WO2007141431A2

WO2007141431A2 - Multilayer thermal energy collecting device for photon converter of atmospheric and solar radiation

Info

Publication number: WO2007141431A2
Application number: PCT/FR2007/000964
Authority: WO
Inventors: Pascal Fayet; Yasmina Fayet
Original assignee: Pascal Fayet; Yasmina Fayet
Priority date: 2006-06-09
Filing date: 2007-06-11
Publication date: 2007-12-13
Also published as: WO2007141431A3; FR2902182A1

Abstract

The invention concerns a multilayer thermal energy collecting device comprising at least one heat exchanger (3), a composite latent heat storage layer (2) and a photovoltaic or photothermal converter (1). The invention is mainly characterized in that it uses the technique of management of radiative cooling via infrared radiation on space and atmosphere applied to the photothermal conversion of atmospheric and solar radiation and to the photovoltaic conversion of solar radiation, in particular in a clear and dry atmosphere having high clearness and low emissivity in the band of photonic wavelengths ranging between 8μm and 13μm.

Description

The present invention relates to multilayer thermal energy collecting devices used to supply the heat source of a heat exchanger and / or to improve the electrical power supplied by a photovoltaic generator (PV). It relates particularly to such devices which operate with a heat reserve and which comprise at least one heat exchanger and a photonic converter using one or more radiative processes among the heat production by absorption of solar radiation, the electricity production by photovoltaic conversion. solar radiation and radiative cooling by infrared radiation (IR) on space.

For the purposes of the present invention and the claims relating thereto, the following terms are defined as follows:

The term "infrared radiation" means photon radiation having a wavelength greater than 0.8 μm.

The expression "visible radiation" means photonic radiation having a wavelength of between 0.4 μm and 0.8 μm.

The term "solar radiation" means radiation from the sun and including the visible. The term "atmospheric radiation" means radiation from the sky including infrared radiation.

The term "atmospheric window" means atmospheric radiation band corresponding to infrared wavelengths between 8 μm and 13 μm. The atmospheric emissivity in this band varies in particular as a function of the water content of the atmosphere and cloudiness.

The term "ambient air temperature" means the dry temperature of the ambient air recorded under ventilated shelter.

The expression "spectrally selective surface [8 μm-13 μm]" refers to an ideally radiating surface such as a black body in the wavelength band between 8 μm and 13 μm and reflecting the visible and infrared radiation outside this region. bandaged.

The expression "photothermal converter of the radiation of

"Atmosphere" means photothermal converter using radiative cooling by infrared radiation on space and atmosphere. The expression "photothermal converter of solar radiation" means photothermal converter using radiative heating by absorption of solar radiation in the wavelength band of visible radiation. The term "active converter operating temperature" refers to the temperature of the converter when it produces heat energy and feeds the heat source of a heat exchanger or the temperature of the converter when produces cooling energy and feeds the heat sink of a heat exchanger.

It is known to use infrared radiative cooling on the space to supply the heat sink of a heat exchanger in a device described in a patent such as U.S. 3,043,112 Method and means for producing refrigeration by selective radiation, July 10, 1962. This device comprises a photothermal converter of the radiation of the atmosphere consisting of a panel in close contact with a heat exchanger so as to optimize the heat transfer by transmission and whose spectrally selective active face in the "window atmospheric [8μm-13μm] "is separated from a blade of dry air and a film transparent to infrared radiation.

Reports from the Academy of Sciences, Paris such as CR. Acad. Sc. Paris, t.256, No. 9, February 25, 1963, 2013-2015 (F. TROMBE) or such as CR. Acad. Sc. Paris, t.258, June 8, 1964, 5685-5688 (F. TROMBE, M and Mrs LE PHAT VINH) describe experiments in similar devices on large temperature decreases exceeding 36 ° C below room temperature , obtained by the radiation of the black body on the space.

It is known that the performance of radiative cooling by infrared radiation on space is all the more important that the atmosphere has a high transparency in the "atmospheric window [8μm-13μm]". It is therefore customary to increase the performance of photonic converters using such a radiative cooling process, to implant these in the known dry regions to clear sky. Indeed, these regions benefit from an atmosphere with a high degree of transparency in the "atmospheric window [8 μm-13 μm]".

It is known that the transparency of the atmosphere in the "atmospheric window [8 μm-13 μm]" decreases as the zenith angle increases, while its emissivity approaches that of a black body. It is therefore customary, to optimize the radiative cooling by IR radiation on the space, to orient the active face of the converter as much as possible towards the zenith or to deflect the fraction of atmospheric radiation not coming from the zenith with a view to limit the heating of the converter by absorption of atmospheric radiation.

It is known to use photothermal converters of space and atmosphere radiation consisting of panels whose spectrally selective active surface radiates ideally as a black body in the "atmospheric window [8 μm-13 μm]" and ideally reflects the solar and infrared radiation outside this window to supply the cold source of a heat exchanger at a lower temperature than the ambient air. However, for small temperature decreases (generally between 0 ⁰ C and 10 ⁰ C below ambient temperature) the power radiated by a black body is greater than that radiated by a spectrally selective surface as described above. Consequently, this solution is not optimized for small temperature decreases, because in this case a blackbody offers a cooling capacity greater than that of a spectrally selective body in the "atmospheric window [8μm-13μm]".

It is known that multilayer devices exploiting radiative cooling are implemented according to two main embodiments.

The first embodiment relates to devices in which the heat flux absorbed by the converter is less than the heat flux that would emit the same converter to the ambient air temperature, in which case the temperature of the converter is less than 'ambiant air. In this embodiment, it is customary to cover the converter with a layer thermally insulating and transparent to IR radiation at least in the "atmospheric window [8μm-13μm]" in order to limit the convective and transmissive heat input on the converter while allowing the latter to be cooled by infrared radiation in the "atmospheric window" [8μm-13μm].

