Estimating the efficiency of a PEM electrolyzer fed by a PV plant in NEOM City

The NEOM City microgrid, designed to be free from fossil fuels generation, is proposed to feature energy supply by wind, solar photovoltaic (PV), concentrated solar power (CSP) with internal thermal energy storage (iTES), and nuclear, plus energy storage by battery (BES), hydrogen (HES) and external thermal energy storage (eTES). The operation of a 100 MW PEM electrolyzer cell (EC) feed with a 100 MW solar PV plant, which is part of the HES, is then analyzed. Based on operational data of old plants, the average annual efficiency of the PEM EC plant is assessed at 0.653, close to the rated power efficiency of 0.676, and higher than the maximum power efficiency of 0.604. Given the continuous improvements in PEM electrolyzers, a novel plant is expected to deliver an efficiency of at least 0.1 more, at a 0.753 annual average. The manuscript also demonstrates the extensive variability of solar energy from daily to annual timescales and its impact on the fluctuating electricity input to electrolyzers, affecting hydrogen production. It emphasizes the importance of choosing suitable electrolyzers and integrating short-term energy storage to stabilize the power supply, and it innovatively examines green hydrogen production variability across multiple time scales.