Original Article

Performance and sensitivity analysis of a combined cycle gas turbine power plant by various inlet air-cooling systems

Proc IMechE Part A: J Power and Energy 226(7) 922–931 ! IMechE 2012 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/0957650912456657 pia.sagepub.com

Murad A Rahim

Abstract This article is aimed at carrying out a performance analysis of a combined cycle gas turbine power plant with various inlet air-cooling systems. A comparison is performed using different cooling systems, including evaporative cooling, fogging, mechanical (electric) chiller cooling, and absorption cooling. A performance analysis is completed for each system. The performance characteristics are determined for a set of actual operational parameters including ambient conditions (temperature and relative humidity), turbine inlet temperature, pressure ratio, etc. To evaluate the net power output and efficiency for each system, a combined cycle unit system consisting of inlet air cooling system, gas turbine, dual pressure heat recovery steam generators, and steam turbine has been analyzed. The results show that power and efficiency improvements depend on ambient air temperature. In addition, by decreasing the ambient temperature and increasing the humidity of the air, the output power can be increased. The carbon dioxide emissions for each cooling system are also discussed. The results and the sensitivity analysis show that the absorption cooling system is most effective. Keywords Gas turbine cycle, combined cycle power plant, inlet air cooling, performance enhancement, sensitivity analyses Date received: 15 July 2011; accepted: 22 May 2012

Introduction The gas turbine engine (GT) is an important engine for use as a power source in many countries, and methods for increasing its output power and efficiency are an important research topic. In hot climate countries such as Turkey, inlet air cooling (IAC) is considered the most efficient and easiest method for increasing power output in simple gas turbine combined cycle (GTCC) power plants. Important considerations in current competitive environments are to maximize production, increase efficiency, and minimize unit costs. Almost all turbine-generator systems have a constant volumetric flow. During the summer, demand for electricity is increased due to cooling requirements. As a result, thermal comfort conditions are obtained by cooling the environment with cooling devices that consume large amounts of electricity. As ambient air temperatures increase, so does the work of a compressor. As a result, gas turbines are prone to decreased power output and efficiency. In a typical gas turbine engine, energy production capacity increases almost linearly,

while inlet air temperatures decrease; raising inlet air temperature from 15  C to 38  C causes a decrease in the capacity by 73%. Moreover, a decrease in inlet aircooling from 38  C to 15  C prevents loss of capacity by 27%. If the inlet air is cooled to 6  C, gas turbine power generation capacity increases to 110% of standard capacity. That is, if the inlet air is cooled from 38  C to 6  C, gas turbine power output capacity increases from 73% to 110%, representing an increase of approximately 40–50%. Thus, the cost of installing a gas turbine or a combined cycle plant rated at 38  C is 20–30% greater than that rated at 15  C. It has been shown that for every 1  C rise in ambient air temperature, gas turbine power output is reduced by 0.58%.1

Mechanical Engineering Department, Engineering Faculty, Gazi University, Turkey Corresponding author: Murad A Rahim, Mechanical Engineering Department, Engineering Faculty, Gazi University, Ankara, Turkey. Email: [email protected]

Rahim The rise of air inlet temperature from 15  C to 38  C increases heating rate. In this case, fuel efficiency leads to a decrease in the rate by about 4%. The decrease in the rate of fuel can be prevented by turbine inlet aircooling. The thermodynamic processes of a topping cycle can be approximately modeled as a Brayton cycle, in which the back work ratio is usually very high and the exhaust temperature is often above 500  C. A high exhaust temperature implies that there is plenty of useful energy wasted to the environment. The recovery of this otherwise wasted energy can be used to improve either power generation capacity and/or efficiency2–4 via modifications to the basic cycle such as steam injection,5 evaporation cycle,6 chemical recuperation,7 IAC,8 and combined cycle.9,10 The main advantages of inlet air cooling systems are: increased capacity; increased fuel efficiency; reduction of the main investment cost accordingly as capacity of output power generation unites; increased steam and power output from steam turbines and improved efficiency of combined cycle; improved pre-determined amount of power generation, which makes the turbine to operate at low inlet air temperature increasing life and lowering the maintenance costs. The disadvantages of the turbine inlet air cooling systems are additional initial investment cost and additional space requirements, requiring additional maintenance for the system, air heat exchanger (cooling coil) or evaporative media placed in the entrance leading to loss of pressure.12 In open literature, many researchers studied different cooling methods to enhance the performance of GT plants operating at high conditions of ambient temperature.13–22 A detailed study conducted by Hariri and Aghanajafi,13 appreciated several methods to improve gas turbine cycles. Inlet air cooling technology is one of them. They used two type of cooling systems: evaporating cooling and mechanical refrigeration cooling systems. It can be noted from their study that by using inlet air cooling system, the power output increase by 17.04%, but cycle efficiency decrease. Bhargava and Meher-Homji,14 have studied the effects of both inlet evaporative and overspray fogging on a wide range of combined cycle power plants utilizing gas turbines available from the major gas turbine manufacturers worldwide. A brief discussion on the thermodynamic considerations of inlet and overspray fogging including the effect of droplet dimension is also presented. Kakaras et al.15 used a computer simulation of the integration of an innovative technology for reducing the intake-air temperature in gas turbine plants. The simulation results analyzed two test cases: a simple cycle gas turbine and a combined cycle plant. First, the effect of ambient air temperature variation

