Large-scale climate neutral Energy Geostructures in District Heating & Cooling systems/networks. Funded by CETP2022, RCN Aage Stangeland.

Europe's energy consumption is increasing every year, with buildings accounting for more than 40% of the total energy (European Parliament, 2022). According to Eurostat (2020), space heating and cooling, together with hot water, account for up to 80% of energy consumption in the residential sector. In the context of climate change, it is crucial to develop local and affordable low-carbon energy sources with low environmental impact to be able to reach the goals of the EU climate goals 2030 and further on the long-term strategy 2050 to become climate neutral (2030 Climate Target Plan). As the carbon footprint of electricity is falling, electrification of heating and cooling through the use of high efficiency ground source heat pumps is a key to decrease non-renewable energy usage and contribute to CO2 emission reductions. However, high initial capital costs, installation time and technological challenges remain significant barriers to adoption. Despite the huge potential, geothermal systems are installed at a lower rate than other renewables. Since the 1980s, the development of Energy GeoStructures (EGS) has made it possible to harness shallow geothermal energy from concrete structural elements in contact with the ground (e.g. pile foundations, retaining walls, tunnels) by integrating heat exchange tubes into them. EGS are therefore novel dual-function engineering substructures that can be used not only as load-bearing elements but also for heat transfer and storage. Their principle is to install heat exchanging tubes connected to the reinforcement cages of these geostructures, giving them an energy role to exploit the thermal energy available in the ground for heating and cooling, in addition to the mechanical role for which their construction is necessary anyway. This dual role makes it possible to reduce the upfront investment and bring the carbon footprint down significantly. The aim of LEG-DHC project is to boost the development of EGS in Norway and Europe.

In the light of low-carbon sustainable city, underground structure, such as retaining wall, pile, tunnel etc., can be equipped with ground heat exchangers to harness thermal energy stored by the ground for heating and/or cooling buildings, leading to a friendly technology namely Energy Geostructures (EGS). Previous investigations over the decades have significantly advanced the technological readiness level (TRL) of some EGS (thermo-active piles) to a higher 4+ level with a number of pilot sites. Despite this well-known interest, there still remains some technical barriers on the route of the implementation and integration of EGS at a large scale as mentioned below: • The lack of visibility on positive thermal and mechanical feedback for the stakeholders • The integration of EGS into a district heating system at the regional scale • The collaborative operation and management of geothermal energy, solar and other local energy sources for a climate neutral regional community. To breakdown the aforementioned barriers, this project will aim to: - Show the global feasibility in terms of thermal efficiency and mechanical impact on existing complex infrastructure. In particular, the energy production, carbon reduction and other existing data will be analysed to demonstrate the environmental protection over previous efforts. - Provide a structured, easily accessible and clear database presenting feedback on thermomechanical behaviour, energy performance, overall efficiency, durability, etc.