-
y-
S.Er Osmir, Tu
Keywords:Exergy analysisAdvanced exergetic analysisExergy
destructionElectricity generation facility
erfoin T
namely endogenous, exogenous, avoidable and unavoidable exergy
destruction rates. Through this anal-
essor,
generation facilities in industry. CHP facilities produce
electricityand heat energy from one type of fuel, generally natural
gas. Theefciency of such a facility can reach 7080% [1]. In
addition tothe economic and efciency benets, their environmental
impactis an important factor. Gas turbines have low greenhouse gas
emis-sions compared to many other power generation systems.
and they do notnt affects one an-hrough ad
There are a few studies on advanced exergy-based
analpower-generating systems in the open literature [315]. Tsnis
[3] discussed the weaknesses of conventional exergyanalyses in
developing improvement strategies and presented ad-vanced exergy,
advanced exergoeconomic and exergoenvironmen-tal analyses as
solutions to these weaknesses. Tsatsaronis andMoung-Ho [4] were the
rst to develop the concepts of avoidableand unavoidable exergy
destruction, which were used to deter-mine the potential of
improving the thermodynamic performanceand cost effectiveness of a
system. Cziesla et al. [5] investigated
Corresponding author. Tel.: +90 (228) 2160061; fax: +90 (228)
216 05 88.E-mail addresses: [email protected],
[email protected]
(E. Akkalp).
Energy Conversion and Management 82 (2014) 146153
Contents lists availab
Energy Conversion
seUnfortunately, gas turbines also have disadvantages. Gas
turbinemaintenance costs are high, they are sensitive to ambient
condi-tions, and they are sensitive to electricity voltage change.
Gas tur-bines are primarily used in combined heat and power
(CHP)
improvement of the system or its components,provide any
information about how one componeother. This lack of information
can be addressed texergy-based methods
[2,3].http://dx.doi.org/10.1016/j.enconman.2014.03.0060196-8904/
2014 Elsevier Ltd. All rights reserved.vanced
yses ofatsaro--basedand a turbine while they have been widely
used in the industryand transportation sectors. For example, they
are used in energyproduction facilities, aircrafts, transport
ships, and even cars andmotorcycles. Gas turbines have some
particular advantages, suchas low annual cost, fast activation,
exible operation, and fastand easy maintenance. In addition, the
most important advantageof gas turbines is that their efciency is
high (approximately 40%).
assessing the performance of energy conversion systems. Exergyis
the maximum work that can be obtained from a system. Exer-gy-based
analyses help determine the irreversibilities (entropygeneration)
and how a source can be used effectively. However,exergy-based
analyses lack some information, which will be dis-cussed in Section
3.2 in more detail. Basically, the results of anexergy-based
analysis cannot be used to consider the potential1.
Introduction
Gas turbines consist of a comprysis, the improvement potentials
of both the components and the overall system along with the
interac-tions between the components are deducted based on the
actual operational data. The analysis indicatesthat the combustion
chamber, the high pressure steam turbine and the condenser have
high improve-ment potentials. The relations between the components
are weak because of the ratio of the endogenousexergy rates of 70%.
The improvement potential of the system is 38%. It may be concluded
that one shouldfocus on the gas turbine and combustion chamber for
improving the system, being the most importantcomponents of the
system.
2014 Elsevier Ltd. All rights reserved.
a combustion chamber
All energy conversion systems must be analyzed in terms
ofenergetic, economic, and environmental aspects for a proper
man-agement. Exergy-based analyses are very convenient methods
forAccepted 1 March 2014Available online 27 March 2014
system is determined to be 40.2% while the total exergy
destruction rate of the system is calculated to be78.242 MW. The
exergy destruction rate within the facilitys components is divided
into four parts,Advanced exergy analysis of an electricitusing
natural gas
Emin Akkalp a,, Haydar Aras b, Arif Hepbasli caDepartment of
Mechanical and Manufacturing Engineering, Engineering Faculty,
BilecikbDepartment of Mechanical Engineering, Engineering and
Architecture Faculty, EskisehicDepartment of Energy Systems
Engineering, Engineering Faculty, Yasar University, Izm
a r t i c l e i n f o
Article history:Received 5 December 2013
a b s t r a c t
This paper deals with the pisehir Industry Estate Zone
journal homepage: www.elgenerating facility
. University, Bilecik, Turkeyangazi University, Eskisehir,
Turkeyrkey
rmance assessment of an electricity generation facility located
in the Esk-urkey using advanced exergy analysis method. The exergy
efciency of the
le at ScienceDirect
and Management
vier .com/locate /enconman
-
(HRSG), a high pressure steam turbine (HPST), a low pressure
Subscripts
EN endogenousEX exogenous
u exergetic efciency (%)
n anall of an externally red combined power plants
componentsaccording to both avoidable and unavoidable exergy
destruction;the associated costs were dened, and the results of
their studywere discussed. Kelly et al. [6] dened the exogenous and
endoge-nous exergy destructions that determine the interactions
betweencomponents, and they were the rst to submit the
calculationmethod they presented. The calculations were expressed
using asimple refrigeration cycle and a simple gas turbine cycle.
