Hydrogen has a very high energy content: for the same weight, it contains up to three times more energy than diesel, and 2.5 times more than natural gas. That said, we know how to store natural gas in tanks or pipelines. Storing hydrogen is more difficult.

Hydrogen is an extremely light gas which occupies a substantial volume under atmospheric pressure conditions. As a result, storing it requires high levels of pressure. The Energy Observer tanks store hydrogen at 350 bars, which is the current standard for buses, for example. Hydrogen cars, such as the Toyota Mirai, stock hydrogen at 700 bars.

The Energy Observer compressor operated for 1,469 hours for the first level at 180 bars and 1,105 hours for the second level at 350 bars. The levels of compression in the H2 production supply demanded a lot attention from the crew during the first 16 months at sea; 11 membranes were destroyed due to different factors which polluted the procedure.

The pollution was not necessarily due to the marine environment, and highlights the importance of a high-quality and rigorous installation. Analysis and optimisation during the winter period should solve the problem. And the Energy Observer team plan to test a new generation of high-pressure electrolysers to reduce weight and simplify the system.