Better together: batteries and fuel cells

As shipping experiments with hybrid propulsion arrangements, batteries and fuel cells are increasingly seen as complementary, rather than competing, technologies

It is five years since the first full battery-powered vessel, the Norwegian ferry Ampere, entered service in May 2015. There were around 55 vessels with batteries fitted at that date; today there are 166 vessels in operation with batteries on board and orders for a further 161, according to the Maritime Battery Forum.

Suppliers of battery technology have responded to this surge in interest with dedicated investment in the sector. Early last year Corvus – the marine battery leader, with a 32% market share (59 vessels in operation) – announced plans to open an NOK80M (US$9.3M) fully automated marine battery factory in Bergen in late 2019, with an annual production capacity of 400 MWh.

In January this year, Siemens opened its own robotic factory further up the Norwegian coast in Trondheim. With capacity to produce 300 MWh of battery modules, Siemens’ factory is smaller than Corvus’ planned facility. But it is a significant investment relative to the size of the company’s existing business in the marine sector: although Siemens has acted as the battery system integrator on 33 ships in service, it has used its own modules very infrequently. The new site, which can build more than six batteries in each shift, will help it serve what it sees as a growing market in the marine and offshore sectors.

Siemens' Offshore Marine Center in Trondheim has been supplemented by a robotic battery factory

Vessels like Ampere that run solely on batteries remain in the minority. Of the battery-equipped vessels in operation and on order, 75% are hybrid. Of those, only 23% are charged by a shore connection, with the remainder taking charge only from engines. And while small coastal ferries remain the mainstay of battery uptake, their use is quickly expanding into other sectors.

“Every vessel project now begins with a discussion about the use of batteries or alternative fuels,” says DNV GL maritime systems leader and Maritime Battery Forum managing director Sondre Henningsgård. He highlights the offshore sector as one with big potential for growth, with multiple suppliers – among them Corvus and Siemens – offering containerised solutions for offshore supply vessels. Nearly 30 offshore vessels will be fitted with batteries between 2019 and 2021, according to the forum’s figures.

“Batteries could replace an auxiliary engine and be used to tackle peaks in energy demand, allowing the remaining auxiliaries to be operated at a more optimal load”

Siemens has its eye on offshore growth. Northern Drilling will introduce the first energy storage system on a semi-submersible rig when West Mira begins operations in the North Sea this year. The rig’s diesel-electric generators will be supplemented by a lithium-ion system, Siemens’ BlueVault, that is expected to cut the running time of the platform’s diesel engines by an estimated 42%. That will cut CO2 emissions by 15% and NOx emissions by 12%. The solution consists of four converter and battery systems with a total maximum power of 6 MW.

Siemens head of offshore solutions Bjørn Einar Brath says: “Offshore rigs have highly variable power consumption for drilling and dynamic positioning. By incorporating energy storage, it is possible to reduce the runtime of diesel engines and keep them operating on an optimised combustion level. This ultimately leads to lower emissions.”

Hybrid gas carriers

The shuttle tanker Aurora Spirit is among the first vessels in its sector to deploy batteries for propulsion

Other sectors are also beginning to take note. Earlier this year the first of Teekay Offshore’s unusual hybrid shuttle tankers was delivered by Samsung Heavy Industries (SHI). The tanker, one of four on order with a further two options, features dual-fuelled LNG propulsion by engines that are also capable of burning volatile organic compounds (VOC) given off by the vessel’s cargo. Batteries are also installed, meaning that Wärtsilä auxiliary engines can burn VOCs as they are emitted and store the energy to use with the vessel’s diesel-electric propulsion.

As a result of that project, Wärtsilä and SHI have formed a partnership to explore the use of batteries on further tankers and – for the first time – in the gas carrier segment. The project will aim to optimise the capital and operational costs of these vessel types while expanding the use of efficient, hybrid solutions.

SHI is also interested in entering the marine market with its own batteries – sister company Samsung SDI is a big producer of lithium-ion batteries and is growing its business in energy storage. Samsung will be able to use Wärtsilä’s hybrid centre in Trieste – a facility that enables the full-scale testing of hybrid propulsion arrangements – to explore the best battery properties and specifications for marine use.

“We are witnessing early indicators of long-term disruption in the marine industry, with dirty diesel engines being substituted by zero-emission fuel cell systems”

Wärtsilä sales director, merchant segment Stein Thorsager says: “They see the advantage of using batteries as part of the energy demand on board and strongly believe this will be of value for other tankers and gas carriers.”

