Look Ma, No Fuel! Flying Cross Country on Sun Power

This week one of the strangest flying machines you’ve ever seen will start its journey across America—without a drop of fuel

The Solar Impulse flying over San Francisco at night.
The Solar Impulse flying over San Francisco at night. Photo courtesy of Jean Revillard/Solar Impulse

Bet you didn’t know that Texas has more solar energy workers than ranchers and California has more of them than actors, and that more people now work in the solar industry in the U.S. than in coal mines.

Or that in March, for the first time ever, 100 percent of the energy added to the U.S. power grid was solar.

Okay, so now you know all that, but I’m guessing you’re no more aquiver over solar energy than you were five minutes ago. That’s the way it is in America these days. Most people think solar is a good thing, but how jazzed can you get about putting panels on a roof.

Bertrand Piccard understands this. Which is why later this week, weather permitting, he will take off from Moffett Field near San Francisco and begin a flight across the U.S. in a plane entirely dependent on the sun. Called Solar Impulse, it will move at a snail’s pace compared to commercial jets–top speed will be under 50 miles per hour–and will stop in several cities before it ends its journey in New York in late June or early July.

But the point isn’t to to mimic a plane in a hurry, crossing the country on thousands of gallons of jet fuel. The point is to show what’s possible without it.

Batteries included

To do this, Piccard and his partner, André Borschberg, have created one of the strangest flying machines ever–a plane with the wingspan of a jumbo jet, but one that weighs about a ton less than an SUV. Its power is generated by nearly 12,000 silicon solar cells over the main wing and the horizontal stabilizer that charge lithium-polymer battery packs contained in the four gondolas under the wing. The batteries in total weigh almost 900 pounds–that’s about one quarter of the plane’s weight–and they’re capable of storing enough energy to allow the plane to fly at night.

Piloting the Solar Impulse is neither comfortable nor without a good deal of risk. Only one pilot can be in the cockpit–a second adds too much weight–and the engines are vulnerable to wind, rain, fog and heavy clouds. But Piccard is, by blood, an inveterate risk-taker. In 1999, he co-piloted the first gas-powered balloon to travel non-stop around the world. In 1960, his father, Jacques, was one of the two men aboard the bathysphere lowered into the Marianas Trench, the deepest part of the world’s oceans. In 1931, his grandfather, Auguste, was the first balloonist to enter the Earth’s stratosphere.

It was near the end of his own record-setting balloon trip that Bertrand Piccard was inspired to find a way to fly without needing to rely on fuel. He almost ran out of propane while crossing the Atlantic. He and Borschberg spent years planning, designing and finding investors–that was no small challenge–but they persevered and, in 2010, the Solar Impulse made the first solar-powered night flight over Switzerland. Last year it completed the first solar intercontinental flight, from Europe to Africa.

The ultimate goal–after the flight across America–is to fly a solar plane non-stop around the world. That’s tentatively scheduled for 2015, but it will require a bigger plane than the Impulse. Since they estimate that it will take three days to fly over the Atlantic and five to cross the Pacific, Piccard and Borschberg have been making other alterations, too–the larger version will have an autopilot, more efficient electric motors and a body made of even lighter carbon fiber. It also will have a seat that reclines and yes, a toilet.

There certainly are easier ways to go around the world, but Piccard sees his mission as stretching our imaginations about the sun’s potential. “Very often, when we speak of protection of the environment, it’s boring,” he said during a recent interview with Popular Science. “It’s about less mobility, less comfort, less growth.”

Instead, he wants to show that clean energy can just as easily be about being a pioneer.

Here comes the sun

Here’s other recent developments related to solar power:

  • It’s always good to save some for later: A team of researchers at Stanford University has devised a partially liquid battery that could lead to the development of inexpensive batteries which can store energy created by solar panels and wind turbines. One of the challenges of both sun and wind power is to be able to store energy efficiently so it’s available when the sun’s not shining and the wind’s not blowing.
  • Forget the undercoating, we’ll throw in solar panels: BMW, which will begin selling its first electric cars later this year, says it will offer buyers the opportunity to get a solar-powered home charging system designed to be installed in their garages.
  • Go ahead and fold. Avoid spindling and mutilation: A Milwaukee middle school teacher-turned-inventor has created a small, foldable solar array that can charge an iPhone in two hours. Joshua Zimmerman turned what had been a hobby into a company named Brown Dog Gadgets and he’s already raised more than $150,000 on Kickstarter to get his business off the ground.
  • And you thought your shirt was cool: An Indian scientist has designed a shirt containing solar cells that power small fans to keep the wearer cool. The shirt would also be able to store enough juice to charge cell phones and tablets.
  • Charge of the light brigade: Since you never know when you need a lantern, there’s now a solar powered bottle cap that lights up your water bottle. Its four bright, white LED lights can turn your beat up water bottle into a shiny beacon.

Video bonus: Take a peek at the Solar Impulse during its test flight over San Francisco last week.

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