923 on the power output and efficiency is presented for both cases. Farzaneh-Gord and DeymiDashtebayaz16 proposed a reversed Brayton refrigeration cycle for cooling the air intake for GT and improving the refinery gas turbines performance using the cooling capacity of the refinery natural-gas pressure drop station.17 They reported an increase in the output power up to 20%, but a 6% decrease in thermal efficiency. Alhazmy et al.18 analyzed a model to study the effect of inlet air-cooling on gas turbines power and efficiency is developed for two different cooling techniques, direct mechanical refrigeration, and an evaporative water spray cooler in hot and humid city (Jeddah, KSA). It can be noted from their studies that the direct mechanical refrigeration increased the daily power output by 6.77% and by 2.57% for the spray air-cooling. Cooling coils give a full control on the compressor inlet conditions; however, they consume considerable amount of power, causing a large drop in the overall plant performance and initial cost is higher than water spray systems. Ameri and Hejazi,19 conducted studies on Chabahar thermal power plant and analysis were performed for an absorption chiller, which was used for inlet air cooling. They showed that, 11.3% power enhancement is achieved and the payback period is estimated 4.2 years. Erdem and Sevilgen20 studied two models on seven different climatic conditions in Turkey and electricity production variations were studied according to climatic conditions. As a result an increase of 0.27– 10.28% in electricity generation was found. Yılmazog˘lu and Rahim21 examined the effects of the ambient conditions on gas turbine power plants. It is shown that increasing temperature and decreasing pressure badly affects the performance of the system. Dawoud et al.22 compared different inlet air cooling techniques at two different locations in Oman. The considered techniques were evaporative cooling, fogging cooling, absorption cooling using both LiBr–H2O and aqua-ammonia, and vapor-compression cooling systems. For evaporative cooling, an 88% approach to the wet-bulb temperature has been considered, compared with a 98% approach for fogging cooling. According to their results, fogging cooling is accompanied with 11.4% more electrical energy in comparison with evaporative cooling in both locations. The LiBr–H2O cooling offers 40% and 55% more energy than fogging cooling at Fahud and Marmul, respectively. On applying aqua-ammonia– water and vapor-compression cooling, a further annual energy production enhancement of 39% and 46% is expected in comparison with LiBr–H2O cooling at Fahud and Marmul, respectively. There are different methods for implementing inlet air-cooling. In this study, four methods were

924 examined: fogging, evaporative cooling, absorption cooling and electrical chiller cooling systems. All systems have advantages and disadvantages when compared to each other. For example, evaporative cooling and fogging systems have lower investment costs. Despite this, water is not abundant in hot climates. Absorption and mechanical compression system investment costs are higher than evaporative and fogging systems. Even so, electricity consumption is very high for mechanical cooling systems. The purpose of this study is to present a computer simulation of the integration of an innovative technology for reducing the intake-air temperature in gas turbine plants. The simulations are performed using ThermoFlex packet software. Following a description of the air-cooling systems, simulation results for six test cases without cooling systems are presented for a simple cycle gas turbine. First, the effect of ambient air temperature variation on the power output and efficiency is presented for all cases. Next, the results from the integration of the air-cooling system approaches are presented and discussed, demonstrating the gains in power output, efficiency, heat rate and fuel input that can be achieved.

