absorption properties of water.
 FIG. 2 of the drawings illustrates a prior art embedded absorber solar collector, and a side view of an embedded absorber solar collector integrated with a regenerator and a condenser.
 FIG. 3 of the drawings shows a side view of both a planar and a cylindrical solar collector containing a vapor insulated heat transfer core with low pressure vapor output in accordance with embodiments of the invention.
 FIG. 4 of the drawings shows a side view of both a planar and a cylindrical solar collector containing a vapor insulated heat transfer core with high pressure vapor output, in accordance with embodiments of the invention.
 FIG. 5 of the drawings shows a schematic diagram for a thermal energy conversion system incorporating a solar collector array with low pressure vapor output.
 FIG. 6 of the drawings shows a schematic diagram for a thermal energy conversion system incorporating a solar collector array with high pressure vapor output, in accordance with one embodiment of the invention.
 FIG. 7 of the drawings shows a schematic diagram for a data processing facility supplied by cooling and heating resource from a solar thermal energy conversion system, in accordance with one embodiment of the invention.
 FIG. 8 of the drawings show a schematic diagram for a solar thermal application dedicated solely to the generation of a cooling resource, a heating resource, or a combined cooling and heating resource, in accordance with one embodiment of the invention.
 In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the invention. It will be apparent, however, to one skilled in the art that the invention can be practiced without these specific details.
 Reference in this specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. Moreover, various features are described which may be exhibited by some embodiments and not by others. Similarly, various requirements are described which may be requirements for some embodiments but not others.
 Plot 100 of FIG. 1 shows the spectrum of radiation emitted by the sun that strikes the earth's surface. In general it is useful to absorb and convert as much of this energy as possible. Plot 100 illustrates that the bulk of the received energy from the sun resides between the wavelengths of 200 nm to 2400 nm. Plot 102 illustrates the absorption spectrum of water, which is one candidate heat transfer fluid. As can be seen, water is extremely transparent to light in the wavelengths from 200 nm to 1000 nm. As the wavelength increases, the absorption of incident light increases dramatically. This property may be used to advantage, and there is evidence to suggest that other heat transfer fluids exhibit similar performance.
 Referring now to FIG. 2, solar collector 202 is shown being illuminated by incident solar flux 200. This light is transmitted into the interior where it is absorbed by porous heat transfer core 204. The heat transfer core 204, because it has a light absorption component on its surface, subsequently rises in temperature due to absorption of the incoming light. Incoming heat transfer fluid 214, which could be water, for example, flows along the exterior of the heat transfer core 204 in the direction indicated by the solid arrows 207 and 210. As it passes through the body heat transfer core 204, it rises in temperature via conduction of heat from the heat transfer core 204. The heated fluid 214 then passes out of the solar collector 202 through the interior of the heat transfer core 204 indicated by dashed arrows 212. The output heated fluid 216, can be used to provide useful heat to external components which are in fluid communication with the collector 202.
 FIG. 2 also shows a conceptual view another collector 220. The collector 220 includes an exterior housing 238 which contains a heat transfer core 236, and is mechanically and thermally bonded to regenerator/condenser assembly 228. In operation, cooled vapor 222, from an exterior energy thermal energy conversion system, propagates in the direction indicated by dashed arrow 224. As it passes through this passage it gives up heat to the assembly and is cooled. After it makes the turn at 226, it continues to propagate along in the direction indicated by line 230, which represents condensed fluid. The bottom exterior surface of regenerator/condenser assembly 228 is exposed to the ambient environment. This provides a means to condense the incoming vapor 222 by providing a thermally conducting path to the environment. Thus heat is rejected to the environment enabling the condensation. Gap 240 provides thermal isolation between the incoming vapor 222, and the condensed fluid 230. Capillary pump 232 provides a means for pumping the condensed fluid 230 along path 234, into the body of the heat transfer core 236, where it is subsequently heated into a vapor 242, which can then be utilized by an external thermal energy conversion system.
