Geothermal

Geothermal energy is heat derived from the Earth’s interior. It can be captured for heating or converted into electricity. The resource ranges from near-surface ground heat to deep high-temperature reservoirs.

Near-surface low-temperature resources are exploited with ground-source heat pumps and direct-use applications like heating buildings and greenhouses.

High-temperature resources allow electricity generation through hydrothermal systems, dry-steam and flash-steam plants, or through enhanced geothermal systems (EGS) which improve permeability and circulation in hot but dry rock.

Direct-use and district heating: hot water from reservoirs is piped to facilities, greenhouse heating, aquaculture, and industrial processes.

Geographic distribution: geothermal resources are concentrated around tectonic plate boundaries and volcanic regions; major producers include the United States, Indonesia, the Philippines, Iceland, New Zealand, Italy, Japan, Mexico, Turkey, and Kenya.

Environmental and social aspects: emissions are typically low, but some plants release hydrogen sulfide and other gases; water management, land use, and potential induced seismicity with certain designs; reservoir pressure is maintained by reinjection of spent fluids.

Economics and policy: capital-intensive upfront costs and long development times affect competitiveness; high capacity factors can improve economics; incentives, feed-in tariffs, and renewable portfolio standards influence deployment.

History: Geothermal applications date to ancient times for direct heating; electricity generation began in 1904 at Larderello, Italy, and global development expanded through the 20th century.