What’s the future of efficient, lower-cost propulsion on your boat?
The answer, according to author and marine systems expert Nigel Calder, may lie in part with that trusty old diesel engine you’ve already got.
Calder, who sat down with Three Sheets Northwest during the recent Seattle Boat Show, has spent several decades working to improve energy efficiency on boats. And he’s come to the conclusion that the solution rests on a hybrid system that uses diesel propulsion wisely.
“When it comes to propulsion, it’s hard to beat a diesel engine,” Calder says. “There are other reasons for using hybrids, but fuel efficiency is not one of them.”
And fuel efficiency isn’t the primary factor in making boats run as efficiently as possible, Calder says – engine run time is. The ideal system for boats, he says, is a “parallel hybrid” that uses a regular diesel engine for high energy loads and switches to a small electric motor for low loads. By contrast, a “serial” hybrid requires both an internal combustion engine and a separate electric propulsion system, making it considerably more costly.
The parallel hybrid system uses a smaller electric motor for lower engine loads – for example, when maneuvering at slow speeds in a marina — and a standard diesel engine for higher loads (i.e., while underway at full speed). When the diesel engine is running, the electric motor becomes a generator, adding enough load on the engine to keep it at peak performance while charging the boat’s batteries.
This approach effectively consolidates the total engine hours into much shorter run times by using the boat’s batteries as a big energy sink. It also reduces the amortization costs of an engine, Calder says, something most recreational boaters rarely think about.
“If an engine costs $20,000 to install and you only get 5,000 hours out of it, which would be pretty good for a sailboat engine, it’s costing you four dollars an hour to run it – before you put any fuel in it,” Calder says. “But if I can consolidate five hours of engine run time into one, I’ve got $20 of amortization costs saved, even though I might not save any fuel. And in that time I’ve probably only burned two or three dollars of fuel anyway.”
A parallel hybrid system depends on being able to rapidly soak up energy and store it, requiring the use of either lithium or thin plate pure lead batteries. The systems are still relatively new to the marine industry. Austrian company Steyr Motors introduced a parallel hybrid propulsion system for boats in 2008, and the technology is being used in some European canal boats, Calder says.
The control systems needed to deploy parallel hybrid technology in the North American boating market haven’t yet been fully developed, Calder says. But when they are, he believes that parallel hybrid systems will become increasingly common in boats. The electric motors they use double as generators, he points out, but cost less and are easier to install than stand-alone generators.
“You can effectively have a generator as well as electric propulsion,” Calder says. “It’s not a bad deal. And I think that’s where the market is. Right now, the market is definitely in retrofits and not in new boats.”
In 2009, Calder, along with a Brit named Ken Wittamore, launched the Hybrid Marine (HYMAR) project, a three-year initiative focused on refining marine systems that was financed by a $3-million grant from the European Union. The project may be extended through this summer, but Calder is ready to turn his focus elsewhere.
He delayed his retirement for the HYMAR project, but is now anxious to get out cruising with wife Terrie Frisbie-Calder. They plan to leave their home in Maine around June and head to the Mediterranean. (The call of the sea is in the family – Calder’s 24-year-son Paul is restoring a Cape Dory in New Orleans and plans to head out cruising when he’s done; his blog about the project can be read here.)
“I want to go cruising,” Calder says. “It’s been a three-year interruption.”