When buying photovoltaic (PV) panels to generate electricity for their home, most people put them on the roof. However, this isn't the only place, and may not be the one that gives the best results.

Below is John Smith's story about his decision to site his solar panels in the corner of a field in front of his bungalow, and his efforts to ensure they are as productive as possible all year round.

"Having selected a likely area I marked the extent of all shadows from trees and buildings from dawn to dusk on a fixed date of each month for 6 months. To record the shadows I put up four wooden datum posts around the area and hammered a stout nail part way into the top of each. Choosing a suitable scale I plotted these on a large sheet of paper.

I marked the shadows with plastic electric fence posts, recorded their distance from each of the datum posts, transcribed it to the paper and labelled it with the month number. I plotted the direction of true west from a sun shot. After six moths it was clear that the south facing array would fit conveniently into only one spot where the cable run would not be excessive, our views not destroyed and others not affected.

We chose to mount the array in one line, running east to west, on a frame whose tilt could be seasonally adjusted. Freedom from shadows is crucial. South facing to within a few degrees is desirable. A frame is usually easy to adjust in tilt if access is reasonable and this can improve financial returns.

The best angle of tilt to use is a matter of some debate. Papers have been published showing theoretical calculations for desert areas and more empirical results for temperate areas. While every operator must consider their own ability and light conditions, my planned schedule for tilt angle, degrees, at latitude N 50.7 degrees is shown below.

January - 60
February - 58
March - 45
April - 31
May - 21
June - 16
July - 18
August - 27
September - 41
October - 54
November - 60
December - 60"

Photo by Coolstock

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