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Question 7.2: Tilt Angle of a PV Module. Find the optimum tilt angle for a......

Tilt Angle of a PV Module. Find the optimum tilt angle for a south-facing photovoltaic module in Tucson (latitude 32.1º) at solar noon on March 1.

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From Table 7.1, March 1 is the sixtieth day of the year so the solar declination (7.6) is

\delta \ = \ 23.45 \ \sin \ \left[\frac{360}{365} \ \left(n \ − \ 81\right)\right] \ = \ 23.45º \ \sin \ \left[\frac{360}{365} \ \left(60 \ − \ 81\right)º\right] \ = \ −8.3º

which, from (7.7), makes the altitude angle of the sun equal to

\beta _{N} \ = \ 90º \ − \ L \ + \ \delta \ = \ 90 \ − \ 32.1 \ − \ 8.3 \ = \ 49.6º

The tilt angle that would make the sun’s rays perpendicular to the module at noon would therefore be

\text{Tilt} \ = \ 90 \ − \ \beta _{N} \ = \ 90 \ − \ 49.6 \ = \ 40.4º
TABLE 7.1 Day Numbers for the First Day of Each Month
January n = 1 July n = 182
February n = 32 August n = 213
March n = 60 September n = 244
April n = 91 October n = 274
May n = 121 November n = 305
June n = 152 December n = 335
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