The second embodiment relates to multilayer devices in which the heat flux absorbed by the converter is greater than the heat flux that would emit the same converter at the ambient air temperature, in this case, the operating temperature of the converter. is higher than the ambient air temperature. In this embodiment, it is customary not to cover the transparent thermal insulation layer in order to promote cooling of the converter by convection and transmission with the ambient air.

Photothermal converters of atmospheric radiation have an operating temperature that depends not only on the transparency of the atmosphere in the "atmospheric window [8μm-13μm]", but also on its temperature. This has the effect of continuously varying the temperature of the converter because the temperature of the atmosphere varies continuously. Subsequently, the temperature of the cold source of the heat exchanger also varies, because the converter directly feeds the latter by thermal transmission. In addition, when the sky is overcast or the water content is high, the performances of the radiative cooling on the space decrease, because the emissivity of the atmosphere in the "atmospheric window [8 μm-13 μm]" increases when its content in water increases. In this case, the converter can no longer supply the heat sink of the heat exchanger with sufficient power.

It is known, for the air conditioning of indoor living or working spaces, located in the dry areas in clear skies, to use a device exploiting the nocturnal radiative cooling, the radiative heating by absorption of solar radiation and the storage in heat Sensitive as described in the publication Heating Experiments with Radiative Cooling System of the Scientific Periodical Building and Environment, Vol 31, No. 6, pp. 509-517. This device is particularly adapted to regions that are hot enough in summer to justify cooling air conditioning and cold enough in winter to justify heating air conditioning. It includes a selective surface that radiates as a black body in the solar spectrum and IR. This has the effect of heating the converter, day, by absorption of solar radiation and cool the converter at night, by IR radiation to space and atmosphere.

In the case of air-conditioning in heating, the heat reserve is heated by diurnal forced circulation in a heat exchanger in close contact with the converter to promote thermal exchange by transmission. It serves as a coolant to heat the space. It allows the smoothing of the temperature of the hot spring, and the feeding of the latter at night or when the sky is overcast.

In the case of cooling air conditioning, the thermal reserve is cooled by night forced circulation in a heat exchanger in close contact with the converter to promote heat exchange by transmission. It serves as coolant to cool the space. It allows the smoothing of the temperature of the cold source and the feeding of the latter during the day or when the sky is covered.

However, the sensible heat and the density of a liquid are such that it is used, to smooth the temperature of the latter and ensure the supply of the hot spring at night or when the sky is covered, or to ensure the feeding the cold source during the day or when the sky is overcast, to use necessarily large thermal capacities which also require a lot of energy for their brewing.

It is known to supply the heat source of a heat exchanger to use a multilayer device exploiting the radiative heating by absorption of solar radiation. This device comprises a heat exchanger and a photothermal converter of solar radiation consisting of a panel whose active face ideally reflects infrared radiation and has an emission factor that is close to that of a black body in the visible. The panel is oriented towards the sun to optimize the incident solar energy flow and thus promote the heating of the converter, because the effects of incident solar radiation cause a heating of the converter all the more important that the incident solar flux is large. This panel is in close contact with a heat exchanger to optimize the heat flow by transmission and thus ensure the supply of the heat source of the heat exchanger. The photothermal converters, keeping these spectral properties at temperatures such as 800 ⁰ K, are rare and expensive.

It is known that photothermal converters of solar radiation have an operating temperature which depends on the incident solar irradiance and the ambient air temperature. This has the effect of continuously varying the temperature of the converter, because the incident solar illumination, the ambient air temperature continuously vary. Subsequently the temperature of the heat source of the heat exchanger also varies because the converter is in close contact with the heat exchanger. In addition, at night or on cloudy days, the photothermal conversion performance of the solar radiation is respectively zero or very weak because the direct solar irradiance is zero at night and very low in overcast conditions. In this case, the converter can no longer supply the heat source of the heat exchanger with sufficient power.

To overcome these disadvantages, US Patent 2005/0061312 (Szymocha), March 24, 2005 discloses a multilayer device comprising a latent heat storage layer, a transparent layer, a photothermal converter of solar radiation separated from the transparent layer by a layer of 'air. This solution allows, thanks to the latent heat storage layer, the smoothing of the temperature of the hot source, and the supply of the latter, at night or when the sky is covered. In addition, the air layer makes it possible to isolate the device from heat losses by convection transmission with the ambient air. However, the thermal losses by infrared radiation on the space via the converter or the transparent layer remain very important, especially in a weakly emissive atmosphere or having a low radiation temperature.

In addition it is of interest to install these devices in clear and dry areas corresponding for example to the desert, semi desert or altitude to optimize the incident solar radiation and therefore the heating of the converter, because the solar field depends the water content and cloudiness of the atmosphere.

However, the increase of the solar field by the choice of the zone of implantation of these devices, is accompanied by a decrease of the emissivity of the atmosphere, particularly in the "atmospheric window [8μm-13μm]", because the emissivity of the atmosphere decreases when its water content or cloudiness increases and a decrease in the radiation temperature of the atmosphere especially at night, consecutively the heat losses by infrared radiation on the space and the atmosphere are more important, which counterbalances the choice of an establishment in an area where the solar field is very important.

It is known to increase the electrical power of a PV generator to use a device for protection against heating because the performance of a cell degrade when its operating temperature increases.

EP-A-1 162 659 (MERCK PATENT GMBH) 12 December 2001 describes a thermal reserve in latent heat of high thermal conductivity, used for the (de) storage of heat at constant temperature in the field of protection against heating of semiconductor devices such as PV cells. JP 11 108467 (NOMOTO SO) October 7, 1997 discloses a PV generator using a multilayer heat removal device comprising a convective type heat exchanger and a latent heat composite heat reserve.

