Muir still cites fuel sourcing and storage as the big obstacles to mass-market viability for hydrogen-powered vehicles. Like most fuel-cell vehicles, Mazda's rotary hydrogen vehicles will store and use hydrogen in its gaseous form, not liquid as in BMW's hydrogen internal combustion 7 Series.
But with even the BMW's optimally efficient (and complicated) liquid hydrogen storage still approximately four times less energy dense by volume than hydrocarbon fuels like gasoline, according to Wikipedia, hydrogen engineers clearly have their work cut out for them. Gaseous compressed hydrogen is even less energy-dense, requiring enlarged tanks for adequate range.
Autocar believes that a next-gen RX-7 would be the likeliest candidate for a hydrogen-fueled rotary engine. With no mention of an RX-8, we wonder if they know something we don't know about the future of Mazda's rotary-powered sports car.--Colin Mathews