Solar boat around the world

September 2010 a Swiss electrical engineer left Monaco to travel around the world for the first time ever with a solar boat. Last week he completed his journey.

It took Raphael Domjan an impressive 584 days to travel 30,000 nautical miles around the world. According to the electrical engineer he didn’t make the trip to get into the Guiness Book of Records, instead he wanted to do something about climate change and show what one can achieve with solar power. Plantsolar is a 31 meter long boat, costing 15 million euros to build.

Tom van Terwisga, professor of Ship Propulsion and Resistance, isn’t surprised Domjan pulled it off: “A solar boat can harvest a lot of sunlight, because there is no shade at sea.”

Planetsolar is made of composites. A good choice, according to Prof. Van Terwisga. “Composites are lightweight and solid,” he explains. “The boat has to be lightweight because that will make it go faster. It was also smart to build Planetsolar as a catamaran, as this creates the possibility to have a big surface area, where one could place the solar panels. It also makes the boat stable.”

Planetsolar used black solar cells. “Standard solar cells are blue, because our eyes see the blue light that is being reflected of the panels. It shows that the panels do not absorb all of the sunlight. Planetsolar has black solar cells, which means that they take up all the sunlight. Nothing is reflected. That makes them very efficient,” says professor of Photovoltaic Materials, Miro Zeman, who is also developing black solar cells.

In good weather the boat could produce up to 600 kWh per hour. “That’s impressive,” says Prof. Zeman, “especially if you know that a family uses less than 10 kWh per hour a day on average.”

The technology to create a boat that could travel around the world is not new. Why has it taken such a long time before someone made the trip? “I think it was particularly a financial challenge,” says mechanical engineering student, Erik Jansen, who works on the Delta Lloyd Solar Boat that will participate in a race for solar boats in the province of Friesland in July.

Planetsolar has given solar boats great PR. “By travelling around the world, their team has shown how reliable solar energy is,” Jansen says. “Planetsolar proves that one could use solar cells to travel.”

Prof. Van Terwisga believes that more boats will use solar panels in the near future: “But not all are suitable to be powered by them. Cargo ships for example will be too heavy. But for lightweight luxury yachts I think solar cells are promising. They could also very well be used as an extra power source on cruise ships. Years ago TU Delft alumni built a speedboat powered by solar energy. Unfortunately, they went bankrupt, but they showed that the concept worked and were ahead of their time.”

Jansen thinks it is interesting to look into hybrid ships: “At night the boat uses the sail. During the day the solar cells collect energy to power the motor. Besides, when it is sunny, there usually isn’t a lot of wind. It could be interesting to build such a boat.” And it could have made the Planetsolar’s journey easier, as the team had to sail close to the equator and change their routes according to sunlight forecast in order to catch as much sun as possible.

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