 FIG. 3 shows a planar solar thermal collector 300, containing a heat transfer core (HTC) 310 similar in structure to that which was described in U.S. patent application Ser. No. 12/623,337, and shown in FIG. 2. In one embodiment, the HTC 310 may comprise a monolithic thermally conducting metal (copper or aluminum for example) or carbon foam matrix whose outer surface, or entire surface, has been coated or treated with a thin film or stack of thin films such that light that is incident on the outer surface is completely or substantially absorbed. In this embodiment the material may be substantially porous with a pore size and density to optimize the transfer of heat via conduction from the material of the HTC 310 to any vapor which is passing through it, while optimizing the pressure drop through the HTC 310. The light absorbing surface treatment may also be in the form of a chemical etching process which produces a microscopically textured or roughened surface whose geometry encourages the absorption of incident light. In another embodiment the core may be in the form of a bonded pair of plates whose surface has been perforated via machining or chemical means, to produce a network of through holes, and whose interior is filled with a highly thermally conductive foam material, as described above, or with a metal wire or fiber mesh, or a structured metal fin array which is substantially porous. Many alternative fill materials and structures may be utilized. The porosity of the core and its fill material is determined by the desired heat transfer coefficient, between the core and vapor propagating inside, and the desired characteristics including pressure drop and velocity of any vapor transported through the core. The porosity may vary in the range of 20-80% more or less. The pore size has a similar impact on these characteristics and may vary in the range of tens to hundreds of microns. The interior of the core may be hollow and provide a space which could be at least several times the size of the pores in the core. The light absorbing coating on the HTC should serve to minimize emission in the near and mid infrared regions as well. HTC 310, is illuminated by solar flux 302 emitted by the sun. Transparent front plate 304 allows for the passage of solar flux 302, so that it may be absorbed by the HTC 310. It comprises a material which is highly transparent to visible light, such as glass or other suitably transparent and environmentally robust material. Transparent front plate 304 is hermetically bonded to housing 306 such that it can sustain a vacuum and prevents the passage of gasses in the environment into the housing 306, and the passage of gasses from the interior of the housing 306 to the environment. The primary characteristics of the housing 306 are that it preclude the passage of such gasses and vapors, be mechanically robust for exposure to an external environment, and be thermodynamically compatible with the transparent front plate 304. Transparent front plate 304 may also have resident on one or both of its surfaces an antireflective coating one type or another, of which there are many designs known to those skilled in the art of designing and manufacturing antireflective coatings. Many materials including metals, and fiberglass or carbon composites suitably coated with barrier materials, can provide this function. The transparent front plate 304 and housing 306 have external conduits 318 and 312 which provide a means for the input of condensed heat transfer/working fluids (HTF) 322, and output of heated vaporized HTF 320, respectively. Additionally the transparent front plate 304 and housing 306 have a porous or surface structured wicking material 308, resident on the entire extent of their interior surface. This material is dimensioned and structured so as to act like a capillary wick for the HTF which resides within it.
 A porous wicking material means a film whose interior is laced with a network of continuous interconnected passages to allow for the pumping, via capillary forces, and propagation of the HTF. A surface structured wicking material has a surface (an array of microscopic grooves for example) which has been defined to promote the capillary pumping and propagation of HTF along the interior surface. Many variations on porous and surface wicks are possible and well understood by those skilled in the art of fabricating capillary wicks, especially for use in heat pipes. Characteristics of the wick on the interior surface of the front plate include high transparency to visible light, and a refractive index close to that of the HTF to be utilized. One candidate is Teflon, but there are a variety of plastics and oxide materials which may suffice. Characteristics of the wick on the interior surface of the housing do not require transparency to visible light. The transparent front plate 304, housing 306, HTC 310, surface structured wicking material 308, and conduits 312,318 collectively define a planar solar collector. Planar means that the lateral dimensions (as extending left to right on the page, and into the page) are substantially larger than the vertical (thickness) dimension (extending top to bottom on the page). Typical dimension are in the range of several to tens of centimeters for the thickness, and 0.5 to 1 meter for the lateral dimension. As described within the aforementioned patent applications, some kind of interior support structure array may be required if the collector is to operate at interior pressures which are sub-atmospheric. The overall design goal of such supports is to minimize the transfer of heat via conduction from the core to the transparent front plate, and housing 306, while providing mechanical support between these two components to withstand the pressure of the external atmosphere.
