Five basic types of GeoThermal energy sources
Closed loop systems circulate a water-based solution through a "loop" of small diameter, underground pipes. In cold weather this solution absorbs heat from the earth and carries it to the geothermal unit. The geothermal system amplifies the heat and delivers it indoors. In warm weather the process is reversed, excess heat is carried from indoors and into the earth. You keep refreshingly cool during the hottest summer.
Horizontal loops are often considered when adequate land surface is available. Pipes are placed in trenches, in lengths that range from 100 to 400 feet.
Vertical loops are the ideal choice when available land surface is limited. Drilling equipment is used to bore small-diameter holes from 75 to 300 feet deep.
Pond (lake) loops are very economical to install when a body of water is available, because excavation costs are virtually eliminated. Coils of pipe are simply placed on the bottom of the pond or lake.
Open loop systems utilize ground water as a direct energy source. In ideal conditions, an open loop application can be the most economical type of geothermal system.