20-09-2014, 02:27 PM
SOLAR POND TECHNOLOGY
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Abstract:
Had you ever thought of storing the solar thermal power without any expensive solar storage devices? .Can’t we
generate solar thermal energy in the form of low grade heat of 70-80.c with 20.c ambient temp .Yes this paper suggests a solution of
storing the solar energy only by constructing a simple pool of salt water ,isn’t it amazing?. Thus a solar pond is a pool of salt water
which serves as the solar energy collection and sensible heat storage.
The solar ponds made a tremendous progress in the last thirty years . This paper also mainly reviews the basic principles of the solar
pond and the problems encountered in its operation and its maintenance. Here we also discuss the factors that enhance the heat storing
capacities and also the factors that influence the technical and the economical viability of the solar ponds.
INTRODUCTION:
Energy is an important input in all sectors of any country’s economic growth. The standard of living of a given country can be directly
related to per capita energy consumption.
Due to the rapid increase in population and standard of living of human beings, there is problem of energy crisis. The supply of oil
will fail to meet the increasing population demand. Hence an alternative energy source had to be chosen to meet the future energy
demands.
Currently a number of alternative energy sources and the method of abstracting the energy had been discovered .Among the most
widely distributed and clean renewable energy resources ,the solar energy is one of the effective solution to environment pollution and
fossil fuel shortage. Solar energy is an abundant and renewable energy source. The annular solar energy incident on the ground in
India is about 20,000 times the current electrical energy consumption. Hence a very little amount of solar energy is sufficient to meet
the major energy demands , particularly in the tropical lands. But the use of solar energy has been very limited. This is because Solar
energy is the time dependent and intermittent energy resource. And also mainly solar energy is the diurnal energy resource. Hence
the main challenge laying here is storing the solar energy to meet the energy needs. Hence energies must be collected in large areas
with high initial investment .These solar energy storing systems must take care of collecting solar energy at cloud day and during
winter times .They should posses the efficacy of storing energy at night times in Oder to supply the energy when required in uniform
manner. This may result in further increase in total capital cost of building such systems. One among the best ways to overcome this
problem is to use large body of water for collecting and storage of solar energy. This concept is called SOLAR POND.
PRICIPLE OF OPERATION AND DECRIPTION OF A SOLAR POND:
A solar pond is a mass of shallow water about 1 or 2 metres deep with a large collection area ,which acts as a heat trap. It contains
dissolved salts to generate a stable density gradient . Part of the incident solar radiation entering the pond surface is absorbed
throughout the depth and the remainder which penetrates the pond is absorbed at the black bottom. If the pond were initially filled
with fresh water , the lower layers would heat up, expand and rise to the surface. Because of the relatively low conductivity ,the water
acts as an insulator and permits high temperature (over 90C ) to develop in the bottom layers . At the bottom of the pond , a thick
durable plastic layers liner is laid. Materials used for liners include butyl rubber, black polyethylene and hypalon reinforced with
nylon mesh. Salts like magnesium chloride, sodium chloride or sodium nitrate are dissolved in the water , the concentration varying
from 20 to 30 percent at the bottom to almost zero at the top.
ALGAE CONTROL
The thermal efficiency of a solar pond is strongly dependent upon the clarity of the pond which is reduced by the presence of algae or
dust. Bits of debris, dust or leaves lighter than water float on the surface and can be skimmed off. Dust and debris much lighter than
water will sink to the bottom .The dust accumulated at the bottom of the pond does not adversely affect the absorption of solar
radiation at the bottom of the pond. The dust floating in the gradient zone can be settled by adding alum. The growth of algae can be
controlled by adding bleaching powder or copper sulphate .If the water used in the pond is alkaline, copper sulphate will not dissolve.
Hull(1990)has proved detailed account of the relative merits of various methods of algae control.
CONCLUSIONS
Solar pond technology has made tremendous progress in the last fifteen years. An excellent monograph is now available on the
science and technology of salinity gradient solar ponds (Hull et al 1989).This technology is cost effective for low temperature process
heat needs of industry. The generation of electricity using solar ponds is not economically viable as yet .However , the new concerns
regarding the environment and safety of nuclear power plants and nuclear wastes disposal may change the picture totally