In theory, green hydrogen (H2) could be produced in abundance at sea using electricity from wind turbines, then transported to land. The biggest drawback to this renewable energy cycle, however, is that it has never been tried in a maritime setting, due to high costs of set-up. This is the background to the joint project OffsH2ore led by the company PNE (Pure New Energy). Over three years, experts in their field investigated all aspects of how offshore H2 production could be achieved in the most economical way – all from PNE’s R&D centre in Cuxhaven, Lower Saxony.

The partners began by simulating a fictious offshore wind farm in the German North Sea that was directly connected to a 500 MW PEM electrolysis platform capable of producing 50,000 tonnes of green hydrogen a year. All the essential process steps were then interrogated from a technical and economic perspective from electrolysis to storage, logistics, electrical engineering and water supply – and suitable solutions were developed.

Water for electrolysis was provided by desalinating seawater via a multi-effect distillation process. The H2 was then purified, dried and compressed to 500 bar and theoretically loaded onto a transport ship capable of delivering between 400 and 500 tonnes of H2 per trip from the platform to shore.

A highly specialised H2 gas loading system had to be developed for the custom-designed ship. The team also evaluated alternative storage and transport concepts such as pipeline and liquid H2, and looked at the framework requirements for standards, regulations and certification relating to production and supply.

Overall, OffsH2ore presented a credible techno-economic case for an offshore supply chain based on compressed gaseous H2, calculating levelized costs of six to seven euros/kg for delivery to the port side. However, the consortium considered the earliest date for commercial operation would be 2030.