Geothermal energy is thermal energy extracted from the Earth's crust. It combines energy from the formation of the planet and from radioactive decay. Geothermal energy has been exploited as a source of heat and/or electric power for millennia.
Geothermal heating is the direct use of geothermal energy for some heating applications. Humans have taken advantage of geothermal heat this way since the Paleolithic era. Approximately seventy countries made direct use of a total of 270 PJ of geothermal heating in 2004. As of 2007, 28 GW of geothermal heating capacity is installed around the world, satisfying 0.07% of global primary energy consumption. Thermal efficiency is high since no energy conversion is needed, but capacity factors tend to be low since the heat is mostly needed in the winter.
A ground source heat pump is a heating/cooling system for buildings that use a type of heat pump to transfer heat to or from the ground, taking advantage of the relative constancy of temperatures of the earth through the seasons. Ground-source heat pumps (GSHPs) – or geothermal heat pumps (GHP), as they are commonly termed in North America – are among the most energy-efficient technologies for providing HVAC and water heating, using far less energy than can be achieved by burning a fuel in a boiler/furnace or by use of resistive electric heaters.
Rosemanowes Quarry, near Penryn, Cornwall, England, was a granite quarry and the site of an early experiment in extracting geothermal energy from the earth using hot dry rock (HDR) technology.
The potential for exploiting geothermal energy in the United Kingdom on a commercial basis was initially examined by the Department of Energy in the wake of the 1973 oil crisis. Several regions of the country were identified, but interest in developing them was lost as petroleum prices fell. Although the UK is not actively volcanic, a large heat resource is potentially available via shallow geothermal ground source heat pumps, shallow aquifers and deep saline aquifers in the mesozoic basins of the UK. Geothermal energy is plentiful beneath the UK, although it is not readily accessible currently except in specific locations.
Geothermal energy in the United States was first used for electric power production in 1960. The Geysers in Sonoma and Lake counties, California was developed into what is now the largest geothermal steam electrical plant in the world, at 1,517 megawatts. Other geothermal steam fields are known in the western United States and Alaska. Geothermally generated electric power can be dispatchable to follow the demands of changing loads. Environmental impact of this energy source includes hydrogen sulfide emissions, corrosive or saline chemicals discharged in waste water, possible seismic effects from water injection into rock formations, waste heat and noise.
The Geysers is the world's largest geothermal field, containing a complex of 18 geothermal power plants, drawing steam from more than 350 wells, located in the Mayacamas Mountains approximately 72 miles (116 km) north of San Francisco, California.
An enhanced geothermal system (EGS) generates geothermal electricity without natural convective hydrothermal resources. Traditionally, geothermal power systems operated only where naturally occurring heat, water, and rock permeability are sufficient to allow energy extraction. However, most geothermal energy within reach of conventional techniques is in dry and impermeable rock. EGS technologies expand the availability of geothermal resources through stimulation methods, such as 'hydraulic stimulation'.
Geothermal power is electrical power generated from geothermal energy. Technologies in use include dry steam power stations, flash steam power stations and binary cycle power stations. Geothermal electricity generation is currently used in 26 countries, while geothermal heating is in use in 70 countries.
Canada has substantial potential for geothermal energy development. To date, development has all been for heating applications. Canada has 103,523 direct use installations as of 2013. There is currently no electricity being generated from geothermal sources in Canada although substantial potential exists in the Canadian Cordillera. The most advanced project exists as a test geothermal-electrical site at the Mount Meager massif in British Columbia, where a 100 MegaWatt (MW) facility could be developed. Potential for enhanced geothermal energy systems (EGS) exists throughout Canada. There are six geothermal power and two direct use projects listed with the Canadian Geothermal Energy Association.
The Iceland Deep Drilling Project (IDDP) is a geothermal project established in 2000 by a consortium of the National Energy Authority of Iceland (Orkustofnun/OS) and four of Iceland's leading energy companies: Hitaveita Suðurnesja (HS), Landsvirkjun, Orkuveita Reykjavíkur and Mannvit Engineering. The consortium is referred to as "Deep Vision".
AltaRock Energy Inc. is a privately held corporation that focuses on the development of geothermal energy resources and enhanced geothermal systems (EGS). It is headquartered in Seattle, Washington and has a technology development office in Sausalito, California. AltaRock has filed patent applications and holds exclusive licenses for related intellectual property related to EGS. In 2008 it started its first project near The Geysers in California to demonstrate the ability of EGS to be a reliable, renewable and clean source for the production of electric power.
The latest study of Massachusetts Institute of Technology "The Future of Geothermal Energy – Impact of Enhanced Geothermal Systems (EGS) on the United States in the 21st Century" (2006) points out the essential importance of developing an economical deep geothermal boring technology. With current boring technologies, bore price rises exponentially with depth. Thus, finding a boring technology with which the bore price rise would be approximately linear with increasing bore depth is an important challenge.
Plasma deep drilling technology is one of several drilling technologies that may be able to replace conventional, contact-based rotary systems. These new technologies include plasma deep drilling, water jet, hydrothermal spallation and laser. Companies that embrace plasma-drilling method include GA Drilling, headquartered in Bratislava, Slovakia.
Research Centre for Deep Drilling is high-tech laboratory focused on research and development of new deep drilling concept based on electrical plasma. It was established by GA Drilling, former Geothermal Anywhere company in the premises of Slovak Academy of Sciences in Bratislava, Slovakia. The Research centre was officially opened on 10 October 2010 as a result of long-term activities whose aim is to support the geothermal technology research and development in Slovakia. In October 2012, GA Drilling officially moved from Research Center for Deep Drilling to newly founded GA Drilling Technology Center.
Hot dry rock (HDR) is an extremely abundant source of geothermal energy that is difficult to access. A vast store of thermal energy is contained within hot – but essentially dry and impervious crystalline basement rocks found almost everywhere deep beneath Earth's surface. A method for the extraction of useful amounts of geothermal energy from HDR originated at the Los Alamos National Laboratory in 1970, and Laboratory researchers were awarded a US patent covering it.
Solar augmented geothermal energy (SAGE) is an advanced method of geothermal energy that creates a synthetic geothermal storage resource by heating a natural brine with solar energy and adding enough heat when the sun shines to generate power 24 hours a day. The earth is given enough energy in one hour to provide all electrical needs for a year. Available energy is not the issue, but energy storage is the problem and SAGE creates effective storage and electrical power delivery on demand. This technology is especially effective for geothermal wells that have demonstrated inconsistent heat or idle oil or gas fields that have demonstrated the proper geology and have an abundance of solar.
Frontier Observatory for Research in Geothermal Energy (FORGE) is a US government program supporting research into geothermal energy. The FORGE site is near Milford, Utah, funded for up to $140 million. As of 2023, numerous test wells had been drilled, and flux measurements had been conducted, but energy production had not commenced.
Fervo Energy is an energy resource company focused on harnessing heat through enhanced geothermal systems (EGS). It was co-founded in 2017 by Tim Latimer, a mechanical engineer who worked as a drilling engineer at BHP until 2015. His departure from the oil and gas sector was driven by a desire to apply techniques observed during the shale revolution to geothermal extraction.
