Effects of shade on solar panels like a Magdalen to King's Lynn drive being blocked by a fallen tree
View From a Shed by Kevin Holland
It was about 10 minutes after switching on my first solar system back in 2011 that I started to notice the effects of shade on solar panels. And it genuinely blew me away when I saw the amount of energy being lost due to such a small amount of shade.
All solar panels need an 'even bathing of light' for them to perform. Think of a panel like a road network. Each cell is connected by wires and if any cell is shaded, this will have an effect on the output of panels. Same as if I was driving from Magdalen to King's Lynn on the back road and the road was blocked by a fallen tree, I'd have to stop, turn around and go the long route. I'd still get there, just much less efficient.
Solar panels generate energy in DC and the inverters convert that DC to AC so it can be used in our houses. When all panels are 'strung' together through one inverter, the effects of shade are more noticeable.
However, there are products on the market to help negate these effects and when optimisers are placed under each panel, it allows each panel to operate on its own merits and only the shaded panel will reduce its output. Microinverters are even better and having one fitted to each panel will allow the whole system to operate at its absolute best, whilst increasing performance as you convert the DC to AC at point of source, on the roof.
Having this knowledge is great for our clients, but when I drive by solar systems that are so close to shade from chimneys, flus and on some occasions, ground mounted systems placed in front of a thick metal railings, it makes me wince at the prospect of all that money have being spent only to find out the system will never perform as intended due to shading elements.
In the summer months, I lose around 7% output as a half inch thick wire casts a shadow for an hour and 32 minutes every day across my panels. In the winter, over 75% loss due to the pole that carries the wire that comes into play when the sun is lower!
December 21st is the shortest day, and it also happens to be the best day to find out the best place for solar on your own home. If we have a clear day on or around the 21st, pop outside and have a look at your own roof and see where the sun falls. The clearest area on the shortest day is the best place for solar all year round.
There are many tools we use to check for shading, but find Sun Surveyor Pro about the best. It allows you to track the sun's path through your phone's camera on any day of the year.
Finally, for our last column of 2022, here's some solar facts about the PE30 postcode and surrounding area.
1. A 10 panel, 4kw solar system will generate around 4,000kwh a year on an unshaded, south facing roof.
2. The same system, split over east and west facing roofs will generate around 3600kwh a yr
3. Going north only, will see around 2,700kwh a year being generated.
It's a fallacy that solar needs to be on the south roof as east, west and north will allow a homeowner to generate their own power. The south just happens to be better, but not exclusive for solar generation.
All that remains to wish each and every one of you a very happy winterfest and a glorious, shade free, sun baked new year!
