Team seeks to turn fuel-cell ship into battery hybrid vessel

Researchers in Norway are hoping to turn an experimental fuel-cell ship into a battery hybrid vessel in order to improve its efficiency.

A team from research institute Det Norske Veritas (DNV) plans to install a battery system onto the adapted commercial ship Viking Lady to operate alongside its molten carbonate fuel cell (MCFC), which is powered by liquefied natural gas (LNG).

The battery will help the power system to increase and decrease its output at a much faster rate than the fuel cell can cope with on its own, increasing its efficiency and creating estimated fuel savings of between 11 per cent and more than 20 per cent.

‘The fuel cell can’t handle dynamic load variations very well because it needs to keep a stable operating temperature [of around 600ºC],’ senior DNV researcher Kristine Bruun Ludvigsen told The Engineer.

‘If you need to increase the power you need several hours. It’s important both for the process plants to feed enough fuel in but also to keep the temperature constant.’

Because the fuel cell isn’t used as the Viking Lady’s primary power source, it often needs to have its power output reduced, she added.

‘If you can add a battery, when you normally need to reduce the fuel cell you can charge the battery instead and then make the battery take the dynamic load variation.’

The ship’s fuel cell was first tested for 9,000 hours in 2010 as part of the second phase of the EU-funded Fellowship project to develop an energy system for commercial vessels that was more efficient and had lower exhaust emissions than traditional ships.

It is now awaiting the installation of a 500kWh demonstration battery pack capable of producing 5MW over short periods of time, which is currently being constructed and tested onshore by DNV and its project partner MTU Onsite Energy.

‘A full-scale hybrid installation would be expected to include a 2–3MWh battery pack, but the 500kWh pack is sufficient to demonstrate the technology,’ said Ludvigsen.

Improving the system’s efficiency is vital if it is to become a commercially viable technology for shipping because of the technology’s high costs and limited lifetime.

MCFC emissions contain much less carbon dioxide than those of traditional propulsion systems and no nitrogen oxides (NOx) or suphur dioxide. They also have very few moving parts so create virtually no noise or vibration, and produce large amounts of heat that can be harnessed. But they cost around $3,000/kw to install — 10 times the price of diesel generators.

‘They have a goal of cost reduction to $1,500/kW so no one believes it will come down to the same installation price as the diesel engine. So they have to compete on efficiency,’ said Ludvigsen.