2023-05-04 11:29:32
At the end of April I was able to celebrate the first birthday of my new solar panels. Those 22 panels face east and west, instead of due south. Nevertheless, they performed quite well. And what a nice side effect is: my 12 oldies are still doing almost as well.
At the beginning of last year, I foresaw the arrival of a heat pump that would slurp electricity before the autumn, and an electric car would follow this year. So an extension of my modest solar park on my roof seemed desirable. The twelve panels from 2011, with a combined 2.76 kW peak (kWP: a measure that indicates how much power they can supply in a sunny hour on a day that is not too hot), were joined by 22 panels with a combined 8.58 kWP. The difference shows the progress we have made in 11 years: the old panels are 230 WP each, the new 390.
East-west is smart
My roof consists of two flat parts of 8 by 8 meters each. One part has virtually no shadow problems and that is where my old panels stood for eleven years, producing electricity neatly oriented towards the south. But that sunny spot was of course for my new battery of no fewer than 22 panels. However, in order to place them on that roof, they had to be placed east-west, with a very gentle angle of inclination so that they would not cast shadows on each other.
East-west produces less power per panel than facing directly south. But then you can fit a lot more panels and, not unimportantly: they then produce a little more power in the morning and afternoon peak. That is good for the grid, which is then under less load around noon, and it is good for the climate because we use more power in the morning and afternoon than around noon, so fewer gas-fired power plants are needed for those peaks. Thirdly, it is good for one’s own wallet if netting is phased out in the future. Because you often need the most power at home in the morning and the afternoon, and that power therefore comes to a greater extent from your own panels.
Much less sun this year
So much for the theory. My practice after a year is that the new panels produced 7790 kWh of electricity in the months of May 2022 to April 2023. That amounts to 908 kWh per kWP. My old panels averaged 950 kWh per kWP in that sunny spot. That makes a difference of only about 4 percent, which must be mainly the result of the east-west location and lower angle of inclination.
It is impossible to say exactly, because the number of hours of sunshine can vary considerably from year to year. Last year the summer was extra sunny, this year the first four months were much less sunny than average. In North Holland we even had more than 20 percent fewer hours of sunshine from January to April than last year! All in all, I’m guessing that the yield is pretty close to what I can expect on average in the coming years: about 8000 kWh. That is a very good result in my opinion.
Oldies in the lead
And my old panels? They are now on the roof part with more shade. Moreover, they are now 12 years old. They generated 2240 kWh from May to April, about 300 less than in their peak years on the low-shadow roof. The 2240 doesn’t disappoint me either, especially when you consider that when I placed my order in 2010 I was told that I could expect around 2300 kWh per year in a sunny spot.
And I don’t know why, but over the first four months of this year my old ones performed relatively better than the new panels: 199 against 196 kWh per kWP. Now that a huge oak is going to leaf out and cast its shadow over the twelve oldies, they will undoubtedly lose the battle. But I’m glad I didn’t just throw them in the trash last May. They are going to give me a lot of power for many years to come.
In his weblog ‘Vincent wants sun’, Vincent Dekker highlights innovations and developments in the field of green energy, close to and far from home. More episodes at Trouw.nl/vincentwilzon. Vincent now also has a podcast, including about heat pumps – listen to it via this link or look it up via the well-known channels.
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