WO2013034593A2 - Solar-thermal collector - Google Patents

Abstract

The present invention relates to a solar-thermal collector with a collector housing, which at least in certain regions is at least partially or completely transparent to radiation in the infrared and/or visible range of the electromagnetic spectrum, and an absorber arranged in the collector housing for converting sunlight into thermal energy as well as a heat transmission device for transporting away the usable heat.

Description

 Solar thermal collector

The present invention relates to a solar thermal collector having a collector housing which is at least partially or completely transparent to radiation in the infrared and / or visible region of the electromagnetic spectrum, and an absorber arranged in the collector housing for converting sunlight into thermal energy and a heat transfer device for the removal of the usable heat.

Solar thermal collectors reach an operating temperature that depends primarily on the impinging solar radiation and the dissipated heat. Typical operating temperatures for indoor applications are 50 to 100 ° C. At these operating temperatures, the collectors should have high efficiencies, ie have the lowest possible heat losses. At high irradiation (eg 800 W / m ² and ber) and little or no heat dissipation sets an operating point with a very high operating temperature. This temperature can reach today's marketable collectors in Stagnationsf ll - ie in the absence of any heat dissipation - 200 ° C or even significantly higher. A lack of heat dissipation can be done on the one hand, if no heat sink is available, for example because the heat storage is completely loaded, or in case of damage, for example in case of failure of the pump in the solar circuit. Solar thermal collectors and systems must be designed so that they survive this stagnation case without damage. However, this considerably limits the choice of production materials and construction and embodiments. For example, there are narrow limits for the use of low-cost polymer materials, as they survive such high temperatures permanently. Form also innovative From guide, such as thermal-photovoltaic panels, which also provide electricity and heat, require a temperature limitation since the Auflamination of the solar cells is not high temperature stable forth ^¬ adjustable on the thermal absorber.

In this respect, methods that make it possible to switch the heat loss of the collector in a temperature-dependent manner are leading. This can basically be done via the collector top or the back of the collector.

In the past, a variety of ways have already been investigated to limit the temperature of solar thermal collectors under high insolation and inadequate or nonexistent heat dissipation. For this purpose, the following paths have been followed: Circuit of transmission:

Systems have been studied and tried to develop in which the transmission of the outer upper cover of a solar thermal collector decreases above a switching temperature and thus the energy input that reaches the absorber is limited {DE 20 2005 007 474 Ul). One embodiment of such a solution was so-called thermotropic layers. However, no technical feasibility was achieved.

Circuit of the emission of the surface layer of the absorber in the infrared region of the radiation spectrum:

It was attempted to develop layers that allow a targeted increase in the radiation emission in the heat radiation (DE 10 2008 038 795 AI). So far, however, this approach was not technically feasible.

Circuit of the heat conduction in the gas space between absorber and glass cover:

One way to specifically influence the heat transfer between absorber and glass cover, is the adjustment of the gas pressure in this space (eg as presented on the website of U IKOLL - www.unikoll.eu/beschreibung_unikoll.html). This requires a circuit of heat conduction. However, a considerable negative pressure must be achieved in order to achieve a visible switching stroke. chen. Accordingly, essential measures must be taken to absorb the pressure on the glass cover in the evacuated state. This is possible in principle, there are vacuum flat plate collectors, which have corresponding supports to absorb the pressure on the glass cover. However, so far no technical implementations are known in which such a solution was successful in combination with a targeted change in the gas pressure in the collector interior for switching the heat loss.

4) Adjustable ventilation of the space between the absorber and the glass cover:

By a targeted closable opening of the gap between absorber and glass cover the heat loss on the top can be increased (WO 2004/070289 AI). Disadvantage is the requirement of a mechanical component and the risk of contamination of the interior. So far, no implementation is known that is based on such an approach.

So far, no solution is known, which has achieved the goal of lowering the stagnation temperature by targeted adjustment of the thermal collector losses and has proven a technical feasibility. In this respect, today only materials and constructions are used that sufficiently withstand the stagnation temperatures achieved.

