Only one pond is in use. Sufficient liquid volume will be maintained throughout the pond's 30-year life. At the end of pond life, the sludge can be removed to a disposal site or mixed with cement to form the bottom for a new pond build directly over the old one. Control points for the system are shown schematically in Figures 1 and 2. Flow of geothermal fluid from the well is regulated by a valve and controller responding to ambient temperature.
Minimum flow is maintained at higher temperatures to provide energy for domestic hot water heating.
A second valve maintains back pressure in the distribution piping to minimize calcite precipitation. The temperature of the hydronic fluid leaving the geothermal heat exchangers and ambient temperature determine geothermal flow rate to the heat exchangers. Circulation in the heating loop is controlled by ambient and fluid temperatures. This avoids wasting pumping energy. Room thermostats control flow through terminal units.