page_title: Solar thermal energy
section_title: Low-temperature solar heating and cooling systems
hierarchical_section_title: Solar thermal energy / Low-temperature solar heating and cooling systems
caption_attribution_description: English: Flipped version of MIT Solar One House
context_page_description: Solar thermal energy is a form of energy and a technology for harnessing solar energy to generate thermal energy or electrical energy for use in industry, and in the residential and commercial sectors.
  Solar thermal collectors are classified by the United States Energy Information Administration as low-, medium-, or high-temperature collectors. Low-temperature collectors are generally unglazed and used to heat swimming pools or to heat ventilation air. Medium-temperature collectors are also usually flat plates but are used for heating water or air for residential and commercial use.
  High-temperature collectors concentrate sunlight using mirrors or lenses and are generally used for fulfilling heat requirements up to 300 deg C / 20 bar pressure in industries, and for electric power production. Two categories include Concentrated Solar Thermal for fulfilling heat requirements in industries, and Concentrated Solar Power when the heat collected is used for power generation. CST and CSP are not replaceable in terms of application.
  The largest facilities are located in the American Mojave Desert of California and Nevada. These plants employ a variety of different technologies.
context_section_description: Systems for utilizing low-temperature solar thermal energy include means for heat collection; usually heat storage, either short-term or interseasonal; and distribution within a structure or a district heating network. In some cases more than one of these functions is inherent to a single feature of the system (e.g. some kinds of solar collectors also store heat). Some systems are passive, others are active (requiring other external energy to function).
  Heating is the most obvious application, but solar cooling can be achieved for a building or district cooling network by using a heat-driven absorption or adsorption chiller (heat pump). There is a productive coincidence that the greater the driving heat from insolation, the greater the cooling output. In 1878, Auguste Mouchout pioneered solar cooling by making ice using a solar steam engine attached to a refrigeration device.
  In the United States, heating, ventilation, and air conditioning (HVAC) systems account for over 25% (4.75 EJ) of the energy used in commercial buildings (50% in northern cities)  and nearly half (10.1 EJ) of the energy used in residential buildings. Solar heating, cooling, and ventilation technologies can be used to offset a portion of this energy. The most popular solar heating technology for heating buildings is the building integrated transpired solar air collection system which connects to the building's HVAC equipment. According to Solar Energy Industries Association over 500,000 m² (5,000,000 square feet) of these panels are in operation in North America as of 2015.
  In Europe, since the mid-1990s about 125 large solar-thermal district heating
  plants have been constructed, each with over 500 m² (5400 ft²) of solar
  collectors. The largest are about 10,000 m², with capacities of 7
  MW-thermal and solar heat costs around 4 Eurocents/kWh without subsidies.
  40 of them have nominal capacities of 1 MW-thermal or more.  The Solar District Heating program (SDH) has participation from 14 European Nations and the European Commission, and is working toward technical and market development, and holds annual conferences.
caption: MIT's Solar House #1 built in 1939 used seasonal thermal energy storage (STES) for year-round heating.
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