Exergy, Economic and Environmental Analysis for Simple and Combined Heat and Power IC Engines

Transcription

1 Sustainability 2015, 7, ; di: /su Articl OPEN AESS sustainability ISSN Exrgy, Ecnmic and Envirnmntal Analysis fr Simpl and mbind Hat and Pwr I Engins Mhdi Alihyai 1, *, Faridh Atabi 2, Mhammad Khrshidvand 3 and Marc A. Rsn 4 1 Dpartmnt f Mchanical Enginring, Islamic Azad Univrsity, Pardis Branch, Pardis Nw ity, Iran 2 Scinc and Rsarch Branch, Islamic Azad Univrsity, Thran, Iran; far-atabi@jamjam.nt 3 Dzful Branch, Islamic Azad Univrsity, 113 Dzful ity, Iran; m.khrshidvand@gmail.cm 4 Faculty f Enginring and Applid Scinc, Univrsity f Ontari Institut f Tchnlgy, 2000 Simc Strt Nrth, Oshawa, ON L1H 7K4, anada; marc.rsn@uit.ca * Authr t whm crrspndnc shuld b addrssd; alihyai@yah.cm; Tl: Acadmic Editr: Francsc Asdrubali Rcivd: 21 Dcmbr 2014 / Accptd: 11 March 2015 / Publishd: 14 April 2015 Abstract: This study rprts th rsults f xrgy, cnmic and nvirnmntal analyss f simpl and cmbind hat and pwr intrnal cmbustin ngins. Valus f ntrpy prductin, scnd law fficincy ar calculatd, and an bjctiv functin, including initial, pratin, maintnanc and ful csts, as wll as th xtrnal csts f nvirnmntal pllutants, such as O2, O and NOx, ar prsntd fr th flu gas f th intrnal cmbustin ngin. Th rsults shw that ntrpy gnratin in th cmbind hat and pwr md is 30% lwr than that in th simpl intrnal cmbustin ngin. Als, by xcssivly incrasing th air rati, th systm ntrpy gnratin dcrass in bth cass f simpl and cmbind hat and pwr I ngins. Th gratst prtin f ntrpy gnratin is rlatd t th cmbind hat and pwr intrnal cmbustin ngin. Th gas hat xchangr gnrats mr ntrpy than th jackt hat xchangr. Lwr valus f lctricity cst and xtrnal csts f air pllutin ar prvidd by highr valus f mlar air t ful rati. Th nvirnmntal aspcts dpnd n lcatin f th systm and tim f ngin pratin. Kywrds: xrgy; xtrnal; cst; intrnal; cmbustin; ngin

