Hybrid solutions for small ferries help put marine public transportation on the road to electromobility

Today’s charging infrastructure cannot adequately support a switch to complete electromobility. In addition, marine electric vessels cannot yet travel long distances. However, the technological shift toward electromobility is already happening, with diesel-electric hybrid ferries being an important stepping-stone in this process. This article describes Volvo Penta’s work with hybrid solutions for small ferries in Sweden and Norway, and how these solutions facilitate the switch to full-scale electromobility.

A diesel-electric hybrid ferry, equipped with gensets powered by Volvo Penta engines

The Tellus ferry operates the 1,8 kilometer-wide waterway Gullmarsleden, across Sweden’s greatest fjord on the country’s west coast. It is a busy maritime route, with little room for delays let alone unplanned stops.

Tellus is a major diesel-electric hybrid ferry, equipped with gensets powered by four Volvo Penta D16 MH engines. Most of the time, the ferry will only use one of them for its trips across the fjord. The other engines are used when required, such as during tough weather conditions or if there is a lot of sea ice. The engines drive synchronous reluctance-assisted permanent magnet (SRPM) technology generators; units that can be driven individually or parallelly in order to optimize fuel consumption and emissions.

Electric batteries that allow for charging via both a charging station and the ferry engines

Tellus also has two electrically driven POD propulsion units, one at either end of the ferry. As such, it does not have to turn when going back and forth across the fjord. The energy for the propulsion units comes either from the batteries or from the Volvo Penta D16 MH engines. An onshore charging station charges the ferry’s twelve Corvus battery-racks (total capacity of 949 kWh) at night. However, they can also be charged by the Volvo Penta D16 MH engines while in operation. Tellus can currently complete three trips in full electric mode before the gensets need to take over.

Long charging times, along with insufficient battery capacity and heavy battery weight, are some factors that have previously limited these kinds of commercially viable, heavy-duty electric solutions. In recent years however, innovation and development have had a significant impact on the capacity of many battery-powered vehicles and vessels. Volvo Penta is one of very few manufacturers making DC gensets that can charge batteries directly, and that can also power DC motors in diesel-electric systems with no batteries.

Hybrid solutions for small ferries Fjordled ferry

Hybrid ferries provide smooth, silent public transportation in Norwegian archipelago

In Rogaland in southwestern Norway, hybrid ferries Fjordled and Fjordøy operate the route between Haugesund and islands Røvær and Feøy. Fjordland was the first hybrid ferry operating in Norway.

Fjordled and Fjordøy are powered by two Volvo Penta D13 MH engines each, producing 441 kW at 1,900 rpm. The vessels also have two electric motors – producing 85 kW at 2,100 rpm – mounted directly on the gears. The battery pack consists of three strings with a total of 140 kWh capacity (110 kWh is usable capacity). The large battery capacity allows for an uninterrupted power supply to the electric and electronic systems onboard. Thus, there is no need for any standard generators to provide electric energy.

The Fjordled ferry is capable of doing 11 knots in battery mode, though harbor steaming only requires 6-7 knots. During harbor steaming, which makes up about 30% of the ferry’s operation, the use of electro-propulsion results in a lower load profile on the engines, which in turn leads to less maintenance. In addition, the ferry is almost silent when running in battery mode.

Selective catalytic reduction provides exhaust aftertreatment, reducing ferry emissions

The Norwegian hybrid ferries are equipped with selective catalytic reduction (SCR) exhaust aftertreatment systems certified for IMO Tier III regulations. Overall, Fjordled and Fjordøy emit 80% less NOx than the ferries that previously operated the Haugesund-Røvær-Feøy route.

All Volvo Penta engines accept HVO, and the combination of SCR technology and HVO fuel means both NOx and CO₂ emissions can be significantly reduced.

Facilitating hybrid solutions and electromobility in the marine and industrial sectors

While the sufficient charging infrastructure is still lacking, these kinds of hybrid ferries are a significant step toward full-scale electromobility. They combine high cruising speeds, achieved by diesel engines, with emission-free battery power close to shore. Volvo Penta is dedicated to facilitating marine hybrid solutions, and developing solutions that enable electromobility in the marine and industrial sectors.

A key driver in this work is to support our customers in future-proofing their businesses. We collaborate with them, assess the best options, and run pilot projects to determine the direction of future product development.

If you liked this article, you may also want to read the article on how our gensets reduced fuel costs and emissions for the Teistin ferry in the Faroe Islands. You can also read more about how we move toward electromobility together with our customers, IMO Tier III and NOx emissions, connectivity, and many other subjects here on the Volvo Penta Professional Power Blog.

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