Steam Power

Earth’s core is about as hot as the sun’s surface. It’s so hot that it melts the rock above it into a liquid called magma. That’s a lot of heat! Energy made by using Earth’s heat is called geothermal energy. Some areas in the United States are able to use geothermal energy as a source of power. In California, The Geysers power plant uses it to make enough electricity for 725,000 homes. They do it with steam.

Steam to Electricity

The Geysers is the world’s largest geothermal field. It is in the Mayacamas Mountains, in an area where magma is closer to the surface. The magma’s heat boils water that collects underground. The boiling water makes steam, and the steam is trapped in rock layers. The Geysers drilled 319 wells to reach it! The areas where the wells reach the steam is called the steam field. How much steam flows out of the steam field? About twelve and a half million pounds per hour!

John Avery is an engineer who has worked at The Geysers for more than twenty years. He explained how it works: “The steam comes out like steam from a tea kettle. Except instead of steam just coming out of the kettle, we have pipelines that take it to the power plants.” All that steam flows into turbines in 13 power plants. The turbines are connected to generators. The steam spins the turbines. The turbines turn the generators, making electricity. Then the steam goes into cooling towers. Cooling the steam turns it back into water. The water is returned to the ground.

A Cleaner Form of Power

Other kinds of power plants also use steam to create electricity, but they make steam by burning fuel, such as coal. Burning coal and other fuels like it causes pollution and releases the greenhouse gasses that cause climate change. The Geysers use steam that’s already in the ground, so its power plants don’t need to burn fuel. It’s a cleaner form of energy that creates little pollution.

The Geysers also recycles. The underground water that becomes steam needs to be refilled so the steam can keep flowing. Some of that water comes from turning the steam back into water in the cooling towers. But The Geysers also takes treated wastewater from nearby towns. How much recycled wastewater do they use? About 20 million gallons per day!

Good for Some But Not for All

If geothermal energy is cleaner, why don’t we use it everywhere? John Avery explained that geothermal power plants like The Geysers “can only occur in certain places that have heat and water and a certain type of rock.” Not all rock lets water and steam flow through it. Plus, those three things need to be close enough to the surface to reach by drilling. “Ours is only two miles deep,” he said. The farther a company has to drill, the more it costs.

But in places where heat, water, and the right kind of rock can be reached, geothermal energy can be a good source of power. California, Nevada, Utah, Oregon, Idaho, New Mexico, and Hawaii all have at least one geothermal power plant. Around the world, geothermal energy is used in parts of Indonesia, the Philippines, Japan, New Zealand, Mexico, Italy, and Kenya. Geothermal energy can’t power the whole world, but every bit of cleaner energy helps.