Method and Apparatus for Collecting Solar Energy

Abstract

Various embodiments for an improved solar collector are disclosed. For example, a heat absorber can be positioned inside an evacuated chamber formed by a frame and a transparent cover. Heat absorbed by the heat absorber within the evacuated chamber can be delivered to a heat transfer fluid inside a chamber of a heat exchanger. The heat exchanger chamber can also reside in the evacuated chamber. In a preferred embodiment, the heat absorber comprises a planar heat pipe. Also in a preferred embodiment, a reflector can be positioned to reflect energy radiated by the heat absorber back to the heat absorber.

Description

BACKGROUND AND SUMMARY OF THE DISCLOSURE

The present invention is directed toward an improved solar collector design. Extensive work has been done in the field of solar collectors. Examples of solar collectors that are known in the art include flat plate solar collectors and evacuated tube solar collectors.

An issue faced by designers of solar collectors is how undesired heat loss to the outside environment can be reduced. That is, heat captured by the solar collector can be lost to the outside environment through processes known as convection, conduction and radiation. Such heat loss reduces the efficiency and output of a solar collector. Another issue faced by designers of solar collectors is how a solar collector can be designed to increase the percentage of its exposed surface area that is used to absorb heat.

The inventors disclose a number of solar collector embodiments that the inventors believe address and improve on one or more of these issues.

In accordance with a first aspect of an exemplary embodiment of the invention, disclosed herein is an apparatus for collecting solar energy, the apparatus comprising (1) a planar heat pipe configured to absorb heat, (2) a frame surrounding the planar heat pipe, the frame forming a chamber within which at least a portion of the heat pipe resides, and (3) a transparent cover engaged with the frame to enclose the chamber, and wherein the chamber comprises an evacuated chamber.

Also disclosed herein is a method for collecting solar energy, the method comprising absorbing heat with a solar collector, the solar collector comprising a planar heat pipe positioned inside an evacuated chamber formed by a frame and a transparent cover.

Further disclosed herein is an apparatus for collecting solar energy, the apparatus comprising (1) a planar heat pipe configured to absorb heat, the heat pipe having a plurality of holes, (2) a frame, the frame comprising a bottom member and a plurality of sidewalls forming a chamber within which the heat pipe resides, (3) a transparent cover engaged with the frame to enclose and seal the chamber, wherein the chamber comprises an evacuated chamber, (4) a heat exchanger in cooperation with the heat pipe, the heat exchanger comprising a heat exchanger chamber and an output, the heat exchanger being configured to receive and transfer the heat absorbed by the heat pipe to the output, wherein the heat exchanger chamber is positioned inside the evacuated chamber, and (5) a plurality of free-floating pins positioned to support the heat pipe without the heat pipe contacting the frame, the pins having a bottom portion for engaging the bottom member and a top portion for engaging the transparent cover, and wherein the pins pass through the heat pipe holes.

In accordance with another aspect of an exemplary embodiment of the invention, disclosed herein is an apparatus for collecting solar energy, the apparatus comprising: (1) a heat absorber configured to absorb heat, (2) a frame adapted to form a chamber within which at least a portion of the heat absorber resides, (3) a transparent cover engaged with the frame to enclose the chamber, the cover configured to permit solar energy to enter the chamber and impact the heat absorber, and (4) a reflector positioned and configured to reflect energy radiated by the heat absorber back to the heat absorber.

Further disclosed is a method comprising, within a solar collector having a heat absorber positioned inside a chamber, reflecting energy radiated by the heat absorber back to the heat absorber with a reflector.

Also disclosed is a method comprising, within a solar collector having a heat absorber positioned inside a chamber, the chamber being formed by a bottom member, a plurality of side walls and a transparent cover, positioning an energy reflector between the heat absorber and the bottom member.

Further still, disclosed herein is an apparatus comprising a flat plate solar collector having an evacuated chamber within which a heat absorber and a reflector are positioned, the reflector being positioned beneath the heat absorber for reflecting energy radiated by the heat absorber back to the heat absorber.

In accordance with another aspect of an exemplary embodiment of the invention, disclosed herein is an apparatus for collecting solar energy, the apparatus comprising (1) a heat absorber configured to absorb heat, (2) a frame surrounding the heat absorber, the frame forming a chamber within which the heat absorber resides, (3) a transparent cover engaged with the frame to enclose and seal the chamber, wherein the chamber comprises an evacuated chamber, and (4) a heat exchanger in cooperation with the heat absorber, the heat exchanger comprising a heat exchanger chamber and an output, the heat exchanger being configured to receive and transfer the heat absorbed by the heat absorber to the output, wherein the heat exchanger chamber is positioned inside the evacuated chamber.

Furthermore, disclosed herein is a method for collecting solar energy, the method comprising (1) absorbing heat with a heat absorber, wherein the heat absorber is positioned inside an evacuated chamber formed by a frame and a transparent cover of a solar collector, and (2) transferring the absorbed heat to a heat exchanger, the heat exchanger comprising a heat exchanger chamber, wherein the heat exchanger chamber is also positioned inside the evacuated chamber.

In accordance with yet another aspect of an exemplary embodiment of the invention, disclosed herein is an apparatus for collecting solar energy, the apparatus comprising (1) a heat absorber configured to absorb heat, the heat absorber comprising a plurality of holes, (2) a frame, the frame comprising a bottom member and a plurality of sidewalls that form a chamber within which the heat absorber resides, (3) a transparent cover engaged with the frame to enclose and seal the chamber, wherein the chamber comprises an evacuated chamber, and (4) a plurality of free-floating pins positioned to support the heat absorber without the heat absorber contacting the frame, the pins having a bottom portion for engaging the bottom member and a top portion for engaging the transparent cover, and wherein the pins pass through the heat absorber holes.

Also disclosed is a method for collecting solar energy, the method comprising (1) absorbing heat with a heat absorber wherein the heat absorber is positioned inside an evacuated chamber formed by a frame and a transparent cover of a solar collector, the heat absorber comprising a plurality of holes, and (2) supporting the heat absorber within the frame with a plurality of free-floating pins that pass through the heat absorber holes, the pins positioned to support the heat absorber without the heat absorber contacting the frame, the pins having a bottom portion for engaging a bottom member of the frame and a top portion for engaging the transparent cover.

In accordance with still another aspect of an exemplary embodiment of the invention, disclosed herein is an apparatus for collecting solar energy, the apparatus comprising: (1) a vacuum pump line for connection to a vacuum pump, (2) a plurality of branch vacuum pump lines for connection to the vacuum pump line, (3) a plurality of solar collectors connected to at least one of the branch vacuum pump lines to form an array of solar collectors, each solar collector comprising an evacuated chamber, a heat absorber positioned at least partially inside the chamber, and a tube valve for connection to the at least one branch vacuum pump line, and (4) a solenoid valve connecting the vacuum pump line with the at least one branch vacuum pump line, the solenoid valve being configured to open and close to maintain a vacuum pressure inside the chambers of the solar collectors in the array and isolate the solar collectors in the array from the vacuum pump line in response to a control signal.

Further disclosed is a method for collecting solar energy, the method comprising: (1) collecting energy with a plurality of solar collectors, each solar collector comprising an evacuated chamber and a heat absorber positioned inside the evacuated chamber, and (2) using at least one solenoid valve to maintain a vacuum pressure inside the evacuated chambers and isolated the evacuated chambers from an upstream vacuum pressure fault.

In accordance with still another aspect of an exemplary embodiment of the invention, disclosed herein is an apparatus for collecting solar energy, the apparatus comprising (1) a plurality of branch pipe lines, (2) a trunk pipe line configured to deliver heat transfer fluid to the plurality of branch pipe lines, and (3) a plurality of solar collectors serially connected to at least one of the branch pipe lines to form an array of solar collectors.

Moreover, disclosed herein is a method comprising (1) delivering heat transfer fluid from a trunk pipe line to a plurality of branch pipe lines, wherein at least one of the branch pipe lines comprises a plurality of solar collectors serially connected to form an array of solar collectors, and (2) collecting energy with the array of solar collectors to heat the delivered heat transfer fluid.

