Insulated Solar Thermal System
A solar thermal system is provided. The system comprises a solar thermal collector, comprising: a solar absorber to convert incident sunlight into heat; a transparent insulating component positioned relative to the solar absorber to allow sunlight to pass through to the solar absorber, and to reduce heat losses from the solar absorbed; wherein the transparent insulating component comprises a nano-porous matrix; and a heat exchanger coupled to the solar thermal collector.
This application is a continuation-in-part of U.S. patent application Ser. No. 14/095,871, titled “Induced Flow Solar Thermal Collector and Method” filed on Dec. 3, 2013, the specification of which is hereby incorporated herein by reference.
FIELDEmbodiments of the invention relate to systems and methods to convert sunlight into heat, the transportation of the resulting heat, and the exploitation of the transported heat for some useful purpose.
BACKGROUNDSolar thermal systems are collections of components which, when integrated and configured in the appropriate fashion, can enable the collection of sunlight for conversion into heat, the transportation of the resulting heat to a point of use, and potential transfer of the heat to another medium. The transferred heat, or in some cases the original heat, can be exploited in a number of ways that are useful to human society and the many heat driven processes that support modern civilization.
SUMMARYAccording to one aspect of the invention, there is provided a solar thermal system incorporating a transparent insulating medium comprising a nano-porous matrix:
which allows sunlight to pass into the solar thermal system while reducing losses through the medium which occur via conduction and radiation by virtue of the properties of the transparent insulating medium;
the heat from which is subsequently exploited to provide a useful function.
According to one aspect of the invention, there is provided a solar thermal system incorporating a transparent insulating medium comprising a nano-porous matrix:
which allows sunlight to pass into the solar thermal system while reducing losses through the medium which occur via conduction and radiation by virtue of the way in which a heat transfer fluid interacts within the transparent insulating medium;
the heat from which is subsequently exploited to provide a useful function.
According to one aspect of the invention, there is provided a solar thermal system incorporating a transparent insulating medium comprising a nano-porous matrix:
which allows sunlight to pass into the solar thermal system while reducing losses through the medium which occur via conduction and radiation by virtue of the heat transfer fluid being a gas or combination of gasses;
the heat from which is subsequently exploited to provide a useful function.
According to one aspect of the invention, there is provided a solar thermal system incorporating a transparent insulating medium comprising a nano-porous matrix:
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- wherein the heat transfer fluid is transported through the system via thermally driven buoyancy forces;
- the heat from which is subsequently exploited to provide a useful function.
According to one aspect of the invention, there is provided a solar thermal system incorporating a transparent insulating medium comprising a nano-porous matrix:
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- wherein components of the system can be fluidically isolated via automatic valves which actuate if a breach occurs at some point in the system;
- the heat from which is subsequently exploited to provide a useful function.
Other aspects of the invention will be apparent from the detailed description below.
In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the invention. It will be apparent, however, to one skilled in the art that the invention can be practiced without these specific details.
Reference in this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. Moreover, various features are described which may be exhibited by some embodiments and not by others. Similarly, various requirements are described which may be requirements for some embodiments but not others.
In one embodiment, a solar thermal system is disclosed. The system includes a collector which harvests incident sunlight and converts into heat by raising the temperature of a heat transfer fluid, an insulated piping mechanism which transports the heated fluid to a point of use, and a heat exchanger which transfers the heat from the heat transfer fluid to another heat transfer fluid or to the medium to be heated so that the heat can be exploited. In general the system is nominally airtight and under neutral or slightly positive pressure in order to minimize the inclusion of water vapor or other contaminants which may be present in the external environment.
The material comprising the nano-porous medium 108 may be in the form of an aerogel or aerogel like material made from a metallic oxide or other organic or inorganic materials whose fundamental structure consists of open or closed cellular pores whose diameter may range from tens of nanometers to tens of microns or more. The porous structure is such that it impedes the flow of a gas or gasses through the medium and therefore impedes the loss of heat from the solar thermal system. Other materials with similar properties including but not limited to masses of woven organic or inorganic fibers may be utilized and/or incorporated as well as long as some combination of the requisite transparency (i.e. transparent to the solar spectrum and absorbing and/or reflective for wavelengths longer than the solar spectrum) porosity and thermally insulating characteristics (i.e. less than 0.04 W/m K) can be achieved with the resulting medium. In this way heat losses 112 from the solar absorber 110 are mitigated thereby improving the efficiency of the solar thermal system.
