West facing solar panels output

insular1 · 04-06-2021 9:16am #1

Hi all. Have recently had solar installed on a West facing roof. It's a 3.6kWp set up. Panels are set in 3 strings with each string on a 1200w microinverter.

It seems to be producing reasonable well but with the really sunny days over the last week it has only ever peaked at 2800 watts. I'm wondering is this normal for a West facing array or should I be seeing closer to the 3600w peak? I'm thinking it's possible that one of the strings may not be working? But in that case I would have thought the max I would see would be 2400w?

Any one with a West facing set up comment if it's normal to see a max output of only about 78% the kWp of the array?

ParkRunner · 04-06-2021 12:14pm

I think about 80% is the max output you’re going to get from a solar array regardless of the direction it is facing or the conditions due to loss during the conversion and limitations of the technology - others may be able to explain the maximum output possible better than I can, but you wouldn’t ever get near 100% output.

With a south facing 6kwp system the most I generate is usually 4.7-4.8 Kwh in the sunny south east.

idc · 04-06-2021 2:03pm

I have a 4.65kWp system split 7 South East and 8 South West and I regularly exceed that, not for sustained periods but on a cloudy day more than a clear day. Others have commented in other threads that when panels are hotter they can produce less hence you may not hit the max, whereas on cloudy day where you get occasional windows of plenty of sun but panels are not very hot you can see very high spikes - one day in May when i was averaging 1.5-2 kW most of the day I had a 10 spikes above that, most below my 4.65 but then i had 3 at 4.74, 4.78 and 5.1 kW.

insular1 · 04-06-2021 3:26pm

Thanks all. Yeah I thought I'd read in another thread about people occasionally exceeding the kWp of their set up. That would fit with my theory that one of the strings is not hooked up right as I saw 2800w as my max a few times but never higher. This would be exceeding the 2400w I would expect from two of the strings but at least 20% less than I would expect from the full 3 strings. I was wondering if mine were seeing lower peaks as they are due west. Think I'll contact the installer and see what they say.

KCross · 04-06-2021 3:38pm

insular1 wrote: »

I was wondering if mine were seeing lower peaks as they are due west.

I’d say that ^

Do you have the ability to login to the inverter and see what each string is generating. You’ll have your answer then.

handpref · 04-06-2021 7:39pm

insular1 wrote: »

Thanks all. Yeah I thought I'd read in another thread about people occasionally exceeding the kWp of their set up. That would fit with my theory that one of the strings is not hooked up right as I saw 2800w as my max a few times but never higher. This would be exceeding the 2400w I would expect from two of the strings but at least 20% less than I would expect from the full 3 strings. I was wondering if mine were seeing lower peaks as they are due west. Think I'll contact the installer and see what they say.

Do get your installer to check and show you the generation from each string if possible. It may be visible from the systems portal.

I say that because my installer trusted the cabling to the roofer and you just don’t know unless it’s double checked.

Was there a commissioning sheet?, because it should be on that what figures were generated from each string when the system was commissioned.

No commissioning sheet - ask why not, there is no excuse for that.

For what it’s worth I have 5.4kwp east west split-9 on each side.
My peak of about 4.2 is usually between 1-3, once the sun passes onto that west side the east is becoming redundant, most I’d get is 3kw’s peak.

Alexa111 · 04-06-2021 7:39pm

tHANKS

insular1 · 04-06-2021 7:48pm

Gonna check the inverters to see if I can log into them but they're micro inverters so not sure how to go about that. I'll have a look at the paperwork the installer gave me to see if there is anything about commissioning noted there.

However after all that today I did actually see my first peak just over 3kw so probably just the orientation affecting them. Didn't seem like as sunny a day so possibly the scorchers we had early in the week just had the panels running too hot. Thanks all for the input.

06-06-2021 11:07am

Had the same question myself about a week ago. I am west facing with 3.2kW, first day with no clouds in the sky and it peaked at 2.3 while other cloudy days it was hitting 3.2 when the sun was out. A poster here said about inefficiency when panels get too hot. Monitored the panels in the days after and it was in fact hitting 3.2 again. Researched it and panels have an ambient temperature and anything above makes them inefficient to the pro rata of temp increase. In France they are cooling panels with water.

The installer conveniently does not tell you this, well mine didn't anyway. I was planning loads on corks only cloudless day last week but didn't happen. I know now what to expect in future. Unless you pipe water to your panels to intermittently cool them on a scorching days you won't get your max output

West facing solar panels output

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