Solar thermal technology uses the sun energy rather than fossil fuels to generate low cost , environmentally friendly thermal energy.This energy is used to heat water or other fluids and can also power solar cooling systems . Solar thermal systems differ from solar photovoltaic(PV) systems , which generate electricity rather than heat.
Solar thermal energy is the use of solar energy to produce heat.This is an effect familiar with , when enter into the car after it has been parked in the sun on a hot summer day.Solar thermal energy works in the same way except that the heat generated is put to practical use to heat water or space heating.By using a solar thermal systems , you make an effective contribution in preserving our energy reserves and environmental protection by reducing CO2 emission.
The Solar collectors absorb the suns rays and convert them to heat and transfer the heat to a heat-transfer fluid .The heat transfer fluid is typically a glycol and water mixture in regions where seasonal freezing in a concern.The heat transfer fluid is then pumped into a heat exchanger located inside the water storage tank where it heats the water.
Solar energy collectors are special kind of heat exchangers that transform solar radiation energy to internal energy of the transport medium.The major component of any solar system is the solar collector.
This is a device which absorbs the incoming solar radiation , converts it into heat and transfer this heat to a fluid flowing through the collector.The solar energy collected is carried from the circulating fluid either directly to the hot water or space conditioning equipment or to a use at night and/or cloudy days.
SUN TRACKING COLLECTORS:
Energy delivery temperatures can be increased by decreasing the area from which the heat losses occur.Temperatures far above those attainable by FPC can be reached if a large amount of solar radiation is concentrated on a small collection area.
This is done by interposing an optical device between the source of radiation and the energy absorbing surface.
The collectors falling in this category are:
1.Parabolic trough collector
2.Linear fresnel reflector
1.PARABOLIC TROUGH COLLECTOR:
PTC are made by bending a sheet of reflective material into a parabolic shape.A metal black tube , covered with a glass tube to reduce heat losses, is placed along the focal line of the receiver.
2.LINEAR FRESNEL REFLECTOR:
LFR technology relies on an array of linear mirror strips which concentrates light on to a fixed receiver mounted on a linear tower.The LFR field can be imagined as a broken up parabolic trough reflector.
It is a point focus collector that tracks the sun in two axes , concentrating solar energy onto a receiver located at the focal point of the dish.
The systems can easily integrate in fossil-fuelled plants for hybrid operation in a wide variety of options and have the potential to operate more than half hours of each year at nominal power using thermal energy storage.
Its cost is about Rs 50,000/-