Optimal Design and Operation Planning of VPPs Based on Hydrogen Storage and Hydrogen Combined Cycle

Abstract

Virtual Power Plants (VPPs) and Multi-Energy Systems (MESs) are aggregated energy systems comprising renewable energy sources, energy storage systems and dispatchable units. The presence of such diverse systems unlocks the possibility of a near-zero carbon emission energy generation while overtaking the main drawback of renewables sources that is their lack of control. Among the different energy storage systems, large scale (seasonal) H2 storages (e.g. salt cavern or depleted oil field) would allow shifting the excess solar energy from the hot to the cold season. High round-trip efficiency (electricity to electricity) and unpaired operational flexibility could be achieved using H2 in state-of-the-art combined cycles. This work investigates the optimal design and operation of a fully renewable VPPs integrating PV panels, batteries for short-term storage, electrolyzers, H2 seasonal storage and H2-fired combined cycles. The optimal design and optimal yearly operation of such complex VPP are formulated as Mixed Integer Linear Programs (MILP) and solved to global optimality imposing to meet the highest possible fraction of the electricity demand profile. Results indicate that the optimal VPP design features a 490 MWhel of battery, 687 MWel of PV panels, 392 MWel of electrolyzer and requires a minimum H2 storage size of 168 GWhH2,LHV to power a combined cycle of 58 MWel. In case of a geological H2 seasonal storage availability, the resulting cost of generated electricity is above 430 $/MWhel, considerably higher with respect to the average electricity prices in Italy (in the range 50–80 $/MWhel) underlining the need of achieving better power-to-gas efficiencies and lower specific investment costs of conversion technologies in the next years. Furthermore, if the H2 storage needs to be built on purpose, the resulting cost of electricity would be even higher.