Analysis of the solar radiation data for Beer Sheva, Israel, and its environs

Solar Energ), Vol. 48, No. 2. pp. 97-106, 1992 Printed in the U.S.A.

0038-092X/92 $5.00 + .00 Copyright © 1992 Pergamon Press plc

ANALYSIS OF THE SOLAR RADIATION DATA FOR BEER SHEVA, ISRAEL, A N D ITS ENVIRONS A. I. KUDISH t and A. IANETZ ~ *Solar Energy Laboratory, Department of Chemical Engineering, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel, *Israel Meteorological Service, Research and Development Division, P.O.B. 25, Bet-Dagan 50205, Israel Abstract--The solar radiation climate of Beer Sheva, Israel, is reported upon in detail. The database utilized

in this analysis consisted of global radiation on a horizontal surface, normal incidence beam radiation, and global radiation on a south-facing surface tilted at 40 °. Monthly-average hourly and daily values are reported for each of these three types of measured radiations, together with the calculated monthly-average daily values for the components of the global radiation, viz. the horizontal beam and diffuse radiations. The monthly-average hourly and daily clearness index values have also been calculated and analyzed. Monthlyaverage daily frequency distributions of the clearness index values are reported for each month. The solar radiation climate of Beer Sheva has also been compared to those reported for a number of countries in this region. The annual-average daily global radiation incident on a horizontal surface is 18.91 MJ/m 2 and that for normal incidence beam radiation is 21.17 MJ/m 2. The annual-average daily fraction of the horizontal global radiation that is beam is 0.72. The annual-average daily value for the clearness index is 0.587 and the average frequency of clear days annually is 58.6%. We conclude, based upon the above analysis, that Beer Sheva and its environs are characterized by relatively high, average-daily irradiation rates, both global and beam, and a relatively high frequency of clear days.

1. I N T R O D U C T I O N

monthly-average hourly and daily values for the clearness index and the average-daily frequency distribution for each month.

A knowledge of the solar radiation climate of an area is of paramount importance in assessing the potential use of solar energy, converted to either thermal or electrical energy, as a power source in that area. Such information is a prerequisite for the design of such solar energy conversion systems. The meteorological station of the Solar Energy Laboratory at the Ben-Gurion University of the Negev, in Beer Sheva ( 3 1 ° 1 5 ' N , 34°45'E, 315 m MSL), has been concurrently measuring normal incidence beam radiation and global radiation on a horizontal surface and on a south-facing surface tilted at 40 °. Beer Sheva is located in the southern Negev region of Israel, a semiarid zone, and has relatively high average-daily irradiation rates, as evidenced by the measurements. Previously, the results of the analysis of the global radiation measured on a horizontal surface, during the time interval 1977-1980, were reported[I]. In that analysis the hourly values were based upon local time and the day was defined as 0600-1800 local time. In the present study, in addition to expanding the analysis to include the normal incidence beam and the global radiation incident on a south-facing surface tilted at 40 ° ( ~ ~ + 10°), all data are referred to solar time and the day is defined as 0500-1900 solar time. We will report on the monthly-average hourly and daily values for the horizontal global, normal incidence beam, and global radiation incident on a south-facing surface tilted at 40 ° . In addition, the monthly-average daily values for the horizontal beam and diffuse radiation have been calculated. We have also calculated the

2. M E A S U R E M E N T S

The normal incidence beam radiation is measured using an Eppley Normal Incidence Pyrheliometer, Model NIP, and the global radiation, both on the horizontal and tilted surfaces, is measured using Eppley Precision Spectral Pyranometers, Model PSP. This station is part of the national network of meteorological stations and the instruments' calibration constants are checked at regular intervals by the Israel Meteorological Service. Each of the above radiation measuring instruments was initially connected to an electronic integrator and printer but they are all presently connected to a rechargeable battery-powered datalogger (Campbell Scientific Instruments). The errors involved in the radiation measurements are assumed to be no less than _+1.5% for the normal incidence beam radiation and _+2.5% for the global radiation. The global radiation data analyzed in this study were collected during the time interval 1982-1990, whereas the normal-incidence beam radiation data refer to the time interval 1984-1990. Due to mechanical and electrical failures (prior to the addition of the rechargeable battery-powered datalogger), the actual a m o u n t of data available for analysis was reduced significantly. Consequently, the individual monthly analysis for global radiation on a horizontal surface, global radiation incident on a south-facing surface tilted at 40% and that for normal-incidence beam radiation are based upon 6-9, 6-8, and 3-6 years of data, respectively. In addition, the validity of the individual hourly values of the global and normal incidence beam

t ISES Member. 97

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A. I. KUDISH and A. IANETZ

radiation were checked in accordance with W M O reco m m e n d a t i o n s [ 2 ]. Those values that did not comply with the W M O r e c o m m e n d a t i o n s were considered erroneous a n d were rejected.

