3 ms·

The title is somewhat overstatement, EPA says turbines have efficiencies up to 90%: "Multistage (moderate to high pressure ratio) steam turbines have thermodyna

The title is somewhat overstatement, EPA says turbines have efficiencies up to 90%: "Multistage (moderate to high pressure ratio) steam turbines have thermodynamic efficiencies that vary from 65 percent for very small (under 1,000 kW) units to over 90 percent for large industrial and utility sized units. Small, single stage steam turbines can have efficiencies as low as 40 percent."

wrycoder 5y ago
Typical steam turbines have efficiency up to around 50%. I think the EPA is referring to isentropic efficiency[0], which is "efficiency" compared to the theoretical maximum for the delta T involved. [0] https://en.wikipedia.org/wiki/Steam_turbine#Thermodynamics_of_steam_turbines https://en.wikipedia.org/wiki/Steam_turbine#Thermodynamics_o...
franciscop 5y ago
Yes, it's comparing apples to oranges, or the efficiency of the whole steam turbine plant (electricity/fuel) vs just a single component (electricity/heat). Is the comparison fair? Well it's tricky but I'd say yes, the generation of just heat from fuel is normally highly efficient so electricity/heat should be similar to electricity/fuel in the second case. However in a turbine generating plant it's not plain heat but it needs to be converted to steam and moved around, so there are many more loses. That paragraph in [1] is referring to: "Isentropic steam turbine efficiency refers to the ratio of power actually generated from the turbine to what would be generated by a perfect turbine with no internal flowpath losses using steam at the same inlet conditions and discharging to the same downstream pressure." It specifically says not to confuse them: "Turbine efficiency is not to be confused with electrical generating efficiency, which is the ratio of net power generated to total fuel input to the cycle." [1] https://www.epa.gov/sites/default/files/2015-07/documents/catalog_of_chp_technologies_section_4._technology_characterization_-_steam_turbines.pdf https://www.epa.gov/sites/default/files/2015-07/documents/ca...

wrycoder 5y ago

Typical steam turbines have efficiency up to around 50%. I think the EPA is referring to isentropic efficiency[0], which is "efficiency" compared to the theoretical maximum for the delta T involved. [0] https://en.wikipedia.org/wiki/Steam_turbine#Thermodynamics_of_steam_turbines https://en.wikipedia.org/wiki/Steam_turbine#Thermodynamics_o...

franciscop 5y ago

Yes, it's comparing apples to oranges, or the efficiency of the whole steam turbine plant (electricity/fuel) vs just a single component (electricity/heat). Is the comparison fair? Well it's tricky but I'd say yes, the generation of just heat from fuel is normally highly efficient so electricity/heat should be similar to electricity/fuel in the second case. However in a turbine generating plant it's not plain heat but it needs to be converted to steam and moved around, so there are many more loses. That paragraph in [1] is referring to: "Isentropic steam turbine efficiency refers to the ratio of power actually generated from the turbine to what would be generated by a perfect turbine with no internal flowpath losses using steam at the same inlet conditions and discharging to the same downstream pressure." It specifically says not to confuse them: "Turbine efficiency is not to be confused with electrical generating efficiency, which is the ratio of net power generated to total fuel input to the cycle." [1] https://www.epa.gov/sites/default/files/2015-07/documents/catalog_of_chp_technologies_section_4._technology_characterization_-_steam_turbines.pdf https://www.epa.gov/sites/default/files/2015-07/documents/ca...