Several times I have read that steam engines have a low efficiency, what is the energy lost as?
Answer:
An "efficient" steam engine (multistage steam turbine) will be appx 60% efficient at converting the heat input into useful power.
Then there's the efficiency of the generator if you are making electricity... Its very hard to get better than 90% efficiency from a generator.
so using a steam turbine to make electricity is approximately 54% efficient. (assuming the heat from burning the fuel 100% goes to heating the water...)
The waste energy goes to waste heat. the leftover steam comming out of the turbine has to be cooled to turn it back into water, to be pumped back into the steam generator.
The generator also makes waste heat.
AND... the fuel burning to heat the water and make steam is not 100% efficient because not all of the heat from burning the fuel goes into the water. Some of t leaves via the exhaust stacks with the CO CO2 and other byproducts of combustion.
HEAT!!
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