There are 2 competing air-powered engines: one from France that uses an engine similar to the internal combustion type we're all familiar with, but powered by air; and another developed in Australia that uses a unique rotary design (the "di Pietro Engine").
Part 1: France
Part 2: Australia
I'm more partial to the Australian design. Critics claim air is only a energy medium and filling up with air still takes an energy source, therefore, not solving any energy problems. While (perhaps) this is true, it also produces no emissions.
Puffy no Gaki no Tsukai ya Arahende!!
3 weeks ago