Optimum Sizing of a PV-Battery-Diesel Hybrid System for Remote Consumers

Transcription

1 Third Iteratial Cferece Applied Eergy May Perugia, Italy Dimitris Zafirakis, Ksmas Kavadias, Emilia Kdili, Jh Kaldellis Optimum Sizig f a PV-battery-Diesel Hybrid System fr Remte Csumers pages -mm Optimum Sizig f a PV-Battery-Diesel Hybrid System fr Remte Csumers Dimitris ZAFIRAKIS 1, Ksmas KAVADIAS 1, Emilia KONDILI 2, Jh KALDELLIS 1 1 Lab f Sft Eergy Applicatis & Evirmetal Prtecti, TEI f Piraeus 2 Optimisati f Prducti Systems Lab, TEI f Piraeus jkald@ teipir.gr; URL: Tel , FAX P.O. Bx 41046, Athes 12201, Greece Abstract O the umerus small ad medium-sized Greek islads f the Aegea ad Iia Archipelags e may ecuter several thusads f remte csumers uable t appreciate a direct electricity utility supply. Fr this purpse, remte csumers usually cver their electricity eeds based the perati f small diesel-geeratr sets. O the ther had, mst f these areas appreciate high quality slar ptetial that cmprises a stimulus fr the use f stad-ale phtvltaic (PV)-based cfiguratis. I this ctext, the primary bjective f the preset study is t determie the ptimum dimesis f a stad-ale PV-diesel system, uder the restricti f miimum lg-term electricity geerati cst, ad accrdigly btai a cmparis with diesel-ly systems. Keywrds Slar eergy, stad-ale system, fuel csumpti, electricity geerati cst, Greece Itrducti Autmus phtvltaic (PV)-diesel systems cmprise e f the mst iterestig ad evirmetally friedly techlgical slutis fr the electrificati f islated csumers r eve etire rural areas [1]. I this ctext, the umerus small ad medium-sized islads f the Aegea ad Iia Archipelags e may ecuter several thusads f remte csumers uable t appreciate a direct electricity utility supply, this fte leadig t the use f small diesel-geeratr sets r rather seldm t the use f stad-ale wid-based cfiguratis [2] i case f appreciable wid ptetial. O the ther had, all these islads are lcated i regis with abudat slar ptetial. I a attempt t miimize the il depedecy ad imprve the life-quality f islated csumers, the idea f creatig a cmbied PV-diesel hybrid system with the existece f a eergy strage device is ivestigated. The primary bjective f the curret study is t determie the ptimum dimesis f a apprpriate stad ale PV-diesel system, able t cver the eergy demad f remte csumers, uder the restricti f miimum lg-term electricity geerati cst [3]. Fr this purpse a itegrated cst-beefit mdel is develped frm first priciples, able t estimate the fiacial behaviur f similar applicatis a lg-term peratial schedule. Jh Kaldellis: jkald@teipir.gr, ,

2 Third Iteratial Cferece Applied Eergy May Perugia, Italy Prblem descripti ad prpsed sluti The prblem t be slved i the curret paper is first t determie ptimum PV-based hybrid cfiguratis based the criteri f miimum lg-term electricity geerati cst ad secdly t btai a direct cmparis f these cfiguratis with the respective diesel-ly sluti. I this ctext, a typical hybrid PV-battery-diesel system able t meet the electricity eeds f a remte csumer (Figure 1) csists f (Figure 2): Typical Weekly Electricity Demad Prfile Witer Csumpti Summer Csumpti 3000 Lad Demad (W) Time (hurs) Figure 1: Lad demad prfile f a typical remte csumer i. A PV system f "z" paels ("N + " maximum pwer f every pael) prperly cected t feed the charge ctrller at the vltage required. ii. A lead acid battery strage system fr "h " hurs f autmy, r equivaletly with ttal capacity f "Q max ", perati vltage "U b " ad maximum discharge capacity "Q mi " (r equivaletly maximum depth f discharge "DOD L "). iii. A DC/DC charge ctrller f "N c " rated pwer ad chargig vltage "U CC ". iv. A DC/AC iverter f maximum pwer "N iv " able t meet the csumpti peak lad demad, takig als it accut a apprpriate security margi. v. A small iteral cmbusti egie f "N d " (kw), able t meet the csumpti peak lad demad "N p " (i.e. N d N p ), where "N p " is the maximum lad demad f the csumpti (based the use f a typical electricity demad prfile f a remte csumer), icludig a safety margi (e.g. 30%) ad als csumig a predefied il quatity "M f ", ragig frm M f =0kg/year t M f =M fmax, i.e. whe the etire eergy demad is cvered by the dieselegie. Figure 2: Typical PV-battery-diesel hybrid system 2

