Heat Pump

A heat pump is a device that uses mechanical or thermal energy to move heat from one place to another rather than generating heat directly, running an electrically powered refrigeration cycle that makes it markedly more efficient than a furnace or electric heater for warming a space. A vapor-compression cycle circulates refrigerant that extracts warmth from cold outdoor air and releases it indoors during winter, and the same cycle can run in reverse in summer to cool a building much like an air conditioner. Lord Kelvin described the underlying theory in 1852, and Peter von Rittinger built the first practical heat pump between 1855 and 1857; the technology saw real use during the World Wars, when fuel-short Switzerland installed about 35 heat pumps between 1937 and 1945, and London's Royal Festival Hall opened in 1951 with a water-source heat pump drawing on the Thames.