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Applied Thermal Engineering 31 (2011) 3347e3353

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Applied Thermal Engineering

journal homepage: www.elsevier .com/locate/apthermeng

Thermodynamic analysis of a trigeneration system consisting of a micro gasturbine and a double effect absorption chiller

Armando Huicochea a,*, Wilfrido Rivera a, Geydy Gutiérrez-Urueta a, Joan Carles Bruno b,Alberto Coronas b

aCentro de Investigación en Energía de la Universidad Nacional Autónoma de México (UNAM), Apartado Postal 34, Temixco 62580, Morelos, MexicobCentro de Innovación Tecnológica en Revalorización Energética y Refrigeración (CREVER), Universitat Rovira i Virgili, Autovía de Salou s/n, 43006 Tarragona, Spain

a r t i c l e i n f o

Article history:Received 8 March 2011Accepted 8 June 2011Available online 17 June 2011

Keywords:TrigenerationAir conditioningAbsorption cooling systemsMicroturbineAdvanced cycles

* Corresponding author. Tel./fax: þ52 55556229740E-mail address: huico_chea@hotmail.com (A. Huic

1359-4311/$ e see front matter Crown Copyright � 2doi:10.1016/j.applthermaleng.2011.06.016

a b s t r a c t

Combining heating and power systems represent an option to improve the efficiency of energy usage andto reduce thermal pollution toward environment. Microturbines generate electrical power and usableresidual heat which can be partially used to activate a thermally driven chiller. The purpose of this paperis to analyze theoretically the thermodynamic performance of a trigeneration system formed bya microturbine and a double-effect water/LiBr absorption chiller.

The heat data supplied to the generator of the double effect air conditioning systemwas acquired fromexperimental data of a 28 kWE microturbine, obtained at CREVER facilities. A thermodynamic simulatorwas developed at Centro de Investigación en Energía in the Universidad Nacional Autónoma de Méxicoby using a MATLAB programming language. Mass and energy balances of the main components of thecooling system were obtained with waterelithium bromide solution as working fluid. The trigenerationsystem was evaluated at different operating conditions: ambient temperatures, generation temperaturesand microturbine fuel mass flow rate. The results demonstrated that this system represents an attractivetechnological alternative to use the energy from the microturbine exhaust gases for electric powergeneration, cooling and heating produced simultaneously.

Crown Copyright � 2011 Published by Elsevier Ltd. All rights reserved.

1. Introduction

Cogeneration systems represent one of the strategic technolo-gies to increase the efficiency of energy usage and distributedpower generation. Among the ways of achieving cogeneration, alsocalled combined heating and power (CHP), the use of microturbinesis considered a very attractive option. The microturbines (MTs) aresmall size combustion turbines, with powers ranging between 28and 200 kWE. Among other advantages and from the environ-mental point of view, the use of MTs is of special interest nowadaysfor the reason that the level of CO2 and NOx emissions of MTs aresignificantly lower than that of reciprocating engines of similarcapacity, as well as fuel flexibility [1]. One application of cogene-ration systems is the coupling of an MT with absorption systems,both for single and double effect. The residual heat of theMT is usedto activate the refrigeration system. In this case, the term trigen-eration is applied since an additional benefit, cooling, is obtained.The interest in double effect systems for this application stems from

.ochea).

011 Published by Elsevier Ltd. All

the higher coefficient of performance compared to those of singleeffects, besides the commercial availability. Someworks in this fieldhave been found in the literature:

Bruno et al. [1] studied the integration of several types ofcommercially available absorption systems with MTs driven bybiogas. It was analyzed a case study for a sewage treatment plant,finding the best configuration that completed the demands for suchplant. The study developed in Ref. [2] deals with the coupling offour MTs with various power capacities with a double effectwatereLiBr absorption system, focusing mainly on the effect ofpost-combustion natural gas on the system gas to raise the coolingcapacity. Hwang [3] performed a theoretical study to show thepotential of the coupled refrigeration systems with an MT and anabsorption chiller, considering several applications of the coolingcapacity of the chiller. The energy saving of the coupling was pre-sented and its economical feasibility was also verified. Ho et al. [4]presented a cogeneration study using a single effect commercialabsorption chiller in their experiments, showing the overall systemefficiency under variable operating loads. Saito et al. [5] developeda simulation of a “micro cogeneration system” composed of a solidoxide fuel cell, an MT and a watereLiBr absorption refrigerator,considering both single and double effect. Their results show a fuel

rights reserved.

