Assessment of Smart Heating and Cooling System Based on Thermal Use of Shallow Aquifer

Abstract

All metropolis across the world are facing the challenges of the growing energy demand and the need to reduce the CO₂ emissions. In order to match the two constraints, urban environments should diversify energy sources and maximize local opportunities offered by renewable resources. Within this context, water resources and especially groundwater represent potential alternatives that could provide an efficient answer to the development needs. Nice Côte d'Azur Metropolis gathers around 540,000 inhabitants with more than 350,000 for the city of Nice. Within a national strategic project, the metropolis is currently develo** a new urban environment located within the low valley of the Var river and has decided to establish a multi-energy Smart Grid solution. The innovative technological approach is based on: storage of heat, production of cold and electricity, and also a cooling offer for individuals, resulting from the recovery of energy used to air-condition commercial buildings. The chosen solution is based on thermal use of the shallow unconfined aquifer located with the Var floodplain. The network is using surface geothermal energy from the alluvial aquifer. By 2029, it will cover the heating (7.2 GWh per year), air conditioning (15.5 GWh per year) and domestic hot water (7.5 GWh per year) needs of 520,000 m² of housing, hotels and additional residential facilities, shops, services and offices served by 1.6 km of geothermal network, 5.6 km of hot and cold networks and 94 sub-stations. The Nice Méridia area will thus be supplied by 82% renewable and recovered energy for heating and 78% for cooling. The development of the geothermal solution requests to pump and to reinject important volumes within the unconfined aquifer. In order to assess the potential impact of the solution on the existing uses (drinking water supply pum** stations), a 3D modelling approach has been deployed over the full groundwater resource of the Var valley. The model, built with FEFLOW solution, validated with field observation, can reproduce the behavior of the aquifer (flow dynamic and thermal). The results have demonstrated the efficiency of the 3D modelling approach and the possibility to use the geothermal resource without significant impact on the aquifer. The thermal use of the shallow unconfined aquifer represents a promising solution that could be duplicated in other locations where similar aquifers are present.