GEOTHERMAL CLOSED LOOP
Closed loops can have many configurations; the three basic being vertical, horizontal or lake or pond. The choice will depend on the size of the property, the future plans for it, the soil around it or the equipment used to excavate. Many make the choice based on the cost, but designed and installed properly, with heating and cooling requirements considered, the loop will provide years of free renewable energy.
The area needed to install a horizontal loop depends on the configuration of the loop, the heating and cooling load of the home, the depth at which it is to be buried, the soil and the amount of moisture it contains, the climate and the efficiency of the heat pump. The average 150 square metre home needs about a 300 to 700 square metre area. Contractors have computer software and loop design guidelines to help with choices.
A vertical loop is also made of HDPE pipe, but it is inserted into holes drilled the soil. These holes are typically drilled 15 to 100 metres deep and 10 to 12 centimetres in diameter. Two lengths of pipe are fused together in a U-bend and inserted into the hole. Pipe which may be 19 or 25 mm is sometimes used. Pipe 32 mm is common in some areas. After the pipe is placed in the hole, it is filled with clay grout. Some sand, crushed stone or cement may be added to the grout.
CSA standards require the grout to be added using a tremie line, or a pipe inserted to the bottom of the hole and retracted as it is filled with grout. This process eliminates air pockets around the pipe and ensures good contact with the soil.
The a vertical loop can be installed in a much smaller area than a horizontal loop and often fits a city lot.
The cost of a vertical loop can vary with soil conditions, some of which cause time consuming drilling. The depth depends on much the same factors as the horizontal loop and the depth to which the holes can be bored.
Lake or pond loops can be installed very cost effectively if there is a lake or pond close by. The water temperature at the bottom of a frozen lake is four to five degrees Celcius even during the coldest weather and the water absorbs the heat from air conditioning in the summer. A minimum depth of the water is two metres, along with protection from wave action and ice pile up. Permission will be required if you don't own the lake or pond. Irrigation ponds can do double duty for lake or pond loops.