Solar powered boats

Simon Milward became the first man to cross the channel on a boat powered purely from solar power. We chat to him about his journey.

Simon Milward

First off, why cross the channel in a solar powered boat?
Two key reasons:
1) To stir people’s imagination and try to promote the use of solar power in more situations, including in innovative ways.
2) To raise money for Oxfam.

How long did it take and how many attempts did it take?
It took 6 hours and 59 minutes. This was my first attempt to cross the channel but I had tested the boat three times before, including in Poole Harbour where I crossed to Brownsea Island and back.

Did you run into any problems?
About three quarters of the way through, in the second shipping lane, the wind and waves picked up. I was worried that the waves might swamp the motors meaning I wouldn’t be able to navigate a path between the ships. But fortunately the boat rode over the waves well and the motors kept relatively dry and were not damaged.

How did you construct the boat?
The boat (called “AKT Solar”) is made from the base of a “Dart 15” racing catamaran. This has a wooden frame fitted on top. 6 AKT Solar panels are then mounted on top and two electric motors are mounted to the transom of the frame. The panels are wired directly into the electric motors.

How do the panels power the boat?
The 6 Solar panels are connected directly to the motors. This means the motors only work during the day as the panels only produce electricity when light shines on them. The boat functions best in direct sunlight and will run slower if it is cloudy. In order to get the most power out of the panels I crossed the channel on a sunny day that was close to the longest day of the year, when the sun is at its highest and most powerful.
The wiring of the panels to the motors is a bit complicated and is done like this:
Two of the 6 Solar panels (the front right and front left) are 220 Watt, 27 Volt panels. The other 4 are 180W, 12V panels. Two 180W panels are wired in parallel to each motor to give 360W at 12V into each motor. Then the motors are also wired in series and the 2 x 220W panels are wired in parallel across the series-connected motors. This gives a further 440W across both motors at around 13V per motor.
So ultimately each motor gets about 580W at around 12V.

Do you think solar power could power larger ships in the near future?
Solar power certainly could power larger ships. However, I’m not sure how practical this would be as you’d need a large surface area for the panels, which might not work with many ships such as container or cruise ships.
Also you’d either need battery storage or a combination of electric and conventional engines, otherwise the ship would not be able to function at night.
And unfortunately battery storage is a key sticking point for many potential uses of solar power. This is because batteries tend to be expensive, bulky and typically degrade after at most a few thousand cycles. In fact, a key way to promote more uses of solar power (and electric power in general) would be to develop a safe, small, cheap and long-lasting solution to electricity storage.

Was the technology used in the boat a total success?
Yes, completely. No problems, even with the salt water, as the AKT Solar panels are fully waterproof and the motors adequately protected.
From the point of view of speed, the technology was also successful. Guinness World Records had said we needed to cross the channel in under 12 hours in order for them to recognise the record and we made it across in 6 hours and 59 minutes.

Was it just the panels or was there any other tech on the boat?
I also had a conventional compass and, stowed away in a dry bag, a phone with GPS on it recording my progress, as required by Guinness World Records. However, apart from those, there was no other technology and the set up was simple, although optimising the panels’ voltages with the motors was somewhat complicated.

Do you think harnessing solar power is key to our future of renewable energy generation?(On the water and in all industry).
I think electricity generation through solar power can be very helpful in three key areas: i) in large-scale electricity generation, feeding into electricity grids and reducing (although probably not eliminating) our need for other generation methods; ii) in small-scale electricity generation providing electricity for the billion or so people on the planet without access to a regular electricity supply; and iii) in providing power for specific new applications such as in space or closer to home in applications such as water pumping, mosquito control, electric fences, ventilation, lighting, electric aircraft etc.

However, I do not think that on its own solar electricity generation will solve all our needs. Rather its true power will be when used in conjunction with other forms of energy supply, especially if we can develop improved batteries and distribution.

Do you have plans for another expedition?
My wife says that I don’t and certainly I don’t have any well-developed plans (yet). Is it all right if I promise to let you know when I am ready for the next one?

…and anything else you’d like to add?
Please donate to Oxfam through my just giving page! www.justgiving.com/Simon-Milward2