PV panels are expensive and fragile, and the direct solar flux does not bring them to saturation with regard to photovoltaic conversion. It is therefore customary, to increase the electrical power of a photovoltaic panel of a given size, to concentrate the light solar on the active side of the cells that cover it. The effects of the solar flux coming from the concentrator are the same as those of the direct solar flux and therefore lead to an additional heating of the solar panel, the greater the higher the concentration and, consequently, a decrease in the photovoltaic efficiency, because the performances of a cell degrade when its operating temperature increases. This counterbalances the effect of using a concentrator. U.S. Patent No. 3,999,283 (DEAN ET AL), December 28, 1976, discloses a concentrator PV generator comprising a heat-removal device such as a convective cooling fin heat exchanger. US Patent 5,498,297 (O'NEILL et al.) Mar. 12, 1996, discloses a similar device in which the PV cell is encapsulated and attached to the cooling fin exchanger by a particularly strong, waterproof and transparent Tefzel adhesive film.

The solar deposit depends on the water content and cloudiness of the atmosphere. It is therefore preferable to install these devices in clear and dry areas corresponding for example to the desert, semi-desert or altitude zones to optimize the incident solar radiation and thus the production of electrical energy and / or heat of the converter, because the latter depends on the incident solar radiation.

In addition, the increase of the solar field by the choice of the implantation zone of these devices is accompanied by a reduction of the emissivity of the atmosphere because the emissivity of the latter decreases when its water content or its cloudiness increases. Consequently, it is harmful that these devices are not designed to optimize the diurnal cooling of the converter by infrared radiation on the space and the atmosphere when the device produces electrical energy and limit for example night heat losses. by infrared radiation on the atmosphere and space when the device also feeds the hot source of a heat exchanger at night.

To overcome these drawbacks, the present invention proposes a multilayer thermal energy collector device comprising at least one heat exchanger (3), a composite heat storage layer. latent material (2), consisting of expanded natural graphite (GNE) compressed and impregnated with a phase change material (PCM), and a photovoltaic or photothermal converter (1), characterized in that the device uses a technique for managing the radiative cooling by infrared radiation applied to the photothermal conversion of atmospheric, solar radiation and photovoltaic conversion of solar radiation in a clear and dry atmosphere with high transparency and low emissivity in the "atmospheric window [8μm-13μm]".

According to another characteristic, the device operates at a temperature close to the phase change temperature of the MCP and between 250 ⁰ K and 800 ⁰ K.

According to another characteristic, the device operates in a two-cycle cycle, a time of evacuation of heat by infrared radiation on the space and the atmosphere and / or convection - transmission with the ambient air, materialized by the solidification to constant MCP temperature, a time of absorption of heat by absorption of solar radiation, atmospheric and / or by convection - transmission with the ambient air, materialized by the constant temperature melting of the MCP.

According to another characteristic, the device comprises at least one additional layer constituting the active face (4) of the converter (1) radiating ideally as a black body in the "atmospheric window [8μm-13μm]" towards the zenith or in a zenith angle between 0 ° and 30 ° when used to supply the cold source of the heat exchanger (2) or to increase the electric power supplied by a PV generator.

According to another characteristic, the active face (4) of the converter (1) is a spectrally selective surface in the "atmospheric window [8μm-13μm]" when the device is used to feed the cold source of the heat exchanger if, for a given dimension and an identical active operating temperature of the converter (1), such an active face (4) radiates more energy than an active face (4) that radiates like a black body over the entire infrared spectrum and reflects the visible. By way of nonlimiting example, the converter is a metallic panel reflecting visible and infrared radiation such as a polished aluminum panel covered with a spectrally selective layer in the "atmospheric window [8 μm-13 μm]" such that a Silicon monoxide (SIO) coating in lμm thickness, such as a magnesium monoxide (MGO) coating with a thickness of 1.1 mm, such as a 0.54 mm thick layer of lithium fluoride (LiF) or such as a polyvinylfluoride film (PVF Tedlar) in thickness of 125 .mu.m. The publications of scientific periodicals Applied Optics, Vol.23, No.3, 370-372 (P. BERDAHL), February 1, 198; Thin Solid Film, 90 (1982) 187-190 (CG GRANQVIST, A. HJORTSBERG AND TS ERIKSSON); J. Appl. PHYs. 52 (6), June 1981, Radiative Cooling to Low Temperatures: General Consideration and Application to Selectively Emitting SIO films 190 (CG GRANQVIST, A. HJORTSBERG) describe techniques for implementing and optimizing the thickness of layers. thin on metal substrates to obtain a spectrally selective surface in the "atmospheric window [8μm-13μm]".

According to another characteristic, the active face (4) of the converter (1) radiates ideally as a black body over the entire infrared spectrum and reflects the visible to produce cold (3) if, for a given dimension and a temperature of identical active operation of the converter (1), such an active face (4) radiates more energy than an active face (4) which would be spectrally selective in the "atmospheric window [8μm-13μm]".

By way of nonlimiting example, the converter (1) is a metal panel reflecting visible and infrared radiation such as a polished aluminum panel covered with a highly emissive layer of infrared radiation such as a layer of alumina ( AL ₂ O ₃ ) in a thickness of 10 μm or 15 μm or a layer of white paint rich in titanium dioxide (TiO ₂ ).

According to another characteristic, the device comprises a concentrator layer of solar radiation transparent to visible radiation and to infrared radiation engraved in Fresnel step (7) disposed at above the converter to concentrate the incident solar radiation on the latter, the transparency of the concentrator layer (7) infrared radiation allowing the converter to radiate freely to the space by infrared radiation much of the heat induced by the absorption of solar radiation. In this case the converter (1) consists of one or more PV cells whose active face (4) is covered with a film transparent to solar radiation which radiates ideally as a black body in the infrared spectrum. By way of non-limiting example, the converter (1) is covered with a Dupont Teflon® FEP, Dupont Teflon® TPFE or Dupont Tefzel®T ^{2 film} in a thickness of 62 μm.

According to another feature, the device comprises an additional layer (5) of high thermal resistance covering the active face of the converter (1), transparent to infrared radiation in the "atmospheric window [8μm-13μm]" to reduce the heat input by transmission - convection with the outside air and favor the evacuation of heat by infrared radiation on the space and the atmosphere, when the active operating temperature of the converter is lower than the ambient air and when the device supplies the cold source of the heat exchanger. Such a layer (5) is constituted by way of non-limiting example of one or more blades of dry air with a thickness of 19 mm, separated by walls (10) of low density polyethylene in a thickness generally between 50 and 200μm or by chalcogenide glass walls, in this case to obtain lower temperatures and optimized the useful cold power, the dry air blade can be replaced by vacuum, excellent thermal insulation.