3 Third Iteratial Cferece Applied Eergy May Perugia, Italy Hece, as it may accrue, there are tw resultig extreme cases, i.e. either a diesel-ly system r a stad-ale PV-battery system with zer diesel-il ctributi. Subsequetly, it shuld be ted that all cfiguratis examied shuld be able t cver the eergy eeds f the remte csumer withut lad rejectis [4] durig a etire year perid (E t =4,73MWh). T cfrt similar prblems ad prduce eergy autmus PV-based hybrid cfiguratis, a cmputatial algrithm "PV-DIESEL III" has bee develped [5] as a extesi f the already preseted "PHOTOV-III" umerical cde [6] (Figure 3). START zi, Q i, Mf i, z, Q, Mf, t, t, z FIN, Q FIN, M ffin Mf=Mf Mf Mf = M fi z =z + z z=zi Q=Q+ Q Q QF IN Q=Q i t=t+ t t=0 Meterlgical Data, i.e. Slar Radiati, Ambiet Temperature Remte Csumer Eergy Dem ad, N D(t) PV Geeratr Pwer Curve NPV=NPV(t) ND Via Iverter N PV NPV >ND NPV =0 Eergy Strage N= ND-NPV N=NPV-N D Battery Empty? Battery Empty? T Lw Pririty Lads Battery F ull? N O Eergy is Stred t the Battery via Charge Ctrller N is cvered by Battery via Charge Ctrller ad Iverter ND is cvered by Battery via Charge Ctrller ad Iverter t > t Q*=Q z z FIN (z-q*) curve Mf Mf FIN PHOTOV-DIESEL III Algrithm END Figure 3: The PV-DIESEL III umerical algrithm 3