2 Sustainability 2015, Intrductin gnratin systm is cnsidrd n f th mst imprtant mthds fr nrgy saving. gnratin systms ar usd whr bth lctricity and hat ar rquird. gnratin systms utiliz th wast hat prducd during lctricity gnratin and apply it fr hating purpss. Sinc cgnratin, r cmbind hat and pwr (HP, systms prduc bth thrmal nrgy (gnrally in th frm f stam r ht watr and lctricity, th first law fficincy can b incrasd frm arund 35% t 55% in cnvntinal pwr plants t vr 90% in HP systms [1 3]. Rciprcating HP units ar gnrally applicabl in lw and mdium pwr cgnratin units. Th sizs f rciprcating HP units dpnd n ful typ and us. Ths can rang frm 50 kw t 10 MW fr natural gas, frm 50 kw t 50 MW fr disl, and frm 2.5 MW t 50 MW fr havy ful il [1 3]. In cmprssin ignitin (I ngins, fur mthds t utiliz wast hat xist: xhaust gas, ngin jackt cling watr, lub il cling watr, and turbchargr cling watr. Th xhaust gass frm disl cgnratin plants ar a main surc f thrmal nrgy fr cmbind hat and pwr applicatins. Th high tmpratur xhaust gas can prduc mdium prssur stam (apprximatly 10 Bar, lw-prssur stam (apprximatly 2 bar and ht watr [1 3]. Lw prssur stam prducd by I ngin cgnratin systms is apprpriat fr lw tmpratur prcss nds such as spac hating, ptabl watr hating and spac cling with absrptin chillrs [1 3]. Numrus nrgy, xrgy and xrg-cnmic analyss f HP r simpl intrnal cmbustin ngins hav bn rprtd. Alkidas [4] prfrmd first and scnd law analyss fr a disl ngin prating at cnstant spd. H cncludd that th ngin scnd-law fficincy incrass with ngin lad and varis frm 22 t 50 prcnt; h als fund that th cmbustin prcss is th mst imprtant surc f irrvrsibility and accunts fr 25 t 43 prcnt f th lst pwr. Danv and Gupta [5] dvlpd a mdl t invstigat a cycl cnsisting f a turbchargd disl ngin (th tpping cycl, a hat rcvry stam gnratr (HRSG and a stam turbin plant (th bttming cycl. This mdl can prdict cycl prfrmanc fr varius cnditins. Kanglutal [6] prfrmd xrgy and nrgy analyss f a 120MW disl ngin pwr plant. Th nrgy and xrgy fficincis f this plant ar 47% and 44%, rspctivly. Ballital [7,8] prfrmd thrmdynamic and thrm cnmic analyss f a tri gnratin systm with a gas disl ngin having a ratd utput f 6.5 MW, whr th gas disl ngin is installd in th Eskishir Industry Estat Zn, Turky. Thy calculatd th fficincis basd n nrgy 59%, xrgy (36%, public utility rgulatry plicis act (PURPA and quivalnt lctrical f th ntir systm (49%. Fu t al. [9] imprvd I ngin utilizatin fficincy by pn stam pwr cycl. Th bttm cycl was a fur-cylindr naturally aspiratd I ngin: with thr cylindrs takn as ignitin cylindr, th last n was usd fr stam xpansin cylindr; I ngin xhaust pip was cupld with a Rankin stam cycl systm which usd th high tmpratur xhaust gas t gnrat stam. Thy shwd that th rcvry fficincy f xhaust gas nrgy was mainly limitd by xhaust gas tmpratur. Th maximum bttm cycl pwr rachd 19.2 kw and I ngin thrmal fficincy can b imprvd by 6.3% at 6000 r/min. Ehyai t al. [10] did tchnical, cnmical, and nvirnmntal study f applying intrnal cmbustin (I ngins fr supplying th rquird lctricity, dmstic ht watr (DHW, hating

