An all-electric aircraft will be more efficient, produce fewer greenhouse emissions and be quieter but current technology cannot be used because an electric motor using conventional magnets can weigh up to five times as much as conventional jet engine and not be as fuel efficient.

Superconducting motors are the answer to greenhouse emissions from plane flights, according Philippe Masson and Cesar Luongo from Florida State University, Gerald Brown at NASA and Danielle Soban at Georgia Institute of Technology. They explain that because superconductors lose no energy through electrical resistance, they could be very efficient components for a new type of aircraft propulsion.

The researchers explain that an electric aircraft will require propulsion motors would be high power, compact and far more efficient electrically, generating three times the torque of a conventional electric motor for the same energy input and weight. In addition, an electric aircraft would be quieter than a conventional jet as there are no internal combustion processes involved. It is the combustion of fossil fuels to drive a conventional aircraft that makes them so noisy.

However, superconducting magnets not only have to be cold, but require a unique energy supply. Masson and his colleagues believe they could solve both problems by using chilly liquid hydrogen to run an electric fuel cell. Liquid hydrogen is cold enough to make the superconducting magnets work but also has four times as much energy weight for weight than aviation fuel.

A fuel cell produces no polluting emissions, just warm water as the hydrogen combines with oxygen. This, say the researchers would mean zero carbon emissions from the aircraft as it flies. "The idea is to reduce the emissions from the aircraft and airports," explains team leader Masson, "The energy needed to produce the liquid hydrogen could come from a remote powerplant". Such a powerplant might be solar or wind powered.

"We could potentially build a superconducting motor and generator smaller than a gas turbine, which would make possible electric propulsion," says Masson. Electrical propulsion would not only decrease emissions but also reduce to a minimum the needs for maintenance as all hydraulic systems would be eliminated, he adds. The team has designed such systems with high fidelity models and optimization tools.

Masson adds that the team is now looking for an industrial partner to build a prototype of the superconducting "turbofan". "The technology is there," he says, "it is a matter of finding a source of funding."

Source: Institute of Physics