In the bleak mid winter

My monthly update is late as I wanted to see how the weather situation resolved, particularly with respect to the effect of snow on the panels. First is a graph of the past 34 days.


Notice how ten days are at zero. No appreciable power was generated because of the shading effect of snow on the panels, even when the Sun shone. If there is no more snow, then perhaps the recent fortnight might be the lowest point. What was remarkable was that a large portion of the panels could be clear but it took only a few percent coverage to completely short out the panels. A steeper roof would have cleared them more quickly. It has been an unusually snowy winter so far - and earlier than we are used to. Now on to the bigger picture:

This graph shows all generation since the beginning. The red line is the panels' 30-day average and the recent paucity of power has brought that figure down to only 1.54 units per day. The yellow line is the average daily power since installation. With ten days to the solstice, this figure is at 8.43 and continues to drop as expected. My hope is that by 18 May, it will be above 6.85. That would mean I had beaten the prediction of 2,480 units annually. I must say, it's starting to look like a close-run thing.

Hitting the bottom

Five days ago, winter came early to the UK and I learned what effect the snow has on a solar PV array. Basically, for me at least, it means zero power - even in bright sunlight. In the relative warmth of the day, the blanket of snow on the panels melts slightly and moves down the incline to expose up to 50% of their area. Yet apparently just having a portion of a panel shaded shorts out the whole panel and dramatically reduces its effectiveness. A trickle of power is generated but even after four days, it has not been enough to make my generation meter tick over one tenth of a unit.

Perhaps if the inclination of the panels had been greater, they would have shed the snow easier. As it is, I will just have to wait it out.

Having just got the payment for September's FiTs readings, EDF sent me an email for December's. We'll see if they pay this one faster. Only £130 is due this time.