Groundwater Heat Pump assessment operation in three cities of south-central Chile: An approach based on aquifer characterization and analytical calculations of Thermal Affectation Zone

Abstract

The aim of this work is the Groundwater Heat Pump (GWHP) assessment in three cities in south central Chile (Talca, Temuco, and Osorno), considering the hydraulic parameters of the aquifer, its temperature, and the Thermal Affectation Zone (TAZ) generated around the reinjection well due to the reinjected water flow, and temperature difference, due to thermal recovery.According to the hydraulic characterization, the conditions are more favorable in the city of Talca, where the hydraulic conductivity is medium to high. On the other hand, in the cities of Temuco and Osorno, the hydraulic conductivity is low or very low, except in some domains of river belts, where the hydraulic conductivity is medium to high. In all cities, the temperature of the aquifer is very good for heating and cooling. In particular, in Talca downtown there is a positive thermal anomaly that improves the GWHP performance for heating purposes.In each city, the extension of the TAZ was calculated for a reinjection rate of 5 [L/s], and a thermal recovery of 3 [°C] (heating). In each city, the TAZ was calculated for the hydraulic conductivity values corresponding to the percentiles 25, 50, and 75. The hydraulic gradient is fixed for each city. The heating time increases from north to south (Talca, Temuco and Osorno) due to the climate. In all cities and in all cases, temperature dispersion due to groundwater flow is moderate to slight and concentrated around the reinjection well. The largest extension of TAZ in the direction of groundwater flow is calculated in Talca, reaching approximately 30 m. On the other hand, the greatest reach of TAZ in the opposite direction to the groundwater flow is calculated in Osorno, reaching approximately 20 m. The effect of varying injection rates (3, 5 and 10 L/s) does not significantly affect the distance range of TAZ, yet affects the concentration of TAZ around the reinjection well.