Solar PV panels problem – can anyone explain?

Hi,

Can anyone shed some light on what’s going on with my panels please?

I have an older system that’s been in since 2012ish. A year ago the inverter packed up and I replaced it DIY. The new inverter has a real-time monitoring system and I can see what’s going on through an app on my phone (manufacturer is Solis).

The system capacity is supposed to be 2.25kW and for the first 8 months I saw peaks of 2.4 for short bursts (which I understand is normal) but on a standard sunny day I’d get a lovely parabola which topped out at about 2.2kW.

However, I’ve noticed since end of August the power output is down – I get peaks of up to 1.8 but on a standard sunny day I get the same shape curve but it peaks at 1.6kW. I seem to have lost 30% capacity ‘overnight’ – or at least within a few weeks of operation.

I know performance deteriorates over time, but my panels seem to have been performing to original spec 10+years after installation and suddenly lost it.

Given its age, the set-up is 9 panels connected in series to create a single array. In this config I’m told that if one panel is out, the whole array goes down, but it appears I’ve lost the majority of the output of up to 3 panels?

The only thing I can think is that the system overheated in the summer somehow and there’s either a thermal protection thing going on or I have a malfunctioning panel that is reducing the output of the system. Visually the panels look clean and there’s no cracks I can see…..

any ideas folks?

Do you have comparable figures from previous years? Could it just be the case that it’s a normal drop off due to seasonality (lower sun angle etc.) that you’ve not noticed previously?

Visually the panels look clean

From a distance or up close? There could be a film of dust etc. that’s not visible from the ground but could significantly affect efficiency.

My guess in winter. In august we would get 20-25 kWh on a good day, but yesterday was pretty much perfect and we got 7.5 kWh. That was with a peak of 2.5 kW instead of 4 kW in summer. I wouldn’t worry unless it doesn’t start tracking back up in the spring.

Sounds normal to me, your peak figure and total output per day will be considerably lower in winter then summer.

We have a South facing 4kw system and on a perfect summer’s day will max at 3.7kw and a total output of 30kwh, in winter that’ll be around 2.2kw with a total output for the day of 6kwh.

Very likely to be related to suns’ angle on the panels. 

Muck on the panels? Everything here a few months back got covered in Sahara sand or 5G particles or something.

I went to look at job yesterday where they had 12 panels on a flat roof installed 12 years ago. Access was easy so I could disconnect every panel and measure them individually. The open circuit voltage on each panel from new was 37 volts, after testing, they ranged from 5.8v up to 28v. Nothing had completely failed but there was a broad range of deterioration. We are going to be going back to the manufacturer to see what can be done – but I’m not holding my breath !

Well, after a bit of investigation it appears that it is indeed the season – I just wasn’t expecting to see the change so suddenly at the end of August into September.

Thanks for your suggestions folks.