Proc IMechE Part A: J Power and Energy 226(7)

System description and thermodynamic analyses A schematic diagram that describes the systems of a combined cycle gas turbine power plant is shown in Figure 1. As shown in Figure 1, ambient air at 20  C and 60% relative humidity is cooled in the inlet air cooler before it enters the axial flow compressor. Four methods for cooling ambient air for gas turbines are analyzed in this study. Evaporative cooling and fogging systems are used to cool the air with 85% and 95% effectiveness, respectively, but both are sensitive to the ambient relative humidity level. A typical single-stage absorption chiller is used to cool the chilling water using a LiBr solution as the working fluid. The chilling water is circulated between the absorption chiller and the air cooler by an electric pump. The air cooler in the absorption chiller reduces the temperature of the intake air to the compressor to 10  C independent of the ambient air temperature and relative humidity, and it supplies intake air to the compressor at a constant mass flow rate in hot conditions. The cooling water used by the absorption chiller releases heat to the ambient air via a cooling tower.4 Electrical chiller systems

Figure 1. General system description of a combined cycle gas turbine power plant with inlet air-cooling systems. C: compressor; CC: combustion chamber; GT: gas turbine; BPS: by pass stack; HRSG: heat recovery steam generator; HPS: high pressure steam; LPS: low pressure steam; ST: steam turbine; D: de-aerator; FWP: feed water pump; COND: condenser; CT: cooling tower.

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are also independent of the inlet air wet bulb temperature and can reduce the inlet air temperature to a minimum of 8  C. By decreasing the inlet air temperature and increasing its mass flow rate, compressor work decreases, and the power output level for the gas turbine cycle can be increased. Compressed gas at 19.16 bar and 435.3  C with compressor discharge ratio 12, enters the combustion chamber. In the present study, the fuel is assumed to be natural gas (CH4 ¼ 87%, LHV ¼ 46286 kJ/kg) and its temperature increases to 1150  C as the hot gas expands in the turbine. At a turbine pressure ratio of 18, the power output of the gas turbine without an inlet air cooling system is 75.26 MW. The expanded gas flows out of the turbine at 480.8  C and enters the heat recovery steam generator. The power formulation for a gas turbine is given in equation (1). To increase the power output of a turbine, the compressor specific work should be decreased or inlet airflow should be increased. In equation (1), mG is the combustion gas flow rate; m, the mechanical efficiency; and G, the generator efficiency. wGT and wC are the specific powers of the gas turbine and compressor, respectively PelGT ¼" mG ðwGT  # wC ÞM G

ð1Þ

Here, mG ¼ mair þ mfuel Compressor specific work can be defined as shown in equation (2). To decrease the specific work of the compressor, and thereby, increase the net power of the gas turbine, the inlet air temperature should be decreased 1 # wC ¼ cp # TC,i : " C

" #  pC,e 1= 1 pC,i

ð2Þ

Here, cp is the specific heat; p, pressure; T, temperature, the subscripts i and e stand for inlet and exit. The efficiency of a gas turbine cycle is given in equation (3), which shows that the net power of a gas turbine cycle combined with the industrial heat recovered is directly proportional to the overall efficiency GT ¼

PelGT þ QIH mf :Hu

ð3Þ

where QIH is the industrial heat and Hu is the lower heating value of the fuel. To calculate the pressure ratio in a gas turbine, we use the following ð1=Þ

PR

  pC,e ð1=Þ TC,eS Tt,i ¼ ¼ ¼ pC,i TC,i Tt,eS

ð4Þ

where TC,eS and Tt,eS, correspond to isentropic processes, the subscripts C and t stand for compressor and turbine and PR is the pressure ratio. We can determine TC,e in terms of PR as shown below  ð1=Þ  TC,e PR 1 ¼ þ1 C TC,i

ð5Þ

where C is the compressor isentropic efficiency. The isentropic efficiencies of an adiabatic turbine and a compressor can be given, respectively, as turb ¼

wa hi  he ¼ ws hi  he,s

comp ¼

ws he,s  hi ¼ wa he  hi

ð6Þ

ð7Þ

where wa and ws are the actual and isentropic works, respectively.

Cooling methods for gas turbine inlet air The general premise for this study is that in the summer season, when the electric power demand increases, inlet air-cooling is probably the most frequently used method to increase gas turbine output power. Cooling the inlet air for a constant-volume machine such as a gas turbine has the advantage that the mass flow rate for cool air is higher than that for warm air. A 1  C decrease in the inlet dry bulb air temperature increases the combinedcycle output by about 2.7%. In combined-cycle applications, the cooler input air also results in a small increase in thermal efficiency.7 Several methods can be adopted to achieve inlet air-cooling.