4 Third Iteratial Cferece Applied Eergy May Perugia, Italy The algrithm is used t carry ut the ecessary parametrical aalysis a hurly eergy prducti-demad basis. Mre precisely, give the "M f " value fr each "z" ad "Q max " pair, the "PV-DIESEL III" algrithm is executed fr the etire time-perid selected (e.g. e year), while emphasis is laid btaiig zer-lad rejecti perati. Fllwig the itegrati f the eergy balace aalysis, a (z-q * ) curve is predicted uder a give diesel-il quatity "M f ". Keep i mid that fr every pair f (z-q * ) the stad-ale hybrid PV-based system is eergy autmus fr the perid ivestigated, usig hwever a predefied diesel-il quatity "M f ". Fially, the ptimum pair may be selected frm every (z-q * ) curve, the basis f a ptimizati criteri set, curretly beig the miimum lg-term peratial cst f the istallati. Estimati f the lg term electricity prducti cst The preset value f the etire ivestmet cst f a hybrid PV-diesel pwer system (after - years f perati) is a cmbiati [7] f the iitial istallati cst ad the crrespdig maiteace ad perati (M&O) cst, csiderig als the ivestmet residual value; all quatities expressed i preset (cstat) values. As already ackwledged i previus wrks [8], the iitial ivestmet cst "IC " icludes the market (ex-wrks) price f the istallati cmpets (i.e. PV-paels, "IC PV "; battery, "IC bat "; diesel-electric geeratr, "IC d " ad electric devices "IC el ", icludig iverter, UPS, rectifier ad charge ctrller cst) ad the crrespdig balace f the plat cst, expressed as a fracti "f" f the PV paels market price. Thus e may write: IC IC IC IC IC f IC (1) PV d bat elec PV Usig the market aalysis data [7], equati 1 fially reads: IC P z N r (1 f ) Q 1 max N d N 1 p b ( z N ) (2) where " " is a fucti f "z" (i.e. (z)), expressig the scale ecmies fr icreased umber f PV paels utilized. I the preset case (z 100), is take equal t e. Subsequetly "Pr" is the specific buy-cst [9] f a PV pael (geerally P r = P r (z.n + )) expressed i /kw p, while " " is the respective diesel geeratr cst (250 /kw). Additially, the parameters " " (483 /kw), " " (0.083) ad "b" (380 /kw) describe the cst f the majr electric devices, beig geerally a fucti f the peak lad demad (e.g. iverter) ad the PV mdules rated pwer (e.g. charge ctrller) respectively, while the parameters " " ad " " describe the battery bak purchase cst (5.04 /Ah ad respectively). Durig lg-term perati, the M&O cst ca be split [7] it the fixed "FC " ad the variable "VC " M&O cst. I the preset aalysis, the fixed M&O cst als csiders the fuel cst csumed by the dieselelectric geeratr. Geerally speakig, the aual fixed M&O cst ca be expressed as a fracti "m" f the iitial capital ivested, further icludig a aual iflati rate equal t "g m ", describig the aual chages f labr cst ad the crrespdig spare parts, embracig als ay lubricats csumpti. Subsequetly, the fuel csumpti cst results by the aual diesel-il quatity csumed "M f ", the curret fuel price "c f " (1.1 /kg) ad the il price aual escalati rate "e f ". Thus e gets: FC c f m IC M f (1 e (1 g f m ) (1 i) ) (1 i) [1 (1 g [1 (1 e f ) m ) /(1 i) /(1 i) ]/( i e ]/( i g f ) m ) (3) 4

5 Third Iteratial Cferece Applied Eergy May Perugia, Italy where "i" is the retur ivestmet idex. The variable M&O cst "VC " maily depeds the replacemet f "k " majr parts f the istallati, which have a shrter lifetime " k " tha the cmplete istallati. Usig the symbl "r k " fr the replacemet cst cefficiet f each "k " majr part (battery, diesel-electric geeratr, iverter, charger, etc.) the "VC " term ca be expressed as: VC IC k k k k ( l k ) (1 gk ) (1 k ) (1 i) }, rk { (4) k 1 l l l 1 l where "l k " is the iteger part f [( 1) / k ], while "g k " ad " k " describe the mea aual chage f the price ad the crrespdig techlgical imprvemet level fr the k-th majr cmpet f the system. I the preset aalysis e may take it accut the diesel-electric geeratr, the battery bak ad the iverter ad charger replacemet every " d " " b " ad " e " years respectively (e.g. d 4 6, b 5 7 ad e 10 years). Usig the abve aalysis ad csiderig that the prpsed PV-diesel system perates fr "" years, e may estimate the crrespdig ttal peratial cst "C " by cmbiig the iitial cst ad the fixed ad variable M&O cst, i.e.: C IC ( 1 ) FC VC Y (5) I equati 5 "Y " represets the residual value f the ivestmet, attributed t amuts recvered at the "-th" year f the hybrid system service perid (e.g. value f lad r buildigs, scrap r secd had value f equipmet, etc.), alg with the experiece gaied ad the crrespdig techlgical kw-hw. Fially, " " is the subsidy percetage (e.g. 30%-50%) prvided (uder specific precditis) by the Greek State, accrdig t the develpmet law i frce (e.g. 3299/04 ameded by 3522/2006) r the crrespdig Natial Operatial Cmpetitiveess Prgram [10]. Lastly, takig als it accut the aalysis preseted i [11], ccerig the curret electricity margial prducti cst "c e ", e gets the fllwig equatis prvided that the et preset value f the ivestmet becmes equal t the crrespdig residual value (NPV=Y, where Y may be equal t zer) after - years f perati, i.e. c e C ( z 1), where z (1 p) /(1 i) (6) E z ( z 1) t ad "p" is the prduced electricity mea aual escalati rate, e.g. p=3%. Besides, e shuld als bear i mid that the prpsed mdel als icludes the diesel-ly sluti (i.e. IC.N d, z=0, M f =M max ) as well as the zer-diesel cfigurati (i.e. IC d =0, M f =0). Applicati Results The abve preseted methdlgy is the applied t a represetative islad f the Iia Sea, amely Zakiths. Zakiths is a medium-small size islad that pssesses very high slar ptetial (~1600kWh/m 2.year, Figure 4) ad mderate wid speeds, hece the applicati f PV-based systems is desigated as the mst prmisig electrificati sluti fr remte csumers. Applyig the PV-DIESEL III algrithm fr a umber f M f cases, e may btai the results f Figure 5. Mre precisely, i Figure 5 e may btai several eergy autmy curves, each e icludig a umber f eergy autmus (Q max -z) cmbiatis ad crrespdig t a aual fuel csumpti ragig frm M f =0kg/year t M f =1000kg/year. Accrdigly, by usig the calculati prcedure f the previus secti e may result t the 5

