Geothermal direct heat
Hot water and steam near the earth’s surface is used to generate electricity. It’s also piped heat greenhouses, swimming pools, fish and prawn farms and for industrial processes such as timber drying.
Ground source heat pumps
Energy stored in the ground, groundwater and surface water can be transferred to efficiently heat and cool homes and other buildings.
How to channel the earth’s warmth
Ground source heat pumps (also known as geothermal heat pumps or GHPs) are very efficient and generate no direct carbon emissions (there may be some associated with their electricity usage). They’re being used in the commercial sector, where high installation costs can be offset quickly by greatly reduced operating costs, and for central heating at the higher end of the residential market.
The system consists of a heat source, a heat pump and a heating/cooling distribution system in the building. Heat sources include networks of pipes filled with water and anti-freeze laid flat and buried in shallow ground loops near the building. An alternative, commonly used in Christchurch, is to draw water from an aquifer. A heat pump then takes the heat gathered from the aquafer or soil and upgrades it so that it can heat buildings.
Water from the aquafer isn’t removed or polluted – only its warmth is used.
The systems make most economic sense in colder parts of the country.