Optimal phasing of tidal stream power around the British Isles and within the English Channel for green ammonia production

Green ammonia, a fertilizer, energy carrier and shipping fuel, is a key zero-carbon chemical for the transition to net zero, but is produced in minimal quantities today, predominantly from wind and solar renewable energy. The waters around the British Isles and within the English Channel contain immense potential for predictable tidal stream energy, which is vastly underutilized today. The Haber-Bosch reactor, which is used to produce ammonia, is not flexible, requiring a smooth (consistent) power input. This paper analyses the potential for exploiting the difference in phase of tidal stream currents (tidal phasing) in different locations to optimize the aggregate power profile for the purpose of green ammonia production. A genetic algorithm is used to optimize the location of the turbines. For the four regions analysed in 2050, phasing is always beneficial – the levelized cost of ammonia (LCOA) is reduced by 6–13 % compared to an unphased, single turbine of the same capacity factor (CF), excluding cabling costs. Phasing is particularly evident in the Bristol Channel and in Alderney as their phased power profiles have infrequent zero or low power values. Although the cabling costs are significant, the tidal capital cost (CAPEX) always contributes more than the cabling CAPEX to the LCOA.