Assessing the feasibility of utilising tidal stream energy for green ammonia production

Thesis

The climate crisis is driving policy makers, energy companies and chemical industries to accelerate the transition from conventional high-carbon ammonia to low-carbon and zerocarbon (green) ammonia. Ammonia is produced on a vast scale globally and is predominantly used for fertilizers but has a potential use as an energy vector and maritime fuel. Utilising variable renewable energy (typically onshore solar or wind) for green ammonia production requires expensive energy storage. Tidal stream energy is a novel energy source for green ammonia production and could be an ideal energy source, given its phasing potential and predictability. This thesis presents the first analysis of green ammonia production using tidal stream energy and the first analysis of green hydrogen and ammonia production using tidal phasing.

A levelized cost of ammonia (LCOA) reduction of up to 18% can be realised for offshore green ammonia production when tidal stream energy is added to offshore wind energy in the Pentland Firth, a high-energy tidal stream energy site. Tidal stream energy is competitive against (or, at least, an ideal complement to) offshore wind energy for onshore green ammonia production in six tidal hotspots around the world, despite offshore wind being a cheaper energy resource.  

Tidal stream energy in the Pentland Firth (UK), the Alderney Race (UK), and the Minas Passage (Canada) can deliver an LCOA competitive with conventional green ammonia today. Tidal phasing reduces the LCOA by 6% in the English Channel, with onshore green ammonia production. However, both nearby and high-energy turbine locations are likely required for the phased tidal stream energy LCOA to be competitive with conventional green ammonia or conventional fossil fuel-based ammonia. The predictability aspect of tidal stream energy is likely to be its most significant advantage over other renewable sources for green ammonia production.

Authors: Driscoll, H

• DOI: 10.5287/ora-n6poezdoy
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English