CN103574948A - Solar selective absorbing coating - Google Patents

Solar selective absorbing coating Download PDF

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Publication number
CN103574948A
CN103574948A CN201210279294.7A CN201210279294A CN103574948A CN 103574948 A CN103574948 A CN 103574948A CN 201210279294 A CN201210279294 A CN 201210279294A CN 103574948 A CN103574948 A CN 103574948A
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China
Prior art keywords
solar
absorbing coating
selectively absorbing
layer
semiconductor
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CN201210279294.7A
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项晓东
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YIKEBO ENERGY SCIENCE AND TECHNOLOGY (SHANGHAI) Co Ltd
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YIKEBO ENERGY SCIENCE AND TECHNOLOGY (SHANGHAI) Co Ltd
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Priority to CN201210279294.7A priority Critical patent/CN103574948A/en
Publication of CN103574948A publication Critical patent/CN103574948A/en
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/40—Solar thermal energy, e.g. solar towers

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Abstract

The invention relates to the technical field of solar energy and discloses a solar selective absorbing coating. The solar selective absorbing coating comprises a metallic reflective layer and a semiconductor absorption layer formed on the metallic reflective layer, wherein the metallic reflective layer is prepared from Al, and the semiconductor absorption layer is prepared from Ge. According to the solar selective absorbing coating, the advantage that a Ge semiconductor is steep in energy band cutoff and has little adverse effect on the low infrared emissivity of metal Al is effectively exerted, so that a solar-system heat collector can absorb solar spectra to the maximum and effectively inhibit infrared radiation, and the limitations to the high-temperature application of the traditional selective absorbing coatings are broken through.