3 Sustainability 2015, and cling nrgy lads in a typical rsidntial building lcatd in Thran. Thy shwd fiv units f G3306B I ngin and cmbind hat and pwr (HP intrnal cmbustin ngin mt th rquird nrgy f this building. Th annual avrag lctricity cst f this systm is qual t 0.05 (US$/kWh and th annual ntrpy gnratin f this systm is qual t 29,903 (GJ/yar. Rqu Díaz t al. [11] did a rsarch abut th Equipmnt slctin and pratin rquir th charactrizatin f pwr, hating and cling lad dmands, and thir tim variatin during yars, sasns, mnths and vn hurs r minuts. Th prsnt rsarch invlvs xrgy, cnmic and nvirnmntal analyss f simpl and HP intrnal cmbustin ngins with cnsidratin f ntrpy prductin, scnd law fficincy, and nrgy csts, including th xtrnal cst f th nvirnmntal pllutants, such as O2, O and NO, prsnt in th flu gas f I ngins. Th nvirnmntal aspcts f air pllutin and als thr pllutin impacts such as dgradatin f watr, sil, tc., causd by pwr gnratin systms ar nt includd in this study. Th fllwing stps dscrib th scp f this study: (1 Exrgy and cnmic analyss f HP and simpl I units ar cnductd. (2 A cmputr prgram cd is dvlpd in FORTRAN t simulat an I ngin unit and t assss th ffcts f hat rcvry xchangrs n xrgy and cnmic analyss. (3 An cnmic analysis is prfrmd, including th xtrnal cst f air pllutin. (4 Th ffcts f including hat rcvry hat xchangrs ar assssd n th cst f lctricity, ntrpy gnratin and scnd law fficincy. 2. Systm Mdling An E2876E302 I ngin with a nminal lctrical pwr 130 kw at ISO cnditins is cnsidrd. This ngin uss natural gas as ful [12]. Th gas ngin and gnratr ar cupld by an lastic cupling, and th systm is quippd with a vibratin absrbr, gas filtr, slnid valv prssur, ful valv with lctrnic gvrnr and lctrnic ignitin systm. In this ngin, watr is usd fr cling purpss. ling watr is pumpd in a clsd circuit by an lctrical watr pump. This ngin is quippd with hat xchangrs fr th watr jackt and xhaust gas fr th purps f hat rcvry. In th simpl I ngin md th lctrical gnratr is mplyd, whil in th HP md th watr jackt and xhaust gas hat xchangrs ar usd. In th HP md and fr dmstic us, urban watr absrbd hat frm warmd cling watr in th watr jackt hat xchangr passs t th xhaust gas hat xchangr whr it absrbs hat frm th ht xhaust gas. With watr mass flw rats in bth hat xchangrs w calculat th tmpraturs f ht watr fr dmstic cnsumptin t b arund Figur 1 shws th cnfiguratin f this systm. Th spcificatins f th I ngin, jackt watr and xhaust gas hat xchangrs ar prvidd in Tabls 1 3, rspctivly. Enrgy mdling Equatin is as fllwing: du Q W h dm i i (1 whr, δq is a hat transfr btwn in cylindr gass and walls (kj. δw is a wrk transfr btwn systm and nvirnmnt and it is calculatd frm PdV Equatin (kj. Th last trm is rlatd t systm nrgy transmissin with intrnal r xtrnal fluid mass flux (kj.

4 Sustainability 2015, Engin hat transfr can b calculatd frm Equatin (2. Fr having mr accurat ngin prfrmanc stimatin an mpirical cnstant f is usd at Equatin (2 that is variabl by kinds f ngin and ful [13]: Q hct Tw 9 T Tw A 10 whr is cnstant, h is hat cnvctin cfficint (kw/kg K, T is tmpratur (K, A is ara (m 2 and subscript w dnts th wall. Fr cmprssin, xpansin and cmbustin prcsss, fllwing Equatin can b applid: dt 1 dq dv P d nc d d v dp 1 dt dv nr P d V d d n is numbr f mls, R is univrsal gas cnstant (kj/kg K, V is vlum (m 3 Nticabl pint is that Equatin (4 fr xpansin prcss is valid by nglcting ttal ml numbr variatin during this prcss. dtu 1 dp dqu Vu P d n c d d u p, u (2 (3 (4 (5 dtb P dv Vb dnb Vu dnu R dp dqu V dp Vu d Rn b d nb d nu d Pc p, u d d P d cv,b dv dq dnu dn b 1 1 P nu nb R dp c c d d d d v,u c v,b p,b Vu V dθ c p,u R dn c b dn u v,u c v,b dqu cv,b Tb Tu dθ dθ c p,u dθ (6 (7 It is nticabl that at ach cmputatinal stp sm f th unburnd mixtur is cmbustd and ntrs th burnd zn. Thrfr fluid flux xists btwn burnd and unburnd zns. Significatins f this transmissin ar dnu and dnb in Equatins (6 and (7. Ths tw trms ar rlatd via mass dθ dθ M u dnb dn dn u u cnsrvatin law by quatin M b. Equatin (8 can b usd fr calculating dθ, which is drivd basd n turbulnt flam spd. dnu d dt ua d t f Af is a frntal flam ara, that it is calculatd with assumptin f sphrical flam advanc. It is mdld basd n flam clash with pistn wall and cylindr wall. ut is calculatd with mpirical rlatins fr laminar flam vlcity. (8