6 Third Iteratial Cferece Applied Eergy May Perugia, Italy estimati f the lg-term electricity geerati cst "c e " f all the (Q max -z) cfiguratis icluded i Figure 5, fr bth 10 ad 20 years f perati respectively. 250 Slar Ptetial i the Area f Zakiths Slar Eergy per Mth at the Hriztal Plae (kwh/m 2 ) Jauary February March April May Jue July August Mth f the Year September Octber Nvember December Figure 4: Slar ptetial at the islad f Zakiths Autmus Eergy Cfiguratis fr Zakiths Islad Battery Capacity (Ah) Mf=0kg/year Mf=100kg/year Mf=200kg/year Mf=500kg/year Mf=1000kg/year Number f PV Paels (z) Figure 5: PV-based hybrid eergy autmus cfiguratis fr Zakiths The results f the cst aalysis are give i Figures 6-7, icludig als the electricity geerati cst "c e " f the diesel-ly sluti (i.e. M f =M fmax ), while by settig the ptimizati criteri f miimum lg-term electricity geerati cst, ptimum PV-based hybrid eergy cfiguratis may be evetually desigated. As it may be ccluded, by allwig the umber f PV paels t icrease up t a certai pit the electricity geerati cst cstatly decreases reachig a miimum value. Further tha that pit hwever, battery capacity required des t decrease (Figure 5) ad thus ay icrease f the PV pwer has a direct impact the icrease f the electricity geerati cst. O the ther had, by icreasig the aual fuel csumpti, the electricity geerati cst presets cstat reducti up t the pit that the uecessary icrease f PV paels (i.e. whe the curve heads upwards, fr 6

