Energy performance of a high BHEs density at district scale

It is known that the ground represents a vast heat energy reservoir but the main challenge relies how technically exploit it in a sustainable way. Vertical BHEs represent a non-invasive application to improve the decarbonisation of the heating sector for dense populated urban areas. The conflicts arise when a large number of BHEs is installed. The present project investigated the energy performance of a high BHEs deployment for a district in Chicago (USA). The analytical approach developed for a specific BHEs field design pointed out that 24% and 39.3% of the total heating and respectively cooling demand can be satisfied. Numerical calculations are performed for two identified urban blocks using the finite element software COMSOL Multiphysicsr to consider the energy performance losses due to adjacent geothermal installations. For five smaller adjacent BHEs fields a temperature drop of 1.2 − 2.1!C occurred in the heat carrier fluid due to their mutual operation. The scenario is worse for three larger neighbouring BHEs fields recording a fluid temperature decrease of 3.7 − 5.9!C. Obtained results highlighted that there is a need to better frame the thermal performance losses due to a high BHEs deployment and to integrate them in design requirements. We applied correction factors to adjust the energy performance of isolated BHEs field in order to avoid a potential cooling of the ground and conflicts between neighbours. The thermal e↵ect of heated buildings basements on the BHEs energy performance is also investigated. An increase ranging from 0.3!C to 0.4!C occurred in the mean temperature fluid after 50 years