Based on this, it was an object of the present invention to provide a solar thermal collector with which the heat loss of the collector can be switched depending on the temperature. This object is achieved by the solar thermal collector with the features of claim 1. The other dependent claims show advantageous developments. In claims 13 to 15 uses according to the invention are given.

According to the invention, a solar thermal collector is provided with a collector housing which is at least partially or completely transparent at least partially for radiation in the infrared and / or visible region of the electromagnetic spectrum, and an absorber arranged in the collector housing for converting sunlight into thermal energy and at least a heat transfer device for the removal of the usable heat.

The solarthermisehe collector according to the invention is characterized in that within the collector housing at least one working fluid and at least one sorbent for the working fluid are contained, wherein the sorbent and the working fluid are coordinated so that an increase in the temperature of the solar thermal collector to a desorption of the working fluid from the sorbent and a lowering of the temperature of the solar thermal collector to a sorption of the working fluid by the

Sorbent leads.

A first variant of the solar thermal collector according to the invention provides that this is a flat collector, which, starting from the collector upper side exposed to the incident radiation towards the collector rear side, has the following structure: a) the coverage that is at least partially or completely transparent to radiation in the infrared and / or visible region of the electromagnetic spectrum;

b) gas space,

c) absorber,

d) a heat transfer device, which allows a removal of the usable heat, as well as

e) at least one thermal insulation panel,

 in particular a vacuum insulation panel, as well as f) a back cover, which limits the solar thermal collector on the opposite side of the transparent cover, wherein the sorbent is integrated in the thermal insulation panel on the absorber side facing the thermal insulation panel as a layer or selectively deposited or wherein the sorbent is integrated in a separate compartment associated with the thermal insulation panel.

In a further preferred variant, the solar thermal collector in the space between the at least partially or completely transparent cover for radiation in the infrared and / or visible region of the electromagnetic spectrum and the absorber on a transparent thermal insulation.

A further variant according to the invention provides that the solar thermal collector is an evacuated flat collector with a cover which is at least partially or completely transparent for radiation in the infrared and / or visible region of the electromagnetic spectrum, the sorbent being present at any desired temperature. ger position in the collector housing is integrated. An advantageous arrangement of the sorbent takes place on the side facing away from the gas space side of the absorber and in close thermal contact with the absorber.

A third variant according to the invention provides that the solar thermal collector is an evacuated tube collector, the tube consisting of a material which is at least partially or completely transparent to radiation in the infrared and / or visible range of the electromagnetic spectrum, and in particular glass and / or a polymer material the absorber is disposed inside the tube, the sorbent being disposed at any position in the tube, and when the temperature of the collector is raised, the sorbent releases the working fluid into the interior of the tube. An advantageous attachment of the sorbent takes place on the side facing away from the gas chamber side of the absorber and in close thermal contact with the absorber.

Preferably, the sorbent is an adsorption and / or absorption material. This is preferably selected from the group consisting of zeolites, zeolite-type materials, aluminophosphates, silica aluminophosphates, metal aluminophosphates (MeAPOs), zeolitic imidazolate frameworks (ziFs), organometallic framework and network compounds, porous coordination polymers

(PCP)), mesoporous alumino and silicon compounds, activated carbons, carbon molecular sieves, carbon nanotubes, silica gels, hexacyano metallates and / or combinations thereof. The zeolites are preferably selected from the group consisting of zeolite A, zeolite 4A, zeolite 5A, zeolites X (faujasites), in particular zeolite 13X, zeolites Y, zeolites of the abovementioned groups with balancing cations selected from the group consisting of H, Li, Na , Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, Ra and / or the rare earth cations, in particular La, and the lanthanides and actinium and the group of actinides.

The aluminophosphates are preferably selected from the group consisting of AIPO-4, AlPO-1, AlPO-18, AlPO-5, AlPO-11 or mixtures thereof.

The metal aluminophosphates (MeAPOs) are preferably selected from the group consisting of FAPO-5 (iron-AlPO-5), MeAPO-11 or mixtures thereof.

The silica aluminophosphates are preferably selected from the group consisting of SAPO-34, SAPO-44, SAPO-18, SAPO-5, SAPO 11, or mixtures thereof.

