JPS6340456B2 - - 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 heat collection and storage feature of conventional solar ponds is that they form a non-convection layer that prevents convection and suppresses heat radiation. To suppress heat radiation, a concentration gradient of salts is created, and the density difference due to this concentration gradient prevents the occurrence of a density difference due to a temperature difference, thereby preventing the occurrence of convection due to buoyancy. If convection is prevented, heat radiation is suppressed and long-term heat storage becomes possible.

However, saline water solar ponds have the following drawbacks. To create a concentration gradient, fresh water is forced into the upper layer of a concentrated salt solution to forcibly form a concentration gradient, resulting in a dilute salt solution in the upper layer.Convection occurs in the upper layer and fresh water is constantly flowing. Therefore, maintenance and management costs and effort are required. This salt water pond takes a considerable number of days to form a salt water gradient and several months to start storing heat. In addition, even a small amount of water leakage results in highly concentrated salt water, so it cannot be used in areas where salt damage is fatal, such as when hatching or cultivating fish. Furthermore, since convection cannot be prevented unless the concentration of salt water is 20% or more, a large amount of salt is required, which is economically disadvantageous. Some salts, such as sodium borate, have the disadvantage that if used for a long period of time, the salt will settle and the bottom will turn white. Also, the amount of heat stored is expressed as the product of specific heat, temperature, and mass, but the specific heat of water is the largest, and since salts are relatively small, the amount of heat stored in water alone is the largest, and decreases as the concentration of salts increases. do. The calorific value of a salt solar pond determined by the density gradient method is a concentrated salt aqueous solution, so compared to a low concentration salt aqueous solution, a low concentration salt aqueous solution is larger at the same temperature and mass. Therefore, concentrated salt water solar ponds can be said to be an inefficient method. Furthermore, 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 has been made as a result of intensive research into a heat storage material for solar ponds that can collect and store a large amount of heat, taking into consideration the various drawbacks mentioned above, and has found that the purpose can be achieved 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.

The present invention neutralizes an aqueous solution of aluminates in silicates with acid to generate a gel-like substance, which is used as a heat storage material for solar ponds.The heat storage efficiency is much greater than that of conventional salt water solar ponds. The present invention provides a heat storage material characterized by improved properties.

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 powder or concentrated solution (candy-like), and sodium aluminate, potassium aluminate, and lithium aluminate may be in powder form or solution. good. Acids used as neutralizing agents include hydrochloric acid, sulfuric acid, nitric acid, or acetic acid;
These include succinic acid, citric acid, and fumaric acid. The ion exchange resin used as the neutralizing agent may be any weakly acidic or strongly acidic cation exchange resin.

Regarding the reaction conditions for gel formation and the optimal conditions for use as a heat storage material, gels can be formed by dissolving silicate and aluminate and then neutralizing them by adding acid or ion exchange resin, which contains a large amount of water. A so-called hydrogel is produced. The gelation time is faster with the addition of aluminate than with silicate alone. Economically, the gelation time is fast, and
Concentrations of silicates and aluminates such that flowability does not occur at low concentrations are desirable. The commonly used silicate concentrations are 0.1% to 10%, and the aluminate concentrations are based on the weight of the silicate.
0.1% or 30% is optimal.

Although the concentration and amount of neutralizing conditions vary depending on the type of acid and ion exchange resin, 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, but gelation occurs over a wider range of hydrogen ion concentrations when aluminate is added compared to silicate alone. Gel time is also fast. For example, 5% sodium silicate and 1
% sodium aluminate is neutralized with 50% sulfuric acid to a hydrogen ion concentration of 6.0, gelation begins in 5 minutes and completes in 30 minutes. As the amount of sodium aluminate increases relative to the amount of sodium silicate, the gelation time becomes faster, and the range of hydrogen ion concentrations at which gelation occurs widens as the amount of sodium aluminate increases. The acid and ion exchange resin used for gelation can be selected according to the required gelation rate, and a large amount of encapsulated water gel can be easily produced.

The aluminosilicate hydrogel produced by the above method is economically inexpensive because it is produced with low concentrations of silicate and aluminate and can be used as a heat storage material.

Since aluminosilicate hydrogel is neutral, it is completely harmless even if water leaks from the pond. Because the hydrogel contains a large amount of water, it can prevent water convection, thereby suppressing heat radiation and effectively storing heat. In addition, the specific heat, which is a measure of calorific value, is almost the same as water because it is a dilute solution containing a small amount of silicate and aluminate. Because it is used for water, its 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 with reference to examples, but 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, 2.5g of sodium aluminate was added and dissolved uniformly, and a solution of 5.0g of sulfuric acid dissolved in 20ml of water was added to the silicic acid. It was added dropwise to a sodium-sodium aluminate solution with stirring to neutralize the hydrogen ion concentration to 6.8. Pour 750ml of the neutralized sodium silicate-sodium aluminate solution into a thermos flask (inner diameter 90mm, depth 230mm), the solution will begin to gel after about 20 minutes, and after 2 hours, gently pour in 250ml of water. 1 in gel phase and water phase
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 was 300 mm from the opening of the thermos to the bulb glass surface, and the amount of light measured by the pyranometer was 0.804 cal cm ^-2 mm ^-1 .
The temperature was measured using a thermocouple placed 190 mm from the opening of each thermos flask and a recorder. The light irradiation was made to be similar to the solar radiation by repeatedly turning on a light bulb for 6 hours and turning it off for 18 hours. 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 was always maintained at a higher temperature than the salt. That is, 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 water encapsulation gel had a higher temperature than the salt. The lowest temperature after 82 hours, which was about 4 days, was 4.7°C higher for the water-encapsulant gel, and the highest temperature after 92 hours was 8.0°C higher for the water-enclosed gel.

Claims (1)

[Claims] 1. The invention is characterized by the use of an aluminosilicate hydrogel, which is a reaction product obtained by neutralizing a mixed solution of silicates and aluminates with an acid or an ion exchange resin. and solar pond. 2. Claim 1 states that one or more of alkali salts and alkaline earth salts such as sodium silicate, potassium silicate, and lithium silicate are used as the silicates from which the hydrogel is produced. Water gel solar pond. 3. Claim 1 states that one or more of alkali salts and alkaline earth salts such as sodium aluminate, potassium aluminate, and lithium aluminate are used as the aluminate salts that form the hydrogel. Water gel solar pond. 4. The acid used as a neutralizing agent for the mixed solution of silicates and aluminates that forms the hydrogel is hydrochloric acid, sulfuric acid, nitric acid, or one of organic acids such as acetic acid, succinic acid, citric acid, fumaric acid, etc. The water-encased gel solar pond according to claim 1, in which two or more types are used. 5. A patent claim that uses one or more of weakly acidic and strongly acidic cation exchange resins as an ion exchange resin as a neutralizing agent for a mixed solution of silicates and aluminates that produce encapsulated water gel. The hydrogel solar pond according to item 1 in the scope of .