Hybrid ships’ attractions grow
Electric-powered vessels are broadening their appeal, reaching beyond the traditional close to shore market
REDUCING atmospheric pollution and enhancing energy efficiency from ships, tugs and ferries have been the primary drivers for hybrid power systems involving an energy storage system or battery, many years ahead of the International Maritime Organization’s decarbonisation roadmap announced in 2018.
Most of the pure battery and hybrid vessels in service and on order tend to operate close to shore, such as ferries and tugs, or vessels that spend much of their time in DP (dynamic positioning) mode. Demand for all these vessels is growing, and while most experts agree that the benefits of battery systems for deepsea ships are less compelling, there is also growing interest in that sector.
For shuttle tankers such as those ordered by Altera Shuttle Tankers (formerly Teekay), the attraction is that these ships operate in DP mode when loading. For expedition cruise ships, it is the ability to operate cleanly and silently — if only for a short time — in fragile and sensitive environments.
For vessels such as PCTCs (pure car/truck carriers) in operation or under construction, or for bulk carriers and tankers, increasingly strict Energy Efficiency Design Index ratings may be a reason for demand, even though energy storage systems are not yet fully recognised in EEDI calculations. Another niche area of demand is in small coastal bulkers, a rising trend, especially among Norwegian owners.
Sverre Eriksen, senior principal approval engineer at DNV GL – Maritime, says the classification society is receiving a lot of interest from customers looking to initiate battery-powered or battery hybrid vessel projects. In addition, he notes that one battery-powered or battery hybrid vessel has entered into operation every week, although this has slowed somewhat in the northern autumn, perhaps as a result of the ongoing Covid-19 crisis.
Mr Eriksen adds that for early pioneers in battery use, the experience has generally been positive. Payback time in terms of reduced fuel use has not always matched expectations, but this has been impacted by falling bunker prices. Capex costs were also higher than expected in some cases, but on the other hand, early adopters have enjoyed reduced maintenance costs and time, based on less use of gensets as well as the expected improvements in operational efficiency.
Battery technology is constantly improving and, assuming energy density can increase, the attraction of hybrid ships will continue to grow. Price is also a factor that needs to be taken into consideration. While prices on land are decreasing rapidly, the cost of a maritime battery system in 2019 was around $600-1000/kWh, which remains considerably higher than in the automotive industry.
Thus far, all but a small number of the battery systems fitted to vessels have been Lithium-ion. These are the most widely prevalent batteries in all industries, but recently concerns have grown over the working conditions for miners of cobalt, an essential element of the battery.
One mitigating development is to reduce the cobalt used, in favour of nickel. Not only does that address the ethical questions about miners, but nickel is cheaper and has the potential to increase energy density. If it has a downside, it is that with present technology, nickel has a shorter lifetime and has a decreased thermal stability.
Looking further ahead, solid state batteries could offer some advantages. According to Henrik Helgesen, senior environmental consultant at DNV GL – Maritime Advisory, they have the potential to not only increase energy density by a factor of three, but also have some safety advantages over current batteries. On the downside, they currently have a high price tag and are used in higher-end automotive vehicles. Nevertheless, the additional range that they offer, along with increased safety, could be sufficient to overcome the current price hurdle.
Whatever direction battery technology is likely to take over the coming years, there is no disputing that it is cleaner at the point of use than burning fossil fuels. And it is equally easy to see the efficiency and environmental advantages that battery energy storage systems offer for some vessel types. How much of the fleet will look to take advantage of hybrid and battery systems remains to be seen, but if these trends continue, the future of shipping might just be a bit more electric.