Razmaraand Saray [7] investigated the destruction of exogenous
andendogenous exergy by the engineering method for a simple
gasturbine cycle operating using different fuels. The
irreversibilitiesobserved in the components were described and
compared forthese fuels. Morosuk and Tsatsaronis [8] applied
advanced exergyanalysis to a simple gas turbine cycle to assess its
performanceand discussed their calculation methods in detail.
Tsatsaronis andMorosuk [9] performed advanced exergy analysis of a
natural gasliquefaction plant using a three-stage refrigeration
cycle. They de-ned the improvement potentials and interactions
between thecomponents. Morosuk et al. [10] analyzed a natural gas
degasica-
Nomenclature
_E exergy rate (MW)_m mass ow rate (kg/s)P pressure (kPa)T
temperature (K)y exergy destruction ratio
AbbreviationsAC air compressorCC combustion chamberCOND
condenserGT gas turbineHPST high pressure steam turbineHRSG heat
recovery steam generatorLPST low pressure steam generator
E. Akkalp et al. / Energy Conversiotion plant that produced
electricity using advanced exergy and ad-vanced exergoenvironmental
methods. They concluded that theexpander II, the heat exchanger II
and the pump deserved the mostattention in improving the
thermodynamic efciency and reducingthe environmental impact of the
plant. Wang et al. [11] analyzed apower plant operating under
supercritical conditions using ad-vanced exergy analysis and
proposed suitable optimization strate-gies. They recommend that the
generator be improved rst,followed by the turbines. Petrakopoulou
et al. [12] studied a com-bined power plant using advanced exergy
and conventional analy-ses and demonstrated the superiority of the
former. They reportedthat an advanced exergy analysis provided a
wide range of optimi-zation strategies and potential improvements.
Petrakopoulou et al.[13] applied advanced exergy and advanced
exergoenvironmentalanalysis methods to a combined power plant. They
determinedthat 68% of the environmental impact of the system was
unavoid-able. In Refs. [14,15], an advanced exergoeconomic analysis
wasapplied to a combined (CHP) system and oxy-fuel power plant
withCO2 capture, and the methodology employed to conduct
advancedexergoeconomic analysis was explained in a detailed
manner.
In the present paper, an advanced exergy analysis method is
ap-plied to an electricity-generating facility using natural gas.
Thus,the actual potential improvements of the system and the
relation-ships between the components are determined, and possible
sug-gestions towards increasing the system efciency are
provided.steam turbine (LPST) and a condenser (COND).
Approximately37 MW of electricity is generated by the system, but
the processsteam cannot be used because of the chemicals included
in thesteam. A 45.07 air/fuel ratio combustion equation for natural
gasis as follows [1619]:
0:9334CH4 0:00211C2H6 0:00029C3H8 0:00012C4H10 0:06408N2
26:51870:7748N2 0:2059O2 0:0003CO2 0:01H2O! 0:9469CO2 2:3800H2O
3:5831O2 20:8671N2 12. System description
The electricity-generating facility using natural gas is shown
inFig. 1. This system is located in the Eskisehir Industry Estate
Zone,Turkey. The system consists of a compressor (AC), a
combustionchamber (CC), a gas turbine (GT), a heat recovery steam
generatorUN unavoidable
Greek lettersg isentropic/energetic efciency (%)D destructionF
fuelk kth componentL lossP producttot total
SuperscriptsAV availabled Management 82 (2014) 146153 147The
specic heat of the combustion gas and the air can becalculated from
Eqs. (2) and (3), respectively [1619]:
cP;gasT 0:935301 0:010577102
T 0:017218105
T2
0:072386109
T3 2
cP;airT 1:04841 0:000383719T 9:45378107
T2
5:490311010
T3 7:929811014
T4 3
The lower heating value of the natural gas, the gas constant
ofthe combustion gas and the gas constant of air are 44661
kJ/kg,0.2947 kJ/kg K and 0.2870 kJ/kg K, respectively, and the
specicexergy of natural gas (CaHb) is calculated as follows
[20]:
ech;FLHV
kF 1:033 0:0169 ba0:0698
a4
where kF is 1.0308. The xed parameters of the system are listed
inTable 1.
