The present invention relates to a heat conversion member and to a heat conversion laminate.
Photovoltaic power generation systems are known that convert sunlight to heat and utilize the heat for electric power generation. In the known systems, sunlight is collected with a collector and the collected sunlight is used to heat a heating medium (such as oil, dissolved salts or molten sodium) in a container or flow channel. Provision of covering materials, thin-films and the like on the surfaces of containers or flow channels is also being studied as a way of accelerating heating of the heating medium by the collected sunlight.
For example, PTL 1 proposes a cermet layer (ceramic+metal=cermet) as a member for conversion of sunlight to heat. Also, PTL 2, for example, proposes a solar energy collecting device having one section that receives the action of sunlight rays and another section that is situated at a gap from that section away from sunlight rays and receives the action of a heat absorption medium, and a section situated between the two sections, wherein the absorbing element is made of a covered sheet material, the sheet material having a sunlight ray-selective coating on one side of the sheet facing the section that receives the action of sunlight rays, and having a radiative coating on the other side of the sheet that faces the section that receives the action of the heat absorption medium.
At the current time, it is desirable to accelerate heating of heating media by collected sunlight and achieve more efficient light-to-heat conversion.
It is an object of the present invention to provide a heat conversion member that can efficiently convert light to heat. It is another object of the present invention to provide a heat conversion laminate comprising a heat conversion member that can efficiently convert light to heat.
The means for achieving these objects is described by the following (1) to (10).
(1) A heat conversion member comprising at least one type of semiconductor,
the band gap of the semiconductor being between 0.5 eV and 1.2 eV.
(2) A heat conversion member comprising a composite material of at least one type of semiconductor and a transparent dielectric material,
the band gap of the semiconductor being between 0.5 eV and 1.2 eV.
(3) The heat conversion member according to (1) or (2) above, wherein the semiconductor comprises FeS2.
(4) The heat conversion member according to (1) or (2) above, wherein the semiconductor comprises Mg2Si.
(5) The heat conversion member according to (1) or (2) above, wherein the semiconductor comprises Zn3As2.
(6) The heat conversion member according to (1) or (2) above, wherein the semiconductor comprises Ge.
(7) The heat conversion member according to any one of (1) to (6) above, which has a film shape.
(8) The heat conversion member according to (7), wherein the film shape has a thickness of 1 nm to 10 μm.
(9) A heat conversion laminate having laminated at least one or more layers including the heat conversion member according to (7) or (8), and a metal layer.
(10) A heat conversion laminate having laminated at least a metal layer, one or more layers including the heat conversion member according to (7) or (8), and a transparent dielectric layer, in that order.
According to the present invention, there is provided a heat conversion member that can efficiently convert light to heat. According to the present invention, there is further provided a heat conversion laminate comprising a heat conversion member that can efficiently convert light to heat.
The heat conversion member of the present invention is a heat conversion member comprising at least one type of semiconductor, wherein the band gap of the semiconductor is between 0.5 eV and 1.2 eV. The heat conversion member of the present invention is also a heat conversion member comprising a composite material of one or more types of semiconductor and a transparent dielectric material, wherein the band gap of the semiconductor is between 0.5 eV and 1.2 eV.
The one or more semiconductors in the heat conversion member of the present invention may be of a single type of semiconductor, or a mixture of two or more different types of semiconductor.
The semiconductor in the heat conversion member of the present invention is not particularly restricted, and examples include FeS2, Mg2Si, Zn2As2 and Ge.
The band gap of the one or more types of semiconductor in the heat conversion member of the present invention is between 0.5 eV and 1.2 eV and preferably between 0.7 eV and 1.0 eV.
The transparent dielectric material in the composite material in the heat conversion member of the present invention (hereunder simple referred to as “composite material”) is not particularly restricted, and examples include SiO2, Al2O2 and AlN, with SiO2 being preferred.
The one or more types of semiconductor in the heat conversion member of the present invention preferably include FeS2, Mg2Si, Zn2As2 or Ge. The values of the band gaps of FeS2, Mg2Si, Zn2As2 and Ge vary depending on the measuring method and measuring conditions, however generally speaking the value of the FeS2 band gap is 0.95 eV, the value of the Mg2Si band gap is 0.77 eV, the value of the Zn2As2 band gap is 0.86 eV and the value of the Ge band gap is 0.89 eV. The one or more types of semiconductor in the heat conversion member of the present invention may also be a mixture of at least two different compounds selected from the group consisting of FeS2, Mg2Si, Zn2As2 and Ge. The band gap can be measured by a photoabsorption method or photoelectron spectroscopy.
The heat conversion member of the present invention may be in any desired form, such as in the form of a film shape, tube shape, sheet shape or the like, however a film shape is preferred. The thickness of a film of the heat conversion member of the present invention may be any desired thickness so long as the effect of the present invention is exhibited; however, preferably a film of the heat conversion member of the present invention has a thickness of 1 nm to 10 μm, and more preferably it has a thickness of 5 nm to 100 nm.