Gas carrier propulsion is usually provided by two-stroke engines, with medium-speed engines catering for on-board power demand including re-liquefaction and cargo loading. Batteries could replace an auxiliary engine and be used to tackle peaks in energy demand, allowing the remaining auxiliaries to be operated at a more optimal load. This would reduce fuel consumption as well as cutting maintenance on the remaining engines.

Mr Thorsager notes that some LNG carriers already deploy electric propulsion. These arrangements make it easy to consider adding batteries to the set-up.

“We believe in electric propulsion for some of the smaller LNG carriers,” he says. “We already see interest in such concepts from shipowners and charterers who are looking at all options to reduce their emissions to meet IMO targets.”

Batteries can offer significant fuel economies – the Teekay shuttle tankers anticipate using 22% less fuel than similar vessels as a result of their ability to burn VOC and store energy in batteries. But the extent to which batteries can help shipping to meet its greenhouse gas emission targets depends heavily on how the electricity is generated in the first place. Electricity from diesel engines will not allow ships to eliminate carbon emissions. And while electricity from shore power would eliminate shipboard emissions, current battery technology can only provide enough charge for relatively short journeys.

“Batteries alone do not solve the problem,” agrees Mr Henningsgård. “But they will enable the solution.”

Fuel cells to the fore

Fuel cells are gaining traction as a potential solution for decarbonisation. Fuel cells do not store energy but convert it to electricity from an external fuel source (often hydrogen), as opposed to batteries which store and then discharge electricity. Investment in these technologies – and the number of projects aiming to deploy them in the marine arena – has advanced rapidly in the first few months of 2019.

Mirroring the move by battery makers Corvus and Siemens, in March fuel-cell company Ballard Power Systems announced plans to open a factory dedicated to the production and repair of marine fuel cells. Ballard’s Marine Centre of Excellence will open in Hobro in Denmark this year, with an annual production capacity of more than 15 MW.

“We are witnessing early indicators of long-term disruption in the marine industry, with dirty diesel engines being substituted by zero-emission fuel-cell systems,” says Ballard Europe president and CEO Jesper Themsen. Given the pace of progress this year, his belief is understandable.

Although not yet applied in the marine sector, fuel-cell technology is relatively well understood. There have been several large marine research projects in recent years and investigations are turning to how fuel cells can best be operated and integrated. One of the partnerships exploring this topic is GE Power Conversion and fuel-cell company Nedstack, which has designed a multi-megawatt hydrogen power plant for passenger vessels.

Crucial to this design – which uses proton-exchange membrane cells fuelled with hydrogen and produces electricity, water and heat with no exhaust gasses – is electric control. Variable-speed electric drives will be used to optimise the control of the fuel cells and distribute the electricity generated. Turning fuel cells on and off frequently reduces their life expectancy and can be limited by using electric drives and a power management system. This will allow fuel cells to reach the required five-year drydock intervals.

As with batteries, Norway is proving to be a driving force in the early marine uptake of fuel cells. Two projects for fuel-cell-powered commercial vessels received funding under the Pilot-E initiative. Organised by Norway’s Research Council, Innovation Norway and Enova, Pilot-E supports several environmental projects each year. Of the six to receive funding in the latest round, two are in the commercial marine sector and feature hydrogen fuel cells.

“Turning fuel cells on and off frequently reduces their life expectancy and can be limited by using electric drives and a power management system, allowing the fuel cells to reach the required five-year drydock intervals”

Multimodal operator Samskip is leading a project to develop two containerships for short-sea routes between Oslo, Poland and the western coast of Sweden. The ships will be entirely electric and will be powered by hydrogen fuel cells.

The Seashuttle project team includes technology supplier Kongsberg, hydrogen specialist Hyon and Massterly, the autonomous vessel solutions joint venture between Kongsberg Maritime and Wilhelmsen. The grant follows €6M (US$6.8M) already received from the Norwegian government.

Meanwhile Norwegian shipyard and marine technology group Havyard has been granted Nkr104.3M (US$12.0M) to develop a ‘high-capacity hydrogen energy system’. It will be installed on one of four cruise ferries being built for new Norwegian coastal operator Havila Kystruten. The system, combined with batteries, will enable the ship to sail without emissions for five times longer than other planned or existing vessels. It will be installed and in operation by the end of 2022.

