Decision-making tool for onshore vs. offshore hydrogen production from offshore wind

This paper presents optimisation studies for the combination of high efficiency reversible solid oxide cells (rSOC) with offshore wind farms in the Celtic Sea. Reversible systems can be used both in electrolyser and fuel cell mode, allowing potential benefits from switching between modes depending on the instantaneous condition of the electricity and hydrogen markets. The purpose of these studies is to determine the most cost-efficient method to combine rSOC with offshore wind whilst matching electricity supply with demand. For this, a model in Python for Power System Analysis (PyPSA) is set up which optimizes production, storage and transport infrastructure for green hydrogen from electricity provided by a wind farm. Input parameters include rSOC efficiencies and infrastructure costs for the rSOC system, including the immediate balance of plant around the system, along with costs associated with hydrogen geological storage and energy transport, in the form of electricity (via subsea cable and on- and offshore substations) or hydrogen (via a subsea pipeline). Cost efficiency calculations also include the calculation of revenue from either electricity or hydrogen. A sensitivity study determines the impact of average values and daily or hourly electricity price fluctuations, as well as the impact of the price paid for hydrogen. Selection between on- and offshore hydrogen production is not predetermined but instead carried out during the optimisation calculation itself. Simulations are run for an offshore wind farm for a single year only for a large number of input parameters. The overall conclusions are that if hydrogen prices are 2.5 times higher than electricity prices, dedicated hydrogen production is recommended offshore, since the transport of hydrogen through a 60 km pipeline is cheaper than the transport of electricity through a 60 km subsea cable connection. When electricity prices are high compared to hydrogen prices, reversible hydrogen production is recommended onshore, as in this case, a subsea cable connection is required even if some hydrogen is kept as a gas.