ARTICLE / MAKALE Fora typical gas turbine, an increase of inlet air temperature from 15°C to 38°C decreases (lower output to about 73% of its rated capacity. This could lead to a loss of opportunity for power producers to seli more power at precisely the time when the rise in ambient temperature increases power demand for operating air conditioners. Conversely, cooling inlet air from 38°C to 15°C prevents the loss of 27% of the rated generation capacity. lf the inlet air is cooled to 6°C, the power generation capacity of the gas turbine will be increased to 110% of the rated capacity. Thus, if the inlet air is cooled from 38°C to 6°C. the power output ofa gas turbine would be increased from 73% to 110% of the rated capacity, in a boost of about 50% - see Figure 2. BENEFITS OF TURBINE AIR iNLET COOLING The main benefit of turbine air inlet cooling is !hat it helps to optimize usage of gas turbine assets in new or existing simple-cycle, cogeneration and combined-cycle systems. When the ambient temperature of air is above 15°C, the benefits of turbine inlet air cooling include: O increased power output O reduced capital cost per unit of power plant output capacity O increased fuel efficiency O increased steam output in cogeneration systems O increased power output of steam turbines in combinedcycle systems O improved predictability of power output by eliminating the weather variable. lncreased power output The primary benefit of turbine air inlet cooling is that it allows plant owners to reduce or prevent loss of gas turbine power output, compared to the rated capacity, when the ambient temperature is above 15°C. Turbine air inlet cooling can also allow plant owners to increase the gas turbine output above the rated capacity by cooling the inlet air to below 15°C. "°E- 120 ·u "' CL "' u v ~ 110 ~ 100 ~ :::, B- :::, o cii :: ~ 90 80 70 ı, . . ...... ~ ••••·· . 5 10 ~ ... ~ --.. ••••· ........ " •••••· ·· ............ 15 20 25 30 35 inlet air tenıperature (°Cl Aeroderivative ••••, lrı dustria l Figııre 2. Oııtpııt of gas ıurbines - ejfecı of ambienı ıeıııperatııre Reduced capital cost per unit of output capacity lf a power producer does not apply turbine air inlet cooling, but wants or needs to make up for the lost capacity due to an increase in the ambient temperature, the only available option is to install another gas turbine or another type of generator, and bring it on-line to make up for the lost capacity. lnstalling another gas turbine asa peaking turbine is usually more expensive than using turbine air inlet cooling on the original gas turbine system. lncreased fuel efficiency A significant secondary, benefit of turbine air inlet cooling is that it reduces or prevents a decrease of fuel efficiency of the gas turbine, compared to the design efficiency or heat rate, when the ambient temperature rises above 15°C. An increase in inlet air temperature from 15°C to 38°C increases the heal rate, which causes a decrease in fuel efficiency of about 4%. Turbine air inlet cooling can avoid !his. and can even help increase fuel efficiency by cooling the inlet air to below 15°C. For a typical gas turbine, cooling the inlet air from 15°C to 6°C reduces the heat rate, and increases fuel efficiency by about 2%. Figure 3 shows the effect of inlet air temperature on heat rale (fuel required per unit of electric energy) for industrial and aeroderivative gas turbines. lncreased steam and steam turbine power output in addition to reducing or preventing the loss of gas turbine power output, turbine air inlet cooling also reduces or prevents the loss of steam produced in cogeneration systems and the loss of power output of steam turbines in combined-cycle systems when the ambient air temperature rises above 15°C. The power output ofa gas turbine falls with a rise in the ambient temperature because the mass flow rate of the inlet air decreases. This decreased mass flow rate also results in decreased total energy in the gas turbine exhaust gases, which in turn leads to reduced steam production in the heat recovery steam generators (HRSGs). The reduced steam generation in the HRSGs results in lower output of steam turbines in combined-cycle systems. "' <I! .c 00 C ~ 100 1----t--:--;,~~~--t----+---+---ı ı ~ ~ ~ :o (l) I 96 ,____...___...___...___ ..L-__ ..J-_ __,J 5 10 15 20 25 inlet air tenıperature (°C) Aeroderivative 30 lndustrial Figııre 3. Gas ıurbine /ıeat raıe - ejfect of aıııbienı ıemperaıııre 35 60 1 ENERJi & KOJENERASYON DÜNYASI ♦ - -+=====~~;;;;;;;;;;;;;,,::_:__:~,;;,;,,- ======"""'"""'"""'"""""'"""= "Kojenerasyon: Yüksek Verim, Temiz Çevre, Ene~ide Yeniden Yapılanma"
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