JP2024121897A - Heat absorption structure and temperature difference power generation device - Google Patents

Abstract

[Problem] To capture thermal energy more efficiently. [Solution] A temperature difference power generation device generates power in response to the temperature difference between a heating section that captures thermal energy used as a high-temperature heat source, and a cooling section through which a fluid used as a low-temperature heat source flows. A heat absorption structure having a heat collection layer made of a fibrous or porous material with a predetermined heat resistance is provided so as to cover at least a portion of the heating section. This technology can be applied, for example, to a temperature difference power generation device used in snow accumulation power generation using snow cold energy. [Selected Figure] Figure 1

Description

This disclosure relates to a heat absorption structure and a temperature difference power generation device, and in particular to a heat absorption structure and a temperature difference power generation device that can capture thermal energy more efficiently.

In recent years, research has been conducted into snow power generation, which uses snow cold energy to cool (as a low-temperature heat source) Stirling engines, which apply heat from the outside of a sealed cylinder and use the expansion and contraction of a gas (working fluid) to move a piston. For example, snow power generation is thought to have a greater advantage than other renewable energy sources in that it places less of a burden on the environment.

Patent Document 1 discloses a Stirling engine in which a heat source cap is provided to cover the heating section, and a heating element is disposed on the inner peripheral surface of the heat source cap. Patent Document 2 discloses a Stirling engine in which a heating element is formed to cover the heat absorption section inside a heat-resistant container, and the heating element is used as a heat source to generate electricity.

JP 2014-98318 A JP 2020-169638 A

However, when using thermal energy from sunlight as a high-temperature heat source for a Stirling engine that generates electricity from snow, the challenge was how to capture the thermal energy from sunlight as efficiently as possible.

This disclosure was made in light of these circumstances, and aims to make it possible to capture thermal energy more efficiently.

The heat absorption structure of one aspect of the present disclosure is provided so as to cover at least a portion of a heating section that takes in thermal energy used as a high-temperature heat source, and includes a heat collection layer made of a fibrous or porous body made of a material with a predetermined heat resistance.

The temperature difference power generation device according to one aspect of the present disclosure includes a heating section that takes in thermal energy used as a high-temperature heat source, a cooling section through which a fluid used as a low-temperature heat source flows, a power generation section that generates power in response to the temperature difference between the heating section and the cooling section, and a heat absorption structure that has a heat collection layer made of a fibrous or porous body made of a material with a predetermined heat resistance and that is provided to cover at least a portion of the heating section.

In one aspect of the present disclosure, the heat collection layer of the heat absorption structure is provided to cover at least a portion of the heating section that takes in thermal energy used as a high-temperature heat source, and is made of a fibrous or porous body made of a material with a predetermined heat resistance.

According to one aspect of the present disclosure, thermal energy can be captured more efficiently.

Note that the effects described here are not necessarily limited to those described herein and may be any of the effects described in this disclosure.

1 is a diagram showing a configuration example of an embodiment of a Stirling engine to which the present technology is applied; 1A to 1C are diagrams illustrating a first configuration example of a heat absorption structure. 11A and 11B are diagrams illustrating a second configuration example of the heat absorption structure. 13A to 13C are diagrams illustrating a third configuration example of the heat absorption structure.

Below, specific embodiments of the present technology will be described in detail with reference to the drawings.

Figure 1 shows an example of the configuration of an embodiment of a Stirling engine, which is an example of a temperature difference power generation device to which the present technology is applied.

The Stirling engine 11 shown in FIG. 1 is configured with at least a power generation section 21, a cooling section 22, and a heating section 23.

The power generation unit 21 incorporates a power generation function that is composed of a piston that moves inside a cylinder by expanding and contracting a sealed gas (such as high-pressure helium gas or air), and magnets and coils that convert the movement of the piston into electricity.

The cooling section 22 is configured with a flow path that, for example, flows in and drains cold water that has been cooled by snow accumulation, and the cold water is used as a low-temperature heat source for the Stirling engine 11. Of course, the cooling section 22 may adopt a water-cooled structure that cools by flowing water, or an air-cooled structure that cools by flowing air, and various fluids can be used as low-temperature heat sources for the Stirling engine 11.

The heating section 23 is configured with fins and the like for taking in thermal energy used as a high-temperature heat source for the Stirling engine 11, and a heat absorbing structure 31 is provided to cover at least a portion of the heating section 23. As shown in Figures 2 to 4 described below, the heat absorbing structure 31 has a heating element 42 used to heat the heating section 23, and a DC or AC power source 32 for supplying power to the heating element 42 is connected to the heat absorbing structure 31.