Microturbine Double effect

absorption chiller

Heat exchanger

ElectricityChilled

Hot water

Propane

Air

Exhaustgases

Heat

.

.Fuelconsumed 108.57 kW

Losses = 21.71 kW

.

.

WE = 25 kW

QEV = 35 kW

QHE = 18.1 kW

QRESIDUAL = 18.1 kW

Fig. 1. Diagram of the trigeneration system.

A. Huicochea et al. / Applied Thermal Engineering 31 (2011) 3347e33533348

consumption reduction in the areas where the systemwas applied,giving the optimal operating conditions.

More recent works include the study developed in Ge et al. [6],which simulated and tested a trigeneration system using a singlestage ammoniaewater commercial absorption system to satisfy theenergy demand of a supermarket. The system model was validatedwith the experimental results showing the effect of some parame-ters on the system performance. Arteconi et al. [7] also studieda trigeneration system for a supermarket, adding the suggestion ofcombining such system with photovoltaic systems and a technicaland economical analysis. They used both watereLiBr and ammo-niaewater absorption units in the study as well as MTs. Velumaniet al. [8] presented a hybrid cogeneration system consisting ona solid oxide fuel cell, an MT and a single effect absorption cycle tosatisfy the demand of a building. The proposed systemwould havea thermal efficiency around 70%. Some works focuses on the eval-uation of combined cooling, heating and power (CCHP) in terms ofprimary energy and economical analysis. Keil et al. [9] showed threeexamples of installation in Germany in their study, being one ofthemaCCHP systemwhichuses a double effect absorption system.Acogeneration engine supplies the heat to activate this system. Forthis particular case, the application obtained good results in termsofenergetic efficiency. A very recent work presented by Schicktanzet al. [10] analyzed the primary energy consumption and economicviability of a CCHP, based also on German data, indicating the mostinfluential parameters of each study. The importance of electricefficiency of the CHP unit is highlighted. On the other hand, variousresearchers focus on the simulation of single and double effectabsorption chillers [11e14]. These works present in detail thecalculation methods and results with respect to the system perfor-mance or exergy analysis as a functions of operating parameters,without the integration of other systems.

This paper presents an analysis of the results obtained througha simulation of the thermodynamic performance of a trigenerationsystem integrated by amicro gas turbine, a double effect absorptioncycle and a heat exchanger. The heat data supplied to the generatorwere acquired from experimental data of a 28 kWE microturbinemodel Capstone C30, from CREVER facilities. The available experi-mental data were used to analyze the influence of the operatingparameters of the microturbine on the specific systems perfor-mance. The results obtainedwill be useful to pose a scenario for thiskind of trigeneration system.

2. System description

The proposed trigeneration system consists of a microturbine toproduce electrical power, a double effect absorption water/LiBrchiller for air conditioning and a heat exchanger to produce hotwater. A portion of the energy of the exhaust gases at hightemperature of the MT are used to supply heat to the generator ofthe double effect absorption system. The remaining portion, withhigh enough temperature, is used to generate hot water in the heatexchanger. Fig. 1 shows the schematic diagram of this system withan example of values of energy obtained.

2.1. The microturbine

A microturbine consists of a centrifugal compressor, a radialturbine and alternator rotor, operating as a Brayton cycle. Its mainfeature is that ahigh speedgenerator isdirectlycoupled to the turbinerotor and uses power electronics instead of a gearbox and conven-tional generator. Amicroturbine usually uses a single shaft,whichhaslower production costs than the double shaft and the generator canalso be mounted opposite to the exhaust gases, therefore, they comeout with lower pressure loss, which improve the net power and

reduces the fuel consumption. Another way of decreasing the fuelconsumption, is to use regenerators to preheat the inlet air, in addi-tion, air emissions are very low at full load. The microturbine used inthis analysis can be fueled with natural gas or propane. It is a 28 kWECapstoneC30model [15,16]. Detailed description about experimentalfacility used to obtain the data is found in Ref. [16].

