Variation of Mean Hourly Insolation with Time at Jos

Transcription

1 OR Jurnal f Envirnmenal cience, Txiclgy and Fd Technlgy (OR-JETFT) e-n: ,p- N: Vlume 9, ue 7 Ver. (July. 015), PP Variain f Mean urly nlain wih Time a J 1 Ad Mua, Babangida Alkali and 3 Yakubu Umar 1, Deparen f Phyic, Cllege f Educain, Azare 3 Deparen f cience Labrary Technlgy, Federal Plyechnic, Naarawa Abrac: 5year daa n mean daily glbal radiain fr J, Nigeria, were ued udy hw he hurly glbal radiain varie ver a ypical day a J. Empirical frmulae were ued in he analyi. The irradiance a lar nn wa fund have a maximum value f 3.81 MJm in February and a minimum value f. MJm in July, wih an average value f MJm ver he 5year perid examined. Wihin he ame perid, he hurly inlain varied frm 0.5 MJm a 7.00am 3.07 MJm a 1.00nn, wih an aumpin ha he day wa ymmerical abu he lar nn. average i 1.70±1.01 MJm ver a daylengh f 11hur. Thi equivalen a pwer upu f 470Wm, which implie ha wih a lar panel f m, ne culd bain a pwer upu f abu 1000W, crrepnding he pwer raing f an elecric irn r waer heaer n a 40V AC upply. The value f inlain bained in hi wrk rngly ugge ha lar energy culd be uilized in J and i envirn mee me energy need, a lea a he dmeic level. Key wrd: glbal radiain, empirical frmulae, irradiance, inlain, lar nn.. nrducin lar radiain play a very impran rle in ur life. The knwledge f lar radiain reaching he earh urface and i gegraphical diribuin i very impran fr lar energy and her applicain. The availabiliy f lar radiain daa i limied by he pariy f he exiing newrk. Bu meaured daa are raher care, and radiain daa fen have be eimaed frm empirical frmulae ha are available fr ha purpe. n hi paper, infrmain abu hurly glbal radiain i derived frm daily glbal radiain in rder acerain he viabiliy f uing lar device and appliance in J and i envirn.. Daa Acquiiin The daa e ued in hi paper wa bained frm he Nigerian Meerlgical Agency (NMET), Lag. Thee daa cnain recrd f mnhly mean daily value f glbal radiain fr he year 1995 and The recrd were f aipang airpr, near J. Thee daa are given in appendix A.. Mehd f Analyi Value f mean hurly glbal radiain, were calculaed frm he mean daily value, f glbal radiain uing empirical frmulae hrugh a cnverin facr, r, defined by: r (1) A demnraed by el and Whillier (1955), and by Liu and Jrdan (1960), r depend eenially n he hur angle and he unrie hur angle wih mrning piive and afernn negaive while. i a uni f ime, each hur equaling 15 f lngiude, i calculaed frm c 1 an an () laiude f lcain nrh piive and lar declinain, i.e. angular piin f he un a 9.95 fr J. can be calculaed lar nn wih repec he plane f he equar (nrh piive). frm he apprximae equain f Cper (1969) a: 3.45in360n 84/365 r frm Mlen (009) a: (3) 3.45in n / (4) DO: / Page

2 Variain f Mean urly nlain wih Time a J n i he day number cuning frm January 1 a 1and ending wih December 31 a 365, ha i 1 n 365. Cllare-Pereira and Rabl (1979) imprved hi crrelain, which allwed r be expreed a a funcin f he exraerrerial irradiain a: r a bc (5) where i he hur angle calculaed a he middle f he cnidered hur and he cefficien a and b are expreed a funcin f by: 3 a in 3 (6) b in (7) and are repecively he mnhly average f daily and hurly exraerrerial irradiain given by n d / (8) n d i1 n d i1 where n i he number f day in he cnidered mnh and d 4 x 3600 c n d (9) i given by (Duffie & Beckman, 1991): c n / 365 c c in in in (10) where he angle are expreed in radian. Fr he hurly exraerrerial hriznal irradiain, he exprein i (Nn, Muelli & Luche, 1996). 1 x 3600 c c n 365 c c in in in in (11) Ne ha r i imply he rai f he hurly al daily al hriznal irradiain. Tiwari (006) expreed i a: c c c r a bc (1) 4 in The mnhly mean hurly al hriznal irradiain ha been calculaed frm he mnhly mean daily al hriznal irradiain, uing equain (1) (1). Fr impliciy, he hurly al and he daily al exraerrerial irradiain, and repecively, were calculaed frm equain (10) and (11), uing fr n (he day f he year), value f he recmmended day fr which hwn in able 1. We adped a value f and = 1367 c are equal he mnhly average. Thee recmmended day are W / m fr he lar cnan (Tiwari, 006), and ued he crdinae f J a {9.95 N, 8.88 E, 1159m}. The declinain,, wa aken frm able 1 while he unrie (r une) hur angle, ω, wa calculaed frm equain (). The mean hurly inlain fr he lar nn ha been calculaed fr all mnh f he year fr he 5 year. Frm hi, he mean value f fr he 5 year were deduced. DO: / Page