7 Third Iteratial Cferece Applied Eergy May Perugia, Italy z>150) bscures ay ther cst cmpet ad thus the ifluece f the M f parameter miimizes. Regardig the cmparis betwee the diesel-ly sluti ad the prpsed cfigurati, as it may be draw frm Figures 6-7, the prpsed sluti is margially csteffective fr 10 years f perati, with results beig csiderably imprved i the case f 20 years. Te-Year Electricity Prducti Cst (Eurs/kWh) Zakiths Islad PV-Diesel Stad-Ale System 10-year Cst Aalysis - Prducti Cst ( =50%) Mf=0kg/year Mf=200kg/year Mf=1000kg/year Mf=100kg/year Mf=500kg/year Mf=Mfmax Number f PV paels (z) Figure 6: Te-year electricity geerati cst fr varius "Mf" cases 5 Zakiths Islad PV-Diesel Stad-Ale System 20-year Cst Aalysis - Prducti Cst ( =50%) Mf=0kg/year Mf=100kg/year Twety-Year Electricity Prducti Cst (Eurs/kWh) Mf=200kg/year Mf=1000kg/year Mf=500kg/year Mf=Mfmax Number f PV paels (z) Figure 7: Twety-year electricity geerati cst fr varius "Mf" cases This is better illustrated i Figure 8, where the miimum ttal-lg term cst "C " cfiguratis are give, icludig als the M f =M fmax case. Nte that althugh a miimum ptimum is achieved i the 10-year case fr M f =1000kg/year (C 10-mi =26,278 ad c e10- mi=0.715 /kwh fr Q max =450Ah ad z=56) the crrespdig value fr the 20-year sceari drps t M f =500kg/year (C 20-mi =39,203 ad c e20-mi =0.657 /kwh fr Q max =600Ah ad z=80), desigatig the icreased utilizati f the PV paels value if the etire lifetime is csidered. I fact, with regards t the 20-year sceari, ly i the case that the PV-ly sluti 7

8 Third Iteratial Cferece Applied Eergy May Perugia, Italy (M f =0kg/year) is adpted is the prpsed system cst-ieffective, while eve if a miimum fuel csumpti is take it accut, i.e. M f =100kg/year, the electricity geerati cst f the prpsed sluti may beat the respective f the diesel-ly pti Miimum Cst Cfiguratis Vs Diesel-Oly Sluti Ttal Cst f the Istallati fr =10,20 years Te-Year Ttal Cst Twety-Year Ttal Cst Optimum Pits Mf=Mfmax Mf=Mfmax Aual Fuel Csumpti Mf (kg/year) Cclusis Figure 8: Optimum ttal cst cfiguratis fr 10- ad 20-year perati I cclusi, if csiderig the etire life service f the istallati (i.e. =20), which may equally well exted frm 20 t 30 years f perati fr the PV techlgy, ptimum size cfiguratis suggestig cst-effective slutis may derive fr umerus remte csumers fud i areas with csiderable slar ptetial. Furthermre, takig als it accut the prgress met i the PV techlgy alg with the gradual prcuremet cst reducti, the electricity geerati cst f similar PV-based hybrid istallatis may be further reduced, thus presetig a mre cutable advatage ver the up t w cmmly adpted diesel-ly sluti. Recapitulatig, a ptimum sizig methdlgy is curretly develped fr PV-based hybrid cfiguratis, usig the criteri f miimum lg-term electricity geerati cst. Frm the results btaied fr the typical remte csumer ad the high quality slar ptetial area ivestigated, it accrues that by usig the develped methdlgy e may result t eergy autmus ptimum-size cfiguratis that may -uder certai cditis- beat the curret electricity prducti cst f diesel-ly systems. Nmeclature b: Cst cefficiet f majr electric devices [ /kw] c e : Electricity margial prducti cst [ /kwh] c f : Fuel il price [ /kg] C : Ttal peratial cst f the system after years f perati [ ] DOD L : Maximum depth f discharge e f : Aual escalati rate f fuel il E t : Aual eergy demad [MWh] f: Balace f the plat cst cefficiet FC : Fixed maiteace ad perati cst [ ] g k : Price iflati f majr system cmpets 8

