Most of the thousands and thousands of airplanes that fly around the world each day use their main engines to move around on the ground when they are landed at airports. That's kind of like using your car to go pay a visit to your neighbor who lives across the street. It works, but it's very wasteful and produces unnecessary pollution. Thankfully, greener ways of taxiing planes are coming (we've already wrote about Taxibot, a robotic tug). One of those is a system called Electric Green Taxiing System (EGTS), developed by Honeywell and Safran.
The photo above was taken at the Paris Air Show. The engines are covered to demonstrate that this Airbus A320 can taxi around simply on electric power. The system uses a 50kW electric motor sandwiched between the landing gear wheels. It is powered by the plane's auxiliary power system; there's no such thing as a free lunch, so this still uses power and burns fuel, but about 1/6 of what the main engines would use to do the same thing.
The makers of the EGTS estimate that about 150 gallons of fuel can be saved during a multi-flight day. That's not a huge amount compared to what a plane will burn while flying (about 4% of total -- not too bad considering that the aerospace industry is constantly tweaking things to gain a few percents in efficiency), but a small fraction of a really huge number is still significant, especially if you multiply it by all the big commercial planes in the world. The should also be an improvement in air quality at and around airports, especially busy ones.
Check out the EGTS in action:
Planes have such long lives that these systems will probably be retrofitted to existing planes. But ideally, new models by Boeing and Airbus would all feature electric taxiing built-in. If a plane is designed form the ground up for it, fuel savings from electric taxiing should be even higher.
For some out-of-the-box thinking, check out: Civilian Airplanes Could Someday Take-Off With Electric Catapults!