Geothermal desalination is a process under development for the
production of fresh water using heat energy. Claimed benefits of this
method of desalination are that it requires less maintenance than
reverse osmosis membranes and that the primary energy input is from
geothermal heat, which is a low-environmental-impact source of energy.
Circa 1995, Douglas Firestone from
Nevada devised the use of
geothermal water directly as a source for desalination. In 1998,
several individuals began working with evaporation/condensation air
loop water desalination. The experiment was successful and a proof of
concept, proving that geothermal waters could be used as process water
to produce potable water in 2001.
In 2005 to 2009 testing was done in a sixth prototype of a device
referred to as a delta t device, a closed air loop, atmospheric
pressure, evaporation condensation loop geothermally powered
desalination device. The device used filtered sea water from Scripps
Institution of Oceanography and reduced the salt concentration from
35,000 ppm to 51 ppm.
A total of six prototypes and six modifications demonstrated that,
with process water approaching 100 °C (212 °F) and a chill
source about 2 °C (36 °F), a full-size device would
produce about 600 m³ of water per day.
Salt concentration in the
wastewater would only be about 10% above the level of the original
water, thus, from, say, 35,000 to about 38,000 parts per million, well
within the ability of osmoregulators to adjust.
Energy Council - Geothermal Desalination
ScienceDirect - Heat Transfer and Evaporation in Geothermal
Energy in Ethiopia
Geothermal heat pump
Hot dry rock
Portals: Renewable energy