01-12-2012, 06:18 PM
Geothermal Energy
Geothermal Energy.ppt (Size: 1.04 MB / Downloads: 604)
Sources of Earth’s Internal Energy
70% comes from the decay of radioactive nuclei with long half lives that are embedded within the Earth
Some energy is from residual heat left over from Earths formation.
The rest of the energy comes from meteorite impacts.
Different Geothermal Energy Sources
Hot Water Reservoirs: As the name implies these are reservoirs of hot underground water. There is a large amount of them in the US, but they are more suited for space heating than for electricity production.
Natural Stem Reservoirs: In this case a hole dug into the ground can cause steam to come to the surface. This type of resource is rare in the US.
Geopressured Reservoirs: In this type of reserve, brine completely saturated with natural gas in stored under pressure from the weight of overlying rock. This type of resource can be used for both heat and for natural gas.
How Direct Uses Work
Direct Sources function by sending water down a well to be heated by the Earth’s warmth.
Then a heat pump is used to take the heat from the underground water to the substance that heats the house.
Then after the water it is cooled is injected back into the Earth.
Availability of Geothermal Energy
On average, the Earth emits 1/16 W/m2. However, this number can be much higher in areas such as regions near volcanoes, hot springs and fumaroles.
As a rough rule, 1 km3 of hot rock cooled by 1000C will yield 30 MW of electricity over thirty years.
It is estimated that the world could produce 600,000 EJ over 5 million years.
There is believed to be enough heat radiating from the center of the Earth to fulfill human energy demands for the remainder of the biosphere’s lifetime.