As it was discussed several types of GHEs such as shallow and deep ones are existed. Deep GHEs are generally U-tube GHEs with common ranges of 50-200 meter. Shallow GHEs are divided to spiral , slinky, pond/lake and snails types.
Among different types of shallow GHEs spiral ones show the best performance in the same application unit area which means that more amount of heat can be extracted or injected into the ground. This also means that more space area of the building could be heated or cooled by spiral GHEs. Spiral GHEs are favorable due to their high efficiencies and low initial costs. When spiral GHEs are connected to the heat pump system and total system (GSHP) is integrated to the buildings, heating/cooling demands of that specific residential building could be supplied easily by spiral GHEs. Many researches show that when nine numbers of spiral GHEs are connected to the heat pump system, heating demands of at least 200 square meter space area of a building could be supplied. Based on different parameters of spiral GHEs this value could be changed between 200-800 square meter space area. In Fig. 1 schematic view of series of spiral GHEs are shown.3