3. RESULTS The results of the analysis of o u r three sets of solar radiation data, horizontal global, normal-incidence beam, global on a south-facing surface tilted at 40 °, are s u m m a r i z e d in Tables 1-3, respectively. Monthlyaverage hourly a n d daily values are reported for each

m o n t h together with the n u m b e r of days per m o n t h (listed in parentheses) analyzed. The monthly-average daily global radiation on a horizontal surface a n d its components, viz. the b e a m a n d diffuse radiation, are presented graphically in Fig. 1. T h e measured hourly normal-incidence b e a m radiation values, lb,, were converted to b e a m radiation incident on a horizontal surface, l~, by applying the geometric conversion factor to individual hourly values, i.e., lb = lb,.cos 0~,

( 1)

Table 1. Monthly-average hourly global radiation (MJ/m 2) Month(days)

5-6

6-7

7-8

8-9 9-10 10-11

11-12 12-13 13-14 14-15 15-16 16-17 17-18 18-19 Daily

January(276) February(250) March(267) April(206) May(200) June(205) July(180) August(210) September(193) October(178) November(208) December(212)

0.00 0.00 0.02 0.04 0.12 0,17 0,15 0.07 0.02 0.01 0.00 0.00

0.01 0.04 0.18 0.40 0.60 0,71 0.62 0.49 0.30 0,18 0.07 0.03

0.23 0.40 0.73 1.04 1.30 1.43 1.30 1.18 0,93 0.69 0.41 0.27

0.69 0.96 1.36 1.69 2.02 2.18 2.06 1.94 1.67 1.34 0.97 0,71

1.53 1.86 2.31 2.78 3.06 3.22 3.18 3.06 2.77 2.27 1.81 1.51

1.68 2.01 2.46 2.99 3.26 3.43 3.40 3.28 2.98 2.47 1.93 1.65

1.62 1.95 2.44 2.91 3.18 3.41 3.38 3.23 2.95 2.42 1.87 1.54

1.40 1.69 2.20 2.63 2.95 3.16 3.13 2.93 2.66 2.10 1.56 1.32

1.04 1.37 1.79 2.19 2.49 2.73 2.67 2.47 2.16 1.63 1.13 0.93

0.59 0.89 1.22 1.65 1.91 2.13 2.09 1.86 1.52 0.99 0.63 0.47

0.18 0.37 0.60 0.98 1.22 1.43 1.40 1.13 0.80 0.41 0.20 0.13

0.01 0.03 0.13 0.35 0.54 0.71 0.67 0.43 0.20 0.07 0.02 0.00

0.00 0.00 0.00 0.08 0.08 0.14 0.13 0.03 0.02 0.00 0.00 0.00

10.16 13.05 17.35 22.07 25.31 27.64 26.89 24.88 21.30 16.46 12.07 9.74

Yearly

0.05 0.30 0.83 1.47 2.04

2.45

2.63

2.58

2.31

1.88

1.33

0.74

0.26

0.04

18.91

1.18 1.49 1.91 2.33 2.60 2.79 2.72 2.59 2.32 1.90 1.47 1.18

Table 2. Monthly-average hourly NIP radiation (MJ/m 2) Month(days)

5-6

6-7

7-8

8-9 9-10 10-11 11-12 12-13 13-14 14-15 15-16 16-17 17-18 18-19 Daily

January(163) February(159) March(169) April(134) May(133) June(125) July(86) August(88) September(86) October(107) November(158) December(100)