2.2. Double effect absorption chiller

The main components of a double effect absorption system area condenser, an evaporator, an absorber, a low pressure generator,a high pressure generator, two solution heat exchangers, a pumpand throttling valves as shown in Fig. 2. A double effect absorptionchiller can operate at three pressures and four temperatures levels.The heat is supplied to the high pressure generator ð _QHP;GEÞ toobtain the primary steam and a concentrated working solution. Theprimary vapor changes to liquid phase in the low pressure gener-ator, giving the heat of vaporization to the concentrated solutionð _QLP;GEÞ to generate a secondary steam (going to the condenser)and the most concentrated solution, which goes to the absorber. Inthe condenser, two refrigerant lines converge to transfer heat to anexternal circuit ð _QCOÞ and change the steam to liquid phase. Thecondensed water is evaporated at low pressure, removing the heatof vaporization of the area to be cooled ð _QEVÞ. In the absorber, thevapor contacts the concentrated solution (coming from the lowpressure generator through the solution heat exchanger 1) toobtain a useful heat at low temperature ð _QABÞ. The diluted workingsolution obtained in the absorber is sent to the high pressuregenerator, passing through solution heat exchangers 1 and 2, torepeat continuously the thermodynamic cycle.

2.3. Heat exchanger

A 40 kW plate heat exchanger was used in this analysis. The heatexchanger uses directly a part of exhaust gases of theMTand residualheat of the double effect absorption chiller to produce hot water.

3. Mathematical model of the double effect absorption chiller

The developed model is based on the following assumptions:

a) The analysis is made under thermodynamic equilibrium andsteady state condition.

2

1

7

TEV TAB TGE, HP

Evaporator Absorber

Condenser

SHE 1

PGE, HP

PGE, LP

PAB

TGE, LP

GE, LP

16

15

17

9

10

13

12

11

5

GE, HP

4

38

14

6SHE 2

Fig. 2. Schematic diagram of a double effect absorption chiller.

A. Huicochea et al. / Applied Thermal Engineering 31 (2011) 3347e3353 3349

b) Heat losses and pressure drops in piping and the componentsare negligible.

c) The waterelithium bromide solution in the generator andabsorber outlet is saturated.

d) The water and vapor leaving the condenser and the evaporator,respectively, is saturated.

e) The expanding process in the throttling valves is isenthalpic.f) The waterelithium bromide concentrations is zero in steam

phase.g) The outlet temperatures of main components and the evapo-

rator heat load are assumed as inlet values.h) The solution heat exchangers effectiveness, i.e., the ratio of the

actual heat transfer to the maximum possible heat transfer forthe given inlet conditions, is assumed as 0.7.

It is possible to determine the thermodynamic conditions inorder to estimate the performance of a double effect absorptionchiller. This is done by using energy analysis applying the principlesof mass, species and energy conservation (Eqs. (1)e(3)):X

_mIN ¼X

_mOUT (1)

X_mINXIN ¼

X_mOUTXOUT (2)

X_Q �

X_W ¼

X_mOUThOUT �

X_mINhIN (3)

The working solution concentration ratio is an important operationparameter to understand the behavior of an absorption system. It isdefined as the ratio between concentration in low pressuregenerator and the concentration difference between low pressuregenerator and absorber. This can also be expressed as:

FRAB ¼ _m1_m17

(4)

Mass and energy balances were estimated for each one of the maincomponents of the system with reference to Fig. 2, obtaining thefollowing equation system:

Evaporator:

_m16 ¼ _m17 (5)

_QEV þ h16 _m16 ¼ h17 _m17 (6)

Condenser:

_m13 þ _m14 ¼ _m15 (7)

h13 _m13 þ h14 _m14 ¼ _QCO þ h15 _m15 (8)

Absorber:

_m17 þ _m10 ¼ _m1 (9)