The Stirling engine 11 configured in this manner can output the electric power generated in the power generation unit 21 according to the temperature difference between the heating unit 23 and the cooling unit 22. At this time, by supplying at least a portion of the electric power output from the Stirling engine 11 to the power source 32, for example, the electric power can be used to assist in initial power generation, thereby improving the power generation efficiency.

The Stirling engine 11 can efficiently capture thermal energy from sunlight using the heat absorption structure 31 as described with reference to Figures 2 to 4, thereby further improving the output power.

With reference to Figure 2, a first configuration example of the heat absorption structure 31 will be described.

As shown in FIG. 2, the heat absorption structure 31 is configured to have a heating element 42 provided to cover the upper end surface 41 of the heating section 23, and a heat collection layer 43 provided to encase the upper end surface 41 and the heating element 42. In the example shown in FIG. 2 (as well as FIG. 3 and FIG. 4 described below), the upper end surface 41 of the heating section 23 is formed in a dome shape that is convex upward, but is not limited to such a shape and may be, for example, a flat shape.

The heating element 42 can be formed, for example, from a nichrome wire wound in a spiral shape to fit the surface shape of the upper end surface 41 of the heating section 23, and generates heat (for example, maintains a temperature of 200° or higher) by power supplied from a power source 32 connected to both ends of the nichrome wire. The heating element 42 can be fixed to the upper end surface 41 by applying a fixing member 44 such as concrete with high thermal conductivity. Note that the heating element 42 is not limited to a nichrome wire wound in a spiral shape, and may be made of a material other than nichrome wire, as long as it can be formed to fit the surface shape of the upper end surface 41.

The heat collection layer 43 is formed in a layered form covering the upper end surface 41 and the heating element 42 with a material (e.g., metal or carbon fiber) that has heat resistance to the extent that it does not melt even when sunlight is collected, and is composed of a fibrous or porous body having a large number of spaces (pores, voids, gaps, or gaps) approximately uniformly arranged at a predetermined ratio inside. For example, it is preferable that the space provided inside the heat collection layer 43 is provided at a ratio of 10% or more to the metal or carbon fiber, etc., so as to suppress the occurrence of thermal convection when the heat collection layer 43 is heated. This ratio may also be adaptively set according to the characteristics of the collecting lens 46 described later. The heat collection layer 43 is also bonded to the fixing member 44 so that heat can be transferred to the upper end surface 41 of the heating unit 23 via the fixing member 44 that fixes the heating element 42.

When sunlight is irradiated onto the heat absorption structure 31 configured in this manner, the thermal energy of the sunlight is accumulated in the heat collection layer 43, and the thermal energy is transferred to the heating unit 23 while passing through the heat collection layer 43. At this time, the heat collection layer 43 is configured to accumulate heat by heating the air in the space provided in the fibrous body or porous body, so that it is possible to prevent heat from escaping due to, for example, reflection, radiation, convection, etc., and to suppress the loss of thermal energy due to sunlight. In addition, the heat absorption structure 31 is configured so that the heat collection layer 43 covers the entire upper end surface 41 of the heating unit 23, thereby preventing the temperature distribution of the heating unit 23 from being biased due to the temperature environment, and avoiding the output of the Stirling engine 11 from becoming unstable.

In this way, by providing the heat absorption structure 31, the Stirling engine 11 can improve the heat absorption efficiency when absorbing thermal energy from sunlight and heating the heating section 23. For example, the Stirling engine 11 has the potential to recover nearly 100% of the solar energy through the heat absorption structure 31 and the heating section 23.

In addition, when the Stirling engine 11 generates electricity by supplying power from the power source 32 to the heating element 42 to heat the heating unit 23, for example, when sunlight is not irradiated sufficiently, at night, or during bad weather, the heat absorption structure 31 provides a heat retention effect that improves power generation efficiency. At this time, the Stirling engine 11 can maintain power generation by using the contraction side of the expansion and contraction in the cylinder of the power generation unit 21 by cooling the cooling unit 22 with cold water cooled by snow accumulation. Therefore, the Stirling engine 11 can continue to generate power even when, for example, power from other renewable energy sources becomes temporarily unstable due to weather changes, and can also provide a power adjustment function.

In addition, when the Stirling engine 11 is exposed to sufficient sunlight, for example, it can generate electricity by using both the expansion and contraction sides of the expansion and contraction in the cylinder of the power generation unit 21, and surplus electricity can be stored in a storage battery, for example.

Furthermore, the Stirling engine 11 can be configured so that the heating element 42, the heat collection layer 43, and the fixing member 44 are black bodies by providing a coating of black fine particles that can absorb light such as sunlight and convert it efficiently into heat on the heating element 42, the heat collection layer 43, and the fixing member 44. Specifically, the heating element 42, the heat collection layer 43, and the fixing member 44 can be black bodies by spraying them with a black body spray that applies paint with an emissivity close to that of a black body to color the surfaces black, thereby increasing the emissivity of the surfaces of the heating element 42, the heat collection layer 43, and the fixing member 44 to, for example, 0.9 or more.

This significantly improves the heat absorption efficiency of the Stirling engine 11, and improves the heat retention effect of the heat collection layer 43. At least these effects can be obtained by making at least one of the heating element 42, the heat collection layer 43, and the fixing member 44 black bodies.

The Stirling engine 11 may be configured so that at least a portion of the power generated by the power generation unit 21 is supplied to the heating element 42, causing the heating element 42 to generate heat, or may be configured so that, for example, the heating element 42 generates heat from power supplied from an external source. The heat absorption structure 31 is not limited to a configuration that covers the entire upper end surface 41 of the heating unit 23, but may be provided so as to cover at least a portion of the heating unit 23, and may be configured so as to transmit thermal energy from sunlight to the heating unit 23.

A second configuration example of the heat absorption structure 31 will be described with reference to FIG. 3. Note that in the heat absorption structure 31A shown in FIG. 3, components common to the heat absorption structure 31 in FIG. 2 are given the same reference numerals, and detailed descriptions thereof will be omitted.

As shown in FIG. 3, the heat absorption structure 31A is configured to have a heating element 42 and a heat collection layer 43, similar to the heat absorption structure 31 in FIG. 2, and is also configured to have a sealed container 45 that houses the heating element 42 and the heat collection layer 43. The sealed container 45 has a sealed structure in which the space housing the heating element 42 and the heat collection layer 43 is sealed by, for example, a transparent member that allows sunlight to pass through.

The heat absorption structure 31A configured in this manner can improve the heat retention effect on the heating section 23 by the air in the space sealed by the sealed container 45. As a result, a further improvement in heat absorption efficiency can be expected in the Stirling engine 11 equipped with the heat absorption structure 31A.

The heat absorption structure 31A can improve the heat retention effect for the heating unit 23 by, for example, filling the airtight container 45 with a gas having a high global warming potential (e.g., carbon dioxide) in addition to air being sealed inside the container 45. Furthermore, the heat absorption structure 31A can improve the heat retention effect for the heating unit 23 by increasing the density of the gas in the space sealed by the container 45 by increasing the airtightness of the container 45 to increase the pressure inside.

For example, when the Stirling engine 11 equipped with the heat absorbing structure 31A is used in an area with a large amount of snowfall, it is preferable to adopt a dome-shaped inclined structure as the sealed container 45 as shown in the figure. As a result, even if snow accumulates on the sealed container 45, the snow will naturally melt due to sunlight and flow off the sealed container 45, so the Stirling engine 11 can always generate power in an environment where a certain amount of sunlight is irradiated. In addition, the Stirling engine 11 can be expected to have an effect of naturally cleaning the surface of the dome-shaped sealed container 45 as the snow that accumulates on it flows off. Note that the shape of the sealed container 45 is not limited to a dome shape as long as it has an inclination that allows the snow to melt and fall due to sunlight, and shapes such as a triangular pyramid or a cone may be adopted.

A third configuration example of the heat absorption structure 31 will be described with reference to FIG. 4. Note that in the heat absorption structure 31B shown in FIG. 4, components common to the heat absorption structure 31 in FIG. 2 are given the same reference numerals, and detailed descriptions thereof will be omitted.

As shown in FIG. 4, the heat absorption structure 31B is configured to have a heating element 42 and a heat collection layer 43, similar to the heat absorption structure 31 in FIG. 2, and in addition, it is configured to have a sealed container 45B that contains the heating element 42 and the heat collection layer 43, and one or more focusing lenses 46.

Similar to the sealed container 45 in FIG. 3, the sealed container 45B is shaped to house the heating element 42 and the heat collecting layer 43, and also has a space for housing the collecting lens 46.

