Electric and hybrid boats

As hybrid gas/electric cars such as Tesla and Prius has grown in popularity and become more practical options for mainstream consumers, boat manufacturers have begun to follow suit.

Experienced boaters tend to have an appreciation for the natural aquatic environment and eco-system around them. From following the tides to co-existing with wildlife, being eco-conscious is deeply-ingrained in the boating lifestyle. New technologically-advanced boat models are now making hybrid gas/electric propulsion not only feasible but enjoyable.


How does a hybrid electric boat work?

A hybrid marine propulsion system is any combination of a combustion engine and an electric motor. Electricity can be produced by one or a combination of the following: a combustion engine generator, a wind generator, a towed water generator or solar panels. A purely electric solution with solar panels is enviable due to its zero carbon footprint and low operating costs and various takes on these systems have been gaining traction on alternative energy vessels. Advances in both energy storage and solar panel technology have reduced costs and physical footprint making solar power propulsion systems more feasible for use on boats.

There are numerous benefits to electric motor propulsion including that it’s quieter, more efficient at lower speeds and less smelly. It’s also expected to lower overall costs of ownership by reducing or eliminating the needs for oil and transmission fluid changes, filter and impeller replacements and starter problems. There’s less to winterize too. Additionally, unlike diesel or gas engines, electric motors provide full torque instantly so boats get up on plane faster. Aftermarket conversions (which currently make up the lion’s share of the market) can use existing drive shafts and components so there are a cost-savings when re-powering.


Hybrid and electric boats and the current marine market.

As mentioned, now that hybrid and pure electric propulsion systems have proliferated within the automotive industry, hybrid or electric boats are beginning to gain steam. Still, the marine world is a relatively small niche market that tends to follow rather than lead other industries in terms of innovation. Currently, only less than 2 percent of boats today are integrating electric or hybrid propulsion. This slow adaption is partly due to the unique issues of boating. Boats have a different frequency and variance of use than cars and the market has many segments (ferries, sailboats, small high-speed planers, large distance cruising yachts, etc.) where boats are used differently, making it hard to build one solution to fit all applications. However, a few companies are trying to change all that.

Power and auxiliary sailboats are typically propelled by inboard or outboard engines using diesel or gasoline fuel. A growing appeal has been placed on electric motors for these purposes – i.e. pure electric engines powered by large battery banks.

As with any new technology, there’s an adoption curve. The early adopters are the technologists, visionaries, and tinkerers and they make up only about 15% of the market. In marine, these are distance sailors that need efficient sustainability and autonomy but they’re also ferries and water taxis that operate on bodies of water where combustion engines aren’t allowed. Then come the towboats, tenders and fishing boats as well as charter boats to fill the boating sweet spot of the 25-75 foot midrange power market.

What are the problems with marine hybrid and electric boating?

Because e-propulsion is in its infancy in the marine market, available solutions are few and they’re expensive. So far, most electric boats have been slow and small and had very restricted range but that is changing. There’s also the problem of infrastructure, which is the same for automotive: What is the range of these new vessels and where do they recharge? Just like a Tesla that you’d probably not take on a cross-country road trip, a boat may need charging stations close together to “fuel” quickly.

The technology behind electric and hybrid boating, the uses of brushless permanent magnet electric motors and advances in lithium-ion battery technology have allowed for leaps to be made in the rush to marine electric. Lithium-ion batteries are half as heavy as lead-acid batteries and last three times as long, and advances in their effectiveness and stability have been significant.

German electric motor manufacturer, Torqeedo, teamed with BMW and “marinized” the automaker’s i3 and i8 Series batteries for use in a variety of boats. They added a rugged damping frame to minimize shock, a venting system to channel gasses safely and waterproofing to IP67 standard. The new batteries have a 31% increase in capacity (energy density) over the previous similarly sized model and their footprint (roughly 5’ x 3’ x 6”) can be fitted into even the most compact engine spaces.

Serial and Parallel Hybrid Boats.

