GES-CAL: A new computer program for the design of closed-loop geothermal energy systems

•New software (GES-CAL) for the design of shallow geothermal systems is presented.•The internal calculations of the software are based on previous experimental results.•The tool is capable of considering all the frequent heat exchanger configurations.•GES-CAL also provides an economical and environmental evaluation.•The new software is especially efficient for its implementation in the region of Ávila (Spain).