effect of altitude and tilt angle on solar radiation in tropical regions

96 Journal of Science & Technology

Vol. (19) No. (1) 2014

Effect of Altitude and Tilt Angle on Solar Radiation in Tropical Regions

Effect of Altitude and Tilt Angle on Solar Radiation in

Tropical Regions

Abdul-Aziz Mohamed Saeed Aldobhani(1)

ABSTRACT

Solar radiation is the main factor that affects the PV system design. Because of high shortage in solar radiation data in many regions, the mathematical models are necessary to use in solar radiation data estimation. In this study Hotel method is modeled and applied to extend the knowledge about the solar radiation on horizontal surface, fixed tilt surface and optimal tilt angle surface in tropical climate regions. In addition, the study inspects in the effect of altitude on solar radiation, and analyzes the variation in solar radiation data in areas that have high diversity in altitude regions. The data provides the PV system designer the exact percentages increase in solar radiation in important times in the year caused by rising in altitude and shifting the tilt angle from horizontal to optimum fixed annually tilt angle and optimum daily tilt angle. The study concludes to the main recommendations that can help the PV system designers to improve the output of PV system. In addition, the study analyzes the combination effect of solar radiation in different altitudes and tilt angles to recommend the designers the procedures of improving the peak sun hours of design month for PV systems. Keywords: PV system, Solar radiation, Altitude, Tilt angle, Zenith angle.

1. INTRODUCTION

Solar radiation is the main factor that affects on PV system design. The amount of solar energy collected by a solar panel is a function of local solar radiation. There is a significant potential for utilizing the photovoltaic solar energy in Yemen which receives more than 5.5 KW/m2/day on a horizontal surface for the most regions around the year [1]. There is a shortage in solar radiation data in most regions in Yemen. The amount of solar radiation incident on tilted surface at any time is a complex function that depends on several parameters like the global radiation on a horizontal surface, the ground reflectance, and the day of the year [2]. The tilt angle of PV system, region altitude and climate

1- Deportment of Electronic engineering, Faculty of engineering, University of Science and

Technology, Sana'a, Yemen


Vol. (19) No. (1) 2014


influences are the main factors that affect on amount of daily and average monthly solar radiation that is received by the square meter of PV array. The total yearly solar energy that is received by tilted PV panels could be better than the incident energy on horizontal one. This amount will be increased for optimum fixed tilt angle of PV solar system in different latitude. Thus, the amount of solar radiation is increasing and the output of PV array is increasing. The knowledge about the solar radiation on horizontal surface or fixed tilt surface is not sufficient to optimize the design of PV system. In addition, the solar radiation data in most regions is not covered the effect of altitude in solar radiation. The effect of altitude on solar radiation as a result the PV system design could be observed in areas that have high diversity in altitude. Many regions in Yemen, as a case study have large variations in elevation in few square kilometers. Hence the effect altitude on solar radiation has to be studied carefully to find out the required factors in PV system design. Many papers are published in different countries to study the effect of either the altitude or tilt angle of PV panels on the solar radiation as a result on the output energy of PV system. For example: Guglielmos. Aglietti and others in [3] examined the possibility to harvest solar energy in the high atmosphere, as an intermediate solution between round-based PV devices and satellite solar power in UK.Stefano Redland and others in [4] harnesses the solar power at high altitude and transmits it to the ground via the mooring cable. The model of a tethered lighter than air spherical balloon is used to simulate the behavior of the system in working conditions. TamerKhatib, A. Mohamed, K. Sopian in [5] use Liu and Jordan model to optimize the monthly tilt angle for solar panels for five main sites in Malaysia. Anu George, Robins Anto in [6] estimated theoretically the values of optimal tilt angle over each month for a PV panel installed in Kerala, India (9.55°N, 76.81ºE) using geographic factor method, clearness index method and declination angle method. DrissLahjouji, HassaneDarhmaoui in [7] developed A mathematical model to calculate solar radiation on an inclined surface as a function of the tilt angle. The study shows that the monthly optimal tilt angle allows maximum solar radiation collection. This study will investigate in the effect of altitude on solar radiation in tropical region. Also the study will figure out and analyze the effect of tilt angle on solar radiation in different altitude levels. The main purpose of this study is to find out the required progressions that will improve the Peak sun hours for design month the PV array in different altitude regions. This paper is organized as follows: introduction and a literature reviews in this field have been introduced in this section. Section two explains the effect of the main influences on solar radiation in, Section three analyzes and investigates the effect of altitude and tilt angle on solar radiation as well on PV panels output. The last section gives the final conclusion and recommendations that can improve the peak sun hours of different types of PV system.