The zeolitic imidazolate framework (zeolitic imidazolate frameworks (ZiF)) is preferably ZiF-8.

The organometallic framework and network compounds or porous coordination polymers (PCPs) are preferably selected from the group consisting of ZMOFs (zeolite-like MOFs), in particular HKUST-1 and / or the group of Materiaux de l ¹ Institut Lavoisier (MILs), in particular MIL-53, MIL-100, MIL-110 and / or MIL-101 and the group of materials DUT (Dresden University of Technology) in particular DUT-6 and the group of materials UiO (University of Oslo ), in particular UiO-66 and ISE-1 or mixtures thereof. Preferably, the working fluid is selected from the group consisting of water, ozone, nitrous oxide, carbon dioxide, carbon monoxide, noble gases and gaseous at temperatures above 80 ° C under normal conditions

Hydrocarbons or alcohols, in particular methane, ethane, methanol or ethanol and combinations or mixtures thereof. In a further preferred variant, the solar thermal collector has at least one solar cell on the surface of the absorber. The solar cells can be deposited, coated or glued.

The e solar thermal collectors according to the invention are used in particular as facade collectors or roof collectors. They can be used to generate hot water and / or warm air. Further possible fields of application are the

Building heating, building drying, providing process heat, e.g. for bakeries, electroplating shops, laundries or paint shops as well as the drying of food, chemical products, wood or pellets. Likewise, the collectors for operating thermally driven chillers, preferably sorption-supported chillers can be used.

Reference to the following figures and examples, the subject invention is to be explained in more detail, without einzushränken this to the specific embodiments shown here.

In Fig. 1 is a cross section of a solar thermal collector according to the invention is shown with Vakuumisolationspaneel. In Fig. A further variant of the invention solar thermal collector is shown as a flat collector with vacuum insulation panel in cross section.

Fig. 3 shows a cross section of a variant of a solar thermal collector according to the invention as an evacuated flat collector.

4 shows a further variant of a solar thermal collector as an evacuated flat collector in cross section,

Fig. 5 shows a variant of a solar thermal collector according to the invention as an evacuated tube collector based on a sectional view.

FIG. 6 shows a further variant of a solar thermal collector according to the invention as an evacuated tube collector on the basis of a sectional representation.

Fig. 7 shows a variant of a solar thermal collector according to the invention as

 Flat collector with vacuum insulation panel in cross-section, which contains photovoltaic cells on the top of the absorber.

8 shows a further variant of a solar thermal collector according to the invention as a flat collector with a vacuum insulation panel in cross-section, which contains a transparent thermal insulation. 9 shows, by way of a diagram, the characteristic curves of a solar thermal collector according to the invention in comparison to a solar thermal collector known from the prior art.

1 shows a solar thermal flat collector 1 according to the invention, which has an absorber 2 in which heat exchanger tubes 7 are integrated. Furthermore, the flat collector on a transparent cover 3, which by a gas space 4 from the absorber. 2

is spaced. The flat collector further has a vacuum insulation panel 8, in which on the absorber 2 side facing a sorbent 5 is arranged. The flat collector further has a rear cover 9.

The embodiment of FIG. 2 corresponds substantially to the embodiment of FIG. 1, but here the sorbent 5 is arranged point by point on the side facing the absorber 2 in the vacuum insulation panel 8.

FIG. 3 shows a variant according to the invention of an evacuated solar thermal collector 1. The evacuated flat collector 1 has an absorber 2 with integrated heat exchanger tubes 7. At the same time, the collector has a transparent cover 3, which is spaced from the absorber 2 by a gas space 4. In this evacuated flat collector according to the invention, the sorbent 5 is arranged on the side of the absorber 2 facing away from the gas space 4. The flat collector 1 also has a back cover 9.

The embodiment according to FIG. 4 corresponds in the sentlichen the embodiment of FIG. 3, but here the sorbent 5 is selectively arranged on the back of the absorber 2. In Fig. 5, a further variant of the invention in the form of an evacuated tube collector 11 is shown as SchnittZeichnung. The collector 1 has a tube wall 16, which includes an absorber 2 and heat exchanger tubes 17. The sorbent 5 is according to this embodiment on the back of the

Absorbers 2 arranged between the Wärmetauseherröhren 7.

