Self-regulating solar thermal collector

Abstract

A self-regulating passive solar thermal collector optimizes temperature through automatic gas flow control, enhancing efficiency while protecting the system from overheating. A variable portion varies in volume with changing temperature of an enclosed gas. The varying starting at a predefined temperature and being over a given range of temperatures. The volume inside the variable portion varies with temperature due to the pressure of the enclosed gas, so as the temperature increases inside the sealed enclosure, the pressure increases inside the sealed enclosure, the volume decreases inside the variable portion, and correspondingly convective gas flow circulation increases in the sealed enclosure, thus increasing heat dissipation from the sealed enclosure to the environment.

Description

[0001] Self-Regulating Solar Thermal Collector

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to solar thermal energy systems, specifically to a self-regulating solar thermal collector.

[0004] BACKGROUND OF THE INVENTION

[0005] Refer to FIG. 1 , a diagram of a typical solar collecting system. Solar thermal units 200, also known as solar thermal collectors, solar energy collectors, solar panels, solar modules, or solar energy modules, convert solar radiation to thermal energy for a variety of applications 202 within residential or industrial structures. Typical applications include water heating 204, spaceheating 206, industrial process heating 208, solar cooling 210, and other applications 212. The solar collector includes a front 140 typically oriented for maximizing absorption of solar radiation (light). Opposite of the front 140 is a rear 141 of the collector. Typically the solar collector is deployed at an angle, with a bottom 142 relatively lower than a top 143 portion of the solar collector. A variety of solar thermal collectors are commercially available. Deployment, operation, and maintenance of conventional solar thermal collectors is well known in the industry. For clarity in this document, the singular term application is often used but does not imply limiting to a single application. One ordinarily skilled in the art will understand that multiple applications are included. In the context of this document, references to the term solar collecting system generally refer to one or more solar thermal collectors, application components, and related support components.

[0006] Refer to FIG. 3, a diagram of a cross-section view of a conventional solar thermal panel 201. Glass 100, for example, low emissivity (low-E) glass, is held by a frame 102 allowing LIGHT (as near IR and visible wavelength light are typically referred to in this context) to reach absorber 106. The absorber 106 is also known as an absorber plate. The absorber 106 is typically coated with an absorber coating (not shown). The absorber coating enhances absorption of light, and can have specific spectral reflectance and emittance characteristics. An exterior surface, or face, of the glass 100 is positioned for accepting solar radiation, or in general terms facing toward the source of solar radiation, and is also known as the surface of the collection panel. Circulation pipes 120 (end- view as shown by circles below / behind absorber 106) circulate a transfer fluid toabsorb heat from the absorber 106 and transfer the heat to applications. Note that connections between circulation pipes 120 and applications are not shown. Note also that for clarity a single solar panel is shown. Typically, multiple solar panels are used with serial and / or parallel connections between solar panels within a solar array. In a case like this, connections to and from circulation pipes of a single solar panel can be from or to (respectively) applications and / or one or more solar panels. Configuration and connection between solar panels and applications will be obvious to one skilled in the art. Internal insulation 107, such as Melamine insulation, provides an internal insulator between the back of the absorber 106 plate and the backside of the solar panel. Lateral (side) insulation 105 and rear thermal insulation 108 provide a thermal barrier on sides and back, respectively.

[0007] SUMMARY

[0008] According to the teachings of the present embodiment there is provided a solar energy module (205) for converting solar radiation to thermal energy, the module including a glass plate (100), a transparent insulation (104), a sealed enclosure (102+100+129) having an enclosed gas (112), an absorbing element (106) inside the sealed enclosure, the absorbing element configured to absorb the solar radiation transmitted via the glass plate then via the transparent insulation, the absorbing element in thermal contact with the enclosed gas, at least one circulation pipe (120) thermally coupled to the absorbing element, internal insulation (107) configured on a side of the circulation pipes opposite the transparent insulation, a front volume (124) associated with an area adjacent to the absorbing element and the transparent insulation, a back volume (130) associated with an area on a side of the internal insulation opposite the transparent insulation, at least one reversibly expandable variable portion (125) deployed in the back volume, at least one channel (123) respectively connecting each variable portion to an ambient environment outside the sealed enclosure, at least two ducts (127A, 127B) configured for convective gas flow between the front volume and the back volume, a back panel (129) on a side of the at least one variable portion opposite the internal insulation, wherein the at least one variable portion is configured to vary the volume of the variable portion in accordance with changing temperature of the enclosed gas, the varying starting at a predefined temperature and being over a given range of temperatures, and in an inflated state (125 A, 125C) the temperature of the enclosed gas is relatively lower, the volume of the variable portion is relatively larger, and restricting the convective gas flow via the ducts,and in a deflated state (125B, 125D) the temperature of the enclosed gas is relatively higher, the volume of the variable portion is relatively smaller, allowing the convective gas flow via the ducts, and heat dissipation from the enclosed gas via the back panel to the ambient environment outside the sealed enclosure.