Evaporative cooling systems In an evaporative cooling system, the inlet air is exposed to a film of water in one of the many types of wetted media. The water used for wetting the medium may require treatment, depending upon the quality of water and the medium manufacturer’s specifications (Figure 2). Evaporative cooling can cool the inlet air by as much as 85% to 95% of the difference between the ambient dry bulb and wet bulb temperatures. The main advantages of this system are the low capital and operation & maintained (O&M) costs, and quick delivery and installation times; moreover, the wetted media operates as an air washer and cleans the inlet air. However, there are some disadvantages, such as limitations on potential capacity improvements and ineffectiveness at high wet bulb temperatures. The theoretical minimum air temperature that can be obtained by evaporative inlet air-cooling is equal to

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Figure 2. Schematic diagram of inlet air cooling with evaporative cooling system.

the ambient wet bulb temperature. This means that it may be difficult to achieve the desired standoff temperature. The actual temperature drop is a function of both equipment design and atmospheric conditions. The actual temperature drop can be calculated by the following expression T ¼ 0:95ðTDB  TWB Þ

ð8Þ

Figure 3. Schematic diagram of inlet air cooling system by fogging.

Figure 4. Schematic diagram of inlet air cooling system with mechanical (electrical) chiller cooling system.

where DB and WB refers to dry bulb and wet bulb, respectively.

and installation times. The disadvantages listed for evaporative cooling also apply to fogging systems.

Fogging

Mechanical chillers

Figure 3 shows a schematic diagram of an inlet air cooling system that utilizes a fogging system. Evaporative fogging systems are designed to inject more spray water into the inlet air stream than can be evaporated at the given ambient temperature. The droplets flow into the compressor, where the hot air completes their evaporation. By decreasing the temperature of inlet air for a compressor, the total mass of the air increases and as the water evaporates, the relative work required for compression is reduced. This results in both higher turbine output and higher efficiency. A fogging system can be equipped with overspray or under spray.2 The relative work of compression can be calculated as follows

The primary objective is to cool the compressor inlet air, and thereby, increase its mass. A cooling system with a mechanical (electrical) chiller can cool the inlet air to much lower temperatures than those possible by evaporative cooling and can maintain the desired inlet air temperature down to as low as 8  C (Figure 4), independent of the ambient wet-bulb temperature. In this study, a typical compact electrical chiller with a coefficient of performance (COP) of 3 was used to cool the ambient air. A cooling coil through which a chilled medium circulates was installed in the inlet air stream. Mechanical refrigeration requires a high level of auxiliary power consumption to drive the compressor; this is a drawback during periods when the electricity demand reaches its maximum.2 The advantages of a mechanical refrigeration system are that it can maintain the inlet air at much lower temperatures than those possible by other technologies and it achieves the desired temperatures independent of weather or climate conditions. The primary disadvantages of this type of system are that it is capital cost intensive and it has higher parasitic loads (typically 0.70–0.81 kW/RT) that lead to higher overall heat rates than those in the case of evaporative cooling technologies.2

:

:

C

A

:

:

W ¼ ðm þ mH2 O Þ  w

ð9Þ

C

To cool the inlet air effectively, the quality of the water used in the fogging system must be controlled. The pH should be between 6 and 8. The total dissolved solid content should be less than 5 ppm; the sodium and calcium content – less than 0.1 ppm; and silica content – less than 0.1 ppm; chloride and sulphate content – less than 0.5 ppm. The main advantages of fogging systems are low capital and O&M costs, improved gas turbine performance compared to the performance achieved by evaporative cooling, and quick delivery

Absorption cooling systems There are two types of chillers, namely, direct chillers and thermal storage chillers. In this study, direct

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Figure 5. Schematic diagram of inlet air cooling system with single effect absorption cooling system.

chillers, i.e. mechanical or absorption chillers, are used to cool the inlet air. Direct chillers can produce chilling instantaneously. Absorption cooling systems are similar to mechanical refrigeration systems except that instead of using mechanical means, they use absorption chillers that use thermal energy (steam or hot water) as the primary source of energy and require much less electric energy than mechanical chillers. In Figure 5, a schematic diagram of an inlet air cooling system with a typical single-effect absorption cooling system is shown. An absorption cooling system with a COP of 0.67 can be used to cool the inlet air to about 10  C. The main advantages of these systems are as follows: (1) they can increase gas turbine performance to values higher than those achieved using evaporative cooling and fog systems and (2) they have much less parasitic load compared to the other systems. However, the absorption cooling systems also have some disadvantages such as high initial capital cost, high O&M costs, and longer delivery and installation times; further, expertise is necessary to operate and maintain the plant.