0.01 0.01 0.01 0.80 0.27 0.57 0.20 0.13 0.06 0.02 0.01 0.00

0.03 0.14 0.38 0.73 1.00 1.35 0.84 0.79 0.68 0.56 0.26 0.15

0.66 0.97 1.12 1.43 1.68 2.02 1.56 1.54 1.51 1.44 1.07 0.81

1.25 1.60 1.54 1.80 2.09 2.54 2.24 2.22 2.13 1.95 1.75 1.44

1.59 1.91 1.76 2.15 2.34 2.77 2.67 2.67 2.48 2.23 2.06 1.81

1.76 1.99 1.92 2.33 2.52 2.93 2.85 2.87 2.70 2.30 2.22 1.98

1.74 1.90 1.98 2.37 2.51 3.01 2.92 2.92 2.83 2.30 2.19 1.99

1.59 1.93 1.95 2.27 2.43 2.96 2.85 2.85 2.81 2.32 2.11 1.83

1.51 1.74 1.82 2.15 2.35 2.85 2.77 2.64 2.70 2.15 1.90 1.70

1.34 1.07 1.68 1.41 1.71 1.44 2.00 1.79 2.21 2.05 2.76 2.59 2.69 2.56 2.57 2.42 2.50 2.25 1.89 1.48 1.65 01.20 1.47 0.92

0.52 0.82 0.99 1.36 1.70 2.26 2.27 2.03 1.70 0.75 0.42 0.23

0.02 0.09 0.30 0.64 1.04 1.63 1.69 1.21 0.63 0.08 0.02 0.00

0.00 0.00 0.03 0.05 0.25 0.59 0.59 0.11 0.08 0.00 0.00 0.00

13.08 16.20 16.92 21.14 24.44 30.84 28.69 26.95 25.06 19.48 16.87 14.33

Yearly

0.11 0.58 1.32 1.88 2.20

2.36

2.39

2.32

2.19

2.04

1.25

0.61

0.14

21.17

1.76

Table 3. Monthly-average hourly global radiation on a south-facing surface tilted at 40 ° (MJ/rn 2) Month(days)

5-6

6-7

7-8

8-9 9-10 10-11

11-12 12-13 13-14 14-15 15-16 16-17 17-18 18-19 Daily

January (236) February (214) March (236) April (207) May (202) June (205) July (180) August (210) September(170) October (170) November(203) December(182)

0.00 0.00 0.01 0.04 0.14 0.12 0.08 0.07 0.02 0.01 0.00 0.00

0.01 0.05 0.19 0.32 0.37 0.41 0.39 0.40 0.29 0.24 0.14 0.12

0.44 0.59 0.83 0.97 1.00 1.03 1.00 1.09 1.01 0.95 0.72 0.51

1.16 1.36 1.57 1.67 1.71 1.76 1.75 1.90 1.88 1.81 1.56 1.27

2.30 2.48 2.69 2.91 2.87 2.89 2.96 3.16 3.21 2.97 2.74 2.38

2.48 2.64 2.87 3.15 3.10 3.11 3.19 3.39 3.46 3.21 2.87 2.56

2.35 2.55 2.83 3.05 3.02 3.08 3.14 3.30 3.38 3.09 2.73 2.38

2.03 2.18 2.52 2.70 2.77 2.77 2.83 2.92 3.00 2.66 2.32 2.06

1.55 1.79 2.04 2.18 2.23 2.28 2.31 2.36 2.39 2.05 1.72 1.50

0.94 1.15 1.36 1.52 1.61 1.62 1.64 1.63 1.62 1.27 0.99 0.80

0.30 0.48 0.63 0.82 0.90 0.90 0.90 0.85 0.80 0.51 0.31 0.18

0.00 0.03 0.10 0.23 0.28 0.29 0.28 0.23 0.16 0.04 0.00 0.00

0.00 0.00 0.00 0.00 0.06 0.05 0.05 0.01 0.00 0.00 0.00 0.00

15.41 17.32 19.85 21.97 22.38 22.73 23.00 23.95 23.87 21.32 18.34 15.69

Yearly

0.04 0.25 0.85 1.62 2.31

2.80

3.00

2.91

2.56

2.03

1.35

0.63

0.14

0.01

20.49

1.85 2.03 2.21 2.41 2.33 2.42 2.46 2.64 2.65 2.52 2.25 1.92

Analysis of solar radiation data for Beer Sheva, Israel

99

30000

GLOBAL •

BEAM

20000

tO000 ee

0

i

i

i

i

t

t

i

i

i

t

i

i

J

F

M

A

M

J

J

A

S

O

N

D

MONTH

Fig. 1. Monthly-average daily solar radiation for Beer Sheva, Israel.

