An array of flexible, foldable solar panels enables extended cruising even when it rains.
Issue 148: Jan/Feb 2023
Some people are motivated by the lure of wealth, fame, and power. I’m motivated by beer and milk. After a long week of work, I want cold beer waiting for me onboard the boat on Friday evenings. Similarly, my wife, Alex, wants cold milk at the ready for her Saturday morning coffee.
Sadly, for the last several years, the boat lived on a mooring and we didn’t have the battery power to leave the fridge on 24/7. Instead, we hauled warming beer, tepid milk, and melting ice out to the boat for every weekend outing.
On longer summer cruises, we resorted to running our diesel engine frequently for battery charging, a habit we hated because of the noise, exhaust, fuel consumption, and wear on the engine. A wind generator might have helped, but the incessant whining noise those things produce ruled them out for us. Instead, we decided to invest in a solar power solution that has worked remarkably well on Sundance, our 36-foot Morris Justine that we are sailing in New England waters.
Two of the solar panels are installed on the bimini.
We liked the idea of taking the solar panels down for winter storage and for storms during the sailing season. We also wanted to avoid the traditional, obtrusive panels for performance and aesthetic reasons. So instead of a big arch with bulky, rigid panels over the transom, we sought something slimmer and lighter. Semi-permanent, flexible panels have a lot to recommend them. Unfortunately, most of the flexible panels I found didn’t look to be well made and didn’t have good options for securing to the boat. The reviews I read confirmed my suspicions.
At the Miami International Boat Show a few years ago, we finally found the panels we wanted. Built by SunWare in Germany and imported by Starboard Sun in Getzville, New York, the model we settled on is a high-quality, flexible, and foldable panel with a perimeter of sturdy grommets mounted in canvas. It also comes with a handy bag for transport and storage.
Our goal on Sundance was to turn the DC-powered boat fridge on in May and leave it on, powered exclusively by solar, until October while the boat lived on her mooring. By trial and error, we learned that at least 300 watts of power were required to accomplish this goal reliably in all weather conditions. Two years ago, we increased our array to 500 watts for additional power.
Supercharged Solar
Each of the five panels has its own charge controller.
Our batteries now stay topped up while we are living on the boat for extended cruising, even on gray and rainy days. On sunny days, we can make coffee with our induction kettle in the morning, run our sailing electronics and autopilot all day, make 50 gallons of water with our DC watermaker, make ice for cocktails, and still go to bed with the batteries near 100%—without ever running the engine! On cloudy days, we need to be more energy conservation-minded. We revert back from induction to propane cooking and shut the lights out a little earlier if it’s raining all day.
Our solar array consists of five identical 100-watt SunWare model RX22052 foldable panels. (These same panels are now rated at 120 watts, thanks to improved technology.) On deck, there are five identical plugs and the panels are all interchangeable. If one of the panels, plugs, or controllers failed, the other four panels would continue with their work.
We can set up our five panels in under 10 minutes and take them down just as fast. We stow them in a cockpit locker and/or under berth cushions in the cabin when not in use. These panels are durable enough to walk on when in position on deck and to sit on when stowed under a berth cushion.
Alex holds the panels in their handy storage bag.
A single panel lying on the foredeck under white shrinkwrap plastic does a surprisingly good job keeping the batteries topped up all winter. We have learned to reinstall that panel on deck after the shrink-wrap plastic cover has been put on for the season.
For a house on land, it’s easy to calculate the optimal angle for solar panel orientation. On our squirmy boats at sea, the geometry gets a little trickier. No matter how you set them up, at least one panel remains in the shade of the sails, radar, or mast—or, quite possibly, pointing away from the sun altogether. This inherent inefficiency on a moving boat is inescapable. The goal is to minimize the loss.