5 Sustainability 2015, Figur 1. nfiguratin f th systm. Tabl 1. Spcificatins f th I (intrnal cmbustin ngin. Engin Spcificatin Valu Engin typ E2876E302 ylindr numbr In-lin 4, 4-strk cycl ylindr br 128 mm Mtr lngth 2650 mm Mtr width 1000 mm Mtr hight 1500 mm Strk 166 mm Firing rdr Spd 1000 rpm mprssin rati 12:1 Maximum lctrical pwr at ISO cnditin 130 kw Wight 1850 kg Mlar air-ful rati 1.5 Intak typ Naturally aspiratd Ratd vltag 220 V Ratd currnt 18 A Starting md 24VD lctric starting systm Frquncy 50 HZ/60 HZ

6 Sustainability 2015, Tabl 2. Spcificatins f th jackt watr hat xchangr. Hat xchangr spcificatin Lngth Valu 1.7 m Hight 1.7 m Width 1.7 m Numbr f tubs 30 Diamtr f tubs 0.1 m Lngth pitch 0.15 m Width pitch 0.15 m Gas mass flw rat 2.2 kg/s Tabl 3. Spcificatins f th xhaust gas hat xchangr. Hat xchangr spcificatin Valu Lngth 1.5 m Hight 1.5 m Width 1.5 m Numbr f tubs 31 Diamtr f tubs 0.1 m Lngth pitch m Width pitch m Mass flw f cling watr 7 kg/s Pwr t hat rati is a ky paramtr and can b calculatd as fllws [14]: Hr, W nt PHR W Q nt (9 nt is th nt lctrical pwr (W, and Q nt is th nt hat rcvrd in watr jackt and gas hat xchangrs (W. Th first law (r nrgy fficincy fr this systm is calculatd as fllws, fr simpl and HP ngin mdls, rspctivly: W nt I (10 m LHV f W nt Q nt I (11 m LHV Hr, m f is th ful mass flw rat (kgsc 1 and LHV is th lw hating valu f th ful (Jkg 1. Applying th first and th scnd laws f thrmdynamics, th ttal xrgy f this systm is btaind [15]: t ph ch (12 In which, is an xrgy (Jkg 1 and subscripts t, ph and ch dnt ttal, physical and chmical xrgis, rspctivly. Th physical xrgy fr idal gass ar dfind as [15]: f

7 Sustainability 2015, ph p T T T T 1 ln ( RT T ln P P (13 Whr p is th cnstant-prssur spcific hat cfficint (Jkg 1 K 1, T is th tmpratur (K, P is a prssur (Pa and 0 dnts th rfrnc cnditin. Th mixtur chmical xrgy is dfind as [15]: ch n i1 x i n ch, i RT xi xi i1 ln( (14 Whr x i is th mass fractin, R is th gas cnstant (Jkg 1 K 1 and ch,i is th chmical xrgy f ach cmpnnt (Jkg 1. Th ntrpy gnratin is calculatd as fllws fr simpl and HP mdls: S 1 gn T in m t ut m t W nt (15 1 T 0 S m m W Q gn t t nt nt (1 T (16 in ut T Fr an I ngin, jackt and gas hat xchangrs, ntrpy gnratin is calculatd as fllws: S gn S gn m [ m S gn c a I, Engin J. HX [ m x, ch, ful (1/ T ] x, ph, ccling G. HX c in (1 / T x, ph, gas [ m watr (1 / T [ g m m [ c m f x, ph, gas m [ g m g x, ph, ful m g m x, ph, clingwat gas x, ch, dmstic x, ph, gas x, ch, dmstic f x, ch, gas r watr x, ch, ful ] watr ut m m ] ut w w ] W ut m nt a x, ph, ful x, ph, dmsticwa x, ph, dmsticwa tr tr ] in ] in (17 (18 (19 Th ttal systm ntrpy gnratin is calculatd as fllws: S gn, S, S Ttal gn I, Engin S gn, J, HX gn, G, HX (20 3. Estimatin f Elctricity st (Objctiv Functin Prducd by an I Engin Th cst f lctricity prducd by a pwr gnratin systm may b btaind as fllws [16]: E 1 O F A (21 whr E, I, O, F and A ar th cst f lctricity, th cst assciatd with th initial invstmnt (including th installatin cst, with pratin and maintnanc, with ful cnsumptin and th intrnalizd xtrnal cst f air pllutin, rspctivly (US$kWh 1. Th salvag valu f th installatin is assumd t b ngligibl. Fr I, I I ( f

