Combined-Cycle Development Evolution and Future

1 GE Power SystemsCombined-CycleDevelopmentEvolutio n and FutureDavid L. ChaseGE Power SystemsSchenectady, NYGER-4206gContentsIntroduction.. 1 Gas turbine Combined-Cycle Features.. 1 Gas turbine Combined-Cycle Development .. 5 First Generation Combined-Cycle Plants .. 5 Second Generation Combined-Cycle Plants .. 6 Third Generation combined Cycles .. 6 Fourth Generation Combined-Cycle Plants .. 9 References.. 13 List of Figures.. 13 List of Tables.. 13 Combined-Cycle Development Evolution and FutureGE Power Systems GER-4206 (10/00)iCombined- cycle Development Evolution and FutureGE Power Systems GER-4206 (10/00)iiIntroductionCombined- cycle systems utilizing the BraytonCycle gas turbine and the Rankine cycle steamsystem with air and water as working fluidsachieve efficient, reliable, and economic powergeneration.

2 Flexibility provided by these sys-tems satisfies both utility-power generation andindustrial-cogeneration commercially available power-genera-tion Combined-Cycle plants achieve net plantthermal efficiency typically in the 50 55% LHVrange. Further Development of gas turbine ,high-temperature materials and hot gas path,metal surface cooling technology show promisefor near-term Future power generation com-bined- cycle systems capable of reaching 60% orgreater plant thermal efficiency. Additional gasturbine technological Development , as well asincreases in steam- cycle pressure and tempera-ture and steam- turbine stage-design enhance-ment, is expected to achieve further STAG Combined-Cycle efficiency General Electric STAG (trade namedesignation for the GE product line of com-bined- cycle systems)

3 Product line offerings, Combined-Cycle experience, and advanced sys-tem Development are used to demonstrate theevolution of Combined-Cycle system turbine Combined-Cycle FeaturesThe combination of the gas turbine BraytonCycle and the steam power system RankineCycle complement each other to form efficientcombined-cycles. The Brayton cycle has highsource temperature and rejects heat at a tem-perature that is conveniently used as the energysource for the Rankine cycle . The most com-monly used working fluids for combined cyclesare air and steam. Other working fluids (organ-ic fluids, potassium vapor, mercury vapor, andothers) have been applied on a limited systems that utilize steam andair-working fluids have achieved widespreadcommercial application due to:1.

4 High thermal efficiency throughapplication of two complementarythermodynamic Heat rejection from the Brayton cycle (gas turbine ) at a temperature thatcan be utilized in a simple andefficient Working fluids (water and air) that arereadily available, inexpensive, Combined-Cycle systems provide flexibili-ty with features that include:1. High Thermal Efficiency- Combined-Cycle thermal efficiency is higher thanthat of other conventional powergeneration Low Installed Cost- combined -cycleequipment is pre-engineered and factory-packaged to minimize installation timeand cost. All major equipment (gasturbine generator, heat recovery steamgenerator [HRSG], and steam turbinegenerator) is shipped to the field asassembled and tested equipment, such as condensers,can be shipped factory-tubed and hydro-tested.

5 This greatly reduces the inventoryof parts that must be managed in thefield and minimizes installation equipment cost is higherthan that for conventional steam plantsdue to pre-engineering; however, Combined-Cycle plant installation costsare significantly lower, resulting from thereduced installation Fuel Flexibility- combined -cycleplants operate efficiently by burning aCombined- cycle Development Evolution and FutureGE Power Systems GER-4206 (10/00)1wide range of fuels, ranging from cleannatural gas and distillate oil fuels to ash-bearing crude oil and residual oil with coal-derived gas fuels hasbeen applied in many commercial-size, Combined-Cycle Flexible Duty cycle - combined -cyclesystems provide flexibility in operationfor both baseload and mid-range dutywith daily startup.

6 Gas turbines in multi-shaft, Combined-Cycle configuration canbe started quickly, bringing about two-thirds of plant power on-line, typically inless than 60 minutes. combined -cycleplants also provide efficient operation atpart load, particularly for multiple gasturbine Combined-Cycle systems. This is il-lustrated by the variation in plant outputwith variation in plant heat rate curveshown for a General Electric STAG 200system (See Figure 1). Modulatingcompressor inlet guide vanes arestandard features of many gas turbinemodels, enabling high efficiencyoperation at part load through reductionin turbine airflow.

7 This is accomplishedat nearly constant turbine exhausttemperature, so that design steamconditions and low stack loss can bemaintained to provide excellent Short-Installation cycle - Combined-Cycle plants can be installed andoperated in less time than that requiredfor conventional steam plants. Again, thisis primarily due to the pre--engineeringand packaging of major components inthe factory. Phased installation of theplant, when gas turbines are installed andop-erated in the simple- cycle modeduring the steam- cycle equipmentinstallation, enables the user to generatepower and revenue in as little as a yearfrom order date (See Figures 2 4).

8 Atypical Combined-Cycle plant installationschedule is presented in Figure Development Evolution and FutureGE Power Systems GER-4206 (10/00)2 Figure 209E Combined-Cycle part load performance6. High Reliability/Availability- Highreliability operation results fromevolutionary design Development thatimproves parts and components, andquality manufacturing programs thatoffer operational factory testing. Highavailability is achieved throughdevelopment of sound operation andmaintenance practices, which resideprincipally with the user. Manufacturerexperi-ence and recommendations alsocontribute to this Low Operation and Maintenance Costs - Low operation and maintenanceCombined- cycle Development Evolution and FutureGE Power Systems GER-4206 (10/00)3 Figure MS7001B gas turbinesFigure STAG 407B Combined-Cycle steam system installationcosts are achieved through qualitydesign, prudent operation, andequipment design that allow convenientaccess for component High Efficiency in Small CapacityIncrements - Gas turbine generators aredesigned and manufactured in discreteframe sizes.

9 For example, the GeneralElectric heavy-duty, gas turbine -packagedpower plant product line includes theMS6001B (50 Hz and 60 Hz), MS7001 FA(60 Hz), MS7001B (60 Hz) and theMS9001 FA (50 Hz) units, which coveran output range of approximately 37MW to 250 MW. Application of these gasturbine models in combined -cycleCombined- cycle Development Evolution and FutureGE Power Systems GER-4206 (10/00)4 Figure STAG 407B combined cycleFigure project schedulesystems as single or multiple gas turbineand HRSG installations can provide fromabout 50 MW to several thousandmegawatts of power generation atessentially constant plant turbine combined -CycleDevelopmentThe commercial Development of combined -cy-cle systems has proceeded in parallel with gasturbine Development .

10 We are presently in thethird generation technology of combined -cyclesystems and are at the launch point of thefourth Generation Combined-Cycle Plants The first gas turbine installed in an electric util-ity in the United States was applied in a com-bined cycle . This was a MW gas turbine thatused the energy from the exhaust gas to heatfeedwater for a 35 MW conventional steam gas turbine is shown in Figure 6. A schemat-ic showing the Combined-Cycle system is shownin Figure 7. This system entered service in June1949, and a similar system was added to this sta-tion in 1952.