where 0z is the average-hourly incidence angle, and average hourly values were then calculated from this converted database. These average hourly values were in turn summed to determine the average-daily beam radiation incident on a horizontal surface for each month. The monthly-average daily diffuse radiation values were then calculated from the difference between the corresponding values for the global and beam radiation incident on a horizontal surface. The monthly-average hourly and daily clearness index values are reported in Table 4. The daily values were calculated as the ratio of the measured global to extraterrestrial radiation during the time interval between sunset and sunrise and were then averaged to determine monthly-average daily clearness index values. Thus, they do not correspond to the average of the individual average hourly values, since the latter are not reported for the same time interval, viz. the hourly interval is truncated.

4. D I S C U S S I O N

4.1 Monthly-average daily solar radiation It is of interest to compare the monthly-average daily global radiation values reported in the present work with those reported previously [ 1]. The relative abundance of incident monthly average daily global radiation in both data basis is in the same exact order (i.e., June > July > May > . . . November > January > December). The values reported in the present work for the monthly-average daily global radiation are greater by a factor of ~ 1.02-1.06, with the exception of February and November which are smaller by a factor of 20.99. One would expect them to be greater, since the time interval analyzed in the present work was expanded relative to the previous one and is based upon solar time (cf. Introduction). The exceptions, viz. February and November, may be explained by the adjustment applied to the 1977 data as explained in

Table 4. Monthly-average hourly and daily clearness index values Month

5-6

6-7

7-8

8-9

9-10

10-11 11-12 12-13 13-14 14-15 15-16 16-17 17-18 18-19 Daily

January 0.377 0.448 0.514 0.539 0.538 0.520 February 0.393 0.488 0.542 0.562 0.560 0.541 March 0.409 0.470 0.543 0.581 0.598 0.595 0.590 April 0.418 0.521 0.577 0.632 0.659 0.665 0.648 May 0.398 0.460 0.570 0.637 0.670 0.697 0.699 0.684 June 0.345 0.489 0.596 0.671 0.710 0.728 0.734 0.730 July 0.308 0.439 0.552 0.643 0.698 0.725 0.732 0.726 August 0.452 0.571 0.655 0.701 0.725 0.729 0.717 September 0.446 0.546 0.631 0.679 0.700 0.703 0.696 October 0.460 0.575 0.627 0.654 0.657 0.662 0.648 November 0.447 0.582 0.609 0.617 0.601 0.580 December 0.401 0.508 0.550 0.568 0.563 0.527

0.493 0.511 0.571 0.624 0.671 0.714 0.711 0.688 0.671 0.610 0.530 0.497

0.453 0.496 0.542 0.596 0.640 0.694 0.686 0.661 0.632 0.560 0.472 0.435

0.386 0.449 0.485 0.561 0.604 0.656 0.653 0.614 0.575 0.463 0.381 0.342

0.316 0.366 0.393 0.492 0.537 0.597 0.594 0.529 0.469 0.339 0.348 0.342

0.495 0.516 0.295 0.554 0.367 0.597 0.414 0.283 0.630 0.484 0.294 0.670 0.480 0.296 0.662 0.370 0.654 0.295 0.642 0.350 0.596 0.528 0.498

100

A.I. KUDISH and A. IANETZ 0.7

0.6

0.5

t~

0.4

t

t

I

t

t

t

I

t

t

t

t

I

J

F

M

A

M

J

J

A

S

O

N

D

MONTH Fig. 2. Monthly-average daily clearness index for Beer Sheva, Israel. 40

•

Dec

[]

Jan

•

Feb

30

m

F20

,.ill

1o

o ,tli[ i [i .t 0.05

0.15

0.25

0.35

0.45

0.55

0.65

0.75

CLEARNESSINDEX (a) Fig. 3. Monthly percent frequency distribution of daily clearness index: (a) December-February, (b) MarchMay, (e) June-August, (d) September-November.

Analysisof solar radiation data for Beer Sheva, Israel

l 01

60 1

Mar

A~r 50

Z

~e

Z 20 CY ~e

0 0.05

0.15

0.25

0.35

CLEARNESS

0.45

0.55

0.65

0.75

INDEX

(b) Fig. 3. (Contd.)

