Costs for solar panel systems have been dropping at a blistering pace in the last few years and are being widely used as a clean alternative to fossil fuels. Solar panels work great for homes and RVs, and some car companies are trying to get it to work there, too, but what about boats? Can solar power be a feasible resource to power yachts, boats and ferries?
Fossil fuels are still the mainstream choice to produce electricity around the globe, and many people assume the reason for that is simple economics: fossil fuels are cheaper. But in the past few years that’s changed. Coal power plants, which supply 37% of the world’s electricity, had a levelized cost of energy (LCOE) of $109/MWh in 2019. In the same year, the solar panel LCOE reached $40/MWh, whereas 10 years earlier it had been rated at $359/MWhn – meaning an 89% decrease within a decade. 1
This decrease is directly related to the price drop of solar modules, which declined from $106/W in 1976 to an incredible $0.38/W in 2019, a 99.6% reduction during that period. That’s led to a widespread adoption of solar panels for applications like residential, commercial, grid-scale, automotive, and even maritime.
In 2019 in the U.S., ships and boats released 40.4 million metric tons of CO2 into the atmosphere, and although ships have the biggest share, this doesn’t mean that smaller boats aren’t off the hook. While wind and biofuels are being explored to lower carbon emissions from ships, as I looked at in a recent video, solar PV have also been considered to power boats, ferries, and yachts. 2
Although electric boats sounds like modern or future technology, the first electric boat dates back to the 19th century. Moritz von Jacobi, a Prussian inventor, developed an early electric motor in May 1834, which was then improved and installed in a 28-foot paddle boat. The boat carrying 14 passengers made its first trip in 1838, crossing the Neva River, in Russia, and it was the first documented launch of an electric boat. It was powered by 180kg of zinc batteries and was able to travel at a speed of about 2.5 km/h.3 4
At that time, batteries were heavy, large, and not rechargeable, making the commercial production of electric boats a non-starter. The development of recharging technologies like the lead-acid in 1859 and the dry cell battery using zinc, manganese, and ammonium chloride in 1866, triggered improvements in motor technology. Combined with batteries, the invention of outboard motors by William Woodnut Griscom of Philadelphia in 1879 enabled the commercial production of electric boats, and the first one set sail about three years later. The battery powered, 7.6 meter long boat could sail for six hours at an average speed of 13 km/h.
After that, several electric boats were launched and the technology started to become more popular. But with the arrival of internal combustion engines in the 1920s, electric boats, like electric cars, were left to drift out to sea. 3
Between October 1973 and February 1974, oil prices rose 400%, while the price of solar panels dropped to $100/W in 1975. In that year, Alan Freeman of Rugby England put together the world’s first solar-powered boat. It was a 2.5-meter catamaran equipped with 10 solar modules, each comprising 5 cells connected in series to give rather modest … 1.3W. 5
In the 1990s, solar boat championships started to be organized and about three decades later, the first boat using only solar power from 48 panels crossed the Atlantic ocean between 2006 and 2007. The boat could run for 20 hours with a full charge and reach a top speed of 11 km/h (7 mph). 6
Global policies to fight climate change opened the door to the development of improved solar-powered boats, but before we sail ahead into the latest technologies, let’s take a look at the basic principle of electric propulsion.
In a solar-powered boat, the solar panels generate energy that’s stored in batteries. This energy is controlled by a charge controller, which ensures that the solar panel achieves peak performance. A motor controller is used to convert the DC current from the batteries into AC, in addition to controlling speed and torque. Finally, a prop-shaft or drive unit is coupled to the motor’s axis in order to propel the boat. 7 8 9 10
There are also hybrid technologies where a generator is used to recharge the batteries, like a diesel generator installed in parallel to the electric motor in order to extend range for emergencies. It’s very similar to hybrid cars. However, these alternatives aren’t as green as solar-powered boats. 10
Fully electric boats offer several advantages compared to traditional boats that use combustion engines. They’re silent, clean, demand very little maintenance, have regeneration capacity, and are lightweight – an electric propulsion system is about 30% lighter than a diesel system, mainly because diesel engines are larger and heavier than electric motors. Also, it’s estimated that electric boats have less than 1/20th of the maintenance costs of a diesel engine in the first 10 years. There’s no diesel, oil to change, filters, etc. (you get the idea). On top of that, the fire hazard of storing gasoline or diesel on the boat is significantly higher than storing batteries. 9 11
However, like everything in the technology world, solar-powered boats also have downsides. First, they have a pretty limited range compared to gasoline/diesel-powered boats. That’s because petrol has about 100x the energy density of a lithium-ion battery, so an electric boat would need a volume of batteries much larger to provide the same range as a conventional diesel/gasoline engine … increasing the boat’s weight.
Regarding costs, although lithium-ion battery prices have dropped considerably in the last few years, the upfront costs of a gas outboard engine over an electric one is lower. But this is where solar energy enters the picture, in order to boost range by recharging the batteries and reducing the total costs of ownership in the long term. 12 13
Aiming to harness solar in marine power, some companies around the world have been developing interesting solutions. And some of those, like luxury yachts, are a great example of what’s possible. Granted, luxury yachts have an outsized demand on resources and high costs when you consider that they’ll be used by a small number of people. On the flip side, you have something like a ferry that can shuttle thousands of people around, which is a more equitable use of resources. But similar to high-end cars, luxury yachts start at a high price due to their innovative concepts. As those concepts become more affordable to manufacture, they’ll make their way into lower-end, more mainstream models.
