Sun, the centre of our solar system delivers 17,000 million MW of energy every year to the Earth, an amount 15,000 to 20,000 greater than is currently utilised on the planet. The Sun, a continuously renewing source of energy is the living source of heat and light for the Earth. Since humankind first created shelter, builders and architects of ancient civilisations have sited and designed their buildings to take advantage of the sun's heat and light, what we now call solar architecture. Solar energy systems contribute to the health and well being of the occupants of the building as well as the surroundings. In addition, they reduce the dependence on conventional energy systems, which are scarce and more importantly damaging to the environment. Like a living organism, the solar building continuously seeks the path of the Sun. The building becomes a skin that orients the occupants to the universal calendar. The object of the building should be to synchronise the beauty and comfort of the natural world with the internal environment.
The solar radiation data available gives the values of energy per unit
area at select locations. Accurate information of the available solar radiation
at a given place is essential for the design of efficient solar energy
systems. One has to ascertain the maximum and minimum levels of radiation
at a place and adopt a suitable value for the design of the system.
Considering the radiation available in different parts, India is divided into five zones. The global radiation varies from 3.5 to 6.3 kWh per day per sq.m. more than 80% of the country receives an average solar energy radiation level of above 5.2 kWh per sq.m. on horizontal surface. Thus, there is great scope for the use of solar energy for various applications in our country.
A number of systems utilising solar energy have been developed over the years mainly for the purpose of heating space as well as water, and other associated applications such as solar dryers, water distillation plants as well as photovoltaic cells which converts solar energy into electricity. Solar energy utilisation techniques can be classified as passive, active and hybrid systems.