[ 1] and the relatively small database available for these months in the previous analysis. In both cases the adjusted 1977 average monthly values were the maximum values reported for each month. Also, in February the average deviation between solar and local time is the minimum (on a monthly basis), ~ 5 min, and there is no measured radiation prior to 0600 or after 1800. The analysis of the solar radiation data can be briefly summarized by the following: 1. The annual-average daily value for global radiation on a horizontal surface is 18.91 M J / m 2. The maximum, 27.64 M J / m 2, occurs in June and the minimum in December, 9.74 M J / m 2. 2. The annual-average daily value for normal incidence beam radiation is 21.17 M J / m 2. The maximum, 30.84 M J / m 2, occurs in June and the minimum is in January, 13.08 M J / m 2. 3. The annual-average daily value for the global radiation incident on a south-facing surface tilted at 40 ° is 20.49 M J / m 2. In this case, both the maximum and minimum values are essentially spread over a two month period. Maximum values were

measured for August and September, 23.95 and 23.87 M J / m 2, respectively. Minimum values were measured for January and December, 15.41 and 15.69 MJ / m E, respectively. The data for the monthly-average daily global radiation incident on a south-facing surface tilted at 40 ° is an important parameter for this region. Tilting a south-facing surface at this angle, which is equivalent to the latitude + 10°, is the recommended tilt angle for maximizing the year-round performance of flatplate solar collectors. In fact, the reason for initiating the measurement of the global radiation on such a surface was to monitor the performance of a central DHW system, which consisted of twenty flat-plate solar collectors positioned at such an angle[3 ]. 4.2 Hourly distribution of global and normal

incidence beam radiation We have also analyzed both the global on a horizontal surface and normal-incidence beam radiations to determine the hourly distribution of the daily radiation. We divided the day into two parts: the peak

102

A.I. KUDISHand A. IANETZ 80 •

June

[]

July

60 1 •

Aug

o

[.. 40

Z

r=

20

O

~ 0.05

0.15

0.25

0.35

0.45

0.55

0.65

0.75

CLEARNESS INDEX

(c) Fig. 3. (Contd.)

insolation hours from 1000 to 1400 and the rest of the day, viz. sunrise to 1000 and 1400 to sunset. December is the month with the maximum and June the month with minimum fraction of daily radiation during the peak insolation hours, 1000 to 1400, for both global and normal incidence beam. In the case of global radiation, 62.0 and 47.8% of the radiation is incident during the peak insolation hours in December and June, respectively (a factor of ~ 1.3 ). On a yearly average basis, 52.7% of the global radiation is incident between 1000 to 1400. In the case of normal-incidence beam radiation, 52.3 and 38. 1% of the radiation is incident during the peak insolation hours in December and June, respectively (a factor of ~ 1.4). On a yearly average basis, 43.8% of the normal-incidence beam radiation is incident between 1000 to 1400.

are much smaller than those for horizontal global and beam radiation. These fluctuations can be summarized by the following: the horizontal global radiation varies between 27.64 (June) and 9.74 M J / m 2 (December), a factor of ~ 2.8; the horizontal beam radiation varies between 22.52 (June) and 5.99 M J / m 2 (January), a factor of 3.8; the diffuse radiation varies between 3.45 (December) and 7.46 M J / m 2 (May), a factor of .-~2.2. The annual-average daily values are 18.91, 13.61, and 5.30 M J / m 2 for the global, beam, and diffuse, respectively. The fraction of the monthly-average daily horizontal global radiation that is beam varies between 0.59 in January to 0.82 in June, with the annual-average daily fraction being 0.72. 4.4 Clearness index-average values and frequency

distribution 4.3 Monthly-average daily components of global

radiation It is observed from Fig. 1 that the fluctuations in the monthly-average daily values for diffuse radiation

The monthly-average hourly and daily values for the clearness index are reported in Table 4. The values of the monthly-average daily clearness index vary between a maximum of 0.670 for June and a minimum

Analysis of solar radiation data for Beer Sheva, Israel

103

80 J •

Sept

[] Oct

6o r •

Nov

Z [... 40

Z

r~.

