Replacement of electric resistive space heating by a geothermal heat pump in a residential application - Environmental amortisation

This paper reports the life cycle analysis (LCA) of the replacement of a conventional boiler by a geothermal boiler in a standard, medium sized, single-family dwelling, located in a Mediterranean country such as Spain. The geothermal installation analysed is vertical, with two wells of 0.66 m diameter and 125 m depth each. This type of vertical wells has been chosen due to the smaller surface area required compared to horizontal collectors. The LCA studies the costs of the different phases, as well as the costs of the final installation. The system boundaries considered during the study cover the overall production for the creation of a functional unit in a gate-to-gate study. Findings indicate that the greatest environmental impacts are in Marine Aquatic Ecotoxicity category and the lowest corresponds to the Ozone Layer Depletion category. Regarding the phases, the drilling phase has the highest environmental impact and the second one is the boiler installation, while the lowest impact is found in the installation of probes. Finally, an amortisation analysis for environmental impact is developed, concluding that all categories are amortised in 8 years and some of them in less than 3 years.