Putting all together now, the predicted overall thermal efficiency of the combined cycle power plant is:
TURBINE THERMODYNAMICS CALCULATOR GENERATOR
= function of generator design, voltage, windage losses (air drag), type of gas cooling (hydrogen, air), bearing lubrication = function of drive shaft design, clutch system, bearing lubrication, mechanical design, windage losses (air drag) ME = mechanical drive shaft and clutch efficiency = 100% = function of steam inlet temperature, steam exhaust pressure, condenser vacuum pressure, cooling system, steam turbine design, steam quality STE = steam turbine efficiency = 37% (up to 40%) = function of exit flue gas temperature (energy lost), gas turbine exhaust temperature (energy input), boiler design, flue gas composition (fuel, excess air) = function of heat loss from GT due to conduction, convection and radiation from GT casing, any heat loss due to friction resulting in higher GT exhaust is captured, however, by the heat recovery steam generator GTE = gas turbine efficiency = say 90% - 95% (the reader please comment or advice) Where OE = overall energy efficiency, % of fuel energy input (as GHV or LHV) OE = (GT x GTE + SG x BE x STE) x ME x GE The final formula is thus: (with correction for GT efficiency) The mechanical energy captured in the GT and ST shafts are then coupled in a clutch (100% efficiency) to drive finally the electric generator (EG) with mechanical to electrical conversion efficiency of 98% (balance of 2% lost to heating in the generator windings and generator cooling system).
The steam energy is then captured in the steam turbine with an efficiency of 37% and the balance (63%) is lost to the cooling water in the condenser. The energy input to the steam generator is then split into 85% (up to 90%) being recovered as steam energy in the boiler while the balance of 15% (or 10%) is lost to the atmosphere (smoke stack, radiation and convection loss). Then let's assume that the proportion of the energy input going to the gas turbine (GT) and to the waste heat recovery steam generator (SG) is around: Let Total Energy Input = Total Energy Output = 100%. Your favorite energy technology expert has derived the following equation to guide the design engineer and project finance modeler or business development engineer in predicting the overall thermal efficiency of the combined cycle.
TURBINE THERMODYNAMICS CALCULATOR HOW TO
How to calculate overall thermal efficiency of combined cycle power plantsĬalculating or predicting the overall performance of a combined cycle power plant, specifically a combined cycle gas turbine (CCGT) power plant is sometimes difficult for most design engineers.
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