

GeoThermal : Closed Loop Systems Energy Savers: Types of Geothermal Heat Pump Systems
The most common type of geothermal installation is a closed loop system. The heat exchanger - a loop of piping filled with fluid - is buried underground. Types of Geothermal Heat Pump Systems. There are four basic types of ground loop systems. Three of these”horizontal, vertical, and pond/lake”are closed-loop systems.
Source: www.energysavers.gov/your_home/space_heating_cooling/index.cfm/mytopic