During operation a cold heat transfer fluid is pumped via interconnect path 120 into collector 102 where it comes into contact with the solar absorber 110. The heat transfer fluid is nominally a gas or some combination of gasses, such as air, which have been selected due to their low-cost, their positive characteristics with respect to specific heat and thermal conductivity, and their benign nature from the standpoint of chemical reactivity and human health. In the embodiment shown, heat transfer fluid (introduced via the interconnect path 120 as described above) does not flow through the nano-porous medium 108 and only flows along a first fluid flow path 122 that exists only between the medium 108 and the absorber 110 and or within the absorber 110 as it gathers heat before exiting the collector 102.
The heated fluid leaves collector 102 via a second fluid flow path defined by inter-connect path 116 wherein it enters heat exchanger 118. Inter-connect paths 116 and 120 are airtight conduits which are insulated in some fashion to minimize heat losses to the environment. In one embodiment they comprise rolled sheets of galvanized steel which have been assembled and mounted to form a coaxial tube. In the annular space within the coaxial assembly resides an insulating material such as mineral wool, aerogel, or other material which is available and known by those skilled in the art. Heat exchanger 118 serves to transfer heat from the heat transfer fluid to a point of use. The phrase “point of use” is used to define the location wherein the heat begins to serve a useful function for example heat exchanger 118 may transfer the heat to water which is subsequently used for bathing or to an ammonia/water mixture which is subsequently used to drive an absorption chiller. After passing through heat exchanger 118, the heat transfer fluid returns to the collector.
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Advection is difficult to realize in fluids that are heated in a non-uniform fashion. This is due to a number of factors but is driven in large part by the fact that non-uniform temperatures in the fluid will lead to the generation of convection cells. Convection cells are phenomena that result when differences in fluid temperature, which produce differences in fluid density, produce currents within the fluid which are rising and/or falling as a result of the differences in density. If the fluid is unconstrained in any way then forcing the fluid in the direction of a heat source, in an attempt to mitigate heat flow away from the source, is very difficult because convection cells prevent uniform flow.
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In one embodiment function 134 may comprise the heating of water for residential or commercial use ranging from personal bathing and washing of clothes to the sterilization of containers or other items used in industrial processes.
In one embodiment function 134 may provide heat to heat the air within a residence or commercial space (space heating) in order to provide for a suitably comfortable environment for people who might occupy the space or items which are being stored there and which must be maintained at a certain minimum temperature. Greenhouses whose internal temperature must be maintained in cooler climates could benefit as well as any industrial processes that use air as a means to provide heat (clothes drying, fruit drying, baking, and cooking, etc.)
There are many refrigeration and cooling processes which utilize heat to drive their operation. In this case function 134 serves to ultimately provide a cooling resource that can be useful in maintaining the interior temperature of a residence or a commercial building. The cooling or refrigeration can also be used to maintain the temperature to keep certain perishable items from degrading which includes many kinds of foods, ice, medicines, etc. that must be kept chilled or frozen. Thermal cooling processes include but are not limited to adsorption, absorption, rankine driven compressors, and vapor ejection systems.
Most of the electricity produced in the world today is derived from a heat engine which drives an electrical generator. Function 134 could serve to ultimately provide electricity by coupling the heat to such a heat engine. There are many heat engines which could exploit this heat including steam and organic vapor driven rankine cycles based on turbines or pistons, stirling engines, among others.
Similarly function 134 could serve to provide mechanical power via one or more of the heat engine concepts described above. Mechanical power is of use in many situations which rely on rotational machinery ranging from fluid pumps for water and irrigation to vapor compressors for refrigeration and the transport of natural gas through pipelines.
Water distillation or the distillation of many fluids often relies on a source of heat to drive an evaporative process. Consequently function 134 could provide the basis to generate steam in a flash water distillation process for the desalination of water or perhaps heat for use in a whiskey distillery or hydrocarbon cracking process.
Any of the above mentioned applications may derive the bulk or a fraction of their required heat from another source, perhaps the combustion of a hydrocarbon for example, or a geothermal source. In such cases function 134 could provide a supplemental or primary source of heat that would work in conjunction with one or more additional sources to reduce the heat required from these sources.
Any of the above mentioned applications may derive the bulk or a fraction of their required heat from a thermal storage component. There are many techniques for storing heat which range from latent heat storage in a medium such as water or oil, to the heat of transformation which includes but is not limited to processes such as the reversible conversion of water into ice and the reversible conversion of a solid salt into a liquid, and the reversible adsorption of a liquid onto the surface of an desiccant. In such a situation function 134 may provide heat which may be stored directly or indirectly in a storage component. The term “indirectly” is meant to describe heat that is used to drive a conversion process, for example a freezer, which then freezes a medium, for example water, and thereby is able to indirectly store the heat in the form of ice. The indirectly stored heat may then be used by the application at a time or date where its utilization is optimized. Heat function 134 may also provide heat simultaneously to a storage mechanism and for immediate use in any of the above described classes of applications and functions.