-
the investigated system.
Table 2Mass ow rates, pressures, temperatures, energy rates and
exergy rates for theelectricity facility using natural gas.
Point Fluid _m (kg/s) T (K) P (kPa) _E (MW)
anFig. 1. Schematic of
Table 1Fixed parameters of the electricity facility using
natural gas.
Parameter Unit Value
_WAC MW 51.082
148 E. Akkalp et al. / Energy Conversion3. Analyses done
3.1. Conventional exergy analysis
The main equations for the exergy analysis of the kth compo-nent
and the overall system are the same [6,21], but there is
onedifference associated with the treatment of the exergy losses:
Itis assumed that the system boundaries used for all exergy
balancesare at the temperature T0 of the reference environment, and
there-fore, there are no exergy loses associated with the kth
component[6,22]. Exergy losses appear only at the level of the
overall system[6]. The exergy destruction rate can be calculated as
follows [21]:
_ED _EF _EP 5The exergetic efciency is [21]:
/ _EF_EP
or / 1_ED_EF
6
The exergy destruction ratio is a ratio of the component
exergydestruction rate to the total exergetic fuel rate [21]:
yk _ED;k_EF;tot
7
For the overall system [21]:
_EF;tot _EP Xk
_ED;k _EL 8
where _EL is the rate of exergy loss of the system or control
volumeto the environment, which can no longer be used. The
properties at
_WGT MW 85.183_WHPST MW 10.278_WLPST MW 4.394
gAC 0.790gGT 0.730gHPST 0.890gLPST 0.370d Management 82 (2014)
146153various locations and the results of the conventional exergy
analysisof the system are described in Tables 2 and 3,
respectively.
3.2. Advanced exergetic analysis
3.2.1. Unavoidable and avoidable exergy destructionsThe
inefciencies of a thermal cycle are caused by exergy
destruction (entropy generation or irreversibilities). Part of
theexergy destruction is avoidable, while part of it is not. The
unavoid-able exergy destruction rate _EUND;k results from
technological and
1 Air 138.00 284.15 101.32 0.0462 Air 138.00 621.15 1045.00
42.6483 Fuel 2.59 298.15 2292.00 121.3024 Combustion gas 140.59
1311.15 992.75 125.1425 Combustion gas 140.59 811.15 112.00 34.3006
Combustion gas 140.59 398.15 103.20 2.1627 Water 16.39 353.15
6850.00 0.4208 Water 3.82 351.15 560.00 0.0699 Water 16.39 772.15
6500.00 22.634
10 Water 3.82 468.15 510.00 2.87911 Water 16.39 438.15 395.00
11.46912 Water 20.21 443.15 420.00 14.36713 Water 20.21 315.65 8.50
2.75314 Water 20.21 309.15 8.20 0.01515 Water 722.23 298.15 300.00
0.13016 Water 722.23 309.15 285.00 1.206
Table 3Exergetic parameters of the electricity facility using
natural gas.
Component _EF (MW) _EP (MW) _ED (MW) / y
AC 51.082 42.602 8.480 0.840 0.030GT 90.846 85.183 5.663 0.940
0.020CC 121.302 73.982 47.32 0.610 0.150HRSG 32.034 25.024 7.010
0.780 0.020HPST 11.165 10.278 0.887 0.920 0.003LPST 11.614 4.394
7.220 0.380 0.020COND 2.738 1.076 1.662 0.390 0.005
-
economic limitations and cannot be improved. The avoidable
partof the exergy destruction rate _EAVD;k is the remaining part of
theexergy destruction rate and represents the improvement
potentialof the component.
For calculating the unavoidable exergy destruction, each
com-ponent is considered in isolation and separated from the
system.The ratio of the exergy destruction per unit of product
exergy _ED_EP
UN
kis calculated assuming operation with high efciency and
low losses. Equations used for calculating avoidable and
unavoid-able exergy destruction rates can be seen in Fig. 2. In
addition,these equations can be listed as follows:
Unavoidable exergy destruction rate is:
_EUND;k _EP;k_ED;k_EP;k
!UN9
Avoidable exergy destruction rate is:
veals the effects of the system on the considered component
seen in Fig. 2.
