Electric propulsion, in performance terms alone, will always lag behind fossil fuel power for all forms of transport until there is a breakthrough in battery technology. Until batteries can be as light as fuel tanks - and store the same amount of energy and fill up at the same rate - the automobiles, ships and aircraft they power will never be able to go as fast or as far as their fossil-fuel competitors.
That’s been the case until now, at least. But perhaps the electric revolution will come not with a single eureka moment but hundreds of small and slight advances which, taken together, will result in in a revolution after all
That’s the thinking behind Solar Impulse 2 which in March 2015 will start a solar-powered round-the-world voyage.
"We are scrutinising a multitude of options in several technological fields from solar, storage to low voltage equipment to see where both can profit from each other’s expertise,“ said André Borschberg, one of the pilots on the trip. "We can already consider multiple developments in the area of ultralight materials and energy savings, in the efficiency of components, in greater reliability and performance of electric motors.
The aircraft has been designed and built to flight test a range of energy saving systems and structures – the target is to develop a heavier-than-air aircraft with perpetual endurance, which means combining efficient electric engines, clever power storage and incredibly light structures. One of the key technology features on board the aircraft is the lightness of the carbon fiber skin, which at 25 grams per square meter, weighs only a third as much as sheets of printer paper.
Already, some of the technologies being explored by the Solar Impulse team can be taken and used on other aircraft. Airbus has its technology teams working on a small electric-powered aircraft which flew earlier this year: the E-fan which it is showing off this week at the Farnborough Air Show. Airbus will further develop the E-Fan technology demonstrator and to produce and market two versions of the aircraft by a subsidiary named VoltAir called E-Fan 2.0, which will carry two passengers and the e-Fan 4.0, which will carry four. While the 2.0 will be battery powered, the 4.0 will be a hybrid for greater range.
It’s a long way from developing an electrically-powered large commercial airliner – but, if the Solar Impulse team can build an aircraft that can cross oceans and deserts, in day and night, without carrying a drop of fuel, it will represent the same kind of technology step that Louis Bleriot realised when he crossed the English Channel in 1909. Quite small, but very, very significant.