[0009] According to the teachings of the present embodiment there is provided a self-regulating solar energy module (205) for converting solar radiation to thermal energy, the module including a glass plate (100), a sealed enclosure (102+100+129) having an enclosed gas (112), an absorbing element (106) inside the sealed enclosure, the absorbing element configured to absorb the solar radiation transmitted via the glass plate, the absorbing element converting the solar radiation to thermal energy, the absorbing element in thermal contact with the enclosed gas, at least one circulation pipe (120) thermally coupled to the absorbing element, internal insulation (107) configured on a side of the circulation pipes opposite the transparent insulation, at least one variable portion (125) deployed in the sealed enclosure, and at least one channel (123) respectively connecting each variable portion to an environment outside the sealed enclosure, wherein the at least one variable portion is configured: to vary the volume of the variable portion in accordance with changing temperature of the enclosed gas such that in a first range of temperatures the variable portion restricts gas flow in the sealed enclosure and in a second range of temperatures the variable portion allows the internal gas circulation in the sealed enclosure. In an alternative embodiment, further including transparent insulation (104), the absorbing element further configured to absorb the solar radiation transmitted via the glass plate then via the transparent insulation.

[0010] In another alternative embodiment, the variable portion is reversibly expandable.

[0011] In another alternative embodiment, the environment outside the sealed enclosure is an ambient environment.

[0012] In another alternative embodiment, further including a front volume (124) associated with an area adjacent to the absorbing element, and a back volume (130) associated with an area on a side of the internal insulation opposite the glass plate,

[0013] In another alternative embodiment, the at least one variable portion (125) is deployed in the back volume.In another alternative embodiment, further including a heat sink module ( 134) thermally coupled to the back volume.

[0014] In another alternative embodiment, further including at least two ducts (127A, 127B) configured between the front volume and the back volume.

[0015] In another alternative embodiment, the at least two ducts (127A, 127B) are configured for convective gas flow between the front volume and the back volume, a first duct (127 A) of the at least two ducts configured at the top of the sealed enclosure, above the absorber, circulation pipes, and internal insulation, and a second duct (127B) of the at least two ducts configured at the bottom of the sealed enclosure, below the absorber, circulation pipes, and internal insulation. In another alternative embodiment, further including a back panel (129) on a side of the at least one variable portion opposite the internal insulation.

[0016] In another alternative embodiment, varying the volume of the variable portion in accordance with changing temperature of the enclosed gas starts at a predefined temperature and is over a given range of temperatures.

[0017] In another alternative embodiment, varying the volume of the variable portion starts at a predefined temperature and is over a predetermined temperature range.

[0018] In another alternative embodiment, the variable portion is further configured in an inflated state (125 A, 125C) when the temperature of the enclosed gas is relatively lower, to restrict gas flow in the sealed enclosure, and in a deflated state (125B, 125D) when the temperature of the enclosed gas is relatively higher, to allow gas flow in the sealed enclosure facilitating heat dissipation from the enclosed gas via a back panel to the ambient environment outside the sealed enclosure. In another alternative embodiment, further including at least two ducts (127A, 127B) wherein the variable portion is further configured in the inflated state (125 A, 125C) the volume of the variable portion is relatively larger restricting the convective gas flow via the ducts, and in the deflated state (125B, 125D) the volume of the variable portion is relatively smaller allowing the convective gas flow via the ducts.

[0019] According to the teachings of the present embodiment there is provided an apparatus for selfregulating thermal overheat protection including an enclosure (305) including an enclosed gas, afront volume (124) and a back volume (130), a heat module (310) configured in the front volume, a heat sink module (334) thermally coupled to the back volume, at least one duct (127C) fluidly connecting the front volume and the back volume, and at least one variable portion (125E, 125F) deployed in the back volume, the variable portion configured to vary the volume of the variable portion in accordance with changing temperature of the enclosed gas such that in a first range of temperatures the variable portion restricts gas flow in the sealed enclosure and in a second range of temperatures the variable portion allows the internal gas circulation in the enclosure.

[0020] In an alternative embodiment, the enclosure is selected from the group consisting of: a sealed enclosure, a solar collector, and an insulated solar collector.

[0021] In another alternative embodiment, internal insulation is configured inside the enclosure to provide the front volume (124) and the back volume (130).

[0022] In another alternative embodiment, further including a glass 100 configured such that solar radiation is transmitted via the glass to the heat module.

[0023] In another alternative embodiment, further including transparent insulation (104) configured inside the enclosure such that solar radiation is transmitted via the glass then via the transparent insulation to the heat module.