Description

Solar selectively absorbing coating
Technical field
The present invention relates to technical field of solar, particularly a kind of solar selectively absorbing coating.
Background technology
Solar energy is a kind of inexhaustible clean energy resource, yet because energy density after its arrival earth is little, brings difficulty to large-scale exploitation.This has just determined that solar energy is directly used in before daily life and industrial production, must improve the energy density of solar energy.Solar selectively absorbing coating is very high to the absorptivity of visible ray, and self infrared emittance is very low, low-grade solar energy can be converted to high-grade heat energy, solar energy is played to enrichment, solar energy is a kind of inexhaustible clean energy resource, yet because energy density after its arrival earth is little, bring difficulty to large-scale exploitation.This has just determined that solar energy is directly used in before daily life and industrial production, must improve the energy density of solar energy.Solar selectively absorbing coating is very high to the absorptivity of visible ray, and self infrared emittance is very low, low-grade solar energy can be converted to high-grade heat energy, and solar energy is played to enrichment.Therefore, preparing efficient solar selectively absorbing coating is the key technology in solar thermal utilization, most important to improving collector efficiency.
According to the difference of principle of absorption and coating structure, coating for selective absorption can be divided into following several: 1. utilize the surface texture of micro-rough, can absorb shortwave radiation, but infra-red radiation is produced to mirror-reflection, form selectively and absorb; 2. utilize the interference effect between multilayer film to obtain selective absorption; 3. utilize nano metal-dielectric composite material to form selectively absorbing layers; 4. metal-semiconductor composite construction: select the less semiconductor of energy gap Eg, energy is absorbed higher than the photon of Eg, and energy sees through lower than the photon (far infrared) of Eg, and metal pair infrared light has good reflection, thus it is selective to form spectral absorption.Based on mechanism selective absorbing material 3., it is the scheme that the current overwhelming majority has the solar thermal collector of using value to adopt.Based on mechanism technology path 4., be never used in actual applications, because common semiconductor is to the absorptivity of solar spectrum lower (<0.7), while being applied to common flat board or tubular type collector.
Up to now, domestic and international most of research work concentrates on cryogenic selective absorber coatings, and the selective transition region of these coatings is very wide, but can meet selective under low temperature.For example, in the time of 100 ℃, the peak wavelength of infra-red emission is about 5-6 micron, away from solar radiation spectral wavelength, and selectively enough being separated of these coatings.Yet along with temperature raises, infrared emission peak is by the afterbody of convergence solar spectrum gradually.Under 400 ℃ of conditions, the infrared emission peak of selective absorbing material and solar spectrum have more overlapping, and desirable separation wavelength is 2 microns of left and right, needs very narrow transition region to be separated.Therefore,, because semi-conducting material has narrower absorptive transition district, the coating for selective absorption that makes semiconductor-metal cascaded structure has obvious advantage with respect to the coating for selective absorption of conventional three-dimensional nano composite structure.
For the coating for selective absorption structure of semiconductor-metal series connection, require that semiconductor absorption coefficient is large and ABSORPTION EDGE is steep, metal fever emission ratio is low.At present, applying maximum semi-conducting materials is silicon, and the absorption coefficient under room temperature can reach 15% with the ratio of emission ratio.But the cutoff wavelength of silicon, in about 1.1u m, can not absorb the solar spectrum energy between 1.1um-2um, reduce absorption energy, therefore limited～raising.
But, above-mentioned multiple existing coating for selective absorption is out of shape because at high temperature absorbing film structural molecule is oxidized, a little less than oxidation resistance, thereby cause the shortcoming that sunshine absorptivity is low, cannot be applied in the high temperature heat collector field of 150 ℃-600 ℃, therefore, this area is in the urgent need to researching and developing a kind of high heat absorption efficiency, low thermal emissivity, can being applied in the solar selectively absorbing coating on elevated operating temperature heat collector.
Summary of the invention
The object of the present invention is to provide a kind of solar selectively absorbing coating, solve the wider high temperature causing in existing coating for selective absorption spectral transition district and apply limited problem.
For solving the problems of the technologies described above, the invention provides solar selectively absorbing coating, comprise metallic reflector and be formed on the semiconductor absorption layer on metallic reflector, metallic reflector is Al, semiconductor absorption layer is Ge.
Optionally, between metallic reflector and semiconductor absorption layer, be provided with infrared transparent oxide skin(coating).
Optionally, infrared transparent oxide skin(coating) is Cr 2o 3, Al 2o 3or TiO 2.
Optionally, metallic reflector below is provided with adhesion layer, and adhesion layer is Ni, Ti or Cr 2o 3.
Optionally, semiconductor absorption layer surface is micro-rough matte.
Optionally, micro-rough surface applies anti-oxidation protection layer.
Optionally, semiconductor absorption layer surface is provided with 1～3 layer of anti-reflection film.
Optionally, 2 layers of anti-reflection film cover conductor absorbed layer surface successively, and anti-reflection film is Si 3n 4, SiO 2+ SiN 4.
Optionally, anti-reflection film surface applies anti-oxidation protection layer, and anti-oxidation protection layer is SiO 2.
Optionally, it is characterized in that, coating for selective absorption is coated on the surface of best bright finish.
The present invention compared with prior art, the main distinction and effect thereof are: semiconductor absorption layer and metallic reflector combine, steep and to the little advantage of Al metal low infrared emissivity negative effect by effectively bringing into play Ge semiconductor energy gap cut-off, the system heat collector of making absorbs solar spectral to greatest extent, and effectively suppresses infra-red radiation.Under 400 ℃ of conditions, the infrared emission peak of selective absorbing material and solar spectrum have more overlapping, and desirable separation wavelength is 2 microns of left and right.Therefore in order to promote the middle high temperature application of coating for selective absorption, selecting cutoff wavelength is that the semi-conducting material of 2 microns of left and right is ideal, the semi-conductive cutoff wavelength of Ge is 1.85um left and right, and ABSORPTION EDGE is steeper, meet the condition as semiconductor-metal series composite structure coating for selective absorption absorbed layer material completely.Another aspect Al metallic reflector heat emissivity coefficient can resist 0.02, and not oxidizable under high temperature, is suitable as very much the metallic reflector of semiconductor-metal series composite structure coating for selective absorption.This solar selective coat can be widely used in (heat generating system, solar water heater system, solar air-conditioner system etc.) in photo-thermal system, greatly reduces the thermal radiation loss of system, thereby improves the efficiency of system; Be applied to can make operating temperature improve 2-3 doubly in solar water heater system; Be applied to can make system effectiveness improve 5-6% left and right in solar heat power generation system, greatly promote solar thermal collector in the application of high-temperature field.
