Heat from the earth can be used in many ways, from utility-grade power stations to simple heat pumps for residential applications. This heat energy, known as geothermal energy, is a renewable source that can be found almost anywhere worldwide.
The heat continuously flowing from the earth's interior is estimated to be the equivalent of 42 million megawatts of power (which is equivalent to the electricity that would be used by more than 30 billion homes).
Tapping geothermal energy is a clean and affordable way to generate electricity and heat and avoid the use of fossil fuels.
Under the earth's crust is a layer of hot and molten rock called magma. Heat is continuously produced there, mostly from stored heat, friction, and the decay of naturally radioactive elements such as uranium and potassium.
The amount of heat within 33,000 feet of the earth's surface contains 50,000 times more energy than all of the oil and natural gas resources in the world!
The most common way of extracting energy from geothermal sources is to tap into naturally occurring hydrothermal convection systems where cooler water seeps into the earth's crust and is heated up before rising to the surface.
Geothermal power plants drill holes into this heated rock to capture this naturally created steam and then use the steam to drive a traditional turbine/generator system to create electricity. Geothermal fluid temperatures should be at least 300 degrees Fahrenheit, although geothermal plants are operating on fluid temperatures as low as 210 degrees Fahrenheit.
There are three main designs for geothermal power plants: dry steam, flash, and binary cycle. The ideal type of system for any particular site depends on temperature, depth, and the quality of the water and steam in the area. All three systems take hot water and steam from the ground, use the steam to generate electricity, and then return the warm water into the ground to prolong the life of the heat source.
Geothermal power plants are currently generating electricity in over 24 countries worldwide with a total output of about 8.9 gigawatts (which is enough electricity to power more than 6 million homes). The United States is the world's largest geothermal energy producer with output of about 2.8 gigawatts.
Geothermal power plants require capital-intensive technology. These power plants don't.