8 Sustainability 2015, whr is th ttal capital cst f th installd pwr gnratin systm (US$kW 1, I is th capital salvag factr t b paid n th unit f brrwd capital and f is th capacity factr, which is assumd qual t 80%. Th capital salvag factr (I can b calculatd frm [17]: L 1 i1 i I L 12 1 i (23 1 Whr L is th liftim f th pwr gnratin systm (yars, r th prid in which th brrwd capital has t b paid back (assumd t b 20 yars, and i is th annual intrst rat, assumd t b cnstant during th liftim f th systm, r th prid f th lan rpaymnt. Fr ful cst F, th fllwing Equatin can b applid [17]: Als, th xtrnal cst f air pllutin A can b btaind frm [17]: A m F Ful st (24 NO ( A, NO m O ( A, O m O ( 2 A, O 2 I W whr m NO,m O, m O ar th xhaust mass flw rats f nitrgn mnxid, carbn mnxid and 2 carbn dixid (kgs 1, and A,NO, A,O, A,O2 ar th intrnalizd xtrnal cst f air pllutin fr nitrgn mnxid, carbn mnxid and carbn dixid, rspctivly (US$kg 1. Fr th cas f a HP I ngin, which prducs pwr and hat, a bilr is assumd t prduc th sam amunt f hat. As a rsult, th csts f initial invstmnt, pratin and maintnanc, ful and als th intrnalizd xtrnal cst f air pllutin fr th assumd bilr can b rducd frm th cst f lctricity as fllws [17]: E ( 1 O F A - ( Fr a simpl I ngin, th cst f installatin is apprximatly 300 US$kW 1, and th cst f pratin and maintnanc is stimatd t b US$kW 1 [18,19]. Fr a HP I ngin, th cst f installatin is cnsidrd t b 385 US$kW 1, and th cst f pratin and maintnanc is assumd t b US$kW 1 [18,19]. Th xtrnal cst f nitrgn mnxid, carbn mnxid and carbn dixid ar stimatd t b 8.175, and US$kg 1, rspctivly [16,17]. In this analysis, thr pllutin surcs, such as watr and sil, prducd by an pratinal pwr gnrating systm ar ignrd. It is imprtant t nt that ths csts vary frm n rgin r cuntry t anthr, mainly bcaus f diffrncs rlatd t paramtrs such as rat f pllutants prductin, laws r nvirnmntal standard limits. Als, ths valus may b affctd in th futur by law r standard limit changs. 4. Rsults and Discussin Fr systm simulatin, a cmputr cd is writtn with th FORTRAN languag. Fr validatin, th cd utput data is cmpard with data rprtd fr th sam mdl I ngin installd in th campus f Khjnasir Univrsity. Th man rrr is abut 5.7%, which is rasnabl fr this rsarch. Tabl 4 shws cmparisn btwn xprimnt and mdl. Th systm installd in Khajnasir Univrsity prducd 130 and 204 kw nminal lctrical and thrmal pwr, rspctivly. In this systm, natural 1 O F A assumd nt bilr (25 (26

