Need to know what geothermal energy is? We break down geothermal energy as a power source and its key benefits.
Harnessing the colossal energy at the Earth's core, geothermal energy represents an underutilized yet promising renewable energy resource. It's derived from the heat generated during the planet's initial formation and the radioactive decay of various materials. This thermal energy is stored in the rocks and fluids in the Earth's core, radiating outward, creating a continuous flow of heat from the center to the surface.
Put simply, geothermal energy is the heat from the Earth that we can harness and utilize for various purposes. The origins of the term Geothermal comes from the Greek "geo" and "thermos", which put together, equals Earth heat - pretty accurate definition!
Historically, geothermal energy has served humanity for thousands of years, warming homes, cooking food, and more. Today, this power drives electricity generation, and geothermal heat can also be used directly for heating and cooling applications. This is achieved through geothermal heat pumps, which leverage the constant temperatures below the Earth's surface. In winter, these pumps move heat from the ground into your house, and in the summer, they pull heat from your home and discharge it into the ground.
Geothermal heat pumps placed around 10 feet underground, use water or an antifreeze solution to harness the earth's heat. These systems help maintain comfortable temperatures in buildings year-round by absorbing the Earth's heat as the fluid circulates back into the structure.
Geothermal energy has also found uses in agriculture for heating greenhouses, residential and commercial district heating, and even melting snow on roads by pumping heated water beneath the pavement.
Harnessing geothermal energy involves a fascinating process that taps into the Earth's subsurface heat and transforms it into a usable form. To access geothermal power and turn it into energy, geothermal power plants have to tap into the Earth's underground heat and then consequently, convert that heat into electricity, usually through a process that involves steam. This process typically involves drilling into the Earth's crust, much like drilling for oil, to access reservoirs of hot water or steam trapped in porous rock or fractures.
Geothermal power plants then use this steam or hot water to drive a turbine connected to a generator, producing electricity. These power plants come in three main types: dry steam, flash, and binary cycle plants. Dry steam plants use steam directly from the ground, flash plants convert high-pressure hot water into steam, and binary plants transfer heat from geothermal water to a secondary fluid, which then turns into steam and drives the turbines.
This heat, or thermal energy, originates from two sources. For starters, there is the residual heat that's left over from the planet's formation around 4.5 billion years ago. The second source, which is ongoing, is the heat generated from the decay of naturally radioactive isotopes such as uranium, thorium, and potassium. To put it succinctly: geothermal energy comes from the residual heat from the planet's formation, and the ongoing decay of radioactive isotopes.
Amid the earth's core and its mind-boggling temperatures - which exceed 4000°C - rocks melt and form magma, a fluid of semi-liquid rock and dissolved gases. This extreme heat causes sections of the mantle to convect upwards, buoyed by their lighter weight compared to the surrounding rock. In addition, the Earth's crust houses rocks and water that can reach temperatures of around 370°C, and that is energy that can be harvested by geothermal plants, from the Earth's surface and all the way down to several miles below.
Tapping into geothermal resources involves drilling deep wells, sometimes over a mile, into underground reservoirs. These resources, either naturally occurring or enhanced via a process known as hydraulic stimulation, drive turbines linked to electricity generators.
The earliest record of geothermal heat for electricity production dates back to 1904 in Larderello, Italy. However, the therapeutic use of geothermal hot springs predates electricity generation, reaching back to the Palaeolithic Age and continues to this day in locations like Japan's hot springs where monkeys warm themselves during the frigid winter months.
Geothermal power plants come in three varieties; dry steam, flash, and binary. Dry steam plants, the earliest kind, harness steam directly from the ground fractures to drive a turbine. Flash plants, on the other hand, utilize high-pressure hot water from beneath the surface, cooled with lower pressure water to create steam, powering a turbine.
Finally, binary plants run hot water through a secondary fluid with a lower boiling point, vaporizing the secondary fluid, which in turn drives a turbine. Future geothermal power plants are projected to be predominantly binary plants. The United States tops the chart as the world’s largest producer of geothermal energy, boasting the most substantial geothermal development thanks to the The Geysers which are north of San Francisco, California.
Contrary to its name, "The Geysers" doesn't actually contain any actual geysers, and the energy harnessed is all steam, not hot water. Countries like Iceland, blessed with 25 active volcanoes and 600 hot springs, also generate 25% of their energy from geothermal sources, thanks to their five geothermal power plants.
For a deeper dive into geothermal power plants and how they work, check out our article on, "is geothermal energy renewable?"
Subscribe now for the latest trends, technology updates, and industry news.
