Due to the increasing penetration of renewable energy sources on the grid, the traditional power plants (PP) and the combined cycles, in particular, are increasingly forced to operate in discontinuous mode with continuous load changes. In the present work, two power-to-fuel-to-power processes are investigated as potential solutions to improve the Combined Cycle Power Plant (CCPP) flexibility by adsorbing and storing the electrical energy produced by the PP and not sold to the grid. The analysis was carried out on the Power-to-Hydrogen-to-Power (P2H2P) and Power-to-Ammonia-to-Power (P2A2P) systems investigating and comparing the process in terms of round-trip efficiency, storage energy density, and plant footprint. Despite the P2H system being more competitive from the efficiency point of view, it presents critical issues related to the energy storage density and system footprint as consequence. These problems can be overcome by ammonia which resulted in a much more effective energy storage medium.
Keywords Power to fuel systems, energy storage, power plant flexibilization, hydrogen, ammonia, decarbonization.