 The light from the solar flux 302, which is absorbed by the HTC 310, is subsequently converted into heat, thus the temperature of the core rises. Subsequently heat radiated from the core in the form of infrared radiation 314, is incident on the HTF which is resident within or on the surface of the interior wick. Because the heat HTF absorbs in the infrared, the temperature of the HTF is subsequently increased and results in evaporation of the HTF. HTF input conduit 318, is in fluid communication with the wick. Thus as the HTF is evaporated it is replaced by additional HTF supplied via the capillary forces which act on the HTF to pump it through the wick. The wick is designed to have a pumping capacity which is at least equal to, though nominally somewhat exceeds, the rate at which evaporation extracts the fluid under normal operating conditions. The rate of evaporation is determined by a number of factors including the initial collector internal pressure, the characteristics of the core and the wick, the intensity of the solar flux, as well as the temperature of the condensed HTF entering the collector among others. As a consequence it may be necessary to constantly modify the incoming flow rate of HTF 322, in order to prevent surface structured wicking material 308 from drying out (at high input energy levels) or flooding (at low input energy levels), or if other internal or external characteristics of the collector change over time.
 The HTF vapor 316 emerges from the wick at a temperature which is slightly above the saturation temperature of the HTF. Due to the resulting increase in pressure the HTF vapor flows towards the HTC 310. The vapor undergoes a small amount of superheat due to the infrared radiation 314 it absorbs, and as it passes through the body of the core undergoes more substantial superheating due to further absorption of radiation and conduction to body of the core. The result is a superheated vapor 320, which is output via conduit 312, and which can be subsequently utilized in a solar thermal energy conversion system to be described later in the specification. Typical pressure of the superheated vapor 320 is less than 1 bar under normal external environmental temperatures.
 Overall this collector exhibits superior operation and lower thermal losses because the heat, absorbed by the HTF in the wick, is transferred to the wick via evaporation. In the aforementioned applications, and the collector 202 shown in FIG. 2, this heat transfer is done via fluidic transfer from the wick to the core. Because HTF vapor has a much lower thermal conductivity, lower thermal losses can be sustained at lower flow rates. The end result is the collector is capable of achieving higher outlet temperatures for a given amount of incident solar flux.
 Referring again to FIG. 3, another solar collector 330 is shown which is identical in function and operation to the collector 200. In this case, however, a cylindrical geometry is shown which can be useful for applications wherein concentrating optics is used to increase the total flux incident on the collector. Transparent cylinder 334, like the transparent front plate of collector 300, is made from a material such as glass which could be strengthened by chemical or thermal treatment, and may have antireflective coatings on its surfaces. For purposes of this illustration one end of the cylinder is shown to be hermetically sealed. In certain applications one or both ends of the cylinder may not be sealed as the cylinders may be connected in a series fashion to create a collectively longer cylinder. The interior of cylinder 334 is also lined with a transparent wicking material 336, which is in fluidic communication to incoming condensed HTF 332. Suspended in the center of the cylinder is porous absorber core 338 which comprises materials which are highly thermally conductive, have internal pore sizes ranging from tens to hundreds of microns, and are also treated so that the exposed surface, or perhaps the entire porous matrix, is highly absorbing to visible light as in collector 300. Alternative means for achieving porosity, such as the perforation described in collector 300, may also apply in this configuration. The core may be hollow to provide supplemental space for vaporized HTF 342, to be output with relative ease. Similarly the interior may also contain a heat conducting fill material as described in collector 300. Similarly the interior may also contain a heat conducting fill material as described in collector 300. Sunlight passes through the cylinder and is incident on the core 338 where it is subsequently turned into heat. The resulting radiation 344 drives evaporation of the HTF resident in the wick, which is sustainably replaced by the pumping properties of the wick by incoming fluid 332. This evaporated heat transfer fluid 340, is forced via pressure differences to propagate into the absorbing core 338, where it undergoes superheating via some combination of conductive and radiant heat transfer from the core 338. The resulting vapor 342, is output to be subsequently used in a thermal energy conversion system or other system process which can make use of heat.
