Patent Application
20080216823
Solar energy absorption structures or panels for absorbing solar energy are known in the art. Such conventional solar energy absorption structures typically include a body or frame and an energy absorption fluid flowing through the body. Many of these conventional solar energy absorption structures have various shortcomings.
For example, conventional solar energy absorption structures are typically made of materials—such as optical glass, aluminum, or copper—which can result in structures that are often difficult to install, heavy and costly to manufacture.
Further, many of the components of conventional solar panels have solid black absorbing surfaces that can often overheat, thereby resulting in extreme stress on the solar panels. More specifically, when exposed to the sun, a conventional solar panel can heat up to between 300° F. and 400° F. if energy absorption fluid has been drained from the panel, or if energy absorption fluid is not being continuously pumped through the panel, e.g., during fluid stagnation periods. In order to prevent damage to or extreme stress on the panels, conventional solar panels must be made of materials that are able to resist such high temperatures. Such materials are typically expensive.
Another known shortcoming of conventional solar energy absorption structures is that energy absorption fluid has a propensity to overheat when exposed to sunlight during fluid stagnation periods. Also, in some climates, such as Northern climates, antifreeze is added to the energy absorption fluid to prevent damage. However, during fluid stagnation periods, the antifreeze can be heated to levels that can ruin or degrade the antifreeze. In the event the antifreeze becomes degraded, the fluid can become acidic and dissolve the components of the absorber and other parts of the system and piping, thereby requiring maintenance. Moreover, damage to a fluid can be difficult to detect unless checked by a professional. Accordingly, if the fluid is not checked regularly, just one instance of the fluid overheating can permanently damage the system.
Another known shortcoming of conventional solar energy absorption structures is that many such structures cannot produce uniform heat transfer at low cost.
Described herein are various embodiments of solar energy apparatus that overcome many of the disadvantages and shortcomings of conventional solar energy absorption structures.
In certain embodiments of the invention described herein, solar energy absorbers that may comprise transparent plastic material are disclosed. The dimensions of the solar energy absorbers may be minimized so as to reduce the amount of energy absorption fluid, such as black fluid, flowing through the solar energy absorber. Reflective coatings, selective coatings for improved absorption and reflectors may also be included in the solar energy absorbers.
In other embodiments of the invention described herein, headers for solar energy absorbers that may comprise transparent plastic materials and reflective coatings are disclosed.
In other embodiments of the invention described herein, housings for absorbers that may comprise foam or transparent plastic materials are disclosed. The housings may also include reflective coatings. The housings may also include elements for holding an absorber in position.
In still other embodiments of the invention described herein, combined absorber and absorber housings are disclosed. The combined absorber and absorber housings may comprise transparent plastic material or foam.
In yet another embodiment of the invention described herein, a solar absorptive fluid circulation system is disclosed. The solar absorptive fluid circulation system may include a monitoring system for monitoring the temperature of the system and valves that may be opened to drain the system of black fluid should the system exceed a predetermined temperature.
Embodiments of the present disclosure are shown in the accompanying drawings.
Described herein are embodiments of solar energy apparatus for collecting and distributing solar energy. The solar energy apparatus include a solar collector system through which a solar absorptive heat transfer fluid, such as black fluid, is allowed to flow. The solar energy collector system may include a solar energy collection portion and a solar energy transfer portion. As the solar absorption fluid flows through the solar energy collection portion, it contacts sun light and collects solar energy. The solar absorption fluid then flows through the solar energy transfer portion where the solar energy collected in the solar absorption fluid is utilized immediately or is transferred to a thermal energy storage system, such as a water heating or building heating system, via a thermal exchange element or a heat collection storage container. Continuing from the thermal energy transfer portion, the absorptive fluid returns to and again flows through the solar energy collection portion to restart the solar energy collection and distribution process in a closed loop. Accordingly, the solar energy apparatus provides continuous collection and distribution of solar energy.
With reference to
The absorber 20 also includes a bottom header 60 at the bottom end 38 of the absorber 20 having an open end 70 and a closed end 72 and a top header 62 at the top end 42 of the absorber 20 having an open end 70 and a closed end 72. Closed ends 72 may be open if there are a plurality of absorbers 20 placed in series or in parallel so that fluid may flow between absorbers. Also, the closed end 72 of the top header 62 and the closed end 72 of the bottom header 60 do not need to be on the same side of the absorber. The closed ends 72 may be on opposite sides of the absorber so that flow goes in one side of the bottom header 60 and out the opposite side of the top header 62, which creates more uniform fluid flow.
The bottom header 60 and top header 62 are in fluid communication with the space between the front panel 22 and rear panel 24. The bottom header 60 may include a fluid valve 113 and the top header may include an air valve 115.
In operation, energy absorptive fluid, such as black fluid, is flowed into the open end 70 of the bottom header 60. The bottom header 60 fills with energy absorptive fluid and eventually begins to fill the space between the front panel 22 and the rear panel 24. Once the fluid has reached the top end 42 of the absorber 20, the fluid flows into the top header 62 and out the opening 70.
As shown in
With reference to
The absorber 20 includes a plurality of fluid chambers 34 in which a heat exchange medium, such as solar absorptive heat transfer fluid, is contained, absorbs sunlight, and is circulated. The fluid chambers 34 include the areas defined between the inward surfaces of the front and rear panels 22, 24 and either adjacent internal members 32 or an internal member 32 and an inward surface of an edge member 30. The fluid chambers 34 each have an inlet opening 36 proximate the bottom end 38 shown in
The absorber 20 has an overall width B and overall depth C. The front panel 22 and rear panel 24 are spaced apart from each other a distance E, i.e., the fluid chambers 34 have a depth or height E. The edge members 30 can have the same general length A (see
The front panel 22 and rear panel 24 are each made from a clear material, such as optically transparent plastic, which permits energy emitted from the sun to pass through and heat the heat exchange medium. The plastic may have any or all of the characteristics of plastic as set forth in Table 1 below.
