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.
Energy development is the field of activities focused on obtaining sources of energy from natural resources. These activities include the production of renewable, nuclear, and fossil fuel derived sources of energy, and for the recovery and reuse of energy that would otherwise be wasted. Energy conservation and efficiency measures reduce the demand for energy development, and can have benefits to society with improvements to environmental issues.
Geothermal gradient is the rate of change in temperature with respect to increasing depth in Earth's interior. As a general rule, the crust temperature rises with depth due to the heat flow from the much hotter mantle; away from tectonic plate boundaries, temperature rises in about 25–30 °C/km (72–87 °F/mi) of depth near the surface in the continental crust. However, in some cases the temperature may drop with increasing depth, especially near the surface, a phenomenon known as inverse or negative geothermal gradient. The effects of weather, the Sun, and season only reach a depth of roughly 10–20 m (33–66 ft).
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.
Renewable energy in Australia is mainly based on biomass, solar, wind, and hydro generation. Over a third of electricity is generated from renewables, and is increasing, with a target to phase out coal power before 2040. Wind energy and rooftop solar have particularly grown since 2010. The growth has been stimulated by government energy policy in order to limit the rate of climate change in Australia that has been brought about by the use of fossil fuels. Pros and cons of various types of renewable energy are being investigated, and more recently there have been trials of green hydrogen and wave power.
Iceland is a world leader in renewable energy. 100% of Iceland's electricity grid is produced from renewable resources. In terms of total energy supply, 85% of the total primary energy supply in Iceland is derived from domestically produced renewable energy sources. Geothermal energy provided about 65% of primary energy in 2016, the share of hydropower was 20%, and the share of fossil fuels was 15%.
Geothermal energy was first used for electric power production in the United States in 1960. The Geysers in Sonoma and Lake counties, California was developed into the largest geothermal steam electrical plant in the world, at 1,517 megawatts. Other geothermal steam fields operate in the western US and Alaska.
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.
The Cooper Basin is a Permian-Triassic sedimentary geological basin in Australia. The intracratonic rift basin is located mainly in the southwestern part of Queensland and extends into northeastern South Australia. It is named after the Cooper Creek which is an ephemeral river that runs into Lake Eyre. For most of its extent, it is overlain by the Eromanga Basin. It covers 130,000 km2.
Geothermal energy is a significant part of renewable energy in Turkey: it is used for geothermal heating and generates 3% of the nation's electricity. Turkey is the world's second largest user of geothermal heating, after China. Many greenhouses, spas and homes are heated by underground water; and many more buildings could be heated in this way.
Queensland's energy policy is based on the year 2000 document called the Queensland Energy Policy: A Cleaner Energy Strategy. The Queensland Government assists energy development through the Department of Energy and Water Supply. The state is noted for its significant contribution to coal mining in Australia. The primary fuel for electricity generation in the state is coal with coal seam gas becoming a significant fuel source. Queensland has 98% of Australia's reserves of coal seam gas. An expansion of energy-intensive industries such as mining, economic growth and population growth have created increased demand for energy in Queensland.
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.
Geothermal energy is the second most used form of renewable energy in Russia but represents less than 1% of the total energy production. The first geothermal power plant in Russia, which was the first Binary cycle power station in the world, was built at Pauzhetka, Kamchatka, in 1966, with a capacity of 5 MW. The total geothermal installed capacity is 81.9 MW, with 50 MW coming from a plant at Verkhne-Mutnovsky.Two other plants were built on the Kamchatka Peninsula in 1999 and 2002. Two smaller additional plants were installed on the islands of Kunashir and Iturup in 2007. Most geothermal resources are currently used for heating settlements in the North Caucasus and Kamchatka. Half of the geothermal production is used to heat homes and industrial buildings, one third is used to heat greenhouses and 13% is used for industrial processes.
United Downs Deep Geothermal Power is the United Kingdom's first geothermal electricity project. It is situated near Redruth in Cornwall, England. It is owned and operated by Geothermal Engineering (GEL), a private UK company. The drilling site is on the United Downs industrial estate, chosen for its geology, existing grid connection, proximity to access roads and limited impact on local communities. Energy is extracted by cycling water through a naturally hot reservoir and using the heated water to drive a turbine to produce electricity and for direct heating. The company plans to begin delivering electricity (2MWe) and heat (<10MWth) in 2024. A lithium resource was discovered in the well.
South Australia is a leader in utility-scale renewable energy generation, and also produces gas and uranium for electricity generation. Gas production is mostly concentrated in the Cooper Basin in the state's north-east. Gas is delivered from these fields by pipeline to users interstate and to Port Adelaide where it fuels three separate gas-fired power plants. Uranium is also mined in South Australia, though nuclear power generation is prohibited nationally. The Olympic Dam mine is the world's single largest known deposit of uranium and represents 30% of the world's total uranium resource. Many utility-scale wind farms and solar farms have been commissioned during the 21st century and geology with potential for geothermal energy has also been identified but is yet to be developed.
Most of Kenya's electricity is generated by renewable energy sources. Access to reliable, affordable, and sustainable energy is one of the 17 main goals of the United Nations’ Sustainable Development Goals. Development of the energy sector is also critical to help Kenya achieve the goals in Kenya Vision 2030 to become a newly industrializing, middle-income country. With an installed power capacity of 2,819 MW, Kenya currently generates 826 MW hydroelectric power, 828 geothermal power, 749 MW thermal power, 331 MW wind power, and the rest from solar and biomass sources. Kenya is the largest geothermal energy producer in Africa and also has the largest wind farm on the continent. In March 2011, Kenya opened Africa's first carbon exchange to promote investments in renewable energy projects. Kenya has also been selected as a pilot country under the Scaling-Up Renewable Energy Programmes in Low Income Countries Programme to increase deployment of renewable energy solutions in low-income countries. Despite significant strides in renewable energy development, about a quarter of the Kenyan population still lacks access to electricity, necessitating policy changes to diversify the energy generation mix and promote public-private partnerships for financing renewable energy projects.
Renewables supply a quarter of energy in Turkey, including heat and electricity. Some houses have rooftop solar water heating, and hot water from underground warms many spas and greenhouses. In parts of the west hot rocks are shallow enough to generate electricity as well as heat. Wind turbines, also mainly near western cities and industry, generate a tenth of Turkey’s electricity. Hydropower, mostly from dams in the east, is the only modern renewable energy which is fully exploited. Hydropower averages about a fifth of the country's electricity, but much less in drought years. Apart from wind and hydro, other renewables; such as geothermal, solar and biogas; together generated almost a tenth of Turkey’s electricity in 2022. Türkiye has ranked 5th in Europe and 12th in the world in terms of installed capacity in renewable energy. The share of renewables in Türkiye’s installed power reached to 54% at the end of 2022.
The Yangbajain Geothermal Field (羊八井地热田) is a geothermal field near the town of Yangbajain in Damxung County, Tibet Autonomous Region, China. The fluid is heated by magmatic activity not far below the surface. It is a tourist attraction and also supplies steam to a major power plant with 25 MW capacity.