 Referring now to FIG. 4, another variation of the planar collector 400 is shown. In many ways this design is also similar to the collector shown in FIG. 1. Transparent front plate 404 is bonded to hermetically sealed housing 410. The interior surfaces of both are coated with a wick medium 408, which is in fluid communication with inlet conduits 420. Absorber core or core 412 has a surface which has been treated or coated in a way to maximize the absorption of visible light and minimize it's emission of infrared radiation.
 In this case the core 412, is not porous but is a solid hollow metal cylinder which is capable, due to its material properties and dimensions, of withstanding high internal pressure. The bulk of the interior of the absorber core is filled with a porous material, the superheat matrix 414, nominally a highly thermally conductive metal, with a pore size and porosity similar to the cores described in FIG. 3.
 One end of the core is in fluidic communication with and hermetically sealed too, outlet conduit 424. Thus superheated HTF vapor 426, may only be output via conduit 424. The absorber core is plugged on one end by high pressure capillary pump 416. Capillary pump 416 is a porous material construct of high mechanical strength. It may be comprised of any one or a combination of materials including metals, metallic oxides, and carbon which have been produced in the form of a foam or perhaps, via a sintering process, into a porous network. There are a variety of other techniques for producing such materials as known by those who are skilled in the art, especially the art of manufacturing porous filtration components. It may comprise materials of different porosities and pore sizes. High pressure capillary pump 416, is shown in greater detail in 428. In this example the pump has two regions of porosity and pore size, regions 430, and 432, though it may have more. Porous region 430 has a pore size on the order of tens to hundreds of microns and a porosity nominally exceeding 40%. Porous region 432 has a pore size of microns or less and a porosity nominally exceeding 50%. Due to its pore size, region 430 performs the function of pumping a fluid at relatively low pressure, perhaps in the range of 0.1 to 5 bar, in addition to providing mechanical support to region 432. This mechanical support is required because of the high pressure differential which must be sustained between the interior of the core and its exterior. Due to its pore size, region 432 is capable of pumping fluids at higher pressures ranging from 10 bar to 50 bar or more.
 The transparent front plate 404, housing 410, wick 408, the core 310 and its components 416 and 414, and the conduits 424 and 420, collectively comprise a high pressure planar collector. Planar refers to the same dimensional constraints as described in FIG. 3.
 Transparent front plate 404, allows incident light 402, to be absorbed by the core 412. As the core heats up due to the incident solar flux, it begins to radiate thus heating the HTF within the wick 408. Proper design of both the wick 408, and the high pressure capillary pump 416, as well as proper maintenance of the internal pressure, among other factors, prevents or inhibits evaporation of the HTF which flows towards capillary pump 416. Capillary pump 416, due to its porosity and pore size is capable of pumping the heated HTF into the superheat matrix 414 against high pressure. Heat which is conducted from the body of the core to the capillary plug causes the fluid to vaporize inside the core and propagate into superheat matrix 414. This drives the pumping of additional fluid, from wick 408, to replace it. Pressure differences within the superheat matrix 414, drive the vapor to propagate towards the other end of the core, and the HTF vapor absorbs heat via radiative and conductive processes as it does so. Because of the mechanical properties of the superheat matrix 414, and the pumping properties of the capillary pump 416, this vapor may be achieve high pressures exceeding 10 bar without damage to the collector. The advantage of being able to sustain high output pressures will be detailed later in this specification.