_EAV ;END;k _EEND;k _EUN;END;k 15
_EAV ;EXD;k _EAVD;k _EAV ;END;k 16
4. Results and discussion
According to the conventional exergy analysis,
thermodynami-cally, the most important component seems to be the
combustionchamber because of exhibiting the maximum exergy
destructionrate of the system components (47.32 MW). Exergy
destruction ismeasure for the irrevesibilities in a system. As
expected, that thehighest exergy destruction rate is at the CC
because chemical reac-tions cause irreversibilities highly.
Therefore, one should focus onthe improvement of the CC. Increasing
the airfuel mass ratiocan cause decreasing the exergy destruction
rates. The minimumexergy destruction rate is due to the HPST (0.887
MW). Similarly,
E. Akkalp et al. / Energy Conversion an[23]. Equations used for
calculating endogenous and exogenousexergy destruction rates can be
seen in Fig. 3._EAVD;k _ED;k _EUND;k 10
3.2.2. Destruction of endogenous and exogenous exergyThe
destruction of endogenous _EEND and exogenous _EEXD exer-
gy are used to determine relationships between the components
ofthe investigated system. Endogenous exergy destruction is
theexergy destruction that occurs in the component itself.
Exogenousexergy destruction is the exergy destruction caused by the
othercomponents. The endogenous part of the exergy destruction
isassociated only with the irreversibilities occurring within the
kthcomponent when the following two conditions are
simultaneouslyfullled:
All other components operate in an ideal manner. The component
being considered operates with its current ef-ciency [2,3].
The exogenous part of the exergy destruction rate is
calculatedby subtracting the endogenous exergy destruction rate
from thereal exergy destruction rate. The exogenous exergy
destruction ofa component can be divided as _EEX;nD;k , which
represents the effectsof the nth component on the irreversibilities
on the kth compo-nent. The difference between the sum of all the
_EEX;nD;k terms andthe overall exogenous exergy destruction rate is
described as mex-ogenous exergy destruction. Mexogenous exergy
destruction re-Fig. 2. Dividing exergy destruction rate to
avoidable and unavoidable parts [2].Unavoidable endogenous,
unavoidable exogenous, avoidableendogenous and avoidable exogenous
destruction rates, respec-tively, are:
_EUN;END;k _EENP;k_ED;k_EP;k
!UN13
_EUN;EXD;k _EUND;k _EUN;END;k 14Exogenous exergy destruction
rate is:
_EEXD;k _ED;k _EEND;k 11Mexogenous exergy destruction rate
is;
_EMEXD;k _EEXD;k Xj1r1rk
_EEX;nD;k 12
3.2.3. Splitting unavoidable and avoidable exergy destructionThe
unavoidable endogenous exergy destruction rate _EUN;END;k ,
the unavoidable exogenous exergy destruction rate _EUN;EXD;k ,
theavoidable endogenous exergy destruction rate _EAV ;END;k and
theavoidable exogenous exergy destruction rate _EAV ;EXD;k are can
be
Fig. 3. Dividing exergy destruction rate into endogenous and
exogenous parts [2].d Management 82 (2014) 146153 149the maximum
exergy efciency is due to the GT (0.92), while theminimum efciency
is obtained for the LPST (0.38). This meansthat the efciency of the
GT is the closest to the efciency of Car-
-
not, while the LPST is far away from it. Exergy destruction
ratio isanother parameter to evaluate the system performance. It
repre-sents the ratio of the exergy destruction rate to the total
fuel exer-gy ratio. The exergy destruction rates of the other
components, theexergy efciencies and the exergy destruction ratios
are listed inTable 3. In addition, the magnitudes of the exergy
destructionrates, the exergy efciency, and the exergy destruction
ratios ofthe system are shown in Figs. 46, respectively.