The content of the one or more semiconductors in the heat conversion member of the present invention may be as desired, and for example, it may be 10 vol % or greater, 20 vol % or greater, 30 vol % or greater, 40 vol % or greater, 50 vol % or greater, 60 vol % or greater, 70 vol % or greater, 80 vol % or greater, 90 vol % or greater or 95 vol % or greater.
The heat conversion member of the present invention may also essentially consist entirely of the one or more semiconductors, in which case the content of the one or more semiconductors will be 100 vol %.
The heat conversion member of the present invention may also contain any desired material other than the one or more semiconductors. The heat conversion member of the present invention may yet also contain any desired material other than a composite material of the one or more semiconductors and a transparent dielectric material.
The heat conversion member of the present invention can be obtained by any desired publicly known production method. For example, the heat conversion member of the present invention can be produced by physical vapor phase deposition (PVD), sputtering or the like.
As one feature, the heat conversion laminate of the present invention has laminated one or more layers comprising a film-like heat conversion member of the present invention, and a metal layer, and it may have a metal layer and one or more layers comprising a film-like heat conversion member of the present invention laminated in that order, or the lamination may be in the reverse order.
As another feature, the heat conversion laminate of the present invention also have at least a metal layer, one or more layers comprising a film-like heat conversion member of the present invention and a transparent dielectric layer, laminated in that order.
The one or more layers comprising a film-like heat conversion member of the present invention in the heat conversion laminate of the present invention may be constructed as a photoabsorbing layer, and because it has a steep change between absorption and non-absorption in a sunlight wavelength range of 2480 nm to 1000 nm, it can efficiently absorb sunlight while minimizing heat release by heat radiation from the heating medium at 200° C. to 600° C., thereby efficiently convert light to heat. The thickness of the one or more layers comprising a film-like heat conversion member in the heat conversion laminate of the present invention may be any desired thickness so long as the effect of the present invention is exhibited, and it is preferably a thickness of 5 nm to 100 nm. The layer comprising the film-like heat conversion member in the heat conversion laminate of the present invention may be a single layer or multiple layers. The one or more layers comprising a film-like heat conversion member in the heat conversion laminate of the present invention may also include any materials other than the film-like heat conversion member.
The metal layer in the heat conversion laminate of the present invention may be constructed as an infrared anti-reflection layer. The metal layer in the heat conversion laminate of the present invention is not particularly restricted, and for example, it may be a molybdenum (Mo) layer, tungsten (W) layer, silver (Ag) layer, gold (Au) layer, copper (Cu) layer or the like, and is preferably a molybdenum (Mo) layer. The thickness of the metal layer in the heat conversion laminate of the present invention may be any desired thickness so long as the effect of the present invention is exhibited, and it is preferably a thickness of 100 nm or greater.
The transparent dielectric layer in the heat conversion laminate of the present invention may also be constructed as an anti-reflection layer. The transparent dielectric layer in the heat conversion laminate of the present invention is not particularly restricted, and examples include a SiO2 layer, Al2O3, AlN layer or the like, with a SiO2 layer being preferred. The thickness of the transparent dielectric layer in the heat conversion laminate of the present invention may be any desired thickness so long as the effect of the present invention is exhibited, and it is preferably a thickness of 10 nm to 500 nm.
The heat conversion laminate of the present invention can be obtained by any desired publicly known production method. For example, the heat conversion laminate of the present invention can be produced by physical vapor phase deposition (PVD), sputtering or the like.
The heat conversion laminate of the present invention will now be explained in greater detail with reference to
Examples will now be provided for a more concrete explanation of the present invention. The present invention is not limited to these examples, however, provided that the object and gist of the present invention are maintained.
The reproducibility of the film properties according to Bruggeman's effective medium approximation was verified by Example 1 and Comparative Example 1.
The absorption properties of a Mo—SiO2 cermet monolayer film were determined using Bruggeman's theory of computation. The term “cermet” means “ceramic+metal”.
The optical constants (n, k) of the Mo—SiO2 cermet monolayer film were calculated by Bruggeman's effective medium approximation formula (formula (1) below). The optical constants for Mo and SiO2 in the Mo—SiO2 cermet were obtained by forming a monolayer film of each component by sputtering, and performing calculation from the measurement data obtained using a spectroscopic ellipsometer, and the reflectance property and the transmittance property as measured with a spectrophotometer.
A multilayer film approximation based on the optical constants (n, k) for Mo—SiO2 cermet obtained by calculation based on formula (1) was used to calculate the absorbance of the Mo—SiO2 cermet monolayer film (corresponding to a film thickness of 30 nm). The results for the absorption properties of a Mo—SiO2 cermet monolayer film (calculated) are shown in
The absorption properties of a Mo—SiO2 cermet monolayer film were determined using an actual film (prepared film).