These and other features and advantages of various embodiments of the present invention will be apparent to those having ordinary skill in the art upon review of the specification and drawings contained herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1(a)-(c) depict an exemplary solar collector in accordance with an embodiment of the invention;

FIG. 2(a) depicts an exemplary solar collector in accordance with another embodiment of the invention;

FIG. 2(b) depicts an exemplary reflector that can be used in the solar collector embodiment of FIG. 2(a);

FIG. 2(c) depicts an exemplary solar collector in accordance with yet another embodiment of the invention;

FIGS. 2(d) and (e) depict exemplary transparent covers for use with exemplary solar collector embodiments;

FIGS. 3(a)-(f) depict an exemplary solar collector in accordance with yet another embodiment of the invention;

FIG. 4 is an exploded cross-sectional view of the solar collector portion around the manifold heat exchanger from FIG. 3(a);

FIG. 5 depicts various views of an exemplary planar heat pipe that can be used with the solar collectors disclosed herein;

FIGS. 6(a)-(d) depict various heat pipe embodiments showing how a plurality of cylindrical heat pipes can be arranged to approximate a planar heat pipe;

FIG. 7 depicts a cross-sectional view of an exemplary planar heat pipe having an upper surface with a plurality of ridges and troughs;

FIGS. 8(a)-(e) depict various views of exemplary planar heat pipes with patterned surfaces;

FIGS. 9(a) and (b) depict exemplary embodiments for a manifold heat exchanger;

FIGS. 10(a)-(c) depict additional exemplary embodiments for a manifold heat exchanger having different inlet/outlet port arrangements;

FIG. 11(a) is a cross-sectional view of an exemplary manifold heat exchanger that illustrates how a heat transfer fluid is heated;

FIGS. 11(b)-(d) depict examples of how heat transfer fluid can flow through a dual-chamber bidirectional manifold heat exchanger embodiment;

FIGS. 12(a)-(d) depict exemplary support pins that can be used in various solar collector embodiments;

FIGS. 13(a)-(c) depict exemplary arrays that can be created from a plurality of the solar collectors disclosed herein;

FIG. 13(d) depicts an exemplary technique for ganging solar collectors together in an array;

FIG. 14 depicts an exemplary arrangement of solar collector arrays on a support member providing tilting elevation for the solar collectors;

FIGS. 15(a) and (b) depict exemplary vacuum systems that can be employed by exemplary solar collector arrays

FIG. 16 depicts a top view of an exemplary solar collector in accordance with another embodiment;

FIGS. 17(a) and (b) depict an exemplary embodiment of a solar collector that is encased in insulation; and

FIGS. 18(a) and (b) depict exemplary solar collectors having a plurality of heat pipes sharing a single evacuated chamber.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1(a) depicts a cross-sectional view of an exemplary solar collector 100 in accordance with an embodiment of the invention. FIG. 1(b) depicts a top view of this solar collector 100, and FIG. 1(c) depicts a perspective view of this solar collector 100. Solar collector 100 comprises a heat absorber 102, preferably a planar heat pipe as discussed below, positioned inside a chamber 108 formed by a box frame 104 and a transparent cover 106. However, it should be understood that the heat absorber 102 need not be a heat pipe as other types of heat absorbers could be used. For example, the heat absorber 102 can be a manifold heat absorber where a heat transfer fluid flowing through piping absorbs heat and this heated heat transfer fluid is then passed out of the solar collector through a heat exchanger port 114. However, the inventors believe that the use of a heat pipe as the heat absorber 102 can provide some advantages relative to such a manifold design because the heat pipe permits the solar collector system to exhibit a higher flow rate for the heat transfer fluid at lower pressure in the piping.

Box frame 104 comprises a bottom member 120 and a plurality of sidewalls 122 formed to create a box having an open chamber 108. A transparent cover 106 that is adapted to pass energy such as light from the outside environment into chamber 108 is positioned atop the box frame 104 to enclose chamber 108.

Box frame can be formed from a material that is sufficiently strong to support the weight of the transparent cover, and with embodiments where the interior chamber of the box frame is evacuated the material should also be capable of adequately maintaining a vacuum. Examples of box frame materials include aluminum, copper and plastic. Also, box frame preferably has a rectangular shape with a long dimension and a short dimension as shown in FIGS. 1(a)-(c), particularly in the top view of FIG. 1(b). However, this need not be the case. For example, a square box frame could be used. Further still, shapes of other polygons such as hexagons could also be used if desired by a practitioner. However, a rectangular shape is preferred because it is expected that a rectangular shape will be more amenable to field assembly and mass production. It should also be understood that the dimensions of the box frame 104 can be varied based on the desires of a practitioner in view of the structural strength needs. An exemplary length (the long dimension shown in FIG. 1(b)) and width (the short dimension shown in FIG. 1(b)) for the box frame can be 4 feet by 8 feet but other dimensions could readily be accommodated. An exemplary height (the vertical dimension shown in FIG. 1(a)) for the box frame can be around 3-6 inches. However, once again, other heights can be used. Furthermore, while the exemplary box frame 104 is described as comprising a bottom member 120 and a plurality of sidewalls 122, it should be understood that the box frames 104 can be formed from not only discrete bottom member units and sidewall units but the box frame 104 can also be formed from an integral structure having a bottom member and a plurality of sidewalls.

The transparent cover 106 is preferably a pane of glass or other material that transmits electromagnetic energy for impacting the heat absorber 102. For example, as is understood in the window arts, the transparent cover 106 can be formed from a material that efficiently passes a desired spectrum range of energy radiated by the sun. This pane is preferably sized to effectively match the length and width dimensions of the box frame 104 and enclose the chamber 108. The thickness of the transparent cover 106 can be varied as desired by a practitioner so long as the transparent cover is sufficiently strong to withstand external forces and pressures imposed by select weather events and the like when the solar collector 100 is in use (e.g., storms, hail, strong winds, etc. depending on the expected weather patterns in the geographic locations where the solar collector would be deployed). The thickness for the transparent cover 106 can vary as desired by a practitioner based on a number of factors. The transparent cover thickness must balance competing factors such as being able to pass a sufficient amount of energy (it is expected that increasing thickness would reduce the percentage of energy impacting the outer surface of the cover 106 that is passed to the chamber 108) while also being sufficiently strong to maintain its integrity when the chamber 108 is under vacuum pressure (it is expected that increasing thickness would increase the cover's strength). Another variable that could impact the cover's thickness is how many support pins 112 are used. Generally speaking, the use of more support pins 112 rather than fewer would better support the cover 106 and permit a less thick cover 106. However, each support pin 112 also takes away from the surface area of the heat absorber that is used to absorb energy, in which case a practitioner will need to balance these factors when selecting a number of support pins 112 and cover thickness. Exemplary thicknesses for the transparent cover 106 can be ¼, ½ or ⅜ of an inch.

Any of a number of techniques can be used to securely engage the transparent cover 106 with the top of box frame 104 to enclose the chamber 108. For example, a sealant material can be applied around the perimeter of the top of the box frame 104, and the transparent cover 106 can be securely attached to the box frame 104 via this sealant. Over time, the box frame 104 and cover 106 will adhere to the sealant to form a secure gasket-type engagement between the frame 104 and cover 106. To accelerate this process, the cover 106 can be seal set during fabrication by applying the sealant and cover 106 to the box frame 104 and evacuating the chamber 108. The pressure created by the vacuum will force the cover 106 against the sealant and accelerate this adhering process. Exemplary sealants that can be used include silicon, Teflon or other heat-resistant materials with sufficient give and adhering properties. The sealant can be applied around the rim of the box frame 104 as a tape. Also, a practitioner may choose to apply one or more spring clips 300 to the transparent cover 106 and box frame sidewalls 122 to further secure the transparent cover 106 to the box frame 104 (see, for example, FIGS. 3(a) and 4 discussed below). Such spring clips 300 can further secure the cover 106 in place, especially while the solar collector 100 is being transported to the location where it is to be used. If desired, for embodiments where the solar collector's chamber 108 is an evacuated chamber, the inventors believe that the spring clips 300 could be removed after the solar collector is put in place in the field because it is believed that the vacuum pressure in the chamber will be sufficient for keeping the cover 106 engaged against the frame 104.

Furthermore, it should be understood that the sealant need not possess adhesive properties described above; in embodiments wherein the chamber 108 is evacuated, the sealant need only serve to create a seal to help maintain the vacuum pressure of the chamber 108. For example, the vacuum pressure and/or spring clips 300 could be used to secure the cover 106 to the frame 104 in the absence of an adhesion of the seal to the cover 106 and frame 104.

A heat absorber 102 is positioned inside the chamber 108. As explained below, the heat absorber 102 is preferably a planar heat pipe. As energy such as sunlight enters the chamber 108 through transparent cover 106 and impacts the upper surface 116 of the heat absorber 102, the heat absorber absorbs this energy and transfers heat created by the absorbed energy to a portion of the heat absorber in communication with a manifold heat exchanger 110. The manifold heat exchanger 110 has a plurality of ports 114, and receives a heat transfer fluid into a chamber via an intake port 114a. This heat transfer fluid, which serves as a carrier fluid, is heated by a portion of the heat absorber 102 that resides within or contacts the heat exchanger chamber. Heated heat transfer fluid then exits the manifold heat exchanger 110 via an outtake port 114b. This heated heat transfer fluid can then be delivered to downstream appliances as needed to provide desired energy. For example, the heated heat transfer fluid can be delivered to a chiller unit or the like to help power an air conditioning operation. Any of a variety of known heat transfer fluids can be used by the heat exchanger 110, and the selection of an appropriate heat transfer fluid can made by a person of ordinary skill in the art based on factors such as the expected operating temperatures of the system. For example, water (or a mix of water and antifreeze) can be used in a system where the expected temperature range does not exceed around 212 degrees Fahrenheit. At higher temperatures, other heat transfer fluids known in the art could be employed.

Also, while the examples of FIGS. 1(a)-(c) show the heat exchanger 110 having male ports 114, it should be understood that the heat exchanger 110 could also be configured with female ports 114. Such female ports 114 would then engage with piping to receive heat transfer fluid and output heated heat transfer fluid. Any of variety of known techniques could be used for engaging piping with the ports 114, whether male or female. For example, the ports 114 could have threading that permits piping to be screwed on, O-ring-type connections could be made between the ports 114 and piping, or any of a variety of other techniques.

