Tapping solar energySolar energy not only has the potential to light up our homes, it is the energy behind our food and our lives
Energy, which has been considered the fuel for overall development, is also the prime mover of economic growth. In fact, there is a direct correlation between the degree of economic growth, the size of per capita income and per capita consumption of energy. This is why countries that have had access to an abundant supply of energy have high rates of industrial growth and a corresponding increase in the Gross National Product.
Most of the energy that we use comes from the sun, and we live in an atmosphere warmed by solar energy. We eat food produced by photosynthetic conversion of solar energy and obtain benefits from a system of wind, rain and rivers driven by solar energy. Though most energy in the universe is gravitational, man is most concerned with solar radiation. Experiments have shown that most life processes at or near the earth’s surface use the sun as a source of energy. The earth intercepts a huge quantity of energy from the sun, which is much higher than the annual human consumption.
The flow of energy from the sun to the earth and the many transformations of that energy represent a complex system. Such energy is transformed, stored and transported because it moves through the system and is in a state of long-term equilibrium.
The sun’s energy spectrum has been found to range from the shortest wave length (gamma, x-ray and ultraviolet) through the visible and infrared wavelengths, with infrared accounting for 50 percent of the total radiation received. Man is a part of a dynamic system that includes the physical, chemical and inert components of the environment. The system is constantly adjusting and changing, and the greatest quantity of its energy enters the system as solar radiation.
Research has shown that a part of the solar radiation is captured by green plants, which is converted to chemical or food energy through photosynthesis. Some of this powers the hydrologic cycle, the main feature of which is constant transfer, without which terrestrial plants and animals would not exist.
The chemical energy of plants is available to be converted to heat by burning (or by being buried and converted to fossil fuel). Food energy may pass through animals and plants and through herbivores to meat-eating animals along a series known as the food chain, which is a channel of energy flow and dissipation.
About 30 percent of the solar radiation intercepted by the earth is directly reflected back into space by clouds and land. About 47 percent is absorbed by the atmosphere, land and water. The small percentage of the incoming solar radiation that is absorbed by the leaves of plants and used in photosynthesis, which converts carbon dioxide and water into organic carbohydrates and oxygen, provides the energy for the basic biological requirements of the earth’s plants and animals. However, most people are ignorant about this fact even now.
Solar radiation can be controlled by man to produce useful heat and to produce electric power. Controlled solar radiation has long been used to heat water and to provide warmth for sprouting seeds and growing flowers and certain vegetables. It has also been collected to heat small and large houses in many urban areas, especially in developed countries.
Though the development of solar energy is in its early stages in Nepal, the number of solar heaters installed here is increasing every year. There are various potential applications of solar energy here, of which heaters, driers, pumps, cookers and furnaces are worth mentioning. Likewise, photovoltaic cells and other direct energy conversion devices can be used for water pumping, lighting and telecommunication purposes, especially in remote areas.
In Nepal, the potential of solar energy is enormous because a study conducted by the Water and Energy Commission in 29 sites some years ago estimated that the total solar energy available here could be very high indeed. However, just the availability of a resource does not fulfil our needs; what is essential is its maximum utilisation to meet the growing power needs. For this purpose, both the governmental and non-governmental agencies should work hand in hand.
Basnyat is freelance writer