Case histories
We spoke to four owners of production boats who now have electric-only installations. These are still mostly found on fast, lightweight modern designs suited to hydro-regeneration, but improved electric saildrives are encouraging quick conversions
CASE 1: POGO 30 ZEPHYR
As leader of marine innovation for Raymarine, Mark Johnson was well placed to convert his 30ft yacht to a full electric set-up. Power comes from a pair of Torqeedo 48-5000 (48VDC-10kWh) lithium batteries recharged by 1kW of Solbian flexible solar panels. The motor is a 4kW (5.3hp) Torqeedo 4 pod, which can also harvest power when sailing.
The ‘sweet spot’ for propulsion is 1.5kW which provides 4.5 knots. When sailing fast (seven knots) for three hours, the pod regenerates around 600Wh. The solar array on the boom can be placed horizontally to catch more rays and also act as a sunshade. Energy is also captured by reflection from the water. Mark’s Raymarine Axiom MFD (MultiFunction Display) has been configured to accurately represent the ebb and flow of power. He has used Zephyr extensively for family holidays, including several Channel crossings, with the display allowing him to plan ‘energy strategies’ depending on the weather. When asked if he is happy with his electric propulsion, Mark replied: “There’s no noise or smell; no vibration; it weighs much less than a diesel; and power is instantly available. But I think the single biggest benefit is the space saving because without that you’d really need a 36ft boat for family cruising.”
The use of electric propulsion has allowed Mark to use the engine space for the liferaft, with the diesel tank area now a hanging locker. By removing the diesel engine, Mark saved just over 200kg (440lb) in weight and £750 a season in fuel and servicing costs.
Price comparison
The set-up aboard Zephyr is more than double the price of a diesel, but servicing and running costs are over 90% cheaper.
CASE 2: 10M SUSTAINABLE YACHT YA
Conceived in 2010 and designed by naval architect Dick Koopmans, the Dutch-built Ya completed a global circumnavigation between 2016-2018. The mission was to prove that an entirely electric yacht was both practical and enjoyable for blue water cruising. The sail plan is for a yawl, while electric propulsion comes from a pair of e-Tech 7.5kW (10hp) shaft drive inboards. Two small Brunton Ecostar propellers optimise the thrust. Power is generated from an array of solar panels and a masthead-mounted wind turbine.
The boat uses no fossil fuels at all, even for cooking, and has a draught of just 70cm (2.5ft) allowing access to almost anywhere, including shallow inland waterways. She is also designed to sail fast, with 130m2 of sail area when the gennaker is flown. She only has three berths, a deliberate move to keep the interior as spacious and comfortable as possible. The full-length windows are a design feature to make her feel more spacious still. The careful generation and management of renewable power allows Ya to have an induction cooker, microwave, oven, freezer, fridge and two watermaker systems. There is also inverter power of 230V and ‘USB outlets everywhere.’ Ya is described by her enthusiastic owners as ‘an energy-neutral demo yacht for everybody who wants to sail sustainably’. You can try her for yourself and book a paying berth on her via the youth sailing website: windseeker.org or via the yacht’s own (mostly Dutch language) site at duurzaamjacht.nl
CASE 3: SALONA 46
Graham Balch of Green Yachts commissioned the Croatian-built Salona 46 with twin electric motors and describes the result as ‘amazing’. The lithium battery bank packs 30kW and powers twin 10kW (13.4hp) Oceanvolt Servoprop electric saildrive units. The yacht sails fast, recording 10 knots on a beam reach in 15-20 knots of breeze. This allows for very effective hydro-regeneration from the twin servo-props, whose blades have been optimised for this purpose. “Manoeuvring in a marina was easy, with no need to use the wheel,” Graham said. “When sailing, we can hydro-regenerate twice as fast. The Salona 46 is such a quick boat, even in quite light winds, so it’s ideal for electric motors.” The boat can make its maximum of 8.5 knots under power for three hours.
CASE 4: SALTRAM 24 E-VOYAGER
Three Plymouth-based companies, two local universities and a host of OEMs have come together to convert an old workboat into an all-electric ‘test bed’ passenger ferry. Voyager Marine took the hull of the 1980’s-built Saltram 24 Mermaid and stripped it out, replacing the elderly 50hp Ford diesel with a modern (and massively overpowered) 140kW (187hp) Avid electric motor provided by EV Parts UK. The overpowering was deliberate in order to get MCA type approval for the engine and controls, which would then be used in commercial vessels of up to 24m.
The battery is a stripped-down and re-purposed 400VDC automotive version from two written-off low-mileage
Nissan Leafs, with the lithium-ion cells pared down to 22kWh. The e-Voyager will become the UK’s first seagoing all-electric passenger vessel on her route across Plymouth Sound, with recharging available from three 22kWh chargers installed at key locations along the route. A full charge can be achieved in three hours (usually done overnight) with shorter ‘top ups’ taken between regular passenger runs.
Larger projects are already underway based on the e-Voyager test data.