9 Sustainability 2015, gas ful ngin was cupld with lctrical gnratr by flxibl jint. Bth mtr and gnratr ar installd in cmmn fundatin. Air/ful rati can b rgulatd by carburtr and lctrical gvrnr. Schmatic diagram f this systm is shwn in Figur 2 [20]. Tabl 4. mparisn btwn mdl and xprimntal data fr ra = 1.5. Mdl Exprimntal η I, Simpl η I, HP Figur 2. Schmatic diagram f I ngin installd in Khajnasir Univrsity. Fr cling f I ngin, watr was usd ac cling fluid. First watr was circulatd in clsd lp in rdr t absrb hat frm I ngin. Thn watr ntrd th xhaust gas hat xchangr t absrb thrmal nrgy frm xhaust gas. Schmatic diagram f HP hat xchangr is shwn in Figur 3 [17]. Figur 3. Schmatic diagram f xhaust gas hat xchangr. All f th systm paramtrs, such as inlt and utlt cling watr tmpratur and prssur, inlt and utlt watr tmpratur in HP hat xchangr, ful prssur, lctrical pwr utput, watr, air and ful mass flw rats, ar shwn in th cntrl panl (Figur 4.

10 Sustainability 2015, Figur 4. Systm cntrl panl. Th variatins f first law fficincy with xcss air rati fr simpl and HP intrnal cmbustin ngins ar shwn in Figur 5. Th frm f th graph suggsts that by incrasing xcss air rati, th simpl I ngin first law fficincy is incrasd but, fr th typ f cmbind pwr and hat prductin, this fficincy dcrass. η I (% Simpl HP r a Figur 5. Variatin f first law fficincy with xcss air rati fr simpl and HP (cmbind hat and pwr intrnal cmbustin ngins at inlt air tmpratur f 15. By incrasing air/ful rati, tw ppsit ffcts can b sn: (1 Incrasing air/ful rati mixtur mass flw rat. (2 Rductin cmbustin tmpratur. Effct 1 can incras utput pwr and ffct 2 can dcras n. In simpl I ngin cmbinatin f ths tw affcts lads t incras in first law fficincy. But in HP I ngin, bsids tw prvius ffcts, tw thr ffcts can b cnsidrd: (1 Incrasing xhaust mixtur mass flw rat, that it causs incras hat xchangr fficincy. (2 Rduc xhaust mixtur tmpratur that it causs rductin in hat xchangr fficincy. But itm 2 has mr ffcts than itm 1, s it lads t dcras HP I ngin fficincy by incras mlar air ful rati.