The effect of the environment temperature values (273.15
K,283.15 K and 298.15 K) on the exergy efciency, the
exergydestruction rates and the exergy destruction ratios is also
investi-gated through a parametric study undertaken, as shown in
Figs. 57. It is clear from Fig. 7 that the environment temperature
has nobig effect on the components. Similar to the exergy
destructionrate, the dead state temperature has no important effect
on thecomponents exergy efciencies and exergy destruction ratios,
asillustrated in Figs. 8 and 9.
tion of exogenous exergy _EEXD;k, _EAV ;EXD;k and _EUN;EXD;k
revealed that theexergy destruction within each of these components
could be de-creased by the increase in the exergy destruction
within the othercomponents. Avoidable exergy destruction indicates
the improve-ment potential for the components, while unavoidable
exergy
AC
GT
CC
HRSG
0.0 0.2 0.4 0.6 0.8 1.0Exergy Efficiencies of Components
Syste
m C
ompo
nent
s
Fig. 5. Exergy efciencies of the components in the system.
AC
GT
CC
HRSG
HPST
LPST
COND
0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16Exergy Destruction
Ratios of Components
Syste
m C
ompo
nent
s
Fig. 6. Exergy destruction ratios of the components in the
system.
AC GT CC HRSG HPST LPST COND
0
10
20
30
40
50
Exer
gy d
estru
ctio
n ra
te (M
W)
Components
298.15 K 283.15 K 273.15 K
Fig. 7. Variation of exergy destruction rates with environmental
temperature.
150 E. Akkalp et al. / Energy Conversion anUncertainties in the
measurement and total exergy values aregiven as follows:
Uncertainties for temperature, mass ow rate and pressure are0.5
C, 0.5% and 0.91%, respectively. Uncertainties associatedwith the
total fuel exergy rate, the product exergy rate and theexergy
efciency are calculated to be 4.537%, 3.171% and
4.254%,respectively.
The details of the advanced exergy analysis of the system
inves-tigated are presented as follows while the assumptions for
the ad-vanced exergy analysis are listed in Table 4. The results
for theadvanced exergy analysis are also listed in Tables 5 and 6.
Assump-tions for the advanced exergy analysis are divided into two
parts.Theoretical conditions are dened for determining the
endogenousand exogenous exergy destruction rates. For determining
theavoidable and unavoidable exergy destruction rates,
assumptionsmust represent limitations that cannot be reached at a
decade.The following results are based on the parameters given in
Table 5.
The endogenous exergy destruction rates are greater than
thecorresponding exogenous exergy destruction rates for the GT,
CC,HPST and LPST, i.e., the exergy destruction in each of these
compo-nents resulted from the component itself. The maximum
endoge-nous exergy destruction is in the CC, due to the great
chemicalirreversibility caused by the combustion process in it. The
exoge-nous exergy destruction rates were found to be greater
thanendogenous exergy destruction rates for the AC, HRSG and
COND,i.e., these components were affected at higher levels by other
com-ponents, and the exergy destruction within each of these
compo-nents could be reduced by increasing the exergy
destructionwithin the other components. The negative values for the
destruc-
AC
GT
CC
HRSG
HPST
LPST
COND
0 10 20 30 40 50
Syste
m C
ompo
nent
sExergy Destruction Rates of Components (MW)
Fig. 4. Exergy destruction rates of the components in the
system.HPST
LPST
COND
d Management 82 (2014) 146153destruction indicated the
constraints. The unavoidable exergydestruction was greater than the
avoidable exergy destruction ofeach of the system components,
except for the HPST and COND.
-
This observation led to that the system had a low potential
forimprovement. However, the maximum potential for improvementwas
in the CC (23.350 MW), which could be realized by enhancingthe
combustion efciency. The largest fraction of the avoidableexergy
destruction rate was endogenous (12.259 MW) and theremaining part
(11.091 MW) was exogenous. In addition, investi-gating the
mexogenous exergy destruction of each component,GT exhibited the
maximum effect on the CCs exergy destruction,
AC GT CC HRSG HPST LPST COND0.0
0.2
0.4
0.6
0.8
1.0
Exer
gy e
ffici
ency
Component
298.15 K 283.15 K 273.15 K
Fig. 8. Variation of exergy efciencies with environmental
temperature.
AC GT CC HRSG HPST LPST COND0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16
Exer
gy d
estru
ctio
n ra
tio
Components
298.15 K 283.15 K 273.15 K
Fig. 9. Variation of exergy destruction ratios with
environmental temperature.
Table 4Assumptions used in the advanced exergy analysis.
Component Operating Theoretical UnavoidableConditions Conditions
Conditions
AC g 0:79 g 1 g 0:85CC DP 52 kPa DP 0 DP 0
k 2:91 k 2:91 k 3:5GT g 0:73 g 1 g 0:80HRSG DTmin 200 K DTmin 0
DTmin 150 K
DP %5 DP 0 DP 0HPST g 0:89 g 1 g 0:95LPST g 0:37 g 1 g 0:50COND
DTmin 6:5 K DTmin 0 DTmin 5 K
DP %5 DP 0 DP 0
Table 5Advanced exergy parameters of the system.
