Geothermal is a general term for many different applications and technologies. Included within those applications are passive earth tubes, active heat pumps and electric power generation. Geothermal power plants create sustainable and fuel free base load energy with minimal operational and maintenance costs. In addition, these plants are designed as closed loop systems; some with the expectation of perpetual power.
The primary generation types include vapor-dominated or liquid-dominated forms, which are divided into High Temperature and Low Temperature Systems respectively.
High Temperature systems generally have resources greater than 392 degrees Fahrenheit and directly drive turbines.
Low Temperature systems have resources between 250 degrees and 392 degrees as the water passes through a heat exchanger and then into an Organic Rankine Cycle binary plant (as represented below). Lower temperature resources are far more common and significantly more accessible to community scale development.
Current Geothermal Trends
According the April 2012 Annual US Geothermal Power Production Development Report published by the Geothermal Energy Association, there is currently 3,187 MW of installed geothermal capacity within the United States. This amounts to almost 3% of domestic renewable energy generation.
Globally, the installed capacity of geothermal resources is close to 11,224 MW and estimates project numbers as high as 2,000 Gigawatts.