The rear panel 24 includes a light reflective layer 44 positioned adjacent an outer surface of the rear panel. For example, in some implementations, the light reflective layer 44 is a metallic layer, such as a thin piece of sheet metal, or foil, coupled to, such as by being adhered to, or otherwise bonded to, the outer surface of the rear panel 24. In some implementations, the reflective surface is spaced apart from the outer surface of the rear panel 24 such that an insulating layer of air can be positioned between the reflective surface and the rear panel.
In one specific exemplary implementation, the overall length A is approximately 96 inches, the overall width B is approximately 48 inches and the overall depth C is approximately 0.13 inches. The thickness D of the front panels 22 and rear panel 24 is approximately 0.02 inches and the panels are spaced apart a distance E of approximately 0.09 inches. The distance G is approximately 0.5 inches and the distance H is approximately 1.0 inches. In this and other implementations, the weight of the absorber plus absorptive fluid is less than 30 pounds.
In some implementations, the components of the absorber can be made using plastic extrusion processes. For example, one or more of the front and rear panels can be a polycarbonate panel, such as manufactured by Gallina USA, of Janesville, Wis.
Referring to
In
In addition to fluid chambers formed between two plates to form a solar energy absorber as described above, the solar energy absorber may have other configurations. Referring to
The outer conduit 330 is coupled to the inner conduit 320 by posts 324 circumferentially spaced about and secured to an external surface of the inner conduit and an internal surface of the outer conduit. In some implementations, the posts 324 are elongate and extend a length of the center conductor 310. In other implementations, the posts 324 are discrete spacers, such as columns or blocks, positioned at incremental locations along the length of the center conductor 310. Although three posts 324 are shown in the illustrated embodiments, in other embodiments, more or less than three posts are used.
In an alternative implementation, the posts 324 can be disks having a central hole with a diameter that is approximately equal to the outer diameter of the inner conduit and an outer diameter that is approximately equal to the inner diameter of the outer conduit such that the disks rest between the inner and outer conduits and maintain the inner and outer conduits in coaxial alignment.
In one embodiment, the ratio of the length of each post 324 divided by the cross-sectional area of each post 324 is maximized in order to minimize heat lost through conduction as heat moves axially up the posts.
The center conductor collection portion 310 includes a region 350 defined between the inner and outer conduits 320, 330 within which a vacuum is created to reduce convective heat losses. In some implementations, an infrared reflective coating may be applied to the interior surface of the outer conduit 330 to increase infrared reflection back into the fluid passageway 322 when visible and UV light is converted into heat inside fluid passageway 322. With specific reference to
In some embodiments, a portion of the lower half of any of the surfaces may be coated with a light-reflecting surface so that light reflects back to sky rather than passing through center conductor 310 when heat absorptive fluid is absent. In certain implementations, one or more of the components of the center conductor 310 can be made of plastic, glass, plastic coated glass, or any combination thereof.
Referring to
In some embodiments, the collector 300 may be drained of fluid to reduce the overall temperature of the collection portion 310 in the event the overall temperature exceeds a predetermined threshold. For example, in one specific implementation, the system drawing heat from the collector 300 is a steam system and the thermal mass is a block of inexpensive metal. The solar absorptive heat transfer fluid can be a high temperature oil compound with Ttm
Because the overall temperature of the collector 300 can be controlled, expensive high-temperature glass or plastics need not be used, and less expensive glass and plastic substitutes can be used.
The inner conduit, outer conduit and posts may each be made of optically transparent plastic material. The plastic material may be, for example, polycarbonate plastic. The plastic may have any or all of the characteristics set forth in Table 1 below.
According to another embodiment,
When in operation, solar absorptive heat transfer fluid flows through the center conduit 830 as described in greater detail below. Depending on the level of desired insulation within the assembly, the sealed space between center conductor 830 and insulating tube 810 may contain air, a noble or inert gas such as argon, or a vacuum.
The insulating tube 810 and the center conductor 830 run the full length of the absorber 801. In one embodiment, the diameter of the insulating tube 810, I_d, equals twice the diameter, C_d, of the center conductor 830. Incident solar energy enters the center conductor 830 directly or reflects off reflector 840 to enter the center conductor 830. The placement of the reflector 840 directly below the center conductor 830 and with walls extending from the base of the insulating tube 810 to its median point at a 45 degree angle make possible the collection of nearly all incident rays, both direct and diffuse, from sunrise to sunset with solar absorptive heat transfer fluid present in the center conductor 830. Absorptive materials cover only half the surface of the collector, yet the collector collects nearly all the incident solar energy. When no solar absorptive heat transfer fluid is present, the collector assembly reflects all incident solar energy. Reflector 840, which reflects all incident solar energy, returns incident radiation back to sky.
Referring to
Outer coating 831 may be applied to the center conduit 830 to decrease permeability to air or noble or inert gas, and to reduce the reflection of incident energy. The material forming the center conduit 830 must allow the transmission of solar energy to either the solar absorptive heat transfer fluid, when present, or to or from the reflector 840 with little on no attenuation. Center conduit 830 may be extruded from glass, plastic, or other suitable solar transmissive material. The plastic material may have any or all of the characteristics described in Table 1 below. Inner coating 833 must stop solar absorptive heat transfer fluid from entering the material of center conduit 830. Without a coating, the solar absorptive heat transfer fluid flowing through the center conduit 830 may, over time, enter the material of the center conduit 830 and begin the discoloration process. As the center conduit 830 discolors, it absorbs incident solar energy even with no solar absorptive heat transfer fluid present. This effect causes the temperature of the center conduit 830 to rise with no solar absorptive heat transfer fluid present. With sufficient discoloration, the temperature of the center conduit 830 may rise to a point where the material fails. Coating 833 prevents or minimizes staining, and thereby prevents or minimizes material failure.
