JPS6342958B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a solar pond using hydrogel as a new heat storage material.

A solar pond is a pond that can absorb and store sunlight in the form of heat.

The conventional method of collecting and storing heat in a solar pond is to use a salt solution to create a concentration gradient to prevent convection, increase the heat insulation effect, and suppress heat radiation. To form this concentration gradient, fresh water may be injected into the concentrated salt solution, depending on the type and concentration of the salt.
A density gradient is formed in accordance with this concentration gradient, and this density gradient prevents the occurrence of a density difference due to a temperature difference, and also prevents the occurrence of convection due to buoyancy. If convection is prevented, heat radiation is suppressed and long-term heat storage becomes possible.

However, salt water solar ponds have the following drawbacks.

First, since it is a method of forcing fresh water to flow through a concentrated salt solution to form a concentration gradient, it is necessary to constantly flow fresh water into the upper layer, which requires maintenance and management costs and effort. Second, this method requires several months to build up the saline gradient and begin heat storage. Third, it causes salt damage due to water leakage, so it cannot be used for fish hatching or aquaculture where salt damage is fatal. Fourth, since the saline water content must be at least 20%, the need for a large amount of salt is not economically advantageous. Fifth, among salts, if boric acid soda is used for a long period of time, the salt will settle and the bottom will turn white. Although other salts are transparent, they are expensive compared to table salt, and anything other than table salt cannot be used economically. Sixth, the amount of heat stored is expressed as the product of specific heat, temperature, and mass, and the specific heat of water is the largest, so water has the largest amount of heat for the same mass at the same temperature. Generally, salts have a small specific heat, and the specific heat of a salt solution decreases as the specific gravity of the solution increases, so the amount of heat of a highly concentrated salt solution of the same mass at the same temperature decreases. Therefore, it can be said that concentrated salt water solar ponds are inefficient. Seventh, if algae, mud, or sand is mixed in, the large amount of concentrated saline water can cause salt damage and cannot be dumped.

The present invention takes into account the above-mentioned drawbacks, and as a result of intensive research into a heat storage material for solar ponds that can collect and store a large amount of heat, it is possible to achieve the objective by using a gel-like material as a completely new heat storage material for solar ponds. Based on this finding, we have arrived at the present invention.

In the present invention, an aqueous solution of an aqueous organic polymer dissolved in a silicate is neutralized with an acid, chloride, etc. to generate a gel-like substance, and this is used as a heat storage material for a solar pond. The present invention provides a heat storage material that is significantly improved over water solar ponds.

The heat storage material of the present invention will be described in more detail. First, the raw silicates, sodium silicate, potassium silicate, and lithium silicate, may be in the form of a powder or a concentrated solution (candy-like). Water-soluble organic polymer resins include cellulose-based resins such as carboxymethylcellulose, hydroxypropylcellulose, hydroxymethylcellulose, and methylcellulose, polysaccharide derivatives such as amylose, hydroxyethyl polyacrylate, polyacrylic acid and its salts, polymethacrylic acid and its salts, etc. Salt, polyvinylpyrrolidone, and polyvinyl alcohol all mix well with silicate to form a uniform hydrogel. Salts as neutralizing agents include chlorides such as magnesium chloride, calcium chloride, and aluminum chloride, or nitrates such as magnesium nitrate, calcium nitrate, and aluminum nitrate, or sulfates such as magnesium sulfate, calcium sulfate, and aluminum sulfate, or magnesium acetate. , acetates such as calcium acetate, aluminum acetate, and other acids, such as organic salts such as magnesium citrate, calcium citrate, magnesium tartrate, and calcium tartrate. Gels are formed with any of the above salts. Acids used as neutralizing agents include hydrochloric acid, sulfuric acid, nitric acid, acetic acid, succinic acid, citric acid, and fumaric acid.

The reaction conditions for gel production and the optimal conditions for use as a heat storage material are as follows: After dissolving the silicate, a water-soluble organic polymer resin is added to completely dissolve the gel, and then the gel is neutralized with acid or salt. For example, a so-called hydrogel containing a large amount of water is formed, but a hydrogel containing a water-soluble organic polymer resin is better than a hydrogel containing only silicate even if the silicate content is small. is generated, the transparency is improved, and the light absorption efficiency is increased. Economically, it is desirable to have a concentration of the silicate and water-soluble organic polymer resin such that the gel contains a large amount of water and does not cause fluidity. The commonly used silicate concentrations range from 0.1% to 10
%, and the concentration of water-soluble organic polymer resin
0.1% to 5% is optimal.

Although the concentration and amount of neutralizing conditions vary depending on the type of acid or salt, the normal neutralizing condition is a hydrogen ion concentration of 6 to 8. The so-called gelation time when a solution becomes gel-like is determined by the hydrogen ion concentration. For example, a solution of 25% sodium silicate and 2% polyvinyl alcohol at 20°C is mixed with 50% sulfuric acid at a hydrogen ion concentration of 7.0. When neutralized to
It will be completed in time. In the case of aluminum chloride, which is a salt, gelation occurs immediately upon adding the aluminum chloride aqueous solution to the sodium silicate-polyvinyl alcohol aqueous solution. The acid and salt used for gelation can be selected according to the required gelation rate, and a large amount of encapsulated water gel can be easily produced. Furthermore, using ink or black dye will further increase light absorption.

