JP5421665B2 - Solar heat converter - Google Patents

Description

  The present invention relates to a solar heat-to-heat converter that receives sunlight and converts it into thermal energy, and in particular, a first layer that transmits light having a wavelength shorter than a predetermined wavelength and reflects light having a wavelength longer than a predetermined wavelength. And a second layer that rises in temperature by absorbing light transmitted through the first layer, and a heat medium that circulates between the first layer and the second layer. The present invention relates to one that heats a heat medium by heat transfer from two layers and converts it into heat energy.

  2. Description of the Related Art Conventionally, technologies such as a solar water heater have been disclosed as those that convert solar energy into heat energy. This solar water heater warms water by solar heat, and can use the received solar energy by converting it into thermal energy. For example, solar hot water as shown in FIG. A vessel is disclosed.

  Such a solar water heater is configured such that a heat collecting tube is housed inside a glass tube via a vacuum heat insulating layer, and a plurality of hot water storage cylinders are formed by inserting water injection tubes inside the heat collecting tube. Since the vacuum heat insulating layer is provided, heat conduction between the glass tube and the heat collecting tube and heat loss due to convection can be prevented, and sunlight can be converted into heat energy with high efficiency.

JP-A-6-249521

  However, in the solar water heater as described above, although heat loss due to heat conduction and convection from the heat collecting tube can be reduced, heat radiation from the heated heat collecting tube through the glass tube is blocked. However, there is a problem that the heat energy conversion efficiency is reduced by the amount of heat loss caused by the heat radiation.

  The present invention has been made to solve the above-described problems.

The invention according to claim 1 is a solar radiation heat conversion device formed in a layer shape that receives sunlight and converts it into heat energy, the first layer receiving the sunlight from one side, and the first layer The first layer transmits light having a wavelength shorter than a predetermined wavelength and reflects light having a wavelength longer than the predetermined wavelength, and the predetermined wavelength is set to an arbitrary wavelength within a range of 1500 nm to 2500 nm. A second layer that is provided on the side of the first layer opposite to the side that receives the sunlight, absorbs the light transmitted through the first layer, and raises the temperature . The layer absorbs light having a wavelength shorter than the predetermined wavelength and reflects light having a wavelength longer than the predetermined wavelength . The layer circulates between the first layer and the second layer and rises. Heated by heat transfer from the heated second layer A sunlight heat conversion apparatus and a medium.

  The invention according to claim 2 is the solar light heat conversion device according to claim 1, wherein the first layer is a multilayer film in which thin films having a high refractive index and thin films having a low refractive index are alternately laminated. .

The invention according to claim 3 is the solar light heat conversion device according to claim 1 or 2, wherein the second layer is on a side opposite to the side receiving the solar light and spaced apart from the second layer. provided, in which and a third reflective layer in at least the second layer or al the emitted wavelength range of heat radiation from the second layer.

  The invention according to claim 4 is the solar light heat conversion device according to claim 3, wherein the space between the second layer and the third layer is a vacuum space, or heat from the second layer. Either a heat insulating member that transmits radiation and has lower thermal conductivity than the second layer and the third layer is interposed.

  According to the solar heat-conversion device according to claim 1, the first layer that receives the solar light from one surface side, and the first layer transmit light having a wavelength shorter than a predetermined wavelength, Reflects light having a wavelength greater than or equal to the predetermined wavelength, and is provided on the side of the first layer opposite to the side that receives the sunlight. The temperature of the first layer is increased by absorbing the light transmitted through the first layer. Since it comprises a second layer, a heat medium that flows between the first layer and the second layer, and is heated by heat transfer from the second layer that has been heated, The heat medium can be heated by the second layer that has been heated by absorbing light having a wavelength shorter than a predetermined wavelength among the sun rays, and among the heat radiation from the second layer that has been heated, It is possible to reflect and radiate more than a predetermined wavelength emitted to the first layer side and return to the second layer, Suppressing heat loss due to thermal radiation from the second layer can convert solar radiation into heat efficiently energy.

  According to the invention described in claim 2, in addition to the effect of the solar light heat conversion device according to claim 1, the first layer is formed by alternately laminating a thin film having a high refractive index and a thin film having a low refractive index. Because it is a multilayer film, it transmits sunlight with a wavelength shorter than a predetermined wavelength, and efficiently reflects heat radiation of a predetermined wavelength or more emitted from the second layer to return to the second layer. It is possible to further reduce heat loss due to heat radiation from the second layer.

