JPS5932664B2 - Solar Stirling cycle engine with Fresnel lens - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a solar Stirling cycle engine combined with a Fresnel lens.

In the first place, if we could create a so-called solar engine that operates using solar heat, for example, when used to operate a solar heating and cooling system, the system itself would operate in accordance with the amount of solar radiation, so the system itself would immediately respond to the amount of solar radiation. This is convenient when considering system control.

In this way, not only can solar heat be used to take advantage of its characteristics in the operation of various systems related to solar heat, but it can also be used to perform a variety of other tasks, saving electrical energy. Dogs contribute to energy conservation.

Conventionally, a solar engine equipped with a parabolic solar heat reflector as shown in Figure 1 was considered, but the distance from the apex of the reflector to the focal point was The thickness is related to the shape of the curved surface, and once the value of h is determined, the shape of the parabolic curved surface is automatically determined.
As shown in the figure, it is thick (if this is done, the value of h will become large).

On the other hand, if the solar radiation area is expanded without changing the value of h as shown in FIG. 3, there is a drawback that the reflecting mirror itself becomes abnormally large.

In addition, when the reflector and the engine are integrated as shown in Figure 1, the attitude of the engine changes as the sun moves and the engine needs to track the sun.In order to avoid this inconvenience, the reflection from the engine body If the mirror parts were separated, the reflector would have to track the sun, so it would be necessary to make a fairly large notch in the center of the reflector, as shown in Figure 4. This results in a decrease in the sunlight receiving area.

Therefore, it is necessary to make the notch hole as small as possible, so even in the heat receiving part of the engine part, it is not possible to make it that thick, and measures to reduce heat leakage from the external surface of the part cannot be taken as desired. This also results in a decrease in the thermal efficiency of the engine itself.

Furthermore, conventional solar engines simply collect sunlight with a reflector and use the resulting heat as a high heat source for the heat engine.

By combining a Fresnel lens and a Stirling cycle engine, the present invention eliminates the various drawbacks caused by using the reflector and increases solar heat collection efficiency, and also effectively combines a Fresnel lens and a Stirling cycle engine. By focusing on the fact that natural convection of air is induced by this, and by using this convective air as the cooling heat source of the Stirling cycle engine, the aim is to obtain a simple and compact solar Stirling cycle engine with excellent thermal efficiency. It is said that

A further object of the present invention is to provide a solar Stirling cycle engine that is equipped with a Fresnel lens that reduces heat leakage from the outer surface of the working fluid heating section of the Stirling cycle engine and has excellent strength.

Therefore, in the present invention, a working fluid heating section of a Stirling cycle engine is provided near the focal point of a Fresnel lens, which has a curvature that allows sunlight to always be tracked perpendicularly to the lens surface, and the outer surface of this section The Stirling cycle engine is generally housed in a transparent vacuum container to reduce heat leakage from the engine, and the Stirling cycle engine is placed upright and its cooling section is placed below the heating section to achieve this purpose. This is what I am trying to do.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 5 shows an embodiment of a solar Stirling cycle engine combined with a Fresnel lens according to the present invention.

Reference numeral 1 is a Fresnel lens, which has a slight curvature to prevent bending of the lens that occurs when the area of a flat Fresnel lens increases and to increase the bending strength of the lens.

3 is a working fluid heating section of an upright Stirling engine, and 5 is a working fluid expansion space.

6 is a displacer, 7 is a power piston, 8 is a flywheel, and 10 is a regenerator.

Reference numeral 11 denotes cooling fins attached around the cooling chamber 9 of the Stirling cycle engine.The cooling chamber 9 and the cooling fins 11 constitute a cooling section, and the working fluid in the cooling chamber 9 is cooled by convection air.

2 is a transparent vacuum container, and a vacuum space 4 is provided between it and the working fluid heating section 3 and the regenerator 10.

Further, in FIG. 7, the Stirling cycle engine section 13 and the Fresnel lens section 1 for capturing sunlight are separated, and an optical fiber 14 connects them.

Next, the operation of the solar Stirling cycle engine combined with a Fresnel lens according to the present invention will be described.

Now, the sunlight that has passed through the Fresnel lens 1, which can track sunlight and has a curvature in the direction of the working fluid heating section 3, further passes through the transparent vacuum container 2 and hits the outer surface of the working fluid heating section 3, generating heat. , heating the same wall surface.

Therefore, the temperature of the wall surface increases, but since the cavity 4 outside the wall surface is a vacuum, most of the heat is used to heat the working fluid in the engine expansion space 5, and the fluid expands.

As a result, the displacer 6 is pushed down and is further pushed down together with the power piston 7.

Thereafter, the displacer 6 is pushed upward again by the inertia of the flywheel 8, and the high-temperature working fluid in the space 5 flows downward along the side of the displacer 6, giving heat to the regenerator 10 and cooling chamber 9. It enters the circuit and is cooled through the wall of the circuit.

Next, the power piston 7 rises and the cooled working fluid is compressed.

In this state, the displacer 6 begins to fall again, so the working fluid returns to the heating expansion space 5 while recovering the heat of the regenerator 10 again.