According to another characteristic, the device comprises an additional layer (5) of high thermal resistance covering the active face of the converter (1) reflecting the infrared radiation and transmitting the solar radiation to reduce the thermal losses by infrared radiation on space and space. and by convection-transmission with the outside air and allow the heating of the converter by absorption of solar radiation when the device supplies the hot source of the heat exchanger (3) at a temperature higher than the air ambient, consisting of one or more blades of dry air of thickness 19 mm or vacuum of the same thickness separated by walls (10) of glass transparent to solar radiation, one of these walls (10) at least , being covered by way of nonlimiting example of a TiO2 / Ag / TiO2 triple layer coating in which each of the layers has a thickness of 18 nm. Such multilayer walls and their associated manufacturing method are described in US Patent 4,822,120 (FAN ETAL) April 18, 1989.

According to another characteristic, the device comprises an additional layer of removable thermal insulation (8) made of a low thermal conductivity material covered on its outer face (12) with a film reflecting the visible and infrared radiation. This layer (8) is arranged on the device when the operating temperature of the converter (1) becomes greater than the phase change temperature of the MCP to reduce the heat input by absorption of the atmospheric and / or solar radiation and to reserve the most much of the latent heat of fusion of the MCP to the supply of the cold source of the heat exchanger (3) when the device supplies the cold source of the heat exchanger (3). The layer (8) is removed when a spectrally identical surface to the active face (4) of the converter (1) radiating under the same conditions as the converter (1) and in an identical device not comprising the thermal insulation layer removable (8) reaches a temperature lower than the phase change temperature of the MCP.

According to another characteristic, the device comprises an additional layer of removable thermal insulation (8) made of a low thermal conductivity material covered on its inner face (11) with a film reflecting the infrared radiation. This layer is disposed on the device when the operating temperature of the converter (1) becomes lower than the phase change temperature of the MCP to reduce thermal losses via the converter (1) by infrared radiation on the space and the atmosphere and reserving most of the latent heat of solidification of the MCP to the supply of the heat source of the heat exchanger (3) when the device feeds the hot source of the heat exchanger (3). The layer (8) is removed when a spectrally identical surface to the active face (4) of the converter (1) radiating under the same conditions as the converter (1) and in an identical device not comprising the removable insulation layer (8) reaches a temperature above the phase change temperature of the MCP.

According to another characteristic, the phase change temperature of the MCP is greater than the active operating temperature of the converter (1) to allow it to solidify when the device supplies the cold source of the heat exchanger (2).

According to another characteristic, the phase change temperature of the MCP is lower than the active operating temperature of the converter (1) to allow its melting when the device supplies the heat source of the heat exchanger (3).

According to another characteristic, the latent heat storage layer (2) is a composite of high thermal conductivity and high energy density placed in close contact with the converter (1) and the heat exchanger (3) to promote exchanges by heat transmission and in that its thermal resistance and its mass allow it to maintain the temperature of the converter (1) and the heat exchanger (3) at a level close to the phase change temperature of the MCP.

By way of nonlimiting example, the latent heat storage composite layer (2) is made with expanded natural graphite (GNE) compressed to 150 kg / m ³ and impregnated with a phase change material such as an alkane or a mixture of alkanes and has an energy density of the order of 150KJ / Kg and a thermal conductivity of the order of 25W / mK in a direction of space. The photonic converter (1) and the heat exchanger (3) are then positioned perpendicular to its axis of greater thermal conductivity to promote heat exchange by transmission. With regard to the other thermal capacities known in the art and of the same thermal conductivity, it has, in addition to greater density energy efficiency, a simpler implementation. These advantages, and in particular its high thermal conductivity associated with its high energy density and a wide range of choice of phase change materials, allow the implementation in a wide range of temperatures, simple fixed thermal storage systems, adaptable, efficient, and bulky compared to other sensitive or latent heat storage systems. EP-AI 162 659 (MERCK PATENT GMBH) 12 December 2001 and the publication of the scientific journal International Journal of Heath and Mass Transfer 44 (2001) 2727-2737 (X.PY) describe techniques for implementing the matrix. GNE at different compression rates impregnated with different types of MCP.

Other features and advantages of the invention will become clear in the following description given by way of non-limiting example with reference to the appended figures which represent according to the invention:

- Figure 1 is a view, a sectional view, of a multilayer thermal energy collector device used to supply the cold source of a finned tubular heat exchanger and forced water circulation in the case where the Active operating temperature of the converter is lower than the ambient air temperature.

FIG. 2, a view, under the same conditions, of a multilayer thermal energy collector device used: a) To non-simultaneously supply the cold source and the hot source of a finned tubular heat exchanger (b) Either to supply the cold source of a finned and forced-flow tubular heat exchanger in the case where the active operating temperature of the converter is greater than the temperature of the ambiant air. - Figure 3, a view in the same conditions of a multilayer thermal energy collector device used to supply the hot source of a finned tubular heat exchanger and forced water circulation.

FIG. 4, a view, under the same conditions, of a multilayer thermal energy collector device used to improve the electric power supplied by a PV generator and supplying the hot source of a finned tubular heat exchanger with forced water circulation.

The present invention therefore consists in arranging the latent heat storage composite layer (2) in close contact with the converter (1) and the heat exchanger (3) so as to promote thermal exchange by transmission. When the device is only used to supply the heat sink of a heat exchanger (3) and the active operating temperature of the converter (1) is greater than the ambient air temperature, a multilayer device such as represented in FIG. 1, comprising a photothermal converter of the radiation of the spectrally selective atmosphere in the "atmospheric window [8 μm-13 μm]" constituted by way of non-limiting example of a polished aluminum panel covered with a layer of silicon monoxide (SIO) in lμm thickness constituting the active face (4) of the converter (1). This has the effect of reducing the heat input by absorption of atmospheric and solar radiation and to promote the radiative cooling of the converter in the "atmospheric window [8μm-13μm]" below the ambient temperature.