Component _ED;k (MW) _EEND;k (MW)_EEXD;k (MW)
_EAVD;k (MW)_EUND;
AC 8.48 1.662 6.818 0.982 7.GT 5.663 10.283 4.620 1.489 4.CC
47.320 24.989 22.331 23.350 23.HRSG 7.010 1.052 5.958 0.376 6.HPST
0.887 0.538 0.349 0.496 0.LPST 7.220 15.703 8.483 1.481 5.COND
1.662 0.753 0.909 1.007 0.
E. Akkalp et al. / Energy Conversion and Management 82 (2014)
146153 151and the ACs exergy destruction must be increased to
decreasethe CCs exergy destruction. The mexogenous exergy
destructionof the COND had a negative value, i.e., the systems
exergy destruc-tion must be increased to decrease CONDs exergy
destruction.Using only the conventional exergy analysis, the AC and
HRSGwere concluded to have high exergy destruction rates.
However,when evaluating these components using advanced exergy
analy-sis, 7580% of these components exergy destruction rates
weredetermined to be associated with other components because
theyhave high exogenous exergy destruction rates. Exogenous
exergydestruction rates for AC and HRSG are (6.818 MW) and(5.958
MW) respectively.
The mexogenous exergy destruction rates of the AC and
HRSGdetermined which components had signicant effects on
them.According to Table 6, the results of analyzing the
mexogenousexergy destruction indicated that CC and GT affected the
ACequally and that the HRSG was affected primarily by the CC. To
de-crease the exergy destruction of these components, both CC and
GThad to be improved. For the GT and LPST, the results of the
conven-tional exergy analysis were misleading. Although the GT and
LPSThad higher exergy destruction rates, their potentials for
improve-ment were low and associated with the exergy destruction
ratesof the other components. The results of the advanced exergy
anal-ysis of the HPST and COND concluded that one should focus
onimprovements in each of the components themselves rather thanthe
effects of other components.
Figs. 1013 indicated the breakdown of the advanced
exergeticdestruction parameters for the entire system. According to
Fig. 10,the endogenous exergy destruction apparently had the
highest rate(70.3%). This high rate led to that the relationships
between thesystem components were very weak for the system. A
similar re-sult was apparent in the data shown in Fig. 11. The
potentialimprovement of the exergy destruction cost rates of the
entire sys-tem was only 37.3%. In addition, 76.5% of this
improvement poten-tial was based on the components themselves (Fig.
12). It isapparent in Fig. 13, that the unavoidable parts of the
exergydestruction rate were primarily endogenous.
The following results are acquired when the considered plant
iscompared to some systems in the literature [412]: In Ref. [4],
theauthors dened the avoidable and the unavoidable exergetic
partsof a cogeneration system. They determined that avoidable part
ofthe exergy destruction consisted of 41% of the total exergy
destruc-tion. This means that the improvement potential of the
system isrelatively low. In Ref. [5], a similar investigation was
performedfor externally red combined-cycle power plant. The
resultsshowed that the avoidable exergy destruction was equal to
33%.Thus, the system had a lower improvement potential.
Compressor
k (MW) _EAV ;END;k (MW)
_EAV ;EXD;k (MW)_EUN;END;k (MW)
_EUN;EXD;k (MW)
498 0.530 1.512 2.192 5.306174 7.625 6.136 2.658 1.516970 12.259
11.091 12.730 11.240634 0.915 1.291 1.967 4.667391 0.308 0.188
0.230 0.161
739 2.945 1.464 12.758 7.019655 0.627 0.380 0.126 0.529
-
3 had the biggest improvement potential. In Ref. [6],
refrigerationand simple gas turbine systems were investigated.
Their exergydestructions were divided into endogenous and exogenous
parts.In the refrigeration system, the endogenous part of the
exergydestruction rate was 67.6%. So, the relations of the
components atthe systemwere weak because of high endogenous exergy
destruc-
ferent fuels. For both system, endogenous exergy destruction
ratesof the system was bigger than exogenous exergy destruction
rates.approximately 64% of total exergy destruction rate was
endogenousin simple gas turbine cycle and similarly, about 78% of
the totalexergy destruction rate was endogenous in the cogeneration
sys-
Table 6Mexogenous exergy parameters of the system.