Results Table 1 clearly lists the net power output, net electric efficiency, net fuel input, and heat rate in the case of a turbine without an inlet air cooling system; the improvement achieved in these parameters by using various cooling systems such as evaporative, fogging, electrical chiller, and absorption-cooling systems can also be seen from the table. Table 1 shows that turbine output power and net electric efficiency increase upon the use of inlet air cooling systems. By using evaporative cooling and fogging systems in hot climates, the mass flow rate of the inlet air increases even under conditions of 100% relative humidity, depending on the ambient air temperature and humidity. At the same time, by using an absorption or electrical chiller cooling system, the mass flow rate of inlet air is fixed at a constant value and is independent of the ambient air temperature and humidity. The COPs of the electrical and absorption chillers used to

927 cool the ambient air are 3 and 0.67, respectively. As listed in Table 1, the power output from the gas turbine increases by 1.70% and the efficiency increases by 0.11% if an evaporative cooling system with an effectiveness of 85% is installed. The gas turbine output power and efficiency increase by 1.90% and 0.11%, respectively, when a fogging system with an effectiveness of 95% is used. If an electrical chiller cools the inlet air to 8  C, the power output of the gas turbine cycle increases by 3.81%, but the net electrical efficiency decreases by 0.85%. Finally, when an absorption cooling system is used to cool the inlet air down to 10  C, the power generated by the gas turbine cycle increases by 3.48% and the net electrical efficiency increases by 0.05%. One of the main factors affecting the performance of a gas turbine cycle is compressor work, as seen in Figure 6. Above 20  C, an absorption chiller cooling system is the best solution if increasing the net power generation is the main aim. If the ambient air temperature is less than 20  C, inlet air cooling with absorption chillers adversely affects net power production because steam consumption necessary in order to satisfy the cooling requirement. In Figure 7, the net electric efficiency curves with respect to the ambient air temperature for various inlet air-cooling systems are shown. The cooling system decreases the temperature of inlet air entering the compressor, therefore, the amount of inlet air passed to the combustion chamber decreases and fuel consumption increases. Hence, the cycle efficiency of a gas turbine cycle with an inlet air cooling system will decrease. The effect of the pressure ratio on the net work output of a combined-cycle power plant with a gas turbine inlet temperature of 1150  C for the four types of inlet air cooling systems is shown in Figure 8. With an increase in the pressure ratio, the gas turbine cycle power also increases, but this occurs at a decreasing rate. This is because the work demand of the air compressor increases as the pressure ratio increases. In the case of the steam cycle, the pressure ratio has the opposite effect. The gas turbine cycle net work, being higher in magnitude than the steam cycle net work, has a dominant impact on net work output of the combined-cycle power plant. However, this net work output increases to an optimum value, beyond which the decrease in steam cycle work output and the increasing work demand of the air compressor cause the combined-cycle net power output to drop at higher pressure ratios. Figure 9 shows that the overall combined-cycle power plant efficiency increases as the overall pressure ratio increases; however, this occurs at a decreasing rate. It also shows that the best performance for the

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Proc IMechE Part A: J Power and Energy 226(7)

Table 1. Main specifications design of a combined cycle gas turbine power plant. Parameters

Units

Without cooling

Evaporative cooling

Fogging

Absorption cooling

Electrical chiller

Net Net Net Net

MW % kJ/kWh MW

96.027 53.50 6729 179.485

97.697 53.56 6721 182.404

97.891 53.56 6721 182.753

99.497 53.53 6725 185.870

99.839 53.04 6788 188.251

power electric efficiency (LHV) heat rate(LHV) fuel input (LHV)

Figure 6. Effect of ambient air temperature on the combined cycle net power output. IAC: inlet air cooling.

Figure 8. Effect of pressure ratio on combined cycle power plant net power output. IAC: inlet air cooling.

Figure 7. Effect of ambient air temperature on the net electric efficiency of the combined cycle power plant. IAC: inlet air cooling.

