ook's blog

GEOTHERMAL ENERGY

Geothermal energy is energy obtained by tapping the heat of the earth itself, usually from kilometers deep into the earth’ s crust. It is expensive to build a power station but operating costs are low resulting in low energy costs for suitable sites. Ultimately, this energy derives from heat the earth’s core. The government of Iceland states:”It should be stressed that the geothermal resource is not strictly, renewable in the sense as the hydro resource.” It estimates that Iceland’s geothermal energy could provide 1700 MW for over 100 years, compared to the current production of 140 MW. Radioactive elements in the earth’s crust continuosly decay, replenishing the heat. The international energy agency classifies geothermal power as renewable.

 

Three types of power plant are used to generate power from geothermal energy : dry steam, flash and binary. Dry steam plants take steam out of fractures in the ground and used to directly drive a turbine that spins generator. Flash plants take hot water, usually at temperatures over 200 C , out of ground and allows it to boil as it rises to the surface then separates the steam phase in steam / water separators and then runs the steam through a turbine. In binary plants the hot water flows through it exchangers, boiling an organic fluid that spins the turbine. The condensed steam and remaining geothermal fluid from all three types of plants are injected back into the hot rock to pick up more heat.

 

The geothermal energy from the core of the earth is closer to the surface in some areas than in others. Where hot underground steam or water can be tapped and bought to the surface it may be used to generate electricity. Such geothermal power source exist in certain geologically unstable parts of the world such as chile, Iceland, new Zealand, united states, the phillipines and Italy. The two most prominent areas for this in the united states are in the Yellowstone basin and in northern California. Iceland produced 170 MW geothermal powers and heated 86% of all houses in the year 2000 through geothermal energy. Some 8000 MW of capacity is operational in total.

 

There is also the potential to generate geothermal energy from hot dry rocks. Holes at least 3 km deep are drilled into the earth. Some of these holes pump water into the earth, while other holes pump hot water out. The heat resource consists of hot underground radiogenic granit rocks, which heat up when there is enough sediment between the rock and the earth’s surface. Several companies in Australia are exploring this technology.

 

source : www.wikipedia.com