Vol. (19) No. (1) 2014


2. Factors that effect on solar radiation

The main factor that can affect the PV system design is the amount of solar

radiation in different months within the year. The minimum solar radiation is

the mainly value that is used to design the standalone PV systems for different

loads. In addition, the maximum cloudy days per year is another important

factor in the design of standalone PV system for critical loads. A big diversity

in amount of solar radiation in different months dissipates a big available power

from PV array if the system is designed concerning the minimum monthly

radiation system design. As well the long cloudy days have the main effect on

the total storage capacity, as a result the cost of standalone PV system. The

solar radiation per square meter can be increased by the following two

methods:

By change the tilt angle of PV panels in different times per year

By increase the altitude of system location.

These two influences will be investigated in section 3.As well as to recognize

these two influences the air mass and main parameters that verify the optimal

tilt angle will be discussed.

2.1 Effect of Air mass on solar radiation The atmosphere scatters and absorbs some of the Sun’s energy that

is incident on the Earth’s surface. The amount of energy reflected,

scattered and absorbed depends on the amount of atmosphere that

the incident radiation travels through as well as the levels of dust

particles and water vapor present in the atmosphere.

The distance travelled through the atmosphere by the Sun’s rays incident on the Earth is accounted for by a quantity called air mass (AM) which can be calculated from Equation (1) or equation (2) [8][2].

(1)


Vol. (19) No. (1) 2014


Where: θ is the Zenith angle.

Air mass affects the amount of spectral content of solar radiation reaches to

earth's surface, and varies with sun position and altitude. Accordingly outside

the Earth's atmosphere AM = 0, when the sun is directly overhead and the

average extraterrestrial insolation at the edge of the atmosphere (solar constant)

is 1367 w/m2 [8][9].

Higher altitudes complicate things somewhat because the higher you go above

sea level, the fewer atmospheres there is and the more the composition of that

atmosphere differs from the atmosphere at sea level. The effect of air mass is

most felt when the sun is lower in the sky and so it has a bigger impact on the

insolation of high latitude places.

2.2 Effect of array tilt on solar radiation [9] The power of solar radiation that incident on a PV module depends not only on

the power contained in the sunlight, but also on the angle between the module

and the sun. The tilt angle has a major impact on the solar radiation incident on

a surface. When the absorbing surface and the sunlight are perpendicular to

each other, the power density will always be at its maximum when the surface

is perpendicular to the sun. Typically the amount of solar radiation incident on

a tilted module surface is the component of the incident solar radiation which is

perpendicular to the module surface. However, as the angle between the sun

and a fixed surface is continually changing, the power density on a fixed PV

module is less than the available incident sunlight [10].

For a fixed tilt angle, the maximum power over the course of a year is obtained

when the tilt angle is equal to the latitude of the location [2]. However, steeper

tilt angles are optimized for large winter loads, while lower tilt angles use a

greater fraction of light in the summer. The simulation below calculates the

maximum number of solar insolation as a function of latitude and module

angle. The optimal tilt angle is the angle that can eliminate the effect of

declination angle (δ) during different time per year on different latitude

locations. The declination of the sun is the angle between the equator and a line

drawn from the center of the Earth to the center of the sun. The declination is a

function of number of day per year[2].

(2)


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The declination angle varies seasonally due to the tilt of the Earth on its axis of rotation and the rotation of the Earth around the sun. If the Earth were not tilted on its axis of rotation, the declination would always be 0°. However, the Earth is tilted by 23.45° and the declination angle varies between 23.25º in summer solstice and -23.25º in winter solstice. Only at the spring and fall equinoxes is the declination angle equal to 0° [10].The optimal tilt angle for a given moment is the one that keeps the sunlight perpendicular to the tilted surface at that moment and is equal to 90°[2][10].