[0024] In another alternative embodiment, the variable portion is reversibly expandable.

[0025] In another alternative embodiment, the heat module is selected from the group consisting of: a passive heater, and a solar thermal radiation absorber.

[0026] In another alternative embodiment, the heat sink is thermally coupled to an environment outside the enclosure.

[0027] In another alternative embodiment, including a back panel 129 configured as a side of the enclosure thermally coupled to an environment outside the enclosure.

[0028] In another alternative embodiment, the at least one duct includes two ducts, a first duct (127A) of the at least two ducts configured at a top of the enclosure, above the heat module, and a second duct (127B) of the at least two ducts configured at a bottom of the enclosure, below the heat module.In another alternative embodiment, further including an actuator module (314) fluidly connecting the variable portion (125E) to an environment outside the enclosure.

[0029] In another alternative embodiment, the actuator module is a passive channel 123.

[0030] BRIEF DESCRIPTION OF FIGURES

[0031] The embodiment is herein described, by way of example only, with reference to the accompanying drawings, wherein:

[0032] FIG. 1 , a diagram of a typical solar collecting system.

[0033] FIG. 2, a plot of collector efficiency as a function of temperature and solar irradiance.

[0034] FIG. 3, a diagram of a cross-section view of a conventional solar thermal panel.

[0035] FIG. 4, a diagram of an insulated solar panel.

[0036] FIG. 5A, a diagram of a self-regulating solar energy module restricting gas flow.

[0037] FIG. 5B, a diagram of a self-regulating solar energy module allowing gas flow.

[0038] FIG. 6A, a diagram of a self-regulating solar energy module restricting gas flow with an alternative variable portion.

[0039] FIG. 6B, a diagram of a self-regulating solar energy module allowing gas flow with an alternative variable portion.

[0040] FIG. 7 A, a diagram of a self-regulating passive thermal overheat protection system restricting gas flow.

[0041] FIG. 7B, a diagram of a self-regulating passive thermal overheat protection system allowing gas flow.

[0042] DETAIEED DESCRIPTION

[0043] The principles and operation of the system according to a present embodiment may be better understood with reference to the drawings and the accompanying description. A present invention is a system for overheat protection for a solar thermal collector. The system relates to solar thermal energy systems. The system facilitates self-regulation of a solar thermal collector, optimizing temperature through automatic gas flow control, passive operation, enhancingefficiency while protecting the system from overheating. Internal variable portions are configured to adjust their volume based on the temperature inside the sealed thermal collector, thereby controlling the convective gas flow within the collector. A problem to be solved is how to maximize efficiency of solar energy conversion while managing temperature of the solar collector, and preventing overheating which may lead to degradation and / or damage to components and operation of the solar collector. Embodiments of this description may provide solution to one or more of these problems.

[0044] The invention of insulated solar panels provides a solar thermal collector with much greater energy conversion efficiencies, as compared to conventional solar thermal collectors. An insulated solar panel (solar thermal panel) is a solar thermal collector with, for example, a layer of transparent insulation material for the surface of the collection panel. Greater efficiencies in insulated solar panels, while providing greater benefits than conventional solar panels, also create operational and maintenance challenges that must be addressed for successful operation. Refer now to the drawings, FIG. 4, a diagram of an insulated solar panel 203. Transparent insulation 104 has been integrated into a conventional solar panel (FIG. 3) between an interior surface of the collection panel (glass 100) and the absorber 106. EIGHT is transmitted (passes) through the transparent insulation 104 to reach the absorber 106. In this case “insulated” refers to the transparent insulation 104 material behind the surface of the collection panel - inside the solar panel, between the glass 100 and absorber 106, as opposed to the conventional insulation typically used in the back and sides of a solar thermal collector (105, 108). Insulated solar panels are available from TIGI of Petah Tikva, Israel. Thermally insulating panels transmissive to solar radiation, while having low transmissivity to thermal infra-red radiation, have been disclosed in US 4,480,632, US 4,719,902, US 4,815,442, US 4,928,665, and US 5,167,217 all to Klier and Novik.

[0045] Greater energy conversion efficiencies are enabled particularly under conditions of substantial temperature differentials between the ambient temperature (for example in cold, high latitudes in winter) and the temperature of the circulating fluid (for example, heated water) inside the collector (for example, inside the circulation pipes 120). The transparent insulation 104 may be a honeycomb structure made of synthetic material or glass which is transparent to solar infrared(IR) radiation and visible wavelength light, while being partially opaque to thermal IR back-radiation, as a result of the optical properties of the material and the geometry of the material and / or the panel. In one implementation, the transparent insulation 104 is chosen to be substantially transparent to thermal IR back-radiation for reasons that will become clear below. At the same time, the transparent insulation material 104 is a thermal convection suppressor as a result of the geometry and physical characteristics of the material, and a thermal conduction suppressor as a result of the thermal properties of the material, including for example, thin walls of a honeycomb. The panel may be filled with a gas.

