Sometimes you need to remove a shadow…

It’s nine days to the solstice. I took this picture at about quarter to nine…

…and if Landlady’s batteries were under any evening load at all this picture would not be acceptable. In fact this only happens in the month or so before and after the solstice. But if the house were occupied…

I would suggest that this tree be sent to meet Juniper Jesus. Or at least severely trimmed. Landlady prefers a tree there to a stump, so there it stays. But come the day the house is occupied, that rule may need to be revised on the first winter it becomes a problem. Shadows are one good reason to position solar panels as high as possible – of course there are also good reasons to keep them low, like snow removal. Either way: Location, location, location.

About Joel

You shouldn't ask these questions of a paranoid recluse, you know.
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6 Responses to Sometimes you need to remove a shadow…

  1. Jim Price says:

    Well, . . . I guess if she really likes the tree, the only other option is to move the solar array.

  2. Joel says:

    Unfortunately too far further from the tree and you get afternoon shadow from the barn.

  3. terrapod says:

    Raise the array 12 feet up into the air and you have solved the shadow problem 😉

  4. s says:

    Does the tree shadow really make that much difference in terms of actual energy delivered from the panels? At 8:45 AM the sun has been up about 90 minutes, the picture shows that the sun’s elevation is pretty low, maybe 15 degrees. That means reduced power from the panels.

    A solar website says that at this time of year the sun in your area doesn’t get to 20 degrees above the horizon until about 9:30 AM. By that time the shadow of that tree won’t be on the panels.

  5. Joel says:

    S, I really don’t know for sure. But shadows definitely have a dramatic effect on output while they’re there, and near the winter solstice there’s not always enough sunny hours in a day. The effect on overall battery charge can be cumulative if they’re regularly pulled down during the dark hours.

    So just in general I consider it a bad practice to allow any shadows at all if it’s possible to eliminate them.

  6. s says:

    No argument there, shadows are the enemy of solar.

    The solar site I found gave me enough info to estimate the effect of morning shadows. If the output of the panels was pulled to zero until 9 AM this time of year, it would cost at most 15% of the total available energy. But that doesn’t include dimming of the light when the sun is low on the horizon and the light has to pass through more miles of atmosphere. The actual energy available in those morning hours is probably closer to 10% of the total available in a day..

    But the panels don’t go to zero, maybe to half, so the net effect is probably about 5%. Not nothing, but also not that much. Normally you’d want the batteries to reach full charge every afternoon, and if that happens the 5% or even 10% makes no difference at all. If the batteries are not recharging most sunny days, there is a mismatch between demand and supply.

    In the end, I suspect there would be a larger difference if the panels were angled lower in the winter and higher in the summer. I’m not suggesting you do that; too much work. Just trying to put the effect into perspective.

    Tell Landlady it is a nice tree. 🙂

To the stake with the heretic!