JPS61228293A - Underground storage of heat by hygroscopic substance - Google Patents

Abstract

PURPOSE:To store large capacities of heat by a method in which water vapor of a temperature higher than the temperature of the ground is placed into the underground, diffused, and condensed to heat the ground and warm water is also impregnated into the ground. CONSTITUTION:When a hygroscopic substance 2 is heated by a heater 3 to high temperatures, the water in the hygroscopic substance is discharged in the form of water vapor. Although the water vapor so discharged becomes water by being cooled by soil 1, its sensible heat and latent heat of evaporation are discharged. When the heating of the heater 3 is stopped and cold water is passed through a heat recovery pipe 5 to cool the hygroscopic substance 2, the hygroscopic property of the substance 2 is increased as its temperature is lowered, the partial pressure of water vapor is lowered, and warm water held by the soil 1 is vaporized to water vapor, whereupon the heat of the soil is absorbed by water vapor. The water vapor so vaporized is absorbed by the substance 2, but if discharges its sensible heat and latent heat of vaporization to raise the temperature of the substance 2. The fluid in the pipe 5 can thus be heated by the substance 2.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for storing thermal energy underground and recovering underground heat.

Conventionally, there are two methods of storing thermal energy that can be used at relatively low temperatures: directly heating water or rocks, and storing heat by heating a heat storage agent that uses the fused tactile heat of materials, but the former requires large equipment. In the latter case, the usage temperature is limited and the heat storage agent is also expensive compared to the heat storage capacity. Therefore, both methods require high equipment costs and are not practical for use as a heat storage device.

The present invention is based on the physical properties of the infinite ± (sand, clay, etc.) found underground.

(a) Underground soil can retain 10 to 20% water by weight as capillary water or gravity water.

(b) When soil is partially heated underground to evaporate moisture, a pressure difference is created underground, which helps the movement of moisture and water vapor.

(c) Rapid heat transfer is possible even underground due to the diffusion of water vapor and the generation of the pressure difference (b). [Same principle as heat pipe] Focusing on (a), (b), and (c) above, an economical heat storage method has been established, and this method will be explained using the following diagram.

In FIG. 1, it is assumed that the hygroscopic substance (2) (a substance with significant hygroscopicity, such as silicage, lithium bromide liquid, etc.) has absorbed moisture up to saturation. In this state, if the hygroscopic substance (2) is heated by the heater (3) to raise its temperature, the hygroscopic substance releases the absorbed moisture as water vapor according to the temperature. The released water vapor is cooled at ±(1) and becomes water, but at this time, the sensible heat and latent heat of vaporization that the water vapor has is released.

The heat source for the heater (3) is provided by a heat source that needs to store its heat, such as late-night electricity, daytime solar heat, and waste heat.

Therefore, the heater may be of any type as long as it can support the properties of the hygroscopic substance.

The heat storage method has been described above, and now the heat recovery method will be explained.

Stop heating with the heater (3) and turn the heat recovery pipe (
5) When cooling the hygroscopic substance (2) by passing a low-temperature fluid such as cold water, the hygroscopic substance (2) increases its hygroscopic power as the temperature decreases, and the partial pressure of water vapor decreases. Due to the rapid diffusion of water vapor underground, the hot water held by ±(1) evaporates and becomes water vapor, which absorbs the heat of soil (1).

The evaporated water vapor is absorbed by the hygroscopic substance (2), and at this time, sensible heat and latent heat of vaporization are released, raising the temperature of the hygroscopic substance (2) (preventing the temperature from decreasing) and releasing the heat recovery pipe (5). Helps heat the fluid.

The fluid in the heat recovery pipe (5) is taken out to the outside as a high temperature and used.

This concludes the explanation of the heat storage method and the method of extracting the stored heat to the outside in the present invention.

Effect of the invention A: It is possible to store heat not only by the sensible heat of the hygroscopic substance (2) and the soil (1), but also by the latent heat of vaporization of the water absorbed by the hygroscopic substance (2). Capacity of heat can be stored. [Because soil (1) can be used to a large extent] B. Heat transfer to soil (1) is not by conduction, so the heat transfer speed is fast, so a large amount of heat can be transported in a short time, so a large amount of soil can be used. thing. (In the case of heat storage method by conduction, it is necessary to increase the temperature difference due to the limitation of thermal conductivity.) Since heat is mainly stored as latent heat due to the hygroscopic ability of C1 hygroscopic substance, compared to storage by sensible heat, the same amount of heat is Since the temperature difference is lower, there is less loss due to heat radiation.

D. Equipment costs are low because inexpensive hygroscopic substances such as silica gel can be used.

E. By using hygroscopic substances (such as lithium bromide solution), geothermal heat can be recovered by lowering the ground temperature to below the normal ground temperature.

F. Incidentally, if the soil temperature is 10°C, and the hygroscopic substance is a lithium bromide solution at 60°C to 70%, the heat storage capacity is 350% per kilogram of lithium bromide if the recovery is carried out at 30°C. kilocalorie (water 0.65
kilogram latent heat).

Therefore, it is highly effective for storing heat sources for heating and heat pumps.

Next, a system that utilizes the method according to the present invention for heating and cooling will be explained. .

The pipe α0 attached to the container (6) is connected to the evaporator of the absorption cooling machine (water is the refrigerant), and the end of the pipe α0 is open to the soil (1).

With the solenoid valve (8) closed and (9) open, the lithium bromide solution (7) is heated with the heater (3) to concentrate and store heat, and then the solenoid valve (9) is closed to make it completely airtight.

Subsequently, heat is recovered from the heat recovery pipe (5) to cool the lithium bromide solution (7), the hygroscopic substance (2), and the soil (1).

Since the air pressure in the container (6) is reduced by the concentrated and cooled lithium bromide liquid (7), the refrigerant (water) in the evaporator is evaporated and absorbed by opening the solenoid valve (8). Note that the heat obtained by absorption of the refrigerant is recovered again.

The water vapor discharged from the pipe αυ is cooled by heat exchange with the soil (1) and can be used as a refrigerant for both purposes. In addition, this system allows recovery at a temperature higher than the temperature of the soil (1), so it is possible to store low-temperature energy in ±+1) and recover it at high temperature in the absorbent material (2). It is possible.

[Brief explanation of drawings]

Figures 1 and 2 are flow sheets.

Claims (1)

[Claims] (1) By introducing water vapor higher than the soil temperature into the ground and causing the water vapor to diffuse and condense underground, the soil (1) in the ground is heated and the temperature is increased, and the soil (1) is heated. ) is a heat storage method that involves soaking hot water in the water. (2) By creating a pressure state in the ground that is lower than the saturated vapor pressure of the moisture contained in the soil (1), the moisture contained in the soil (1) is evaporated, and the latent heat is used to evaporate the moisture contained in the soil (1). ) and re-condensing the evaporated water vapor to recover latent heat. (3) A method of creating a pressure state lower than the saturated vapor pressure of water and using a hygroscopic substance to condense the water vapor recovered from the water contained in the soil (1). (4) A method for storing and dissipating heat underground and recovering underground heat by combining the above (1), (2), and (3).