Integrated decarbonisation strategies for the electricity, heat, and transport sectors

Abstract

The rapid climate change experienced at the beginning of the twenty-first century is intimately entwined with the increase in anthropogenic greenhouse gas (GHG) emissions resulting from the growth of fossil fuel consumption in all energy sectors. By 2050, not only these energy sectors must eliminate GHG emissions: electricity, heat, transport, but also those sectors should be closely coupled to achieve maximum synergy effects and efficiency. In this context, this thesis develops integrated models to assess decarbonisation strategies for a variety of complex energy system transitions, including the electricity, heat and transport sectors. Firstly, the thesis proposes a novel single-year, integrated electricity, heat and transport sectors model that considers integrating the hydrogen supply chain while optimising the system’s investment and operation costs and covers both local and national levels. A series of studies are then carried out to evaluate different integrated decarbonisation strategies for the future low-carbon energy system based on the single-year integrated multi-energy optimisation model. Secondly, this thesis evaluates the economic performance and system implications of different road-transport decarbonisation strategies and analyses the electricity sector decarbonisation synergy. Great Britain (GB) case study suggests that transport electrification should be carried out with smart charging to reduce the additional cost on the electricity sector expansion. Hydrogen fuel cell vehicle (HFCV) can be combined with electric vehicle (EV) to reduce the system of increased peak demand due to road transport’s electrification. However, when EV enables smart charging, the case for HFCV becomes less compelling from a system perspective. Their penetration is limited by their higher capital costs and lower efficiency compared to EV. The results also clearly demonstrate a synergy between the hydrogen used in the electricity and transport sector. The integration of hydrogen-fuelled generation can reduce the overall system cost by enabling more investment in renewable energy and reduce the need for the firm but high-cost low-carbon generation technologies, particularly nuclear and gas with carbon capture and storage (CCS). The integration of power-to-gas (P2G) facilities can increase the integration of wind power capacity. Additionally, the heat sector’s decarbonisation is one of the key challenges in achieving the net-zero target by 2050. This thesis evaluates the integrated decarbonisation strategies for the electricity, heat and transport sectors involving hydrogen integration. A study compares the economic advantages under the deployments of P2G hydrogen production and gas-to-gas (G2G) hydrogen production and the associated implications for overall system planning and operation. The results demonstrate that hydrogen integration through the G2G process brings more economic benefits than the P2G process; combining P2G with G2G can yield further cost savings. The results also clearly show the changes in the electricity side driven by the different hydrogen integration strategies. The integration of hydrogen will promote hydrogen boiler (HB) deployment, which will dominate the heating market, combined with the heat pump (HP). From the perspective of the transport sector, the development of HFCV is positively related to the integration cost of the hydrogen system, especially in the demanding carbon scenario. Going further, the single-year, multi-energy integrated optimisation model has limitations, focusing only on short-term investment operations and unable to deal with the long-term system planning problem. Therefore, this thesis presents a novel transition model for the electricity, heat and transport sectors, operating in full hourly resolution and taking into account sectoral coupling, simulating future energy systems’ transition to low-carbon energy production. Finally, considering the different difficulties and speeds of transition in the different energy sectors and the complementary effects between energy sectors, designing individual sector transition cannot provide a systematic view, as the most valuable sector coupling effects are overlooked, and sector separation consideration underestimates the complexity of the optimal transition pathway. This thesis designs three integrated energy system transition pathways based on the multi-year transition model, placing sector coupling and considering a full range of low-carbon technologies, enabling fundamental insights into the optimal energy system transition pathway to achieve the net-zero target by 2050. The GB case study results demonstrate that electrification combined with hydrogen integration will be the most cost-effective pathway. Hybrid heating technologies and EV will be the leading options in the heat and transport sector for decarbonisation. Bioenergy will play an essential role to offset carbon emissions from the other energy sectors. Cross-energy flexibility is vital to achieving a cost-effective transition pathway. Based on the above results, the policy recommendations for the net-zero target achieving can be made for policymakers.