Decarbonisation of workboats: sort your hull first
While the delegates at February’s Commercial Marine Network ‘Workboat 2050’ webinar might not have agreed on the exact technologies, they spoke loudly and clearly on the importance of hull design.
The webinar was brought to you by The Commercial Marine Network, Seawork and Maritime Journal, in association with The Workboat Association and kindly sponsored by Spinlock and supported by SMI, UKHMA, and UKMPA.
Bruno Bouckaert of Holland’s HullVane began by making the useful analogy of reducing the carbon footprint of our homes: “We start by insulating the roof, adding double glazing, LED bulbs etc. That means when we do the big things like boilers, we get more bang for our buck. It’s the same with workboats; the hull is the equivalent to our insulation and double glazing. Before we think about hybrid or electric propulsion, we must absolutely minimise the hull drag.”
HullVane’s main solution is an underwater foil situated below and behind the transom that provides lift and forward drive, and in tests has cut diesel burn by up to 27%. It looks at cutting the wavemaking component of hull drag, by dramatically reducing the vessel’s stern wave, which wastes large amounts of fuel to create. With some very persuasive before and after pictures, Bruno explained how the harbour patrol boat RPA8 had not only saved its operators (and the planet) 57,000 litres of diesel and 150 tons of CO2 emissions per year, but also provided a quieter working environment for those aboard. The technology is well suited to vessels with a low Froude number.
Dr. Nere G. Skomedal, co-founder of Norwegian Surface Effect Ship specialist ESNA, had a different solution, and also needed to start by explaining his company’s interesting technology. Surface Effect Ships are otherwise known as sidewall hovercraft. Usually catamarans in general arrangement, they push pressurised air into the space between the hulls. A flexible finger skirt at the bow, and a flexible airbag at the stern create enough of a seal to stop the air immediately escaping, allowing the pressure to build and the craft to rise considerably in the water. This riding on a cushion of air is claimed to improve the seakeeping of the vessel, as well as saving fuel due to the reductions to skin friction and wavemaking drag.
Unlike a traditional hovercraft they use conventional water propulsion, and consequently are not, of course amphibious. A delegate raised the valid question of how much fuel you need for the lift engine. Nere was able to report that only 5-15% of the overall vessel power was used for lift, but much less was needed for propulsion with the SES system so the overall fuel burnt was significantly less. Clever electronics allow three modes to be selected on the bridge to actively control the air chamber pressure, and hence the degree of damping, especially useful for managing crew transfers.
ESNA are working on a battery vessel with diesel as backup only, using their SES technology. The sums suggest that it will be able to perform 12-hour trips in full zero-emission electric mode.
THROWING AWAY THE MOULDS
In terms of throwing away the moulds of traditional commercial craft design, our first two speakers had set a high bar. But Simon Schofield, CTO at BAR Technologies was able to show two of the most dramatic looking CTV/ WTW designs we’d seen. The BARTech 30 and 50, for a start, are proas (long thin monohull, with smaller stabiliser hull to one side). When you throw into the mix, actively controlled foils, that use AI to ‘learn’ the seastate and predict what they’ve got coming to them, and super fine hulls that are claimed to cut up to 1000 tonnes of CO2 per year, it made for an interesting presentation.
The company is a spin out from Ben Ainslie’s America’s Cup team, which uses lots of ex Formula1 talent and techniques. Lightweighting is clearly a part of this, with plenty of use of composites, but Simon was able to show how this reduces the push-on power required at the windfarm towers, so an added benefit over the sea keeping and fuel burn improvements.
BAR is developing a fully electric version with diesel range extender. The range under electric power alone is predicted to be 50nm at 20 knots.
The speakers then proceeded into a rich panel discussion, ably compered, as always, by Andy Page of Chartwell Marine, who as a naval architect was clearly in his element with these three diverse solutions to pressing problems.
Don’t miss: Session 4 on Thursday 6th May at 10:00. Medium term 2025 onwards: Vessel design & technologies for the future - Focus on Propulsion systems: Hybrid Battery & Electric & SCR
Also Session 5 Live at Seawork 2021: Long term 2035 onwards: The future fuel race – battery, hydrogen, ammonia etc. - How do we go about commissioning a vessel in this changing environment?
View the YouTube video of the presentation’s edited highlights by clicking here
By Jake Frith
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