Energy Matters Forums

[sidney001]

My question is, my understanding that in the northern climates (45 degrees latitude) the rule of thumb for setting the array row spacing for larger installations, (>100KW) is: on the winter solstice, at noon, the row in front shades just under the bottom panel of the row behind it. That would mean by 2:30pm on the solstice, the bottom panel of the entire row, all rows of the array except the front row are shaded and the system is shutting down. The engineers virtually forgo the months between Nov, Dec, Jan, Feb, with the sun being low, snow cover, clouds and such its not worth the extra spacing.

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[Inspector]

Have you had a look at the CEC Tech Info March 2010? It provides details and calculations to provide unshaded sunlight access to panels between 10am-2pm. Ideally a longer time would be preferable but space considerations might be a limiting factor.

I've seen some downright ridiculous systems in the past 3 or so years, the largest being about 30kw of panels with the majority of them being too close. The "designers" considered it was "within spec" for them to be too close, stating the system was designed for "summer output" but I still believe a higher overall yearly output would've been achieved from fewer panels at the correct spacing given the bottom edge of panel were shaded before 11am and it wasn't even close to winter solstice.

[sidney001]

space for our system was a limiting factor, we only had 10,000 sq.ft. to work with as dictated by the planning commission. So the contractor installed the extra panels that will receive more sun during the summer months and basically let the winter months dwindle away.

[Gordon-Loomberah]

If you have more than 1 MPPT input, then the back row can be tilted up more than the front row, to avoid shading altogether.

There's a large (I assume 10kW) array on trackers in a paddock down the road from me, installed earlier this year- 5 trackers on an ~E-W alignment. I thought at the time they were being installed that it was definitely the wrong alignment for the spacing they used, and sure enough, I passed by mid-late afternoon last month each tracker was partially shading the next. That there is any shading when there is heaps of space in the paddock, shows very poor layout design, the owner probably isn't going to get more power on the longer days of summer. I suppose there is a chance production might even go down due to the shading on the longer days...