When was the last time you pulled back the throttles to save fuel? Yeah, that’s what we thought. Cruising slowly to burn less sounds great — right up until you try it. Once you discover that the entire world is a no-wake zone, boating gets boring. Yet just as surely as the sun sets in the west, we boaters still love to pretend we’re green. We put oil-absorbing socks in the bilge, switch to phosphorus-free boat wash and keep that Y-valve cinched down tight. If we really want to clean up our act, of course, we need to burn fewer dead dinosaurs.
The automotive industry has made progress, thanks to hybrid technologies. And there are hybrid boat propulsion systems, such as those made by Steyr. But they are not yet widely available in production boats. That doesn’t have to stop you from taking advantage of electric power, free, from the glowing ball in the sky. Who says you can’t install some batteries, wire in a solar panel and use an electric outboard to transform any boat into a hybrid vessel? No one — so we tried it for you to see how it would work.
Many solar options have been proved effective on concept boats, which can run on 100 percent sun power. Perhaps the most well known is Planet Solar, a 102-foot long-distance cruiser covered in 5,780 square feet of solar panels that is currently circumnavigating the globe. In full sunlight, these create electricity equal to 127 hp and propel Planet Solar at speeds up to 10 knots. Hold on to your hat.
The mere existence of the boat may prove its point, but it also highlights some major-league problems with sun power. Firstly, it cost $26 million to build. Secondly, it isn’t exactly fast, especially when you compare its projected 32-month circumnavigation with the world record of 48 days, seven hours — set by a sailboat, for gosh sakes. Thirdly, Planet Solar was designed for a very specific purpose and won’t serve any other functions very well. You’re not going to use this boat, or one like it, for day cruising, running to the fishing grounds or tubing and water skiing.
Unfortunately, all three of these problems can carry over into the recreational realm. Solar-powered boats are usually expensive, limited in use and relatively slow. But in a few cases, solar still makes sense. Small electric launches in the 16- to 18-foot range, like those made by Duffy or ElectraCraft, have full canopies (read: plenty of surface area for solar panel mounting) and are used purely for shuttling people around at speeds of 5 or 6 knots. Solar gets the job done, and in this service, the savings on fuel costs pan out.
In virtually all other cases, hybridization makes a lot more sense than cruising purely on the sun’s rays. Since you have to go slowly some of the time anyway, why not make that time as environmentally friendly as possible? Use the sun to supplement when appropriate, and run internal combustion engines when you want it.
Very few boats are built specifically as hybrids, but one, the Greenline Hybrid 33, can cruise at up to 6 knots on electric power with six 1.3 kW panels in the hardtop and a lithium-ion battery array, or at up to 15 knots using a 150 hp diesel. Another real-world hybrid application that’s already in use is the harbor master’s boat in Annapolis, Maryland. The city’s patrol boat was retrofitted with solar panels on the hardtop and a Steyr diesel-electric hybrid engine last fall. It makes 5 knots without burning a drop of fuel, and since it spends most of its time in a no-wake zone, the boat’s running costs have been cut by about 50 percent. This “floating meter maid” runs about 1,500 hours a year, and significant savings are expected.
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.”
All Amped Up
When it’s all done, what is the result? We clamped my 24-volt Minn Kota Riptide 70-pound-thrust electric outboard to the transom of the 2,800-pound Glacier Bay. This draws 42 amp-hours at full throttle at 24 volts. Using this engine to maneuver while casting to shallow-water structure, my 150 amp-hour battery bank runs for as long as six hours in calm conditions where little maneuvering is required and as little as 90 minutes if it’s windy, the current’s running and I’m maneuvering a lot to hold position.
With eight amps from the panel trickling in, the rig can fish indefinitely. On top of that, I putt from the launch ramp through the mile-long no-wake zone to open water without burning a single drop of fuel. Considering how often I use this ramp, that might save 20 gallons of gas each season.
Then consider the time spent fishing: Without the electric motor, I’d use the outboard for several additional hours through the course of the day of fishing, burning at least two to three more gallons of fuel. Added bonus: The whisper-quiet electric motor is less likely to spook fish than the gasoline-powered outboards.
I also discovered some downsides. I can cruise at 2.5 mph, but that speed makes me feel like I’m watching grass grow. And while a transom-mount motor takes zero time and effort to install and is comfortable to use on smaller boats, on the 22-footer it forces me to lean out over the transom to tiller-steer. A pair of motors mounted onto the outboard’s anti-ventilation plates would make steering easier. And I get no gain from the panel when the sun isn’t shining.
Green feelings aside, battery maintenance also turns out to be a big advantage of adding solar to your boat. Since the trolling motor batteries never sit in a discharged state, their life span can be increased by a matter of years. David Taylor, owner of a Grady-White 282, became so frustrated with replacing expensive batteries that he installed a small 18-watt solar panel purely to extend his battery longevity.
“I used to go through batteries every other year or so,” he said. “I can’t plug in my boat where I store it, so they wore out pretty quickly. But after adding a small solar panel at the helm, I’ve had the last pair of batteries last five seasons.” At a total cost of $200, the system quickly paid for itself.
And there are some other advantages to having a constant solar feed: The batteries are less likely to die sooner due to a stuck bilge pump or a switch left in the “on” position; dockside electric bills can be significantly reduced as well, or eliminated altogether; and accessories can be used or left on while the boat sits at anchor, or at a mooring with no electrical service, for extended periods of time.
Hybrid For You?
Does turning your boat into a solar hybrid make sense? If you tend to cruise at low speed for long distances, use an electric motor as you fish or leave your boat unattended and unplugged for long periods of time, you just may benefit from the addition of an electric motor and solar panels. In any case, as the cost of solar goes down and the cost of petroleum products goes up, solar hybrids are bound to become more and more common — and then we’ll all be pulling back on those throttles to save fuel. Yeah, right. Just as surely as the sun will rise in the east.
Alternative Power Options
Electric outboards range from 12-pound-thrust eggbeaters to 40-pound-thrust green giants. A mix of bow, transom, lower-unit and trim-tab mounting options are available, as are dedicated inboards.
Get More Juice Online
In this article we provided a thumbnail sketch of how a simple solar-hybrid system could be added to virtually any boat. Let’s call it a “hybrid-assist” system. But hybrid boats are a vast subject — too vast, and too dependent upon the needs of individual boaters, to cover in these pages alone. If you want to convert your boat to a full-on, pure hybrid with enough torque to really cruise under electric power along with incorporating a variety of charging sources, you’ll need more information. So we created a special Web exclusive section that includes detailed articles about hybrid repowering, new battery technology and more. Charged up about solar and hybrid power? Visit boatingmag.com/hybrid.
Atlantic Towers is a longtime top fabricator serving the marine community. Atlantic’s new Hiamp Hi-Line hardtops allow you to purchase a custom-fit top for your boat complete with a pre-installed solar array. The solar panels are let in flush with the top for an integral look, to prevent the need for excess fasteners, and won’t collect dirt like surface-mount panels. They can be configured to output more than 1,000 kW of power, depending upon the size of the top. These are custom-built, so prices vary, but they start at about $13,000. atlantictowers.com
As we showed, a solar-hybrid installation can take place in your slip or driveway. You can call the pros, like those at Watts Your Plan (wattsyourplan.com) to add solar power for charging batteries and running an electric motor. You can also do it yourself.
You’ll need to be comfortable working with DC electric, have knowledge of battery charging characteristics and naturally be adept at physically installing the components. Many of those same contractors who will install a solar system for you will also sell you the components needed for the conversion. Do it yourself and you’ll save labor charges and be prepared to deal with any future troubleshooting as a bonus.