Soil-Water Pit Heat Store with direct charging system - Technology and Economy

In the case of large pit heat stores (10 000 m3) with small area to volume ratio (A/V) the thermal storage medium embodies a significant cost reduction potential. If there is no gravel available at or near the construction site of the store, and if the excavated soil can be refilled, it can be used as a very cheap heat storage medium. Both the money for the landfill and the costs for the gravel can be saved. An indirect charging system designed similar to a floor heating system using plastic piping (see figure 1) is required in the case of a soil/sand pit heat store. This is the main disadvantage of this concept, because the length and as a consequence the cost of the plastic piping increase linearly with the size of the store. Thus the cost reduction potential of the storage medium is compensated by the complicated and consequently costly plastic piping system. In table 1 an overview of realised gravel-water and soil/sand water pit heat stores is given: