The growing interdependencies between natural gas and power systems, driven by gas-fired generators and gas compressors supplied by electricity, necessitates detailed investigation of the interactions between these vectors, particularly in the context of growing penetration of renewable energy sources. In this research, the role of an integrated approach against a decoupled approach for operating natural gas and power systems is assessed. Then, a decomposition method based on outer approximation with equality relaxation approach is proposed to solve the mixed integer non-linear problem of integrated operation of natural gas and power systems, which significantly increased the efficacy of the optimisation achieving nearly 40% reduction in computation time.

The value of flexibility options such as battery storage, demand side response, gas-fired generators, power-to-gas, and flexible gas compressors in the operation of integrated gas and electricity systems in GB 2030 energy scenarios is quantified for different levels of penetration of renewable generation. The modelling demonstrates that the flexibility options will enable cost savings in the annual operational costs of natural gas and power systems (up to 2.3%) and reductions in corresponding emissions. On the other hand, the analysis carried out indicates that deployment of flexibility technologies will reduce the interaction value between power and natural gas systems.

Finally, an integrated expansion planning strategy for natural gas and power systems with consideration of investments on flexibility options is proposed. The results indicate that the flexibility options could play an important role in meeting the emission targets in the future. However, the investment costs of these options highly impact the future generation mix as well as type of reinforcements in the natural gas system infrastructure. In low investment costs of the flexibility options, up to £24.2b annual cost savings in planning and operation of natural gas and power systems could be achieved, compared to the case that no flexibility option is considered.