Establishing an urban geo-observatory to support sustainable development of shallow subsurface heat recovery and storage

Low-enthalpy ground source heating and cooling is recognised as one strategy that can contribute towards reducing reliance on traditional, increasingly insecure, CO2-intense thermal power generation, as well as helping to address fuel poverty. Development of this technology is applicable in urban areas where high housing density often coincides with the presence of shallow aquifers. In urban areas groundwater temperatures can be elevated due to the subsurface Urban Heat Island effect. Uptake and development of this technology is often limited by initial investment costs, however, baseline temperature monitoring and characterisation of urban aquifers, conducted in partnership with local authorities, can provide a greater degree of certainty around resource and sustainability that can facilitate better planning, regulation and management of subsurface heat. We present a novel high-density, city-scale groundwater temperature observatory and introduce a 3D geological model aimed at addressing the needs of developers, planners, regulators and policy makers. The Cardiff Geo-Observatory measures temperature in a Quaternary aged sand and gravel aquifer in 61 boreholes and at a pilot shallow open-loop ground source heating system. We show that repurposing existing infrastructure can provide a cost effective method of developing monitoring networks, and make recommendations on establishing similar geo-observatories.