Preferably, chamber 108 is evacuated after the transparent cover 106 is put in place atop the box frame 104. Furthermore, it is preferred that this evacuation occur in the field after the solar collector has been positioned on site where it is to be used. By maintaining a vacuum inside chamber 108, the solar collector will be better insulated from convection heat loss to the ambient environment. That is, the vacuum inside chamber 108 will help reduce the rate at which heat captured by the heat absorber escapes to the environment by convection.

To evacuate the chamber a tube valve 124 can be installed at some location along the box frame. This valve 124 permits the solar collector's chamber 108 to be connected to a pump line for creating a continuous vacuum pressure inside the chamber. This tube valve 124 can be a conventional access valve with a tube extension as is known in the heating and cooling arts. The pump line to which this valve 124 is connectable would be connected to a vacuum pump and the vacuum pump would maintain the vacuum pressure inside the chamber. As explained below, in embodiments where the solar collector 100 is deployed in an array of solar collectors, a pump line can serve multiple solar collectors if desired.

To further improve the insulation properties of the solar collector 100, the chamber portion of the manifold heat exchanger 110 is also preferably positioned inside the evacuated chamber 108, as shown in FIGS. 1(a)-(c) (see also chamber 900 in FIG. 4). With such an embodiment, the heat loss due to convection from the heat exchanger 110 can be reduced. Furthermore, the amount of piping external to the insulation provided by the vacuum through which the heated heat transfer fluid flows is reduced.

Moreover, the heat absorber 102 is preferably positioned inside the chamber 108 such that the heat absorber chamber does not directly contact the box frame's bottom member 120 or sidewalls 122. As shown in FIG. 4, a standoff sleeve 412 that serves as a conductive barrier to heat can be used as at least part of the heat exchanger's ports 114 to support that heat exchanger's reservoir chamber away from the frame 104. By avoiding such contact, the solar collector reduces heat loss from the heat absorber to the outside environment via conduction. Preferably, there is a gap of around ¼ to 1 inch between the heat absorber 102 and the sidewalls 122 and a similar gap between the heat absorber 102 can the bottom member 120, as shown in FIG. 1(b). However, it should be understood that other gap dimensions could be used with a caveat that it is generally preferred to not use too large of a gap between the heat absorber 102 and the sidewalls 122 so as to maximize the exposed surface area of the heat absorber 102 that captures sunlight.

To support the heat absorber 102 in a manner that avoids direct contact with the box frame's bottom member 120 and sidewalls 122, a plurality of support pins 112 are used. Preferably, these support pins 112 are “free-floating” within the chamber 108 of the box frame 104. What is meant by “free-floating” is that the support pins 112 are not attached to the box frame 104. Essentially, if one were to remove the transparent cover 106 and heat absorber 102 and turn the box frame 104 upside down, the pins would fall out. The inventors believe that by using free-floating pins rather than pins that are fixedly attached to the frame 104 (or cover 106), the solar collector will better be able to accommodate the thermal expansions and contractions that can be expected to occur as a result of heating and cooling, particularly when one considers that different materials used in the solar collector will likely have different thermal expansion/contraction properties. The inventors also believe that the use of free-floating support pins may reduce thermal losses due to convection. Furthermore, for exemplary embodiments, the support pins 112 also provide support to the transparent cover 106, particularly when under pressure from a vacuum in chamber 108. The heat absorber 102 is preferably configured with a plurality of holes through which the pins 112 are passed as shown in FIGS. 1(a) and (b) to support the heat absorber 102 and transparent cover 106. While the holes shown in FIGS. 1(a)-(c) are generally circular in shape, it should be understood that the holes may be formed by gaps of any shape if desired by a practitioner. A practitioner can also select a desired spacing of holes and pins along the heat absorber 102 so as to adequately support the cover 106. As noted above, factors such as the thickness of the cover 106 and the expected weather conditions where the solar collector is to be deployed all factor into how many pins 112 are needed and how they should be spaced.

An exemplary embodiment of a free-floating support pin 112 is shown in greater detail in FIGS. 12(a) and (b). In this embodiment, the support pin 112 is generally cylindrical, and it has a bottom portion 1200 of a first diameter and an upper portion 1202 of a second diameter, wherein the first diameter is larger than the second diameter. This creates a shoulder portion 1204 upon which the heat absorber 102 rests, as shown in FIG. 1(a). An upper face 1206 of the upper portion 1202 engages and provides support to the transparent cover 106. A bottom face 1208 of the bottom portion 1200 engages the bottom member 120 of the box frame 104. As a free-floating support pin, neither upper face 1206 nor bottom face 1208 is attached to the transparent cover 106 or bottom member 120.

It should be noted that while the exemplary embodiment of FIGS. 12(a) and (b) is shown to have a generally cylindrical shape, other shapes could be used for the support pins 112, such as square shapes, rectangular shapes, or other polygonal shapes.

To reduce conduction losses to the outside environment via a path from the heat absorber 102 through the pins 112 to the box frame 104, the pins are preferably made out of material that is a poor conductor of heat, such as a ceramic. However, it should be understood that other materials could be used if desired by a practitioner. For example, ceramic end caps could be placed over metal support pins.

Furthermore, as shown in FIG. 12(c), a cushion layer 1220 could be attached to the upper face 1206 of the support pins to provide cushioning between the pins 112 and cover 106 for accommodating thermal expansion/contraction and/or the vacuum pressure. This cushion layer can be formed of a silicon material or the like. A similar cushion layer 1222 could be applied to the bottom face 1208 of the support pins (see FIG. 12(d)). Moreover, both the upper and bottom faces 1206 and 1208 can employ such cushion layers 1220 and 1222 if desired.

FIG. 2(a) is a cross-sectional view of another exemplary solar collector embodiment. The solar collector 100 of FIG. 2(a) is similar to the solar collector shown in FIGS. 1(a)-(c), except the solar collector 100 of FIG. 2(a) includes a reflector 200 positioned between the bottom surface 118 of the heat absorber 102 and the bottom member 120 of the box frame 104. The reflector 200 is thus positioned to reflect energy radiated by the heat absorber 102 back to the heat absorber 102. In this way, radiation losses from the solar collector to the outside environment can be reduced. The reflector 200 is preferably of a planar shape and sized to cover the bottom surface area of the chamber 108.

FIG. 2(b) is a side view of an exemplary reflector 200. The reflector 200 is basically a mirror or other polished surface having a substrate 202, wherein a reflective coating layer 204 sits atop the substrate 202. The substrate 202 is preferably a flat planar pane of glass. However, as noted above, any suitably polished surface could be used. The coating 204 is preferably a coating that is configured to reflect energy of a select wavelength corresponding to the energy that is expected to be radiated by the heat absorber 102. For example, the coating 204 can be a coating that reflects infrared (IR) energy. However, it should be understood that other coatings that are energy-reflective could be used. The selection of a particular coating can be made based on the desires of a practitioner using knowledge about reflective coatings prevalent in the window and glass industry.

It is worth noting that, with a preferred embodiment, the reflector 200 need not be configured to reflect visible light as the reflector 200 is not likely to receive much if any direct visible light because the heat absorber is positioned to block substantially all sunlight from reaching the reflector 200. In fact, with some embodiments, the reflector 200 may not reflect visible light at all and would appear black or non-reflective to an observer unlike the conventional mirrors that have been used with conventional solar collectors. Thus, contrary to past solar collector designs which have used mirrors to concentrate visible light onto a desired location, the solar collector embodiment of FIG. 2(a) uses a reflector 200 to reflect energy radiated by the heat absorber 102 back to the heat absorber 102.

Furthermore, if desired, a practitioner can also place a reflector 200 around the internal face of the sidewalls 122 within chamber 108 to minimize heat loss through the sidewalls. Alternatively, the internal face of the sidewalls 122 can themselves serve as the reflector by highly polishing the sidewall's internal faces to provide better energy reflective properties. Similarly, the bottom member 120 could serve as the reflector itself through such polishing. Further still, the sidewalls and/or bottom member (whether polished or not) can be covered with energy reflective coating 204 to serve as the reflector. Further still, such a coating 204 can be applied directly to the bottom member 120 to serve as the reflector.

Moreover, if desired, a practitioner could also place an energy reflective coating 222 on the underside of the transparent cover 106, as shown in FIG. 2(d). This energy reflective coating 222 would be positioned to reflect energy radiated upward from the heat absorber 102 back to the heat absorber. Furthermore, because the cover 106 needs to transmit electromagnetic energy such as sunlight from above into the chamber 108, this energy reflective coating 222 is preferably a one-way energy reflective coating 222, as known in the window and glass industry, that permits energy to pass in one direction but reflects energy in the other direction. Moreover, to further improve the performance of cover 106, an anti-reflective treatment 224 may be placed on the upper surface of the cover 106 if desired by a practitioner to improve the way the cover 106 captures energy for transmission through to chamber 108 (see FIG. 2(e)). Such a treatment 224, which may take the form of a coating, secondary cover (e.g., a Fresnel lens) or the like would better capture low angle sunlight that strikes the cover 106 and provide the low angle sunlight energy to the chamber 108.