20

O 0.05

0.15

~ 0.25

0.35

0.45

0.55

0.65

0.75

CLEARNESS INDEX

(~) Fig. 3. (Contd.)

of 0.495 for January. The annual-average daily clearness index is 0.587. The fluctuations in the monthlyaverage daily clearness index values are shown in Fig. 2. It is apparent from this analysis that this region is characterized by relatively clear skies during a major portion of the year. The monthly-average frequency distributions of the clearness index are reported in Fig. 3. The months have been divided into four groups for the sake of clarity, corresponding to the four seasons experienced in this region, viz. winter--December-February; spring-March-May; summer--June-August; autumn--September-November. The annual-average frequency distribution of the clearness index is reported in Fig. 4. Throughout the year a relatively high frequency of clear days (defined here as Kr > 0.60, since the bin width was taken as 0. l0 units) is observed for this region. The lowest frequency of clear days occurs during December, 27.6%, whereas the highest frequency of clear days occurs during July, 94.6%. The average frequency of clear days annually is 58.6%.

4.5 Comparison of Beer Sheva's solar radiation climate to those reported for other sites in the region It is of interest to compare the results of our analysis of the solar radiation climate for Beer Sheva to those reported in the literature for this region. Stanhill[4] has previously reported the monthly-average daily global radiation as measured by a number of Israeli meteorological stations, including Beer Sheva (using the data from [ 1]). We will, therefore, restrict ourselves to a comparison of the Beer Sheva solar radiation climate with those reported for a number of our neighboring countries. AI-Riahi et aL[5 ] have recently reported upon the solar radiation climate for Fudhaliyah-Baghdad, Iraq. Since their data analysis was reported in a manner similar to the present work, it is amenable to an in depth comparison: a priori, one would expect the solar climate of these two sites to be similar. A number of parameters characterizing the two solar radiation climates are compared in Table 5 and they are, indeed, very similar.

104

A.I. KUDISHand A. IANETZ

[]

Yearly

40

30 Z

o

~s

7,0

Z

10

,

0.05

I i ,

,

0.15

0.25

I

,

,

0.35

0.45

0.55

0.65

0.75

CLEARNESS INDEX

Fig. 4. Annual percent frequency distribution of daily clearness index.

We can expand this comparison to include other countries in this region, but it will be limited to a comparison of the annual- and monthly-average daily horizontal global radiation. In Table 6 we have horizontal global radiation data reported for Beer Sheva, Israel (present work), Fudhaliyah-Baghdad, Iraq [ 5 ], Safat, Kuwait[6], Cairo, Egypt[7], Dhahran, Saudi Arabia[ 8 ], Beirut, Lebanon [9 ], Wadi Dhuliel, Jordan [9 ] and Raqqa, Syria[9]. It is obvious from these data that this region is blessed with an abundance of solar radiation. The monthly-average daily horizontal global radiation recorded for the sites listed in Table 6 exhibit a maximum value in June for Cairo, 29.74 M J / m 2, and a minimum value in December for Raqqa, 7.83 M J / m 2. The annual-average daily horizontal global radiation for this region varies from 17.26 M J / m 2 for Beirut to 24.30 M J / m 2 for Cairo.

5. C O N C L U S I O N S

The solar climate of Beer Sheva, Israel, and its environs has been reported upon in detail. 1. The measured solar radiation data have been ana-

lyzed and monthly-average hourly and daily values have been reported for global radiation on a horizontal surface, normal incidence beam radiation, and global radiation incident on a south-facing surface tilted at 40 ° . 2. The hourly distribution of the daily global radiation on a horizontal surface and normal incidence beam radiation have been reported. 3. The monthly-average daily components of the global radiation on a horizontal surface, viz. the beam and diffuse, have also been calculated and analyzed. 4. The monthly-average hourly and daily clearness index values have been calculated and analyzed. 5. The monthly-average daily frequency distributions of the clearness index values have also been determined. 6. The solar radiation climate for Beer Sheva has also been compared to those for a number of countries in this region. We conclude, based upon the above analysis, that Beer Sheva and its environs are characterized by relatively high average-daily irradiation rates, both global and beam, and a relatively high frequency of clear days.

