The options for having an electric boat or a hybrid-electric boat are growing in popularity; we outline the current options for those making the switch
A modern electric boat can come in all shapes and sizes, from the latest high-tech speed boats with recently developed high-performance electric engines, to a traditional tender with an electric outboard on the back. Increasingly yachts are going electric too as electric engines become increasingly capable of propelling boats weighing several tonnes, and with the rigging for sails, at a reasonable speed for an acceptable length of time.
Since the invention of the marinised engine, there has never been the capacity to store enough fuel to cover significant distances in boats that are smaller than a tanker, with fuel capacity always being the limiting factor. As such the best way to cover long distances on a boat fit for a small number of passengers was, and remains, wind power.
For all the many green attributes that using the power of wind offers, there is no escaping that for most, fossil fuels still represent some part of sailing – whether that be a diesel engine to motor in light winds, onto and off a mooring, or to generate power for onboard electronic systems. Even a small tender used to go from ship-to-shore is often fitted with an outboard motor.
Recent advances in electric power, however, have started to make electric propulsion a reasonable alternative to fossil fuel power. Range will always be an issue but that has long been true of a traditional diesel engine. Improvements in lithuim-ion battery performance is, and likely will continue to, increase range every year.
Additionally electric power and batteries offer the bonus of being able to be recharged via solar panels, a wind turbine or hydroelectric power – via a hydrogenerator mounted on the stern of a boat sailing.
At first glance the electric yacht market could appear in its infancy, but like every revolution, the will of the people is driving forward technology that only a few years ago was seen as the stuff of fantasy.
The market has responded to demand, and battery and motor technology has come on leaps and bounds, driven in part by the rapid development of electric cars.
It may not be commonplace yet, but electric yachting is here, even available ‘off the shelf’, so is it time to get onboard?
A cutting edge electric boat
Like Formula One, it’s the cutting edge of electric yachting that trickles down into mainstream production in no time at all.
For Spirit Yachts, a builder defined by a unique blend of traditional and state-of-the-art, electric yachting has been driven by demanding clients that want their yachts to be at the cutting edge.
Spirit Yachts have now produced a number of projects aimed at the all electric luxury yacht market including the Spirit 44e electric boat and a recent project, the Spirit 111, had all the hallmarks of a superyacht project and the team had to earn their keep delivering to brief.
Managing Director Nigel Stuart explained how it works.
‘The 111 combines several cutting-edge technologies to deliver a something that’s never really been done before. A lithium-ion powered electric drive system can be charged by hydrogenation and also two high-wattage diesel generators.
‘Each generator is 22kw, meaning they can pack a lot of power into the system in a short period of time, they don’t need to run for long to fully recharge.
‘The prop is both a means of drive and power generation, so no separate hydrogenerator is needed. She will be capable of motoring under electric alone for more than 30 miles.
‘When you take on a project that’s electric, it makes you think hard about efficiency so the air conditioning, water heaters and everything in the galley has also been carefully selected to use less power.
‘For her owner there is very little compromise and some major advantages.’
Whilst it’s a long way from the average cruising yacht, the trickle-down effect of projects like the Spirit 111 can’t be underestimated.
Traditional boats go electric
Less well known is the yard’s interest in electric auxiliary engines, something they have been involved in for more than 10 years.
Their first project, the refit of a Contessa 32 called Calypso, was an experiment by the Rogers family to see what was possible.
‘Calypso was a test bed in the technology’s infancy,’ explains Kit Rogers of this early electric boat.
‘Inevitably, we didn’t get it all right, but we learned a lot about the dos and don’ts of electric yachting. The end result was a hybrid. The more we did, the more interesting the project became.
‘It’s not just the obvious, silent peaceful propulsion; it’s also the things you take for granted about a cruising boat. For example, no gas, we didn’t need it because we had electric power.
The yard has also worked on an electric folkboat conversion for a foreign customer.
‘The client, first and foremost, loves to sail. He sees the electric as an auxiliary option, along with the rowing and is excited to own a boat that’s quietly different.