  According to the invention described in claim 3, in addition to the effect of the solar light heat conversion device according to claim 1 or 2, the second layer is a side opposite to the side receiving the solar light, and the second layer The temperature is raised because it includes a third layer that is spaced apart from the layer and reflects heat radiation from the second layer at least in the wavelength region radiated from the second layer 4. Of the heat radiation from the second layer, the radiation radiated to the third layer side can be reflected and returned to the second layer, and the heat loss due to the heat radiation from the second layer can be further reduced. Further reduction can be achieved.

  According to the invention described in claim 4, in addition to the effect of the solar light heat conversion device described in claim 3, the space between the second layer and the third layer is a vacuum space, or the Since the heat radiation from the second layer is transmitted and a heat insulating member having a lower thermal conductivity than the second layer and the third layer is interposed, the second layer In the heat transfer from the first layer to the third layer, heat transfer other than heat radiation, that is, heat transfer by heat conduction and convection can be suppressed, and heat loss from the second layer can be further reduced. it can.

1 is a schematic cross-sectional view showing a solar heat conversion apparatus according to a first embodiment of the present invention. It is the schematic sectional drawing which expanded and showed the 1st layer vicinity of FIG. It is the schematic which showed the radiation intensity curve (those normalized with the maximum value) with respect to wavelength (lambda) of a black body, and made radiation temperature a parameter. It is the schematic which expanded and showed a part of FIG. It is the schematic sectional drawing which showed the solar-beam heat conversion apparatus which concerns on the 2nd Example of this invention. FIG. 6 is a schematic cross-sectional view showing a modified example of FIG. 5. It is the figure which showed the transmittance | permeability and reflectance with respect to wavelength (lambda) of the 1st layer of FIG.1, FIG.2, FIG.5 and FIG.

  A first embodiment of the present invention will be described with reference to FIGS. In FIG. 1, A has shown the solar beam heat conversion apparatus, and the solar beam heat conversion apparatus A receives sunlight and converts it into heat energy, and roughly shows the first layer 2 and the second layer. Layer 4 and the heat medium 3.

As shown in FIG. 1, the first layer 2 receives the sunlight Y from one surface side, transmits a light beam having a wavelength shorter than the predetermined wavelength λ ₀ as transmitted light Y1, and has a predetermined wavelength λ _0. The above light beam is reflected as reflected light Y2, and is formed of, for example, a multilayer film 20 as shown in FIG. In FIG. 1 and FIGS. 5 and 6 to be described later, the sun rays Y are actually incident on the first layer 2 perpendicularly, but the relationship between the transmitted light Y1 and the reflected light Y2 is more easily understood. For the sake of convenience, the incidence of sunlight Y is shown obliquely with respect to the first layer 2.

  Here, the multilayer film 20 (2) will be described in detail. The multilayer film 20 (2) includes a thin film having a high refractive index and a thin film having a low refractive index (in FIG. 2, a1, a2,..., Am are low). (B1, b2,..., Bm are high-refractive index thin films), which are alternately laminated, such as sputtering vapor deposition, electron beam vapor deposition, and vacuum vapor deposition. It is formed using the well-known method.

The low refractive index thin films a1, a2,..., Am and the high refractive index thin films b1, b2,..., Bm include, for example, silicon dioxide (SiO ₂ ), silicon oxide (SiO), Magnesium fluoride (MgF ₂ ), titanium dioxide (TiO ₂ ), tantalum pentoxide (Ta ₂ O ₅ ), niobium pentoxide (Nb ₂ O ₅ ), zirconium oxide (ZrO ₂ ), hafnium oxide (HfO ₂ ), oxidation Magnesium (MgO), aluminum oxide (Al ₂ O ₃ ), aluminum (Al), gold (Au), silver (Ag), copper (Cu), silicon (Si), germanium (Ge), carbon (C), etc. Among these, those having relatively high refractive index and low refractive index are selected and used in combination.

Here, the optical thicknesses of the low refractive index thin films a1, a2,..., Am and the high refractive index thin films b1, b2,..., Bm are (2n−1) la λ _i / 4 (λ _i is The design center wavelength of visible light to be reflected, n is a natural number), but is preferably λ _i / 4 (n = 1) in order to obtain the same reflection effect with a thinner film thickness.

  1 and 2, reference numeral 1 denotes a structure. The structure 1 is a substrate of the multilayer film 20 when the first layer 2 is the multilayer film 20 as described above. Materials that are optically transparent at least in the near-ultraviolet to mid-infrared region (having a wavelength region of 200 nm to 4 μm that occupies most of the sunlight Y), such as heat resistant glass, quartz, sapphire, etc. Made of material.

