ABSTRACT
The heat load of a residential unit is normally covered by heat from a conventional energy source. To identify more environment-friendly applications, attention is being given to the potential of solar energy. A seasonal solar application must be incorporated with a heat store to equalise the gap between supply and demand of heat and to achieve an acceptable solar fraction at reasonable cost.
An interesting technique is seasonal storage in clay. For two years, the Swedish Geotechnical Institute has been operating a test field to study high temperature storage (70 °C) in clay. The results have so far been very promising. Performance of the heat stores has been trouble-free. The newly developed method for continuous duct installation has proved to be very efficient. The problem of oxygen diffusion through the ground heat exchangers has been eliminated. Low installation costs have also been confirmed. Economically, simulations have indicated a lowest solar heat cost of 86 US$/MWh.