The concentrating lenses 46 concentrate sunlight irradiated onto the heat absorption structure 31B so that it is efficiently converted into thermal energy in the heat collection layer 43. For example, multiple concentrating lenses 46 can be arranged three-dimensionally so that sunlight from various angles is concentrated onto the heat collection layer 43. This allows the concentrating lenses 46 to concentrate sunlight during the day, making it possible to maintain the temperature of the heat absorption structure 31B.

In the example shown in FIG. 4, six condenser lenses 46-1 to 46-6 are provided, but the required number of condenser lenses 46 can be provided depending on the output of the Stirling engine 11. For example, the condensing ability of the condenser lens 46 is proportional to the square of the aperture D, and the condenser lens 46 provided in the heat absorption structure 31B can be designed by setting the amount of heat transfer that the Stirling engine 11 wants to acquire. Even if the condenser lens 46 is not perfectly focused on the heat collection layer 43, the air in the space of the heat collection layer 43 can be heated by the sunlight collected by the condenser lens 46, which can prevent the heating unit 23 from becoming locally hot, and the heat energy can be efficiently collected by the heat collection layer 43.

The heat absorption structure 31B configured in this manner can improve the heat retention effect and heat collection efficiency of the heat collection layer 43 by concentrating sunlight using the concentrating lens 46. As a result, a Stirling engine 11 equipped with the heat absorption structure 31B can be expected to have even greater heat absorption efficiency.

In the heat absorption structure 31B, the condenser lens 46 is provided inside the sealed container 45B, but a configuration in which the condenser lens 46 is provided outside the sealed container 45B may also be adopted. In addition to using a convex lens as the condenser lens 46, for example, a Fresnel lens (not shown) having a so-called sawtooth-shaped cross section may also be used. Furthermore, the surface shape of the sealed container 45B may be processed to form a structure in which the condenser lens 46 is integrated with the sealed container 45B.

As described above, the Stirling engine 11 of this embodiment can capture thermal energy from sunlight more efficiently by including the heat absorption structure 31 of each of the configuration examples described above. Note that in this embodiment, the Stirling engine 11 has been described as an example of a temperature difference power generation device, but the present technology can be applied to various temperature difference power generation devices other than the Stirling engine 11, for example, to a temperature difference power generation device using a Peltier element. Furthermore, the heat absorption structure 31 is not limited to use in temperature difference power generation devices such as the Stirling engine 11, but can also be used in various devices that need to recover thermal energy from sunlight with high efficiency, such as a solar hot water heater.

Note that this embodiment is not limited to the above-described embodiment, and various modifications are possible within the scope of the gist of this disclosure. In addition, the effects described in this specification are merely examples and are not limiting, and other effects may also be present.

11 Stirling engine, 21 Power generation section, 22 Cooling section, 23 Heating section, 31 Heat absorption structure, 32 Power source, 41 Upper end surface, 42 Heat generating element, 43 Heat collecting layer, 44 Fixing member, 45 Sealed container, 46 Condenser lens

Claims (8)

A heat absorption structure comprising: a heat collection layer that is provided so as to cover at least a portion of a heating section that takes in thermal energy used as a high-temperature heat source, and that is made of a fibrous or porous material having a predetermined heat resistance. The heat absorption structure according to claim 1 , further comprising a heating element that is provided on the heating unit side relative to the heat collection layer along a surface shape of the heating unit covered by the heat collection layer, and generates heat by electric power supplied from a power source. The heat absorbing structure according to claim 2 , wherein at least one of the heat collecting layer, the heating element, and a fixing member for fixing the heating element is blackened. The heat absorption structure according to claim 2 or 3, further comprising a sealed container that houses the heat collection layer and the heat generating element. The heat absorption structure according to claim 1 , further comprising: a single or multiple concentrating lenses for concentrating sunlight onto the heat collection layer. A heating unit that takes in thermal energy used as a high-temperature heat source;
a cooling section through which a fluid used as a low-temperature heat source flows;
a power generation unit that generates power in response to a temperature difference between the heating unit and the cooling unit;
a heat absorption structure having a heat collection layer formed of a fibrous or porous body made of a material having a predetermined heat resistance, the heat absorption structure being provided so as to cover at least a portion of the heating portion. the heat absorption structure further includes a heating element provided on the heating unit side of the heat collection layer along a surface shape of the heating unit covered by the heat collection layer,
The temperature difference power generation device according to claim 6 , wherein the heating element generates heat by being supplied with at least a portion of the electric power generated by the power generation section. The temperature difference power generating device according to claim 7 , further comprising a power storage unit that stores at least a portion of the power generated by the power generation unit.

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