Investigating the role of natural gas and hydrogen in a future integrated energy system

Many countries are working on transitioning towards a carbon-neutral economy by 2050. This has predominantly driven investments towards renewable electricity technologies such as solar and wind generators, driving research to increase energy systems' interconnection. To investigate the role of gas-based vectors in the transition of the energy system, the following sectors are considered, i.e., gas for energy storage, gas for heating, and gas for power generation. Maximizing green hydrogen production in Power to Gas (P2G) systems by understanding 1) stack performance of low and high-temperature electrolyzers and 2) operational modes in response to curtailed renewable electricity could aid potential investors to achieve maximum return on their investment. Progressively increased intermittent operational modes in electrolyzers showed that low-temperature electrolyzers were more resilient to flexible operation (< 7.7% difference in total H2 production) when compared to high-temperature electrolyzers (< 67%). These results indicated that a stack-level understanding of electrolyzers in the integration of the energy system, needs to be incorporated to maximize green hydrogen production. Utilizing the present gas infrastructure for flexible power generation is foreseen as a primary role for natural gas/hydrogen in a low carbon future. A least-cost optimization for systems operational cost in a one-node multi-renewable electricity systems model increased operational costs when large coal generators were progressively replaced with smaller gas generators. The role of reciprocating engines and industrial gas turbines was primarily in providing fast frequency response and reserve regulation. Another pathway for natural gas and hydrogen in a low-carbon energy system is in the heating sector. A detailed investigation of potential decarbonization achievable in Irish building stock that still uses traditional gas boilers for domestic and space heating was analyzed. The study concluded that thermal retrofits and blending of 20% H2 in the gas network alone would contribute to a maximum decarbonization of 34% in Ireland’s heating sector. The studies presented in the thesis provide a novel approach to understanding the use of P2G systems, analyzing the role of gas for heating and flexible gas generators in a future low carbon energy system.