Figure 9. Effect of pressure ratio on combined cycle power plant net electric efficiency. IAC: inlet air cooling.

combined cycle corresponds to pressure ratios between 18 and 20. The effect of the gas turbine inlet air temperature on the combined-cycle net power for the various inlet aircooling systems is shown in Figure 10. For a pressure

ratio of 18, an increase in the gas turbine inlet temperature results in a continuous increase in the net power output for a combined-cycle power plant. For a fixed total mass flow rate through the gas turbine, the optimum pressure ratio for producing maximum work

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Figure 10. Effect of gas turbine inlet temperature on the combined cycle power plant net power output. IAC: inlet air cooling.

Figure 11. Effect of gas turbine inlet temperature on the combined cycle power plant net electric efficiency. IAC: inlet air cooling.

output increases for higher gas turbine inlet temperatures. Figure 11 shows the effect of gas turbine inlet temperature on the combined-cycle power plant net electrical efficiency. The thermal efficiency increases as the gas turbine inlet temperature is increased. The effect of pressure ratio on annual carbon dioxide emissions released to the environment by plants equipped with different inlet air cooling systems is shown in Figure 12. Carbon dioxide emission levels, measured in tons per year, decrease at higher overall pressure ratios. One of factors that led to a reduction in the amount of carbon dioxide emitted is a significant change in the combined-cycle power plant net work output. The bulk of the net work output from the

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Figure 12. Effect of the design point overall pressure ratio on the combined cycle power plant CO2 emissions. IAC: inlet air cooling.

Figure 13. Effect of ambient air temperature on the combined cycle power plant net heat rate. IAC: inlet air cooling.

combined-cycle power plant is generated by the gas turbine cycle. Hence, any enhancement in the gas turbine cycle performance will result in a substantial increase in net work output. Thus, increasing the amount of combustion mixture that passes though the gas turbine in order to improve its work output can be accomplished by installing an inlet air cooling system to decrease the compressor specific work. Improvement in sensible heat rates is associated with decreasing dry bulb temperatures. The effect of ambient air temperature on the combined-cycle net heat rate per kilowatt hour is plotted in Figure 13, which clearly shows that the heat rate improves as the compressor inlet temperature decreases. Reducing the heat rate of a power plant is an effective way of reducing fuel consumption, and thus, CO2 emissions.

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Conclusion Inlet air cooling systems are useful tools for increasing the net power generation capabilities of gas turbine power plants, especially in hot climates. Reducing the inlet air temperature to the gas turbine increases the mass flow rate and enhances its net output power and efficiency. In this study, four inlet air-cooling systems are simulated and system performance data are analyzed for each system with respect to ambient air temperature, pressure ratio, and gas turbine inlet air temperature. A power plant without inlet air-cooling is also modeled for comparison with the plants equipped with inlet air cooling systems. Fogging and evaporative cooling systems are considered as two options to provide chilled air to the inlet of the compressor. In the case of these systems, the ambient wet bulb temperature acts as a limit of their cooling capacity; hence, the relative humidity of the ambient air is assumed to be constant. The availability and quality of the water sources near the power plant are the main obstacles for foggers. An absorption cooling system can chill the compressor inlet air to a temperature below the wet bulb temperature. Absorption chillers use bled steam to provide the energy needed to cool the inlet air. However, the net electric efficiency of the plant decreases sharply when the ambient air temperature reaches 20  C because of the increased cooling load for the inlet air. Electric (mechanical) chiller systems are used to chill water, which in turn cools the compressor inlet air. In hot climates, both absorption and mechanical chillers can cool the inlet air temperature to the desired level, independent of the ambient temperature and humidity. If the main aim is to increase net power generation, absorption chillers are the best solution. The results indicate that a thermoeconomic optimization problem occurs. Hence, economic and source audits should be performed before deciding the type of the inlet air cooling system to be installed. Funding This work was supported by the Gazi University Energy – Envronmental Systems and Industrial Rehabilitation Research Center.

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Appendix Notation cp h Hu m_ p

specific heat (kJ/kg  C) enthapy (kJ/kg) lower heating value (kJ/kg) mass flow rate (kg/s) pressure (bar)

PelGT PR Q_ T w

gas turbine power output (MW) pressure ratio net heat (MW) temperature ( C) specific work (kJ/kg)



efficiency (%)