![]() Īs of 2004, there are over a million units installed worldwide, providing 12 GW of thermal capacity with a growth rate of 10% per year. Open loop systems dominated the market until the development of polybutylene pipe in 1979 made closed loop systems economically viable. Īs a result of the 1973 oil crisis, ground source heat pumps became popular in Sweden and have been growing slowly in worldwide acceptance since then. Professor Carl Nielsen of Ohio State University built the first residential open loop version in his home in 1948. Webber built the first direct exchange ground source heat pump in the late 1940s sources disagree, however, as to the exact timeline of his invention The first successful commercial project was installed in the Commonwealth Building (Portland, Oregon) in 1948, and has been designated a National Historic Mechanical Engineering Landmark by ASME. Īfter experimenting with a freezer, Robert C. Heinrich Zoelly had patented the idea of using it to draw heat from the ground in 1912. The heat pump was described by Lord Kelvin in 1853 and developed by Peter Ritter von Rittinger in 1855. Penetration depth in metres of diurnal and annual temperature cycles The "penetration depth" is defined as the depth at which the temperature variable is less than 0.01 of the variation at the surface, and this depends on the type of soil: Below that, in the deeper layer, the temperature is effectively constant, rising about 0.025 ☌ per metre according to the geothermal gradient.In the shallow layer to a depth of about 8–20 metres depending on soil type, the thermal mass of the ground causes temperature variation to decrease exponentially with depth until it is close to the local annual average air temperature it also lags behind the surface temperature, so that the peak temperature is about 6 months after the surface peak temperature.In the surface layer to a depth of about 1 metre, the temperature is very sensitive to sunlight and weather,.The thermal properties of the ground near the surface Ground-source heat pumps take advantage of the difference between the ambient temperature and the temperature at various depths in the ground. Setup costs are higher than for other heating systems due to the requirement to install ground loops over large areas or drill bore holes, and for this reason air source heat pumps are often used instead. ![]() Ground source heat pumps (GSHPs) – or geothermal heat pumps (GHP) as they are commonly termed in North America – are among the most energy-efficient technologies for providing HVAC and water heating, using far less energy than can be achieved by burning a fuel in a boiler/furnace or by use of resistive electric heaters.Įfficiency is given as a coefficient of performance (CoP) which is typically in the range 3 – 6, meaning that the devices provide 3 – 6 units of heat for each unit of electricity used. A heat pump in combination with heat and cold storageĪ ground source heat pump (also geothermal heat pump) is a heating/cooling system for buildings that uses a type of heat pump to transfer heat to or from the ground, taking advantage of the relative constancy of temperatures of the earth through the seasons.
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