While the cost of hybrid and electric technology has fallen it still represents a significant outlay for owners, but reduced maintenance and increased efficiency can sweeten the initial hit
Can operators amortise their investments based on optimised performance and reduced operating costs? That was the key question panellists were asked at a recent Riviera Maritime Media webinar, sponsored by Corvus Energy and Elliott Bay Design Group, titled ‘The Business Case for Hybrid and Electric Technology’.
Addressing the unique nature of the current energy transition, Elliott Bay Design chief electrical engineer Will Ayers explained “This is not like sail to steam or steam to diesel; there is no single clear-cut solution for this transition.”
He pointed out that one of the exceptional issues at play involved the diversity of vessels and the operating profiles likely to be impacted, which effectively ruled out a one-solution-fits-all approach.
“When we are speaking about a hybrid electric system, there is an obvious challenge,” said Mr Ayers. “We have a lithium-ion rack – 124 kilowatt hours – and a three-gallon jug of diesel, 124 kilowatt hours. So, we are still talking about this 50 to 1 energy density differential.”
Citing examples of plug-in vessels currently operating in the Scandinavian territories, he noted the ongoing use of diesel engines, which he stressed was valid as marine applications – be that overboard searches, vessels in distress, or emergency drydocks – require the ability to operate at a range that would be compromised without such units on board.
Taking up the subject of electric vessels, Aero Kommune project manager, renewable energy Cecilie Larsen moved the conversation onto the innovative e-ferry Ellen, the design of which she has been heavily involved with. Explaining the value proposition behind the vessel, she noted that despite the high upfront costs, the business case for electric vessels is fundamentally solid. “Battery prices are dropping rapidly,” she said. “We conducted a pre-study before the e-ferry project where we predicted battery prices would fall, but we had not predicted they would drop at this rate. That is good news for investment, since the battery pack is still a large part of the extra cost of an e-ferry.”
She also noted potential benefits from avoiding future CO2 taxes and the ongoing value of second-life usage of the batteries, noting “The break-even period can be even shorter when [these are] calculated in.”
“When we come to replace our battery pack, the price will be a quarter of the original cost”
Ms Larsen explained the break-even for the E-ferry prototype compared to a modern diesel alternative is within five to eight years. “A lot of resources have been invested in R&D, design, communication and administration of the project, that will not apply for the next electric ferry in the series. Therefore, the break-even period for the next in line is expected to be within four years of operation,” she said.
Ms Larsen went on to highlight that in the course of the Ellen project, an equivalent battery pack had dropped 50% in price, adding “when we come to replace our battery pack, the price will be a quarter of the original cost.”
She also flagged potential savings in terms of crew costs, explaining the number of crew members needed on an e-ferry is lower than for a conventional ferry, and the reduced maintenance required, owing to fewer moving parts compared to conventional engines.
Cost and safety
Still, the initial outlay for a battery-powered vessel is high compared to a traditionally powered ship, and Spear Power Systems commercial director Jon Diller explained why this was the case, but also why it was likely to change over coming years. “The major markets for lithium-ion batteries are automotive and large-scale energy storage systems for stationary applications, such as at power plants,” he said. “While marine is growing rapidly, it is unlikely to grow to become a significant percentage of the consumption of lithium-ion. For that reason, the attendant costs associated with a maritime lithium-ion battery are significantly higher.”
But he said if the energy content of a cell can be increased, the number of modules and number of streams necessary to reach a certain capacity can be reduced. “The attendant costs associated with those peripheral items will reduce in kind and the overall system price will be lower.”
He predicted that over the next 10 years, solid-state cells would become widely available and commercially sustainable. “We will have a radical increase in energy density and a significant increase in inherent safety,” he said.
“The attendant costs associated with a maritime lithium-ion battery are significantly higher”
As the discussion continued, talk turned to the optimum means of installing hybrid solutions on various vessel types, with Mr Ayers noting “Short-haul vessels are the low-hanging fruit; this is where hybrid electric really has some distinct advantages.”
Danfoss Editron director, marine business line Erno Tenhunen concurred, adding “Due to improving overall energy efficiency, the required battery size and charging infrastructure will be smaller, meaning a smaller total investment.”
He did however note the complications of installing an electric drive in a smaller vessel, which are typically more weight- and space-critical.
“The question is, what kind of system does not have a negative impact on a vessel’s general arrangement but gives all the opportunities the electric system can provide?” he said.
He explained that a decentralised model that fits well into a vessel’s hull might be preferable in certain instances, saying “The installation can be done into existing machinery space, so you can re-use that footprint and system weight and achieve a very compact design, with lightweight, compact components.”
“What kind of system does not destroy the whole general arrangement but gives all the opportunities the electric system can provide?”
Corvus Energy chief commercial officer Halvard Hauso gave further insight into the hybrid electric technology on such vessels. He commented that the power requirement must be sufficient to handle a worst-case scenario and generally, such vessels run at a much lower load than such a scenario would require. This gives an upside to switching to a hybrid configuration. “If you go for a hybrid, you can reduce the size of your engine,” he said. “You add your battery, and together they can do the same job as a big engine, but with much less fuel consumption.”
Mr Hauso also discussed safety, a big concern among those looking to transition to electrical power. He explained that Corvus Energy had been working on thermal runaway solutions and battery cooling for many years. “In terms of battery cooling,” he said, “bulk liquid cooling and air cooling will both work.” But to mitigate thermal runaway he explained the company has employed passive isolation. “That means, even if the cooling is not running and if you are in dock or at a shipyard, the thermal runaway isolation works and goes into an exhaust system and out of the ship.” Reassuringly, he added “Nothing will then happen if thermal runaway occurs from a defect in the battery cell.”
Watch The Business Case for Hybrid and Electric Technology webinar in our webinar library