Hybrids for All
This is all good stuff to know if you’re interested in solar and you’re buying a new boat, or if you’re running a fleet of pig-slow workboats. But, can solar power be used effectively to hybridize the kinds of boats most of us own? You bet. In fact, retrofitting recreational boats with solar power has become something of a cottage industry. Outfits like Watts Your Plan in Maryland offer custom-designed solar systems, and others like e Marine Systems in Florida distribute DIY kits for solar installations. “They’re popular on trawlers,” explained e Marine sales manager Bob Everhard, “because solar kits like these allow them to run without a generator, or to leave food in the fridge without it spoiling when the boat’s somewhere you can’t plug in.”
Just what can be accomplished with a retrofit, and just how cost-effective is it? To find out we had Mark Jenkins, the owner of Watts Your Plan (wattsyourplan.com, 301-606-5402), bring his mobile solar workshop to our test platform, a 22-foot Glacier Bay. The mission: Turn this twin-engine outboard catamaran into a hybrid.
“The system is based on charging the batteries,” Jenkins said, “and then the batteries can be used to run almost everything electrical on board with an inverter, or to run an electric motor for propulsion. Yet, batteries have a finite limit as to how much power you can put into them, and how much you can get out. So stretching capacity is a big concern. Most everyone is interested in the cost-benefit analysis. You could approximately double your amp-hours with AGM batteries, for example, but they cost three times as much as standard flooded-cell batteries. And the cost for marine lithium-ion batteries is astronomical.”
Keeping it simple, we stuck with the pair of 75 amp-hour, 12-volt, deep-cycle flooded-cell batteries already on board. These were wired in series to produce a single 24-volt, 150 amp-hour battery bank. More batteries, better batteries or bigger batteries would have increased our range. The bank we had would suffice for this experiment.
As soon as we started looking at solar panel options, we discovered that the T-top didn’t provide as much room as Jenkins would have liked. It would hold a single 4-foot-11-inch by 2-foot-2-inch, 135-watt rigid panel, weighing about 30 pounds, and that produces eight amps of current, only half the output of his average installation.
Jenkins said the toughest part of any hybridization is mounting those rigid panels. Although flexible solar panels are available, they’re not as cost-effective. Rigid panels often use crystal silicon as a semiconductor; when sunlight hits the semiconductor it kicks electrons loose and allows them to flow, creating an electrical current. Flexible panels frequently use cadmium telluride or amorphous silicon coatings. These are only about half as efficient as rigid panels, often have shorter life spans and cost more. Luckily, conforming to unusual surfaces isn’t usually a problem, even with rigid panels.
“Mounting the panels on a curved T-top frame really isn’t tough,” Jenkins said, “as long as there’s an aluminum framework I can drill through.”
With the panel installed, we routed the wiring down the T-top pipes and into the chase under the cockpit sole. In the battery compartment we mounted a “solar controller” about the size of a deck of cards, which dictates the rate of charge and prevents overcharging the batteries. Two power leads run from the solar controller to the batteries; a battery monitor can be added if you like, and the job’s done. Total installation took but a few hours, and Jenkins said installing a 270-watt system with two 135-watt panels rarely takes more than a day of work and costs “between $2,000 and $3,000.”