2 options here Dear K1W1, 1. Only air-power: you're right, limited range. But an average day cruising with a little to medium size boat (one has to start somewhere, no?) involves 3 hours motoring on average. At cruising speed this means some 250-300 liters of air at 300 bars, with 2 (small) engines. At night you re-plenish the air-tanks with the shore-power and the built in compressor. 2. Dual energy: air + any-fuel. Thermo-dynamic cycle was expained some replies ago, but in short it goes like this: air intake > compression with the built-in compression pistons (lose some 30% power) > external combustion with any-fuel (at temps lower than to generate NOx) > expansion of the heated + compressed air > exhaust. This allows for a very important range with small air-tanks and small any-fuel tanks (consumption approx 0.8L/HR). Perhaps "seeing is believing"! You're more than welcome.