Hydrogen production onboard could help ship operators cut CO2 emissions without the challenges of storing high volumes of the volatile molecule.
Hydrogen has largely been written off as a fuel for long-distance shipping. While a few hold-outs suggest otherwise, storage challenges around low volumetric energy density and cryogenic temperatures have dissuaded shipping’s mainstream from seriously considering bunkering hydrogen.
The storage challenge is another of the endless trade-offs ship operators face when choosing clean fuels. That difficulty aside hydrogen would have strong potential, usable in both fuel cells and as a drop-in fuel with existing engine technologies. But what if you didn’t need to bunker it to take advantage of the emissions benefits hydrogen offers?
Renewable technology company e1 Marine has received approval in principle (AiP) from Lloyd’s Register (LR) for a hydrogen generator that uses methanol and water to produce fuel cell grade hydrogen. The system, developed under a project that also includes tanker operator Ardmore Shipping and shipowner Maritime Partners, will power the M/V Hydrogen One, expected to be the world’s first methanol-fuelled towboat when it enters service next year.
“Methanol is an ideal hydrogen carrier for shipping,” says Dr. Benjamin Jäger of the Fraunhofer Institute for Ceramic Technologies and Systems IKTS. “Its energy density is twice as high as liquid hydrogen, so the on-board methanol tanks only need to be half the size. It can also be transported safely: Even if a tank leaks, there is no acute environmental risk.”
The Fraunhofer Institute is a partner in the HyMethShip project, which has managed to scale the steam reformation process converting methanol to hydrogen so that it can enable engine propulsion of up to 1MW. A mid-term goal of 20MW propulsion systems would enable use of reformed hydrogen by cruise and container vessels.
According to another system designer, US-based RIX Industries, methanol-to-hydrogen generators require no major retrofit of ship infrastructure to deploy hydrogen-on-demand. With proper cleaning, tanks currently used for HFO storage can instead store liquid methanol at ambient temperatures, with no cryogenics or high-pressure storage.
The rush of recent system developments coincides with a spate of investments in methanol-fuelled vessels from companies including methanol tanker operator Marinvest, Maersk, Xpress Feeders subsidiary Eastaway and a joint venture between MPC Container Ships and North Sea Container Line. As the methanol orderbook and bunkering infrastructure grows, hydrogen reformation could offer even greater propulsion flexibility for ship operators if the added efficiency in combustion or fuel cell use can outweigh conversion process losses.
Reformation of hydrogen is also possible from LNG. In late 2021 a consortium comprising RINA, ABB, Helbio and the Liberian Registry revealed a system that combines LNG with steam to produce hydrogen and CO2. The hydrogen produced will be used directly in a mix with natural gas in internal combustion engines or in fuel cells, thus eliminating the need for hydrogen to be stored onboard. The CO2 will be liquefied using the cryogenic stream of LNG that would be used as fuel anyway, and later disposed ashore for carbon storage. Tankers can use the stored CO2 as inert gas during discharge.
The idea of LNG from hydrogen has been brewing for some time. As early as 2017, a research paper highlighted a particularly useful potential application for reforming hydrogen from LNG. Gas carriers which would otherwise divert excess boil-off gas from their cargo to a gas combustion unit could instead convert it to hydrogen for use in engines. Other applications are likely to emerge, with hydrogen enabling sailing with no air pollutants if required at ports, for example.
The transition to clean fuels in shipping is often described as a revolution; with new technologies that could enable on-demand hydrogen use on a wider range of vessels, perhaps it should be relabeled a reformation.