[0046] This imbalance of the transparency to incoming solar radiation versus the thermal IR back-radiation and the restricted energy losses due to low convection and conduction create a thermal diode and enables the capturing of heat and use of that captured heat for a variety of energy applications. The use of thermal insulation panels enables much greater energy conversion efficiencies over a much broader range of ambient temperatures and conditions, especially in colder climates as compared to systems that do not use a thermal insulation panel. In certain implementations, the solar absorption surface is coated with a spectrally selective layer that suppresses thermal re-emission in a particular band of the thermal infrared spectrum, obviating the need for the transparent insulation to be substantially opaque in the thermal infrared spectrum.

[0047] Refer to FIG. 2, a plot of collector efficiency as a function of temperature and solar irradiance. H = collector efficiency, X= AT / G, where AT is the temperature difference between ambient and the average collector temperature and G is the global solar radiation. Higher values of X indicate colder and less sunny conditions. As can be seen from the current figure, the insulated efficiency 250 of an insulated solar panel remains high as the environment gets colder and / or the amount of available solar radiation decreases, as compared to the conventional efficiency 252 of a conventional flat panel collector. When the efficiency of a typical conventional flat panel collector drops to about zero (for example, in the range of 0 to 10%), an insulated solar panel can still operate at an efficiency of about 40%.

[0048] In the context of this document, a variable portion 125 may be “reversibly expandable”. The variable portion 125 may be expansile, capable of expanding and then returning to its original size. The variable portion 125 may be compliant, capable of yielding to pressure and thenreturning to its original shape. For example, the variable portion may begin by being filled / expanded when the temperature inside the sealed enclosure is sufficiently close to the ambient temperature outside the sealed enclosure. When the temperature inside the sealed enclosure increases, the temperature of the enclosed gas correspondingly increases, and the pressure inside the sealed enclosure correspondingly increases. The increasing pressure on the variable portion causes the variable portion to deflate, or compress, (also referred to in the context of this document as the “unfilled” state), with a corresponding decrease in volume of the variable portion. When the temperature inside the sealed enclosure decreases, the temperature of the enclosed gas correspondingly decreases, and the pressure inside the sealed enclosure correspondingly decreases. The decreasing pressure on the variable portion causes the variable portion to inflate, or decompress (also referred to in the context of this document as the “filled” state), with a corresponding increase in volume of the variable portion. In the context of this document, the variable portion is also referred to as an “airbag”.

[0049] In the context of this document, convective flow involves the actual movement of matter, in this case typically a fluid (like air, gas, or water). Convective gas flow includes the transfer of heat caused by the bulk movement of a fluid, such as a gas. As the gas heats up, the gas expands, becomes less dense, and rises, while cooler, denser gas sinks. This creates a "loop", current, or (gas) circulation.

[0050] In the context of this document, movement of a fluid, for example the internal gas, is referred to as “gas flow”. In the case where the fluid is air, then the gas flow is airflow.

[0051] Refer to FIG. 5A, a diagram of a self-regulating solar energy module restricting gas flow. The solar energy module 205 includes elements similar to FIG. 4. The sealed enclosure 110 may be formed, for example, by the frame 102, glass 100, and back panel 129. In an alternative example, the sealed enclosure 110 may be the internal area including the front volume 124 and back volume 130 surrounded by the transparent insulation 104, lateral insulation 105, and the back panel 129. The transparent insulation 104 is typically internal to the sealed enclosure 110. The sealed enclosure 110 may have a fixed volume. The sealed enclosure 110 may have an enclosed gas 112. The sealed enclosure 110 may include an absorbing element 106 (also referred to in the context of this document as an “absorber”). The absorbing element 106 isconfigured to absorb the solar radiation (LIGHT) transmitted via the glass plate 100 then via the transparent insulation 104. The absorbing element 106 converts the solar radiation to thermal energy. The absorbing element 106 is in thermal contact with the enclosed gas 112. At least one circulation pipe 120 may be thermally coupled to the absorbing element 106. An internal insulation 107 may be configured on a side of the circulation pipes 120 opposite the transparent insulation 104.

[0052] At least one reversibly expandable variable portion 125 may be deployed in the sealed enclosure. The reversibly expandable portions 125 may be constructed from materials such as aluminum with polymer layers, such as polyethylene. One source of expandable bags is China Synergy Manufacturing Group (Fujian, China). The variable portions 125 may be configured on a support 136. For example, the support may be a netting associated with the back volume 129 adjacent to the internal insulation 107.

