JPS5911824B2 - solar pond - Google Patents

Description

[Detailed description of the invention] The present invention relates to solar ponds.

A solar pond is a device that stores solar heat in pond water.

Conventionally, in order to increase the solar heat collection temperature, measures have been taken to reduce heat dissipation by, for example, using the density of a salt solution.

The structure of a conventional general solar pond will be explained based on FIG.

Solar ponds generally have a non-convection layer 1 at the top as shown in the figure.
, the lower part is called the convective layer 2, and sunlight passes through the non-convective layer 1 of the soil and stores heat in the convective layer 2 below, and low-temperature water A is stored in this convective layer 2 and comes out as high-temperature water B. Go to heat exchanger 3
The data is provided to the usage system 4 via.

In the non-convective layer 1 above the convective layer 2, a concentrated solution C of salts flows in from the lower part, that is, from a little soil in the convective layer 2, and fresh water flows in from the upper part, and these mix and become concentrated. The solution (diluted solution) E in which the concentration has decreased is discharged from approximately the middle of the non-convection layer 1.

Due to this forced circulation, as shown in the relationship between concentration, density, temperature, and depth in Figure 2, the concentration, density, and temperature are constant at the location of convective layer 2, and the concentration, density, and temperature are constant in the non-convective layer. At position 1, a gentle slope line is formed.

By appropriately selecting the type of salt in the non-convection layer 1 and the concentration of the salt-making solution C to be supplied, a density gradient is formed in accordance with the concentration gradient.

By creating this density gradient, it is possible to prevent the density difference caused by the temperature difference, and furthermore, to prevent the occurrence of convection due to buoyancy, thereby forming the non-convection layer 1.

Therefore, even if the temperature in the lower part of the water tank rises, convection is prevented in the non-convection layer 1 due to the density gradient, which in turn can prevent heat radiation, making it possible to store heat for a long time.

However, to form this solar pond, in order to forcibly form a concentration gradient, it is necessary to flow a large amount of salt-making solution C and fresh water, which also requires considerable cost.

The present invention overcomes the drawbacks of the solar pond and provides an effective and economical solar pond by simple means.

An embodiment of the present invention will be described below based on the drawings.

FIG. 3 shows the structure of the solar pond of the present invention. To make it easier to absorb sunlight, the bottom of the aquarium is blackened with asphalt or black plastic, and a vertical fin tube 6 is passed horizontally above the blackened bottom 5, and a special tube is placed on the blackened bottom 5. Salt crystals 7 that have become black due to the treatment are accumulated, and a saturated salt solution 8 is filled above them, and a fresh water layer 9 is further formed above them.

In such a state, a rapid change in concentration is formed at the interface between the saturated salt solution 8 and the fresh water layer 9, and the fresh water layer 9 plays the role of heat insulation and the role of maintaining the concentration change.

Solar heat is absorbed by the blackened portion of the bottom surface, raising the temperature of the surrounding saturated salt solution 8.

As the temperature rises, the saturated solution becomes unsaturated, the solubility increases, and salt crystals T begin to dissolve further, and the concentration naturally increases near the bottom, and from the interface between the fresh water layer 9 and the saturated solution 8 to the bottom. A gentle concentration gradient is naturally formed,
A concentration/density/temperature distribution is formed as shown in Figure 4.

This solar pond is provided with a chemical inlet F and a drainage outlet G, but these are not always necessary, and a mass-mouth type float 10 on the surface of the fresh water layer 9 or a transparent or reflective structure is used. You can also perform this operation.

Note that the drainage outlet G is for treating inflow water such as rainwater, and the chemical solution inlet F is for maintaining the transparency of the fresh water layer 9.
It is used to periodically inject a chemical solution to prevent the growth of algae and plankton.

In addition, the trout-shaped floats 10 and the like were installed for the purpose of preventing the effects of waves and wind on the ice surface from being transmitted to the inside of the solar pond.

With the above configuration, the vertical fin tube 6 is used to extract heat, and the low temperature water A is heated here and becomes high temperature water B, which exits and is supplied to the utilization system 4 via the heat exchanger 3. .

The reason why the vertical fin tube 6 is used is because the bottom of the water tank is made up of eight layers of saturated solution of salts, which is cooled when heat is taken out and salts precipitate and stick to the vertical fin tube 6. Since the vertical fin tube 6 has the effect of preventing sticking in that crystals that are fixed to a certain extent will peel off once they grow, it is possible to prevent heat transfer from being inhibited.

Figure 4 shows the concentration, density, and
Shows the relationship between temperature and depth.

In comparison with the conventional example shown in FIG. 2, the concentration, density, and temperature all show a natural increase toward the bottom, indicating that it has an effect of preventing heat radiation.

FIG. 5 shows the relationship between the specific gravity and temperature of a saturated solution, and as the temperature of the saturated solution increases, the specific gravity also increases.

It can be seen that even if solar heat is stored at the bottom of the solar pond of the present invention, the specific gravity increases, so no convection occurs between the upper fresh water layer 9 and the saturated salt solution 8 and within the saturated salt solution 8 layer.

As described above, according to the solar pond of the present invention, a concentration gradient is naturally formed, so a device for feeding the salt-making solution and fresh water and discharging the diluted solution is provided to forcibly create a concentration gradient, as in the conventional solar pond. It is no longer necessary to form a non-convective layer, thus reducing the maintenance costs involved.

Moreover, since a vertical fin tube is used, it is possible to prevent salts from sticking to the tube, which is very effective.

[Brief explanation of the drawing]

Figure 1 is a longitudinal cross-sectional view showing the structure of a conventional solar pond, Figure 2 is a diagram showing the relationship between concentration, density, temperature, and depth in the solar pond shown in Figure 1. Figure 3 is the structure of the solar pond of the present invention. FIG. 4 is a diagram showing the relationship between concentration, density, temperature, and depth in the solar pond shown in FIG. 3, and FIG. 5 is a diagram showing the relationship between specific gravity and temperature of the saturated solution. 5... Blackened bottom surface, 6... Vertical fin tube, 7... Salt crystals, 8...
・Saturated salt solution, A...Low temperature water, B...
High temperature water.

Claims (1)

[Claims] 1. The bottom of the aquarium is blackened, a vertical fin tube is passed horizontally above the bottom near the water layer, salt crystals are accumulated on the bottom, and a saturated salt solution is filled above it, and By providing a fresh water layer above it, a sharp (large) concentration difference is formed at the boundary between the saturated salt solution layer and the fresh water layer, and a gentle concentration distribution is naturally formed in the saturated salt solution layer as well. Features solar pond.