3. Improving the solar radiation.

To improve the output power of PV panels the factors that affect solar radiation

should be studied carefully before PV system is installed. The incidence solar

radiation per square meter can be improved by change the elevation of installed

PV system in regions that have a variety of altitudes.

As mentioned previously the altitude is one of the main factors that are effect

on air mass as a result the total solar radiation per meter square. In addition, the

tilt angle of PV array has a complicated effect on total solar radiation in

different times per year and in different altitude locations.

To track a significant solar radiation, the effect of altitude and tilt angle has to be studied indifferent times per year. Hotel method in tropical climate regions is modeled in this paper to study the effect of these two influences on different times per year and different altitude levels and different tilt angles of meter square of surfaces.

3.1 Estimation of clear sky radiation Hotel has presented a method for estimating the beam radiation transmitted through clear atmosphere in four climate types [2]. The method takes into account zenith angle on horizontal surface (θZ)and altitude (A).The atmosphere transmission of the beam radiation could be calculated by:

)cos/exp(10 Zb kaa

Where constants 0a , 1a and k are for the slandered atmosphere with 23km

visibility and are founded from 0a *, 1a * and k*, which are given for altitude

less than 2.5 km by: 2*

0 )6(00821.04237.0 Aa

2*1 )5.6(00595.05055.0 Aa

2* )5.2(01858.02711.0 Ak

(3)

(4)

(5)

(6)


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Where: A is the altitude of the observer in kilometers.

Hence, 0a , 1a and k are calculated as following:

0*00 raa

1*11 raa

krkk *

The changes in the Hotel correction factor r0, r1 and rk depend on climate types and given in Table (1). Also, the variation in zenith angle on horizontal surface (θZ) in equation (3)is a function of latitude (φ) , declination (δ) and hour angle (ω) and is given by :

sinsincoscoscoscos Z

The declination is a function of the day in year n (n=1 on 1 January and can be calculated by using equation (11)

)365

284360sin(45.23

n

Hence the total beam radiation (Ib) on horizontal surface can be calculated by using Equation (12)

bb GI 0

Where GO is the solar radiation incident on horizontal plane outside the atmosphere and given by:

ZSCO

nGG cos)]

365

360cos(033.01[

Where the maximum solar radiation outside atmosphere 1367SCG Wh/m2,

n is the day in the year (n=1 on January,1) The relationship between the transmission coefficient for beam radiation (τb) and diffuse radiation (τd) for a clear day is given by equation (14):

b

O

dd

G

I 294.0271.0

Where: Id is the incident diffuse radiation on horizontal plane. The total solar radiation on the tilted surface in south north direction and oriented in vertical axis (IT) can be calculated by:

)2

cos1()

2

cos1(

gdbbT IIRII

(7)

(8)

(9)

(10)

(11)

(12)

(13)

(14)

(15)


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Where β is the tilt angle of surface, g is the reflectance of the ground, I is the

total incident solar radiation on horizontal surface and Rb is ratio between beam radiation on the tilted surface to that on horizontal and can be calculated by:

The zenith angle (θ) is given by:

cossinsincos cossincossin

coscoscoscos coscossinsincos

sinsinsincos (17)

Where: is the surface azimuth angle. Table (1) shows the correction factors

to be used with four climate types.

Table (1 ):Correction Factors for Climate Types

Climate Type r0 r1 rk

Tropical 0.95 0.98 1.02 Middle attitude summer 0.97 0.99 1.02 Subarctic summer 0.99 0.99 1.01 Middle attitude winter 1.03 1.01 1.00

3.2 data description

The mathematical model in this study is applied using the tropical correction

factors. The data shown in Table(2),Table(3)and Table(4) are obtained every 15

minutes for 6 selected days per years and with 100 m change in altitude

between see level(0 meter) and 2500 meter. The data is obtained at latitude

15.5º N as a case study of tropical region. The data in Table (2),Table (3) and

Table (4) are illustrated in Figure (1) , Figure (2) and Figure (3) receptively.

