Editing Geothermal energy (section)

==Types==

=== Hydrothermal systems ===
Hydrothermal systems produce geothermal energy by accessing naturally-occurring hydrothermal reservoirs. Hydrothermal systems come in either ''vapor-dominated'' or ''liquid-dominated'' forms.

==== Vapor-dominated plants ====
Larderello and The Geysers are vapor-dominated. Vapor-dominated sites offer temperatures from 240 to 300&nbsp;°C that produce superheated steam.

==== Liquid-dominated plants ====
Liquid-dominated reservoirs (LDRs) are more common with temperatures greater than {{convert|200|C}} and are found near volcanoes in/around the Pacific Ocean and in rift zones and hot spots. Flash plants are the common way to generate electricity from these sources. Steam from the well is sufficient to power the plant. Most wells generate 2–10 MW of electricity. Steam is separated from liquid via cyclone separators and drives electric generators. Condensed liquid returns down the well for reheating/reuse. As of 2013, the largest liquid system was [[Cerro Prieto]] in Mexico, which generates 750 MW of electricity from temperatures reaching {{convert|350|C|F}}.

Lower-temperature LDRs (120–200&nbsp;°C) require pumping. They are common in extensional terrains, where heating takes place via deep circulation along faults, such as in the Western US and Turkey. Water passes through a [[heat exchanger]] in a [[Rankine cycle]] binary plant. The water vaporizes an organic working fluid that drives a [[turbine]]. These binary plants originated in the Soviet Union in the late 1960s and predominate in new plants. Binary plants have no emissions.<ref name=sci2013/><ref name=eere>{{cite web|url=http://www1.eere.energy.gov/geothermal/low_temperature_resources.html
|title= Low-Temperature and Co-produced Geothermal Resources |publisher=US Department of Energy}}</ref>

=== Engineered geothermal systems ===
An engineered geothermal system is a geothermal system that engineers have artificially created or improved. Engineered geothermal systems are used in a variety of geothermal reservoirs that have hot rocks but insufficient natural reservoir quality, for example, insufficient geofluid quantity or insufficient rock permeability or porosity, to operate as natural hydrothermal systems. Types of engineered geothermal systems include ''enhanced geothermal systems'', ''closed-loop or advanced geothermal systems'', and some ''superhot rock geothermal systems''.<ref name="auto">{{Cite web |title=Superhot Rock Energy Glossary |url=https://www.catf.us/superhot-rock/glossary/ |access-date=2023-11-29 |website=Clean Air Task Force |language=en}}</ref>

==== Enhanced geothermal systems ====
{{Main|Enhanced geothermal system}}
Enhanced geothermal systems (EGS) actively inject water into wells to be heated and pumped back out. The water is injected under high pressure to expand existing rock fissures to enable the water to flow freely. The technique was adapted from oil and gas [[fracking]] techniques. The geologic formations are deeper and no toxic chemicals are used, reducing the possibility of environmental damage. Instead [[proppant]]s such as sand or ceramic particles are used to keep the cracks open and producing optimal flow rates.<ref>{{Cite web |date=2023-03-16 |title=When Fracturing for Geothermal, Is Proppant Really Necessary? |url=https://jpt.spe.org/when-fracturing-for-geothermal-is-proppant-really-necessary |access-date=2024-02-11 |website=JPT |language=en}}</ref> Drillers can employ [[directional drilling]] to expand the reservoir size.<ref name=sci2013/>

Small-scale EGS have been installed in the [[Rhine Graben]] at [[Soultz-sous-Forêts]] in France and at [[Landau]] and [[Insheim]] in Germany.<ref name=sci2013/>

==== Closed-loop geothermal systems ====
{{Main|Closed-loop geothermal}}

Closed-loop geothermal systems, sometimes colloquially referred to as Advanced Geothermal Systems (AGS), are engineered geothermal systems containing subsurface working fluid that is heated in the hot rock reservoir without direct contact with rock pores and fractures. Instead, the subsurface working fluid stays inside a closed loop of deeply buried pipes that conduct Earth's heat. The advantages of a deep, closed-loop geothermal circuit include: (1) no need for a geofluid, (2) no need for the hot rock to be permeable or porous, and (3) all the introduced working fluid can be recirculated with zero loss.<ref name="auto" /> [[Eavor Technologies|Eavor<sup>tm</sup>]], a Canadian-based geothermal startup, piloted their closed-loop system in shallow soft rock formations in Alberta, Canada. Situated within a sedimentary basin, the geothermal gradient proved to be insufficient for electrical power generation. However, the system successfully produced approximately 11,000 MWh of thermal energy during its initial two years of operation."<ref name=":5" /><ref>{{Cite web |last=Toews |first=Mathew |date=January 11, 2020 |title=Eavor-Lite Demonstration Project |url=https://albertainnovates.ca/wp-content/uploads/2022/08/2506-G2019000423-Eavor-Final-Public-Report-Jan-2021.pdf}}</ref>