FIGS. 3(a)-(f) are views of another exemplary solar collector embodiment. FIG. 3(a) is a cross-sectional view of an exemplary solar collector 100 along the long dimension of the solar collector. FIG. 3(c) is a cross-sectional view of the solar collector 100 of FIG. 3(a) along the short dimension of the solar collector. With this embodiment, a plurality of spring clips 300 are used for securing the transparent cover 106 to the box frame. The inventors believe that these clips would help secure the cover 106 to the frame 104, particularly during transportation of a solar collector. If desired, the clips 300 can be run more or less continuously along the length and width of the solar collector. However, a spacing of spring clips 300 with longer intervals could be used. Also, the front and side sidewalls 122 include a ledge 302 that enhanced the structural strength of these sidewalls 122. Preferably, the heat absorber 102 does not contact the ledges 302, as shown in FIGS. 3(a) and (c).

FIG. 4 illustrates an exploded view of the rear section of FIG. 3(a). In this figure, the spring clip 300 used to secure the transparent cover 106 to the box frame 104 can be seen in greater detail. Furthermore, FIG. 4 shows that the sidewalls 122 can include a portion 404 that forms an internal ledge around the inner perimeter of the sidewalls near the transparent cover 106. This internal ledge portion 404 can provide support for the transparent cover 106. The sidewalls 122 can also include a portion 406 extending vertically above the ledge to laterally protect the transparent cover 106 and restrict undesired lateral movement of the transparent cover 106. Further still, this portion 406 may extend laterally outward relative to lower portions of the sidewalls 122 to form a surface 408 upon which a portion of the spring clip 300 can grip to secure the spring clip 300 in place. However, it should also be understood that this upper portion can be recessed relative to the lower part of the sidewall 122 (together with a notch in the sidewall upper portion for receiving the spring clip 300) so that multiple solar collectors can be more flushly engaged against each other in an array if desired by a practitioner. Furthermore, the transparent cover 106 may include a sealant layer 402 extending around its perimeter to form a seal with the frame 104 as explained above. The sealant layer 402 may cover around ½ to ¾ of an inch of the cover's edge portions. Also, this sealant layer may be formed from silicon or other suitable materials. Spring clip 300 can also engage the exposed surface of the sealant layer 402 to secure the transparent cover 106 in place.

In the example of FIG. 4, it can also be seen that the bottom of the box frame 104 has been configured with an open path area 430 enclosed by the lateral and rear sidewalls 122, an upper portion 410 and an internal wall 414 (see also FIG. 3(f)). Upper portion 410 can be a plate extending inward into the solar collector interior and perpendicularly from the rear sidewall 122, as shown in FIG. 4. The upper portion 410 may include holes through which the heat exchanger ports 114 pass and a hole through which a valve stem 124 for creating a vacuum within the chamber 108 passes. Piping (not shown) for delivering heat transfer fluid to and taking heat transfer fluid away from the heat exchanger 110 can pass through the open path area 430. The piping can pass into the open path area 430 through a hole 310 in the lateral sidewalls 122, as shown in the side view along the long dimension of the solar collector in FIG. 3(b). The heat exchanger ports 114 may include a standoff sleeve 412 as shown in FIG. 4 to engage against the upper portion 410 of the path area 412. This standoff sleeve 412 both supports the heat exchanger's reservoir chamber 900 away from the frame 104 to reduce potential conduction losses and serves as a conductive barrier to heat with respect to a potential heat flow from the heat exchanger reservoir chamber 900 to the frame 104 and for any piping that connects with the heat exchanger 110. For example, the sleeve 412 through which any piping that connects to the heat exchanger's ports 114 passes, and would thus serve as a barrier to heat conduction between the piping and frame 104. To provide this barrier to heat conduction, the sleeve 412 is preferably formed of a material that is a poor conductor of heat such as a ceramic material. The standoff sleeve 412 may fit through a hole in the upper portion plate 410 and include a flange rim 420 as shown in FIG. 4 for securing the sleeve 412 to the upper portion plate 410. Bolts through the flange rim 420 and plate 410 can secure the standoff sleeve 412 in place.

Also, the internal wall 414 is preferably positioned laterally inward relative to the outer internal edge of the upper portion 410, as shown in FIG. 4. This creates a ledge 416 extending laterally inward into the solar collector interior from the internal wall 414. The reflector 200 engages the bottom surface of this ledge 416. A sealant layer 450 can be used to providing sealing action between the reflector 200 and ledge 416. Further still, another sealant layer 452 can provide sealing action between the reflector 200 and frame bottom member 120, as shown in FIG. 4. These sealant layers 450 and 452 can also be formed of a silicon material or the like. A support material 460 (e.g., backerboard of the like) can be positioned below the bottom member 120 if desired to further support the collector 100.

FIG. 3(d) shows a side view of the solar collector 100 of FIGS. 3(a)-(c) along a short dimension of the solar collector. FIG. 3(e) is a top view of the solar collector 100 of FIGS. 3(a)-(d). As can be seen, the heat absorber 102 takes up the vast majority of the solar collector's exposed surface area. FIG. 3(f) is a bottom view of the solar collector 100 of FIGS. 3(a)-(e). For example, the inventors believe that around 95%-98% of the solar collector's surface area can taken up by the heat absorber 102 to collect energy.

FIG. 5 shows a preferred embodiment for the heat absorber 102. As noted above, in a preferred embodiment, the heat absorber is a planar heat pipe 500. The central frame of FIG. 5 shows a top view of an exemplary planar heat pipe 500. The planar heat pipe 500 can be largely symmetrical with respect to its top and bottom, so this central frame can also depict a bottom view of the planar heat pipe 500. However, this need not be the case. Furthermore, as noted below, different treatments can be applied to the upper and bottom surfaces 116 and 118 to enhance its performance. The upper frame of FIG. 5 shows a cross-sectional view of the planar heat pipe 500 along its long dimension. The left frame of FIG. 5 shows a cross-sectional view of the planar heat pipe 500 along its short dimension. As is known in the art, a “heat pipe” is a closed structure, typically with an internal vacuum, that efficiently transfers heat from a first location to a second location. A planar heat pipe refers to a heat pipe that has a generally planar shape in that it is generally flat and exhibits a length and width that are much larger than its thickness. An exemplary thickness for the planar heat pipe 500 can be around ½ to 1 inch. An exemplary length and width for the planar heat pipe 500 can be similar to the length and width for the frame's chamber 108 such that the heat pipe 500 fits inside the frame's chamber 108 save for a gap around the chamber perimeter and sufficient space is left in the chamber for accommodating portions of the heat exchanger not taken up by the heat pipe. However, it should be understood that other lengths, widths and thicknesses could be used. The planar heat pipe 500 preferably has a plurality of holes 502 through which the support pins 112 can pass. The spacing for these holes 502 can be chosen as desired by a practitioner to balance the need for adequately supporting the heat pipe 500 and transparent cover 106 against the desire to maximize the heat absorbing surface area of the planar heat pipe 500.

The planar heat pipe 500 preferably includes a portion 902 (see FIGS. 4 and 9(a)-(b)) that is to be located inside the heat exchanger 110 for delivering heat to the heat transfer fluid inside the heat exchanger 110. Thus, the planar heat pipe 500 is preferably configured to deliver heat absorbed by exposed surfaces of the heat pipe to portion 902 inside the heat exchanger 110 to heat the heat transfer fluid.

The heat pipe's upper and bottom surfaces 116 and 118 can be sheets of a heat absorbent material (e.g., copper, aluminum, titanium, etc.). As is understood in the heat pipe art, these sheets can be brought together at their ends leaving a chamber between them that is subjected to a vacuum pressure. Furthermore, a coating can be applied to the outer surfaces of the heat pipe to enhance the heat pipe's heat absorption and heat rejection properties. A coating on the upper surface 116 of the heat pipe can enhance heat absorption and heat rejection, while a coating on the bottom surface 118 can serve to reflect heat that would otherwise be radiated out the bottom surface 118 back into the heat pipe. The inventors note that an appropriate heat pipe 500 can be built by a heat pipe manufacturer according to the desired parameters of a practitioner such as the thickness of the heat pipe walls (e.g., the thickness of the copper sheets or the like), the expected operating temperature for the heat pipe, the coatings that are desired for the heat pipe's outer surfaces, the amount of vacuum pressure expected within chamber 108, the design/shape of the heat exchanger 110 and the expected angle of use (e.g., whether the heat pipe is expected to be positioned in an effectively flat orientation or a more tilted orientation).

While the exemplary planar heat pipe 500 of FIG. 5 is shown to have a flat surface, it should be understood that the surface of the planar heat pipe need not be entirely flat. For example, as shown in FIGS. 6(a)-(d), a plurality of cylindrical heat pipes 600 can be arranged together to approximate a planar heat pipe 500. FIG. 6(a) is a perspective view of a plurality of cylindrical heat pipes arranged to approximate a planar heat pipe. FIG. 6(b) is a cross-sectional view of such a planar heat pipe. FIG. 6(c) is a top view of such a planar heat pipe. It should be understood that any of a variety of techniques can be used to join the cylindrical heat pipes 600 together to approximate the planar heat pipe. For example, welding or soldering could be used. Also, a joining member 602 can be used to bundle the cylindrical heat pipes 600 together, as shown in FIG. 6(d). FIG. 6(d) also depicts how one end of the cylindrical heat pipes would engage with (and preferably be positioned inside the heat exchanger 110.

