An overview of geothermal energy technologies

Marcelo Guarido, David J. Emery, Daniel O. Trad, Kristopher A. Innanen

Geothermal resources have been used by hominids since prehistoric times for bathing, curing wounds, and tempering hunting weapons. Even religious connections are observed in old civilizations. District heating application appeared in France during the 15th century, while the first power plant was installed in Larderello, Italy, in 1913. Since then, power plant technologies and optimized geothermal resources are studied for large-scale renewable energy generation. Power plants require water temperature ranging from 95°C to over 200°C. Hydrothermal resources, presenting manifestations in the surface as geysers, hot springs, and fumaroles, can provide water or steam over 150°C. With crust’s gradient temperature averaged as 30°C/km, resources in dry rock systems come from 3 to 7 km depth. But the gradient varies on the crust, and some areas are more suitable for implementation of Enhanced Geothermal Systems of closed-loop systems. With over 458,000 wells connected to the oil and gas industry, Alberta, Canada, has a high potential to reuse part of those wells, around 7,900 wells, for electricity generation if converted to EGS or closed loop. SE and E areas of the province showed the potential to reach electricity generation temperatures at depths lower than 1 km.