Geothermal Heat Pump-Energy Within - Using Geothermal Energy

This means of energy production uses the heat of the earth to generate power. Currently around 8,000 MW of electricity, with 2,800 MW in the United States alone. As with many other alternative sources,geothermal shows great potential. In a report released last year, the U.S. Geological Survey estimates that the geothermal potential in the U.S. alone is between 95,000 and 150,000 MWe (megawatts of electric power). A report issued just last year by MIT estimates the world's geothermal potential using Enhanced Geothermal Systems (EGS) at more than to be over 13,000 ZJ (a zettajoule is 1021) of which over 200 ZJ would be ex tractable with current technology.

Geothermal Technology

There are two basic types of geothermal power plants currently in use. Steam plants can use the hot water and very hot steam (over 300F) to power a turbine that feeds a generator directly ("dry steam") or they can depressurize the very high-pressure and temperature water to create steam ("flash steam"). The only emission in enough quantity to be significant is steam, although minute amounts of CO2, NOx and sulfur are released (in amounts almost 50 less than the amounts emitted at fossil fuel plants). Currently steam plants can generate electricity for about 4 cents to 6 cents per kWh.

Binary plants can operate at locations with lower temperatures ((100 F to 300 F), which is more readily available. Hot water passes through aheat exchanger along with a working fluid that has a lower boiling point (e.g., isobutene, isopentane). The working fluid vaporizes, turning the turbines and powering the generators.

Because this system is a closed loop, there are no emissions. Currently steam plants can generate electricity for about 5 cents to 8 cents per kWh. Because the lower-temperaturegeothermal locations are more plentiful, most plants are binary.

Geothermal energy can also be used a direct heat source. Nearly all the houses in Iceland are heated with water from hot springs, and the country generates more than half its energy fromgeothermal sources. If the heat is there but the water is not, energy can still be extracted. Pumping water through hot rock heats the water and can be used directly or to generate power.

Underground heat pumps are also a form of geothermal energy, these work like refrigerators in reverse. Believe it or not, you don't have to dig very deep to find the level of earth that stays at a fairly constant temperature - usually about 8 feet.Heat pumps use pipes (buried well below the frost line) that circulate a refrigerant through a cycle of condensing and evaporating between twoheat exchangers. One heat exchanger evaporates at low pressure and absorbs heat . A compressor pushes the refrigerant vapor, now at high pressure, to other coil where the refrigerant condenses and releases theheat. Unlike refrigerators and air conditioners, heat pumps can work in both directions-heating and cooling. Energy cost savings with a ground-based heat pump are substantial.

Geothermal Power Advantages

1.Geothermal energy produces little or no emissions.
2. In most cases, the "fuel" is free, although with the "hot rock" method water must be used, and may have to be transported there. Once the power stations are built they cost very little to operate.
3.Geothermal power plants usually have a small footprint, and very little environmental impact.
4.Ground-based heat pumps can be used almost anywhere. If you're thinking that they won't work in your snowy neck of the woods, consider that they are used extensively in Canada.

Geothermal Power Disadvantages

1.Geothermal cannot be considered a renewable resource (although it is a sustainable one).
2.Not every area has accessible geothermal sources. The hot rocks and water must be within drilling range (except in the case of natural geysers).
3.Geothermal sites can run out of steam, as their temperatures drop to low. This can happen naturally or if a "hot rock" extraction method is mismanaged, and the water injected cools the rocks.
4.Along with the hot water and/or steam, geothermal sources can also yield up harmful gases and minerals.
5.Drilling deep into the ground, especially when water is then pumped into the holes, can set off "small seismic events" - earthquakes.
6.While research can suggest likely places for geothermal power plants, there is no guarantee a given site will produce enough energy to offset the capital expenditure and operating costs.

What Can You Do?

Ocean and earth power gives you a lot of options. We've collected the ideas from this chapter-hydropower, tidal power, wave power, ocean thermal conversion, andgeothermal power- at the end to remind you of the variety, and to reinforce the idea that while there is no single perfect alternative energy source for the world, or even the country, there are many that in combination could be the perfect solution for you. Much depends on where you live and what resources you have.

1.If you have a river, stream, brook, waterfall or some other running water nearby, look into installing a micro hydro system to generate some or all of your electricity.
2.If you live on a body of water that experiences tides, you may be able to use them to your advantage. Naturally you won't be damming up estuaries to power your house (your own personal tide mill), but it is possible that you could implement something on a much smaller scale that powers, say, your dock lights. Realistically, however, what you'll be doing is keeping up with the technology so you'll know when someone has developed something with a more personal application.
3.While none of the wave power technologies are available as personal-size power stations, if you live somewhere that has strong, consistent waves, you may be able to adapt some of the techniques.
4.While you probably don't have a geyser in your yard, you might be able to install a ground-based heat pump to heat and cool your house.

By Kevin Rockwell