Such a device further comprises two additional thermal insulation layers:

- The first (5) covers the converter (X). It is transparent to IR radiation at least in the "atmospheric window [8μm-13μm]".

It consists of two blades of dry air (9) with a thickness of 19 mm separated by walls of low density polyethylene 30μm thick (10) transparent to IR light.

- The second (6), located under the heat exchanger is made of a low thermal conductivity material such as extruded polystyrene 10cm thick covered on its outer face (13) of a film reflecting the visible radiation and infrared.

This has the effect of reducing the heat input to the device by convection, transmission with the ambient air while allowing the converter (1) to emit to the space in the "atmospheric window" [8μm-13μm], under a dry, clear atmosphere at a temperature below ambient air.

During the heat dissipation time corresponding to the clear, dry, and nocturnal periods, the active face of the converter (4) is oriented as much as possible towards the zenith to optimize the radiative cooling. The latter (4) is rapidly cooled by IR radiation on the space through the "atmospheric window [8 μm-13 μm]" to a temperature slightly lower than the phase change temperature of the MCP contained in the storage layer. latent heat (2). When this temperature is reached, the MCP solidifies at a constant temperature. At the same time, part of the cold induced by IR radiation on the space also supplies, via the latent heat storage layer (2) of low thermal resistance, the cold source of the heat exchanger (3). During the heat absorption time corresponding to the covered, wet, or diurnal periods, when the temperature of the converter becomes greater than the phase change temperature of the MCP, the device is covered with a removable thermal insulation layer (8) manufactured in a material of low thermal conductivity coated on its outer face (11) with a film reflecting the IR and solar radiation. This has the effect of limiting convection and transmission heat gains with the ambient air and absorption of solar radiation and / or atmospheric. Consecutively this allows to reserve a greater part of the heat absorption materialized by the melting of the latent heat storage layer (2) to the supply of the cold source of the heat exchanger (3).

In a variant, when the device is only used to supply the heat sink of a heat exchanger (3) and the active operating temperature of the converter (1) is greater than the ambient air temperature, it is generally used a multilayer device as shown in FIG. 2, comprising a photothermal converter (1) for the radiation of the atmosphere and of the space in direct contact with the ambient air, reflecting the visible radiation and radiating like a black body at least in the "atmospheric window [8μm-13μnn]" constituted by way of non-limiting example of a polished aluminum panel covered with a layer of alumina in a thickness of 10 μm constituting the active face (4) of the converter (1). This has the effect of reducing heat gains by absorption of solar radiation and to optimize the radiative cooling of the converter by infrared radiation on the atmosphere and on space. During the heat removal time, the active face of the converter (4) is oriented as much as possible towards the zenith to optimize the radiative cooling. The latter (4) cools rapidly to a temperature slightly below the phase change temperature of the MCP, by convection - convection with ambient air and by IR radiation on the atmosphere and space. When it reaches this temperature, the MCP solidifies at constant temperature. At the same time, a part of the cold induced by transmission - convection with the ambient air and IR radiation on the space and the atmosphere also feeds by transmission via the latent heat storage layer (2) of low thermal resistance, the cold source of the heat exchanger (3). During the heat absorption time corresponding to the covered, wet, or diurnal periods, when the temperature of the converter becomes greater than the phase change temperature of the MCP, the device is covered with a removable thermal insulation layer (8) manufactured in a material of low thermal conductivity coated on its outer face (11) with a film reflecting the IR and solar radiation. This has the effect of limiting convection and transmission heat gains with the ambient air and absorption of solar radiation and / or atmospheric. Consecutively this allows to reserve a greater part of the heat absorption materialized by the melting of the latent heat storage layer (2) to the supply of the cold source of the heat exchanger (3).

In addition, if the temperature of the ambient air becomes greater than the operating temperature of the heat exchanger, a removable thermal insulation layer (6) is put in place under the heat exchanger. It is made of a material of low thermal conductivity such as extruded polystyrene in a thickness of 10 cm and covered on its outer face (13) with a film reflecting the visible and red radiation. This has the effect of limiting the contribution of convective heat transfer and with Vû ^ambient sr. Consecutively this allows to reserve a greater part of the heat absorption materialized by the merger of the latent heat storage layer (2) to the supply of the cold source of the heat exchanger (3).

In another variant, when the device is used to non-simultaneously supply the cold source and the hot source of a heat exchanger (3), a multilayer device as shown in FIG. 2 is generally used and comprises a photothermal converter. radiation of the atmosphere and the sun (1) radiating ideally as a black body in the visible and infrared to allow the daytime heating of the converter by absorption of solar radiation and the night radiative cooling of the converter by infrared radiation on the space and atmosphere constituted by way of non-limiting example of a PPO resin plate (polypheniloxide) constituting the active face (4) of the converter (1). When the device is used to power the cold source of the heat exchanger, the converter (1) cools rapidly during the heat removal time corresponding to the night and dry period, to a temperature slightly below the temperature phase change of the MCP, by IR radiation on the atmosphere and space and / or transmission - convection with ambient air. When it reaches this temperature, the MCP solidifies at constant temperature. At the same time, a part of the cold induced by transmission - convection with the ambient air and IR radiation on the space and the atmosphere also feeds by transmission via the latent heat storage layer (2) of low thermal resistance, the cold source of the heat exchanger (3), During the heat absorption time corresponding to the covered, wet, or diurnal periods, when the temperature of the converter becomes higher than the phase change temperature of the MCP, the device is covered with a removable thermal insulation layer (8) made of a material of low thermal conductivity coated on its inner face (11) with a film reflecting the IR radiation and on its outer surface (12) with a radiation reflecting film IR and visible.

This has the effect of limiting convection and transmission heat gains with the ambient air and absorption of solar radiation and / or atmospheric. Consecutively this allows to reserve a greater part of the heat absorption materialized by the melting of the latent heat storage (2) at the supply of the cold source of the heat exchanger (3).

