Seasonal Heat Storage in Underground Warm Water Stores. Construction and Testing of a 500 M exp 3 Store

摘要

The aim of the work has been to show that warm water pits, uninsulated towards the soil are well suited for seasonal heat storage. Limiting the insulation to the top surface will contribute to a construction price reduction, which is so important, if seasonal storage shall be economically feasible. A truncated pyramidal geometry completely imbeded in the ground was chosen. The uninsulated store/soil interface was made waterproof by use of a 2.5 mm high density polyethylene liner. The floating insulated lid was constructed in a ''dry-dock'' and floated to final position. A floating gasket was installed to seal the lid to the pit walls. The inlet and outlet systems for water made circulation of the entire pit volume possible in four days. Two 36 kW gas boilers and an aircooler of about 30 kW made simulated operations between 30degC possible. In order to get an impression of the reduction in heat loss expected by many seasonal operations a sinoidal charge-discharge pattern between 30degC and 60degC over a 70 day-periods was used. The measured temperatures in the soil were compared with the computed temperatures and satisfactory agreement was found based on the actual thermal properties. The storage efficiency measured indicated, that the theoretical expression developed for the seasonal storage efficiency will be in good agreement with the efficiency which will be obtained in practical work. (ERA citation 10:009946)