FIG. 6 shows a further embodiment of an evacuated tube collector 11 according to the invention. The tube collector 11 has an outer tube wall 16 and an inner tube wall 13. In the area between the inner tube wall 13 and the outer tube wall 16 there is a vacuum. The enclosed by the inner tube wall space, however, is not evacuated. In this, a cylindrical absorber 12 is arranged, are connected to the heat exchanger tubes 17. The sorbent 15 is arranged in the present case in the evacuated region between the inner tube wall 13 and the outer tube wall 16.

FIG. 7 shows a further variant according to the invention of a flat collector 1, which represents a development with respect to the flat collector shown in FIG. In addition to this, the flat collector 1 according to FIG. 7 has solar cells 10, which are arranged on the side of the absorber 2 facing the gas space 4.

In Fig. 8 is another variant of the invention a flat plate 1 with vacuum insulation onspaneel 8 shown, which also represents a development compared to the flat collector of FIG. 1. In this case, the flat collector 1 has a transparent heat insulation 11 between the absorber 2 and the transparent cover 3.

In Fig. 9, the characteristics of a solar thermal collector according to the invention and a solar thermal see collector according to the prior art, which has no switchable thermal insulation shown. The illustration shows the course of the efficiency of a solar thermal collector as a function of the operating temperature. The point of intersection with the ABS zisse shows the maximum operating temperature (Stagna ^¬ tion temperature) that can reach a solar thermal collector, if no useful heat is dissipated and the total generated heat at the absorber in the form of thermal loss is dissipated to the environment. The illustration shows that a conventional solar thermal collector can reach a high stagnation temperature over 200 ° C. In contrast, a collector according to the invention achieves a significantly lower stagnation temperature, without having a lower efficiency than a conventional solar thermal collector in the range of low operating temperatures. This lowering of the stagnation temperature is achieved by the incorporation according to the invention of a sorbent and a working medium, which lead to a desorption of the working medium at a sufficiently high temperature and thus to an increase in pressure and a corresponding increase in the thermal losses.