The second layer 4 is provided on the side of the first layer 2 opposite to the side that receives the sunlight Y, and the light transmitted through the first layer 2 (transmitted light Y1) (this transmitted light Y1 is described later). And the like, as long as it absorbs light having a wavelength shorter than the predetermined wavelength λ _0. For example, graphite (C), silicon ( Si), germanium (Ge), and the like can be formed, but in order to suppress the radiation from the second layer 4 while absorbing the sunlight Y, from the predetermined wavelength λ ₀ that is most of the sunlight Y. It is preferable that it absorbs light having a short wavelength (for example, light having a wavelength of 200 nm to 1700 nm) and reflects light having a longer wavelength (for example, light having a wavelength of 2000 nm to 20000 nm).

  The heat medium 3 circulates between the first layer 2 and the second layer 4 and is heated by heat transfer (mainly heat conduction) from the second layer 4 that has raised the temperature by absorbing the transmitted light Y1. Any material may be used as long as it can store heat and is transparent to the extent that it can optically transmit the transmitted light Y1 and has fluidity. For example, water, ethylene glycol, etc. Used.

  The circulation of the heat medium 3 is performed by a circulation means such as a pump (not shown). When the heat medium 3 becomes a high temperature steam by the heating by the second layer 4, for example, the high temperature steam is used. When the turbine generator is driven by the above, or when it becomes a high-temperature liquid, it can be used as a heat source such as hot water supply or heating.

  Next, the effect of the solar-beam heat conversion apparatus A which concerns on the 1st Example comprised as mentioned above is demonstrated with reference to FIGS. First, as shown in FIG. 1, the sunlight Y incident on the solar heat conversion apparatus A passes through the structure 1, part of which passes through the first layer 2 as transmitted light Y1, and the remaining part The reflected light Y2 is reflected by the first layer 2.

Here, the operation of the first layer 2 will be described with reference to FIG. 2, taking as an example the low refractive index thin film a1 having an optical film thickness of λ _i / 4 sandwiched between the high refractive index thin films b1 and b2. At the interface c between the high refractive index thin film b1 positioned on the upper side and the low refractive index thin film a1 positioned on the lower side, the phase of the reflected light beam does not change, but the lower refractive index thin film a1 positioned on the upper side and the lower At the interface d with the high-refractive-index thin film b2 located on the side, the phase of the reflected light beam is reversed, and when the sun rays Y are perpendicularly incident on the first layer 2, the interface Since the optical path difference between the light beams reflected by c and interface d differs by λ _i / 2 (= (λ _i / 4) × 2), the light beams reflected by interface c and interface d are in phase and strengthened. Accordingly, the reflected light Y2 having a specific wavelength λ _i is generated.

Therefore, the low refractive index thin films a1, a2,..., Am and the high refractive index thin films b1, b2,. It is possible to reflect a light beam having a wavelength λ ₀ or more as reflected light Y2 while transmitting a light beam having a wavelength shorter than the wavelength λ ₀ ) as transmitted light Y1.

In FIG. 7, the predetermined wavelength λ ₀ is set to about 2000 μm, the low refractive index thin films a 1, a 2,..., Am are made of silicon dioxide (SiO ₂ ), and the high refractive index thin films b 1, b 2,. The characteristics of the reflectance and transmittance with respect to the wavelength λ of the multilayer film 20 formed using niobium pentoxide (Nb ₂ O ₅ ) as bm are illustrated.

The transmitted light Y1 transmitted through the first layer 2 is transmitted through the heat medium 3 and absorbed by the second layer 4, and the second layer 4 is thermally excited by absorption of the transmitted light Y1. The temperature of the second layer 4 thus raised causes heat transfer (mainly heat conduction) to the heat medium 3 and generates heat radiation (radiated light). Then, this radiated light is transmitted again through the heat medium 3, and in the first layer 2, reflection occurs with respect to light having a predetermined wavelength λ ₀ or more by the same action as the generation of the reflected light Y 2 described above. To the second layer 4.

  3 and 4 show a radiation intensity curve (normalized by the maximum value) with respect to the wavelength λ of the black body. Here, the radiation intensity curve of 6000 K approximates the sunlight Y. The radiation intensity curves at 100 ° C. and 300 ° C. exemplify the thermal radiation from the assumed second layer 4, but the actual radiation intensity curve from the second layer 4 is the second It depends on the emissivity and temperature of the layer 4, and these are the physical properties such as the specific heat and surface state of the material constituting the second layer 4, the heat transfer rate from the second layer 4 to the heat medium 3, the surroundings Varies with temperature.

