MODULE 5 Lecture No: 5 Extraterrestrial Radiation

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Rosalind Heath
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1 1 P age Principle and Perfrmance f Slar Energy Thermal Sytem: A Web Cure by V.V.Satyamurty MODULE 5 Lecture N: 5 Extraterretrial Radiatin In Mdule 5, Lecture N. 5 deal with 5.1 INTRODUCTION 5. EXTRA TERRESTRIAL SOLAR RADIATION ON DIFFERENT TIME SCALES 5.3 SUMMARY Lecture INTRODUCTION In Mdule 3, while intrducing the un-earth gemetry, tw reference lar radiatin quantitie have been identified. They are, the lar cntant G c, and the extraterretrial nrmal radiatin, G n. The difference between the tw being nly that, fr the lar cntant, the plane under cnideratin, nrmal t un' ray i at un-earth mean ditance, where a fr the extraterretrial nrmal radiatin, the plane i at the day' un-earth ditance. The meaurement in terretrial meterlgical tatin mtly pertain t hrizntal radiatin n variu time cale, hur, day, mnth r even a year, thugh, the bae meaurement i uually intantaneu value recrded and integrated ubequently t yield finite time interval quantitie. In thi Mdule, the crrepnding extraterretrial value are expreed, which erve a reference quantitie t the terretrial value. 5. EXTRATERRESTRIAL SOLAR RADIATION ON DIFFERENT TIME SCALES Intantaneu Extraterretrial Slar Radiatin n a rizntal Surface Crrepnding t, G n, the nrmal lar radiatin intenity under extraterretrial cnditin, the intenity n a hrizntal plane, G in W/m i given by, G = G n c z (5.1) Uing Eq.(3.1) fr G n and Eq.(3.11) fr c z, in Eq.(5.1), it fllw, 1 P age

2 P age G = G c ( c[360n/365] ) [ c c c + in in ] (5.) Extraterretrial Slar Radiatin n a rizntal Surface fr Shrt Time Interval Let 1, be the hur angle crrepnding t a time interval frm t 1 t t. I, the lar radiatin n a hrizntal urface fr the time interval can be expreed a, t I Gdt (5.3) t1 Uing Eq.(5.) in Eq.(5.3) and realizing that dt = d / [ /(1x3600)], lead t, I 1x Gc( c[360n/365])[ c c c in in ] d Upn integrating and ubtituting the limit, I in J/ ( m -hr) i given by, (5.4) 1x3600 I Gc ( c[360n / 365]) x [c c in( in 1) in in ( 1)] (5.5) In Eq. (5.5), 1 and are expreed in radian. Daily Extraterretrial Slar Radiatin n a rizntal Radiatin Extraterretrial lar radiatin received ver a day n a hrizntal urface,, can be btained uing Eq.(4.4), replacing the limit f integratin ( 1 t ) by ( - t ). i given by, 4x3600 G c ( c[360n / 365][c c in in in ] (5.6) P age

3 3 P age Mnthly Average Daily Extraterretrial Radiatin n a rizntal Surface The mnthly average daily extraterretrial lar radiatin n a hrizntal urface,, i defined by, i N 1/ N) i i1 ( (5.7) can be cnveniently evaluated with a ingle equatin, imilar t Eq.(5.6), withut ging thrugh ummatin fr 30 r 31 day a required by Eq.(5.7), by imply uing the mnthly mean declinatin, m, in place f in Eq.(5.6). The mnthly mean declinatin ha been defined a the value f the declinatin applicable fr the mnth, which yield a value f when ued in Eq.(5.6), yield clet t the value f, a wuld be btained when Eq.(5.7) i emplyed., i btained frm, Table 5.1 Recmmended mnthly mean day and the mean declinatin Mnthly Mean Day Mnth Date n, Day f the year m,the mean declinatin January February March April May June July Augut September Octber Nvember December P age

4 4 Page 4x3600 G c ( c[360n / 365][c c m in in in m ] In Eq.(5.8), i in radian. Value f m, the mnthly mean declinatin and the recmmended day f the mnth are given in Table 5.1 (5.8) Yearly Average Daily Extraterretrial Slar Radiatin n a rizntal Surface Vialakhi [] thrugh a ummatin prcedure develped an accurate exprein t calculate the yearly average daily extraterretrial lar radiatin n a hrizntal urface. The yearly average daily extraterretrial lar radiatin n a hrizntal urface y i defined a, y i365 i1 i j1 ( 1/ 365) (1/1) N (5.9) j1 j j y in MJ/m -day can be calculated accurately frm Vialakhi [] a, y = c + A in (5.10) Where, A = fr 0 and (5.11) A = fr 0 (5.1) In Eq.(5.10), it may be nted that i in degree and i pitive fr nrthern hemiphere and negative fr uthern hemiphere. 5.3 SUMMARY Exprein t calculate the extraterretrial lar radiatin received by hrizntal urface n different time cale have been develped. The tarting pint in develping thee exprein ha been the intantaneu extraterretrial lar radiatin n a urface nrmal t un' ray, which i in term f the lar cntant and an exprein 4 Page

5 5 Page in term f the day in the year, t take int accunt the varying ditance between the un and the earth frm day t day. The exprein are applicable fr a hrt time interval, uually an hur, a day and mnthly and yearly average day. The extraterretrial radiatin value depend n the finite time interval cnidered. The ther parameter are the latitude, declinatin and the hur angle under cnideratin fr the time perid cnidered. 5 Page

Empirical correlations for the estimation of global solar radiation using meteorological data in WA, Ghana

Empirical correlations for the estimation of global solar radiation using meteorological data in WA, Ghana Available nline at www.pelagiareearchlibrary.cm Advance in Applied Science Reearch, 2013, 4(4):63-71 ISSN: 0976-8610 CODEN (USA): AASRFC Empirical crrelatin fr the etimatin f glbal lar radiatin uing meterlgical