What Is Geothermal Power?

Geothermal power is sustainable energy generated by drawing heat up from beneath the Earth's surface and converting it into electricity using turbines, generators, and other standard power generating equipment.

Geothermal power is sustainable energy generated by drawing heat up from beneath the Earth’s surface and converting it into electricity using turbines, generators, and other standard power generating equipment. Geothermal power is widely promoted as a cost-effective and environmentally responsible alternative to energy produced by burning fossil fuels such as petroleum and coal and accounts for approximately 0.4% of all energy consumed in the United States.

A Short History Of Geothermal Power

Geothermal power has been harnessed by man since the Stone Age when hot springs were first used for bathing. The first known instance of civilization harnessing geothermal energy is from the 3rd century BCE when China’s Qin Dynasty directed the flow of an underground hot spring to fill a small stone pool at the same location where the Huaqing Chi palace was later built. In 1 AD, the first commercial use of geothermal energy occurred when the Romans used hot springs to feed public baths and for in-residence under-floor heating.

What Is Geothermal Heat?

Geothermal heat is generated deep inside the Earth’s core by the slow decay of radioactive particles. At its center, the Earth’s core is approximately 6,000°C, as hot as the surface of the sun. As you move away from the core and closer to the Earth’s surface, temperatures drop dramatically to about 200°C where the earth’s crust begins, at a depth of approximately 15 to 35 miles. As geothermal heat occurs naturally and is continuously being created inside the Earth, it is considered a carbon neutral renewable energy source.

How Is Geothermal Heat Harnessed?

Geothermal Heat Pump Diagram
Geothermal Heat Pump Diagram

Geothermal heat is harnessed using either direct geothermal energy or a geothermal heat pump. Direct geothermal energy heats buildings simply by pumping water from hot springs or a geothermal reservoir directly into a building. This basic method has been employed for thousands of years to facilitate tankless hot-water bathing and cooking. Geothermal heat pumps heat buildings indirectly by burying liquid-filled pipes several meters beneath the ground where the temperature is a constant 12°C. The liquid in the pipes is circulated, drawing heat up into a central heating system the redistributes the heat through the home. In the summer, the system cools the home using the exact same process.

How Is Geothermal Heat Converted Into Electricity?

Geothermal Power Station Diagram
Geothermal Power Station Diagram

Geothermal heat is converted into electricity by using a geothermal power station. A geothermal power station operates by digging a well deep into the Earth’s crust where it is very hot. Water is pumped into the well and rising steam spins an electricity generating steam turbine. The steam is cooled and converted back into water by a condenser and then pumped back into the well to start the process all over again. The deepest geothermal well to date was just in completed in 2019, in Falmouth, England. It is 5km deep and maintains a constant temperature of 195°C at its base. Geothermal power stations work similarly to biomass power stations but require no fuel to burn for heat. Producing zero emissions, they are better for the environment.

How Much Geothermal Power Is Being Generated?

In 2019, geothermal power accounted for 0.4% of all energy used in the United States, generating approximately 3.7GW. World-wide, approximately 15.4GW of geothermal electricity was generated, with Indonesia being the second-largest producer at 1.4GW.

Who Generates Geothermal Power?

The following companies generate geothermal power:

Berkshire Hathaway Renewables LogoBerkshire Hathaway Renewables
Geothermal power producer.
Calpine Energy Solutions LogoCalpine Energy Solutions
Geothermal power producer.
Northern California Power Agency LogoNorthern California Power Agency
Geothermal power producer.
Ormat Technologies LogoOrmat Technologies
Geothermal power producer.
Terra-Gen Power LogoTerra-Gen Power
Geothermal power producer.

What Is The Future of Geothermal Power?

Scientists expect that the knowledge and technology needed to drill down to 300°C will be developed in approximately 3 year’s time. However, the ultimate goal is to get down to a game-changing 500°C, which is expected to take up to 25 years more.

Geothermal Power In The News


Geothermal Electricity Producers: Berkshire Hathaway Renewables, Calpine Energy Solutions, Northern California Power Agency, Ormat Technologies, Reykjavik Geothermal, WaterFurnace

Jill is the Renewable Energy editor at Electric Guide and writes about the world-wide transition from fossil fuels to sustainability.  With a B.S. in Environmental Engineering from the Samueli School at UCI and having campaigned extensively for federal subsidization of affordable green housing, Jill is uniquely qualified to discuss the rapidly evolving renewables industry. Send tips and story ideas to Jill at: jill@electric.guide