Accompanying drawing explanation
Fig. 1 is the structural representation of the first embodiment of solar selectively absorbing coating of the present invention;
Fig. 2 is the structural representation of the first embodiment of solar selectively absorbing coating of the present invention.
Fig. 3 is that solar selectively absorbing coating of the present invention is while being applied to solar water heater and the difference figure of the operating temperature of non-selectivity coating and traditional selective coating solar water heater.
The specific embodiment
In the following description, in order to make reader understand the application better, many ins and outs have been proposed.But, persons of ordinary skill in the art may appreciate that even without these ins and outs and the many variations based on following embodiment and modification, also can realize each claim of the application technical scheme required for protection.
For making the object, technical solutions and advantages of the present invention clearer, below in conjunction with accompanying drawing, embodiments of the present invention are described in further detail.In figure, same or analogous member uses the same reference numerals to represent.
Fig. 1 shows the first embodiment of solar selectively absorbing coating of the present invention, referring to Fig. 1, solar selectively absorbing coating comprises: metallic reflector 1 and be formed on the semiconductor absorption layer 2 on metallic reflector 1, and metallic reflector 1 is Al, semiconductor absorption layer 2 is Ge.In Fig. 1, the basic physical function cell cube that semiconductor absorption layer 2 and Al metallic reflector 1 are coating for selective absorption, and other cell cubes are and realize the required cell cube of high low-temperature circulating long-time stability.The film thickness of Ge semiconductor absorption layer 2 is roughly 0.1-5um, can adopt the method for manufacturing thin film such as plating/CVD/ evaporation/sputter to obtain; The thickness of Al metallic reflector 1 is that 10-1000nm can adopt by preparation methods such as sputter, plating, evaporation, chemical plating, silver mirror reaction and obtains; Buffer layer thin film can adopt plating/CVD/ evaporation to wait method for manufacturing thin film to obtain.
In order to guarantee the Stability and dependability of coating for selective absorption, can add targetedly the film layer structures such as adhesion layer 4, infrared transparent oxide skin(coating) 3, anti-oxidation protection layer 5.The low problem of absorption coefficient high in order to improve semiconductor dielectric constant, boundary reflection causes greatly, can be arranged to semiconductor absorption layer surface micro-rough matte, as shown in Figure 1.
Between metallic reflector 1 and semiconductor absorption layer 2, be provided with infrared transparent oxide skin(coating) 3.Infrared transparent oxide skin(coating) can be selected Cr 2o 3, Al 2o 3or TiO 2deng material.Can when the Al of splash-proofing sputtering metal reflecting layer, put into partial oxidation, oxygen and this metallic reflector surface reaction, form one deck Al 2o 3infrared transparent oxide skin(coating) 3, the object of this infrared transparent oxide skin(coating) is the reduction problem of the selective absorption function that brings for fear of semiconductor absorption layer 1 and metallic reflector 2 inter-diffusion reaction.
Metallic reflector 1 below is provided with adhesion layer 4, and the object of adhesion layer 4 is in order to guarantee the stability of selective absorption film in high during low temperature cycling was, can select to add oxide, the Cr of Ni/Ti 2o 3with and composition thereof wait material.Adhesion layer can adopt plating/CVD/ evaporation to wait method for manufacturing thin film to obtain.
Semiconductor absorption layer 2 surfaces are micro-rough matte.In order to improve because semiconductor dielectric constant is high, the low problem of absorption coefficient that boundary reflection causes greatly, can utilize semiconductor anisotropic etching to form matte micro-rough matte and will form light trapping, reduce the reflectivity of Ge semiconductor surface, micro-rough matte can adopt H 2o 2etching obtains.
Micro-rough matte surface applies anti-oxidation protection layer 5, at suede facing surface, introduces the high-temperature oxydation that anti-oxidant unit usually prevents film, improves high-temperature stability and the reliability of composite layer.
Fig. 2 shows the second embodiment of solar selectively absorbing coating of the present invention, and the difference of this embodiment and the first embodiment is, Ge semiconductor absorption layer 2 surfaces are planar structure, on Ge semiconductor absorption layer surface, are provided with two-layer anti-reflection film 6.The effect of anti-reflection film 6 is in order to reduce because semiconductor dielectric constant is high, the low problem of absorption coefficient that boundary reflection causes greatly, and anti-reflection film can adopt the method for CVD by regulating N 2o/NH 3ratio obtain Si 3n 4-SiO 2+ Si 3n 4-SiO 2series antireflective coating.
In addition, on anti-reflection film 6 surfaces, apply anti-oxidation protection layer 5, on selectively absorbing layers 2 surfaces, introduce anti-oxidant element, as SiO 2, prevent the high-temperature oxydation of film, improve high-temperature stability and the reliability of composite layer.
The coating for selective absorption of the first embodiment and the second embodiment, preferably, should be coated on the surface of best bright finish, as glass or metal, can first carry out polishing to metallic substrates, guarantees its planarization, to guarantee stability and the reliability of selective pad pasting.
Referring to Fig. 3, show solar selective coat of the present invention and be coated in solar water heater and non-selectivity coating and the operating temperature of traditional selective coating water heater and the relation of efficiency, as seen from the figure, when radiation loss accounts for 60% of total losses, the operating efficiency of water heater is 0.6 o'clock, the operating temperature of the solar water heater of non-selectivity coating can reach 35 ℃ of left and right, the operating temperature with the solar water heater of selective coating can reach 100 ℃ of left and right, and adopt the new selective solar water heater of structure of the present invention can reach the operating temperature of 280 ℃.Novel coating for selective absorption has been broken the low limitation of existing coating for selective absorption operating temperature, solved because the wider high temperature causing of conventional three-dimensional nanometer coating for selective absorption transition region is applied limited defect, substituted the selective absorbing material of conventional three-dimensional nanometer, effectively brought into play semiconductor energy gap cut-off suddenly and the little advantage of good metal low infrared emissivity negative effect is absorbed to more multipotency the effectively loss of reduction infrared emanation.Be widely used in (heat generating system, solar water heater system, solar air-conditioner system etc.) in photo-thermal system, greatly reduce the thermal radiation loss of system, thereby improve the efficiency of system; Be applied to can make operating temperature improve 2-3 doubly in solar water heater system; Be applied to can make system effectiveness improve 5-6% left and right in solar heat power generation system.
Although pass through with reference to some of the preferred embodiment of the invention, the present invention is illustrated and described, but those of ordinary skill in the art should be understood that and can do various changes to it in the form and details, and without departing from the spirit and scope of the present invention.

