The future of aviation was on display at the recent Paris Air Show. Many concepts at the show featured super-fast speeds and low emissions, but one concept, the VoltAir, stood out for its zero-emission, all-electric propulsion technology. As powerful as it is efficient, the VoltAir will be powered by a pair of advanced li-ion batteries beneath its nose, which send power to a pair of co-axial, counter-rotating propellers shrouded at the rear of the aircraft. It’s expected to be far quieter than traditional combustion engine aircraft. Although its innovative propulsion system would radically…