Operating Experience with Vertical Borehole Heat Exchanger for Underground Thermal Energy Storage Applications in Chile and Argentina

Abstract

The possible heat sources for seasonal Underground Thermal Energy Storage (UTES) can be divided in two main groups - renewable energy (solar thermal, hydrogeothermal, biofuels and others) and waste heat (heat and power co-generation, industrial process heat, waste incineration and others). Chile is a country possessing solar energy in large amounts which can be stored in the ground by means of UTES during the summer and used 3 to 6 months later during the winter. The same seasonal storage could be used to produce cold in the summer. Large cities, like Santiago with a population of more than 5 million inhabitants, requires heating in the winter (minimum temperature about -5?C) and cold in the summer (maximum temperature about 35?C). A setup for testing this type of storages was realized at the "Solar Energy Laboratory" of the Technical University Federico Santa Maria, Valparaiso, Chile. Research groups of Chile and Argentina performed and analyzed a charging - discharging cycle test with this installation. During the first phase the store was charged during 29 days (18.08 - 16.09.2003) with solar energy by means of 4.4 m2 of solar collectors. Discharging followed during 13 days (17.09 - 30.09.2003) using a water-water heat exchanger. One loop was connected to the BHE the other loop was supplied with tap water. The experiments made prove the possibility of using underground seasonal storage for heating and cooling in different regions of Chile and Latin America (Argentina, Brazil) and to apply the BTES technology in the same region.