[0053] At least one channel 123 may respectively connect each variable portion 125 to an environment 114 outside the sealed enclosure 110. In a case where the channels 123 connect the internal variable portions 125 to the ambient environment 114, the channels 123 allow pressure equalization of the variable portions 125 with the external atmosphere 114.

[0054] Each of the at least one variable portions 125 may be configured to vary the volume of the variable portion 125 in accordance with changing temperature of the enclosed gas 112 such that in a first range of temperatures the variable portion 125 restricts gas flow in the sealed enclosure 110 and in a second range of temperatures the variable portion 125 allows the internal gas 112 circulation 132 (132A, 132B, 132C, 132D) in the sealed enclosure 110.

[0055] The environment 114 outside the sealed enclosure 110 may be an ambient environment.

[0056] The sealed enclosure 110 of the solar energy module 205 may include a front volume 124 associated with an area between the absorbing element 106 and the transparent insulation 104. The front volume 124 may be associated with an area adjacent to the absorbing element 106 and the transparent insulation 104. In a case where the circulation pipes 120 are configured between the absorbing element 106 and the transparent insulation 104, the front volume 124 may be associated with an area adjacent to the circulation pipes 120. A back volume 130 is associated with an area on a side of the internal insulation 107 opposite the transparent insulation 104. Atleast one of the reversibly expandable variable portions 125 may be deployed in the back volume 130.

[0057] Optionally, the solar energy module 205 may include a heat sink module 134 thermally coupled to the back volume 130. The heat sink module 134 may be passive or active, and may facilitate additional removal of thermal energy (heat) from the sealed enclosure 110. The heat sink module 134 may include one or more modules and / or sub-modules thermally coupled to one or more portions of the back panel 129 or the entire back panel 129.

[0058] The solar module 205 may include one or more ducts 127 fluidly configured between the front volume 124 and the back volume 130. The sealed enclosure 110 may include two ducts (127A, 127B), each duct connected between the front volume 124 and the back volume 130. A first duct 127 A of the ducts may be at the top 143 of the sealed enclosure 110 above the absorber 106, circulation pipes 120, and internal insulation 107. A second duct 127B of the ducts may be at the bottom 142 of the sealed enclosure 110 below the absorber 106, circulation pipes 120, and internal insulation 107. The at least two ducts 127 may be configured for convective gas flow between the front volume 124 and the back volume 130.

[0059] The solar module 205 may include a back panel 129 on a side of the variable portion 125 opposite the internal insulation 107.

[0060] Varying the volume of the variable portion 125 may be in accordance with changing temperature of the enclosed gas 112, the varying starting at a predefined temperature and being over a given range of temperatures. Varying the volume of the variable portion 125 may start at a predefined temperature and be over a predetermined temperature range. The volume inside the variable portion 125 varies with temperature due to the pressure of the enclosed gas 112, so as the temperature increases inside the sealed enclosure 110, the pressure increases inside the sealed enclosure 110, the volume decreases inside the variable portion 125, and correspondingly gas circulation (132 A, 132B, 132C, 132D) increases in the sealed enclosure. A feature of embodiments is that gas circulation may be passive.

[0061] The variable portion 125 is further configured in an inflated state (125A, 125C) when the temperature of the enclosed gas is relatively lower, to restrict gas flow in the sealed enclosure 110, and in a deflated state (125B, 125D) when the temperature of the enclosed gas is relatively higher, to allow gas flow in the sealed enclosure 110 facilitating heat dissipation from theenclosed gas via a back panel 129 to the ambient environment 114 outside the sealed enclosure 110.

[0062] The solar module 205 may include at least two ducts (127A, 127B) configured between the front volume 124 and the back volume 130 and the variable portion 125 is further configured in the inflated state (125 A, 125C) the volume of the variable portion 125 is relatively larger, restricting the convective gas flow via the ducts 127, and in the deflated state (125B, 125D) the volume of the variable portion 125 is relatively smaller allowing the convective gas flow via the ducts 127. Refer also to FIG. 5B, a diagram of a self-regulating solar energy module allowing gas flow. Gas circulation is shown in the figures by arrow 132A being heated gas (enclosed gas 112) rising (flowing up) in the front volume 124 from the bottom 142 to the top 143 of the sealed enclosure 110. The heated gas reaches the top 143 of the sealed enclosure 110 and flows, as shown by arrow 132B, from the front volume 124 toward the back volume 130. The heated gas may cool, at least in part, by releasing heat via the back panel 129 to the environment 114. The relatively cooler gas sinks (flows down) as shown by arrow 132C. As the gas flows 132C in thermal contact with the back panel 129, additional heat is released and the gas additionally cools. The cooler gas reaches the bottom 142 of the sealed enclosure 110 and flows, as shown by arrow 132D, from the back volume 130 to the front volume 124.