Materials of similar or differing temperature coefficients of expansion may be utilized to form the insulating tube 810 and center conduit 830 depending on the application.
The reflector 840 resides at the base of the assembly. It may be formed of a single piece of material either by cutting and bending, or it may be extruded. Surface 841 must be mirror-like to reflect all incident solar energy. Coating may be applied to surface 843 to block infrared radiation from escaping. Polished aluminum, plated plastic, or other suitable material may be used to form the reflector.
The spacer 820 serves to position the center conductor 830 within the insulating tube 810. It also matingly receives the reflector 840 in slots 823. The spacer material may be plastic, or other suitable substance with high thermal resistance to minimize the conduction of heat from the center conductor 830 to the insulating tube 810 to ambient. The plastic material may have any or all of the characteristics described in Table 1 below. A coating 821 may be applied to the spacer 820 to reflect incident solar energy to either the reflector 840 or the center conduit 830. Coating 821 may stop incident reflections to increase transmissivity through spacer 820.
As shown in
As shown in
Referring now to
Coupler 825 attaches each absorber end to its respective header 860 or 861 shown in
Still referring to
Referring to
In operation, filling the center conduits of the absorber assemblies 801 with solar absorptive heat transfer fluid makes the collector solar absorptive. The solar absorptive heat transfer fluid enters through bottom header 861, fills the absorber center conduits of the absorber assembly 801, then exits through top header 860. As noted previously, the solar absorptive heat transfer fluid flow direction may be reversed.
In one specific exemplary implementation, the length A is approximately 96 inches; the width B is approximately 48 inches; the absorber thickness is approximately 0.02 inches; C_d is 0.5 inches: I_d is 1.0 inch; N is 48, and L_s is 12 inches. The collector assembly may weigh less than approximately 25 pounds, hold less than 5 gallons of fluid, operate with vacuum insulation, and be manufactured inexpensively.
In another specific exemplary implementation, the length A is approximately 20 feet; the width B is approximately 10 feet; the absorber thickness is approximately 0.02 inches, C_d is 3 inches; I_d is 6 inches; N is 20; and L_s is 12 inches. The center conduit makes use of the configuration defined by 830.1. This collector assembly, which collects solar energy over an approximate 200 square foot area, assembles in a modular fashion. The entire assembly may weigh less than 200 pounds, holds less than 20 gallons of fluid, operates with air as the insulator, and may be manufactured and installed inexpensively.
Referring now to
The fluid reservoir portion 64 defines a generally circular fluid passageway 68 extending from an open end 70 to a closed end 72 (as shown in
The absorber attachment portion 66 extends away from the external surface of the fluid reservoir portion 64 and has a generally rectangular shape having a height K and a depth L. In some embodiments, the height K is approximately 1.0 inches and the depth L is approximately 0.5 inches. The absorber attachment portion 66 can have any of various other shapes, such as, for example, trapezoidal.
An elongate slot 74 is formed, such as by milling or an intrinsic slot made by extrusion, in the absorber attachment portion 66 and penetrates an external surface of the absorber attachment portion. The slot 74 extends less than the length of the header 60 and is approximately equal to or slightly longer than the overall width B of the absorber 20, has a width approximately equal to or slightly wider than the overall depth C of the absorber, and has a depth equal to or less than the depth L. In this manner, the slot 74 is configured to matingly receive the end of the absorber 20 within the absorber attachment portion 66. The absorber can be retained within the elongate slot 74 through use of an adhesive or other known bonding technique. Absorber 20 may slide into attachment portion 66 which forms a seal with a gasket or other known “slip in” methods. When attached to each other, the absorber 20 and top and bottom headers 60, 62 can be referred to as an absorber assembly.
In certain implementations, a fluid inlet feed slot 76 is formed in the header in fluid receiving communication with the fluid passageway 68 and fluid expelling communication with the fluid chambers of the absorber 20 when the absorber is received within the elongate slot 74. In other words, the fluid inlet feet slot 76 provides a channel between the fluid passageway 68 and the fluid chambers of the absorber 20 through which solar absorptive heat transfer fluid is permitted to flow. The fluid inlet feed slot 76 slot extends a substantial portion of the elongate slot 74 such that each of the fluid chambers of the absorber 20 are in at least partial fluid receiving communication with the fluid inlet feed slot 76. In the illustrated embodiment, the fluid inlet feed slot 76 is a single continuous slot. In other embodiments, the fluid inlet feed slot can be multiple slots spaced apart along the length of the elongate slot.
In certain implementations, the top and bottom headers 60, 62 are plated with a reflective layer, such as a metallic layer, to reflect solar energy from the sun and prevent solar radiation from contacting any solar absorptive heat transfer fluid flowing through the headers or solar absorptive heat transfer fluid residually remaining within the headers in the event solar absorptive heat transfer fluid is drained or otherwise removed from the panels as will be described in more detail below.
In certain applications, absorber assemblies such as those described above are placed in housings. Referring now to
In some implementations, the absorber 20 is attached to, such as adhesively bonded to, an upper surface of the bottom wall 106 such that the absorber and base 102 form a unified assembly. In other implementations, the absorber 20 is secured to the base 100 via the mating engagement between the sides 108 of the base 100 and the headers without any direct attachment of the absorber to the base.