Figure (1) shows the variation in solar radiation in meter square per day for 0o

tilt angle surface. Figure (2) shows the variation in solar radiation per meter

square per day for 15.5º south tilt angle surface which is the optimal fixed angle

per year of this latitude. Figure (3) shows the variation in solar radiation per

meter square per day for optimum daily tilt angle surface which is obtained by

subtracting the latitude angle from declination angle [10][11] .

(16)


Vol. (19) No. (1) 2014


The six days data in the three figures that are selected according to three

criterions as follow:

21 June and 21 December: represent the summer solstice and winter

solstice. In these two dates the beam radiation has maximum deviation

in zenith for optimum fixed tilt angle surface per year.

21 March and 21 September: where the sun is directly overhead at solar

noon at all points on the equator. In these two dates the beam radiation

has approximately zero deviation in zenith angle for optimum fixed tilt

angle surface per year at mid-daytime.

3 May and 10 August: In these two dates the beam radiation has

approximately zero deviation in zenith angle for 0o tilt angle surface per

year at mid-daytime in 15.5º latitude regions.

3.3Data investigation

As mentioned in section 2 the altitude and tilt angle are the two influences that

can improve the incident solar radiation per meter square as demonstrated in

Figure (1) , Figure (2) and Figure (3).

The tilt angle of PV system changes the value of zenith angle of beam

radiation. As the zenith angle approaches to zero at midday (Beam radiation is

perpendicular to PV panels) the total solar radiation per day on the surface has

its maximum intensity [11]. This can be made by change the tilt angle of PV

array by angle equal the result of subtraction of the latitude angle from

declination angle as mentioned previously.

When the surface is tilted toward the equator with constant angle which is

equal the latitude of system location, the incident solar radiation will improve

at vernal equinox in March autumnal equinox in September. This can be

observed from Figure (2) relating to the data in the horizontal surface in Figure

(1). Furthermore, the best annually average solar radiation can be obtained

when the surface is tilted with this fixed angle (neglecting the climate effect).

To improve the Peak sun hours for design monthly the PV array has to be

oriented to tilt angle at value near optimum angle in winter and summer

solstice.


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Table(2):Total solar radiation in different altitude and 0º tilt angle surface

β = 0o

Solar radiation (Wh/m2)