[0063] The absorbing element 106 may be in a spaced relationship to the transparent insulation 104 and / or the glass 100 such that a conduit is defined via the front volume 124 between the absorbing element 106 and the transparent insulation 104, or the absorbing element 106 and the glass 100. The absorbing element 106 and / or the internal insulation 107 may be in a spaced relationship to the back panel 129 such that a conduit is defined via the back volume 130 between the absorbing element 106 and / or the internal insulation 107 and the back panel 129. Restricting gas flow may include preventing and / or impeding a portion, some, or substantially all of the enclosed gas 112 from circulating in the sealed enclosure 110. In particular, restricting gas from the front volume 124 flowing to the back volume 130. Restricting may include reducing gas flow below a given and / or determined (pre-determined) amount. For example, the variable portion 125 may not completely seal the ducts 127 and there may be some relatively small amount of gas circulation even at temperatures below the predefined temperature (the temperature at which the variable portion 125 begins to deflate). However this relatively smallamount of gas circulation may be acceptable for a desired level of operation of the solar thermal panel 205.

[0064] Below the pre-determined temperature, the variable portions 125 remain inflated to restrict gas flow. This restriction may include, at least in part, the inflated variable portion 125 blocking one or more of the ducts 127. For example, see FIG. 5A where the variable portion (airbag 125A) blocks the first duct 127A. Also shown is another variable portion 125A on the right side of the figure, blocking the second duct 127B.

[0065] Refer also to FIG. 6A, a diagram of a self-regulating solar energy module restricting gas flow with an alternative variable portion, and FIG. 6B, a diagram of a self-regulating solar energy module allowing gas flow with an alternative variable portion. In the current exemplary figures, similar in operation to FIG. 5A and FIG. 5B, the variable portion (airbag 125C) inflates to block the area between the internal insulation 107 and the back panel 129, thus sealing substantially the entire cross-section of the back volume 130, hence restricting gas flow in the back volume 130. The ducts 127 may provide inlets and outlets for gas circulation. For example, the first duct 127a may provide an inlet for heated gas to flow from the conduit of the front volume 124 to the conduit of the back volume 130. Correspondingly, the second duct 127b may provide an outlet for the cooled gas to flow from the conduit of the back volume 130 to the conduit of the front volume 124.

[0066] Above the pre-determined temperature the volume of the variable portion 125 may vary in accordance with changing temperature of the enclosed gas 112. The deflation varying may start at the predefined temperature and as the temperature increases over a given range of temperatures (a predetermined temperature range) the corresponding pressure increases, and the variable portions 125 compresses to allow increasing gas flow, facilitating heat dissipation and preventing overheating. As the temperature decreases, this process is reversed, the variable portion 125 inflation varying as the temperature decreases over a range of temperatures, the corresponding pressure internal to the sealed enclosure 110 decreasing, and the variable portion 125 inflating to restrict gas flow, facilitating retaining heat (conserving heat) within the sealed enclosure 110 which can be transferred to the circulation pipes 120.

[0067] In a non-limiting example, when the absorber plate 106 is relatively cool or at nominal operating temperatures, for example 0- 70 degrees Celsius, the variable portion (125 A, 125C) in the backvolume 130 remains inflated to the extent that the inflated variable portion restricts gas flow between the front volume 124 and the back volume 130. As the variable portion 125 is connected to the outside ambient environment 114 by a channel 123 which allows free or impeded gas flow between the variable portion 125 and the ambient environment 114, retaining the pressure inside the variable portion 125 substantially at atmospheric pressure. For relatively higher operating temperatures, for example 80 - 200 degrees Celsius, the pressure rise in the front volume 124 of the collector 205 is such that the variable portion (125B, 125D) is compressed allowing convective gas flow between the front volume 124 and the back volume 130 of the collector 205. It is appreciated that the transition from thermally insulated to thermally conductive between the front volume 124 and back volume 130 of the collector 205 is not necessarily abrupt at a specific (predefined) temperature but the transition may occur over, for example, a 10 to 20 degree Celsius range. In another non-limiting example, varying the volume of the variable portion 125 may start at a predefined temperature of about 80 degrees Celsius, and the varying is over a predetermined temperature range of 80 to 120 degrees Celsius.

