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Well, a binary cycle geothermal power plant utilizes the low temperature of the primary liquid to generate heat. I found out that they are only 10% to 15% efficient.

Is the continuous flow of the primary fluid a major cause for such inefficiency? From what I understand due to the continuous flow of the primary fluid the secondary fluid is only able to capture a portion of that heat due to continuous flow of primary fluid.

Or is the inefficiency is due to the use of a low boiling point secondary fluid?

Please guide me if I am wrong in my assumptions. I researched a bit but was not able to clear my doubt so though to seek some expert advice.

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There is a general rule for any heat-driven engine called the carnot efficiency which tells you for any delta T between the hot and cold side of the engine what the maximum possible thermodynamic efficiency can be for any process operating between those temperatures. It is equal to the temperature difference divided by the product of the two temperatures.

For source temperatures that are relatively low (delta T = small), the maximum possible efficiency will be low, and that is what's happening in your case here.

Maximizing the efficiency requires running the hot side at the highest temperature that the machine can withstand without damage while rejecting the waste exhaust at the lowest possible temperature. In big natural gas-fired power plants, the burners that power the turbines are running close to the softening limit of the turbine blades and the exhaust side is cooled with river water.

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