The base 102 acts as an insulator to reduce conductive, convective and radiated heat losses from the solar absorptive heat transfer fluid flowing through the absorber 20. Moreover, the base 102 can provide structural support and rigidity for enduring the environmental conditions in which the collector portion will operate. Accordingly, in some embodiments, the base 102 is made from structural foam, such as polyurethane foam. The thickness of the bottom wall 106 and side walls 108 is determined based on the desired maximum heat loss through the absorber 20 and the R-Value of the foam. For example, in certain implementations, the bottom wall 106 or side walls 108 can be two-inch thick inexpensive polyurethane foam having an insulating value of R-3 or greater per inch. In one embodiment, the inexpensive foam has an R-10 insulation value.
Typically, inexpensive foams such as polyurethane foam tend to melt at temperatures around 200° F. Accordingly, conventional solar collectors would require more expensive foams capable of operating at higher temperatures, or a “buffer insulation” between the absorber and the foam, commonly associated with such conventional collectors. As will be described in more detail below, the ability of the solar energy apparatus described herein to control operating temperatures allows for the use of lower cost foam materials relative to conventional solar collectors.
In some embodiments, the portions of the base 102 and side walls 108 that may be exposed to solar radiation are plated or painted with a metallic layer to reflect the radiation and prevent UV damage to the base.
The cover assembly 104 includes a cover 110 coupled to the top surfaces of the side walls 108 and cover supports 112 positioned within the recess 109 between the cover 110 and the absorber 20. The cover 110 may hermetically seal off an insulation chamber 114 defined between the side walls 108, bottom wall 106, cover 110, and absorber 20. In some implementations, a seal or flexible adhesive is positioned between the cover 110 and the side walls 108 and cover supports 112 to attach the cover to the side wall and cover supports and to sealingly enclose the insulation chamber 114. The insulation chamber 114 can include dead air or a noble or inert gas, such as Argon, to better insulate the absorber from the environment. The cover 110 can be sealed to the top surfaces of the side walls 108 with any of various adhesives or with other mechanical assemblies, such as an aluminum U-channel perimeter frame and gaskets. Such a U-channel can also provide an attachment point for coupling the collector to a mounting surface, such as a roof.
Each cover support 112 can be an elongate beam, such as a plastic I-beam, having a first side attached to the cover 110 and a second side opposite the first side attached to or simply touching the absorber 20. The cover supports 112 couple the cover 110 to the absorber 20 to provide structural support to the cover 110.
As described above, in some implementations, the absorber is coupled to the base 102 and the cover 110 via the cover supports 112 by an adhesive or other known method of attachment e to form an integrated structural solar energy connector capable of withstanding harsh environmental conditions.
In specific implementations, the absorber 20, cover 110, cover supports 112 are made of a optically transparent plastic. The plastic can be any of various plastics characterized by any of various parameter values or performance characteristics depending on the desired application, manufacturing costs or other variables. Listed in Table 1 below are several clear plastic parameters, associated general descriptions of the parameter, parameter values according to various embodiments, and associated comments. The parameters, parameter descriptions, parameter values, and comments listed in Table 1 are associated with the characteristics of exemplary types of plastics that can be used to form the plastic components of some embodiments of the solar energy apparatus described herein. In other embodiments, the plastic components can be made of plastics having performance characteristics outside of the value ranges specified in Table 1.
Referring to
In some embodiments, the plastic components can be made from Lexan SLX2432T, manufactured by General Electric. In some embodiments, other plastics, such as polycarbonate and acrylic plastics, can be used.
Prior to collecting solar energy, the collection portion does not contain solar absorptive heat transfer fluid. In this non-operational state, solar energy penetrates the cover 110, front panel 22, absorber chamber 34, and rear panel 24 and is reflected by the reflective layer 44 to the atmosphere with minimal absorption. Further, solar energy is reflected off the reflective layers on the base 102 and bottom and top headers. Because little to no solar energy is absorbed in this non-operational state, the temperature of the components of the collection portion 12 and the overall temperature of the collection portion remains relatively unchanged, i.e., approximately equal to ambient temperature.
In the illustrated embodiment, the shell 560 includes a generally hollow, rectangular-shaped shell having spaced-apart front and rear walls 511, 512 and two side walls 515 positioned around opposite sides of and coupling the front and rear walls. The shell 560 includes spaced-apart top and bottom open ends 513, 514, respectively.
The end caps 510, 520 are coupled to the bottom and top ends 514, 513, respectively, of the shell 560 to partially encapsulate the headers 540, 550. The end caps 510, 520 can be attached to the ends of the shell 560 with a suitable adhesive or other known connecting method. For example, although not shown, in some implementations, the shell 560, headers 540, 550 and end caps 510, 520 can be coupled together using flexible gaskets, joints, bellows, or other known flexible attachment method to seal and allow movement between the shell, headers, and end caps. Such a flexible attachment method can allow for independent movement between the shell 560 and an absorber housed therein, such as when the temperatures of the various components of the collector assembly 500 are different or changed relative to each other.
As shown in
As shown in
The shell 560 allows light to transmit through to an absorber 562 and, in some embodiments, is made primarily of a UV resistant plastic or glass. The plastic material may have any or all of the characteristics described in Table 1 above. As with the absorbers previously described, the absorber 562 contains solar absorptive heat transfer fluid when in a solar energy absorption mode and does not contain solar absorptive heat transfer fluid when in a solar energy reflection mode.
The shell 560 includes upper and lower insulation cavities 564, 565, respectively. The upper insulation cavities 564 are defined between the front wall 511 of the shell and the absorber 562 and the lower insulation cavities are defined between the rear wall 512 and the absorber. The cavities 564, 565 provide dead air insulation above and below the absorber 562, respectively. In some embodiments, the lower insulation cavities 565 can be filled with an insulative material, such as foam beams or solid foam, to improve bottom insulation performance and strengthen the shell 560.