Working in unison

The mention of batteries and fuel cells working side-by-side in the Havila Kystruten system is important. For any but the smallest marine fuel-cell application, energy storage is an essential part of the power system. If power produced by fuel cells cannot be used immediately, it must be stored. For some advanced fuel-cell designs that must be turned on constantly, batteries are essential for taking the excess charge.

One of Havila Kystruten's cruise ferries will feature a hybrid fuel-cell-battery combination

A project by researchers at the École Polytechnique Fédérale de Lausanne (EPFL) has proposed a hybrid power system centred on solid oxide fuel cells (SOFC) running at a constant load. Batteries would store any excess electricity generated when electricity demand is lower than the SOFC output, while syngas produced by the cells would be processed to hydrogen that could fuel auxiliary proton exchange membrane (PEM) fuel cells at peak power demand.

SOFCs developed by EPFL have achieved 75% efficiency, compared to just over 50% for the most efficient engines, but can take 20 hours to reach full capacity. They can be used to produce a combination of electricity, hydrogen-rich synthesis gas, and high-temperature heat. This heat would be used in a purifying process – consisting of a two-stage water-gas shift reactor and a pressure swing absorption unit – to generate hydrogen. The only by-products would be CO2 and water.

EPFL researcher Francesco Baldi explains that the hybrid power system would suit cruise ships because of their diverse power demands, compared to the mainly propulsive power needed for merchant vessels. SOFCs can run on a wide variety of gas and liquid fuels, while PEMs use hydrogen fuel, which would require vast storage space onboard if used as the main power source.

While solid oxide fuel cells may be a more distant prospect, other projects are exploring the combination of ‘traditional’ PEM cells with batteries. One is being conducted by Norwegian shipyard Fiskestrand, which is exploring how hydrogen fuel cells and batteries can be used on a short ferry route from next year.

The shipyard’s HYBRIDship project is considering the optimum engineroom layout for fuel cells as well as how they can be integrated with other systems. The aim is to ensure that propulsion (including fuel cells) is robust enough for repetitive, short-burst service.

The SINTEF Ocean laboratory in Trondheim and ABB will assess how fuel cells and batteries can best function together for short-distance ferry operations. The tests will simulate the conditions that a ferry is expected to encounter on a high-frequency, 10-km route.

Fuel cells need batteries – or at least some form of energy storage – to be truly effective in helping to decarbonise shipping. And, surprisingly, there could be more barriers to uptake for relatively mature batteries than for the fledgling fuel-cell technology. Chief among them are cost and energy density.

On Hurtigruten’s battery-assisted cruise ships, Roald Amundsen and Fridtjof Nansen, the installed 1.35-MWh systems occupy just a fraction of the battery rooms designed to accommodate installations of up to 6.5 MWh. When those installations are complete they are expected to weigh around 80 tonnes. That is nearly half the total weight of the four Rolls-Royce B33:45 engines which cater for the majority of the vessels’ power needs.

It is not hard to see why big battery packs have yet to find applications on more weight-sensitive vessels. And technology advances that are expected to bring battery energy density to a new level are proving painfully slowly to emerge. According to research institute BloombergNEF, solid-state batteries – the next great hope in scaling down battery technology – are not expected to have a 'meaningful impact' on the electric vehicle market until the late 2020s. For the more conservative and challenging marine market, it could be much later.

Even more than batteries though, it is answers to the hydrogen challenge that will determine the success of fuel cells in shipping. The difficulty of storing hydrogen in large volumes is well known. Even in its most compact, liquefied form, hydrogen takes up twice the space of LNG. For vessels taking long voyages between bunkering, this is a key issue. Storage concerns could be overcome only with major changes to vessel design. Adapting bunkering schedules would not be a possibility unless the availability of commercial liquefaction plants, in Europe in particular, is dramatically improved.

But there is a more fundamental issue than storage. Fuel cells can only cut greenhouse gas emissions from well-to-wake if they use clean fuel. There are technologies emerging which could supply renewable hydrogen. Large scale electrolysis plants have been designed for onshore use which would deliver many hundreds of tonnes per day. Hydrogen could also be produced cleanly by combining natural gas steam reforming with carbon capture and storage. And a recent breakthrough by Stanford University researchers could make seawater electrolysis effective at greater volumes.

None of these solutions will be available at commercial scale imminently. The question therefore remains whether renewable sources of hydrogen can be scaled up rapidly enough to contribute to shipping’s relatively urgent need for decarbonisation.

Fuel cells will play a role in the decarbonisation of shipping. But the size and timing of that role will be decided largely by progress in the fields of batteries and renewable hydrogen.