Further still, other cross-sectional shapes can exist on the surface of the planar heat pipe if desired by a practitioner. For example, a series of rounded ridges 702 and troughs 704 may be positioned on the exposed surface of the planar heat pipe 700 of FIG. 7. FIG. 7 shows a cross-sectional view of an exemplary planar heat pipe 500 with rounded ridges and troughs. Similarly, more pointed ridges and troughs could be used as shown in FIG. 8(d) which reside on the upper surface 116 sheet (with vacuum space 800 residing between the upper sheet 116 and bottom sheet 118). These ridges and troughs could be beneficial for capturing sunlight when the sun is at lower elevations during the morning or early evening hours. As an additional example, a waffling or dimpling pattern 802 can be applied to the exposed surface of the planar heat pipe 500 of FIGS. 8(a) and (b). FIG. 8(a) shows a cross-sectional view of such an exemplary planar heat pipe 800, while FIG. 8(b) shows a top view. An example of an additional waffling pattern is shown in FIG. 8(c). Moreover, the upper and lower surfaces 116 and 118 of a heat pipe can be stamped together to leave a number of spaced half-cylinder vacuum chamber 800 as shown in FIG. 8(e). While the examples of FIGS. 8(c) and (d) show a small gap between the upper sheet 116 and lower sheet 118 of the heat pipe, it should be understood that the upper and lower sheets 116 and 118 could be effectively made flush at the trough points such that a gap only exists between the two sheets at the ridge portions if desired.

FIG. 9(a) shows an exemplary embodiment for a manifold heat exchanger 110. The main frame of FIG. 9(a) shows a bottom view of the exemplary manifold heat exchanger 110 while the left frame shows a side view of the manifold heat exchanger 110 in FIG. 9(a). In this embodiment, the intake and outtake ports 114a and 114b extend out the bottom of the heat exchanger 110 at opposite lateral end portions of the heat exchanger 110. With reference to the embodiment shown in FIGS. 1(a)-(c), the heat exchanger embodiment of FIG. 9(a) has the ports 114a and 114b extending downward from the bottom of the heat exchanger 110 rather than extending outward from the rear of the heat exchanger 110. The heat exchanger includes an internal reservoir chamber 900. An end portion 902 of the heat absorber 102 is also positioned inside the chamber 900. It should be noted that this end portion 902 may be possess a geometrical configuration or pattern that is designed to enhance heat transfer between the heat pipe 500 and the heat transfer fluid flowing inside the chamber 900.

Thus, as heat is absorbed by the heat absorber 102, heat will be delivered to the heat absorber portion 902 inside the heat exchanger chamber 900. Then, as heat transfer fluid enters intake port 114a it becomes heated heat transfer fluid as it passes the heat source of the heat absorber portion 902. This heated heat transfer fluid then exits the chamber 900 via outtake port 114b. FIG. 11(a), which is a cross-sectional side view along a short dimension of an exemplary heat exchanger 110 such as the one shown in FIG. 9(a), generally illustrates this process.

FIG. 9(b) shows another exemplary embodiment for a manifold heat exchanger 110. The main frame of FIG. 9(b) shows a bottom view of this exemplary manifold heat exchanger 110 while the left frame shows a side view of the manifold heat exchanger 110 in FIG. 9(b). The embodiment of FIG. 9(b) shows a dual chamber bidirectional flow manifold heat exchanger 110. With this embodiment, the reservoir chamber 900 comprises an upper chamber 900a separated from a lower chamber 900b by a dividing wall or the like. A plurality of intake ports 114a1 and 114a2 and a plurality of outtake ports 114b1 and 114b2 are shown, with one intake/outtake port pair serving the upper chamber 900a while the other intake/outtake port pair serves the lower chamber 900b. In this example, the multiple intake ports and outtake ports are shown extending from the bottom of the heat exchanger 110. However, this need not be the case.

By having multiple chambers, the heat exchanger 110 can accommodate multiple flows of heat transfer fluid, including flows of heat transfer fluid in opposite directions. As such, the heat exchanger embodiment of FIG. 9(b) can be referred to as a dual chamber bi-directional flow heat exchanger 110. FIG. 11(b) generally depicts how these bidirectional fluid flows could be heated inside the chambers 902a and 902b for the heat exchanger 110 of FIG. 9(b). FIG. 11(c) generally depicts the bidirectional flow directions as well. Piping can deliver heat transfer fluid flowing in one direction to the intake port 114a1 for the upper chamber 900a while piping can deliver heat transfer fluid flowing in the other direction to the intake port 114a2 opposite port 114a1. The heat transfer fluid would thus flow in opposite directions through the heat exchanger. This is shown in FIGS. 11(b) and (c) by fluid flow 1102 through the upper chamber 900a in a first direction and a fluid flow 1104 through the lower chamber 900b in the opposite direction. This permits the return flow path of heat transfer fluid to a central source to stay within the insulating confines of the heat exchanger to a greater extent than having an exposed return path would provide. FIG. 11(d) generally illustrates a bidirectional fluid flow through an exemplary array of solar collectors 100a, 100b and 100c. In this example, fluid enters the array at point 1110, traverses the three solar collectors through the upper flow paths 1102 and returns to the source at point 1112 through lower flow paths 1114. Short piping that passes through holes 310 in the solar collector sidewalls 122 can connect adjacent solar collectors, and a short U-connector pipe 1114 can be used at the end point of the final solar collector 100c in the array to return the fluid exiting the upper flow path 1102 of solar collector 100c to the lower flow path 1104 of solar collector 100c.

It should be understood that a practitioner may choose to position the heat exchanger's ports 114 in any of a number of configurations. FIG. 10(a) illustrates a top view of an exemplary heat exchanger 110 where the ports 114 extend laterally outward from the sides of the heat exchanger 110. FIG. 10(b) illustrates a side view of an exemplary heat exchanger 110 where one port (e.g., port 114a) extends laterally outward from a side of the heat exchanger 110 while the other port (e.g., port 114b) extends downward from the bottom of the heat exchanger 110. FIG. 10(c) illustrates a top view of an exemplary heat exchanger 110 where one port (e.g., port 114a) extends laterally outward from a side of the heat exchanger 110 while the other port (e.g., port 114b) extends out from the rear of the heat exchanger 110. However, it should be understood that still other configurations are possible, particularly if multiple intake and outtake ports are used. Further still, it should be understood that the ports 114 can be positioned as desired along the length, width and height of the heat exchanger 110, although it is preferred that the ports 114 be positioned to provide a flow path for the heat transfer fluid to absorb heat from the heat source of the heat absorber portion 902.

FIG. 13(a) depicts an embodiment where a plurality of the solar collectors 100 disclosed herein are arranged in an array 1300. It should be understood that number of solar collectors 100 to include in an array is up to a practitioner. To form the array, the solar collectors 100 are preferably arranged together like puzzle pieces. With reference to the embodiment of FIGS. 3(a)-(f), piping 1302 for delivering heat transfer fluid to and taking heat transfer fluid away from the heat exchangers 110 can be positioned to pass through hole 310 and enter the open path area 430, traverse the open path area 430 and exit the hole 312 on the opposite side of the solar collector. Such an arrangement would permit multiple solar collectors 100 to positioned largely flush against each other to maximize space usage. Similarly, by alternating male and female connection ports between adjacent solar collectors, another largely flush engagement could be achieved.

A trunk pipe line 1302 preferably connects different arrangements of solar collectors 100 in the array 1300. A plurality of branch pipe lines 1320 and 1322 can sprout from each trunk line 1302 (preferably perpendicularly). This is shown in FIG. 13(b). Branch line 1320 provides heat transfer fluid to solar collectors 100 in a first flow direction while heat transfer fluid flows through branch lines in the opposite direction. As such, it can be seen that the exemplary embodiment of FIG. 13(b) is a suitable candidate for the dual chamber bidirectional flow heat exchanger 110 of FIG. 9(b). Thus, each branch line 1320/1322 has a plurality of serially connected solar collectors where the heated heat transfer fluid output of one solar collector is fed to the next solar collector down the line (including along the return path of line 1322). Trunk line 1302 preferably comprises a main pipe 1310 where fluid flows in a first direction and a second main pipe 1312 where fluid flows in the opposite direction. If desired, a U-connector piece can join the output of one end of pipe 1310 to the input of the nearby end of pipe 1312. Alternatively, separate sources and terminations could be used at each end of pipes 1310 and 1312 if desired.

It should be understood that for each of illustration, the piping 1310 and 1312 in FIGS. 13(a) and (b) is shown to reside outside the footprint of the solar collectors 100. However, if desired, the piping 1310 and 1312 can run through the frame sidewalls (see hole 310) via open path area 430 to reduce the amount of exposed piping and maximize space usage. Further still, it should be understood that it is desirable to provide insulation around the pipes 1310 and 1312 so as to reduce heat loss.

FIG. 13(c) depicts another exemplary array embodiment wherein different arrays 1300 are arranged in super-arrays 1350 that surround a central collection unit 1352. The central collection unit 1352 can serve as a junction where a plurality of relatively lower pressure fluid pipelines are joined in a relatively higher pressure fluid pipeline. If desired, the joined high pressure fluid flow can then be delivered via piping to a desired location from the central collection unit 1352. Alternatively, electrical generating components and/or energy consumption components can be placed at or near central collection unit 1352 to use the energy received from the solar collectors 100. In the example of FIG. 13(c), each central collection unit 1352 connects with 4 arrays 1300 as shown in FIG. 13(c) to form a super-array 1350.

