System-driven design of hybrid electricity- and hydrogen-based systems for domestic heat decarbonisation

For the purpose of Open Access, the authors have applied a CC BY public copyright licence to any Author Accepted Manuscript version arising from this submission.This paper explores various combinations of electric heat pumps (EHPs), hydrogen boilers (HBs), electric boilers (EBs), hydrogen absorption heat pumps (AHPs) and thermal energy storage (TES) to assess their potential for delivering cost-efficient low-carbon heat supply. A technology-to-systems approach is adopted in the paper based on comprehensive thermodynamic and component-costing models of various heating technologies, which are integrated into a whole-energy system optimisation model to determine cost-effective configurations of heating systems that minimise the overall cost for both the system and the end-user. Case studies presented in the paper focus on two archetypal systems that differ in terms of heat demand and availability profiles of renewables (North and South). Modelling results indicate a preference for a portfolio of low-carbon heating technologies including EHPs, EBs, HBs and TES, while AHPs are not chosen for investment due to their high investment cost. Capacities of the four heating technologies are found to vary significantly depending on system properties such as the volume and diversity of heat demand and the availability profiles of renewable generation. The bulk of heat (83-97%) is delivered through EHPs, while the remainder is supplied by a mix of EBs, HBs and TES. The results also suggest a strong impact of heat demand diversity on the cost-efficient mix of heating technologies, with higher diversity (i.e. lower coincidence factor) favouring less EHP and more of the other, less capital-intensive heating options. Finally, if only a subset of heating technologies is available for investment, the modelling suggests that coupling EHPs with TES is the second best solution in the North system, while in the South it was the combination of EHPs and EBs.UK Engineering and Physical Sciences Research Council (EPSRC) grant number EP/R045518/1 (IDLES Programme)