The word geothermal comes from the Greek words geo (earth) and therme (heat), thus geothermal energy is heat from within the earth. We can use the steam and hot water produced inside the earth to heat buildings or generate electricity. Geothermal energy is a renewable energy source because the water is replenished by rainfall and the heat is continuously produced inside the earth. Geothermal power supplies less than 1% of the world’s power. Electricity has been generated successfully from a producing oil well’s geothermal hot water for the first time in October 2008. DOE’s Rocky Mountain Oilfield Testing Center and Ormat Technologies used a standard commercial Ormat Organic Rankine Cycle power plant, using hot water from a producing oil well to exchange heat in an Ormat Energy Converter. This project is unique in its production of onsite renewable power and has the potential to increase the productivity and longevity of existing US oil fields. Harnessing hot water produced during production to power the oil field could lead to more economical access, especially in older, depleted fields. A large number of US oil and gas fields produce hot water as well as hydrocarbons. DOE said that while the unit at NRR-3 is the first to use geothermal water from a producing oil field, it is similar to a 250 kw Ormat unit which has generated electricity at an Austrian resort from 210 degree F geothermal water for more than six years. Similar units have been in continuous operation in Nevada and Thailand since the 1980s.