Utilizing of Water Phase Transitions in Heat Storage Systems
Abstract
Utilizing of the solar energy for heating existing family houses requires seasonal heat magazines with a capacity at least 50 kWh/m² of a dwelling area. Depending on the house size, 3000 - 8000 kWh heat has to be available in the magazine at the end of autumn. Closed heat magazines with desired energy content are neither technically, nor financially justifiable. Open soil heat magazines, utilizing sensible heat, are known , but they are justified only for large capacity systems (GWh size). Only then, the ratio of volume to surface area is large enough to keep thermal losses of a magazine at an acceptable level. Another solution, combination of deep borehole with a heat pump is frequently used. However, the return on investment of such system frequently exceeds 10 years. Increasing the capacity of seasonal heat depositories is therefore highly desired. In the present article a seasonal heat storage system, making use of the water latent heat is described. As a result, the heat capacity of wet soil heat magazine can exceed 70 kWh/m³ without any heat losses and the surface area of the magazine for a house with the dwelling area of ca 100 m² can be kept below 100 m².