Resumen de Flexibility and stability constraints in the future power system with a high share of variable renewable energy: the role of new generation and storage technologies (hydrogen)
The increasing penetration of Variable Renewable Energy (VRE) causes several challenges in power systems because of their intermittency and unpredictability.
Therefore, different alternatives and mechanisms have been addressed in the literature to deal with variability and provide flexibility to the grid. However, the performance of the future power system and the role of new generation and storage technologies have not been previously analysed, considering flexibility and stability constraints for different climate conditions. Accordingly, a rule-based power system model called "Future Renewable Energy Performance into the Power System" (FEPPS) has been developed in this thesis to fill these gaps. Spain and Great Britain were used as case studies.
FEPPS was generated using historical and theoretical data to set flexibility parameters for projecting and modelling the existing and new power generation technologies. The model followed a merit order approach and was developed from historical data from the transmission system operator and inputs from the Ten-Year Network Development Plan (TYNDP) developed by the European Network of Transmission System Operators for Electricity (ENTSO-E). FEPPS was validated using historical data from the Spanish Transmission System Operator (TSO). Results suggest that ambitious targets of the national and international scenarios for VRE penetration and decarbonisation in the power system cannot be achieved when flexibility and inertia constraints are considered.
The resulting share of VRE in FEPPS was significantly lower than in these scenarios.
Considering existing technologies in the power system, no scenario meets the Paris emissions targets due to the significant need for natural gas combined cycle (NGCC) to provide inertia and cope with variability. Therefore, the first part of this thesis shows the need for new low-carbon and storage technologies to contribute to the decarbonisation of power systems.
A sensitivity analysis showed that Spain could benefit from an increased solar thermal capacity to further decarbonise the electricity grid before including new technologies. In the second part of this thesis, batteries were irrelevant, reaching a very low-capacity factor in all scenarios. Polymer electrolyte membrane (PEM) and heavy-duty vehicle polymer electrolyte membrane (HDV-PEM) fuel cells reached higher capacity factors.
Therefore, fuel cells could be transitional technologies for Spain, while they could have a significant role for Great Britain in the short and long term. This is because the power system of Great Britain has a lower critical inertia level compared to Continental Europe.
Adiabatic compressed air energy storage (A-CAES) reached low-capacity factors in the short term. However, in the long term, its role would be conditioned by the capacity of the electrolysers for hydrogen production because both technologies would use the curtailment of VRE.
FEPPS has demonstrated that hydrogen has a crucial potential to contribute to a nearzero emissions power system. Hydrogen turbines for electricity generation (H2-CC) reached high-capacity factors in all scenarios for the short and long term (~40–50%).
Hydrogen turbines provide flexibility, allowing the most significant substitution of NGCC, thus playing a crucial role in grid decarbonisation. Hydrogen storage has been analysed and included in the model to provide flexibility. The resulting storage was 18 days of average demand for Spain and 9 for Great Britain, which is below the theoretical potential for hydrogen storage using salt caverns. Hydrogen production from electrolysis in all scenarios was not sufficient to meet the power system requirements; therefore, an external supply of renewable hydrogen from biomass was assumed.
Only the inclusion of new generation technologies and large-scale energy storage will allow the analysed power systems to meet the Paris benchmarks (both in the short and long term). In addition, climate conditions strongly impact the final curtailment levels and hydrogen storage requirements.
