Battery-powered cars are a big deal all of a sudden, so why not a battery-powered plane? The European Aeronautic Defence and Space Company, better known for being the parent company of Airbus and Eurocopter, has been working on this concept aircraft which could be flying us around on battery power by 2035.
The VoltAir concept (funny on so many levels) is a zero-emission passenger aircraft that runs entirely on batteries. Specifically, it uses lithium-air batteries, which have very high energy to weight ratios of greater than 1,000 watt hours per kilogram. To get around the fact that fancy futuristic batteries still need to be recharged, the entire battery system would be able to be swapped in and out while the plane is on the ground changing out passengers at the same time.
Powering the plane is (or, you know, will be) an ultra high density superconducting electric engine that promises to be nearly silent, super efficient, and basically everything you could possibly want in an engine short of something that could push you to super high Mach numbers. Yeah, this may not be the ultra-fast plane of the future, but it's quiet and efficient and eco-friendly, all features that you'll have ample time to appreciate as you watch those big loud fuel-guzzling supersonic jets blow past you.
I have to say, I kinda feel like batteries are the wrong way to go on this one, and I'm hopeful that by 2035 we'll have a better way of storing energy. Whether or not they're initially efficient, the problem with batteries is that they get progressively less efficient, to the point where your batteries only have (say) 10% of their charge left but you're still carrying the other useless 90% of them around with you anyway.
Don't get me wrong, lithium-air batteries are leaps and bounds better than something like lead-acid batteries, but I'm still pulling for ground-based laser propulsion.