In addition, if the ambient air temperature becomes greater than the operating temperature of the heat exchanger, a removable insulation layer (6) is placed under the heat exchanger. It is made of a material of low thermal conductivity such as extruded polystyrene 10cm thick covered on its outer face (13) of a film reflecting the visible and infrared radiation. This has the effect of limiting the heat input by convection radiation and transmission with the ambient air. Consecutively this allows to reserve a greater part of the heat absorption materialized by the melting of the latent heat storage layer (2) to the supply of the cold source of the heat exchanger (3). When the device is used to supply the heat source of the heat exchanger (3), the converter (1) heats up to a temperature slightly higher than the phase change temperature of the MCP by absorption of solar radiation during the heating time. absorption of heat corresponding to the diurnal and clear periods. This has the effect of melting the latent heat storage composite layer (2) at a constant temperature. At the same time, part of the heat induced by the absorption of solar radiation at the converter (1) also feeds via transmission via the latent heat storage layer (2) of high thermal conductivity, the hot source of the heat exchanger. heat (3). During the evacuation time of the heat corresponding to the nocturnal, covered periods, when the temperature of the converter (1) reaches a temperature lower than the phase change temperature of the MCP, the removable thermal insulation layer (8) is arranged on the converter (1) to limit heat losses by convection with ambient air and IR radiation to space and atmosphere. This has the effect of reserving a large part of the heat release materialized by the solidification of the MCP to the supply of the heat source of the heat exchanger (3).

In addition, if the temperature of the ambient air becomes lower than the operating temperature of the heat exchanger, a removable thermal insulation layer (6) is placed beneath the heat exchanger. It is constituted in a material of low thermal conductivity such as extruded polystyrene 10cm thick covered on its inner side with a film reflecting the infrared radiation. This has the effect of limiting thermal losses by convection and transmission with ambient air and infrared radiation. Subsequently, this allows to reserve a greater part of the heat absorption materialized by the melting of the latent heat storage layer (2) g the supply of the heat sink of the heat exchanger (3). ;

When the multilayer device is only used to supply the heat source of the heat exchanger (3), a multilayer device as shown in FIG. 3 is generally used and comprises a photothermal converter of the solar radiation (1) consisting of a panel whose active face (4) weakly emitting infrared radiation radiates ideally as a black body in the visible formed by way of non-limiting example of black chrome. This has the effect of promoting heating of the converter by absorption of solar radiation and reduction of thermal losses by IR radiation on the atmosphere and space, particularly in the "atmospheric window [8μm-13μm]". During the heat absorption time, corresponding to the diurnal and light periods, the active face of the converter (4) is oriented towards the sun so as to optimize heating of the converter (1) by absorption of solar radiation. This has the effect of melting the latent heat storage layer (2), because the phase change temperature of the latter (2) is lower than the operating temperature of the converter (1). At the same time, part of the heat induced by the absorption of solar radiation at the converter (1) also feeds via transmission via the latent heat storage layer (2) of high thermal conductivity, the hot source of the heat exchanger. heat (3).

During the time of evacuation of heat by infrared radiation on the space and the atmosphere and convection transmission with the ambient air, corresponding to the nocturnal or covered periods, the supply of the hot source of the heat exchanger (3 ) is ensured by the release of heat materialized by the solidification at constant temperature, of the latent heat storage composite layer (2).

Such a device comprises two additional layers:

- The first (5) covers the converter (1). It is transparent to visible radiation and reflects IR radiation. By way of nonlimiting example, this layer (5) consists of two blades of dry air (9) with a thickness of 19 mm separated by walls (10) made of transparent glass visible to the visible radiation. at least one of them being covered with a TiO ₂ ZAg / TiO ₂ triple-layer coating in which each of the layers has a thickness of 18 nm.

- The second (6), located under the heat exchanger is made of a low thermal conductivity material. By way of non-limiting example, this layer (6) may consist of extruded polystyrene 10cm thick covered on its inner side with a film reflecting infrared radiation.

The insulating nature of the air blades makes it possible to reduce the temperature of the upper wall (10) of the device and thus the thermal losses by infrared radiation on the space and the atmosphere of said wall, as well as the thermal losses by convection. , transmission between the converter (1) and the ambient air. In addition, the glass wall covered with a TiO ₂ ZAg / TiO ₂ triple-layer coating reflecting the infrared radiation and transparent to visible radiation, allows the solar heating of the converter and considerably limits its cooling by infrared radiation on the space. As a result, the heat output of the device is increased.

When the incident direct solar flux is insufficient to supply the heat source of the heat exchanger (3), the solar breather is increased on the converter (1) with an additional layer transparent to solar radiation and etched in Fresnel step (7). ) so as to concentrate the solar flux on the converter (1). The use of other concentrators is possible, for example that of flat, parabolic or cylindroparabolic reflective concentrators or of different shape, combined or not with a Fresnel lens, but these concentrators are often more expensive and more cumbersome. This has the effect of increasing the temperature of the converter (1), because the effects of concentrated solar flux are the same as those of the direct solar flux and cause a heating of the converter (1) even greater than the concentration is At night or in cloudy weather, when the temperature of the converter is lower than the phase change temperature of the MCP, the thermal losses of the device are greater than the heat inputs and are all the more important that the temperature of change of the MCP phase and the active face of the device is high, the ambient air temperature is low and the atmosphere is dry and has low emissivity, particularly in the "atmospheric window [8μm-13μm]". limit these thermal losses and thus improve the performance of the device, it is installed on the latter an additional layer of removable thermal insulation (8) manufactured in a material of low thermal conductivity coated on its inner face (11) with a film reflecting the IR radiation. It is removed during the day, in clear weather to ensure the illumination of the converter (1) and consecutively allow its heating above the phase change temperature of the MCP. This has the effect of melting the latent heat storage layer (2). At the same time, part of the heat induced by the absorption of solar radiation at the converter (1) also feeds via transmission via the latent heat storage layer (2) of high thermal conductivity, the hot source of the heat exchanger. heat (3).