_m17X17 þ _m10X10 ¼ _m1X1 (10)

h17 _m17 þ h10 _m10 ¼ _QAB þ h1 _m1 (11)

Generator (low pressure):

_m11 ¼ _m12 (12)

_m7 ¼ _m14 þ _m8 (13)

h7 _m7 þ h11 _m11 � h12 _m12 � h14 _m14 � h8 _m8 ¼ 0 (14)

Generator (high pressure):

_m4 ¼ _m5 þ _m11 (15)

_m4X4 ¼ _m5X5 þ _m11X11 (16)

_QGE þ h4 _m4 ¼ h5 _m5 þ h11 _m11 (17)

Solution Heat Exchanger 1:

_m2 ¼ _m3 (18)

A. Huicochea et al. / Applied Thermal Engineering 31 (2011) 3347e33533350

_m8 ¼ _m9 (19)

h2 _m2 þ h8 _m8 ¼ h3 _m3 þ h9 _m9 (20)

Fig. 3. Microturbine electric power versus ambient temperature.

Solution Heat Exchanger 2:

_m3 ¼ _m4 (21)

_m5 ¼ _m6 (22)

h3 _m3 þ h5 _m5 ¼ h4 _m4 þ h6 _m6 (23)

A thermodynamic simulator for a double effect absorptionchiller was developed the Centro de Investigaciones en Energía ofthe Universidad Nacional Autónoma de México by using a MATLABprogramming language. Simulations were carried out according tothe following operating conditions:

� The evaporator heat ranges from 25 kW to 35 kW.� Condenser temperature was equal to the absorber

temperature.� Condensation temperature was considered seven degrees

higher than environment temperature, which was variedfrom 23 �C to 37 �C.

� Generation temperature ranges from 80 �C to 200 �C� Evaporation temperature ranges from 4 �C to 10 �C.� Effectiveness of the heat exchangers was fixed at 70%.

The NIST/ASME Steam properties software [17] was used forwater properties, and correlations reported by McNeely [18] wereused for the waterelithium bromide mixture.

4. System performance

The coefficient of performance for a double effect absorptionchiller is defined by Eq. (24), which includes the electric power:

COP ¼_QEV

_QHP;GE þ _Qaux(24)

With _Qaux define as (Izquierdo et al. [19]):

_Qaux ¼_Wpump

hcen(25)

The generating efficiency of the electricity system hcen wasassumed as 0.33. The electrical efficiency is defined as:

hE ¼_WE

_mfuelLHV(26)

With _mfuel and LHV representing fuel consumption and the lowerheating value of the fuel, respectively.

The overall system efficiency is calculated in some works as theratio between the sum of the electrical, cooling and heating powerto the gas power consumption [20e22]. However, because of the

Table 1Comparison between reported data and the developed model.

Component Anand and Kumar(1987)

Presentwork

Difference(%)

High pressure generator(kW)

1858.94 1863.61 0.25

Low pressure generator(kW)

1268.60 1258.64 �0.78

Absorber (kW) 2922.39 2918.69 �0.12Condenser (kW) 1289.53 1300.95 0.88Evaporator (kW) 2357.17 2355.69 �0.06COP (dimensionless) 1.268 1.264 �0.30

weakness of this estimation (regarding to the fact that electricity ismore valuable than process heat) the second-law (exergy) effi-ciency is used by some authors [23,24] among other methods. Inthis work, the MT electric efficiency and the COP of the doubleeffect absorption system are presented individually. The heatexchanger efficiency in the process (between exhausting gases andliquid) was considered as 0.5, according to reported values in theliterature [25].

5. Results

In this section, the simulation results obtained through thevariation of operating parameters of the system under study arepresented.

Simulation results corresponding to the performance of a doubleeffect absorption chiller, obtained bymeans of themodel developedin this work, were compared with data reported in the literature[26]. The operating conditions taken for the comparison were:TGE ¼ 140.6 �C, TEV ¼ 7.2 �C, TCO ¼ TAB ¼ 37.8 �C, solution heatexchangers efficiency¼ 0.7 and vapormassflow rate¼ 1 kg/s. Thesevalues are the same as those given in Ref. [26] and theyare used onlyfor validation purposes. The maximum difference obtained was0.88% as it is exposed in Table 1. These results are a reference for thevalidity of the mathematical model presented here.