On Sundance, our standard solar configuration consists of 200 watts atop the bimini, 100 watts on the foredeck, and 200 watts draped over the lifelines in a weather-cloth style configuration. The 15-foot cord on each panel allows for some adjustment to that configuration. Chasing the sun, we have at times set the panels up atop the dodger and mainsail cover, or on deck just forward of the mast, an element of flexibility that would be impossible with a fixed, rigid panel.
Angling for Power
A panel on the foredeck doubles as a dog bed.
The tropics aren’t the only place for solar. The longer days in the mid-latitudes during sailing season compensate for the lower midday sun angle in these waters. The mid-latitude boat also consumes less power than she would in the tropics. Her fridge runs easy thanks to the cooler seawater, and her lights burn judiciously thanks to the shorter nights. Lower power consumption means less work for the panels.
But to maximize power generation in the mid-latitudes, we must adjust our solar panel orientation to accommodate the relatively low sun angles found here. Choosing a lifeline-draped mounting approach for some panels helps diversify the sun angles the total array is exposed to. On Sundance, we’ve found our vertically mounted lifeline-draped panels to be an excellent complement to our horizontally mounted panels on the bimini and foredeck. When heeling under sail, the lifeline-draped panels often catch the sun squarely, and I have been amazed to see them frequently outperforming our horizontally mounted panels. On the mooring, or at anchor, the lifeline-draped panels catch the early and late sun. In doing so, they lengthen day and shorten night, an excellent feature for any solar system.
Lifeline-draped panels help catch the sun when
the boat is heeled.
The solar panels on Sundance work together to charge our 300 amp hour lithium house bank. Each panel is controlled by its own Victron Energy SmartSolar charge controller. Each controller recognizes how much sun its assigned panel is currently soaking in and optimizes the output accordingly. This way, the panels in the sun won’t compromise the performance of the panels in the shade, and vice versa. The fi ve controllers are networked to deliver the house battery bank what it needs, depending on its state of charge. All of this can be monitored via Bluetooth to a display on a phone and/or tablet, something we pay close attention to when onboard.
Wiring the panels is simple enough. A pair of wires goes from the plug to its controller. Another pair goes from the controller to the battery—and that’s it. The tricky part is picking the spots on deck to install the plugs. Ideally, they should be located close to their designated panel and clear from the boat’s gear and crew, while still providing for manageable wire runs below deck to the controllers. A clean solution I found for my bimini top panels was to install plugs on the underside of a backstay- mounted antenna farm just above the bimini. With this arrangement, the plugs are completely out of sight and the solar wires sister up with all the antenna wires in tidy fashion. Aside from this one replicable trick, plug locations will vary from deck to deck.
In recent years we’ve replaced hard blocks and shackles with Dyneema soft blocks and shackles all over the boat. High-quality, flexible, lashable, stowable solar panels outperform rigid solar panels for all the same reasons: flexibility and simplicity of installation, plus light weight and low bulk.
Five identical plugs on deck make the panels
interchangeable.
A few years back, the designer of our boat, Chuck Paine, stopped by for a visit on short notice. My top priority in the hour before he arrived was to strike the solar panels (and sell the paddleboard) to get the boat looking sharp. Solar power is great, but solar panels do detract from the aesthetic of the boat. I love having the option to stow them when the boat needs to look her best.
Our approach minimizes the intrusive nature of the solar panel both cosmetically and functionally, but it doesn’t solve the problem completely. I look forward to a time when components of the boat, like the stack pack, decking, dodger, or paddleboard are built completely of solar panels.
In such a boat, solar power generation would be a part of the design and build of the boat and the solar panels would maintain the shape of their original function. Solar power that is truly built in instead of tacked on is the ultimate fix.
Christopher Birch is cruising full-time with his wife, Alex, and dog, Bill, aboard their 1991, 36- foot Morris Justine, Sundance. You can follow their voyage at EagleSevenSailing.com.
Thank you to Sailrite Enterprises, Inc., for providing free access to back issues of Good Old Boat through intellectual property rights. Sailrite.com