In a variant, when the device is used not only to supply the heat source of the heat exchanger (3) but also to increase the electrical power of a PV generator, a multilayer device is generally used as represented in FIG. , comprising a concentrator layer of solar radiation etched Fresnel step transparent to visible radiation and infrared radiation in particular in the "atmospheric window [8μm-13μm]" (7), and a photovoltaic converter of solar radiation and photothermal radiation of the space and atmosphere (1) consisting of a panel covered with one or more PV cells whose active face (4) is covered with a film transparent to visible radiation and radiating ideally as a black body constituted by way of non-limiting example of a Dupont Tefzel®T ² film with a thickness of 62 μm constituting the active face (4) of the converter (1).

The concentrating layer of the solar radiation (7) is positioned above the converters so as to concentrate the solar radiation on the active face (4) of the converter (1).

This has the effect of increasing the temperature of the converter (1) because the effects of concentrated solar flux are the same as those of the direct solar flux and cause a heating of the converter (1) even larger than the concentration is large. This allows the converter (1) to supply the heat source of the heat exchanger (3) and produce electricity.

At the same time, it also favors the cooling of the converter (1) by IR radiation on the space and on the atmosphere because the infrared radiation is all the more important as the temperature of the converter is large and the concentrator layer ( 7) and transparent to infrared radiation in the "atmospheric window [8μm-13μm]". Subsequently, this makes it possible for a given temperature to increase the concentration rate of the incident solar flux within the limit of the maximum operating temperature of the converter (1) in order to increase the electrical power supplied by the converter (1). As non-limiting examples, the concentrator layer (7) can be made from a sheet of high density polyethylene which is as thin as possible so as to increase its transparency, since the latter decreases as its thickness increases. In addition, in order to allow convective cooling of the converter ambient air can flow freely between the converter and the concentrating layer of solar radiation (7). This favors in certain proportion the heat evacuation by convection and transmission with the ambient air and makes it possible to optimize in the same proportion the concentrated solar flux in order to increase the electric power supplied by the converter (1).

During the heat absorption time, the converter (1) is oriented towards the sun so as to optimize its illumination. The latter (1) heats up quickly by absorption of solar radiation to a temperature slightly higher than the phase change temperature MCP contained in the latent heat storage layer (2). When it reaches this temperature, the MCP melt at constant temperature. This has the effect of considerably slowing down the heating of the converter (1), because the thermal resistance and the mass of the latent heat storage composite layer (2) make it possible to maintain the temperature of the converter at a level close to the temperature of change of heat. phase of the MCP.

At the same time, part of the heat induced by heating the active face (4) of the converter (1) also feeds via transmission via the latent heat storage composite layer (2) of low thermal resistance, the heat source of the exchanger heat (3).

During the heat removal time, when the operating temperature of the converter (1) is lower than the phase change temperature of the MCP, the latter solidifies by yielding heat by convection, transmission and radiation via the converter (1). ).

To improve its thermal performance, such a device comprises two additional layers:

- The first is a removable thermal insulation layer (8) which covers the active face of the device when the temperature of the converter (1) is lower than the phase change temperature of the MCP and when the amount of heat removed via the The exchanger is sufficient to solidify the latent heat storage layer (2) alone. This removable thermal insulation layer (8) is covered on its inner face (11) with a film reflecting IR radiation and is made of a material of low thermal conductivity. This has the effect of limiting thermal losses by convection and transmission with ambient air, and by IR radiation to space and to the atmosphere. Subsequently, it allows to reserve a greater part of the heat release materialized by the solidification of the latent heat storage composite layer (2) to the supply of the hot source of the heat exchanger (3). The removable thermal insulation layer (8) is removed during the day to ensure the illumination of the converter and consecutively allow its heating and the production of electrical energy. - The second (6) is located under the heat exchanger (3). It consists of a material of low thermal conductivity. By way of non-limiting example, this layer (6) may consist of extruded polystyrene 10cm thick covered on its inner side with a film reflecting infrared radiation.

This has the effect of reducing heat losses via the exchanger (3) by convection and transmission with ambient air. As a result, it increases the amount of heat supplied to the heat source of the heat exchanger (3). In addition, when the heat source of the heat exchanger (3) is insufficiently stressed during the heat removal time ensuring the solidification of the latent heat storage layer (2), the device is not covered with the removable thermal insulation layer (8). This allows the converter (1) to be cooled by IR radiation on the space and the atmosphere and by convection - transmission with the ambient air to ensure the solidification of the latent heat storage composite layer (2).

Claims

A multilayer thermal energy collector device comprising at least one heat exchanger (3), a latent heat storage composite layer (2) impregnated with a phase change material (PCM) and a photovoltaic or photothermal converter ( 1), characterized in that the device uses a technique for managing radiative cooling by infrared radiation on the space applied to the photothermal conversion of atmospheric radiation, solar radiation, and the photovoltaic conversion of solar radiation, implanted in an atmosphere clear and dry having a high transparency and low emissivity in the "atmospheric window [8μm-13μm]", in that the active surface radiates like a black body in the "atmospheric window [8μm-13μmJ", and in that it comprises an additional layer of removable thermal insulation (8).

2. multilayer thermal energy collector device according to claim 1, characterized in that the device operates at a temperature close to the phase change temperature of the MCP and between 250 ⁰ K and 800 ⁰ K.

3. multilayer thermal energy collector device according to claims 1 and 2, characterized in that the converter (1) is a photothermal converter of the radiation of the atmosphere whose active face (4) radiates towards the zenith in an angle included between 0 ° and 30 ° to reduce heat gains by absorbing radiation from the "atmospheric window [8μm-13μm]".

4. multilayer thermal energy collector device according to claims 1, 2 and 3, characterized in that the active face (4) of the converter (1) radiates ideally as a black body over the entire infrared spectrum and reflects the visible in view to produce cold (3) if, for a given dimension and an identical active operating temperature of the converter (1), such an active face (4) radiates more energy than an active face (4) which would be spectrally selective in the "atmospheric window [8μm ~ 13μm]".

