Life Cycle Greenhouse Gas Emissions of Hydrogen Supplied Chains via Offshore Wind Farms Utilizing Compressed Gaseous Hydrogen, Liquefied Hydrogen and Ammonia: A Case Study of China

The development of promising offshore wind farms contributes to the cleanliness of the power system, and hydrogen (H2) is a potential energy carrier to address the challenges of delivering power from long-distance offshore wind farms. In this work, a life cycle evaluation (LCA) model for green hydrogen production from offshore wind farms is developed. The greenhouse gas emissions (GHG) and fossil energy consumption of compressed hydrogen (G-H2), liquefied hydrogen (L-H2) and liquid ammonia (L-NH3) as energy carriers are compared, and the sensitivity of GHG to wind farm load factor and transport distance is analysed. The results show that the G-H2 route has the lowest GHG emissions of 633.2 (gCO2eq/kg H2) and fossil energy consumption of 7.25 MJ/kg. In contrast, the L-NH3 route possesses the highest GHG emissions of 732.6 (gCO2eq/kg H2) and fossil energy consumption of 8.134 MJ/kg H2. In addition, the sensitivity coefficients of GHG emissions to transportation distance and annual load factor of offshore wind farms are investigated, and the sensitivity of the annual load factor reached between 0.9 and 1.4, following the order of L-H2 > L-NH3 > G-H2. In addition, the sensitivity coefficient of transportation distance is only reflected in G-H2 and reaches a remarkable value of 0.4 at 500 km. The results indicate that the G-H2 route has the lowest greenhouse gas emissions and fossil energy consumption at distances of less than 70 km offshore and that beyond 70 km, L-H2 is the preferred alternative. This work provides a comprehensive life cycle perspective to facilitate the selection of energy carriers for offshore hydrogen production.