alt Hacker News60% efficiency? How do these power plants manage to circumvent the limit set by Carnot efficiency?
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slavik81 • yesterday at 8:54 PM
Natural gas burns at ~2200 K. Ambient temperature is ~300 K. 1 - 300/2200 = 86% as the Carnot limit?
60% efficiency? How do these power plants manage to circumvent the limit set by Carnot efficiency?
Natural gas burns at ~2200 K. Ambient temperature is ~300 K. 1 - 300/2200 = 86% as the Carnot limit?
They don’t. they capture the waste heat from the gas turbine and use it to make steam to spin another turbine. A gas turbine is ~40% efficient, add in a HRSG to make a combined cycle plant and you can get up to ~60%. You don’t even need a gas turbine to use a HRSG, any exhaust stream with enough heat will work, a boiler plant or similar.
https://en.wikipedia.org/wiki/Heat_recovery_steam_generator
https://en.wikipedia.org/wiki/Combined-cycle_power_plant