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Stanley514
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According to Carnot theorem, the higher temperature of a hot side and the lower temperature of a cold side the higher is the efficiency of a heat engine. Does it mean that in theory it could get anywhere close to 100%? If we take in account that 100% efficiency means it is a perpetuum mobile, does it mean that once we start to approach 100% efficiency, the demand for energy input to do some work will decrease exponentially? For example, if we have Stirling engine with 40% efficiency which requires 1 kg of a fuel to produce 1000 kW-h, then how much of the same fuel we need to produce the same work with a similar engine which is 99.99% efficient?