<P> Geosolar combisystems have been used to heat and cool a greenhouse using an aquifer for thermal storage . In summer, the greenhouse is cooled with cold ground water . This heats the water in the aquifer which can become a warm source for heating in winter . The combination of cold and heat storage with heat pumps can be combined with water / humidity regulation . These principles are used to provide renewable heat and renewable cooling to all kinds of buildings . </P> <P> Also the efficiency of existing small heat pump installations can be improved by adding large, cheap, water filled solar collectors . These may be integrated into a to - be-overhauled parking lot, or in walls or roof constructions by installing one inch PE pipes into the outer layer . </P> <P> The net thermal efficiency of a heat pump should take into account the efficiency of electricity generation and transmission, typically about 30% . Since a heat pump moves three to five times more heat energy than the electric energy it consumes, the total energy output is much greater than the electrical input . This results in net thermal efficiencies greater than 300% as compared to radiant electric heat being 100% efficient . Traditional combustion furnaces and electric heaters can never exceed 100% efficiency . </P> <P> Geothermal heat pumps can reduce energy consumption--and corresponding air pollution emissions--up to 44% compared to air source heat pumps and up to 72% compared to electric resistance heating with standard air - conditioning equipment . </P>

How deep does a ground source heat pump