The MT data used in this study is based on the work developedby Vidal et al. [16], in which correlations for the electrical power,

Fig. 4. Microturbine fuel consumption for the experimental data.

Fig. 5. Coefficient of performance against generator temperature at five differentambient temperatures.

Fig. 7. Solution concentration ratio and coefficient of performance against generatortemperature at three different evaporation temperatures.

A. Huicochea et al. / Applied Thermal Engineering 31 (2011) 3347e3353 3351

the fuel consumption, and exhaust gases mass flow rate areobtained from experimental results. The data was obtained for fullload considering that the MT, and therefore the cogenerationsystem, is more efficient operating at full load. The energy savingwill be higher than that obtained at partial load, in which case itcould be not attractive compared to a conventional system.

Figs. 3 and 4 represent the experimental data of the net outputpower from the MT and fuel consumption, respectively, as a func-tion of the ambient temperature [16].

The coefficient of performance COP against the generatortemperature TGE is plotted in Fig. 5, showing the influence ofambient temperatures for five different values. The values of TGE areused to show the sensitivity of the chiller performance to thevariation of the temperatures of the MT exhaust gases. The figureillustrates that the COP increase at lower ambient temperatures,following a similar behavior of electric power in Fig. 3. Moreover, ifthe ambient temperature is higher, for instance at 36 �C, the coolingsystem cannot operate at generation temperatures lower than146 �C and it is necessary to reach temperatures close to 166 �C toobtain the highest COP of 1.289 at that ambient temperature.

Fig. 6 shows the COP against TGE at four different evaporatortemperatures TEV ¼ 4 �C, 6 �C, 8 �C and 10 �C. The fixed conditionsfor ambient temperature and cooling power are given in this figure.It can be appreciated that the COP increases rapidly at low

Fig. 6. Coefficient of performance against generator temperature at four differentevaporation temperatures.

Fig. 8. Left side: Microturbine electric power, evaporator and heat exchanger loads.Right side: coefficient of performance, heat exchanger efficiency and microturbineelectric efficiency. All parameters are plotted against ambient temperature.

Fig. 9. Left side: Microturbine electric power, evaporator and heat exchanger loads.Right side: coefficient of performance, heat exchanger efficiency and microturbineelectric efficiency. All parameters are plotted against fuel mass flow rate.

A. Huicochea et al. / Applied Thermal Engineering 31 (2011) 3347e33533352

generation temperatures (TGE < 148 �C) and then remains almostconstant at higher TGE. In addition, it increases with an increment ofthe evaporator temperatures varying from 1.130 to 1.327.

Fig. 7 illustrates the solution concentration ratio FRAB and theCOPof the cooling systemasa functionof thegeneration temperature TGE,for the selected evaporation temperatures. The fixed conditions forambient temperature and cooling power are given in this figure. TheFRABdecreases andtheCOP increaseswith an incrementofTGE for thereason that the amount of water vapor produced in the generatorincreases (see Eqs. (4) and (24) for FRAB and COP). A lower FRAB

implies lower pumping costs and smaller component size, such asgenerator and absorber [27]. Also, it can be observed that an increasein the evaporator temperature decreases FRAB values.

The performance parameters for the individual componentsintegrating the trigeneration systems (MT, absorption chiller andheat exchanger) are depicted in Fig. 8 as a function of the ambienttemperature. The interaction of such components can be observedin this figure. The _QEV is fixed to 35 kW. The COP of the doubleeffect absorption chiller and the heat load obtained in the heatexchanger _QHE follows the tendency of the electric power _WEgenerated from the MT, which verifies the importance to increasethe electric efficiency of the MT in this kind of systems (cogene-ration or trigeneration). The benefit of using the remaining part ofthe rejected energy from the MT and the absorption chiller isobserved in the quantity of _QHE which is around 18 kW. The MTelectric efficiency hE decreases as the ambient temperature Tambincreases, ranging from 0.233 to 0.227 for Tamb from 24.4 to 28.9 �C.This is an approximate reduction of 0.55% per �C. The corre-sponding reduction for _WE is 1.13%, for the COP is 1.04% and 1.44%for _QHE. The decreasing tendency of all parameters with theincrease of ambient temperature is noticeable is this figure.