The Spanish company SILENT-YACHT has been producing several models of solar-powered yachts. Its 18-meter long SILENT 60 is equipped with a 17kW solar array that’s used to power the propulsion system, which is available in three models. The options range from 2 x 50kW motors and 143 kWh of batteries to 2 x 340 kW motors and 286 kWh of batteries. It has a cruising speed of 6-8 knots and can reach a top speed of 13-20 knots, depending on the propulsion system. But get ready for some sticker shock, the price starts at €2.4 million, or about $2.78 million.14
In case you’re not up on luxury yacht prices, just to give you a comparison, an equivalent diesel-powered yacht, the HELIOTROPE 65 with a length of 19.8 meters, goes for $1.98 million. 15
SILENT-YACHT also has a larger model available, the SILENT 80, that has 26 kW of solar power installed. At a cruising speed of 6-7 knots, the catamaran run quietly for about 100 nautical miles per day without fuel, and with virtually unlimited range as the solar array recharges the batteries. In addition, SILENT’s yachts are equipped with a diesel generator for backup. The starting price is about €5.4 million, or about $6.26 million. 16 17 18 Again for comparison, a similar fossil fueled model, the OCHO UNO built by Fairline, is currently for sale for a modest $1.95 million.19
Regarding operating and maintaining conventional diesel-powered yachts, a report by Towergate Insurance, a UK-based broker, shows that owners need to spend at least 10% of what they paid for the yacht every year. So, a $2 million yacht costs at least $200,000 to be maintained and operated. While diesel currently costs $0.96 per liter in the U.S., solar panels recharge the batteries for free, and if electricity is needed to recharge the batteries, the current cost of electricity in the U.S. is about $0.10 per kWh – and in some ports around the globe, using charging stations is free. On top of that, an electric drivetrain has only a few moving parts in comparison to the hundreds of moving components of an internal combustion engine, making the maintenance cost much lower.20 21 22 23 24
Moving beyond the luxury yachts, the Singapore-based company Azura Marine is making boats, ferries, and plastic collectors.25 Ferries are a very common transportation method in India, and Azura sells three models that differ in passenger capacity, length, and power capacity. The larger model, the E-FERRY 45, can accommodate from 35 to 50 passengers, the overall length is 12.5 meters, and the ferry is powered by a set of two motors rated at 20kW and a battery bank of 60 kWh. The max speed is 9-10 knots, but when cruising at 4 knots it’s range is unlimited.26 27
To get into some detailed benefits, we can look at another company working on solar ferries, Navalt, which produced India’s 1st solar ferry. ADITYA is a 20m long catamaran ferry that can accommodate 75 passengers and is powered with two 20kW motors that consume the power generated by the 20kW PV array. In 4 years, this ferry has saved 130,000 liters of diesel and avoided 330 tons of CO2. The cost of ADITYA is ₹1.95 Cr, equivalent to $260,894. A diesel ferry with similar features would cost around ₹1.5 Cr ($200,687).
When it comes to maintenance, an equivalent diesel-powered boat would require oil and filters as well as engine overhaul charges. An analysis made by Navalt showed that a diesel sibling of the ADITYA consumed ₹2,102,429 ($28,235) in fuel in the first year while the ADITYA consumed ₹62,235 ($835) in grid electricity. The maintenance cost of running the diesel ferry for one year every day was ₹210,243 ($2,823). In contrast, the solar ferry has zero maintenance costs until the batteries need to be replaced (about seven years since the ADITYA started its operation). The replacement cost of the batteries cells is expected to be ₹2,500,000 ($33,573) at the current price. The total cost of ownership (TCO) of the ADITYA in a 20 year cycle works out to ₹27,440,000 ($368,497). On the other hand, the TCO for its diesel sibling is ₹91,470,000 ($1,228,369), about three times higher. 28 29
With material cost reductions and incentives for the electrification of boats, the solar ferry and yacht market has a lot of room for growth in the next few years. Luxury options, like yachts, for example, are still unaffordable for most people, and we can see a higher upfront cost compared to their diesel siblings. But when we analyze solar ferry boats, as the ADITYA, solar and battery powered boats turn out to be great in terms of cost and benefits, considering that they’ll transport hundreds or thousands of people every day. But even though the cost of solar panels and batteries are dropping, there’s still a long way to go towards mainstream adoption in the marine environment.
- Why did renewables become so cheap so fast?↩
- Greenhouse gas emissions from ships and boats in the United States from 1990 to 2019↩
- Electric Boats↩↩
- Electric Boat↩
- TBThursday 1975: The world’s 1st Solarboat↩
- TRANSATLANTIC SUN 2↩
- Lithium-ion vs. lead acid batteries overview↩
- The Technology of Electric Boats↩
- Market barriers towards electric boats↩↩
- ELECTRIC PROPULSION EXPERTS↩↩
- Electric Propulsion↩
- Electric vs. Burners on the water – are electric boat engines worthwhile?↩
- Electric vs. Gas Outboard Motors: Which Is Better?↩
- SILENT 60↩
- HELIOTROPE 65 Yacht for Sale↩
- Silent 80↩
- SILENT 60 – Royal Yacht International↩
- Silent Yachts introduces Silent 80 Tri-Deck – the most spacious solar electric catamaran ever↩
- OCHO UNO Yacht↩
- The hidden costs of owning a superyacht↩
- # HOW MUCH DOES IT (REALLY) COST TO OWN A YACHT?↩
- Learn More about the Science behind Electric Boating↩
- USA Diesel prices, 01-Nov-2021↩
- Average retail electricity prices in the United States from 1990 to 2020↩
- Aquanima 45↩
- Aquanima E-FERRY 45↩
- Ferry Lifecycle Cost Model for Federal Land Management Agencies↩
- Introduction to India’s First Solar Ferry↩
- Economics of ADITYA – India’s First Solar Ferry↩