VTTESS- Variable-Temperature Thermochemical Energy Storage System and Heat Networks for Decarbonising the Buildings Sector

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Over half of all energy consumption in the UK is for meeting thermal demand, with the buildings sector accounting for around 44%. Direct and indirect greenhouse gas emissions from buildings alone accounted for 26% of the UK total in 2019. In order to decarbonise the supply side of the buildings sector, low carbon and zero carbon heating systems need to be developed to replace fossil-fuelled systems. There are many potential candidates, such as geothermal and solar-thermal, industrial, and commercial waste heat and heat pumps. However, the variable nature of the low-zero carbon sources, both short term (daily) and long term (seasonal), and mismatches between needs and availability of energy, make decarbonisation difficult to achieve at the individual building level. District heating (DH) systems in urban settings (industrial and domestic) are ideally placed to provide the infrastructure to match the demand from individual buildings via transient low/zero carbon sources, but require suitable energy storage facilities that can operate over a range of source temperatures. Currently, just over 7% of DH systems in the UK use hot water storage. Fluidised bed thermochemical energy storage (TCES) system using water circulation through inorganic oxides has great potential for storage at high energy densities. It can be designed for operation at variable temperatures. It can retain the energy in its absorbed state, with near-zero losses and so potentially allowing storage inter-seasonally, e.g. storing solar energy in summer during low demand and discharging in winter during high demand. DH integrated with TCES will significantly contribute to decarbonisation of the built environment, addressing issues of fuel poverty and pollution. However, its success depends not only on technical capacities but also on the systemic inter-dependencies between macro (national), meso (regional) and micro (local) level actors. DH is a context-specific energy service where a coalition of these actors are essential, and social and environmental criteria must be incorporated in the decision-making process. As DH is a multi-building technology, for residential application, community engagement and integration of citizens in the decision process, taking into account of the above elements, are critical to ensure a pathway to success. We will therefore develop a co-design framework to better understand socio-political, organisational, economic, and technical factors associated with TCES-DH system in order to foster a community of practice between actors on all levels.