Exogenous exergy destructionof each component (MW)
Effects of the other components on theexogenous exergy
destruction (MW)
AC CC 2.7196.818 GT 2.689
MX 1.410
CC GT 24.37322.331 AC-4.732
MX 2.690
HRSG AC 0.0985.958 CC 2.174
GT 0.626MX 3.060
HPST AC 0.0250.349 CC 0.022
GT-0.013HRSG 0.035MX 0.280
COND AC 0.1330.909 CC-0.048
GT 1.850HRSG-0.140HPST 0.420LPST 3.178MX-4.484
152 E. Akkalp et al. / Energy Conversion antion rate. The
endogenous exergy destruction part of the systemFig. 10. Breakdown
of the endogenous and exogenous exergy destruction rates ofthe
system.
Fig. 11. Breakdown of the available and unavoidable exergy
destruction rates of thesystem.was 68.9%, and similar to the
refrigeration cycle, the relations ofthe components were weak. In
Ref. [7], one investigated a simplegas turbine cycle and
cogeneration system that operated with dif-
Fig. 12. Breakdown of the avoidable destruction of rates the
system.
Fig. 13. Breakdown of the unavoidable exergy destruction rates
of the system.d Management 82 (2014) 146153tem. In Ref. [8],
advanced exergy analysis for chemical reacting sys-tems was
performed using a simple open gas turbine cycle. It wasfound that
77% of the exergy destruction rate was endogenousand only 29% of
the system had improvement potential. A systemgenerating
electricity and vaporizing liqueed natural gas wasinvestigated with
advanced exergy analysis [9]. 88% of the exergydestruction rate was
endogenous and its 57% was improvable. Asystem that included liquid
natural gas regasication and an elec-tricity generation system was
also analyzed using advanced exer-gy-based methods in Ref. [10].
One found that the system had57% improvement potential. In Ref.
[11], endogenous exergy ratewas 85% for the system and its
improvement potential was only8%. In Ref. [12],endogenous exergy
rate consisted of 83% of the totalexergy destruction. In addition
to that the improvement potentialof the systemwas 33%. When the
considered systemwas comparedto others, endogenous exergy
destruction rates of the systems werehigher, ranging from 65% to
85% generally as it was our consideredsystem. The improvement
potentials of the other system also variedfrom 30% to 40% while our
system had 37.3% improvement poten-tial. Based on the results
listed above, our system represents a goodagreement with ones in
the literature.
5. Conclusions
In this paper, we have assessed the performance of an
electric-ity generation facility using natural gas through advanced
exergyanalysis based on the actual operational data. We have
concluded
-
that conventional exergy analysis could lead to
misinterpretationsthat result in incorrect improvement strategies.
In addition, onewas not able to provide any information about the
relationshipsbetween the components of the system through the
conventionalexergy analysis only while these shortcomings could be
addressedusing an advanced exergy analysis.
We have listed some concluding remarks as follows:
(a) The relations between the components are week becausetotal
endogenous exergy destruction rate is 70% of the totalexergy
destruction.
(b) The improvement potential of the system is 38%, meaningthat
systems improvement potential is low.
(c) An advanced exergy analysis of the system determined thatone
should focus on the GT and CC for possible improvementof the
system, which are the most important components ofthe system.
(d) This paper also clearly indicates that conventional
exergyanalyses are not enough to evaluate an energy
conversionsystem and it is recommended performing advanced
based
[6] Kelly S, Tsatsaronis G, Morosuk T. Advanced exergetic
analysis: approaches forsplitting the exergy destruction into
endogenous parts. Energy2009;34:38491.
[7] Razmara N, Saray RK. A simple gas turbine system and
co-generation powerplant improandment based on endogenous and
exogenous exergy destruction.PI Mech Eng A J Pow 2009;24:43347.
[8] Morosuk T, Tsatsaronis G. Advanced exergy analysis for
chemically reactionsystems-application to a simple open gas-turbine
system. Int J Thermodyn2009;12:10511.
[9] Tsatsaronis G, Morosuk T. Advanced exergetic analysis of a
novel system forgenerating electricity and vaporizing liqueed
natural gas. Energy2010;35:8209.
[10] Morosuk T, Tsatsaronis G, Boyano A, Gantiva C. Advanced
exergy-basedanalyses applied to a system including LNG regasication
and electricitygeneration. Int J Energy Environ Eng 2012;3:19.
