INDUSTRY FOCUS MARINE
Take an environmentally friendly journey to Scotland’s offshore islands
High efficiency drives from Danfoss have been used in the development of a hybrid diesel-electric-battery propulsion system that is enabling Scottish ferries to achieve a 33% reduction in fuel consumption
The ferry propulsion system has three diesel-driven 368kVA three-phase generator sets operating at 400V, 50Hz. These feed the vessel’s main switchboard, which also has provision for connection of a shore supply when the vessel is in port. The switchboard provides power for two VACON NXP-series
liquid-cooled variable speed drives from Danfoss
C
aledonian Maritime Assets Limited (CMAL) is the asset owner for the
ferries operated by CalMac Ferries, which provides almost all of the services to Scotland’s offshore islands. As part of its commitment to supporting Scotland’s target of achieving a 33% reduction in environmentally damaging emissions by 2020, CMAL embarked on a project to develop electric hybrid ferries. Having evaluated a number of approaches including high-efficiency diesel-mechanical and diesel-electric systems, the company concluded that an electric hybrid propulsion system would offer the greatest benefits. Essentially this comprises diesel engines
driving generator sets to produce power for electric motors that drive the vessel’s propulsion units. A key feature of the hybrid arrangement, however, is that the propulsion motors can be powered not only from the generator sets, but also from high-capacity energy storage batteries. In the CMAL vessels, these batteries are charged overnight from shore supplies while the vessels are in dock, which means that advantage can be taken of low-cost off-peak electricity. To turn this concept into reality,
CMAL worked with Ferguson Shipbuilders of Port Glasgow, ship design specialists Seatec, and electrical specialists Tec-Source. The initial contract covered the design, construction and fitting out of two ferries – the MV Hallaig, destined for
16 MAY 2018 | DESIGN SOLUTIONS
use on the Sconser-Raasay route, and the MV Lochinvar, for the Tarbert to Portavadie route.
THE TECHNOLOGY The propulsion system has three diesel-driven 368kVA three-phase generator sets operating at 400V, 50Hz. These feed the vessel’s main switchboard, which also has provision for connection of a shore supply when the vessel is in port. The switchboard provides power for two VACON NXP-series liquid-cooled variable speed drives from Danfoss, each of which controls one of the vessels’ two propulsion motors, which are rated 375kW and have an operating speed range of 0 to 615rpm. The motors drive Voith Schneider Propellers that combine propulsion and steering in one unit. For pollution-free operation of the propulsion motors, each NXP drive has a 350kWh lithium-ion battery bank connected to its DC link. There were a number of reasons that the Danfoss drives were selected for this project – they are compact, combine excellent performance with an efficiency of better than 98% and a power factor of 0.99, and offer long reliable operating lives in the toughest of shipboard environments. Before installation on the first vessel, extensive on-shore factory tests and trials were carried out which not only proved the concept but enabled potential problems to be identified and addressed at an early stage.
REDUCING FUEL USE AND EMISSIONS MV Hallaig, which was the first ferry to incorporate the new environmentally friendly hybrid drive system, accommodates 150 passengers and 23 cars or two HGVs, and has a service speed of nine knots. Against the target of a 20% reduction
in fuel usage and emissions, the vessel is actually achieving a reduction in fuel consumption of 33%. It is anticipated
that this will lead to a decrease in CO2 emissions in excess of 5,500 tonnes over the lifetime of the vessel, with a proportionately similar decrease in sulphur and nitrogen oxide emissions. Furthermore, the new drive system
incorporates a high level of redundancy, allowing the vessel to continue to operate even if one of its two drive systems fails. It can also operate even if no diesel fuel is available – it regularly provides the Sunday service between Raasay and Sconser running on battery power alone. A year later, sister ship MV Lochinvar
entered service, and this is also consistently delivering equally impressive fuel savings and performance. Following the success of these vessels,
CMAL ordered a third: the MV Catriona. This was built in Port Glasgow by Ferguson Marine Engineering and sails on the Claonaig to Lochranza crossing.
Danfoss
www.danfoss.co.uk
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44
