Putting the Safety into Battery Driven Propulsion
Interview with PBES’s Grant Brown in the September issue of The Navel Architect. Access the digital issues here
Whether for hybrid or fully-powered, advances made in lithium-ion batteries have allowed the technology to quickly establish itself as a viable solution for marine propulsion. Since the launch of the first diesel-electric hybrid ferry, the 43m ro-ro MV Hallaig, in December 2012 the scale and ambition of such projects has moved on leaps and bounds with new projects, both retrofits and newbuildings, announced almost monthly.
Ferries, offshore and smaller vessels remain the focus for battery-powered innovation, spurred on in no small measure by the impetus of tightening emission-control regulations. However, Norwegian travel company Hurtigruten’s announcement in September 2016 that its forthcoming polar expeditionary ships Roald Amundsen and Fridtjof Nansen (due for delivery in 2018 and 2019 respectively) would deploy sustainable hybrid technology is seen by many as a watershed moment. And while its seems unlikely that we will see battery-powered vessels engaged in long-haul transportation any time soon, it no longer seems beyond the realms of possibility.
One company with a vested interest in the technology’s continued progress is Canadian manufacturers, Plan B Energy Storage (PBES). Founded in early 2015 by Brent Perry, the former CEO and founder of rival battery suppliers Corvus Energy, PBES has quickly established itself with an outspoken commitment to marine energy storage ‘done right’, placing a strong emphasis on quality.
Grant Brown, PBES’s VP for Brand and Marketing (and, like Perry, also one of the co-founders of Corvus) explains:
“Due to our experience with other products and projects in the past, when we designed this battery we really looked at how we could make it as safe as possible. The last thing anybody wants is a fire on board a ship. Lithium fires are very unpredictable and difficult to extinguish when they start propagating.”
In order to achieve this, PBES incorporated a number of unique safety features into its batteries. The most important of these, according to Brown, is a patented liquid cooling system they call CellCool.
“CellCool liquid cooling does two things: it provides a safety feature in that it prevents our battery going into thermal runaway [when the heat generated within the cell causes a reaction between the cathode material and electrolyte], because the cooling system can extract more heat than the cells can produce. We’re the only battery in the world that can actually prevent thermal runaway from occurring, not just spreading from cell to cell.”
While other battery systems rely on air cooling, the PBES method is similar to that found in the engine block of a car. Water is circulated through and around the components before exiting. Because the water is low pressure (around 4psi) it doesn’t put strain on the internal seals and components of the cell.
The cooling system is further enhanced by the use of cooling elements within the holders of the battery cells. Unlike many of their competitors, PBES has elected to use aluminium housing for their cells, rather than the more typical (and cheaper) glued-in plastic casing which can’t be serviced and requires the replacement of the entire battery. It also facilitates a unique CellSwap system which makes it possible to replace the cell core — each cell is roughly the size of a magazine and slots into the 10mm thick aluminium housing — without any interruption to the vessel’s service, not to mention cutting down on electronic recycling.
Safety features are integral to every aspect of the PBES battery design, says Brown. The battery’s contactor is built-in and opens up in such a way in that there is no voltage or danger of electrocution while it is inactive. Another is the patented E-Vent system, which channels fumes away through a chimney that leads outside in the event of thermal runaway. Brown says:
“The reason for this is that when lithium cells start to combust they create a combination of hydrogen gases that is very flammable. The smoke in a lithium fire is actually hydrogen gas, you can’t have that in the engine room of a vessel where the firefighters wouldn’t even be able to re-enter the room because of the potential for an explosion.”
PBES – which has already opened regional plants in Norway, Denmark and China – produces two battery solutions: the PBES Power 65, a 6.5kWh (75 ah cells) module optimised for high performance across a five-year lifespan, and the PBES Energy 97, a 9.7 KW/h (112 ah cells) battery comprised of the same parts but a higher energy density cell. Brown explains:
“It’s a 30% decrease in size, weight and ultimately cost. With cell swap it means the owner can start with one type of cell and potentially change them if the ferry changes its route and has different energy needs.”
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