[0068] Refer now to FIG. 7A, a diagram of a self-regulating passive thermal overheat protection system restricting gas flow, and FIG. 7B, a diagram of a self-regulating passive thermal overheat protection system allowing gas flow. Elements of the current figure are similar to same-numbered elements of other figures in this description. An apparatus for self-regulating thermal overheat protection includes an enclosure 305 including an enclosed gas 112, a front volume 124 and a back volume 130. A heat module 310 is configured in the front volume 124. A heat sink module 334 is thermally coupled to the back volume 130. At least one duct 127 fluidly connects the front volume 124 and the back volume 130. At least one reversibly expandable variable portion (125E, 125F) is deployed in the back volume 130, the variable portion 125E is configured to vary the volume of the variable portion 125E in accordance with changing temperature of the enclosed gas 112 such that in a first range of temperatures the variable portion restricts gas flow in the enclosure 305 and in a second range of temperatures the variable portion 125F allows the internal gas circulation in the enclosure.

[0069] The enclosure 305 may be a sealed enclosure, a solar collector, or an insulated solar collector.The enclosure 305 may include internal insulation 107 configured inside the enclosure 305 to provide a front volume 124 and a back volume 130, the back volume 130 on a side of the internal insulation 107 opposite the front volume 124,

[0070] The enclosure 305 may include transparent insulation 104.

[0071] The heat module 310 may be a passive heater or a solar thermal radiation absorber 106.

[0072] The heat sink module 334 may be thermally coupled to an environment 114 outside the enclosure 305. The heat sink module 334 include a back panel 129.

[0073] The enclosure 305 may include at least one duct 127C. The enclosure 305 may include at least two ducts 127, a first duct of the ducts may be at the top 143 of the enclosure 305 above the heat module 310 and internal insulation 107. A second duct of the ducts may be at the bottom 142 of the enclosure 305 below the heat module 310 and internal insulation 107. The at least two ducts 127 may be configured for convective gas flow between the front volume 124 and the back volume 130.

[0074] An actuator module 314 fluidly connects to the variable portion. The actuator module 314 can be passive, for example like the channel 123 to the environment exterior to the enclosure 305.

[0075] Note that the above-described examples, numbers used, and exemplary calculations are to assist in the description of this embodiment. Inadvertent typographical errors, mathematical errors, and / or the use of simplified calculations do not detract from the utility and basic advantages of the invention.

[0076] To the extent that the appended claims have been drafted without multiple dependencies, this has been done only to accommodate formal requirements in jurisdictions that do not allow such multiple dependencies. Note that all possible combinations of features that would be implied by rendering the claims multiply dependent are explicitly envisaged and should be considered part of the invention.

[0077] It will be appreciated that the above descriptions are intended only to serve as examples, and that many other embodiments are possible within the scope of the present invention as defined in the appended claims.

Claims

1. WHAT IS CLAIMED IS:

1. A self-regulating solar energy module (205) for converting solar radiation to thermal energy, the module comprising:a glass plate (100),a sealed enclosure (102+100+129) having an enclosed gas (112),an absorbing element (106) inside the sealed enclosure, the absorbing element configured to absorb the solar radiation transmitted via the glass plate, the absorbing element converting the solar radiation to thermal energy, the absorbing element in thermal contact with the enclosed gas,at least one circulation pipe (120) thermally coupled to the absorbing element, internal insulation (107) configured on a side of the circulation pipes opposite the transparent insulation,at least one variable portion (125) deployed in the sealed enclosure, andat least one channel (123) respectively connecting each variable portion to an environment outside the sealed enclosure,wherein the at least one variable portion is configured:to vary the volume of the variable portion in accordance with changing temperature of the enclosed gas such that in a first range of temperatures the variable portion restricts gas flow in the sealed enclosure and in a second range of temperatures the variable portion allows the internal gas circulation in the sealed enclosure.

2. The solar energy module of claim 1, further including transparent insulation (104), the absorbing element further configured to absorb the solar radiation transmitted via the glass plate then via the transparent insulation.

3. The solar energy module of claim 1, wherein the variable portion is reversibly expandable.

4. The solar energy module of claim 1 , wherein the environment outside the sealed enclosure is an ambient environment.

5. The solar energy module of claim 1, further including a front volume (124) associated with an area adjacent to the absorbing element, and a back volume (130) associated with an area on a side of the internal insulation opposite the glass plate,6. The solar energy module of claim 5, wherein the at least one variable portion (125) is deployed in the back volume.

7. The solar energy module of claim 5, further including a heat sink module (134) thermally coupled to the back volume.

8. The solar energy module of claim 5, further including at least two ducts (127A, 127B) configured between the front volume and the back volume.

9. The solar energy module of claim 8 wherein the at least two ducts (127A, 127B) are configured for convective gas flow between the front volume and the back volume, a first duct (127 A) of the at least two ducts configured at the top of the sealed enclosure, above the absorber, circulation pipes, and internal insulation, and a second duct (127B) of the at least two ducts configured at the bottom of the sealed enclosure, below the absorber, circulation pipes, and internal insulation.