The same variables are plotted in Fig. 9 against the fuelmassflowrate _mfuel. Again, the performanceparameters follow thebehavior of_WE, but this time showing an increasing tendency with highervalues of fuelmassflow rate. This is obvious since the increase in thefuel consumed leads to an increase in the electrical power obtained.The increase of the individual performance parameters per 1 kg/h of_mfuel are: 10.5% for _WE, 16.5% for the COP and 21.4% for _QHE.

As mentioned in a previous section, the efficiency of themicroturbine under study is around 0.23 when it is used only forelectric power generation. This low value can be compensated withthe implementation of a trigeneration system like the one pre-sented here, which represents an attractive option to use theenergy of the microturbine exhaust gases for electric powergeneration, cooling and heating produced simultaneously.

6. Conclusions

A trigeneration system for the production of electricity, coolingand heating has been analyzed. A microturbine real data has beenused together with a mathematical model of a double effect coolingsystem to predict the performance of the trigeneration system,which was evaluated at different operating conditions. Theimportance to increase the electric efficiency of the MT in this kindof systems was illustrated. The low efficiency obtained froma microturbine when it is used to produces only power generation,can be compensated with the implementation of a trigenerationsystem like the one presented here. The results demonstrated thatthis system represents an attractive technological alternative to usethe energy from the microturbine exhaust gases for electric powergeneration, cooling and heating produced simultaneously.

Acknowledgements

The authors want to express their gratitude to the UniversidadNacional Autónoma de México (UNAM) and Consejo National deCiencia y Tecnología (CONACYT) for the support given throughpostdoctoral fellowships.

Nomenclature

COP coefficient of performance (dimensionless)FR concentration ratio (dimensionless)h specific enthalpy (kJ/kg)MT microturbine_m mass flux rate (kg/s)_Q heat flow rate (kW)T temperature (�C)W power or work (kW)X mass fraction of LiBr in working solution (%)

Subscripts1e17 connection linesAB absorberamb ambientcen centralC coolingCO condenserE electricalEV evaporatorGE generatorH heatingHE heat exchangerHP high pressureIN input

A. Huicochea et al. / Applied Thermal Engineering 31 (2011) 3347e3353 3353

LP low pressureOUT outputS system

References

[1] J.C. Bruno, V. Ortega-López, A. Coronas, Integration of absorption coolingsystems into micro gas turbine trigeneration systems using biogas: case studyof a sewage treatment plant, Applied Energy 86 (2009) 837e849.

[2] J.C. Bruno, A. Valero, A. Coronas, Performance analysis of combined microgasturbines and gas fired water/LiBr absorption chillers with post-combustion,Applied Thermal Engineering 25 (2005) 87e89.

[3] Y. Hwang, Potential energy benefits of integrated refrigeration system withmicroturbine and absorption chiller, International Journal of Refrigeration 27(2004) 816e829.

[4] J.C. Ho, K.J. Chua, S.K. Chou, Performance study of a microturbine system forcogeneration application, Renewable Energy 29 (2004) 1121e1133.

[5] M. Saito, H. Yoshida, Y. Imamoto, A. Ueda, An analysis of a micro cogenerationsystemcomposedof solid oxide fuel cell,microturbine, andH2O/LiBr absorptionrefrigerator, Journal of Thermal Science & Technology 2 (2007) 168e179.

[6] Y.T. Ge, S.A. Tassou, I. Chaer, N. Suguartha, Performance evaluation of a tri-generation system with simulation and experiment, Applied Energy 86(2009) 2317e2326.

[7] A. Arteconi, C. Brandoni, F. Polonara, Distributed generation and trigeneration:energy saving opportunities in Italian supermarket sector, Applied ThermalEngineering 29 (2009) 1735e1743.

