solar thermal

Solar Thermal Systems

Solar Thermal Devices

A solar thermal device captures and transfers the heat energy available in solar radiation which can be used for meeting the requirements of heat in different temperature ranges.

Three main temperature ranges used are:

Low temperature Hot water - 60°C to 80°C
Medium temperature Drying - 80°C to 140°C
High temperature Cooking & power generation - > 140°C

Types of Solar Thermal System

  • Solar Water Heating System
  • Solar Air Heating System (SAHS)
  • Solar Cookers
  • Others

Solar Water Heating System


Solar water heating system (SWHS) is a device which supplies hot water at 60°C to 80°C using only solar thermal energy without any other fuel. It has three main components, namely,

  • 1. Solar Collector
  • 2.Insulated hot water storage tank and
  • 3.Cold water tank with required insulated hot water pipelines and accessories.

In the case of smaller systems ( 100 – 2000 litres per day ), the hot water reaches the user end, by natural (thermo – siphon) circulation for which the storage tank is located above the collectors. In higher capacity systems, a pump may be used for forced circulation of water.

Working Principle

In a typical solar water heater, water is heated by the solar thermal energy absorbed by the collectors. The hot water with lower density moves upwards and cold water with higher density moves down from the tank due to gravity head. A bank of collectors can be arranged in a series – parallel combination to get higher quantity of hot water. A typical 100 litres insulated tank with a 2 m2 collector area, will supply water at a temperature of 60 - 80°C.

Hot Water Storage Tank

The tanks are generally made of stainless steel to avoid corrosion and are insulated to reduce heat losses. They are also fitted with electrical heater as a backup during monsoon days. The tanks may also be made of G.I. sheets or aluminium.

Cold Water Tank & Pipelines

Cold water comes from the over head tank. Hot water from the system is transferred to various utility points through to insulated pipelines. A heat exchanger may be provided when the water is hard.


Domestic: Bathing, Coffee / Tea preparation, Dishwashing etc.

Industrial: Pre-heating of boiler feed water, cooking / dishwashing in industrial canteens. washing of milk canes in dairies, sterilisation of surgical instruments etc.

Solar Energy

Solar radiation sustains all forms of life on earth. According to estimates, sun radiates about 1.74 x 1017 W of power per hour to earth....


Working Principle

In a typical solar water heater, water is heated by the solar thermal energy absorbed by the collectors water is heated by the solar ....