The front and rear panels of absorber 562 have a thickness D, which is defined above in relation to
In some implementations, the thickness of the shell walls is greater than the thickness D of the absorber front and rear panels. Such a configuration can improve the structural performance of the shell and allow the shell to better withstand adverse environmental conditions.
As shown in
In one specific exemplary implementation, the length A is approximately 96 inches; the width B is approximately 48 inches; the thickness D is approximately 0.01 inches; the height E is approximately 0.10 inches; the width S is approximately 0.25 inches; the distance H is approximately 3.00 inches; and the height L is approximately 3.00 inches. The collector assembly 500 may weigh less than approximately 15 pounds, hold less than approximately 1.5 gallons of solar absorptive heat transfer fluid, and be manufactured inexpensively.
As shown in
As shown in
Each flexible beam 741 has a length that is substantially greater than its thickness. Likewise, the length of the flexible beam 741, because of its serpentine shape, significantly exceeds its height. In certain implementations, the thickness of each support member 741 may be made considerably less than the total length of the serpentine support member. Since a long, but thin, member offers high thermal resistance per unit length, the ratio of the length of flexible beam 741 divided by the material thickness of the supports may be large to minimize conduction of heat from the absorber 721 to the outer panels 711 and 731. By intention, they form a very poor thermal connection to track 740.
While the flexible beam 741 is shown having a serpentine shape, any other flexible shape which accommodates lateral stress without failure may also be used for the flexible beam. For example, the flex beams may be comprised of two flexible beams opposing each other and bowing away from each other, like two opposing leaf springs.
Referring back to
An infrared reflective coating 712 may be used to stop heat from being radiated to outside space when the collector 700 collects solar energy. The coating 712 passes incident energy to the absorber 721 while reflecting infrared emitted from the absorber 721 back to the absorber. The bottom surface of the top panel 711 may also include an ultraviolet blocker.
Specific coatings on the interior chambers, formed by E_shell and S_shell, of the top panel 711 determine part of the heat loss characteristics and thereby part of the insulation characteristics of the top panel 711. An optically transmissive coating applied to the interior chambers allows the top panel 711 to be filled with a noble or inert gas, such as argon, or support a vacuum to increase the thermal resistance over air filling the chamber. The interior chambers may also be made from an optically transmissive material, thereby eliminating the need for a coating. One embodiment uses a coating which entraps a noble or inert gas in the top panel 711. Significant increases in thermal resistivity occur under such a condition. A similar, or possibly different, coating may be applied to prevent gasses from entering the top panel 711. This coating permits the creation of a vacuum. In case of a vacuum, a getter may be inserted inside chambers of the top panel 711 Very high thermal resistance exists with a vacuum present on the interior of the top panel 711. Heat only conducts outward through the thin vertical support members of 711, where the ratio of E_shell to the thickness, D is large. The top panel's thermal conductivity is small compared to conventional solar collector top glazing, which is frequently glass. The top panel material may be low thermal conductivity plastic. The interior chambers may also be coated with an anti-staining material.
Coatings and additives upon and within bottom panel 731 optimize thermal performance. An infrared reflective coating 732 may be used to stop heat from being radiated to space when the collector 700 collects solar energy. The coating 732 returns infrared emitted from the absorber 721 back to the absorber. Coating 732 may also be an ultra violet, V, blocker with antireflective properties.
Coating 730 provides additional infrared reflectivity and may also have antireflective properties. Coating 730 and 732 may or may not be identical.
Specific coatings on the interior chambers, formed by E_shell and S_shell, of the bottom panel 731 determine part of the heat loss characteristics and thereby part of the insulation characteristics of the bottom panel 731. A coating applied to the interior chambers allows the bottom panel 731 to be filled with a noble or inert gas, such as argon, or support a vacuum to increase the thermal resistance over air filling the chamber. One embodiment uses a coating which entraps a noble or inert gas in the bottom panel 731. Significant increases in thermal resistivity occur under such a condition. A similar, or possibly different, coating may be applied to prevent gasses from entering the bottom panel 731. This coating permits the creation of a vacuum. In the case of a vacuum, a getter may be inserted inside chambers of bottom panel 731. Very high thermal resistance exists with a vacuum present on the interior of the bottom panel 731, heat only conducts outward through the thin vertical support members of 731, where the ratio of E_shell to the thickness, D is large. The thermal conductivity of the bottom panel is comparable to the thermal conductivity of the insulation commonly used on the bottom sides of the conventional solar collectors. The bottom panel material may be low thermal conductivity plastic. The interior chambers may also be coated with an anti-staining material.
The side panel 751, while differing in dimension from the bottom panel 731, uses similar coatings and exhibits similar performance.
While not shown in any drawings, insulation (fiberglass, foam, or other suitable type) may be inserted in the spaces between the absorber 721 and the bottom panel 731 to further increase collector efficiency. This insulation must be expandable and compressible or allow enough space to not interfere with the operation of the flex beams 741. Insulation may be applied outside of shell 702 on the bottom 731 and the sides 751 and 752 for additional heat loss reduction.
Coatings and additives upon and within the absorber panel 721 optimize performance. The antireflective nature of the coating maximizes the amount of solar energy passing into the absorber panel 721, when filled with solar absorptive heat transfer fluid, over a range of incident sun angles. A reflective coating 722 or reflective material applied by adhesive or other know means reflects the full spectrum of incident energy upwards back to sky with no solar absorptive heat transfer fluid present in the absorber 721. The combination of solar absorptive heat transfer fluid and a bottom reflective surface make the absorber 721 either solar absorptive when the solar absorptive heat transfer fluid is present, or solar reflective when no solar absorptive heat transfer fluid exists in the absorber 721.