Function 134 may incorporate one, all, or some combination of the applications and functions described above depending on the nature and complexity of the energy needs of the customer. A residence, for example, may require water and space heating throughout the year but only require space heating in the winter and space cooling in the summer. Because bathing generally occurs during the mornings or evening a thermal storage component may be required to store heat that is collected during the day to be utilized at those times.
Claims
1. A solar thermal system, comprising:
- a solar thermal collector, comprising a solar absorber to convert incident sunlight into heat; a transparent insulating component positioned relative to the solar absorber to allow sunlight to pass through to the solar absorber, and to reduce heat losses from the solar absorber; wherein the transparent insulating component comprises a nano-porous matrix; and
- a heat exchanger coupled to the solar thermal collector.
2. The solar thermal collector of claim 1, wherein the nano-porous matrix is defined by an aerogel.
3. The solar thermal collector of claim 1, further comprising:
- a first fluid flow path defined in the solar thermal collector for a heat transfer fluid to be introduced into the solar thermal collector for heating by the solar absorber; and
- a second fluid flow path defined in the solar thermal collector for removal of heated heat transfer fluid from the solar thermal collector; wherein the first fluid flow path comprises an advective flow path through the transparent insulating component whereby at least some of the heat transfer fluid entering the collector flows through the transparent insulating component en route for the solar heat absorber.
4. The solar thermal system of claim 3, wherein the first fluid flow path further comprises a non-advective flow path that is disposed between the transparent insulating component and the solar absorber.
5. The solar thermal system of claim 4, wherein a ratio of a volume of fluid flowing through the advective flow path to a volume of fluid flowing through the non-advective flow path is set to minimize heat losses from the solar collector through advection.
6. The solar thermal system of claim 5, wherein said ratio can be set dynamically during operation of the system.
7. The solar thermal system of claim 3, wherein the solar absorber is embedded in the transparent insulating component.
8. The solar thermal system of claim 1, wherein the heat transfer fluid is driven between the solar thermal collector and the heat exchanger by thermal buoyancy forces.
9. The solar thermal system of claim 1, further comprising at least one valve for fluid isolation of the solar thermal collector from the heat exchanger in cases where a structural integrity of the solar thermal collector is compromised.
10. The solar thermal system of claim 1, coupled to a heat function.
11. The solar thermal system of claim 10, wherein the heat function is selected from the group consisting of a heating function, a cooling function, an electricity generation function; mechanical power function and a heat storage function.
12. A solar thermal system, comprising:
- a solar thermal collector, comprising: a solar absorber to convert incident sunlight into heat; a transparent insulating component positioned relative to the solar absorber to allow sunlight to pass through to the solar absorber, and to reduce heat losses from the solar absorber; a first fluid flow path defined in the solar thermal collector for a heat transfer fluid to be introduced into the solar thermal collector for heating by the solar absorber; said first fluid flow path comprising an advective flow path through the transparent insulating component whereby at least some of the heat transfer fluid entering the collector flows through the transparent insulating component en route for the solar heat absorber; and a second fluid flow path defined in the solar thermal collector for removal of heated heat transfer fluid from the solar thermal collector; and
- a heat exchanger coupled to the solar thermal collector.
13. The solar thermal system of claim 12, wherein the transparent insulating component comprises a nano-porous matrix.
14. The solar thermal system of claim 13, wherein the nano-porous matrix is defined by an aerogel.
15. The solar thermal system of claim 14, wherein the first fluid flow path further comprises a non-advective flow path that is disposed between the transparent insulating component and the solar absorber.
16. The solar thermal system of claim 15, wherein a ratio of a volume of fluid flowing through the advective flow path to a volume of fluid flowing through the non-advective flow path is set to minimize heat losses from the solar collector through advection.
17. The solar thermal system of claim 16, wherein said ratio can be set dynamically during operation of the system.
18. The solar thermal system of claim 12, wherein the solar absorber is embedded in the transparent insulating component.
19. The solar thermal system of claim 12, coupled to a heat function selected from the group consisting of a heating function, a cooling function, an electricity generation function; mechanical power function and a heat storage function.
20. The solar thermal system of claim 12, wherein the heat transfer fluid is driven between the solar thermal collector and the heat exchanger by thermal buoyancy forces.
Type: Application
Filed: May 30, 2014
Publication Date: Jun 4, 2015
Inventor: Mark W. Miles (Atlanta, GA)
Application Number: 14/292,702