Solar thermal energy and application

Solar thermal energy is the use of solar radiation as heat. Sunlight is absorbed by a surface (the absorber), which converts it into heat that warms a fluid (water, air or oil). The heat is used directly or to run a heat engine for electricity. It does not use photovoltaic cells.

Main components

A collector (flat-plate or concentrating) with a black absorber, transparent cover glass, insulation, a heat transfer fluid, and a storage tank. Flat-plate collectors give low temperatures (up to 80–100 °C); concentrating collectors (parabolic trough, dish, tower) give medium to high temperatures (150–1000 °C).

 Sun ---> [Glass cover]
          [Absorber plate + tubes] --> hot water
          [Insulation]                  to tank

Applications

1. Water heating: domestic and commercial solar water heaters (common in Nepal's urban homes, hotels and hospitals).
2. Space heating and cooling: passive solar buildings, absorption cooling.
3. Cooking: box-type and parabolic solar cookers.
4. Drying: solar dryers for crops, fruits, herbs and timber.
5. Desalination and distillation: solar stills.
6. Industrial process heat: pasteurisation, dairy, textile.
7. Electricity generation: concentrating solar power (CSP) plants with steam turbines, with heat storage in molten salt.
8. Greenhouse heating and swimming-pool heating.