GEOTHERMAL ENERGYTrapping the Earth’s Internal Heat

How is Geothermal Energy Generated?

• Temperatures hotter than the sun’s surface are continuously produced inside the earth by a slow decay of radioactive particles

• The most common method that scientists use to find geothermal reservoirs is drilling a deep well and testing the temperature deep underground.

• Steam or very hot water from deep within the earth is piped to the surface and used as a heat source or to produce electricity.

• Earth’s kinetic energy is converted into electricity.

Energy Efficient and Cost Effective

• According to the EPA, geothermal are the most energy efficient, cost effective, and environmentally clean systems for temperature control

Uses and Goals

• Heat pumps – heat and cool building; melt snow from roads and sidewalks

• Direct use applications – greenhouses, heat water for fish farming, pasteurize milk, food dehydration, gold mining

• Power plants – produce electricity

• Help mitigate global warming

How is Geothermal Energy Generated?

• Temperatures hotter than the sun’s surface are continuously produced inside the earth by a slow decay of radioactive particles

• People around the world use geothermal energy to produce electricity and heat their homes by digging deep wells and pumping the heated water or steam to the surface

Where is Geothermal Energy Found?

• Found along major plate boundaries where earthquakes and volcanoes are concentrated– Geysers– Hot springs– Fumaroles– Geothermal reservoirs

The Ring of Fire

The US and Geothermal Energy

• Most of the geothermal reservoirs in the U.S. are located in the western states, Alaska and Hawaii.

• California generates the most electricity from geothermal energy.

• "The Geysers" dry steam reservoir in northern California is the largest known dry steam field in the world and has been producing electricity since 1960.

• 7 states have geothermal power plants• In 2008 U.S. geothermal power plants produced 0.4%

of total electricity in the United States.

Geothermal Energy is the U.S.

Iceland

• Iceland plans to run its entire economy on renewable hydropower, geothermal energy, and wind; and use these sources to produce hydrogen gas for running all of its motor vehicles and ships by the year 2050.

Geothermal Power Plants

• Require high temperatures (300 F – 700 F) hydrothermal resources that may either come from dry steam wells or hot water wells

• There are three types of geothermal power plants: dry steam plants, flash steam plants, and binary cycle power plants

Dry Steam Plants

• Use steam piped directly from a geothermal reservoir to turn the turbogenerator

Flash Steam Plants

• Takes high pressure hot water from deep inside the earth and converts it to steam to drive the generator turbines

• When the steam cools it condenses into water and is injected into the earth to be used over and over again.

• Most geothermal plants are flash steam plants

Flash Steam Power Plants are the most common form of geothermal power plant. The hot water is pumped under great pressure to the surface. When it reaches the surface the pressure is reduced and as a result some of the water changes to steam. This produces a ‘blast’ of steam. The cooled water is returned to the reservoir to be heated by geothermal rocks again.

Binary Cycle Power Plants

• Transfers the heat from geothermal hot water to another liquid.

• The heat causes the second liquid to turn to steam which is used to drive a generator turbine.

Geothermal Power Plant Piping

Geothermal Power Plants and the Environment

• Geothermal power plants do not burn fuel to generate electricity so their emission levels are very low

• Release less that 1% of carbon dioxide emissions of a fossil fuel plant

• Use scrubber systems to clean the air of hydrogen sulfide

• Emits 97% less acid rain-causing sulfur compounds than fossil fuel plants

Advantages

• Very high efficiency/high net yield• Very reliable (runs 24 hrs. a day)• Very clean – no air pollution or GHGs• Renewable and sustainable• Conserves fossil fuels• Can help decrease dependence of foreign oil• No transportation involved

Disadvantages

• Can’t provide our current energy needs• Can only be used in certain geologically active

areas• Water contains minerals that can be corrosive

and difficult to dispose of safely• Harmful gases can escape from deep within the

earth• Piping system requires large areas of land• Initial costs can be high