A coating on the interior chambers, formed by E_abs and S_abs, prevents the absorption of the solar absorptive heat transfer fluid into the materials that form the absorber 721. Without any coating as the collector ages, the solar absorptive heat transfer fluid may enter the materials forming the absorber 721 and begin a discoloration process. As the absorber 721 discolors it absorbs incident solar energy even with no solar absorptive heat transfer fluid present. This effect causes the temperature of the absorber 721 to rise when exposed to solar radiation. With sufficient absorption of solar absorptive heat transfer fluid, the temperature of the absorber 721 may rise to a point where the materials forming the absorber 721 fail. The interior coating of the absorber 721 prevents staining and thereby material failure.
With specific reference to
As shown in
In one specific exemplary implementation, the length A is approximately 96 inches; the width B is approximately 48 inches; the material thickness D is approximately 0.01 inches; the height E_abs is approximately 0.16 inches; the width S_abs is approximately 0.16 inches; the width S_shell is approximately 0.50 inches and E_shell is approximately 0.50 inches; the distance H is approximately 12.00 inches; and the height L is approximately 3.00 inches. The collector assembly 700 may weigh less than approximately 25 pounds, hold less than approximately 3.0 gallons of solar absorptive heat transfer fluid, and be manufactured inexpensively.
In other embodiments described herein, the absorber is built into the housing. Referring to
Base 212 is generally rectangular with a rear wall 216, a top wall 217, and a bottom wall 219 projecting transversely from the rear wall. An absorber recess 220 is defined between the rear wall 216 and the side walls 218 shown in
Referring to
The large elongate foam ribs 214 project transversely relative to the rear wall 216 and extend from the top end 230 to the bottom end 232 of the body 210 shown in
Referring to
The collection portion 202 also includes an outer optical layer 250 supported by and attached to the large elongate foam ribs 214 and side ribs 222. The optical layer 250 and dead-air, or inert gas in some implementations, located within insulation chambers 252 defined between the inner optical layer 240, the outer optical layer 250, and adjacent large ribs act as an insulator in the same manner as the cover 110 and insulation chamber 114. As with collection portion 12, the inner and outer optical layers 240, 250, which may be made of a plastic material having some or all of the characteristics described in Table 1 above, provide two layers of insulation between the environment and the solar absorptive heat transfer fluid circulating through the fluid chambers. The two layers of insulation assist in keeping heat stored in the solar absorptive heat transfer fluid from being lost via radiation, conduction, or convection into the outside environment.
In some embodiments, the base 212, large ribs 214, 222, and small foam ribs 215, 223 are plated with a reflective layer or coating to reflect sunlight to keep the components of the collection portion 202 cool and, in some embodiments, keep ultraviolet light from damaging the plastic or insulation. Additionally, the reflective layer can enhance solar energy absorption by redirecting the sunlight striking the ribs into solar absorptive heat transfer fluid contained within the fluid chambers, thereby increasing the overall efficiency of the collector 200.
Referring to
The top layer 410 and upper middle layer 414, and bottom layer 412 and lower middle layer 416, can be coupled together in a spaced apart relationship via a plurality of spacers 420. The spacers 420 can run a length of the collection portion 402 such that vacuum chambers 422 are formed between respective layers and spacers. The air within the vacuum chambers 422 can be vacated to form a vacuum within each of the vacuum chambers. Getters may be placed inside each vacuum chamber. The vacuum chambers may also be chambers filled with dead air, inert gas or noble gas, rather than a vacuum.
The upper and lower middle layers 414, 416 are coupled together in a spaced apart relationship via absorption chamber spacers 424. As with the spacers 420, the absorption chamber spacers 424 can extend a length of the collection portion 402 such that fluid chambers 426 are defined between the upper and lower layers 414, 416 and respective spacers 424. Although not shown, headers can be implemented at respective inlets and outlets to the chambers 426 and solar absorptive heat transfer fluid can be pumped into the chambers 426 via one header and out of the chambers via another header. Top and bottom headers may be recessed to allow only chamber 426 to connect to top and bottom headers.
As the solar absorption fluid flows between the headers and through the fluid chambers 426, it collects solar energy. The vacuum chambers 422 are vacated of air to create a vacuum that provides an insulating barrier for preventing conducted and convective heat losses from the solar absorptive heat transfer fluid as it flows through the fluid chambers 426.
In some implementations, the fluid chambers 426 have a depth of approximately 0.05 inches.
The collection portion 402 has a width Q and an overall depth R. In some implementations, the width Q is approximately 6.0 inches and the depth R is approximately 0.5 inches.
Although not specifically shown, in some implementations, the collection portion 402 may have foam insulation, e.g., a body, surrounding sides 430, ends (not shown) and bottom layer 412 of the collection portion. Also, a reflective layer 432, such as a plated metallic layer, may be coupled to the outer surface of the bottom layer 412 to reflect solar light when the fluid chambers 426 are not filled with solar absorption fluid. Further, although the implementation of the solar energy collector 400 illustrated in
In some embodiments, one or more collection portions can be arranged in series or parallel and coupled to each other directly or via common headers to effectively provide a wider solar energy absorption area.
Referring now to
Referring to
Referring now to
The frame assembly 620 includes a right side beam 622, left side beam 626, top beam 627, bottom beam 621, header mounting apertures 623, and top cover assembly supports 624. The header mounting apertures 623 receive the headers of the absorber assembly 610 and allow access to the headers from a location external to the collection system 600. The top cover assembly supports 624 are spaced-apart along the right and left side beams 622, 626 at appropriate intervals to align with mating structures on the top cover assembly as will be described in more detail below.