‘He’s looking for a more connected experience and an electric boat helps him achieve it. When you’ve been motoring in and out of marinas under chugging diesel engines for years, the electric motor is something of a revelation.
Off-the-shelf electric boat
Perhaps the biggest indication of the future of the electric boat is the willingness of production and semi-production builders to pin their flags to the mast and embrace it.
One of the first was Hanse, who developed a version of their 315 utilising a Torquedo electric pod system.
Providing around the same amount of power as a 10 horsepower diesel, a 4.4kWh lithium ion battery pack powers the system.
Arcona, Dufour, Elan and Delphia also have electric boat models and are each taking their own direction on entering the market.
Arcona’s 380Z (the ‘Z’ stands for ‘zero emission’) fully electric boat has solar panel covered sails, capitalising on the large surface area to top up batteries under sail.
In the multihull market, there is even more scope for solar, wind and hydrogenation due to the horizontal surface area available for solar charging.
What are the options for an electric boat?
Purely electric systems can be broadly divided into two categories, high and low voltage.
The latter is the simplest option in terms of how it works and requires less specialist knowledge to install.
Kit Rogers installed a 48v Ocean Volt system in his latest project and remarked on the experience.
‘The advantage of the low voltage system is its inherent lack of complexity. Whilst we’ve coupled it with lithium ion battery technology, it can also be wired up to conventional lead acid batteries. There are pros and cons to both. What surprises everyone is the size, it’s a tiny motor and is surrounded by lots of space where the engine would normally sit.’
High voltage systems are more advanced, and utilising lithium-ion technology, their capacity is improving year on year.
For larger yachts this is generally seen as a better option.
A partnership between BMW and Torqueedo has led to the development of the Deep Blue 315v high voltage battery.
Effectively the same unit as found in the BMWi3 electric cars now often seen on the high street, the system produces a lot of power and is being used on the Spirit 111 project as well as catamarans.
One big barrier to entry exists for most potential electric yacht buyers – range.
Even the most advanced set-ups are limited to a maximum of a few hours motoring at cruising speed.
‘The electric motors excel at two things in particular,’ explained Kit Rogers.
‘The first is as auxiliary power for getting in and out of marinas. The second is engaged at low power to very efficiently motor-sail in light airs. If you want to do more than that, at present, you need to add a way of packing in the charge into the battery quickly whilst at sea; which means a generator’ .
As with electric cars and as enthusiasm builds for the technology, a hybrid option, pairing a generator with an electric drive system, is already proving popular and is probably the most practical option for those planning to cruise any distance.
Using a large generator, charge can be quickly put into the system when needed.
Once under sail, the yacht’s propeller becomes a hydro generator, meaning that diesel power is not needed day-to-day.
Solar can also be used to add additional charging capacity.
‘When a fully integrated electric hybrid system is incorporated into a cruising yacht from the outset, its possibilities really become clear,’ explains John Arnold, UK manager at Torqeedo.
‘Sailing for days on end with no engine noise is entirely possible. There are other less obvious benefits too. Electric drives have no long rotating shaft, so can be used as pod drives as well, meaning the boat is far more manoeuvrable than even a yacht equipped with bow and stern thrusters.’
How much does it cost to convert a boat to electric power?
The technology exists, but anyone seriously considering going electric will want to crunch the numbers.
In the case of taking out a traditional inboard diesel and replacing it with an electric system, it’s relatively easy to work this out.
However, unless you include an auxiliary generator, you will be limited to battery range alone.
For this reason, we’ve done a like for like comparison for a 35ft yacht engine refit, including the cost of a generator to make the system a practical hybrid.
Unsurprisingly, at the moment, there’s a big difference in cost, but at between three to six times the cost, it is gradually coming into the realms of possibility, and prices should continue to drop as technology develops and evolves.
Ocean Volt SD10 Motor system (including batteries, charger and 6kw generator): £30,825.16
Beta Marine Beta 20hp Marine Diesel: £4,100
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