The engine operates by repeating this cycle, and the working fluid in this case is air, but the same principle applies to engines that use helium or hydrogen as the working fluid and are sealed and pressurized inside the engine. .

In addition, in the Solar Stirling engine combined with a Fresnel lens of the present invention, as schematically shown in FIG. is cooling the cooling section of the Sterling Cycle Station.

Next, the effects of the present invention will be described.

In the Fresnel lens combined solar Stirling cycle engine of the present invention, the distance H between the working fluid heating section 3 and the Fresnel lens 1 can be determined only by the focal length of the lens.

(See Figure 5). The most important advantage is that an effective space can be secured between the Fresnel lens and the heating section.

Moreover, since it is possible to easily manufacture a lens by selecting its focal length almost arbitrarily, the distance H can also be determined freely, and therefore, miniaturization can be achieved.

In addition, the sunlight receiving area can be freely selected based only on issues related to light collection, and even when tracking the sun, the space between the lenses can be used to move only the lenses without moving the engine itself. This can be easily achieved by

Furthermore, there is no need to provide a cutout hole in the lens.

In addition, compared to the case of a parabolic curved reflector, the solar light condensing part itself can be made lighter due to the reduction in the development area due to the difference in curvature, which makes the solar engine itself lighter and simpler. linked.

Furthermore, in this solar Stirling cycle engine, there are no external restrictions on the size of the working fluid heating section, the so-called solar light collecting and receiving section, so that the size of the working fluid heating section, the so-called solar light collecting and receiving section, is not subject to any external restrictions. In order to reduce heat loss, these can be covered with transparent containers, and the gaps created between them can be evacuated.

As a result, heat loss due to heat conduction and convection heat transfer from these parts can be kept to an extremely low level, the temperature of the working fluid heating section increases dramatically, and it is not directly affected by outside air such as wind. As a result, the temperature remains stable and the thermal efficiency of the engine is further improved.

Experiments have shown that if a vacuum section is not formed, heat is carried away in the presence of wind, resulting in a significant drop in efficiency.

- If the surface temperature of the heating part is not a vacuum part 2
In some cases, the temperature has been measured to be 500°C or higher.

This is because heat loss due to convection and heat conduction can be sufficiently prevented if the engine is exposed to heat, and this has led to a significant increase in the thermal efficiency of the heat engine.

Further, the Fresnel lens used in the present invention has curvature to improve the bending strength of the lens itself.

As a result, the lens can be made larger without requiring extra reinforcing materials or supporting members.

Further, since the Fresnel lens has a curved surface, it is more preferable that the curved surface side is on the engine side, which is more compact in terms of protection of the Stirling cycle engine section and overall size.

Furthermore, in the present invention, by using a solar Stirling cycle engine combined with a Fresnel lens, natural convection of air is induced, and the convection air cools the cooling section of the Stirling cycle engine, so the structure of the cooling section is simplified. , and economical.

In addition, in the case of the one shown in FIG. 7, the inconvenience that the Stirling cycle engine section 13 must always be attached to the Fresnel lens 1 outdoors is eliminated.

In this way, since the Fresnel lens with curvature is used to collect sunlight, the Stirling cycle engine as a whole can be simplified and compact compared to conventional ones. Since the engine itself can be firmly fixed and installed on the ground without any light-receiving area, it has good stability, and it also has many excellent effects such as reducing heat loss and increasing the thermal efficiency of the Stirling cycle engine. It becomes possible to perform.

[Brief explanation of drawings]

Figure 1 shows a solar engine using a parabolic curved reflector.
Figure 3 shows the relationship between the shape of the parabolic curved surface of the reflecting mirror and the focal length. Figure 4 shows the movement when the Stirling cycle engine body is fixed and only the parabolic curved reflector is moved.
This indicates the size of the notch hole. FIG. 5 shows an embodiment of a solar schooling cycle engine combined with a Fresnel lens according to the present invention. FIG. 6 schematically shows the state of the cooling air flow due to natural convection in this solar Stirling cycle engine combined with a Fresnel lens. FIG. 7 shows an example of use in which the Stirling cycle engine section and Fresnel lens section are separated. 1... Fresnel lens, 2... Transparent vacuum container, 3...
... Working fluid heating section, 4... Vacuum section, 5... Working fluid expansion space section, 6... Displacer, 7...
Power piston, 8... Flywheel, 9... Cooling chamber, 10... Regenerator, 11... Cooling fin, 12
... Parabolic curved reflector, 13... Stirling cycle engine section, 14... Optical fiber, 15... Concave lens.

Claims (1)

[Claims] 1. The working fluid heating section of the Stirling cycle engine is located near the focal point of the Fresnel lens, which has a curvature that allows sunlight to be tracked so that it always hits the lens surface perpendicularly, and heat leakage from the outer surface of this section is prevented. A solar Stirling cycle engine, characterized in that the part is generally housed in a transparent vacuum container in order to reduce the temperature, and further, the Stirling cycle engine is stood upright, and its cooling part is disposed below the heating part.