Azimut Magellano uses hulls designed for efficiency and speed.

All About the Green

Senior Editor Kevin Koenig set out to see if building an environmentally friendly powerboat was possible. What he found may surprise you.

Full disclosure: When I found out I was writing an article essentially trying to answer the question: “Is it possible to build a green power boat?” I asked what the word count was, and then contemplated writing “No. No. No,” eight hundred times in a row. Not to sound like the oldest 32-year-old in the world, but to me a truly green boat has always seemed like a bit of a pipe dream, or maybe just a sailboat. But then I did some digging. As it turns out—and as you might expect—there are plenty of highly varied opinions in the marine world about just how green a boat can be.

"For sure it is possible to build an environmentally friendly boat. However the market and demand is still niche right now…" —Dr. Pascal Goulpié

If my initial pessimistic opinion was at one pole on the spectrum, Dr. Pascal Goulpié’s is at the other. Goulpié is the director of PlanetSolar, the largest solar-powered boat in the world, which completed a 26-month circumnavigation in May 2012 with much fanfare. When I asked him what he thought of the premise of this article, he responded with confidence, “For sure it is possible to build an environmentally friendly boat. However the market and demand is still niche right now, mainly due to the price and a general lack of confidence in the technology’s efficiency and reliability, which is unfortunate because it works well.”

When asked for clarification, and where he thinks the technology will best fit in the leisure-boating market, Goulpié continued, “If you can imagine, larger boats use a huge demand of energy, so it might not work using only solar there. But, for smaller boats, and short voyages, yes I think a green-boat market will grow soon. For daytrips and things like diving excursions, a green boat will become a standard. But if you’re sleeping and eating onboard, there’s too much of a demand for energy than solar panels can provide on their own.”

One man who agrees with the good Dr. Goulpié, at least in part, is Reuben Trane, managing director of Island Pilot, the Florida-based builder of small to midrange cruisers. Trane built a hybrid solar-and-diesel-powered catamaran in 2008 that he named DSe Hybrid 12m. Trane believes that the boat, which remains unsold, is perfect for baby-boomer retirees who want to save on fuel by using electricity to propel them from island to island on short cruises. The key to his design, he says, is the battery. 

“We originally fitted the boat with Odyssey AGM batteries,” he says, “because lithium at the time was too expensive. But we recently replaced those with a Winston lithium battery because lithium technology has become more affordable. And the great thing about lithium is, depending on how you use it, you get 2,000 to 5,000 cycles out of it over its lifetime. So if you use your boat a lot, it’s actually cheaper than an AGM battery.”

Trane also recommends that you get as big a battery as space and budget will allow. “That way,” he says, “the solar panels can charge the battery, and depending on the size, you can find a nice cove in the Bahamas somewhere, drop the hook, and go for a week without sun.” Not ideal to spend a week in the Bahamas with no sun I suppose, but an interesting and environmentally friendly prospect nonetheless.

At the less extreme ends of the green-boating movement are some other ways to reduce your boat’s carbon footprint. Everybody I spoke to agreed that resin-infusion technology is a move towards cleaner boating, as it significantly reduces construction emissions over hand-laying techniques, and also generally produces a lighter hull. And a light hull is key for that old standby foremost in pretty much every boater’s mind: fuel efficiency. The equation there is pretty obvious: Use less carbon-based fuel, leave a smaller carbon footprint. One company that has been focusing its efforts on building greener hulls is Azimut, with its long-range cruising brand, Magellano. On the Azimut Magellano 53, for example, the dual-mode hull can cruise in displacement mode at around 10 knots using 20 to 30 percent less fuel than if she was a planing boat. However, because of underwater trickery dreamed up by hull designer Bill Dixon, the boat is also capable of semi-displacement speeds approaching 20 knots, a key feature that lets owners have the option of going fast, while also being able to do the majority of their cruising a lot more cleanly.

Greenline is also doing interesting things in this area. That company’s boats, which range between 33 and 70 feet, use hybdrid electrical/diesel propulsion, are resin infused, and also have “super-displacement” hulls, which are rounded and deep enough that the shafts are at an angle less than one degree, making them extremely efficient.

Of course, not everybody is as keen on green powerboating as Azimut Magellano, Greenline, Island Pilot, and PlanetSolar. David Gerr is the director of the Westlawn Institute of Marine Technology, a school for yacht designers, and when speaking to him, you get the distinct impression that, at the moment, he thinks the green-boating movement is a load of donkey crap.

“What everybody means, I think, when they talk about green boating is hybrid electric/diesel-powered engines,” he says. “Those are well intentioned, but they make no sense for boats.” One of Gerr’s main beefs is with the inefficiencies in electric motors. “With a diesel,” he explains, “the prop uses 96 or 97 percent of the power coming from the engines. With electric, you go from chemical, to electric, to mechanical energy, and you lose some things there. The best you’ll see is about 87 to 88 percent, and a lot of times it’s lower. Every time you change energy form there’s a loss, that’s due to entropy. It’s a law. There is no escaping it.” Gerr begrudgingly allows that PlanetSolar was a success, but doesn’t think the design is practical because it has “solar cells plastered across every inch of space.”

I pressed on with Gerr, and asked him if he thinks a green boat isn’t possible at all. “Well,” he responded with a snort of laughter, “if you really want to make a green boat there is one way.” I waited for the punch line, but none came. “You could make it longer and slenderer and drive it slower than its theoretical hull speed. If you were to come to me and say you wanted a green boat, I’d go with a diesel or gasoline engine, and stretch a 50-footer to a 65-footer so it’s got the same displacement, and run it slow, and it could be as much as 30 or 40 percent more efficient as far as miles per gallon.” He paused. “But that’s not sexy so nobody ever does it.”

After all these interviews and research, can I say for sure that Gerr or Goulpié, or anybody in between, has the definitive right answer to my question? No, I cannot. What I can say is that it certainly seems possible—not to mention worthwhile—to make power boats greener, and for now, that’s a step in the right direction.

This article originally appeared in the January 2014 issue of Power & Motoryacht magazine.