Ground source heat pump

Geothermal (ground-source) heat pumps (GHP) are
one of the fastest growing applications of renewable energy
(see discussion at the end of this article) in the world, with
annual increases of 10% in about 30 countries over the past 10
years. Its main advantage is that it uses normal ground or
groundwater temperatures (between about 5 and 30o
C), which are available in all countries of the world.

Most of this growth has occurred in the United States and Europe,
though interest is developing in other countries such as Japan and Turkey.
The present worldwide installed capacity is estimated at almost
12,000 MWt (thermal) and the annual energy use is
about 72,000 TJ (20,000 GWh).

The actual number of installed units is around 1,100,000, but the data are incomplete.Table 1 lists the countries with the highest use of GHPs.