The foam assembly 630 comprises a generally rectangular sheet of foam 631 having a thickness that can be approximately half a total thickness R of the collector assembly 600. In some implementations, sealant materials can be applied to the surfaces of the sheet of foam 631 to reduce out gassing and enhance collector performance. In some implementations, the foam is encapsulated inside a high permeability substance such as plastic. The top surface of the sheet of foam 631 can also be coated with a reflective material 635 to reflect incident solar energy to the sky when fluid is not present in the absorber assembly 610 such that the internal temperature of the collector 600 is near ambient temperature. When fluid is present in the absorber assembly 610, the reflective material 635 can, in some implementations, effectively increase the absorption path length through the fluid by a factor of two. More specifically, incident solar energy that enters the fluid, but is not absorbed, reflects off the reflective material 635 and passes through the fluid a second time for reabsorption.
In some implementations, a moisture barrier 636 can be coated on the bottom of the sheet of foam 631 and right and left side beams 622 and 626 to prevent moisture from entering the foam and the assembly 600. The foam assembly 630 can have stepped ends or recesses 632, 633 for receiving the headers of the absorber assembly 610 and allowing for thermal expansion and contraction of the absorber as it heats up and cools down.
The frame assembly 620 is coupled to the foam assembly 630 and extends about a periphery of the foam assembly. In certain implementations, adhesives secure the frame assembly 620 to the foam assembly 630 to increase the overall strength of the collection assembly 600 and provide a seal between the frame assembly and the foam assembly.
In the illustrated implementation, the absorber assembly 610 rests upon, but is not attached to, the foam assembly 630. The foam assembly 630 vertically centers the absorber assembly 610 within the frame assembly 620. The absorber assembly 610, e.g., the absorber 613 and attached headers 611, 612, has a length less than the length A of the collector assembly 600 and a width less than the width B of the collector assembly such that the absorber assembly can fit into and float within the frame assembly 620. The floating nature of the absorber assembly 610 accommodates the thermal expansion and contraction of the absorber as hot solar absorptive heat transfer fluid is either added (expansion) or removed (contraction).
The top cover assembly 650 comprises a generally rectangular plastic sheet having a front wall 654, a top wall 652, and a bottom wall 651. In some implementations, the plastic may be polycarbonate and may have some or all of the characteristics described in Table 1 above. The top cover assembly 650 also includes beams 653 secured to an inner surface of the front wall 654 and extending parallel to the top and bottom walls 652, 651. The beams 653 can be secured to the front wall 654 by an adhesive or other known fastening method. The beams 653 are sized and shaped to be matingly received and laterally secured in slots formed in the top cover assembly supports 624 of the frame assembly 620. The top and bottom walls 652, 651 can, in some implementations, provide a weather seal and function as an end beam as well.
The collector assembly 600 includes a pair of top retainers or brackets 660 that at least partially secure the top cover assembly 650 to the frame assembly 620. In certain implementations, the top retainers 660 each include a central portion that extends lengthwise across the top cover assembly 650 between the top wall 652 and the bottom wall 651 and tabs that extend perpendicularly from the central portion and overlap the top and bottom walls. The tabs can be secured to the frame assembly 620 through use of a fastener or other coupling technique. When secured to the frame assembly 620, the top retainers 660 secure the top cover assembly 650 in compression. Accordingly, the top retainers 660 prevent front to rear motion of the top cover assembly 650 relative to the frame assembly 620 and the mating engagement between the support beam 653 and the cover assembly supports 624 prevents side to side motion of the top cover assembly relative to the frame assembly. In this manner, the top cover assembly 650 can maintain its structural integrity during severe weather conditions and not make contact with the absorber assembly 610.
As has been described above, the foam assembly 630 seals a bottom of the collector assembly 600, frame 620 seals the sides of the collector assembly, and the top 650 in conjunction with a gasket 640 seals the top of the assembly. Top retainers 660 compress the top 650 into the gasket 640 to form a complete perimeter seal.
In an exemplary implementation, the length A is approximately 102 inches; the width B is approximately 52 inches; the thickness C is approximately 0.16 inches; and the depth R is approximately 4 inches. The beams of the frame assembly 620 can have a thickness of approximately 1 inch and a height of approximately 4 inches. The support beams 653 can have a thickness of approximately 0.25 inches and a height of approximately 1.25 inches. The collector assembly 600 according to this exemplary implementation, can weigh less than approximately 30 pounds and may hold less than 3 gallons of solar absorptive heat transfer fluid.
In another exemplary implementation, the length A is approximately 106 inches; the width B is approximately 52 inches; the thickness C is approximately 0.25 inches; and the depth R is approximately 3.5 inches. The beams of the frame assembly 620 can have a thickness of approximately 1 inch and a height of approximately 4 inches. The foam assembly 630 is approximately 1.5 inches thick and the frame 620 is made from 1.0 inch by 3.5 inch PVC foam board. The absorber fluid chambers have a height E of approximately 0.25 inches and a width S of approximately 0.25 inches such that the absorber holds approximately 5 gallons of fluid.
In some embodiments, the collector assembly 600 provides several advantages. For example, collector assembly 600 is made of inexpensive materials such that the collector assembly is light, strong, weather-proof, easily installed, and aesthetically appealing. The extensive use of plastics and foam in the collector assembly reduces the weight of the assembly, which can lend to easy installation versus heavier collectors. Employing securing structures extending in the directions of dimensions A and B, as well as securing many of the components together using adhesives and fasteners, results in a structurally strong and long-lasting collector assembly. The full perimeter gasket, folded down top cover assembly, and the use of sealant adhesives produce weather tight seals. Additionally, the configuration of the collector assembly 600 resists rain, snow, sleet, and ice build-up by providing smooth top surfaces on which accumulation will readily slide. Also, as described above, the floating nature of the absorber facilitates connecting adjacent units (as will be described below) using simple flexible pipe. Aesthetically, there are no visible components other than the case top and sides. For example, all pipes, connectors, and roof mounts remain out of sight under the top cover assembly 650.