To structurally gang solar collectors 100 together in an array 1300, a structural member 1360 (e.g., a steel bar) such as that shown in FIG. 13(d) can be used. As shown in the top view of FIG. 13(d), a plurality of solar collectors 100 can be attached to structural bars 1360 (e.g., via bolts or the like connected to the solar collector sidewalls 122). These ganged solar collectors can then be put into place in the field as a single unit with a reduced number of crane operations to lift the solar collectors and put them in position. Furthermore, the ganged solar collectors are preferably pre-plumbed with the necessary piping and other connections so that only connections between pipe ends need to be performed in the field. Each solar collector array preferably includes the corresponding piping for lines 1310 and 1312, a vacuum pipe, and a conduit for low voltage electrical connections as discussed below.

An array 1300 can be positioned at a location where the solar collectors will receive sufficient sunlight to produce a heated output for delivery to downstream energy consumers. For example, arrays 1300 can be placed on the roof of large buildings such as shopping malls. As another example, arrays 1300 can be placed at sunny locations in remote areas such as deserts or beneath existing power lines. Furthermore, each solar collector 100 can be supported by a tilting mechanism (see FIG. 14) having a plurality of columns 1400 that are configured to elevate or tilt the solar collector at a desired angle to increase the capture rate of solar energy. If desired, this tilting mechanism could include tracking capabilities (where the elevation of the array would be adjusted throughout the day to better catch sunlight) as is known in the art. For example, one common positioning technique is to deploy solar collectors in a largely north/south orientation, tilt the solar collectors to maximize sunlight capture and then adjust the solar collector's angle and orientation to track the sunlight throughout the day.

FIGS. 15(a) and (b) depict exemplary techniques for maintaining vacuum pressure within the solar collector chambers 108 when a plurality of solar collectors 100 are combined in an array. The inventors believe that embodiments such as the ones described by FIGS. 15(a) and (b) will permit more effective field maintenance of the vacuum pressure inside the solar collector chambers. With reference to FIG. 15(a), a main pump line 1500 is shown. This main line 1500 is preferably connected to a vacuum pump that establishes a vacuum pressure. A plurality of branch pump lines 1502 can sprout off the main line 1500 as shown in FIG. 15(a). Each branch line 1502 connects to a plurality of solar collectors 100 in an array. A solenoid valve 1504 can be positioned along a branch line 1502 upstream from a plurality of solar collectors connected to that branch line 1502, as shown in FIG. 15(a). This solenoid valve 1504 is configured with backflow prevention features as is known in the art to effectively provide isolation for the downstream solar collectors 100 in case there is a fault elsewhere in the vacuum system. That is, should there be a break somewhere along the main line 1500, the solenoid valve 1504 will operate to protect the vacuum pressure inside the downstream solar collectors 100. Such operation could be achieved in any of a number of ways. For example, the solenoid valves' default state after vacuum pressure has been established can be in a closed state so as to provide isolation by default between segmented solar collectors. Then, these solenoid valves can be actuated to an open state as needed should there be a need to adjust the vacuum pressure in the affected solar collectors. Alternatively, the solenoid valves' default state can be in an open state. Then, should the system detect a fault in vacuum pressure, select solenoid valves would be actuated to a closed state to achieve isolation of desired solar collectors.

One or more sensors 1506 for sensing the temperature and pressure in branch line 1502 and/or fluid branch lines 1320/1322 can be employed to detect whether there are any problems in the vacuum system and whether the solar collectors are operating as desired. Based on the data sensed by sensors 1506 and processed by a controller (not shown), the solenoid valves can be activated to open/close as desired. For example, to increase the vacuum pressure in the downstream solar collectors, the corresponding solenoid valve 1504 can be actuated (via a signal on a low voltage data/control line 1508) to the open position so that the vacuum pump can increase the vacuum pressure. It should also be understood that the sensors 1506 can be positioned in or on the solar collectors 100 themselves to provide such data to a controller via data/control line 1508 (e.g., as shown in connection with the FIG. 15(b) embodiment discussed below).

FIG. 15(b) depicts an exemplary embodiment where the vacuum isolation is provided on a solar collector-by-solar collector basis. With this exemplary embodiment, the solenoid valve 1504 is used as the valve in the tube valve 124 for connecting each solar collector to the branch pump line 1502. Control signals on line 1508 can then be used to operate each individual solenoid valve as desired.

Furthermore, the inventors note while the exemplary solar collector embodiments of FIGS. 1(a)-(c) and FIGS. 3(a)-(f) were configured such that the heat exchanger 110 was positioned at an end portion of the chamber 108 with reference to the long dimension of the solar collector, a solar collector 100 can also be arranged such that the heat exchanger 110 is positioned at an end portion of the chamber 108 with reference to the short dimension of the solar collector, as shown in FIG. 16, which is a top view of such a solar collector arrangement.

Further still, the inventors note that the solar collector's bottom member 120 and sidewalls 122 can be encased in insulation 1700 to further protect the solar collector from heat loss to the outside environment if desired by a practitioner (see FIGS. 17(a) and (b)). Varying thickness of insulation could be used by a practitioner depending on the practitioner's desires (e.g., 18 inches). More, the insulation should be able to accommodate the expected high temperatures that the solar collectors would exhibit when in use. Furthermore, a practitioner may choose to provide multiple layers of different types of insulation around the solar collectors. For example, the insulation may include a first insulation layer contacting the frame that is capable of withstanding high temperatures and a second insulation layer around the first insulation layer that need not be configured to high temperature duty (e.g., a foam-type insulation).

The inventors also note that, if desired by a practitioner, a plurality of heat absorbers 102 (e.g., planar heat pipes 500) could be positioned in a single evacuated chamber, as shown in FIGS. 18(a)-(b). Embodiments such as these would permit larger solar collector length/width dimensions and possibly result in a more efficient use of space with less material costs. The ports on the heat exchangers 110 can directly connect with each other inside the evacuated chamber 108, thereby eliminating any piping outside the chamber 108 that would otherwise be needed to connect the heat exchangers for different heat absorbers 102. Also, it should be noted that the spacing between the various heat exchangers 110 is shown for ease of illustration. A practitioner may choose to provide a more flush engagement of the different heat exchangers against each other so as to maximize the use of space inside the chamber. Furthermore, it should be understood that a single heat exchanger 110 could be used to receive the end portions 902 of the different heat absorbers 102 if desired. Further still, as shown in FIG. 18(b), one or more structural members 1800 can be installed inside the chamber 108 to provide structural support for the solar collector's frame (such support may be necessary given the increased dimensions that could arise in such embodiments. The example of FIG. 18(b) shows a support beam member 1800 extending along the long dimension of the solar collector inside the chamber 108 at around the mid-point of the chamber 108 with respect to the short dimension. It should be understood that such a beam 1800 could also be run along the short dimension at around the mid-point of the chamber 108 with respect to the long dimension. Similarly, two support members 1800 could be run perpendicular to each other along the long and short dimensions if desired. Such a support member 1800 need not seal off one portion of the chamber 108 from another—it need only provide structural support for the frame. The chamber 108 in such an embodiment would be a single evacuated chamber.

While specific embodiments of the invention have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of invention which is to be given the full breadth of the claims appended and any and all equivalents thereof. It should further be understood that the embodiments disclosed herein include any and all combinations of features as disclosed herein and/or described in any of the dependent claims.

Claims

1. An apparatus for collecting solar energy, the apparatus comprising:

a planar heat pipe configured to absorb heat;

a frame surrounding the planar heat pipe, the frame forming a chamber within which at least a portion of the heat pipe resides; and

a transparent cover engaged with the frame to enclose the chamber; and

wherein the chamber comprises an evacuated chamber.

2. The apparatus of claim 1 wherein the entire heat pipe resides within the evacuated chamber, the apparatus further comprising:

a heat exchanger in cooperation with the heat pipe, the heat exchanger comprising a heat exchanger chamber and an output, the heat exchanger being configured to receive and transfer the heat absorbed by the heat pipe to the output, wherein the heat exchanger chamber is positioned inside the evacuated chamber.

3. The apparatus of claim 2 wherein the heat exchanger further comprises a heat transfer fluid for entering the heat exchanger chamber to absorb heat from the heat pipe and transporting the absorbed heat to the output.

4. The apparatus of claim 2 wherein the heat exchanger chamber comprises a first heat exchanger chamber and a second first heat exchanger chamber.

5. The apparatus of claim 5 wherein the heat exchanger comprises a multi-chamber bidirectional flow manifold heat exchanger.

6. The apparatus of claim 2 wherein the frame comprises a bottom member and a plurality of sidewalls, the apparatus further comprising a reflector positioned and configured to reflect energy radiated by the heat pipe back to the heat pipe.

7. The apparatus of claim 6 wherein the reflector is positioned inside the chamber.

8. The apparatus of claim 7 wherein the reflector comprises a reflector positioned between the heat pipe and the bottom wall.