21-Dec 21-Sep 10-Aug 21-June 3-May 21-Mar Day

Altitude

4837.315 6544.005 7003.779 7026.046 7065.979 6620.299 0

4898.595 6616.28 7079.34 7102.371 7142.21 6693.413 100

4957.958 6686.182 7152.404 7176.179 7215.924 6764.127 200

5015.389 6753.706 7222.968 7247.465 7287.114 6832.434 300

5070.876 6818.847 7291.028 7316.227 7355.779 6898.331 400

5124.408 6881.603 7356.585 7382.462 7421.918 6961.816 500

5175.976 6941.975 7419.639 7446.172 7485.532 7022.889 600

5225.572 6999.963 7480.194 7507.359 7546.625 7081.55 700

5273.192 7055.572 7538.256 7566.029 7605.203 7137.805 800

5318.832 7108.807 7593.832 7622.187 7661.272 7191.658 900

5362.491 7159.677 7646.93 7675.844 7714.842 7243.118 1000

5404.172 7208.189 7697.562 7727.01 7765.924 7292.193 1100

5443.875 7254.357 7745.742 7775.698 7814.532 7338.897 1200

5481.608 7298.193 7791.484 7821.922 7860.68 7383.241 1300

5517.378 7339.712 7834.806 7865.701 7904.386 7425.242 1400

5551.193 7378.933 7875.725 7907.051 7945.669 7464.918 1500

5583.065 7415.873 7914.263 7945.994 7984.55 7502.287 1600

5613.009 7450.554 7950.443 7982.553 8021.051 7537.37 1700

5641.038 7482.998 7984.288 8016.751 8055.196 7570.191 1800

5667.172 7513.23 8015.824 8048.615 8087.013 7600.774 1900

5691.429 7541.275 8045.079 8078.172 8116.528 7629.145 2000

5713.83 7567.162 8072.082 8105.452 8143.77 7655.331 2100

5734.399 7590.918 8096.863 8130.485 8168.772 7679.363 2200

5753.16 7612.574 8119.455 8153.303 8191.563 7701.27 2300

5770.14 7632.162 8139.889 8173.941 8212.179 7721.086 2400

5785.366 7649.715 8158.201 8192.431 8230.654 7738.842 2500

Figure (1): Variation of solar radiation in different altitude and 0º tilt angle surface

0 500 1000 1500 2000 25004500

5000

5500

6000

6500

7000

7500

8000

8500

Altitude

Ener

gy W

h/m

2

= 0o

21-Mar

3-May

21-June

10-Aug

21-Sep

21-Dec


Vol. (19) No. (1) 2014


Table (3):Total solar radiation in different altitude and 15.5º tilt angle surface

β = 15.5o

Solar radiation (Wh/m2)


Altitude

5701.298 6732.175 6619.76 6346.67 6678.131 6810.109 0

5786.186 6808.937 6687.057 6408.305 6746.017 6887.749 100

5868.487 6883.179 6752.087 6467.847 6811.616 6962.841 200

5948.18 6954.895 6814.85 6525.297 6874.928 7035.377 300

6025.242 7024.081 6875.346 6580.655 6935.953 7105.355 400

6099.657 7090.734 6933.578 6633.924 6994.694 7172.771 500

6171.408 7154.855 6989.548 6685.111 7051.153 7237.625 600

6240.481 7216.445 7043.263 6734.22 7105.338 7299.92 700

6306.867 7275.508 7094.73 6781.261 7157.255 7359.658 800

6370.558 7332.05 7143.959 6826.242 7206.914 7416.847 900

6431.549 7386.079 7190.96 6869.175 7254.327 7471.494 1000

6489.837 7437.605 7235.747 6910.073 7299.505 7523.609 1100

6545.424 7486.641 7278.333 6948.951 7342.463 7573.206 1200

6598.313 7533.2 7318.735 6985.823 7383.218 7620.298 1300

6648.512 7577.3 7356.97 7020.707 7421.787 7664.901 1400

6696.029 7618.957 7393.056 7053.621 7458.189 7707.035 1500

6740.878 7658.193 7427.016 7084.585 7492.446 7746.719 1600

6783.074 7695.029 7458.87 7113.621 7524.578 7783.977 1700

6822.637 7729.49 7488.643 7140.751 7554.611 7818.831 1800

6859.588 7761.601 7516.358 7165.996 7582.568 7851.309 1900

6893.951 7791.39 7542.042 7189.384 7608.477 7881.438 2000

6925.753 7818.886 7565.722 7210.937 7632.363 7909.248 2100

6955.026 7844.119 7587.425 7230.683 7654.257 7934.77 2200

6981.801 7867.122 7607.182 7248.649 7674.186 7958.036 2300

7006.114 7887.928 7625.023 7264.862 7692.182 7979.08 2400

7028.002 7906.573 7640.977 7279.351 7708.276 7997.937 2500

Figure (2): Solar radiation in different altitude and 15.5º tilt angle surface

0 500 1000 1500 2000 25005500

6000

6500

7000

7500

8000

Altitude

Ene

rgy

Wh/

m2

= 15.5o

21-Mar

3-May

21-June

10-Aug

21-Sep

21-Dec


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Table (4): solar radiation in different altitude and optimum daily tilt angle surface

β = Optimumo Solar radiation (Wh/m2)


