Geothermal heating
As of 2007, 28 GW of geothermal heating capacity is installed around the world, satisfying 0.07% of global primary energy consumption.
The cities of Reykjavík and Akureyri pipe hot water from geothermal plants under roads and pavements to melt snow.
Geothermal systems tend to benefit from economies of scale, so space heating power is often distributed to multiple buildings, sometimes whole communities.
This technique, long practiced throughout the world in locations such as Reykjavík, Iceland;[7] Boise, Idaho;[8] and Klamath Falls, Oregon;[9] is known as district heating.
[11] Some parts of the world, including substantial portions of the western USA, are underlain by relatively shallow geothermal resources.
In these areas, water or steam may be captured from natural hot springs and piped directly into radiators or heat exchangers.
The high temperatures and pressure of the magma steam were used to generate 36MW of electricity, making IDDP-1 the world's first magma-enhanced geothermal system.
GSHPs circulate a carrier fluid (usually a mixture of water and small amounts of antifreeze) through closed pipe loops buried in the ground.
As a result, the heat is pumped across a larger temperature difference and this leads to higher efficiency and lower energy use.
Geothermal energy supplied channeled district heating for baths and houses in Pompeii around 0 AD.
[18] In the first century AD, Romans conquered Aquae Sulis in England and used the hot springs there to feed public baths and underfloor heating.
[20] The world's oldest working geothermal district heating system in Chaudes-Aigues, France, has been operating since the 14th century.
[4] The earliest industrial exploitation began in 1827 with the use of geyser steam to extract boric acid from volcanic mud in Larderello, Italy.
In 1892, America's first district heating system in Boise, Idaho, was powered directly by geothermal energy, and was soon copied in Klamath Falls, Oregon in 1900.
The earliest one was probably Robert C. Webber's home-made 2.2 kW direct-exchange system, but sources disagree as to the exact timeline of his invention.
[23][24] Professor Carl Nielsen of Ohio State University built the first residential open loop version in his home in 1948.
[23] Since 2000, a compelling body of research has been dedicated to numerically evidence the advantages and efficiency of using CO2, alternative to water, as heat transmission fluid for geothermal energy recovery from enhanced geothermal systems (EGS) where the permeability of the underground source is enhanced by hydrofracturing.
[36] The design defined on the base of site-specific geological, hydrogeological and environmental knowledge prevent all these potential risks.
