http://www.golehr.com/products.shtml
A ridiculous application:
http://www.goped.com/products/proped/default.asp
It is a 25cc engine of 1HP therefore 750 W.
The scooter gives 20 miles (32 km) at 20 mph (full speed) for a 16.4oz (460g) "can". The trimmer gives 2 hours for the same can.
Autonomy is excellent for a scooter: on this kind of machine, one hour at 32 km / h is more than enough to kill yourself 10 times ...
Well. The can contains roughly 6 kWh (46.4 MJ / kg). It is 24x the capacity of an electric bicycle battery, it is still necessary to transform this chemical energy into mechanical energy ...
By the way, this scooter is really annoying: 185 Wh primary energy per km ... it's true that it's a little less than a car, we understand why they sell it to sores
...
As we don't yet have a suitable fuel cell (apparently research is concentrated on hydrogen, I wonder why ...) there remains the good old piston engine.
1 HP = 750W for one hour = 750 Wh, which gives us a 12% efficiency for the motor of the scooter.
It's not terrible. At the current price of propane (2 € per kilo approximately) that makes us the mechanical kWh around 1.20 €, so horribly expensive, almost double the electric kWh coming from a battery.
Perhaps the efficiency could be higher with the motor not "full".
On the other hand, that puts the km in elevation at around 0.40 € ... which is reasonable.