9 Third Iteratial Cferece Applied Eergy May Perugia, Italy g m : Aual iflati rate f maiteace ad perati h : Hurs f eergy autmy [h] i: Retur ivestmet idex IC bat : Battery bak iitial ivestmet cst [ ] IC d : Diesel egie iitial ivestmet cst [ ] IC el : Electric devices iitial ivestmet cst [ ] IC : System iitial ivestmet cst [ ] IC PV : PV paels iitial ivestmet cst [ ] k : Idex f majr istallati cmpets requirig replacemet l k : Times f replacemet f majr system cmpets m: Cefficiet f fixed maiteace ad perati cst M f : Aual quatity f il used [kg] M fmax : Maximum aual quatity f il used [kg] : Service perid f the istallati [years] N + : Maximum pwer utput f each PV pael [W] b : Service perid f the battery bak [years] N c : Rated pwer f the charge ctrller [kw] N d : rated pwer f the diesel egie [kw] d : Service perid f the diesel egie [years] e : Service perid f the electric devices [years] N iv : Rated pwer f the iverter [kw] k : Lifetime f a majr system cmpet [years] N p : Peak lad demad [kw] NPV: Net preset value [ ] p: Mea aual escalati rate f electricity price P r : Specific buy cst f PV paels [ /kw] Q max : Maximum battery strage capacity [Ah] Q mi : Miimum battery strage capacity [Ah] r k : Replacemet cst cefficiet f a majr system cmpet U b : Battery vltage perati [Vlts] U CC : Chargig vltage f the charge ctrller [Vlts] VC : Variable maiteace ad perati cst [ ] Y : Residual value f the ivestmet [ ] z: Number f PV paels : State subsidy f the iitial ivestmet cst : Cefficiet f scale ecmies fr PV paels : Cst cefficiet f majr electric devices [ /kw] : Cst cefficiet f the battery bak [ /kw] k : Techlgy imprvemet cefficiet f majr cmpets : Cst cefficiet f majr electric devices : Specific buy cst f the diesel egie [ /kw] : Cst cefficiet f the battery bak 9

10 Third Iteratial Cferece Applied Eergy May Perugia, Italy Refereces [1] Shaahid S.M., El-Ami I., 2009, Tech-ecmic evaluati f ff-grid hybrid phtvltaic diesel battery pwer systems fr rural electrificati i Saudi Arabia-A way frward fr sustaiable develpmet, Reewable ad Sustaiable Eergy Reviews, Vl 13, N 3, pp [2] Kaldellis J.K., ed., 2010, Stad-Ale ad Hybrid Wid Eergy Systems: Techlgy, Eergy Strage ad Applicatis, Wdhead Publishig, Cambridge, ISBN [3] Kaldellis J.K., Kdili E., Filis A., 2006, Sizig a hybrid wid-diesel stad-ale system the basis f miimum lg-term electricity prducti cst, Applied Eergy, Vl 83, N 12, pp [4] Kaldellis J.K., Krakis P., Kavadias K., 2004, Eergy Balace Aalysis f a Stad- Ale Phtvltaic System, Icludig Variable System Reliability Impact, Reewable Eergy, Vl 29, N 7, pp [5] Kaldellis J.K., 2010, Optimum hybrid phtvltaic-based sluti fr remte telecmmuicati statis, Reewable Eergy, Vl 35, N 10, pp [6] Kaldellis J.K., Kavadias K.A., Krakis P.S., 2007, Cmparig Wid ad Phtvltaic Stad-Ale Pwer Systems Used fr the Electrificati f Remte Csumers, Reewable ad Sustaiable Eergy Reviews, Vl 11, N 1, pp [7] Kaldellis J.K., 2004, Optimum Techecmic Eergy-Autmus Phtvltaic Sluti fr Remte Csumers thrughut Greece, Eergy Cversi ad Maagemet, Vl 45, N 17, pp [8] Kaldellis J.K, Gavras T.J., 2000, The Ecmic Viability f Cmmercial Wid Plats i Greece. A Cmplete Sesitivity Aalysis, Eergy Plicy, Vl 28, N 8, pp [9] Hffma W., 2006, PV slar electricity idustry: Market grwth ad perspective, Slar Eergy Materials ad Slar Cells, Vl 90, N 18-19, pp [10] Kaldellis J.K., 2002, A Itegrated Time-Depedig Feasibility Aalysis Mdel f Wid Eergy Applicatis i Greece, Eergy Plicy, Vl 30, N 4, pp [11] Vlachs G.Th, Kaldellis J.K., 2004, Applicati f gas-turbie exhaust gases fr brackish water desaliati: a tech-ecmic evaluati, Applied Thermal Egieerig, Vl 24, N 17-18, pp