Geothermal energy is heat sourced from within the Earth, continuously produced beneath our feet. This warmth stems from the planet’s formation and radioactive decay. Humanity’s journey to understand and harness this power for various uses, from simple warmth to complex electricity generation, spans a long history.
Ancient Origins
Human interaction with geothermal energy began in prehistoric times. Early civilizations utilized naturally occurring hot springs. Archaeological evidence suggests that indigenous peoples in North America used hot springs over 10,000 years ago for bathing, cooking, medicinal purposes, and as neutral gathering places for different tribes. These natural thermal waters were often considered sacred, offering healing and spiritual rejuvenation.
Similarly, the ancient Romans developed sophisticated uses for geothermal resources, constructing public baths, known as “thermae,” as early as 200 BCE. These bathhouses were centers for hygiene, relaxation, and social interaction, often heated by natural hot springs or through innovative underfloor heating systems. In Japan, the tradition of “onsen,” or hot spring baths, dates back at least to the 6th century CE, with Buddhist monks playing a role in popularizing communal bathing for purification and healing. Even in Iceland, Vikings utilized natural hot springs for bathing and heating homes.
Pioneering Industrial Use
Harnessing geothermal energy for industrial purposes and electricity generation marked a turning point. The first documented industrial use began in Larderello, Tuscany, Italy, in 1818. Here, the French engineer Francesco Giacomo Larderel pioneered a method to extract boric acid from volcanic mud and hot springs, using geothermal steam as a heat source to evaporate water. This innovative process led to the establishment of a thriving chemical industry in the region, which was later renamed Larderello in his honor.
Geothermal electricity generation began in Larderello with Prince Piero Ginori Conti. On July 4, 1904, Conti successfully experimented with the first geothermal power generator, which utilized steam from the Larderello dry steam field to power a dynamo. This experimental 10-kilowatt generator demonstrated the feasibility of converting the Earth’s heat into electrical power. Following this success, the world’s first commercial geothermal power plant, Larderello 1, began operation in 1913. This plant, with an initial capacity of 250 kilowatts, provided electricity for the Italian railway system and nearby villages, establishing Italy as the sole industrial producer of geothermal electricity for decades.
Modern Advancements
Geothermal technology has continuously evolved and diversified. The initial dry steam power plants, like those at Larderello and later at The Geysers in California, directly utilize steam from underground reservoirs to turn turbines. As technology progressed, flash steam power plants became prevalent, converting high-pressure hot water into steam by reducing its pressure, which then drives turbines. These flash steam systems are currently the most common type globally.
A more recent advancement is the binary cycle power plant, which can operate efficiently with lower-temperature geothermal resources, typically between 225°F and 360°F. These plants use the geothermal heat to vaporize a secondary working fluid, which has a lower boiling point than water, and the resulting vapor turns a turbine in a closed-loop system. This innovation has broadened the geographic potential for geothermal energy development. Beyond electricity generation, geothermal energy is now used for district heating systems, warming entire communities, as seen in places like Boise, Idaho, since 1892, and extensively in Iceland. It also supports various industrial processes, agricultural applications like greenhouse heating, and residential heating and cooling through geothermal heat pumps.