Second law analysis of horizontal geothermal heat pump systems

This paper presents an exergetic analysis of the operating conditions of a shallow horizontal groundsource heat pump. The analysis is conducted through theoretical evaluation of the exergy potential andthe evaluation of the main sources of unavoidable irreversibilities. This approach can be used to assessthe main causes of performance reduction and degradation, as well as to select the optimal installation(depth, position) or to modify the operating parameters.The analysis of a real installation in then considered. This is a horizontal ground heat exchanger, consti-tuted of a network of pipes installed 1 m below the surface, covering an area of about 210 m2. A comparisonof the current installation with a deeper installation, 2 m below the surface, shows that the exergy outputcan be increased of more than 60%. This improvement can be easily compared with the increase in theinstallation costs in order to evaluate the optimal depth.