This week, a Swiss team unveiled the Solar Impulse 2 , claiming to be the only airplane of “perpetual endurance,” flying day and night on sunlight, using zero drops of fuel. For its biggest challenge, the Solar Impulse 2 will attempt the first solar flight around the world starting in the spring of next year.

Last summer, its predecessor, Solar Impulse 1 , traveled across the U.S. from San Francisco to New York, making five pit stops along the way. Powered by sunlight in the day, it glided slowly downward at night using its lithium batteries.

The new plane builds on that one in a few ways: bigger cockpit, bigger wingspan, and lighter materials. Even though its wings span as far as a Boeing 747, the new plane weighs only 2,300 kilograms, or about as much as an SUV. To cut down on power wasted, its motors are 97 percent efficient, and it has a top speed of about 140 kilometers an hour (about 40 miles per hour).

The top of the wings are made of 17,000 weatherproof solar cells -- about 135 microns thick -- which will charge batteries in the day to run its four 17.5 horsepower engines. Batteries tucked behind the engines can store 165 kilowatt-hours. At night, the plane will slow down, gradually gliding closer to sea level as the engines run off batteries. When the sun comes up, the plane will gain altitude and speed. There will be no fuel on board.

The aircraft is mostly wings, and it only seats one. The project’s directors, Andre Borschberg and Bertrand Piccard, will trade off at scheduled stops in several countries along the way. Those stops won’t be very frequent though: The cockpit is designed for the pilot to stay in for five consecutive days and nights (the amount of time they plan to fly over the larger oceans). The comfy new seat also serves as a toilet and a bed in the 3.8 meters squared cocktpit. “We went from a bad economy class on the first plane to a good business class seat,” Borschberg jokes . Although, the cabin isn’t pressurized or heated, for maximum energy efficiency, so living on a plane will be the team’s other challenge.

The plan is to start in the desert near the Persian Gulf, fly over Myanmar and China, then across the Pacific, the U.S., the Atlantic, and finally, over land near Mediterranean -- and all within a five months’ time. You might remember Piccard as the first man to take a balloon around the globe , back in 1999.

Test flights will begin next month, and the big one is planned for March or April 2015. Below is a video that describes the construction of the new aircraft.