Altitude

6275.105 6731.954 7003.192 7195.721 7065.5 6809.921 0

6381.788 6808.722 7078.733 7277.121 7141.715 6887.567 100

6485.296 6882.971 7151.778 7355.869 7215.413 6962.664 200

6585.598 6954.693 7222.323 7431.959 7286.588 7035.206 300

6682.665 7023.885 7290.365 7505.384 7355.238 7105.188 400

6776.47 7090.544 7355.904 7576.142 7421.362 7172.609 500

6866.989 7154.67 7418.941 7644.231 7484.963 7237.468 600

6954.203 7216.265 7479.48 7709.653 7546.042 7299.767 700

7038.095 7275.333 7537.525 7772.409 7604.607 7359.51 800

7118.65 7331.88 7593.085 7832.506 7660.663 7416.702 900

7195.86 7385.914 7646.168 7889.95 7714.221 7471.353 1000

7269.717 7437.445 7696.786 7944.751 7765.291 7523.472 1100

7340.218 7486.485 7744.952 7996.921 7813.887 7573.072 1200

7407.365 7533.048 7790.681 8046.474 7860.025 7620.168 1300

7471.163 7577.151 7833.99 8093.426 7903.721 7664.774 1400

7531.619 7618.812 7874.897 8137.795 7944.994 7706.911 1500

7588.747 7658.052 7913.424 8179.601 7983.865 7746.598 1600

7642.563 7694.891 7949.592 8218.867 8020.357 7783.858 1700

7693.088 7729.355 7983.427 8255.617 8054.494 7818.715 1800

7740.346 7761.469 8014.953 8289.878 8086.302 7851.196 1900

7784.365 7791.26 8044.199 8321.678 8115.81 7881.327 2000

7825.177 7818.758 8071.193 8351.047 8143.045 7909.139 2100

7862.819 7843.994 8095.966 8378.018 8168.04 7934.662 2200

7897.329 7866.999 8118.55 8402.623 8190.826 7957.93 2300

7928.751 7887.807 8138.977 8424.899 8211.436 7978.975 2400

7957.13 7906.573 8157.283 8444.882 8229.905 7997.834 2500

0 500 1000 1500 2000 25006000

6500

7000

7500

8000

8500

Altitude

Energ

y W

h/m

2

= Optimumo

21-Mar

3-May

21-June

10-Aug

21-Sep

21-Dec

Figure (3): Variation of Solar radiation in different altitude and optimum daily tilt angle

surface


Vol. (19) No. (1) 2014


The data that is shown with optimum angle in Figure (3) verifies the

improvement in solar radiation at this angle with respect to fixed tilt angle. This

improvement varies in different times per year. The largest upgrading in solar

radiation is around summer solstice in June which is between 13.4% at sea

level and 16% above 2200 m. This upgrading is lower in winter solstice which

is between 8.5% at sea level and 11.7% above 2200 m.

The large increase in solar radiation in high altitude regions in summer owing

to adjust the tilt angle to optimal tilt is very important to substitute the decline

in solar radiation caused by cloud effect in mountain areas in Yemen.

The PV system can receive more solar radiation in high altitude regions better

than in low altitude regions. However, this improvement in solar radiation has

more significant value in winter solstice in December and January when the

system is tilted at optimum tilt angle as shown in Figure (3). This increase is

about 1680 Wh/m2/day when the altitude increases from 0 m to 2500 m which

is 26.8% in solar radiation. Besides this improvement in the solar radiation is

about 500 Wh/m2/day when the altitude increases from sea level to 500 for

optimum tilt system in this time. This increase is about 8% for this small

change in altitude. Within winter solstice the total improvement in solar

radiation is about 17% according to the change in tilt angle from fixed angle to

optimum and increasing the altitude from sea level to 500 m.

As observed from Figure (2) the minimum value of solar radiation for fixed tilt

angle surface is observed at zero altitude. In addition, in the regions near the

sea the high humidity decreases the total solar radiation which could be decline

the total solar energy per day to value under 5kWh/m2 within winter solstice for

the fixed tilt angle system. Hence the 17% upgrading in solar radiation caused

by changing the tilt angle from fixed angle to optimum and altitude increase

from sea level to 500 m. this upgrading in solar radiation can compensate the

decline in solar radiation caused by humidity.