11 Sustainability 2015, Th variatins f ntrpy gnratin with xcss air rati fr simpl and HP intrnal cmbustin ngins ar shwn in Figur 6. Du t th rcvrd hat in watr jackt and xhaust gas hat xchangrs, ntrpy gnratin in th HP md is lwr than that in a simpl intrnal cmbustin ngin. By incrasing th xcss air rati, th systm ntrpy gnratin is dcrasd in bth simpl and HP intrnal cmbustin ngins. T btain highr xcss air ratis th air mass flw rat will b incrasd whil th ful mass flw rat rmains cnstant. This incras causs th fllwing ffcts: (1 Incras in cnsumd cmprssin wrk. (2 Dcras in cmbustin tmpratur. (3 Incras in prducd xpansin wrk. (4 Incras in ttal mass flw rat t th I ngin ( m a m f nt utput pwr., which rsults in an incras in th In a simpl I ngin, th cmbinatin f ths ffcts lads t a cnsidrabl dcras in ntrpy gnratin whn th xcss air rati is incrasd. In a HP I ngin th incras in th ttal mass flw rat (air and ful mass flw rats incrass th ffctivnss f bth hat xchangrs; hnc th rductin in ntrpy gnratin is gratr than that in a simpl I ngin. Ṡgn(kW/K Simpl HP r a Figur 6. Variatin f ntrpy gnratin with xcss air rati fr simpl and HP intrnal cmbustin ngins at an inlt air tmpratur f 15. Figur 7 shws th variatin f lctricity cst (bjctiv functin with inclusin and xclusin f th xtrnal cst f air pllutin with xcss air rati fr a simpl and HP I ngins at an inlt air tmpratur f 15. Elctricity cst is rgardd as th bjctiv functin fr cmputing th lctricity cst fr an I ngin. This functin cnsists f fur main parts: initial, pratin and maintnanc, ful csts as wll as th xtrnal cst f air pllutin. This cst is addd t th initial, pratin and maintnanc and ful csts. Ful cst and th xtrnal cst f air pllutin dpnd n mlar air-ful rati du t a variatin f air pllutin and th first law fficincy (Equatins (23 and (24, sinc ths paramtrs ar affctd by mlar air-ful variatin. It can b sn frm Figur 7 that by incrasing th air-ful rati, th lctricity cst dcrass in bth cass (inclusin and xclusin scial cst air pllutin. Th avrag lctricity cst with inclusin th scial cst f air pllutin incrass 41% cmpard t whn th lctricity cst xcluds th scial cst f air pllutin. In this rsarch th highst valu f th mlar air-ful rati is cnsidrd t b 2, bcaus at highr mlar air ful ratis cmbustin will nt b achivd. In fact whn flammability limits ar bsrvd th xcss air rati f 4 is ptimum valu. Fr HP kind, th shap f that graph is similar t that fr a simpl I ngin;

12 Sustainability 2015, hwvr this graph has a stpr slp. Th cst f lctricity fr th HP I ngin is lss than fr th simpl n du t th rductin f th hat rcvry hat cst frm th cst f lctricity. ntrary t xrgy, th ptimum valu fr lctricity cst (bjctiv functin has rginal valus bcaus th xtrnal cst f air pllutin dpnds n lcatin f th plant and tim f pratin. Figur 7. Variatin f lctricity cst (with and withut inclusin f th xtrnal cst f air pllutin with xcss air rati fr a simpl and HP I ngins at an inlt air tmpratur f nclusins Exrgy, cnmic and nvirnmntal analyss ar prfrmd fr simpl and HP I ngins, including valuatin f ntrpy prductin, scnd law fficincy, and nrgy csts. Th analysis includs th xtrnal cst f th nvirnmntal pllutin frm O2, O and NO prsnt in th xhaust flu gas f th I ngins. Th fllwing cnclusins ar drawn: Entrpy gnratin in th HP intrnal cmbustin ngins is 30% lwr than that in a simpl ngin. An incras in xcss air rati dcrass ntrpy gnratin in simpl and HP ngins. Th maximum prtin f ntrpy gnratin in a HP ngin is rlatd t th I ngin, and th xhaust gas hat xchangr typ gnrats mr ntrpy than th cling watr jackt hat xchangr typ. Whn cnsidring th xtrnal cst f air pllutin, fr a simpl I ngin, th inlt air tmpratur has a ngligibl ffct n th lctricity cst, but in a HP I ngin, this ffct is cnsidrabl. Th nvirnmntal aspcts ar strngly dpndnt n lcatin f th plant and tim f ngin pratin.

