Multi-scale modelling of integrated energy supply systems

Local energy systems are changing with the use of more distributed generation as well as the decarbonisation of heat and transport, but the impacts of these local changes on national scale energy supply systems are not well understood. The existing whole energy system models lack the spatial granularity to represent local energy systems and their interactions with gas and electricity transmission networks. This key limitation was addressed by the new CGEN+Energy Hubs model. The CGEN+Energy Hubs Model enables multi-time period operational analysis of integrated national and local energy supply systems. The CGEN+Energy Hubs model was developed by extending a well�established Combined Gas and Electricity Network model (CGEN) by adding the representation of local energy systems. Energy Hubs were used to represent local energy systems in different geographic areas of GB. The CGEN+Energy Hubs model also extended CGEN by including functions for bi-directional electricity interconnector flows, intermittent renewable generation, demand response, distributed injection of hydrogen and biogas, and vehicle to grid electricity supply. The application of the CGEN+Energy Hubs model was demonstrated using contrasting Energy Supply Strategies. The Energy Supply Strategies were defined to explore options to decarbonise heat supply in GB: i.e. 1) low-carbon electricity in the Electric Strategy 2) biomass and solid-waste fuelled CHP in the Heat Network Strategy, 3) hydrogen and biogas in the Green Gas Strategy, and 4) Unconstrained, which employs cost optimisation to choose the heating technology. The Energy Supply Strategies were first applied to the Oxford-Cambridge Arc region to investigate how each strategy would cost-effectively reduce CO2 emissions from the Arc’s energy system. The Electric Strategy was shown to be able to meet the CO2 emissions target in 2050 at the lowest annualised costs per dwelling (investment and operation). The study showed that additional investment is needed to increase the capacity of transmission electricity supply, distributed generation, and the electricity distribution network. The Energy Supply Strategies were then applied to all Energy Hubs in GB simultaneously. The Electric Strategy was again shown to be able to deliver the net-zero CO2 emissions target in GB at the lowest annual operating costs. It was shown that CCGT generator capacity is required to mitigate the impact on the electricity transmission network due to the variability of renewable generation. Battery storage systems are proposed to replace CCGT plants and further reduce the use of natural gas