A film was formed by simultaneous sputtering of Mo and SiO2 on a quartz substrate that had been heated to a temperature of 500° C. to 600° C., to obtain a sample of a Mo—SiO2 cermet monolayer film. The optical constants (refractive index n, extinction coefficient k) of the Mo—SiO2 cermet were calculated for the obtained sample from the measurement data with a spectroscopic ellipsometer and the reflectance property and transmittance property measured with a spectrophotometer.
The calculated multilayer film approximation based on the optical constants (n, k) for Mo—SiO2 cermet was used to calculate the absorbance of the Mo—SiO2 cermet monolayer film (corresponding to a film thickness of 30 nm). The results for the absorption properties of the Mo—SiO2 cermet monolayer film (an actual film) are shown in
As is clear by referring to
The absorption properties of a heat conversion member were evaluated using Example 2 and Comparative Example 2.
Evaluation of the absorption properties of a heat conversion member of the present invention was conducted using a FeS2—SiO2 cersemi monolayer film, a Mg2Si—SiO2 cersemi monolayer film, a Ge—SiO2 cersemi monolayer film and a Zn2As2—SiO2 cersemi monolayer film. The term “cersemi” means “ceramic+semiconductor”.
The optical constants (n, k) of the FeS2—SiO2 cersemi, Mg2Si—SiO2 cersemi, Ge—SiO2 cersemi and Zn2As2—SiO2 cersemi were calculated by Bruggeman's effective medium approximation formula (formula (2) below). For the optical constants (ns, ks) for FeS2, Ge and Zn2As2, refer to “Handbook of Optical Constants of Solids”, Edward D. Palik, Academic Press, Boston, 1985”, and for the optical constants (ns, ks) of Mg2Si, refer to “T. Kato et al., J. Appl. Phys. 110, 063723(2011)”. Experimental data were used for the optical constants (nc, kc) of SiO2.
Using the multilayer film approximations based on the optical constants (n, k) for FeS2—SiO2 cersemi, Mg2Si—SiO2 cersemi, Ge—SiO2 cersemi and Zn3As2—SiO2 cersemi, obtained by each calculation using formula (2), each absorbance was calculated for the FeS2—SiO2 cersemi monolayer film, Mg2Si—SiO2 cersemi monolayer film, Ge—SiO2 cersemi monolayer film and Zn3As2—SiO2 cersemi monolayer film (corresponding to a film thickness of 30 nm).
The absorption properties of a Mo—SiO2 cermet monolayer film were evaluated.
The optical constant (n, k) of the Mo—SiO2 cermet monolayer film was calculated by Bruggeman's effective medium approximation formula (formula (1) below). The optical constants for Mo and SiO2 in the Mo—SiO2 cermet were obtained by forming a monolayer film of each component by sputtering, and performing calculation from the measurement data obtained using a spectroscopic ellipsometer, and the reflectance property and the transmittance property as measured with a spectrophotometer.
A multilayer film approximation based on the optical constants (n, k) for Mo—SiO2 cermet obtained by calculation based on formula (1) was used to calculate the absorbance of the Mo—SiO2 cermet monolayer film (corresponding to a film thickness of 30 nm). The results for the absorption properties of the Mo—SiO2 cermet monolayer film are shown in
Referring to
Evaluation of the absorption properties of a heat conversion laminate and evaluation of the film efficiency were conducted using Example 3 and Comparative Example 3.
Evaluation of the absorption properties of a heat conversion laminate of the present invention and evaluation of the film efficiency were conducted using a FeS2—SiO2 cersemi laminate. The structure of the FeS2—SiO2 cersemi laminate that operates at a heat collecting temperature of 580° C. was a 4-layer structure comprising a SiO2 layer (film thickness: 70 nm), a cersemi layer with a FeS2 mixing ratio of 30% (film thickness: 70 nm), a cersemi layer with a FeS2 mixing ratio of 100% (film thickness: 15 nm) and a Mo (molybdenum) layer (film thickness: 100 nm) from the light incident side, as shown in
The optical constants (n, k) of the FeS2—SiO2 cersemi layers of the FeS2—SiO2 cersemi laminate that operates at a heat collecting temperature of 580° C. and the FeS2—SiO2 cersemi laminate that operates at a heat collecting temperature of 400° C. were determined by exactly the same calculation method as used for the optical constants (n, k) of Example 2. For the optical constants (n, k) of Mo, refer to “Handbook of Optical Constants of Solids”, Edward D. Palik, Academic Press, Boston, 1985”. Experimental data were used for the optical constants (nc, kc) of SiO2.