[11] Wang L, Yang Y, Morosuk T, Tsatsaronis G. Advanced
thermodynamic analysisand evaluation of a supercritical power
plant. Energies 2012;5:185063.
[12] Petrakopoulou F, Tsatsaronis G, Morosuk T, Carassai A.
Conventional andadvanced exergetic analysis applied to a combined
power plant. Energy2012;41:14652.
[13] Petrakopoulou F, Tsatsaronis G, Morosuk T, Paitazoglou C.
Environmentalevaluation of a power plant using conventional and
advanced exergy-basedmethods. Energy 2012;45:2330.
[14] Petrakopoulou F, Tsatsaronis G, Morosuk T. Advanced
exergoeconomicanalysis applied to a complex energy conversion
system. In: Proceedings ofthe ASME 2010 international mechanical
engineering congress & exposition(Imece2010), November 1218,
2010, Vancouver, British Columbia, Canada.
[15] Petrakopoulou F, Tsatsaronis G, Morosuk T. Cost reduction
strategies for an
E. Akkalp et al. / Energy Conversion and Management 82 (2014)
146153 153exergoenvironmental analyses.
Acknowledgement
The authors are very grateful to the reviewers for their
valuableand constructive comments, which have been utilized to
improvethe quality of the paper. They also would like to thank all
the tech-nical staff of the investigated facility, located in the
EskisehirIndustry Estate Zone in Turkey.
References
[1] EPA. ; 2013 [accessed May 2013].
[2] Petrakopoulou F. Comparative evaluation of power plants with
CO2 capture:thermodynamic, economic and environmental performance,
Ph.D. Thesis,Berlin Technical University, Berlin; 2011.
[3] Tsatsaronis G. Recent developments in exergy analysis and
exergoeconomic.Int J Exergy 2008;5:48999.
[4] Tsatsaronis G, Moung-Ho P. On avoidable and unavoidable
exergy destructionsand investment costs in thermal systems. Energy
Convers Manage2002;43:125970.
[5] Cziesla F, Tsatsaronis G, Gao Z. Avoidable thermodynamic
inefciencies andcost in an externally red combined cycle power
plant. Energy2006;31:147289.oxy-fuel power plant with co2 capture:
application of an advancedexergoeconomic analysis to an advanced
zero emission plant. In:Proceedings of the ASME 2011 international
mechanical engineeringcongress & exposition (Imece2011),
November 1117, 2011, Denver,Colorado, USA.
[16] Balli O. Performance assessments of cogenarition systems
using the energy,availability (exergy) and exergoeconomic analysis
methods. Ph.d. Thesis,Eskisehir OsmangaziUniversity, Eskisehir,
Turkeyl; 2008.
[17] Balli O, Aras H. Energetic analysis of the combined heat
and power (CHP)system. Energy Explor Exploit 2007;25:3962.
[18] Balli O, Aras H, Hepbasli A. Exergetic performance
evaluation of a combinedheat and power (CHP) system in Turkey. Int
J Energy Res 2007;31:84966.
[19] Balli O, Aras H, Hepbasli A. Exergoeconomic analysis of a
combined heat andpower (CHP) system. Int J Energy Res
2007;32:27389.
[20] Moran MJ, Shapiro HN. Fundamentals of engineering
thermodynamics. NewYork: John Wiley; 1995.
[21] Bejan A, Tsatsaronis G, Moran M. Thermal design and
optimization. NewYork: Wiley; 1996.
[22] Tsatsaronis G. Design optimization using exergoeconomics.
In: Bejan A,Mamut E, editors. Thermodynamic optimization of complex
energysystems. Dordrecht: Kluwer Academic Publishers; 1999. p.
10117.
[23] Tsatsaronis G, Morosuk T. Advanced exergoeconomic
evaluation and itsapplication to compression refrigeration
machines. In: Proceedings of theASME international mechanical
engineering congress and exposition, 2007,Seattle, USA Cd-Rom, le
2007-41202.
Advanced exergy analysis of an electricity-generating facility
using natural gas1 Introduction2 System description3 Analyses
done3.1 Conventional exergy analysis3.2 Advanced exergetic
analysis3.2.1 Unavoidable and avoidable exergy destructions3.2.2
Destruction of endogenous and exogenous exergy3.2.3 Splitting
unavoidable and avoidable exergy destruction
4 Results and discussion5
ConclusionsAcknowledgementReferences