[8] S. Velumani, C.E. Guzmán, R. Peniche, R. Vega, Proposal of a hybrid CHPsystem: SOFC/microturbine/absorption chiller, International Journal of EnergyResource 34 (2010) 1088e1095.

[9] K. Christian, S. Plura, M. Radspieler, C. Schweigler, Application of customizedabsorption heat pumps for utilization of low-grade heat sources, AppliedThermal Engineering 28 (2009) 2070e2076.

[10] M.D. Schicktanz, J.Wapler,H.M.Henning, Primary energy andeconomic analysisof combined heating, cooling and power systems, Energy 36 (2011) 575e585.

[11] S. Aphornratana, T. Sriveeraku, Experimental studies of a single-effectabsorption refrigerator using aqueous lithiumebromide: effect of operatingcondition to system performance, Experimental Thermal and Fluid Science 32(2007) 658e669.

[12] R. Gomri, R. Hakimi, Second law analysis of double effect vapour absorptioncooler system, Energy Conversion and Management 49 (2008) 3343e3348.

[13] A. Yattara, Y. Zhu, M. Mosa Ali, Comparison between solar single-effect andsingle-effect double-lift absorption machines (part I), Applied Thermal Engi-neering 23 (2003) 1981e1992.

[14] M.B. Arun, M.P. Maiya, S. Sririvasa Murthy, Performance comparison ofa double effect parallel-flow and series-flow waterelithium bromideabsorption systems, Applied Thermal Engineering 21 (2001) 1273e1279.

[15] J.C. Bruno, W. Rivera, N. Velázquez, R. Best, A. Coronas, Thermodynamicanalysis of a directly coupled GAX chiler/micro gas turbine combined system,Eurotherm Seminar, vol. 72, 2003, pp. 369e374.

[16] A. Vidal, J.C. Bruno, R. Best, A. Coronas, Performance characteristics andmodeling of a micro gas turbine for their integration with thermally activatedcooling technologies, International Journal Energy Research 31 (2007)119e134.

[17] NIST/ASME number 10, Steam properties data base Software, version 2.1,1998.

[18] L.A. McNeely, Thermodynamic properties of aqueous solutions of lithiumbromide, ASHRAE Transactions 85 (1979) 413e434.

[19] M. Izquierdo, R. Lizarte, J.D. Marcos, G. Gutiérrez, Air conditioning using anair-cooled single effect lithium bromide absorption chiller: results of a trialconducted in Madrid in august 2005, Applied Thermal Engineering 28 (2008)1074e1081.

[20] H.I. Onovwiona, V.I. Ugursal, Residential cogeneration systems: review of thecurrent technology, Renewable and Sustainable Energy Reviews 10 (2006)389e431.

[21] W. Somcharoenwattana, C. Menkea, D. Kamolpus, D. Gvozdenac, Study ofoperational parameters improvement of natural-gas cogeneration plant inpublic buildings in Thailand, Energy and Buildings 43 (2011) 925e934.

[22] F. Jiménez-Espadafor Aguilar, M. Torres García, E. Carvajal Trujillo, J.A. BecerraVillanueva, F.J. Florencio Ojeda, Prediction of performance, energy savings andincrease in profitability of two gas turbine steam generator cogenerationplant, based on experimental data, Energy 36 (2011) 742e754.

[23] A. Abusoglu, M. Kanoglu, Exergetic and thermoeconomic analyses of dieselengine powered cogeneration: part 1 e formulations, Applied ThermalEngineering 29 (2009) 234e241.

[24] M. Kanoglu, I. Dincer, Performance assessment of cogeneration plants, EnergyConversion and Management 50 (2009) 76e81.

[25] A. Faghir, Heat Pipe Science and Technology. Taylor & Francis, USA, 1995.[26] D.K. Anand, B. Kumar, Absorption machine irreversibility using new entropy

calculations, Solar Energy 3 (1984) 243e256.[27] W. Rivera, R. Best, J. Hernández, C.L. Heard, F.A. Holland, Thermodynamic

study of advanced absorption heat transformersdII. Double absorptionconfigurations, Heat Recovery Systems and CHP 14 (2003) 185e193.