 Referring again to FIG. 4, a cylindrical solar collector 440 is shown which is identical in function and operation to planar collector 400 of the same Figure. A transparent cylinder 444 has a transparent wick 446, resident on its interior surface. Core 450, is sealed by capillary pump 452 at one end, and the bulk of its interior occupied by superheat matrix 454.
 Similar in operation to the planar collector 400, sunlight passes through the cylinder wall of the transparent cylinder 444 where it is incident on core 450, and subsequently converted into heat. The radiation from the core heats up the HTF 456, which is propagating in wick 446, and is finally pumped via capillary pump 512, into the interior of the absorber core. There it is turned into a vapor, then superheated by passage through superheat matrix 454, and output in the form of high pressure superheated vapor 458. Output temperatures from the collectors described in FIGS. 3 and 4 can theoretically achieve temperatures exceeding 300 C without the need for mechanisms for tracking the sun or optics for concentrating the solar flux. With concentration, which can take the form of parabolic troughs, Fresnel arrays, parabolic dishes, and other techniques well known and demonstrated commercially, output temperatures can reach even higher values.
 Referring now to FIG. 5, two heat transfer loops are illustrated. The first, the heat transfer fluid loop, comprises vapor and fluid loop sections 504 and 506 respectively, which collectively form a continuous hermetically sealed conduit loop through which heat transfer vapor and fluid may flow. The second loop, the working fluid loop, comprises vapor and fluid loop sections 518 and 520 respectively which collectively form a separate hermetically sealed conduit loop. The loops are coupled via heat exchangers 510, 512, and 514. In general, heat exchangers 510, 512, and 514, provide a means for transferring heat from one conduit to another without mixing the two fluids between which the heat is exchanged. The overall goal is to effectively transfer heat from the heat transfer loop, to the working fluid loop.
 During operation, low pressure solar collector array 502 (which could comprise planar and/or cylindrical collectors as described earlier), is illuminated by the sun 500 and the resulting heat in the form of a superheated low pressure vapor is carried away via vapor conduit 504.
 Some portion of this heat may be stored in thermal energy storage unit 508 which is connected to conduit 504. Thermal energy storage unit 506, is a sealed tank capable of supporting high internal pressures and filled with a quantity of water and/or water vapor at saturation. Input and extraction of thermal energy may be accomplished by a number of means including those described by the aforementioned U.S. patent application Ser. No. 12/396,336. The heat from conduit 504 passes through superheater heat exchanger 510 which lowers the temperature of the vapor, and provides a means for transferring heat from the vapor in conduits 504 to the vapor in conduits 516. The vapor continues to flow to boiler heat exchanger 512, which lowers the temperature of the vapor further, transferring additional heat to the fluid passing through the heat exchanger via conduit 518. Finally the vapor passes through preheat heat exchanger 512, where it is condensed into a liquid. This liquid passes into fluid conduit 506 where it is pumped via pump 516, back into the collector array 502 where it can be reheated. This represents a typical solar thermal heat transfer loop though in this case the pump, 516, may not be necessary or its required pumping capacity lowered due to the inherent capillary pumping capacity of the solar collector array.
 The temperature of evaporation in the collector is determined in part by the total volume of HTF and vapor which exists in the HTF loop. This combined volume contributes to the internal operating pressure of the system or the saturation pressure. The volume and therefore operating pressure of the HTF loop, can be determined when the system is assembled and/or changed dynamically during operation to minimize the temperature difference between the environment and the condensed HTF inside the wick. One simple means for achieving this dynamic control would be to incorporate a hermetically sealed reservoir 526, which is coupled to the system via a pump and valve mechanism. The pump could be used to decrease the operating pressure of the system by pumping excess vapor or fluid into the reservoir, and the valve could be used to release the vapor/fluid from the reservoir into the system. The pump and valve mechanisms would operate under electronic or computer control to keep the internal system operating pressure at a level which relates to the environmental conditions including but not limited too ambient temperature, solar flux intensity, and wind conditions. Many means exist for controlling internal pressure which are well known to those skilled in the art of pressurized network design. In general, keeping the temperature difference between the environment and the HTF in the wick further reduces heat losses to the environment and is the goal of the computer control system.
