The Solar Boat that did: North to Alaska!

The voyage of the Wayward Sun documented on the Solar Sal Journey blog chronicles a pioneering trip that saw the solar-powered boat complete a successful 1,216 nautical mile journey from Bellingham, Washington, all the way to Alaska, culminating in a visit to Glacier Bay National Park. Serving as a real-world demonstration of sustainable cruising, the expedition proved the viability of 100% solar power for long-distance travel, even through the often cloudy and rainy weather of the Inside Passage, showcasing that solar-only boats can effectively eliminate “range anxiety” and depend solely on the sun for unlimited distance.

Alex and David Borton are taking a Solar Sal boat on a 1000 nm journey from Bellingham WA to Juneau AK, embarking May 23 2021. The 27-ft, 100% solar boat, built by Devlin Boat in Olympia, WA, has been named Wayward Sun and upgraded and outfitted for this journey. We added more solar panels, more electronics, and doubled battery capacity. Please note we will strictly adhere to all of the rules for a transit-through passage through Canadian waters during this pandemic. After all, we never need to stop to refuel.

People always ask us “how far can your boats go?” For 100% solar boats, this is the wrong question. But understandable, because that is how regular electric boats work. Regular electric boats are inherently limited by their battery capacity and their efficiency. They have to return to shore power to charge. Until recently, solar was not capable of severing the tie to shore power, so it was only functional for extending range, or for partial charging. But it’s now possible to produce a solar boat with reasonable speeds and accommodation that can continuously cruise without ever charging from the shore. Ever. Sustainable Energy Systems has been producing boats like this since 2012. As long as it is daylight our boats get enough energy from the sun to go, even on overcast and rainy days.

One incomplete answer to the “how far” question is that Wayward Sun will go80-100 nautical miles on a full charge – that is if we threw our solar panels overboard. But practically this number is not really relevant because we are always getting solar input. Empty batteries will charge in 2 sunny days, or overnight on shore power. Again, this is not the most important consideration because on a cruise we almost never drain the batteries all the way.

The relevant question for solar boats is “how fast can you go?” The unsurprising answer is faster when it is sunny and slower when it is cloudy. Let’s say we threw our batteries overboard. On a sunny day we collect enough power to move our boat between 4.5 and 5 knots (not considering current or wind). On an overcast day we get enough power to go between 2-3 knots, depending on the thickness of the clouds. Now if we assume both the batteries and solar panels manage to stay onboard, we can adjust our speed and daily distance to match the conditions. Indefinitely.

On any electric boat it is easy to measure the exact power the motor is producing in Watts. Wayward Sun will go 4.5 knots at 1000 Watts and 5 knots at 1500 Watts. Doubling the power from 1500 Watts to 3000 Watts will gain just over an additional knot of speed. Add another 1500 Watts gets you only get another half knot to max out our top speed of 6.5 knots at 4500 Watts of power. Of course using higher, inefficient speeds significantly reduces the time and distance you can travel. For Wayward Sun, the sweet spot is close to 5 knots.