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Marine Propulsion & Auxiliary Machinery

Marine Propulsion & Auxiliary Machinery

Designing in an energy boost

Tue 05 Dec 2017

Designing in an energy boost
Jan-Erik Räisänen, head of new technology, Foreship

A leading engineering design consultant believes it has ways to achieve major energy savings using waste heat energy, energy storage and fuel cells

In March 2017, Foreship appointed Jan-Erik Räsänen head of new technology. Formerly with ABB, Mr Räsänen is an acknowledged expert in shipboard energy optimisation, and one whose breadth of experience in shipboard battery power and fuel cell development would be hard to better.

Foreship, a naval architecture and marine engineering consultancy, has made a speciality of advising the world’s leading cruise ship companies on how to optimise ship structures and systems for energy efficiency. At a truly exciting time for shipboard energy options, the head of new technology is revelling in his freedom to offer objective technical advice.

As with everything at Foreship, projects seeking to optimise energy use begin at the design level for the newbuild or conversion. “The starting point is to establish what the owners want to achieve and their thoughts on how to go about it,” said Mr Räsänen. “Then we analyse their wishes and make recommendations, advising them on the goals that are achievable and where we might have to look at alternative solutions.”

Describing the working process for Foreship, Mr Räsänen told Marine Propulsion: “You need to have an overall picture of the energy balance in terms of what you produce and where it goes.

One idea is reduce consumption as much as possible – find technologies that maximise your energy use. The other thing is to maximise the use of energy that is otherwise wasted.

An overall understanding of the energy balance between production and consumption is needed, so that insight can be offered into where the energy should be used and where it is typically wasted. We need to establish what the energy sources of the vessel are/will be, and where efficiency gains might be available.”

Efficiency improvements could come from considering new energy storage techniques (either electrical or thermal), but they might also result from reclaiming efficiencies from existing systems. What is important is the complete energy flow of the vessel, he says.

“You could, for example, describe waste heat energy as an alternative energy source that can be reused by being fed through absorption chillers, organic Rankine cycle or steam turbines,” said Mr Räsänen.

In the past, container shipping companies have used steam turbines to reclaim the plentiful waste heat generated by 60-70 MW two-stroke engines. Until recently, cruise ship engines generating on average 9-16 MW have not been large enough to justify sizeable steam turbines, especially when considering the typical operational profile of a cruise ship. But “we are seeing a change because now it is becoming possible to fit small steam turbines on these ships, partly because of lower heat demand in traditional steam processes with LNG fuel and freshwater production, as well as improved waste heat energy recovery systems,” Mr Räsänen explained. Foreship is undertaking several feasibility studies evaluating next-generation waste heat recovery systems for cruise ship owners.

“One goal is to minimise the use of oil-fired boilers, saving fossil fuel that would otherwise be burned while also serving the combined needs of the galley heating process, fuel heating, the reverse osmosis plant producing fresh water and laundry services, for example,” Mr Räsänen said.

There is swiftly emerging potential for cruise ships to exploit battery power, with stored energy deriving from a variety of sources. “Cruise operators tend to have a better picture of their energy use because they own and operate their own vessels. With merchant vessels, you’re never sure who pays for what, so it’s much harder to prescribe how to address problems,” said Mr Räsänen.

Mr Räsänen explained that there are ship types that have been natural candidates for battery power, typically ferries and shortsea vessels requiring power in short bursts, or vessels used in the oil and gas sector that spend a lot of time idling. Others have not been such an easy fit, even though a hybrid solution with batteries and conventional engine can improve fuel efficiency by up to 15%.

Customer interest “has been there the whole time,” but the objection to battery technology in the cruise market has always been based on space and cost, Mr Räsänen said. This objection is being overcome. Foreship has already been involved in a feasibility study to evaluate the use of battery power for a leading cruise operator.

“Most cruise operators are keen to do something. They realise there are savings to be gained. Technology is developing very fast, so something that wasn’t feasible yesterday is feasible today,” he said.

Furthermore, shipboard battery options are fast-developing. In late 2016, one battery maker was offering a 6.5 kWh battery with dimensions of approximately 36 cm by 30 cm by 30 cm. Six months later, the same supplier is offering a 9.7 kWh battery of the same size. “Typically, a high charge and discharge rate has been one of the major criteria to minimise the size of the batteries due to the big physical size in space and weight,” Mr Räsänen said. “But with increased density and lower price per kWh, we see a step away from this. With a moderate charge and discharge rate, we expect longer battery lifetime as well.”

Early cruise adopters of battery technology include ship operators calling in particularly sensitive areas, and Mr Räsänen acknowledged that it can be difficult to move from case study to generalisation in terms of uptake. But he cited as heralds of change recent moves by Statoil to contract seven more supply vessels with hybrid battery operation and to invest in a lithium ion battery manufacturer to develop energy storage for dynamic positioning duties.

“It’s not likely that we will see large numbers of ships operating solely on batteries, but I believe 40-60% of all vessels could benefit from auxiliary battery load exploitation to support peak load shaving,” said Mr Räsänen. “A small number of ships – say, 5% of the fleet – will also use batteries for specific duties: in the cruise sector, for example, battery power could be useful during port entry, where the environmental gains would be strong.”

Foreship has recently seen an increased interest in fuel cells in parallel with combustion engines to improve fuel efficiency. For the time being, Mr Räsänen believes the most promising of the available technologies is polymer electrolyte membrane (PEM), whose use in the automotive industry has brought a lower per energy unit price than the less mature solid oxide fuel cell (SOFC). But he added that SOFC efficiency can be raised up to 65-70%, whereas PEM has a lower efficiency of around 45%.

Mr Räsänen explained that while both technologies use hydrogen as fuel, other types of fuel (such as LNG and methanol) can be used. LNG and methanol, though, emit pollutants and need a reforming process to produce hydrogen. After the reforming process, carbon monoxide and hydrogen remain. Mr Räsänen noted that while SOFC plants can utilise both carbon monoxide and hydrogen as fuel, the carbon monoxide needs to be removed in the case of PEM, lowering the overall efficiency and complicating the fuel treatment process.

“We are closely monitoring the development of fuel cell technology. We don’t actively promote it because we don’t believe the technology is mature enough for use on a large scale. But it is coming,” Mr Räsänen said.

As to whether these ideas are purely theoretical, Mr Räsänen said: “Maybe. Maybe not. Let’s put it like this: we very rarely do things that don’t have a meaningful end to the story.”

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