5. multilayer thermal energy collector device according to claims 1, 2 and 3, characterized in that the active face (4) of the converter (1) is a spectrally selective surface in the "atmospheric window [8μm-13μm]" in to produce cold if, for a given dimension and an identical active operating temperature of the converter (1), such an active face (4) radiates more energy than an active face (4) which radiates like a black body over the entire infrared spectrum and reflect the visible.

6. Multilayer thermal energy collector device according to claims 1, 2 and 3, characterized in that the converter (1) is a photothermal converter of the radiation of the atmosphere and the sun radiating ideally as a black body in the visible and the infrared to allow diurnal heating of the converter by absorption of solar radiation and nocturnal radiative cooling of the converter by infrared radiation on space and atmosphere when the device feeds non-simultaneously the hot source and the cold source of the heat exchanger (3).

Multilayer thermal energy collecting device, according to claims 1, 2 and 3, characterized in that the converter (1) is a photothermal converter of atmospheric radiation and photovoltaic solar radiation consisting of a panel covered with one or more PV cells whose active face is covered with a film transparent to visible radiation and radiating ideally as a black body in the infrared spectrum,

8. multilayer thermal energy collector device according to claim 1, 2, 3, 4 and 5 characterized in that it comprises at least one wall (10) separated from the converter by a vacuum blade or dry air large thermal and transparent resistance at least in "atmospheric window [8μm-13μm]" to reduce heat transfer by transmission - convection with the outside air and to favor the evacuation of heat by infrared radiation on the space and the atmosphere when the active operating temperature of the converter is lower than the ambient air.

9. multilayer thermal energy collector device according to claims 1, characterized in that it comprises at least one wall (10) separated from the converter by a vacuum blade or dry air of high thermal resistance to reduce the temperature of said wall, such a wall (10) reflecting the infrared radiation and transmitting the solar radiation to reduce the thermal losses of the device by infrared radiation on the space and the atmosphere and by convection-transmission with the outside air and allow the heating the converter by absorption of solar radiation when the device supplies the heat source of the heat exchanger (3) at a temperature higher than the ambient air.

10. multilayer thermal energy collector device according to claims 1, 2, 3, 5, and 6 characterized in that it comprises an additional layer concentrating solar radiation (7), consisting of a panel engraved in echelon Fresnel, transparent to the IR radiation and solar radiation arranged on the upper face of the device for concentrating the solar flux on the active converter face (1) and to promote its radiative cooling by infrared radiation on the space and the atmosphere in the "window atmospheric [8μm-13μm].

11. According to another characteristic, the device operates in a two-cycle cycle, a time of evacuation of heat by infrared radiation on the space and the atmosphere and / or by convection - transmission with the ambient air, materialized by the constant temperature solidification of MCP, a time of absorption of heat by absorption of solar radiation, atmospheric and / or convection - transmission with ambient air, materialized by the melting at constant temperature of the MCP.

Multilayer thermal energy collecting device according to claims 1 to 11, characterized in that the latent heat storage composite layer (2) is placed in close contact with the photonic converter (1) and the heat exchanger ( 3) to promote thermal exchange by transmission and in that its thermal resistance and its mass allow it to maintain the temperature of the converter (1) and the heat exchanger (3) to a level close to the temperature of change of phase of the MCP.

13. Multilayer thermal energy collector device according to claims 1, 2, 3, 4, 5, 6, 8, 10, 11 and 12 characterized in that the active operating temperature of the converter is lower than the temperature of change of the MCP to allow solidification of the MCP during the cooling time when the device feeds the cold source of the heat exchanger.

Thermal energy collector multilayer device according to claims 1, 6, 7, 9, 10, 11 and 12 characterized in that the active operating temperature of the converter is greater than the phase change temperature of the MCP to enable the merger of

MCP during the warm-up time when the device is supplying the hot source of the heat exchanger.

15. Multilayer thermal energy collector device according to claims 1, 2, 3, 4, 5, 6, 8, 10, 11, 12 and 13, characterized in that an additional layer of removable thermal insulation (8) made of a material of low thermal conductivity coated on its outer surface with a film reflecting solar and infrared radiation is disposed on the device when the operating temperature of the converter becomes greater than at the phase change temperature of the MCP to reduce the heat gains by absorption of atmospheric and / or solar radiation and to reserve most of the latent heat of fusion of the MCP to the supply of the heat sink of the exchanger of heat, said removable insulation layer (8) being removed when a spectrally identical surface to the active face of the converter (1) radiating under the same conditions as the converter (1) and in an identical device not including the removable thermal insulation layer (8) reaches a temperature below the phase change temperature of the MCP.

16. multilayer thermal energy collector device according to claims 1, 6, 7, 9, 10, 11, 12, 14 characterized in that an additional layer of removable thermal insulation (8) formed in a low material thermal conductivity coated on its inner side with a film reflecting the infrared radiation is disposed on the device when the operating temperature of the converter becomes lower than the phase change temperature of the MCP to reduce thermal losses via the converter (1) by infrared radiation over the space and the atmosphere and reserve most of the heat stored during the melting of the MCP during the warm-up time at the supply of the heat source of the heat exchanger when the device powers the heat source of the heat exchanger (3), said removable insulation layer (8) being removed when a surface spectrally identical to the active ace (4) of the converter (1) radiating under the same conditions as the converter (1) and in an identical device not comprising the removable insulation layer (8) reaches a temperature above the phase change temperature of the MCP.

17. multilayer thermal energy collector device according to claims 1 to 16 characterized in that the device comprises an additional layer of thermal insulation (6) made of a low thermal conductivity material to reduce heat leakage between the heat exchanger of heat (3) and the mood.

18. multilayer thermal energy collector device according to any one of claims 1 to 17 characterized in that the latent heat storage composite layer (2) is an anisotropic body composed of expanded natural graphite (GNE) and a phase change material (PCM) of an energy density of at least 150KJ / Kg and a directional thermal conductivity at least 25W ^* / m.