13 Sustainability 2015, Authr ntributins Mhdi Alihyai dsignd and carrid ut th majrity f th rsarch with Mhammad Khrshidvand. Marc A. Rsn and Faridh Atabi cpratd in th rsarch, prviding input thrughut and rviwing dtails. All authrs rad and apprvd th final manuscript. nflicts f Intrst Th authrs dclar n cnflicts f intrst. Rfrncs 1. Abusglu, A.; Kanglu, M. First and scnd law analyss f Disl ngin pwrd by cgnratin systms. Enrgy nvrs. Manag. 2008, 49, Abusglu, A.; Kanglu, M. Exrgtic and thrm-cnmic analyss f Disl ngin pwrd cgnratin: Part 1 Frmulatins. Appl. Thrm. Eng. 2009, 29, Abusglu, A.; Kanglu, M. Exrgtic and thrm-cnmic analyss f disl ngin pwrd cgnratin: Part 2 Applicatin. Appl. Thrm. Eng. 2009, 29, Alkidas, A.. Th applicatin f availability and nrgy balancs t a Disl ngin. Trans. ASME J. Eng. Gas Turbins Pwr 1988, 110, Danv, S.N.; Gupta, A.K. Mdling th prfrmanc charactristics f Disl ngin basd cmbind-cycl pwr plants part II: Rsults and applicatins. Trans. ASME J. Eng. Gas Turbins Pwr 2004, 126, Kanglu, M.; Isik, S.K.; Abusglu, A. Prfrmanc charactristics f a disl ngin pwr plant. Enrgy nvrs. Manag. 2005, 46, Balli, O.; Aras, H.; Hpbasli, A. Thrmdynamic and thrm-cnmic analyss f a trignratin (TRIGEN systm with a gas-disl ngin: Part I Mthdlgy. Enrgy nvrs. Manag. 2010, 51, Balli, O.; Aras, H.; Hpbasli, A. Thrmdynamic and thrm-cnmic analyss f a trignratin (TRIGEN systm with a gas-disl ngin: Part II An applicatin. Enrgy nvrs. Manag. 2010, 51, Fua, J.; Liub, J.; Rna,.; Wangd, L.; Dngb, B.; Xua, Z. An pn stam pwr cycl usd fr I ngin xhaust gas nrgy rcvry. Enrgy 2012, 44, Ehyai, M.A.; Ahmadi, P.; Atabi, F.; Hibati, M.R.; Khrshidvand, M. Fasibility study f applying intrnal cmbustin ngins in rsidntial buildings by xrgy, cnmic and nvirnmntal analysis. Enrgy Build. 2012, 32, Rqu Díaz, P.; Bnit, Y.R.; Paris, J.A.R. Thrmcnmic assssmnt f a multi-ngin, multi-hat-pump HP (cmbind cling, hating and pwr gnratin systm A cas study. Enrgy 2010, 44, AMDA Hm Pga. Availabl nlin: (accssd n 8 March Niminn, J.; Dincr, I. mparativ xrgy analyss f gaslin and hydrgn fulld IEs. Int. J. Hydrg. Enrgy 2010, 35,

14 Sustainability 2015, Huang, F.F. Prfrmanc assssmnt paramtrs f a cgnratin systm. In Prcdings f EOS 96, Stckhlm, Swdn, Jun Bjan, A. Advancd Enginring Thrmdynamics; Jhn Wily & Sns: Nw Yrk ity, NY, USA, Hrngrn,.T. st Accunting: A Managrial Emphasis; Prntic-Hall: Englwd liffs, NJ, USA, Brnw, S.S.; Marrn, D.B. Valuatin f Envirnmntal Extrnalitis fr Enrgy Planning and Opratins; Tllus Institut: Bstn, MA, USA, Ehyai, M.A.; Mzafari, A. Enrgy, cnmic and nvirnmntal (3E analysis f a micr gas turbin. Enrgy Build. 2010, 42, Mzafari, A.; Ehyai, M.A. Optimizatin f micr gas turbin by xrgy cnmic and nvirnmntal (3E analysis mplyd fr n-sit cmbind hat and pwr prductin. Int. J. Exrgy 2010, 7, Ehyai, M.A.; Bahadri, M.N. Slctin Optimum as f Disprsd Pwr Gnratin in Diffrnt limat nditin f Iran by Exrgy, Ecnmic and Envirnmntal Analyss; Sharif Univrsity f Tchnlgy: Thran, Iran, by th authrs; licns MDPI, Basl, Switzrland. This articl is an pn accss articl distributd undr th trms and cnditins f th rativ mmns Attributin licns (