A hybrid power management system on Transport for London’s (TfL) two new £20M (US$25.7M) hybrid electric Woolwich ferries has been a major factor behind problems that plagued the vessels following their launch
TfL London Rail director John Fox told the annual Interferry conference in late October that “Despite lots of effort and focus, performance has suffered with a disappointing start to service in January (2019) and a significant number of asset failures.
The hybrid power management system has, among other asset issues, been particularly problematic and year-on-year volume has gone down, despite it being a free ferry.”
According to Mr Fox’s figures, a year-over-year comparison showed that traffic volumes on the ferry service have dropped by around 30%. The troubled pair of vessels replaced a set of three older vessels in January 2019 and were intended to reduce noise and emissions and improve reliability on vehicle and pedestrian transfers across the River Thames between North and South Woolwich in southeast London.
The shipyard that won the contract to build the ferries, Remontowa shipyard in Poland, gave Passenger Ship Technology more detail about some of the teething problems the vessels have experienced.
As Remontowa Shipbuilding director of commerce Michal Jaguszewski explained, “The new Woolwich ferries have indeed experienced some issues connected mainly with the functioning of the power management system. As a result, the system required adjusting which is a common situation as far as hybrid solutions are considered.”
Mr Jaguszewski said a resolution has been reached regarding the power management system’s problems.
“A special technical team consisting of the owner’s, the operator’s, the yard’s and the electric system integrator’s representatives was formed with the aim of identifying the root cause of problems and coming up with solutions. This task was completed successfully and currently both vessels are operating untroubled,” he said.
Both TfL and London Mayor Sadiq Khan have publicly apologised for the delays and inconveniences created by problems with the vessels.
“We’re sorry for the issues that Londoners using the Woolwich Ferry have faced this year – it isn’t acceptable,” TfL’s general manager of sponsored services Danny Price said. “A taskforce of engineers has been created to resolve the power issues the hybrid engines have experienced. The Woolwich Ferry is an important part of London’s transport and we take its operations very seriously – that’s why we’ve invested in new vessels with much cleaner environmental standards and increased capacity.”
TfL representative Danny Keillor told Passenger Ship Technology that the service faced additional issues with the vessels’ docking system.
The ferries use an automatic magnetic mooring system developed by Mampaey Offshore Industries.The automated mooring system – in which a large magnet is clamped on to the side of the ferry to save energy – is a relative newcomer to ferry operations. Typically, the systems are used in harbours with larger, ocean-going cargo ships.
The TfL vessels’ need for quick turnaround times pose another potential problem for the mooring system. According to Mr Fox’s presentation at the Interferry conference, the service’s target is six crossings per vessel, per hour, adding up to some 25,000 mooring operations per terminal, per year. The site of the ferry crossing on the River Thames sees a tidal range of up to 7.6 m and a tidal current up to 5 m/sec as well as a considerable amount of passing river traffic. All of these factors, in addition to a need for precision in the alignment to linkspans whose tolerance is +/- 150 mm, create additional levels of complexity for the services efficient running.
Mr Fox listed lessons he said had been learned from TfL’s experience with the Woolwich ferry, including public expectation being set against the city’s most efficient public transit service – the London Underground, also managed by TfL; that urban environments are not the place to trial unproven technology; that whole-system risk integration needs to be clear and incentivised; that there is a need to use suppliers throughout the supply chain who understand your needs and culture; and that contingencies should be in place to ensure asset utilisation is not assumed to be 100%.
The vessels’ battery diesel-hybrid solution is intended to extend the life of the diesel engine, allowing the engines to run at a constant low load with the batteries taking dynamic loads in a process known as peak shaving. The advantages of using batteries for peak shaving on the ferries are that they allow the diesel engines to reach optimal efficiency with the lowest specific fuel consumption.
The equipment package per vessel consists of battery packages provided by Corvus, two diesel generators by Cummins and four thrusters by Hydromaster.
Norwegian Electric Systems (NES) provided the two hybrid electric systems for the new ferries. The NES package consists of ultralight converters forming a DC-grid system with four battery packages, two on each side of the DC-bus for redundancy.