3 Variain f Mean urly nlain wih Time a J Table 1: Recmmended Average Day fr Mnh and Value f n By Mnh. Fr he average day f he mnh Mnh n fr ih day Dae Day f year Declinain f mnh i n January February 31 + i March 59 + i April 90 + i May 10 + i June i July i Augu 1 +i epember 43 +i Ocber 73 +i Nvember 304 +i December 334 +i urce: Duffie and Beckman, V. Reul and Dicuin Maximum irradiance a lar nn Mnhly mean hurly value f maximum irradiance a lar nn have been calculaed hrughu he 5-year perid. The reul are preened in appendix B. Thi i illuraed in fig.1. can be een ha i generally higher during he dry ean. The maximum value ccur in February a abu value f. m MJ m decreae prgreively during he rainy ean, reaching a minimum MJ in July, afer which i rie again. The lwer value f during he rainy ean can be aribued he increaed abrpin f lar radiain by waer vapr in he aphere and he reflecin f lar radiain back pace by clud. Variain f hurly inlain wih ime f he day Value f average hurly inlain,, a lar nn and a each f he 5 hur n eiher ide f he lar nn have been calculaed, averaged and preened in appendix C. A graph f he variain f wih ime f he day i hwn in fig.. ha i maximum f 3.07 MJm a midday while he minima ccur a he beginning and a he end f he day. Ne he ymmery f abu he lar nn. V. Cncluin The hurly inlain a J wa fund, n he average, be 1.70 MJm Wm, equivalen a pwer raing f abu 470. Thi value f inlain i high enugh encurage he ue f lar energy device and appliance in J and i envirn, a lea a he dmeic level. V. Recmmendain n view f he ignificance f radiain ur biic envirnmen, we huld equip ur bervarie wih he lae and m reliable inrumen fr meauremen f lar radiain and her relaed quaniie. Furher reearch huld be cnduced n lar radiain n iled urface a J. DO: / Page

4 Variain f Mean urly nlain wih Time a J Fig. 1: Variain f wih mnh Fig. : Variain f wih ime f day Reference [1].C. el, and A. Whillier, Evaluain f fla plae lar cllecr perfrmance, Tranacin f he cnference n he ue f lar energy, The cienific Bai,, par, ecin A: , [] B.Y.. Liu, and R.C. Jrdan, The inerrelainhip and characeriic diribuin f direc, diffue and al lar inlain. lar Energy, 4, 1-19, [3] P.T. Cper, Abrpin f lar radiain in lar ill. lar Energy, 1 (3), [4] W.. Mlen, Mlen Weaher ain, uh Africa. hp:/range.ewcd.rg/e/mlw/radin.php, 009. [5] M. Cllare-Pereira and A. Rabl, The average diribuin f lar radiain: crrelain beween diffue and hemipherical and beween daily and hurly inlain value. lar Energy,, , [6] J.A. Duffie and W.A. Beckman, lar Engineering f Thermal Prcee. nd Ediin. Jhn Wiley and n, Chicheer,1991. [7] G. Nn, M. Muelli, and A. Luche, Tw eimain mehd fr mnhly mean hurly al irradiain n iled urface frm mnhly mean daily hriznal irradiain frm lar radiain daa f Ajacci, Crica. lar Energy, 57 (), Elevier cience Ld [8] G.N. Tiwari, lar Energy: Fundamenal, Deign, Mdelling and Applicain. Nara Publihing ue, New Delhi, ndia, 006. DO: / Page

5 Variain f Mean urly nlain wih Time a J Appendix A Average Daily nlain a J 1 Glbal radiain G in MJm day cnvered frm ml f Gunbellani Appendix B Average urly nlain a J Variain f maximum irradiance a lar nn in MJm wih ime f he day Appendix C: Variain f mean hurly inlain in MJm wih ime f he day DO: / Page