Geo-thermal power plants use Geo-thermal resources of earth surface that have both water (hydro) and heat (thermal). At first we should know that –WHAT IS A GEOTHERMAL RESOURCE?
Geo-thermal resources are natural reservoirs of hot water that exist at varying temperatures and depths below the Earth’s surface. Deep wells can be drilled into underground reservoirs to tap steam and very hot water that can be brought to the surface for use in a variety of applications, including electricity generation, direct use, and heating and cooling.
Geothermal power plants require high-temperature (300°F to 700°F) hydrothermal resources that come from either dry steam wells or from hot water wells. People use these resources by drilling wells into the earth and then piping steam or hot water to the surface. The hot water or steam powers a turbine that generates electricity. Some geothermal wells are up to two miles deep.
History of Geothermal Energy
Many ancient peoples used hot mineral springs for bathing, cooking, and heating. Water from hot springs is now used world-wide, for heating buildings, and for agricultural and industrial uses. Many people believe hot mineral springs have natural healing powers.
The first attempt to develop geothermal power in the United States came in 1922 at The Geysers steam field in northern California. The project failed because the pipes and turbines of the day could not stand up to the abrasion and corrosion of the particles and impurities that were in the steam. Later, a small but successful hydrothermal plant opened at the Geysers in 1960. Today 28 plants are operating there.
Electricity is now produced worldwide from geothermal energy in 21 countries,
Types of geothermal power plants-
There are three basic types of geothermal power plants:
Dry steam plants use steam directly from a geothermal reservoir to turn generator turbines. The first geothermal power plant was built in 1904 in Tuscany, Italy, where natural steam erupted from the earth.
Flash steam plants take high-pressure hot water from deep inside the earth and convert it to steam to drive generator turbines. When the steam cools, it condenses to water and is injected back into the ground to be used again. Most geothermal power plants are flash steam plants.
Binary cycle power plants transfer 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.
Benefit Of GeoThermal Energy:
- Renewable—Through proper reservoir management, the rate of energy extraction can be balanced with a reservoir’s natural heat recharge rate.
- Baseload—Geothermal power plants produce electricity consistently, running 24 hours per day / 7 days per week, regardless of weather conditions.
- Domestic—U.S. geothermal resources can be harnessed for power production without importing fuel.
- Small Footprint—Geothermal power plants are compact; using less land per GWh (404 m2) than coal (3642 m2) wind (1335 m2) or solar PV with center station (3237 m2).*
- Clean—Modern closed-loop geothermal power plants emit no greenhouse gasses; life cycle GHG emissions (50 g CO2 eq/kWhe) are four times less than solar PV, and six to 20 times lower than natural gas. Geothermal power plants consume less water on average over the lifetime energy output than the most conventional generation technologies.
Advantages of Geothermal Energy
1) It is a renewable source of energy.
2) Non-polluting and environment friendly.
3)No wastage or generation of by-products.
4) Geothermal energy can be used directly. In ancient times, people used this source of energy for heating homes, cooking, etc.
5) Maintenance cost is very less.
6) Geothermal power plants don’t occupy too much space and thus help in protecting natural environment.
7) Unlike solar energy, it is not dependent on the weather conditions.
Disadvantages of Geothermal Energy
1) Only few sites have the potential of Geothermal Energy.
2) Most of the sites, where geothermal energy is produced, are far from markets or cities, where it needs to be consumed.
3) Total generation potential of this source is too small.
4) There is always a danger of eruption of volcano.
5) Installation cost of steam power plant is very high.
6) There is no guarantee that the amount of energy which is produced will justify the capital expenditure and operations costs.
7) It may release some harmful, poisonous gases that can escape through the holes drilled during construction.