Analysis of solar radiation data for Beer Sheva, Israel

105

Table 5. A comparison of the solar radiation climates of Beer Sheva, Israel and FudhaliyahBaghdad, Iraq

Latitude Longitude Elevation Annual-average daily solar radiation (MJ/m 2) Global Beam Diffuse Range of monthly-average daily solar radiation (MJ/m 2) Global Diffuse Annual- and range of monthly-average daily ratio of beam to global Annual average Maximum Minimum Range of monthly-average daily clearness index Maximum Minimum Hourly global radiation at midday (MJ/m2h) Maximum Minimum

Beer Sheva

Fudhaliyah-Baghdad

31 ° 1YN 34 o45'E 315 m MSL

33 ° 14'N 44 ° 14'E 34 m MSL

18.91 13.61 5.20

18.28 12.42 5.86

27.64-9.74 7.46-3.45

25.71-9.57 8.50-3.29

0.72 0.82 (June) 0.59 (Jan.)

0.68 0.744 (Sept.) 0.636 (Nov.)

0.670 (June) 0.495 (Jan.)

0.663 (Sept.) 0.529 (Dec.)

3.43 (June) 1.54 (Dec.)

3.16 (June) 1.59 (Dec.)

Table 6. A comparison of the annual- and monthly-average daily global radiation (MJ/m 2) for a number of countries in this region Beer Sheva

FudhaliyahBaghdad [5]t

Safat [6]

Cairo [7]

Dhahran [8]

Beirut [9]

Wadi Dhuliel [9]

Raqqa [9]

Latitude Longitude Elevation

31°15~ 34°45'E 315 m MSL

33° 1 4 ' N 44 ° 1 4 ' E 34 m MSL

29°20'N 47°57'E --

30°03'N 31 ° 1 5 ' E --

26° 13q'q 50°00'E --

33°49'N 35°29'E 18 m MSL

32°09q~ 35 ° 1 7 ' E 580 m MSL

35o57'N 39°00'E 250 m MSL

January February March April May June July August September October November December

10.16 13.05 17.35 22.07 25.31 27.64 26.89 24.88 21.30 16.46 12.07 9.74

11.0 15.2 17.3 21.2 24.0 25.7 25.3 23.2 22.0 15.4 11.4 9.6

12.84 16.75 18.78 22.42 24.93 27.22 26.56 25.74 23.18 17.55 13.90 11.71

20.77 21.13 22.43 27.40 27.18 29.74 28.12 28.44 24.48 22.68 18.72 20.52

14.40 16.56 19.08 23.40 25.20 28.08 27.36 26.28 23.04 19.44 15.48 13.68

8.31 11.49 15.77 19.79 23.26 25.95 25.26 23.13 19.37 15.29 10.81 8.34

11.96 14.94 20.36 23.97 28.80 28.53 29.62 27.21 23.53 17.88 13.40 13.76

8.99 12.08 17.45 21.08 27.40 28.33 27.46 22.39 20.40 15.37 10.92 7.83

Annual

18.91

18.28

20.13

24.30

21.00

17.26

20.86

18.55

Average-daily global radiation (MJ/m 2)

* The data for Fudhaliyah-Baghdad have been interpolated from Fig. 1 in [5].

106

A.I. KUDISH and A. IANETZ

Acknowledgments--We are indebted to Mr. E. Berman for his partial support of this research by funding the purchase of the Normal Incidence Pyrheliometer system. We also wish to thank Drs. A. Manes and I. Seter of the Israel Meteorological Service for their encouragement of this joint research project.

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4. G. Stanhill, The radiation climate of the Dead Sea, J. Climatology 7, 247 ( 1987 ). 5. M. AI-Riahi, N. A1-Hamdani, and K. Tahir, Contribution to the study of the solar radiation climate of the Baghdad environment, Solar Energy 44, 7 (1990). 6. S.D. Al-Aruri, The empirical relationship between global radiation and global ultraviolet (0.290-0.385) #m solar radiation components, Solar Energy 45, 61 (1990). 7. E. EI-Rafey and M. EI-Sherbiny, Load/weather/insolation database for estimating photovoltaic array and system performance in Egypt, Solar Energy 41,531 ( 1988 ). 8. V. Bahel, R. Srinivasan, and H. Bakhsh, Solar radiation for Dhahran, Saudi Arabia, Energy 11, 985 (1986). 9. Commission of European Communities. Solar radiation atlas, voL 1: Global radiation on horizontal surfaces, W. Palz (ed.), Verlag Piiz Rheinland GmbH, K61n (1984).