# How can I make the heat engine efficiency become 100%? [closed]

Is it possible to make it 100%? Or in what kind of situation the heat engine efficiency could be 100%?

## closed as off-topic by DilithiumMatrix, AccidentalFourierTransform, Jon Custer, Wolpertinger, GertNov 29 '16 at 6:57

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• One that (A) reaches the theoretical maximum efficiency for its operating conditions and (B) uses a cold reservoir at absolute zero. (A) is a engineering impossibility and (B) is a plain old impossibility. – dmckee Nov 27 '16 at 23:23
• Please do some research! eg read What's the efficiency of real heat engines? or Why is the Carnot engine the most efficient? – sammy gerbil Nov 27 '16 at 23:28
• I'm voting to close this question as off-topic because it shows a complete lack of effort or research. – DilithiumMatrix Nov 28 '16 at 0:12

## 1 Answer

According to Carnot's Theorem Carnot's Theorem, the maximum efficiency of a cyclic heat machine working between a hot reservoir at absolute temperature $T_h$ and a cold reservoir at $T_c$ is $$\eta=\frac{W}{Q_h}=1-\frac{T_c}{T_h}$$ where $W$ is the work done and $Q_h$ is the heat entering the machine. Therefore, the efficiency increases for large $T_h$ and small $T_c$ and approaches $1$, i.e.100%, for $T_c \to 0K$, which is, however not a practical working condition.