Solar powered travel, a distant dream or viable future?

As hybrid or electric vehicles become more common place1,2,3 scientists, engineers and visionaries are turning their attention on the next challenge: fully solar powered transport.

The Solar Impulse is an impossibly graceful solar powered aircraft who’s wings span fully 63 m (about the same as an Airbus 340) but this plane only carries one pilot and travels at barely 30 km/h when taking off.

What the plane lacks in speed it more than makes up in endurance. This summer, it limited itself to crossing the US. It took off from San Francisco in May and flew past the Statue of Liberty before landing at JFK in July, traversing the country in five stages, with Piccard and the other co-founder of the project, André Borschberg, a former fighter pilot in the Swiss air force, swapping places in the cockpit. The flight was a remarkable achievement: the Solar Impulse flew further than any solar-powered aircraft before.

The plane that crossed America is a prototype, with the name HB-SIA. Its successor, the HB-SIB, will try to circumnavigate the world in 2015, using about as much power as a scooter. With no rival, it will have the skies to itself, but on land and on sea, too, a new generation of solar-powered vehicles is making extraordinary journeys, around the world and across continents. Now, though, a number of projects across the globe are pushing the boundaries of technical knowledge and coupling them to daring and demanding adventure.

The Solar Impulse’s solar cells are 135 microns thin – the same as a human hair; its motors waste only 6% of the energy they consume, compared with a typical bleed of 70%; its carbon fibre panels that form the structure of the wings and fuselage are, at 25g/m squared, three times lighter than writing paper. The new plane, the HB-SIB, can fly through night and day, clear skies and storms, at a top speed of 70km an hour. “We built the first plane with the technology of 2007,” Piccard says. “We built the second plane with the technology of 2015.”

Circumnavigation feats are not exclusively for air travel: PlanetSolar was the first around the world, in a 31-metre, space-age-looking motorboat called the MS Tûranor PlanetSolar. “There must be something in the water and in the air also,” PlanetSolar’s managing director and co-founder, Pascal Goulpié.

The amount of energy the Earth receives from the sun in one hour is enough to power the total human power consumption for a year.

PlanetSolar was founded two years after Solar Impulse – was because of advances in the commercial photovoltaic market: “It was a time when the PV industry was starting mass production, but at the same time when its market share was very small. The basic concept was to show the maturity and reliability of solar. It was to show what we can do with PV energy. The amount of energy the Earth receives from the sun in one hour is enough to power the total human power consumption for a year. The technology is here, mature and available.”

The boat began its circumnavigation in September 2010, cruising at a speed of 7.5 knots – “the idea was not to be the fastest, but the first” – and travelling under a French military escort off the coast of Sudan and Yemen. It returned to Monaco, completing the journey, in May 2012. Although the boat was slow, it was extremely efficient: it was able to travel for three days even without sun, thanks to its storage capabilities and lower power demands. And the solar technology proved completely reliable.

Sky and sea present unique challenges for solar vehicles, which require unique solutions and a lot of funding – Solar Impulse’s budget, over 10 years, is €90m; it cost €15m to build PlanetSolar. Solar cars are cheaper and offer the chance for lower cost, bottom-up innovation. Cambridge University Eco Racing has developed a solar-powered car that will race 20 other vehicles 3,000km across the Australian outback in October 2013. The team behind it comprises 60 students at the university, “without much academic input”, according to project manager, Keno Mario-Ghae, a 20-year-old engineering student at Girton College. Cuer’s budget is only £500,000, much of it donations in kind – and that’s still five times the budget of previous year’s attempts.

The car is tiny (4.5 metres long, 0.8 metres wide at its widest and 1.1 metres tall at its tallest) but has a top speed of 140km an hour. Even more impressive, Cuer went from drawing board to finished vehicle in eight months. “Everyone is trying to push the boundaries,” says Mario-Ghae. “If you do things the way they’ve always been done, you’re always going to get the same result. No one buys into us because of our eco credentials. It’s because it’s different and it’s an extra that it’s eco as well.”

The hope is that the hi-tech being invented for these grand expeditions starts to appear in workaday contexts. This month, Dutch researchers unveiled a prototype family car that can travel 420 miles on a sunny day and 250 miles when there is no sunshine, at a low price: its solar cells cost only £2,000. Interactive Fully Electrical Vehicles is an Italian company set up to commercialise solar-powered vehicles for the continent’s roads. And the US version of the electric Nissan Leaf features a solar panel on its spoiler that trickle-charges the auxiliary battery.

That the technology involved in these project is already finding its way into mass-markets and may one day solve our sustainable transport needs is a very exciting prospect.

For more information: Solar-powered travel: opening up new routes across sky, sea and land

References:

  1. Ford hybrid and electric sales quadruple
  2. http://www.electricdrive.org/index.php?ht=d/sp/i/27132/pid/27132
  3. Hybrid car sales set for explosive growth as slow electric car sales continue, says RAC Foundation

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