The principle behind solar thermal technologies is the same one often used to brew tea in a jar outside on a hot summer day. The sun's energy radiates to the earth and is captured in a jar of water. The water is warmed by this captured energy, and brews the tea.
In the same manner, solar thermal energy can be used to heat water for household use.
A solar water heating system requires collectors ("the jar") to absorb the sun's energy and a storage system to hold the energy until it is needed. The collectors are large, flat panels that are most frequently mounted on a roof. The storage systems look and act like conventional water heaters. Pumps are also part of the system and are used to circulate the heated water.
A residential solar water heating system is usually designed to meet 50 to 80 percent of a home's water heating requirements. Water heating typically accounts for about 14 to 25 percent of the average home's utility bill.
Solar electric is energy converted directly into electricity.
This conversion is done through solar cells, also known as photovoltaic or PV cells. PV modules are made up of individual PV cells and are joined together to form a PV array which is used to generate electricity. The PV array is installed on a roof or in a sunny location to maximize the sun's rays. When the sun shines on the array, the sun's energy is converted into electric current that can be used to operate appliances and other household devices.
Once installed, a photovoltaic system requires little maintenance and can produce power for more than 20 years.