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Originally Posted by tech
How does one calculate the efficency of a system? eg. gasoline combustion engine.
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there are many things that go into this, in the most simplest of terms its a relation between energy put into a system vs energy you get out. in the combustion engine it's energy that is generaged by the combustion process vs kinetic energy at the crank (assuming we are talking only about the engine). In a hydrogen fuel cell, its energy produced by the oxidation of hydrogen vs the electric energy produced by the cell.
here's the thing, you cant think on a small scale when you are guesstimating the efficiency of a car as a system, you need to take into the consideration, not only how the fuel is obtained, but also how that energy at thhe crank gets used, the efficiency of a petrol-burning vehicle depends on the extraction process, the burning process, the efficiency of the engine, the efficiency of the transmission, the overall weight of the vehicle, the efficiencu of the ectual propulsion system, aka, what are we spinning, etc.
hydrogen systems are easier, it is much simpler to calculate what the efficiency of the extraction process is, rather, the energy input at that stage, and then you start calculating output, and the efficiency of the fuel cell, and the electric motor, as well as the propulsion system, also considering the weight of the car...
many factors, its not a simple 3+2=11 deal...
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