# The long, long way round (in a Solar Taxi)

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Round the world on solar power. View gallery (7 images)

December 8, 2008 Swiss school teacher Louis Palmer last week became the first person to drive around the world on solar power. The 52,000km (32,000 mile) trip took 17-months at an average speed of 65kmh (40 mph). Mr Palmer, 36, said the car ran "like a Swiss clock," breaking down only twice during the grueling trip through 38 nations that started in Lucerne in July 2007.

The Solar Taxi is an aluminum chassis three wheeled vehicle that gets its power from a \$5,000 six square meter solar panel trailer provided by German company Q-Cells. The solar cells on the trailer produce enough electricity to run the car up to 100 km a day. Weather permitting, the trailer provides the Taxi with 700 watts (approx 1 horsepower) which on it’s own is only enough to propel the vehicle at approx 20km/h (12 mph) so the vehicle is also powered by a pair of \$15,000, 115kg (250-lb) recyclable batteries from Zebra Battery. One battery is in the trailer while the other is in the front of the “Taxi”. The batteries store energy from the sun and from whatever electrical socket Palmer can find at night. On a sunny day the Solar Taxi can travel 400kms, at night 300kms. If the trailer was left behind the Solar Taxi can travel 200kms. The entire vehicle including trailer weighs 500kg (1100lb), top speed is 90km/h and it’s power consumption is a mere 8 kw/hr per 100 km (130wh/mi)

100% solar

You might be asking how is the Solar Taxi 100% solar powered if the batteries are charged over night from the grid? For this purpose, they have a solar power plant on a rooftop in Berne, Switzerland. This electricity is fed into the grid, offsetting electricity generated by using fossil fuels. It's like paying money into a bank account and withdrawing the money somewhere else. They feed solar electricity into the grid and charge it into their battery anywhere in the world.

Salt battery

The new high-energy Zebra battery is made from common salt, ceramics and nickel and holds four times more energy like a lead acid battery for the same weight. Total battery capacity is 28Kw/hr. A ZEBRA-battery can be charged about 1,000 times - equivalent to the Solar Taxi covering a distance of 400,000 km (250,000 miles). To keep the electrolyte salt liquid, the battery requires a working temperature between 270° and 350 °C. Due to vacuum-isolation, much like that used in a thermos bottle, the exterior temperature is only 5 to 10 degrees higher than ambient and heat loss amounts to a mere 40 W. The battery can be charged on any regular 110 or 220 V power outlet and by using a quick charge it's possible to fill to 50% capacity in 30 minutes. The regular charging process takes 6 to 8 hours and the Zebra battery is 100 % recyclable.

The Solar Taxi prototype cost as much as two Ferraris to build, but would cost around 10,000 euros (\$12,620) if mass produced, with an extra 4,000 euros for solar panels

Next challenge

Mr Palmer said he now plans to return home: "I promised my mother to be back before Christmas." Next year he plans to arrange a trip with six vehicles around the world in 80 days drawing power from sources such as hydro, geothermal and wind energy.

Paul Evans

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