The predetermined wavelength λ ₀ is preferably set to an arbitrary wavelength within the range shown in FIG. 4, that is, the range of 1500 nm to 2500 nm. This is because, as shown in FIG. 4, in the first layer 2, a light ray having a long wavelength and a temperature lower than that of the sunlight ray Y is transmitted while transmitting the sunlight ray Y containing many rays having a short wavelength at a high temperature. This is to reflect the radiation light from the second layer 4 containing a large amount of light and suppress the heat loss due to the thermal radiation from the second layer 4 to efficiently convert the solar rays Y into thermal energy.

  Next, a second embodiment of the present invention will be described with reference to FIG. The same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. In this embodiment, a third layer 6 is further provided in addition to the configuration of the solar light heat conversion apparatus A of the first embodiment.

  As shown in FIG. 5, the third layer 6 is provided on the side opposite to the side of the second layer 4 that receives the sunlight Y, and is spaced 5 from the second layer 4. The thermal radiation from the second layer 4 is reflected at least in the wavelength region radiated from the second layer 4, for example, a metal such as aluminum (Al), silver (Ag), gold (Au), etc. The surface is polished and processed to be flat, or these metals are deposited on a flat substrate by a known vapor deposition method.

  Next, the effect of the solar-beam heat conversion apparatus A which concerns on the 2nd Example comprised as mentioned above is demonstrated with reference to FIG. In addition, since the effect to the solar ray Y based on the structure of the structure 1, the 1st layer 2, the heat medium 3, and the 2nd layer 4 is the same as the thing of a 1st Example, the detailed description Is omitted.

  In this example, similarly to the first example, the second layer 4 rises in temperature by absorbing the transmitted light Y1 transmitted through the first layer 2, and the raised second layer 4 It generates thermal radiation (radiated light) from

  And this thermal radiation is divided roughly into the thing which goes to the 2nd layer 4 side, and the thing which goes to the 3rd layer 6 side. Of the thermal radiation from the 2nd layer 4, 3rd Paying attention to the layer 6 side, the emitted light is reflected by the third layer 6 as reflected light Y4 and returns to the second layer 4, and the heat radiation from the second layer 4 and the third layer 6 are reflected. The return of the reflected light Y4 from the layer 6 is repeated, and as a result, the radiated light is confined and heat loss due to thermal radiation can be further reduced.

  By the way, in the above-described example, the space 5 may be filled with air, for example, but the space 5 between the second layer 4 and the third layer 6 is a vacuum space or FIG. As shown in FIG. 5, the heat insulating member 5 ′ (for example, heat resistant glass) that transmits heat radiation (radiated light) from the second layer 4 and has lower thermal conductivity than the second layer 4 and the third layer 6 is used. , Quartz, sapphire, etc.) are preferably interposed. This is in the heat transfer from the second layer 4 to the third layer 6, and heat transfer other than heat radiation, that is, heat transfer by heat conduction and convection can be suppressed. This is because the heat loss can be further reduced.

A Sunlight heat conversion device Y Sunbeam 2 First layer 3 Heat medium 4 Second layer 5 Between 6 Third layer

Claims (4)

It is a solar radiation heat conversion device formed into a layer that receives sunlight and converts it into heat energy,
A first layer that accepts the sunlight from one side;
The first layer transmits a light beam having a wavelength shorter than a predetermined wavelength and reflects a light beam having the predetermined wavelength or more.
The predetermined wavelength is set to an arbitrary wavelength within a range of 1500 nm to 2500 nm,
A second layer provided on the opposite side of the first layer to the side that receives the sunlight, and absorbing light rays transmitted through the first layer to raise the temperature;
The second layer absorbs light having a wavelength shorter than the predetermined wavelength and reflects light having a wavelength longer than the predetermined wavelength.
The solar radiation heat | fever characterized by including the heat medium which distribute | circulates between the said 1st layer and the said 2nd layer, and is heated by the heat transfer from the said 2nd layer heated up Conversion device. The solar radiation heat conversion apparatus according to claim 1, wherein the first layer is a multilayer film in which a thin film having a high refractive index and a thin film having a low refractive index are alternately stacked. And the second layer a layer comprising at the side for receiving sunlight opposite side of the second provided apart between the thermal radiation at least the second layer or et radiation from the second layer The solar radiation heat conversion apparatus according to claim 1, further comprising: a third layer that reflects in a wavelength region to be reflected. The space between the second layer and the third layer is a vacuum space or transmits heat radiation from the second layer and conducts heat more than the second layer and the third layer. The solar radiation heat conversion device according to claim 3, wherein a heat insulating member having a low rate is interposed.

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