As shown in
The collector assembly 600 provides a combination of excellent energy collection performance, low manufacturing cost, and low installation cost. Accordingly, the collector assembly 600 can provide a considerable benefit to heat energy consumers.
Turning now to
The collector 10 includes a solar energy distribution system 14. The solar energy distribution system 14 includes a fluid pump 150, thermal storage mass 152 and fluid reservoir 154 in thermal communication with each other via heat exchanger 158. In some implementations, lines, as used herein, can be insulated conduits or pipes.
In operation, solar absorptive fluid, e.g., black fluid, which is stored in the reservoir 154, is pumped via lines 156 by pump 150 into the bottom header 60 at the open end 70 as indicated by directional arrow 161. Black fluid entering the bottom header 60 flows through the fluid passageway of the header and is initially contained within the header by the closed end 72 of the header. The fluid passageway of header 60 fills with black liquid until the fluid reaches the level of the infeed slot 76 shown in
Once the absorber chambers are filled, further pumping causes fluid to enter the top header 62 via an outfeed slot (not shown) similar to the infeed slot 76. The fluid passageway of the top header 62 fills with fluid in the same manner as the bottom header 60 until the passageway is at least partially full and fluid exits the top header via its open end 70 in a direction indicated by directional arrow 165. From the open end 70 of the top header 62, the fluid enters fluid line 157 and flows into heat exchanger 158, then returns to the reservoir 154. Storage mass 152, which can be any thermal mass commonly known in the art, stores heat for use by other devices (not shown) attached to the system.
Although
In operation, the pump 150 cyclically pumps fluid through the system such that fluid continuously flows upward through the absorber chambers. As black fluid flows through the absorber 20, solar energy from the sun is absorbed in the black fluid as thermal energy. The thermal energy is then transferred to the thermal energy storage mass 152 via header 62 and transport pipe 157, and heat exchanger 158.
The black, or sufficiently high absorptivity, fluid can have any of various properties or performance characteristics depending on the application or the structure of the collector, such as the depth of the absorber chambers. For example, listed in Table 2 below are several solar absorptive heat transfer fluid parameters, associated general descriptions of the parameters, parameter values according to various embodiments, and associated comments. The parameters, values, and comments listed in Table 2 are merely examples of parameters and parameter value ranges of implementations of solar absorptive heat transfer fluid that can be used in the solar energy apparatus described herein. In other embodiments, the solar absorptive heat transfer fluid can have performance characteristics that are not listed in Table 2 or fall outside of the value ranges specified in Table 2.
In some embodiments, the solar absorptive heat transfer fluid can be automotive automatic transmission fluid or propylene glycol, and the pigments or dyes can be conventional printing inks known in the art, carbon black, or other high absorbtivity substance, in powder form.
In some implementations, one or more of the surfaces of the base 102 defining the insulation chamber 114 shown in
In some embodiments, the solar energy collection system 10 can be operated to reduce the overall temperature of the system in the event the temperature of the absorber exceeds a predetermined threshold. As the solar absorptive heat transfer fluid circulates through the system, the thermal storage mass 152 will increase in temperature if the current energy taken out of the system, either directly or through a thermal heat exchange element or heat exchanger (not shown) in energy transfer communication with the thermal storage mass 152, is less than the current sun input that is converted into heat.
More specifically, the temperature of the fluid exiting the thermal storage mass 152 and entering the absorber 20 is approximately the same as the temperature of the thermal storage mass. The temperature of the fluid flowing through the absorber 20 increases to a new temperature greater than the temperature of the thermal storage mass 152 as it absorbs energy from the sun. The fluid exits the absorber at the new higher temperature and comes into heat exchange contact with the thermal storage mass, which causes the temperature of the thermal storage mass to increase. If energy is not transferred from the system, the fluid exits the thermal storage mass at a temperature greater than when it exited the thermal mass in the previous cycle. In other words, the temperatures of the components around the solar energy collection system loop can increase in tandem. Without some mechanism to reduce the sun input converted to heat or increase the current energy consumption, the temperature of one or more of the components around the loop may become dangerously high and cause long-term damage to some or all of the components including but not limited to any plastic, foam or fluid materials.
Based on the properties of the solar absorptive heat transfer fluid, plastic components and insulator components of the solar energy apparatus described herein, a predetermined maximum operating temperatures of the thermal storage mass Ttm
In some embodiments, a control system, such as system 167, is included. The system 167 may include a microcomputer that monitors temperature at one or more locations within the solar energy collection system 10 and opens the valve described above when the temperature at the one or more locations reaches a predetermined limit.
In some embodiments, the solar energy collection system can include an additional safety mechanism to prevent overheating of the collection system in the event the control system fails. The additional safety mechanism includes a snap switch, as commonly known in the art, which forces the fluid to drain from the absorber if the control system fails to open the valve. For example, in some implementations, the microcomputer of the control system can be programmed to open the valve at a Tc
After the fluid has drained from the absorber 20, the temperature of the collection system will decrease. Once the temperature of the solar energy collection system dips below a predetermined minimum temperature, the control system can close the fluid valve 113 and pump 150 can again circulate solar absorptive heat transfer fluid through the absorber 20, which causes the air within the absorber exit the absorber through the air valve 115. Once the absorber 20 is full, the air valve 115 can close.
In view of the many possible embodiments to which the principles of the disclosed solar energy apparatus may be applied, it should be recognized that the illustrated embodiments are only examples and should not be taken as limiting the scope of the disclosure.
It can thus be seen that at least certain of solar energy absorption apparatus embodiments set forth above can provide the following advantages among others:
This application claims the benefit of priority to U.S. Provisional Application No. 60/901,063, filed Feb. 12, 2007, the entirety of which is incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| 60901063 | Feb 2007 | US |