9. The apparatus of claim 8 wherein the reflector comprises a mirror.

10. The apparatus of claim 9 wherein the mirror comprises a coating, the coating configured to reflect infrared energy.

11. The apparatus of claim 6 wherein the heat pipe does not contact the frame.

12. The apparatus of claim 2 further comprising a plurality of the planar heat pipes positioned inside the evacuated chamber.

13. The apparatus of claim 1 wherein the heat pipe comprises a plurality of holes, wherein the frame comprises a bottom member, the apparatus further comprising:

a plurality of free-floating pins positioned to support the heat pipe without the heat pipe contacting the frame, the pins having a bottom portion for engaging the bottom member and a top portion for engaging the transparent cover, and wherein the pins pass through the heat pipe holes.

14. The apparatus of claim 13 wherein the pins further comprise a shoulder portion upon which the heat pipe is supported.

15. The apparatus of claim 14 wherein the pins are formed from a material that is substantially non-heat-conducting.

16. The apparatus of claim 14 wherein the pins comprise ceramic pins.

17. The apparatus of claim 1 further comprising a tube valve passing through the frame for connection to a vacuum pump line, the vacuum pump line having a solenoid valve connected thereto, the solenoid valve connecting the vacuum pump line to another vacuum pump line, the solenoid valve configured to maintain a vacuum pressure inside the chamber and isolate the chamber from the another vacuum pump line in response to a solenoid valve control signal.

18. The apparatus of claim 1 further comprising a tube valve passing through the frame for connection to a vacuum pump line, the tube valve comprising a solenoid valve for connecting the chamber to a vacuum pump line, the solenoid valve configured to maintain a vacuum pressure inside the chamber and isolate the chamber from the vacuum pump line in response to a solenoid valve control signal.

19. The apparatus of claim 1 wherein the frame has a rectangular shape.

20. The apparatus of claim 19 wherein the transparent cover has a surface area portion through which light enters the chamber, and wherein the heat pipe has a surface area that takes up around 95% of the transparent cover surface area portion.

21. The apparatus of claim 1 further comprising a sealant layer between the frame and the transparent cover for creating a seal between the transparent cover and the frame.

22. The apparatus of claim 1 wherein the planar heat pipe comprises a plurality of cylindrical heat pipes that are arranged to approximate a flat plate.

23. The apparatus of claim 1 wherein the planar heat pipe has a plurality of ridges and troughs on an upper surface thereof.

24. A method for collecting solar energy, the method comprising:

absorbing heat with a solar collector, the solar collector comprising a planar heat pipe positioned inside an evacuated chamber formed by a frame and a transparent cover.

25. The method of claim 24 wherein the heat absorbing step comprises absorbing the heat with the heat pipe, the method further comprising:

transferring the absorbed heat to a heat exchanger, the heat exchanger having a heat exchanger chamber, the heat exchanger chamber also positioned inside the evacuated chamber.

26. The method of claim 25 further comprising:

heating a heat transfer fluid inside the heat exchanger chamber with the transferred heat; and

transporting the heated heat transfer fluid out of the heat exchanger chamber.

27. The method of claim 25 wherein the heat exchanger chamber comprises a first heat exchanger chamber and a second first heat exchanger chamber.

28. The method of claim 27 further comprising providing a bidirectional flow of heat transfer fluid through the first and second heat exchanger chambers.

29. The method of claim 25 further comprising:

reflecting energy radiated by the heat pipe back to the heat pipe with a reflector.

30. The method of claim 29 wherein the reflector is positioned inside the evacuated chamber.

31. The method of claim 30 wherein the reflector is positioned between the heat pipe and a bottom member of the frame.

32. The method of claim 31 wherein the reflector comprises a mirror.

33. The method of claim 32 wherein the mirror comprises a coating, the coating configured to reflect infrared energy.

34. The method of claim 25 wherein the heat pipe does not contact the frame.

35. The method of claim 24 wherein the heat pipe comprises a plurality of holes, the method further comprising:

supporting the heat pipe within the frame with a plurality of free-floating pins that pass through the heat pipe holes, the pins positioned to support the heat pipe without the heat pipe contacting the frame, the pins having a bottom portion for engaging a bottom member of the frame and a top portion for engaging the transparent cover.

36. The method of claim 35 wherein the pins further comprise a shoulder portion upon which the heat pipe is supported.

37. The method of claim 36 wherein the pins are formed from a material that is substantially non-heat-conducting.

38. The method of claim 36 wherein the pins comprise ceramic pins.

39. The method of claim 24 wherein the solar collector comprises a tube valve passing through the frame, the method comprising:

connecting the tube valve to a vacuum pump line, the vacuum pump line having a solenoid valve connected thereto, the solenoid valve connecting the vacuum pump line to another vacuum pump line; and

controlling the solenoid valve to maintain a vacuum pressure inside the chamber and isolate the chamber from the another vacuum pump line in the event of a fault along the another vacuum pump line.

40. The method of claim 24 wherein the solar collector comprises a tube valve passing through the frame, the tube valve comprising a solenoid valve, the method comprising:

connecting the tube valve to a vacuum pump line; and

controlling the solenoid valve to maintain a vacuum pressure inside the chamber and isolate the chamber from the vacuum pump line in the event of a fault along the vacuum pump line.

41. The method of claim 24 wherein the frame has a rectangular shape.

42. The method of claim 41 wherein the transparent cover has a surface area portion through which light enters the chamber, and wherein the heat pipe has a surface area that takes up around 95% of the transparent cover surface area portion.

43. The method of claim 24 further comprising:

creating a seal between the transparent cover and the frame with a sealant layer.

44. The method of claim 24 wherein a plurality of the planar heat pipes are positioned inside the evacuated chamber.

45. An apparatus for collecting solar energy, the apparatus comprising:

a planar heat pipe configured to absorb heat, the heat pipe having a plurality of holes;

a frame, the frame comprising a bottom member and a plurality of sidewalls forming a chamber within which the heat pipe resides;

a transparent cover engaged with the frame to enclose and seal the chamber, wherein the chamber comprises an evacuated chamber;

a heat exchanger in cooperation with the heat pipe, the heat exchanger comprising a heat exchanger chamber and an output, the heat exchanger being configured to receive and transfer the heat absorbed by the heat pipe to the output, wherein the heat exchanger chamber is positioned inside the evacuated chamber; and

a plurality of free-floating pins positioned to support the heat pipe without the heat pipe contacting the frame, the pins having a bottom portion for engaging the bottom member and a top portion for engaging the transparent cover, and wherein the pins pass through the heat pipe holes.

46. An apparatus for collecting solar energy, the apparatus comprising:

a heat absorber configured to absorb heat;

a frame adapted to form a chamber within which at least a portion of the heat absorber resides;

a transparent cover engaged with the frame to enclose the chamber, the cover configured to permit solar energy to enter the chamber and impact the heat absorber; and

a reflector positioned and configured to reflect energy radiated by the heat absorber back to the heat absorber.

47. The apparatus of claim 46 wherein the reflector is positioned inside the chamber.

48. The apparatus of claim 47 wherein the frame comprises a bottom member and a plurality of sidewalls, and wherein the reflector is positioned between the heat absorber and the bottom wall.

49. The apparatus of claim 48 wherein the reflector comprises a mirror.

50. The apparatus of claim 48 wherein the reflector comprises a coating, the coating configured to reflect infrared energy.

51. The apparatus of claim 50 wherein the coating comprises a coating applied to a surface below the heat absorber.

52. The apparatus of claim 50 wherein the heat absorber has a bottom surface, and wherein the coating comprises a coating applied to the heat absorber bottom surface.

53. The apparatus of claim 47 wherein the frame comprises a bottom member and a plurality of sidewalls, and wherein the reflector is positioned on an internal face of at least one of the sidewalls.

54. The apparatus of claim 48 further comprising a coating applied to an underside of the transparent cover, the coating configured to pass energy from outside the apparatus into the chamber and also configured to reflect energy radiated by the heat absorber back to the heat absorber.

55. The apparatus of claim 46 further comprising:

a heat exchanger in cooperation with the heat absorber, the heat exchanger configured to receive and transfer the heat absorbed by the heat absorber to an output.

56. The apparatus of claim 55 wherein the heat absorber comprises a planar heat pipe.

57. The apparatus of claim 56 wherein the planar heat pipe comprises a flat plate heat pipe.

58. The apparatus of claim 55 wherein the chamber comprises an evacuated chamber.

59. A method comprising:

within a solar collector having a heat absorber positioned inside a chamber, reflecting energy radiated by the heat absorber back to the heat absorber with a reflector.

60. The method of claim 59 wherein the reflector is positioned inside the chamber.

61. The method of claim 60 wherein the solar collector comprises a bottom member, a plurality of side walls and a transparent cover for defining the chamber, and wherein the reflector is positioned between the heat absorber and the bottom member.

62. The method of claim 61 wherein the reflector comprises a mirror.

63. The method of claim 61 wherein the reflector comprises a coating, the coating configured to reflect infrared energy.

64. The method of claim 63 wherein the heat absorber comprises a planar heat pipe.

65. The method of claim 61 wherein the chamber comprises an evacuated chamber.

66. The method of claim 60 wherein the reflector is positioned on an internal face of at least one of the sidewalls.

67. The method of claim 60 wherein the reflector comprises a coating applied to an underside of the transparent cover, the coating configured to pass energy from outside the apparatus into the chamber and also configured to reflect energy radiated by the heat absorber back to the heat absorber.

