Geowarmth Heat Pumps

In a typical ground source heat pump installation fluid circulates around the ground in plastic pipes at a lower temperature than the ground, say at 5oC.  This creates a heat gradient and draws heat from the ground into the fluid in the pipe.  The fluid passes through an evaporator (heat exchanger) in the heat pump and the heat extracted from the ground is absorbed by the refrigerant which circulates around the heat pump.  The refrigerant becomes a gas and is compressed in a compressor which causes further heat.  Try holding a finger over the end of a bicycle pump to see how compressing a gas creates heat.  The pressurized refrigerant then passes over another heat exchanger called a condenser where the heat is transferred to the building’s underfloor or radiator pipe work.  Having given up its heat, the refrigerant passes through an expansion valve where its pressure and temperature further reduces returning it to a liquid state to start the cycle again.  The main power consumer in a heat pump is the compressor, but the majority of the energy comes from the environment.  A typical ratio is that for every 1kW of electrical input to a ground source heat pump, 4kW of thermal output is generated.