The absorbance of the FeS2—SiO2 cersemi laminate that operates at a heat collecting temperature of 580° C. was calculated using multilayer film approximation, based on the optical constants (nc, kc) of the SiO2 layer (film thickness: 70 nm), the optical constants (n, k) of the cersemi layer with a FeS2 mixing ratio of 30% (film thickness: 70 nm), the optical constants (n, k) of the cersemi layer with a FeS2 mixing ratio of 100% (film thickness: 15 nm) and the optical constants (n, k) of the Mo (molybdenum) layer (film thickness: 100 nm). The results for the absorption properties of the FeS2—SiO2 cersemi laminate that operates at a heat collecting temperature of 580° C. are shown in
Similarly, the absorbance of the FeS2—SiO2 cersemi laminate that operates at a heat collecting temperature of 400° C. was calculated using multilayer film approximation, based on the optical constants (nc, kc) of the SiO2 layer (film thickness: 80 nm), the optical constants (n, k) of the cersemi layer with a FeS2 mixing ratio of 30% (film thickness: 75 nm), the optical constants (n, k) of the cersemi layer with a FeS2 mixing ratio of 100% (film thickness: 25 nm) and the optical constants (n, k) of the Mo (molybdenum) layer (film thickness: 100 nm). The results for the absorption properties of the FeS2—SiO2 cersemi laminate that operates at a heat collecting temperature of 400° C. are shown in
Next, the values of the film efficiency η for the FeS2—SiO2 cersemi laminate that operates at a heat collecting temperature of 580° C. and the FeS2—SiO2 cersemi laminate that operates at a heat collecting temperature of 400° C., were determined by formula (3) below. The film efficiency η is an index representing the function of sunlight to heat conversion.
The results for the film efficiency η of the FeS2—SiO2 cersemi laminate that operates at a heat collecting temperature of 580° C. are shown in
The absorption property of a Mo—SiO2 cermet laminate and the film efficiency were evaluated. The structure of a Mo—SiO2 cermet laminate that operates at a heat collecting temperature of 580° C. was a 4-layer structure comprising a SiO2 layer (film thickness: 80 nm), a cermet layer film with a Mo mixing ratio of 40% (film thickness: 40 nm), a cermet layer with a Mo mixing ratio of 50% (film thickness: 25 nm) and a Mo (molybdenum) layer (film thickness: 100 nm), from the light incident side, as shown in
The optical constants (n, k) of the Mo—SiO2 cermet layers of the Mo—SiO2 cermet laminate that operates at a heat collecting temperature of 580° C. and the Mo—SiO2 cermet laminate that operates at a heat collecting temperature of 400° C. were determined by the same calculation method as used for the optical constants (n, k) of Comparative Example 2. For the optical constants (n, k) of Mo, refer to “Handbook of Optical Constants of Solids”, Edward D. Palik, Academic Press, Boston, 1985″. Experimental data were used for the optical constants (nc, kc) of SiO2.
The absorbance of the Mo—SiO2 cermet laminate that operates at a heat collecting temperature of 580° C. was calculated using multilayer film approximation, based on the optical constants (nc, kc) of a SiO2 layer (film thickness: 80 nm), the optical constants (n, k) of a cermet layer with a Mo mixing ratio of 40% (film thickness: 40 nm), the optical constants (n, k) of a cermet layer with a Mo mixing ratio of 50% (film thickness: 25 nm) and the optical constants (n, k) of a Mo (molybdenum) layer (film thickness: 100 nm). The results for the absorption properties of the Mo—SiO2 cermet laminate that operates at a heat collecting temperature of 580° C. are shown in
Similarly, the absorbance of the Mo—SiO2 cermet laminate that operates at a heat collecting temperature of 400° C. was calculated using multilayer film approximation, based on the optical constants (nc, kc) of a SiO2 layer (film thickness: 90 nm), the optical constants (n, k) of a cermet layer with a Mo mixing ratio of 30% (film thickness: 50 nm), the optical constants (n, k) of a cermet layer with a Mo mixing ratio of 50% (film thickness: 50 nm) and the optical constants (n, k) of a Mo (molybdenum) layer (film thickness: 100 nm). The results for the absorption properties of the Mo—SiO2 cermet laminate that operates at a heat collecting temperature of 400° C. are shown in
Next, the values of the film efficiency η for the Mo—SiO2 cermet laminate that operates at a heat collecting temperature of 580° C. and the Mo—SiO2 cermet laminate that operates at a heat collecting temperature of 400° C., were determined by formula (3) below.
The results for the film efficiency η of the Mo—SiO2 cermet laminate that operates at a heat collecting temperature of 580° C. are shown in
Referring to
Number | Date | Country | Kind |
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2012-237314 | Oct 2012 | JP | national |
Filing Document | Filing Date | Country | Kind |
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PCT/JP2013/077251 | 10/7/2013 | WO | 00 |