Module Angle of Solar Panels
To get the most from solar panels, you need to point them in the direction that captures the most sun. The following advice applies to any type of panel that gets energy from the sun; photovoltaic, solar hot water, etc. We assume that the panel is fixed, or has a tilt that can be adjusted seasonally. (Panels that track the movement of the sun throughout the day can receive 10% (in winter) to 40% (in summer) more energy than fixed panels.)

1.  Orientation & Tilt Angle

The solar panel should be oriented to receive maximum incident solar radiation over the course of a year. The preferred orientation is facing south in the northern hemisphere, and facing north in the southern hemisphere. A simple rule suggested for the tilt angle is given in the table below.

Table 1. Solar panel tilt angle
Site Latitude (N or S)
Tilt Angle
0 - 10 degree
10 degree
11 - 20 degree
Latitude + 5 degree
21 - 45 degree
Latitude + 10 degree
46 - 65 degree
Latitude + 15 degree
> 65 degree
80 degree
* From Design Aids for Small PV Power Systems, Solarex Corp.

If seasonal adjustments can be made, some books give the advice that the tilt should be equal to your latitude angle, plus average declination for winter, or minus average declination for summer. The average declination is 11.75 degree (half of 23.5 degree).

2.  Design Guide for Chinese Cities [CECS 84:96]

The preferred orientation should be facing south. But if due to limitations of the topgraphy, surrounding and climate, the solar panel should be deviated not more than the latitude angle of the location from south.

(a)  Fixed installation:  Angle = Latitude + 10 degree (or the suggested angle given in Table 2 for major cities in China)

(b)  Installation with seasonal adjustments, twice each year:

      - Spring Equinox (20, 21 or 22 March):  Angle = Latitude - 11.75 degree

      - Autumn Equinox (23 or 24 September):  Angle = Latitude + 11.75 degree

(c)  Installation with seasonal adjustments, four times each year:

      - Spring Equinox (20, 21 or 22 March):  Angle = Latitude

      - Autumn Equinox (23 or 24 September):  Angle = Latitude

      - Summer Solstice (21 or 22 June):  Angle = Latitue - 23.5 degree

      - Winter Solstice (21 or 22 December):  Angle = Latitue + 23.5 degree

Table 2.  Optimum tilt angle (for fixed installation) of solar panels for major cities in China (in degree)

City (Province)
Latitude, L
Tilt Angle
City (Province)
Latitude, L
Tilt Angle
Harbin (Heilongjian)
45.68
L + 3
Hangzhou (Zhejiang)
30.23
L + 3
Changchun (Jilin)
43.90
L + 1
Nanchang (Jiangxi)
28.67
L + 2
Shenyang (Liaoning)
41.77
L + 1
Fuzhou (Fujian)
26.08
L + 4
Beijing (Beijing)
39.80
L + 4
Jinan (Shandong)
36.68
L + 4
Tianjing (Tianjing)
39.10
L + 5
Zhengzhou (Henan)
34.72
L + 7
Huhehaote (Neimonggu)
40.78
L + 3
Wuhan (Hubei)
30.63
L + 7
Taiyuan (Shanxi)
37.78
L + 5
Changsha (Hunan)
28.20
L + 6
Wulumuqi (Xinjiang)
43.78
L + 12
Guangzhou (Guangdong)
23.13
L - 7
Xining (Qinghai)
36.75
L + 1
Haikou (Hainan)
20.03
L + 12
Langzhou (Gansu)
36.05
L + 8
Nanning (Guangxi)
22.82
L + 5
Yinchuan (Ningxia)
38.48
L + 2
Chengdu (Sichuan)
30.67
L + 2
Xian (Shaanxi)
34.30
L + 14
Guiyang (Guizhou)
26.58
L + 8
Shanghai (Shanghai)
31.17
L + 3
Kunming (Yunnan)
25.02
L - 8
Nanjing (Jiangsu)
32.00
L + 5
Lasa (Xizang)
29.70
L - 8
Hefei (Anhui)
31.85
L + 9
      
* The optimum tilt angles in this table are estimated by computational methods, based on the adjustments from solar radiation intensity in Spring and Summer.

References

| Created: 24 Mar 2002 | Update: 24 Mar 2002 | By cmhui@hku.hk |