Claims

claims Solar thermal collector (1) with a collector housing, which is at least partially or completely transparent to radiation in the infrared and / or visible region of the electromagnetic spectrum, and an absorber (2) arranged in the interior of the collector housing for converting sunlight into thermal energy and at least ei ^¬ ner heat transfer device (7) for the removal of the usable heat, characterized in that contained in the interior of the collector housing at least one working fluid and at least one sorbent (5) for the working fluid, wherein the sorbent (5) and the working means to each other are agreed that an increase in the temperature of the sola thermal collector leads to a desorption of Arbeitsmi means of the sorbent (5) and a lowering of the temperature of the solar thermal collector to a sorption of the working fluid by the sorbent (5). Solar thermal collector according to claim 1, characterized in that the solar thermal collector (1) is a flat collector, which, starting from the incident of the incident radiation collector upper side towards the collector back, has the following structure: a) for radiation in the infrared and / or visible range of the electromagnetic Spectrum at least partially or completely transparent cover (3), b) gas space (4), c) absorber (2), d) the heat transfer device (7) and e) at least one thermal insulation panel (8), in particular a vacuum insulation panel and f) a back cover (9) delimiting the solar thermal collector (1) on the side opposite the transparent cover (3), the sorbent (5) being in the thermal insulation panel on the side of the absorber (2) integrated thermal insulating panel (8) as a layer or selectively deposited or wherein the sorbent is integrated in a separate compartment, which is in communication with the thermal insulation panel. Solartherm shear collector according to claim 2, characterized in that the solar thermal collector (1) in the space between the radiation in the infrared and / or visible region of the electromagnetic spectrum at least partially or completely transparent cover (3) and the absorber (2) a transparent Thermal insulation (11) contains. Solar thermal collector according to claim 1, characterized in that the solar thermal collector (1) is an evacuated flat collector with one for radiation in the infrared and / or visible region of the electromagnetic Spectrum at least partially or completely transparent cover (3), wherein the sorbent (5) is integrated at any position in the collector housing. Solar thermal collector according to claims 1 and 3 or according to claims 1 and 4, characterized in that the sorbent (5) on the of Gas chamber (4) facing away from the absorber (2) is arranged. Solar thermal collector according to claim 1, characterized in that the solar thermal collector (1) is an evacuated tube collector, wherein the tube (16) consists of a for radiation in the infrared and / or visible region of the electromagnetic spectrum at least partially or completely transparent material, in particular glass and / or one Polymer material, and is arranged inside the tube of the absorber (2), wherein the sorbent (5) is arranged at any position in the tube and with an increase in the temperature of the collector, the sorbent (5) the working fluid into the interior of the tube releases. Solar thermal collector according to one of the preceding claims, characterized in that the sorbent (5) consists of an adsorption and / or absorption material selected from the group consisting of Zeolites, zeolitic materials, aluminophosphates, silica aluminophosphates, metal aluminophosphates (MeAPOs), zeolitic Imidazolate frameworks (Zeolitic Imidazolate Frameworks (ZiFs)), organometallic framework and network compounds, porous coordination polymers (PCPs), mesoporous alumino and silicon compounds, activated carbons, carbon molecular sieves, carbon nanotubes, silica gels, hexacyanometallates and / or combinations thereof or essentially contains them. Solar thermal collector after preceding the claim characterized in that a) the zeolites are selected from the group consisting of zeolite A, zeolite 4A, zeolite 5A, zeolites X (faujasites), in particular zeolite 13X, zeolites Y, zeolites of the abovementioned groups with compensation cations selected from the group consisting of H, Li, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, Ra and / or the rare earth cations, in particular La and the lanthanides and Actinium and the group of actinides or mixtures thereof, b) the aluminophosphates are selected from the group consisting of A1PO-4, AlPO-14, A1PO-18, A1PO-5, A1P0-11 or mixtures thereof, c) the metal aluminophosphates (MeAPOs) are selected from the group consisting of FAPO 5 (iron-AlPO-5), MeAPO-11 or mixtures thereof,  the silica aluminophosphates are selected from the group consisting of SAPO-34, SAPO-38, SAPO-44, SAPO-18, SAPO-5, SAPO-41 or mixtures thereof,  the zeolitic imidazolate framework (ZiF) ZiF-8, the organometallic framework and network compounds and the porous coordination polymers (PCP) are selected from the group consisting of ZMOFs {zeolite like MOFs) , especially  H UST-1 and / or the group of Materiaux de 1 'Institut Lavoisier (MILs), in particular MIL-53, MIL-100, MIL-110 and / or MIL-101 and the group of materials DUT (Dresden University of Technology) in particular DUT-6 and the group of materials UiO (University of Oslo), in particular uiO-66 and ISE-1, or mixtures thereof. Solar thermal collector according to one of the preceding claims, characterized in that the working fluid is selected from the group consisting of water, ozone, nitrous oxide, carbon dioxide, carbon monoxide, noble gases and at temperatures above 80 ° C under normal conditions gaseous hydrocarbons or alcohols, in particular methane, ethane, methanol or ethanol and combinations or Mixtures of these. Solar thermal collector according to one of the preceding claims, characterized in that the arming device comprises a liquid heat transfer medium or at least one heat pipe. Solar thermal collector according to one of the preceding claims, characterized in that the solar thermal collector {1) has at least one solar cell (10) on the surface of the absorber (2). Solar thermal collector according to claim 11, characterized in that the at least one solar cell (10) on the absorber (2) deposited, coated or glued. Use of a solar thermal collector according to one of the preceding claims as Fasadenkollektor and / or roof collector. Use of a solar thermal collector according to one of the preceding claims for producing hot water or for heating another liquid and / or warm air. Use of a collector according to any one of the preceding claims for Gebäudehe tion, building detrocknung, providing process heat, eg for bakeries, galvanic plants, laundries or paint shops, drying of food, chemical products, wood and / or pellets, for operating thermal power NEN chillers, preferably sorption-based chillers.