4. Conclusions and recommendations

Based on the investigation given in section 3.3 the main conclusions and

recommendations from this study can be extracted as follow:

The minimum average daily solar radiation is in winter. For large

stations of grid tie PV system, the good selection of system location in

high altitude areas will increase the output of PV system due to the

upgrading in solar radiation. This upgrading in solar radiation due to


Vol. (19) No. (1) 2014


2500m increase in altitude from sea level is about23.2% for fixed tilt

system and 27.8% for optimum tilted system. Hence, if the grid tie PV

system is installed in high mountain regions the above percentages

increase in solar radiation will reflect equivalently in the output of PV

panel.

The additional 1076 W/m2/day in solar radiation in winter that is made

by select a good position of PV system by little change in altitude and

tilt angle is very useful for medium PV standalone station in coastal

cities which has small mountain like Aden Mokala and in rural regions

in Tehama near the mountain. This upgrade in solar radiation increases

the Peak sun hours of design month for PV system which is usually in

winter in these regions. The reduction in required PV owing the 1076 W/m2/day increase in solar radiation for similar electrical load is about 15%.

In several regions in Yemen the altitude could be increase about 1500 m

if the location of installed is changed from valley to the top of the

mountain. This large difference in altitude is very useful for the optimal

tilted system with design month peak sun around summer solstice or

winter solstice. This deduction can be observed from a large slope in

solar radiation between altitudes 0 m and 1500 m of fixed and optimal

tilt angle curves.

The horizontal slope of PV system has to be defeated to avoid the low

system ventilation as a result decline in PV efficiency regarding to high

cell temperature operation.

It could be observed around mid-tropical region there is a large effect of

altitude and tilt angle in winter due to the large deviation of zenith angle

on horizontal surface. As latitude increase in tropical climate and out of

tropical climate regions (above 23.5º)the incident angle of beam

radiation on fixed angle system will increase. The zenith angle in winter

becomes greater than 47º at mid-day, therefore, it is expected the effect

of altitude and tilt angle will be increased at this regions. Hence, more

studies are required to identify the effect of altitude in the edge and

outside the tropical regions.


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5. References

[1] The NASA Surface Meteorology and Solar Energy web site -

.http://eosweb.larc.nasa.

[2] John A. Duffie and William A. Beckman, “Solar engineering thermal

processes”, second edition, A Wiley- international publication, USA, 1991.

[3] Guglielmo S. Aglietti, Stefano Redi, Adrian R. Tatnall, and Thomas

Markvart "Harnessing High-Altitude Solar Powerexamined the possibility to

harvest solar energy in the high atmosphere" ,IEEE TRANSACTIONS ON

ENERGY CONVERSION, VOL. 24, NO. 2, JUNE 2009.

[4] Stefano Redi, Guglielmo S. Aglietti, Adrian R. Tatnall, and Thomas

Markvart, "Configuration Study of High Altitude SolarCollectors", IEEE

Electrical Power & Energy Conference, 2009.

[5] Tamer Khatib, A. Mohamed, K. Sopian, "The monthly optimum tilt angle

of solar panel forfive sites in Malaysia", IEEE International Power

Engineering and Optimization Conference (PEOCO2012), Melaka,

Malaysia: 6-7 June 2012.

[6] Anu George, Robins Anto,"Analytical and Experimental Analysis of

Optimal Tilt angle of Solar Photovoltaic Systems", International Conference

on Green Technologies (ICGT), 2012.

[7] DrissLahjouji, HassaneDarhmaouiin, "Tilt Angle Optimization for

Maximum Solar Energy Collection - Case Study for Ifrane, Morocco",

International Renewable and Sustainable Energy Conference (IRSEC), 2013.

[8] Tariq Muneer, C. Gueymard, and H. Kambezidis,"Solar Radiation and

Daylight"secondedition. ElsevierLtd, 2004.

[9] Air Mass and Insolation: http://pv education.org

[10] Tilt Angle: load tilts, optimal&not optimal, http://pv education.org

[11] William Brooks, James Dunlop, "Photovoltaic installer resource guide",

North American Board NABCEP, March 2012.

effect of altitude and tilt angle on solar radiation in tropical regions

Documents

solar radiation incident

introduction solar radiation

solar panel

tilt angle of pv system

global radiation

photovoltaic solar energy

altitude regions

design of pv system