Geothermal energy basics

Introduction

Geothermal energy refers to power extracted from heat stored in the Earth. Where does this heat originate from? It all started long, long time ago when our planet originally started its formation, from radioactive decay beneath the Earth's surface, volcanic activity, and also from solar energy that was absorbed at the surface. The first geothermal energy use was for bathing, but today geothermal energy is mostly used to generate electricity, and in some countries also for heating purposes in form of geothermal heating.

What's good about geothermal energy?

Geothermal energy is renewable energy source that cannot be depleted since earth is in constant state of producing heat, and it does not produce harmful carbon emissions nor it contributes to air pollution like fossil fuels (coal, oil, and natural gas do). Geothermal energy is clean, cost effective, reliable, sustainable, and environmentally friendly source of energy. Unlike solar and wind energy geothermal energy doesn't suffer from intermittency issue, and once built geothermal power plants offer extremely reliable clean energy solution.

What's not good about geothermal energy?

High installation costs are probably the first thing when talking about the cons of renewable energy. Geothermal power plants are very expensive to be built costing twice as much compared to natural gas power plants. High construction and drilling costs are the main reason why geothermal energy isn't economically viable option in all corners of the world, but only in areas with suitable amount of hot rocks at just the right depth for drilling. Once the drilling technologies become more technologically advanced geothermal energy will likely become much more competitive to fossil fuels.

Geothermal energy on global scale

Geothermal energy is renewable energy sector that is quickly expanding, and in the last couple of years global geothermal capacity has increased by more than 20%, with around 10,715 megawatts (MW) of geothermal capacity installed worldwide. 10,715 megawatts (MW) projects growth to 18,500 MW by 2015.

Geothermal energy in United States

United States is global leader in installed geothermal energy capacity with 3,086 MW of installed capacity coming from 77 geothermal power plants. California is the nation's leader with more than 2500 MW of geothermal energy production capacity but Nevada is quickly closing the gap. The first U.S. geothermal power plant was opened at The Geysers in California in 1960. According to current estimates installed geothermal capacity in the United States could exceed 15,000 MW by 2025.

Geothermal power plants

Three basic types of geothermal power plants are:
1.dry steam plants where steam is piped directly from a geothermal reservoir to turn the generator turbines.
2.flash steam plants that takes the high-pressured hot water from deep inside the Earth and convert it to steam to turn the generator turbines.
3.binary cycle power plants that transfer the heat from geothermal hot water to another liquid, and then the second liquid is turned into the steam that turns the generator turbines.

Geothermal energy environmental impact

As said before geothermal energy is environmentally friendly source of energy. Existing geothermal electric plants emit an average of 122 kilograms (269 lb) of CO2 per megawatt-hour (MW·h) of electricity, an amount negligible compared to fossil fuel power plants. Harnessing geothermal energy has minimal land and freshwater requirements. The only potential hazard is the fact that fluids drawn from the deep earth carry a mixture of gases, such as carbon dioxide (CO2), hydrogen sulfide (H2S), methane (CH4) and ammonia which can (if not treated properly) add to global warming, air pollution, and acid rain.