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I'm wondering how other owners are impacted by the current excess heat in the sun. My panels are mounted on a steel profile roof, which I guess is probably too hot to touch at present. My daily output is down by about 5Kwh compared to what would be 'normal' on a 3.87 kw array. I'm on a early FIT so don't need to worry about export income but any new owners will be a bit p**d off when the production is not as predicted.

How does the cost of a (mains water) spray - if you can reach it - compare with the increased generation it might bring?
(Granted, people on meters pay for disposal of all incoming water even if they consume it on-site, although people not on meters can use it will-nilly!)

I have circa 12kW of PV, with inverters capped to 9kW and my export capped to 3.68kW. From March to May in full sun, 9kW is achieved as long as there are enough loads to power which there normally is.

June, July and August are months which I don't usually need any heating, so curtailment because of the max export limit usually is the larger factor that affects me over high temperatures. But any reduction in output during those months is irrelevant to me apart from a small loss of FITs.

Today fairly warm, but not too hot, about 25 degrees and the max output today when not curtailed was about 7.5kW in full sun. I will check again over the next 3 days to see how low it goes.

AE-NMidlands wrote: ↑Sat Jul 16, 2022 6:38 pm How does the cost of a (mains water) spray - if you can reach it - compare with the increased generation it might bring?
(Granted, people on meters pay for disposal of all incoming water even if they consume it on-site, although people not on meters can use it will-nilly!)

In the early days,2011, I didn't believe the story of panels being too hot so I put a lawn sprinkler on the roof which did increase output BUT as I'm on a borehole the extra power was more than consumed by the 2 pumps involved. I have not repeated the exercise.

We have 6kWp of south facing PV and it's struggled to hit 5kW for the past few weeks. I think we got around 5.5kW when it had been fairly cool overnight a week or so ago, but today the highest we managed was about 4.5kW. There doesn't seem to be anything wrong as far as I can see. Both strings are delivering about the same, so I don't think we have a problem with a panel or connector. We're still generating around 30 to 35kWh per day, but we have hit over 40kWh per day in the past. The system's about 10 years old now, so maybe there is a bit of age related degradation, plus it's at a steeper than optimum angle for midsummer. I guess all the little losses add up when conditions aren't ideal.

Heat is hitting our power, seeing about 2.7kW, whereas I'd expect with clear skies more like 3.2, to 3.5, even 4.2 sustained with some wind. But, still hitting energy levels of low 30kWh per day, which is excellent for us, max ever is 35kWh. So low flat generation, but dusk till dawn, so no complaints.

Edit - LOL, dusk to dawn generation would be really nice, but I think dawn to dusk is far more likely.

We're not complaining as we're on 2011 FIT so export does not effect our income and the slightly lower figures for total generation in the scheme of things is not a lot. Our current FIT is £0.625 per unit this year (including the 50% deemed export).

I'm seeing about 300-320W around midday here with the temp up in the low thirties. Normally at best I see 480W when bright but cool. This works out a bit over 100W/m2, or about a 10% conversion of the solar insolation, which is pretty shonky when compared to the solar thermal IIRC. I did do a load of calcs over on "the other side" but I don't think I still have the data, I may run the experiment again sometime.
Not that I am complaining, the system cost next to nothing so it is great

Desp

It's really reassuring to hear that others are seeing the same sort of output reduction in this weather. I've only really been looking at the data closely over the past year or so since I fitted remote monitoring so I can call up a display on the PC and see what's going on. Our system output may well have been dropping a lot in hot weather in previous years and I wouldn't have noticed. It's only really since I fitted a Raspberry Pi running Grafana earlier this year that I've had a natty display showing what everything is doing.

It's great watching the detail but does get a bit obsessive at times. I often find myself looking at the data and then thinking "Why on earth is it doing that?", which then prompts a wander out to the battery shed or up to look at the display on the Eddi to try and work out what's going on. SWMBO reckons I'm obsessed with micro-managing things, but she was still working back when I was running our old system with the big bank of NiFe cells, so didn't get to see what I got up to then. The old NiFe cell system worked well but did need a lot of attention, not least because the cells I was using were ex-RAF starter packs dating back to around 1950. Better not going on about them though, doing that on the other place got me banned. Still got a soft spot for them, though, as they will easily outlive me.

I've just taken reading of our system before and after sprinkling with the hose pipe, 385-395Wbefore, 425-435 after, almost a ten percent difference.
That was done twice and an average of three readings as the display cycled was taken. The sunlight is almost normal to the panels and the cloud/transparency of the sky didn't noticeably change.

That is a bigger difference than I was expecting but our panels are old stock sold off cheap by "the other lot" so could be old tech?

Desp