Claims (10)

1. a solar selectively absorbing coating, is characterized in that, comprises metallic reflector and is formed on the semiconductor absorption layer on described metallic reflector, and described metallic reflector is Al, and semiconductor absorption layer is Ge.
2. solar selectively absorbing coating according to claim 1, is characterized in that, is provided with infrared transparent oxide skin(coating) between described metallic reflector and semiconductor absorption layer.
3. solar selectively absorbing coating according to claim 2, is characterized in that, described infrared transparent oxide skin(coating) is Cr 2o 3, Al 2o 3or TiO 2.
4. solar selectively absorbing coating according to claim 2, is characterized in that, described metallic reflector below is provided with adhesion layer, and described adhesion layer is Ni, Ti or Cr 2o 3.
5. solar selectively absorbing coating according to claim 4, is characterized in that, described semiconductor absorption layer surface is micro-rough matte.
6. solar selectively absorbing coating according to claim 5, is characterized in that, described micro-rough matte surface applies anti-oxidation protection layer.
7. solar selectively absorbing coating according to claim 4, is characterized in that, described semiconductor absorption layer surface is provided with 1～3 layer of anti-reflection film.
8. solar selectively absorbing coating according to claim 7, is characterized in that, described 2 layers of anti-reflection film cover conductor absorbed layer surface successively, and described anti-reflection film is Si 3n 4, SiO 2+ SiN 4.
9. solar selectively absorbing coating according to claim 7, is characterized in that, described anti-reflection film surface applies anti-oxidation protection layer, and described anti-oxidation protection layer is SiO 2.
10. according to the solar selectively absorbing coating described in claim 1 to 9 any one, it is characterized in that, described coating for selective absorption is coated on the surface of best bright finish.
CN201210279294.7A 2012-08-07 2012-08-07 Solar selective absorbing coating Withdrawn CN103574948A (en)

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104976803A (en) * 2014-04-11 2015-10-14 太浩科技有限公司 Solar spectrum selective absorbing coating and preparation method thereof
CN104976802A (en) * 2014-04-11 2015-10-14 太浩科技有限公司 Solar spectrum selective absorptive coating and manufacturing method thereof
CN105506554A (en) * 2015-12-29 2016-04-20 电子科技大学 Visible light/infrared band nano-optical absorbing coating and preparation method thereof

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104976803A (en) * 2014-04-11 2015-10-14 太浩科技有限公司 Solar spectrum selective absorbing coating and preparation method thereof
CN104976802A (en) * 2014-04-11 2015-10-14 太浩科技有限公司 Solar spectrum selective absorptive coating and manufacturing method thereof
CN105506554A (en) * 2015-12-29 2016-04-20 电子科技大学 Visible light/infrared band nano-optical absorbing coating and preparation method thereof

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Application publication date: 20140212