Currently, two approaches are battling it out on the water – serial and parallel hybrids. The serial hybrid system integrates a range-extending generator. The engine drives the generator, which powers an electric motor connected to the driveshaft—there is no mechanical connection between the engine and the driveshaft. A parallel system has a direct mechanical connection between the engine and the driveshaft but also drives an additional electric motor that operates as a generator – on the same shaft.

Range-extending power regeneration may be accomplished by a free-spinning propeller, which is easy to do on a moving sailboat and can be accomplished by using only one engine at a time on a powerboat. UK motor manufacturer, Hybrid Marine, is offering a third option: a multimode system that combines the best of serial and parallel approaches with an arrangement of clutches and gears.

Cutting-edge Concept Designs in Solar Boating.

Fully-electric boats are making great progress but they’re still a small portion of the boating market. However, highly promoted concept designs are helping raise awareness of alternative energy solutions and one such advocate is Touranor SolarPlanet, a 102-foot catamaran with wave-piercing hulls. The futuristic Swiss SolarPlanet cost 15 million Euros when it was launched in 2010 and circumnavigated the globe in 585 days strictly on electric power generated by the 500 solar panels on her top deck. Although the design’s top speed was 14 knots, the average speed around the globe was 5 knots.

After that impressive feat, the boat was donated for research. Boats like this may be one-offs but they’re helping shine the spotlight on what can be accomplished in alternative energy propulsion and the direction that boating is taking.

Fuel Efficiency in Hybrid Boat Engines.

In a hybrid solution, there’s still a need for some form of the combustion engine (for primary propulsion or as a generator). Increasingly, traditional diesel engine manufacturers have focused on improving the fuel efficiency of their engines in both inboard and outboard applications and they’ve become an ideal partner in hybrid approaches.

Volvo Penta just introduced their D4 and D6 diesel engines that have been reconfigured for a smaller size (for weight savings), lower emissions (for the environment) and better economy (for fuel-sipping efficiency). Meanwhile, outboard manufacturers like Evinrude and Yamaha have been building larger engines with more torque but better mileage. It seems the whole world is trying to ease up on their carbon footprint even if they don’t eliminate it altogether.

Hybrid Solutions for Sailboats.

Large sailboats are under auxiliary power often, especially when docking, anchoring or heading out on long windless passages. Distance cruising sailboats have pioneered solar power solutions for onboard energy needs for hotel loads such as refrigeration, A/C and lighting. However, propulsion has been a challenge. In 2010, production catamaran builder Lagoon experimented with a diesel-electric design but there were challenges, primarily due to insufficient energy storage (battery) capabilities at the time. Lagoon builds the lion’s share of sailing catamarans in the charter that are based in exotic locales where fuel is at a premium and a hybrid solution would be a game-changer for the charter industry.

Inboard motor maker, OceanVolt, powers all manner of sailboats including JBoats sailing racers, Alerion luxury daysailers, and boats that are often seen in charter like the Dufour 382 and the Voyage 480 multihull. Meanwhile, Torqeedo’s Cruise outboard series includes models with throttle control and a GPS-based battery-management system that continually reports the remaining range at variable speeds and requires only two 24-volt lithium-ion batteries. These outboards are well suited to smaller, lighter sailboats for close-quarter maneuvering and short distance motoring but powerboats have benefited as well.

On the cutting edge, upscale sailing catamaran builder Gunboat launched Moonwave that is testing a hybrid electric power plant with a diesel generator backup. With BMW i8 batteries, Moonwave uses electricity for propulsion as well as their large hotel needs, which makes it hard to stay completely electric for long stretches of time.

The future of hybrid and electric boating.

The technology may be complicated and the adoption rate may still be below 2%, but change is happening at an accelerating pace as breakthroughs in battery expertise, motor design, and lightweight hull-building materials are introduced. Fast, clean, quiet and price-effective electric, hybrid and solar boats will soon be within reach of boaters everywhere.

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