Solar water heating is one of the most common and cost-effective uses of solar energy. Solar hot water collectors heat water for washing, showers, and other domestic uses. Over 100,000 of them have been installed in the United States.
Solar hot water systems typically use solar energy to pre-heat the water that is incoming to a conventionally fueled heating tank. The warmer the water from the solar heater, the less conventional fuel will be needed to provide the household’s hot water needs. (Source: http://www.rerc-vt.org/solarbasics.htm)
Solar heaters convert up to 60 per cent of the sun’s energy into heat whereas PV cells are far less efficient and convert only 12 to 15 per cent of the sun’s energy into electricity.
Sophia Gordon Hall has a large rooftop array of solar water heaters. They are expected to provide the energy for heating about 40% of the domestic hot water in the building.
Check out the real-time energy display that shows:
In a solar hot water system, collector tubes inside an insulated box absorb the sun’s heat and transfer the heat to water or another liquid flowing through the tubes. In areas where freezing is not a threat, the system can be an "open loop" where the water flowing through the tubes is heated directly for use. In colder areas the system is a "closed loop." Antifreeze liquid is heated before transferring its heat to the water by way of a heat exchanger. (Source: http://www.nesea.org/buildings/info/solarwater.html)
In SGH, water is pumped to the panels and heated, then that heat is transferred to domestic hot water and stored. The water circulating to the panels drains back into the building at night and when there is a risk of freezing.
Components of a Solar Water Heater
Links to More Information on Solar Hot Water
US Department of Energy’s Energy Efficiency and Renewable Energy Program: