It was last March that Swiss aviators Bertrand Piccard and André Borschberg began a round-the-world trip in their completely solar-powered aircraft, the Solar Impulse 2. Unfortunately, during a July stopover in Hawaii, they discovered that the batteries had overheated, causing serious damage. Now, however, they're finally set to resume their journey.
The Solar Impulse 2 now has new batteries, stabilization and cooling systems, and has been on a total of 13 test flights around Hawaii since late February. Those flights indicated that the new systems were in good working order, plus they helped Piccard and Borschberg prepare for the next leg of the trip – a non-stop flight east to North America.
As of this Friday, the team will officially re-enter "mission mode," and start checking meteorological forecasts to identify favorable departure windows. Depending on the weather and other variables, the destination city may be Phoenix, San Francisco, Los Angeles or Vancouver – a decision will be made a couple of days in advance.
Assuming all goes well with that flight, it will be followed by flights to New York, Europe or North Africa, and then finally to the original starting point of Abu Dhabi in the United Arab Emirates.
A montage of what went on during the team's past eight months in Oahu, Hawaii, can be seen below.
Source: Solar Impulse
Initial attempts at flight powered by gasoline did not go far because of the design issues of the plane and the engine technology. The gasoline always had the energy potential to power the plane to the extent that we do today (with lots more room of improvement).
This plane is huge, yet it can't accommodate any payload above and beyond the 2 pilots. Yes, the batteries can be charged via solar on the ground. But the plane will still be very slow. And the slower it is (vs conventional technology), the larger it's payload have to be to become economically feasible. Putting solar cells (even at 100% efficiency) on a plane is not a solution now and never will be. Charging batteries on the ground with solar power to fly electrical planes is. That is a technology that currently is not ready for prime time, but it is getting there, can get there and will get there. Solar cells on a plane will never be a viable technology.
The payload isn't /just/ the pilots. It's also several days worth of water and food. In theory the same technology could be used to build drones that could stay up for ever because it would have more favorable aerodynamics without a cockpit and not need to carry a pilot. Take a look at the ARGUS survalence system if you want an idea of what the implications for the technology could be: https://www.youtube.com/watch?v=QGxNyaXfJsA
The technology could help enable full time city wide surveillance and archive the footage.