Notes

eothermal Energy uses the heat that is continuously produced inside of our Earth to produce heat or electricity. Where does this heat come from? The core of the Earth is about as hot as the surface of our Sun, making it an important source of heat within the Earth. The decay of radioactive isotopes beneath the surface also contributes to geothermal heat. The molten magma caused by this heat either seeps out of the cracks in the Earth's surface, erupts out of a volcano, or remains below and heats the rocks and water trapped beneath the Earth. Hot springs and geysers, like Old Faithful, get their heat from geothermal energy that has made its way to the surface. Most water that has been heated by geothermal energy remains beneath the Earth's surface in geothermal reservoirs.

Geothermal energy was first used in hot springs. Indigenous people used them for bathing, cleaning and for cooking for thousands of years. In the 1800's these springs gained commercial use. In the mid 1800's hot springs gained popularity as spas and resorts.

In the first century AD, early Roman engineers discovered the potential of geothermal energy as an energy source for providing heat for their homes. In the city of Bath in the UK, Romans used hot springs to provide under-floor heating as well as public baths. These spas have been preserved and are visited each year by thousands of tourists.

The first district heating system was developed in 1892 and brought hot spring water to homes in Boise, Idaho. Just 12 years later, in 1904, an Italian businessman called Piero Ginori Conti invented the first geothermal power generator in Larderello, Italy. The following year the first geothermal power plant went into operation in Larderello. In 1913, the first commercial power plant was constructed in the same location. This plant used natural steam to generate power.

The improvement of the use of geothermal energy continued in the 1900s and became a focus in the 1970s during the Oil Crisis. The United States has had the largest growth and is currently leading the world in geothermal electricity production with around 3187 MW of installed capacity. U.S generation of geothermal power has grown by 20% since 2005. The Geothermal map shows where our geothermal resources are located. As of 2010, 24 countries are currently using geothermal energy as a source for power. Seventy countries have geothermal projects already in the works or in the planning stage. Still, geothermal energy accounts for less than 1% of the world's energy.

Even though geothermal resources are right under our feet, not all sites are cost effective. Developers search for sites where resources are abundant and close to the surface since they are more economical. Some of the best sources of geothermal energy are located in the area known as the Pacific Rim. This area is also known as the Ring of Fire and is home to more than three-fourths of the world's volcanoes and earthquakes.

Harvesting geothermal energy has very little negative impact on the environment. Geothermal power plants do not take up any more space than a traditional power plant and since they are built right on the hydrothermal resources there is no need to store or transport the resource. Geothermal power plants do release some carbon dioxide but this is significantly less than the amount released by a fossil fuel power plant with a similar capacity. Water is taken from the Earth to fuel geothermal power plants, but most is treated and then injected back into the Earth. Geothermal power plants cost about the same amount as coal power plants, making them more affordable than other forms of renewable energy.

Reflection Question
Look at a map of the Ring of Fire. In the United States, which states do you think might have abundant geothermal resources?