Assessment of power-to-power renewable energy storage based on the smart integration of hydrogen and micro gas turbine technologies

Power-to-Power is a process whereby the surplus of renewable power is stored as chemical energy in the form of hydrogen. Hydrogen can be used in situ or transported to the consumption node. When power is needed again, hydrogen can be consumed for power generation. Each of these processes incurs energy losses, leading to a certain round-trip efficiency (Energy Out/Energy In). Round-trip efficiency is calculated considering the following processes; water electrolysis for hydrogen production, compressed, liquefied or metal-hydride for hydrogen storage, fuel-cell-electric-truck for hydrogen distribution and micro-gas turbine for hydrogen power generation. The maximum achievable round-trip efficiency is of 29% when considering solid oxide electrolysis along with metal hydride storage. This number goes sharply down when using either alkaline or proton exchange membrane electrolyzers, 22.2% and 21.8% respectively. Round-trip efficiency is further reduced if considering other storage media, such as compressed- or liquefied-H₂. However, the aim of the paper is to highlight there is still a large margin to increase Power-to-Power round-trip efficiency, mainly from the hydrogen production and power generation blocks, which could lead to round-trip efficiencies of around 40%–42% in the next decade for Power-to-Power energy storage systems with micro-gas turbines.