For example, Ormat Technologies has delivered a more than 150% gain, between January and September of 2006. As stated on their official website, http://www.ormat.com/, Ormat Technologies, Inc, (NYSE: "ORA") is a leading vertically integrated company dedicated to providing solutions for geothermal power, recovered energy generation (REG) and remote power. The Company designs, develops, builds, owns and operates geothermal and recovered energy-based power plants. Additionally, the Company designs, manufactures and sells geothermal and recovered energy power units and other power generating equipment, and provides related services. Ormat products and systems are covered by more than 70 patents. Ormat's geothermal power plants are a field-proven, mature commercial product operating worldwide, designed for outdoor installation and remote control unattended operation. Ormat has successfully supplied more than 800 MW of geothermal power plants, based on its proprietary technology, logging millions of hours of operating experience.

Magma Power Company is one of the largest geothermal companies in California. Magma Power Company searches for, develops, and sells or leases geothermal resources used to generate electric power. Magma Power is not the other California geothermal companies, because it's a pioneer in its field and almost solely responsible for creating the geothermal industry in USA. It was the first of all geothermal energy companies to start drilling for naturally produced steam way back in the mid-1950s. It's not only developing geothermal resources, but it also constructs and operates geothermal electric power plants.

Vulcan is also amongst the top geothermal power companies. It's privately owned, headquartered in Bend, Oregon and founded in 1991. The main focus of Vulcan is the development and operation of clean, renewable, non-stop baseload geothermal power plants. A 2007 third-party report estimated that Vulcan properties can supply electricity for up to 2 million Americans. The official company website is http://www.vulcanpower.com/.

Enel is one of the Italian geothermal electric companies and as you probably know, Italy is the country where geothermal energy was first utilized. Enel's substantial geothermal expertise in Italy is now being exported to North America where Enel North America is combining it with local knowledge to build a strong geothermal program. In early 2007, Enel NA acquired the rights to develop and operate four geothermal projects totaling approximately 150 MW, located in Utah, California, and Nevada. The official website of Enel is http://www.enel.it/.

Econar and Borel Geothermal are one of the most popular geothermal heat pump manufactures. Delaware is one of the China lake geothermal companies.

Here is the basic principle of operation of a geothermal power plant. People have geothermal water from the earliest times as they used to cook using the hot water that flowed from the earth's surface. The Romans were actually using to treat eye and skin diseases, while the Pompeii were using to heat buildings. Native Americans were also using geothermal energy for cooking and medicine. In present days, geothermal power plants are taking it to the next step and use geothermal energy to generate electricity. The first geothermal power plant went into operation at The Geysers in 1921. It produced 250KW of electricity.

Geothermal power plants use heat, steam, or hot water from geothermal reservoirs as they provide the force that spins the turbine generators to produce electricity. There has got to be an external force that has to make the turbine generators spin and that's exactly the purpsoe of hot water in this case, or heat, or steam. Geothermal energy is a renewable type of energy because once the geothermal water is used, it's returned down by re-injection that puts it well into the reservoir to be reheated, to maintain pressure, and to sustain the reservoir.

There are three types of geothermal power plants. These power plants are differentiated depending on the temperatures and pressures of a reservoir, so here is the list:

-Dry steam reservoir - the largest Dry steam reservoir type of geothermal power plant is The Geysers (http://www.geysers.com/). It's in the Mayacamas Mountains, located 72 miles north of San Francisco, where naturally occurring steam field reservoirs below the earth's surface are being harnessed by Calpine to make clean, green, renewable energy for homes and businesses across Northern California. The Geysers, comprising 30 square miles along the Sonoma and Lake County border, is the largest complex of geothermal power plants in the world.

-hot water reservoir - geothermal reservoir that produces mostly hot water. The power plant that utilizes it is called a "flash" power plant.

-reservoir with temperatures between 250 and 360 degrees F - Such a reservoir doesn't have water hot enough to flash enough steam, but a binary power plant can still use it to produce electricity.

Pictures of geothermal power plants can be easily found on the Internet using the Image feature of the Google search engine.

The open loop geothermal heating system has been used with great success for several decades now. Open loop systems work by drawning an aquifer through one well, which is then discharged to the same aquifer but through a second well that is distanced from the first one. Such Geo-Thermal Heating systems are very popular in areas where they are allowed because they the temperature of ground water is almost constant throughout the year.

Closed loop system on the other side seem to be enjoying more success as they are more commonly used. When installed correctly, the closed loop system provides an efficient, economical and at the same timer reliable way of heating a given home. Such systems work by circulating water through a continuous buried pipe. Closed loops can be vertical or horizontal. The horizontal type is the most cost-effective for small installations that have sufficient land area. Up to six pipes, usually in parallel connections, are buried in trenches with minimum separations of a foot between pipes and ten to fifteen feet between trenches. Vertical geothermal heating systems are used when the soil is too shallow for trenching and the property owner doesn't want to change the current landscape. A U-tube is used in such cases, burried between 100 to 400 feet deep.

Here is the principle of operation of geothermal heating systems. The system takes advantage of the fact that the temperature below ground remains the same throughout the entire year, regardless of climate or season. The ground is able to keep a higher rate of temperature consistency because it absorbs almost half of the suns heat as it hits the surface of the earth. A Ground source heat pumps is used to move heat that already exists in the earth to provide your home with central heating.

WaterFurnace is a company manufacturing geothermal heating systems. WaterFurnace geothermal systems use the free, renewable energy found in your own back yard to save up to 70% on heating, cooling, and hot water costs. WaterFurnace manufactures and sells more geothermal systems for homes than anyone else in the business. During the heating cycle, a WaterFurnace geothermal system uses the earth loop to extract heat from the ground. As the system pulls heat from the loop it distributes it through a conventional duct system as warm air. It's interesting to note that WaterFurnace systems can do both heating and cooling. You can find out more information on WaterFurnace at http://www.waterfurnace.com/.

Geothermal comes from the Greek words "Geo" (earth) and "Therme" (heat). So in that sense, you have probably already figured out that geothermal energy is heat from within the earth. We can actually use the steam and hot water inside the earth's core to heat buildings and produce electricity. A very important eco fact is that geothermal energy is a renewable energy source, since the water is recovered by rainfall, while the heat itself is produced all the time within the earth.

One of the most interesting geothermal energy facts is that geothermal energy is produced 4,000 miles below the surface in the earth's core. You will probably be amazed to hear that the temperatures in there are hotter than the sun's surface. The reason for this phenomenon is a radioactive process that takes place in all rocks. People from all parts of the world have started using geothermal energy to heat their homes and generate electricity by digging deep holes and pumping the heated underground water. But that's just one the uses and it's called direct use. Geothermal power plants are built around geothermal reservoirs, because they require water or steam at very high temperature (like 300 to 700 degrees Fahrenheit). Hot water near the surface of the earth is piped directly into buildings and used for heating. In Reykjavik, Iceland, 95% of the buildings use geothermal energy for heating, but that's due to the uniqueness of this country since that's the country with the largest number of geysers in the world.

Geothermal energy is one of the best types of energy when it comes to how safe it is for the environment. We have other sources which are far more dangerous and cause much more pollution, whereas geothermal energy has almost zero negative impact on the environment. The biggest advantage is that it doesn't require the burning of fuel to generate electricity, so there is practically no emission. A geothermal power plant releases only about 1 to 3 percent of the carbon dioxide emissions of a fossil fuel plant and emit 97 percent less acid rain. The best thing is that after the water and how steam have been used, they are reinjected back into the earth.