 With respect to the working fluid loop, condensed working fluid is pumped via pump 522 through fluid conduit 520 into heat exchanger 514 and receives sufficient-heat so that its temperature is raised to the boiling point. After the heated working fluid passes through heat exchanger 512, the additional heat boils it and produces a vapor stream which flows into vapor conduit 518. The resulting working fluid vapor stream passes through heat exchanger 518 where it is superheated. After this stage the superheated vapor then passes through utility generation unit (UGU) 524, where it is converted into various utilities comprising some combination of electricity, heat and cooling resources for industrial, residential or other uses. Because the generation of electricity from a heat source generally requires a working fluid vapor under high pressure, two separate loops are required in order to maintain low pressure on the heat transfer loop side, and high pressure on the working fluid loop side. If the suite of utilities supplied by UGU 524, does not include electricity, then only one loop is required and heat exchangers 510, 512, and 514, can be eliminated.
 Referring now to FIG. 6, a single working fluid heat transfer loop is shown comprising vapor loop sections 604, and fluid loop sections 614. During operation solar flux incident on high pressure collector array 602, results in a high pressure superheated vapor stream which flows into vapor conduit 604. In a fashion similar to that described for FIG. 5, heat may be added to or extracted from thermal energy storage unit 606 as conditions of operation merit. The superheated vapor is transported to expander 608 which is in the form of one of many designs for expansion units (turbines, tesla engines, screw expanders, etc.) which are manufactured commercially. The function of the expander is to convert the energy of the expanding vapor into mechanical work which can be used to drive electric generator 610 to generate electricity. The expanded vapor emerging from the expander still has useful heat, thus it flows to UGU 612, which converts and/or transfers this heat into heating/cooling resources as described above. The UGU 612, extracts sufficient heat so that the vapor is condensed and flows into fluid conduit 614. Pump 616 then transports the fluid back to the collector array where it can be reheated and converted back into a superheated vapor. As in FIG. 5, this pump may be optional or require lower pumping capacity based on the ability of the collector array to pump fluids via capillary action.
 The expander/generator 608/610 are shown external to the utility unit (unlike in FIG. 5) to illustrate the point that the production of high pressure superheated vapor allows the expander to be directly driven by the output of the collector array. This cannot be accomplished with the aforementioned low pressure array as a high pressure difference is required to extract any useful work from the output superheated vapor. In this regard, a thermal energy conversion system based on high pressure collectors is simpler and less costly to construct and maintain.
 It should be noted that while an expander has been described as a means for converting heat into mechanical energy, to be subsequently converted electricity, it is not the only option. Other means for the conversion of heat into electricity include but are not limited to, thermoelectric devices, fuel cell like thermal conversion devices, and thermo electron emission devices. Many versions of these approaches exist and are in various stages of development by those skilled in the art of such components and processes. All of these approaches may be incorporated into the solar thermal conversion systems described above with varying conversion efficiencies based on the output temperature of the solar array, the condensing temperature of the environment, and the particular characteristics of the thermo-conversion technology.