10. The solar energy module of claim 1, further comprising a back panel (129) on a side of the at least one variable portion opposite the internal insulation.

11. The solar energy module of claim 1 , wherein varying the volume of the variable portion starts at a predefined temperature and is over a predetermined temperature range.

12. The solar energy module of claim 1, wherein the variable portion is further configured in an inflated state (125 A, 125C) when the temperature of the enclosed gas is relatively lower, to restrict gas flow in the sealed enclosure, and in a deflated state (125B, 125D) when the temperature of the enclosed gas is relatively higher, to allow gas flow in the sealed enclosure facilitating heat dissipation from the enclosed gas via a back panel to the ambient environment outside the sealed enclosure.

13. The solar energy module of claim 12, further comprising at least two ducts (127A, 127B), wherein the variable portion is further configured in the inflated state (125A, 125C) the volume of the variable portion is relatively larger restricting the convective gas flow via the ducts, and in the deflated state (125B, 125D) the volume of the variable portion is relatively smaller allowing the convective gas flow via the ducts.

14. A solar energy module (205) for converting solar radiation to thermal energy, the module comprising:a glass plate (100),a transparent insulation (104),a sealed enclosure (102+100+129) having an enclosed gas (112),an absorbing element (106) inside the sealed enclosure, the absorbing element configured to absorb the solar radiation transmitted via the glass plate then via the transparent insulation, the absorbing element in thermal contact with the enclosed gas,at least one circulation pipe (120) thermally coupled to the absorbing element, internal insulation (107) configured on a side of the circulation pipes opposite the transparent insulation,a front volume (124) associated with an area adjacent to the absorbing element and the transparent insulation,a back volume ( 130) associated with an area on a side of the internal insulation opposite the transparent insulation,at least one reversibly expandable variable portion (125) deployed in the back volume, at least one channel (123) respectively connecting each variable portion to an ambient environment outside the sealed enclosure,at least two ducts (127A, 127B) configured for convective gas flow between the front volume and the back volume,a back panel (129) on a side of the at least one variable portion opposite the internal insulation,wherein the at least one variable portion is configured:to vary the volume of the variable portion in accordance with changing temperature of the enclosed gas,the varying starting at a predefined temperature and being over a given range of temperatures, andin an inflated state (125 A, 125C) the temperature of the enclosed gas is relatively lower, the volume of the variable portion is relatively larger, and restricting the convective gas flow via the ducts, andin a deflated state (125B, 125D) the temperature of the enclosed gas is relatively higher, the volume of the variable portion is relatively smaller, allowing the convective gas flow via the ducts, and heat dissipation from the enclosed gas via the back panel to the ambient environment outside the sealed enclosure.

15. An apparatus for self-regulating thermal overheat protection comprising:an enclosure (305) including an enclosed gas, a front volume (124) and a back volume (130),a heat module (310) configured in the front volume,a heat sink module (334) thermally coupled to the back volume,at least one duct (127C) fluidly connecting the front volume and the back volume, and at least one variable portion (125E, 125F) deployed in the back volume, the variable portion configured to vary the volume of the variable portion in accordance with changing temperature of the enclosed gas such that in a first range of temperatures the variable portion restricts gas flow in the sealed enclosure and in a second range of temperatures the variable portion allows the internal gas circulation in the enclosure.

16. The apparatus of claim 15 wherein the enclosure is selected from the group consisting of:a sealed enclosure,a solar collector, andan insulated solar collector.

17. The apparatus of claim 15 wherein internal insulation is configured inside the enclosure to provide the front volume (124) and the back volume (130).

18. The apparatus of claim 15 further including a glass (100) configured such that solar radiation is transmitted via the glass to the heat module.

19. The apparatus of claim 18 further including transparent insulation (104) configured inside the enclosure such that solar radiation is transmitted via the glass then via the transparent insulation to the heat module.

20. The apparatus of claim 15 wherein the variable portion is reversibly expandable.

21. The apparatus of claim 15 wherein the heat module is selected from the group consisting of:a passive heater, anda solar thermal radiation absorber.

22. The apparatus of claim 15 wherein the heat sink is thermally coupled to an environment outside the enclosure.

23. The apparatus of claim 15 further including a back panel (129) configured as a side of the thermally coupled to an environment outside the enclosure.

24. The apparatus of claim 15 wherein the at least one duct includes two ducts, a first duct (127 A) of the at least two ducts configured at a top of the enclosure, above the heat module, and a second duct (127B) of the at least two ducts configured at a bottom of the enclosure, below the heat module.

25. The apparatus of claim 15 further including an actuator module (314) fluidly connecting the variable portion (125E) to an environment outside the enclosure.

26. The apparatus of claim 25 wherein the actuator module is a passive channel (123).

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