The hydrogel produced by the above method is economically inexpensive because it can be used as a heat storage material with a low concentration of silicate and water-soluble organic polymer resin.

Silicates are powder or candy-like, and water-soluble organic polymer resins are also powder, so they can be easily transported to remote areas, and the water gel produced is neutral, so there is no possibility of water leaking from the pond. However, it is completely harmless. Hydrogel contains a large amount of water with a small amount of silicate and a water-soluble organic polymer resin, which prevents water convection and suppresses heat radiation, so heat can be stored effectively. In addition, the specific heat, which is a measure of the amount of heat, is almost the same as that of water because it is a dilute solution containing a small amount of silicate and an organic polymer resin with a small specific heat.In comparison, salt water has a small specific heat. Because a large amount of salt is used, the specific heat is small, and if the same temperature and mass are used, the hydrogel pond will accumulate a much larger amount of heat. The above points are the most advantageous features of the present invention.

Next, the present invention will be explained in detail by examples.
The present invention is not limited to the following examples unless it exceeds the gist thereof.

Example 1 After dissolving 25g of powdered sodium silicate in 955ml of water, 2g of polyvinyl alcohol was added and dissolved uniformly, and a solution of 4.5g of sulfuric acid dissolved in 20ml of water was added to the sodium silicate solution. It was added dropwise to a polyvinyl alcohol solution with stirring to neutralize the hydrogen ion concentration to 7.0. 1 neutralized sodium silicate-polyvinyl alcohol solution
Pour 750ml into a thermos flask (inner diameter 90mm, depth 230mm), the solution will start to gel after about 1 hour, and after 3 hours, gently pour in 250ml of water, and the gel phase and water phase will be combined.
And so. On the other hand, pour 750 ml of 25% sodium chloride into the same thermos flask, and then gently pour 250 ml of water to make 1.

Place two thermos bottles directly under the 500W tungsten light bulb.
I installed them side by side. The distance between the bulb and the thermos is 300 mm from the opening of the thermos to the bulb glass surface, and the amount of light measured by the pyranometer is 0.804 cal cm ^-2 min ^-1 .
The temperature was measured using a thermocouple placed 190 mm from the opening of each thermos flask and a recorder. Light irradiation was achieved by repeatedly turning on a light bulb for 6 hours and then turning it off for 18 hours to make it almost the same as the solar radiation. When we measured this blinking process over a long period of time, we found that when we compared the temperature rise of the hydrogel and the salt, the hydrogel always maintained a higher temperature than the salt. In other words, when comparing the highest temperature immediately after 6 hours of lighting and the lowest temperature immediately after 18 hours had passed after the lights were turned off, the temperature of the encapsulated water gel was always higher than that of common salt. The minimum temperature after 82 hours, which is about 4 days, was 5.2°C higher for the hydrogel, and the maximum temperature after 92 hours was 8.5°C higher for the hydrogel.

Claims (1)

[Scope of Claims] 1. Uses a hydrogel, which is a reaction product obtained by neutralizing a mixed solution of an inorganic salt and a water-soluble organic polymer or an aqueous solution to which a dye is added, with an acid or a salt. A hydrogel solar pond characterized by: 2. One or two of alkali salts and alkaline earth salts such as sodium silicate, potassium silicate, and lithium silicate as the inorganic salts that form the hydrogel.
1. The water-enriched gel solar pond according to claim 1, wherein more than one species is used. 3 Water-soluble organic polymers contained in the hydrogel include polyvinyl alcohol, cellulose-based water-soluble resins such as carboxymethyl cellulose, hydroxypropyl cellulose, hydroxyethyl cellulose, and methyl cellulose, polysaccharide derivatives such as amylose, polyhydroxyethyl acrylate, and polysaccharide derivatives such as amylose. The water-encapsulated gel solar pond according to claim 1, which uses one or more of methacrylic acid and its salts, polyacrylic acid and its salts, and polyvinylpyrrolidone. 4 Acids that can be used as neutralizing agents for inorganic salts that produce hydrogel include hydrochloric acid, sulfuric acid, nitric acid, or organic acids such as acetic acid, succinic acid, citric acid, and fumaric acid.
The first claim using a species or two or more species
Water encapsulation gel solar pond described in section. 5 Salts used as neutralizing agents for inorganic salts that produce hydrogel include magnesium, calcium, manganese,
Acid metal salts of aluminum, cuprous, cupric, ferrous, ferric, nickel chlorides, nitric or sulfuric acids and organic acids such as acetic acid, fumaric acid, citric acid, succinic acid, etc. The hydrogel solar pond according to claim 1, in which one or more types are used. 6. The hydrogel solar pond according to claim 1, wherein the dye contained in the hydrogel is one or more of black coloring dyes such as ink, sulfur black, diamond black, and naphthol black. .