Lecture 2 - Sun - Earth Geometry Notes

 Page 1


Solar Energy Technology - 2 
 
 
 
 
 
V.V.Satyamurty 
Professor of Mechanical Engineering 
INDIAN INSTITUTE OF TECHNOLOGY 
Kharagpur 721302, INDIA 
 
 
Page 2


Solar Energy Technology - 2 
 
 
 
 
 
V.V.Satyamurty 
Professor of Mechanical Engineering 
INDIAN INSTITUTE OF TECHNOLOGY 
Kharagpur 721302, INDIA 
 
 
 
Lecture 2 Sun - Earth Geometry 
 
 
 
Page 3


Solar Energy Technology - 2 
 
 
 
 
 
V.V.Satyamurty 
Professor of Mechanical Engineering 
INDIAN INSTITUTE OF TECHNOLOGY 
Kharagpur 721302, INDIA 
 
 
 
Lecture 2 Sun - Earth Geometry 
 
 
 
Sun 
 
Dia. = 1.39 ? 10
9
m 
        = 8.64 ? 10
5
 mi 
 
32 ? 
 
Ea rth 
 
127 ? 10
7
 m 
7900 mi 
 
Solar constant 
 
= 1353 W/m
2
 
= 428 Btu/ft
2
 hr 
= 4871 MJ/m
2
 hr 
 
G
sc 
 
Distance is  
 
1.495 ? 10
11
 m 
 
9.3 ? 10
7
 mi 
 
?1.7% 
 
 
SOLAR CONSTANT 
G
sc
, = 1377 W/m
2
 
Page 4


Solar Energy Technology - 2 
 
 
 
 
 
V.V.Satyamurty 
Professor of Mechanical Engineering 
INDIAN INSTITUTE OF TECHNOLOGY 
Kharagpur 721302, INDIA 
 
 
 
Lecture 2 Sun - Earth Geometry 
 
 
 
Sun 
 
Dia. = 1.39 ? 10
9
m 
        = 8.64 ? 10
5
 mi 
 
32 ? 
 
Ea rth 
 
127 ? 10
7
 m 
7900 mi 
 
Solar constant 
 
= 1353 W/m
2
 
= 428 Btu/ft
2
 hr 
= 4871 MJ/m
2
 hr 
 
G
sc 
 
Distance is  
 
1.495 ? 10
11
 m 
 
9.3 ? 10
7
 mi 
 
?1.7% 
 
 
SOLAR CONSTANT 
G
sc
, = 1377 W/m
2
 
E
sun
= ? A
s
T
4
 W 
?= 5.67 x 10
-8
 W/(m
2
K
4
) 
The variation in the total radiation emitted by 
sun is less than ? 1.5 % 
 
 
EXTRA TERRESTRIAL NORMAL 
RADIATION 
Page 5


Solar Energy Technology - 2 
 
 
 
 
 
V.V.Satyamurty 
Professor of Mechanical Engineering 
INDIAN INSTITUTE OF TECHNOLOGY 
Kharagpur 721302, INDIA 
 
 
 
Lecture 2 Sun - Earth Geometry 
 
 
 
Sun 
 
Dia. = 1.39 ? 10
9
m 
        = 8.64 ? 10
5
 mi 
 
32 ? 
 
Ea rth 
 
127 ? 10
7
 m 
7900 mi 
 
Solar constant 
 
= 1353 W/m
2
 
= 428 Btu/ft
2
 hr 
= 4871 MJ/m
2
 hr 
 
G
sc 
 
Distance is  
 
1.495 ? 10
11
 m 
 
9.3 ? 10
7
 mi 
 
?1.7% 
 
 
SOLAR CONSTANT 
G
sc
, = 1377 W/m
2
 
E
sun
= ? A
s
T
4
 W 
?= 5.67 x 10
-8
 W/(m
2
K
4
) 
The variation in the total radiation emitted by 
sun is less than ? 1.5 % 
 
 
EXTRA TERRESTRIAL NORMAL 
RADIATION 
 
G
on 
= G
sc
( 1 + 0.033 cos[360n/365] ) 
n is the day of the year, i.e., the sequential 
number of the day counting January 1 as 1. 
 
 
Sun is at an effective temperature of 5772 K. 
The solar constant is 1377 W/m
2
.