68. A method comprising:

within a solar collector having a heat absorber positioned inside a chamber, the chamber being formed by a bottom member, a plurality of side walls and a transparent cover, positioning an energy reflector between the heat absorber and the bottom member.

69. The method of claim 68 further comprising:

reflecting energy radiated by the heat absorber back to the heat absorber with the energy reflector.

70. The method of claim 68 wherein the energy reflector comprises a mirror.

71. The method of claim 68 wherein the energy reflector comprises a coating, the coating configured to reflect infrared energy.

72. An apparatus comprising:

a flat plate solar collector having an evacuated chamber within which a heat absorber and a reflector are positioned, the reflector being positioned beneath the heat absorber for reflecting energy radiated by the heat absorber back to the heat absorber.

73. The apparatus of claim 72 wherein the reflector comprises a mirror, the mirror having a coating, the coating configured to reflect infrared energy.

74. An apparatus for collecting solar energy, the apparatus comprising:

a heat absorber configured to absorb heat;

a frame surrounding the heat absorber, the frame forming a chamber within which the heat absorber resides;

a transparent cover engaged with the frame to enclose and seal the chamber, wherein the chamber comprises an evacuated chamber; and

a heat exchanger in cooperation with the heat absorber, the heat exchanger comprising a heat exchanger chamber and an output, the heat exchanger being configured to receive and transfer the heat absorbed by the heat absorber to the output, wherein the heat exchanger chamber is positioned inside the evacuated chamber.

75. The apparatus of claim 74 wherein the heat exchanger chamber comprises a heat transfer fluid for absorbing heat from the heat absorber and transporting the absorbed heat to the output.

76. The apparatus of claim 75 wherein the heat exchanger chamber comprises a first chamber and a second chamber, the first and second chamber configured to separately heat different flows of heat transfer fluid.

77. The apparatus of claim 76 wherein the heat exchanger chambers are configured to receive a bidirectional flow of heat transfer fluid in the first and second chambers.

78. The apparatus of claim 74 wherein the heat exchanger chamber does not contact the frame.

79. The apparatus of claim 78 comprises a standoff sleeve positioned to connect the heat exchanger chamber to the frame, the standoff sleeve comprising a material that is resistant to heat conduction.

80. The apparatus of claim 79 wherein the standoff sleeve material comprises a ceramic.

81. A method for collecting solar energy, the method comprising:

absorbing heat with a heat absorber, wherein the heat absorber is positioned inside an evacuated chamber formed by a frame and a transparent cover of a solar collector; and

transferring the absorbed heat to a heat exchanger, the heat exchanger comprising a heat exchanger chamber, wherein the heat exchanger chamber is also positioned inside the evacuated chamber.

82. The method of claim 81 further comprising:

heating a heat transfer fluid inside the heat exchanger chamber with the transferred heat; and

transporting the heated heat transfer fluid out of the heat exchanger chamber.

83. The method of claim 82 wherein the heat exchanger chamber comprises a first chamber and a second chamber, the method further comprising separately heating different flows of heat transfer fluid within the first and second chambers.

84. The method of claim 83 wherein the flows comprise bidirectional flows of heat transfer fluid.

85. The method of claim 81 wherein the heat exchanger chamber does not contact the frame.

86. The method of claim 85 further comprising insulating the heat exchanger chamber with a standoff sleeve positioned to connect the heat exchanger chamber to the frame, the standoff sleeve comprising a material that is resistant to heat conduction.

87. The method of claim 86 wherein the standoff sleeve material comprises a ceramic.

88. An apparatus for collecting solar energy, the apparatus comprising:

a heat absorber configured to absorb heat, the heat absorber comprising a plurality of holes;

a frame, the frame comprising a bottom member and a plurality of sidewalls that form a chamber within which the heat absorber resides;

a transparent cover engaged with the frame to enclose and seal the chamber, wherein the chamber comprises an evacuated chamber; and

a plurality of free-floating pins positioned to support the heat absorber without the heat absorber contacting the frame, the pins having a bottom portion for engaging the bottom member and a top portion for engaging the transparent cover, and wherein the pins pass through the heat absorber holes.

89. The apparatus of claim 88 wherein the pins further comprise a shoulder portion upon which the heat absorber is supported.

90. The apparatus of claim 89 wherein the pins are formed from a material that is substantially non-heat-conducting.

91. The apparatus of claim 89 wherein the pins comprise ceramic pins.

92. The apparatus of claim 88 further comprising a cushion layer disposed on at least one of the ends of the pins.

93. A method for collecting solar energy, the method comprising:

absorbing heat with a heat absorber wherein the heat absorber is positioned inside an evacuated chamber formed by a frame and a transparent cover of a solar collector, the heat absorber comprising a plurality of holes; and

supporting the heat absorber within the frame with a plurality of free-floating pins that pass through the heat absorber holes, the pins positioned to support the heat absorber without the heat absorber contacting the frame, the pins having a bottom portion for engaging a bottom member of the frame and a top portion for engaging the transparent cover.

94. The method of claim 93 wherein the pins further comprise a shoulder portion upon which the heat pipe is supported.

95. The method of claim 94 wherein the pins are formed from a material that is substantially non-heat-conducting.

96. The method of claim 94 wherein the pins comprise ceramic pins.

97. The method of claim 93 further comprising cushioning an engagement between the pins and at least one of the bottom member and the transparent cover with a cushion layer disposed on at least one of the ends of the pins.

98. An apparatus for collecting solar energy, the apparatus comprising:

a vacuum pump line for connection to a vacuum pump;

a plurality of branch vacuum pump lines for connection to the vacuum pump line;

a plurality of solar collectors connected to at least one of the branch vacuum pump lines to form an array of solar collectors, each solar collector comprising an evacuated chamber, a heat absorber positioned at least partially inside the chamber, and a tube valve for connection to the at least one branch vacuum pump line; and

a solenoid valve connecting the vacuum pump line with the at least one branch vacuum pump line, the solenoid valve being configured to open and close to maintain a vacuum pressure inside the chambers of the solar collectors in the array and isolate the solar collectors in the array from the vacuum pump line in response to a control signal.

99. A method for collecting solar energy, the method comprising:

collecting energy with a plurality of solar collectors, each solar collector comprising an evacuated chamber and a heat absorber positioned inside the evacuated chamber; and

using at least one solenoid valve to maintain a vacuum pressure inside the evacuated chambers and isolated the evacuated chambers from an upstream vacuum pressure fault.

100. The method of claim 99 wherein the solenoid valve using step comprises using a solenoid valve that connects a branch vacuum pump line to a vacuum pump line, wherein the solar collectors are connected to the branch vacuum pump line to create a vacuum pressure inside the chambers.

101. The method of claim 99 wherein the solenoid valve using step comprises using the solenoid valve to directly connect the solar collectors to a vacuum pump line.

102. An apparatus for collecting solar energy, the apparatus comprising:

a plurality of branch pipe lines;

a trunk pipe line configured to deliver heat transfer fluid to the plurality of branch pipe lines; and

a plurality of solar collectors serially connected to at least one of the branch pipe lines to form an array of solar collectors.

103. The apparatus of claim 102 wherein each solar collector comprises a multi-chamber bidirectional manifold heat exchanger that is configured to receive a flows of heat transfer fluid in a first direction and a second direction.

104. The apparatus of claim 102 wherein the plurality of solar collectors formed in the array are joined together by a structural member.

105. The apparatus of claim 102 wherein a plurality of the arrays are formed into a super-array around a central collection unit.

106. The apparatus of claim 102 wherein each solar collector in the array comprises an open path area on an underside thereof for receiving piping to serially connect the solar collectors in the array.

107. The apparatus of claim 102 wherein each solar collector comprises: (1) a planar heat pipe configured to absorb heat, (2) a frame surrounding the planar heat pipe, the frame forming a chamber within which at least a portion of the heat pipe resides, and (3) a transparent cover engaged with the frame to enclose the chamber, wherein the chamber comprises an evacuated chamber.

108. A method comprising:

delivering heat transfer fluid from a trunk pipe line to a plurality of branch pipe lines, wherein at least one of the branch pipe lines comprises a plurality of solar collectors serially connected to form an array of solar collectors; and

collecting energy with the array of solar collectors to heat the delivered heat transfer fluid.

109. The method of claim 108 wherein each solar collector comprises a multi-chamber bidirectional manifold heat exchanger, the method further comprising each solar collector in the array receiving flows of heat transfer fluid in a first direction and a second direction.

110. The method of claim 108 further comprising joining the solar collectors in an array together with a structural member.

111. The method of claim 108 further comprising forming a plurality of the arrays into a super-array around a central collection unit.

112. The method of claim 108 wherein each solar collector in the array comprises an open path area on an underside thereof for receiving piping to serially connect the solar collectors in the array.

113. The method of claim 108 wherein each solar collector comprises: (1) a planar heat pipe configured to absorb heat, (2) a frame surrounding the planar heat pipe, the frame forming a chamber within which at least a portion of the heat pipe resides, and (3) a transparent cover engaged with the frame to enclose the chamber, wherein the chamber comprises an evacuated chamber.