Battery-Powered Planes

Source : Forbes

By MIT Technology Review Custom, an Energy Realities Partner

Batteries are becoming ever more compact; solar panels are becoming ever more efficient; and composite frame-construction materials keep getting both stronger and lighter. The products of those three trends are spreading throughout the world of technology, not least by making feasible what until recently had been only a sci-fi dream: electric airplanes.

To be sure, an electrically powered heavy-duty commercial aircraft that can handle passengers and cargo the way today’s airliners do is, at best, two or three decades away. The main obstacle: petroleum products, especially jet fuel, have tremendous energy density; that is, they provide enormous amounts of power relative to their weight. Unfortunately, electric batteries currently offer barely more than six percent of gasoline’s energy density. Lack of energy density is one reason that the batteries that power popular electric cars like the Tesla can weigh half a ton, about a quarter of the weight of the entire vehicle.

But those limitations notwithstanding, scores of experimental lightweight electric airplanes already exist that are capable of carrying one or two people for long distances—and soon, around the world. Many of these are basically electrified gliders, which need a tow from another plane to get airborne, but can stay up in the sky with the help of solar panels.

The Taurus Electro G2 takes a different approach, made by glider manufacturer Pipstrel. That aircraft has an electric engine that lifts it aloft, at which point the engine retracts and the Taurus operates like a traditional glider.

The Taurus is priced at $130,000, and is available commercially. Most other electric airplanes are experimental devices, and not in regular commercial production. As befits the Wright brothers-like spirit of their creators, these aircraft often make news with their exploits. The most famous is the Swiss-made Solar Impulse, a project of the École Polytechnique Fédérale de Lausanne that is funded mainly by a number of European companies, including Bayer and Deutsche Bank, and which, true to its name, gets its energy from solar panels. Those panels provide enough power for the Solar Impulse to take off by itself.

This summer, the Solar Impulse made headlines by flying across the United States in six hops, with each hop lasting between 19 and 25 hours. Electric planes still have a long way to go in matching traditional jets in the speed department.

The ultimate journey — around the world — is scheduled for 2015, featuring a redesigned Solar Impulse that will combine the weight of an average automobile with a wingspan of 80 meters, wider than that of an Airbus A30. It will fly at an altitude of up to 12,000 meters (40,000 feet) and stay aloft for up to five days. Circumnavigating the globe is expected to require four or five separate flights.

Where might all this lead? One of the most ambitious attempts at imagining a future all-electric aircraft is the VoltAir, which the European Aeronautic Defence and Space Company (EADS), the European consortium behind the Airbus, has been showing off as a “concept plane” at aviation industry events, including the famous biennial Paris Air Show. The body of the VoltAir is cucumber-shaped; its wings are long and thin; and the engine is located at the back of the fuselage. The plane will be made with the next-generation carbon-fiber materials already found in today’s advanced aircraft, like the Boeing Dreamliner.  But much of the rest of the VoltAir doesn’t yet exist, at least not outside a few specialized laboratories. Chief among its still-to-be-developed components are super-conducting electric motors to run the engines, and ultra-advanced lithium ion batteries that are to power them.

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This article is also published on the Energy Realities website.

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