 Referring now to FIG. 7, an integrated application illustrating how the utilities generated by a solar thermal conversion system can be exploited is shown. Symbolic block 700, represents a solar thermally driven UGU comprising many of the components already described in this specification including, a solar collector array 704 (driven by the sun 702), thermal storage unit 706, and UGU 710. These combined represent the solar thermal conversion system already described. While the connecting heat transfer loops are not shown, they are implicit in this diagram and thus the aforementioned components are thermally coupled in a manner described earlier so that heat input from the solar flux source is converted and output in the form of electricity and cooling resource (via a chilled fluid loop) from UGU 710. One additional component is the hydrocarbon fuel supplemental heat source 708. This component generates heat by the combustion of a hydrocarbon fuels such as natural gas, biofuels or fuel oil. This heat source provides additional or alternative heat to the solar thermal conversion system should the thermal storage unit 706, prove inadequate and the solar flux source or solar collector array be compromised due to inclement weather or some other reason. Hydrocarbon fuel supplemental heat source 708, is also coupled thermally to the system so that its heat can be supplied in the same way the heat from the collector array and the storage unit is incorporated.
 Symbolic block 712 is a facility which exploits the electricity and cooling utility output by the UGU 710. In this example the facility is in the form of a data center comprising, an array of computational units and/or data storage units and associated data communications hardware represented by hardware array 714. Data centers are facilities operated to handle large data processing tasks driven by the information technology needs of users 718, which include a variety of businesses and commercial entities ranging from banking to internet hosting and web searching. The primary inputs of data centers are in the form of electricity and a cooling resource, the latter being used to dissipate the tremendous heat which is generated during the course of operating the components comprising hardware array 714. Their primary output is in the form of electronic data exchanged via one or more of several data exchange means 716, including fiber optic data links, microwave data links, and more conventional signal carrying conductive cable arrays, among others. Data centers are historically located near sources if inexpensive energy (hydroelectric dams for example) and access points to high bandwidth communication nodes (fiber optic hubs). In general proximity to the energy source takes priority as the cost to construct-high tension lines capable of transmitting the large amounts of power required are more expensive than installing the fiber optic cables, or other data exchange mechanism, required to transmit large amounts of data.
 Given that the highest levels of solar flux are generally available in remote desert locations, the optimal performance of solar thermal conversion systems is achieved by locating such generation facilities far away from where their power could be utilized. This locational requirement increases the cost of such facilities since the construction and permitting process for the related high tension transmission capacity adds cost, complexity, and delays. Locating an integrated facility, combining the utility generation capacity of block 700 with the utility consuming and data processing capability of block 712, at the remote location where the solar flux is high can reduce costs. The overall cost reduction comes about due to eliminating the need to establish high tension transmission capacity, which is very high, at the price of adding the requisite data exchange means, which is very low. The lower cost of the data exchange means comes about as a result of the lower physical footprint and associated infrastructure require to install some combination of fiber optic, microwave, or other means for data exchange.
 Referring now to FIG. 8, a solar thermal system dedicated to producing a heating and/or cooling resource is shown. Solar collector array 802 is illuminated from the sun 800, to produce a high temperature working fluid vapor stream into vapor conduit 804. Thermal storage unit 806, as described in the earlier Figures, can be used to store excess heat and release it as needed. The working fluid vapor passes through utility generation unit (UGU) 808 where, after imparting some portion of its heat, it is condensed and is pumped by optional fluid pump 810, back to the solar collector array. UGU 808 is comprised of one of a variety of thermally driven chiller units which are well understood by those skilled in the art of manufacturing such components which are both commercially available and under development. Such chiller include bur are not limited to absorption chillers, adsorption chillers, and jet vacuum chilling processes. Another approach involves using an expander, of the type described earlier, to mechanically drive a compressor unit as the basis for a conventional vapor compression refrigeration cycle. A solar thermal conversion system of this sort can benefit from the small physical footprint of the planar solar collectors described above, facilitating roof mounted installations and providing high quality heat without the need for tracking or concentrating optics.
Patent applications by Mark W. Miles, Atlanta, GA US
Patent applications in class Having evaporator and condenser sections (e.g., heat pipe)
Patent applications in all subclasses Having evaporator and condenser sections (e.g., heat pipe)