Direct use involves using geothermal heat directly (without a heat pump or power plant) for such purposes as heating buildings, industrial processes, domestic heating, greenhouses, aquaculture, public baths and pools. Direct use can use high and moderate to low temperature geothermal resources. Existing developments have generally been on an individual basis rather than capturing the benefits of combined use for district heating or industrial parks.
There is a wide range of direct uses in New Zealand for which consumer energy totals about 8 PJ. The largest geothermal direct user in the world is the Norske Skog Tasman pulp and paper mill at Kawerau. With an installed capacity of 210 MWt and an annual energy use of 7.5PJ, the plant uses geothermal fluids to generate clean process steam for paper drying, a source of heat in evaporators, timber drying and increasingly for electricity generation
Very low temperature resources can also be exploited for heat applications using ground-source heat pumps to provide space heating and cooling. This is a practical technology that can be used almost everywhere in New Zealand where some groundwater occurs and offers significant opportunities for electricity conservation; however, it cannot be used for electricity generation. For more on ground source heat pumps.