Slow starting solar- any ideas why?

Heedtheadvice

Oooooh we will really get into complex technical discussions if you need a full explanation, and probably beyond me!


However to try and help.
The cells are made of semiconductor diodes that generate an electromotive force (what we commonly call a voltage) wnen a 'bandgap' figure is exceeded and they can then deliver electrons as a current. So a minumum illumination is required to start generation.
The relationship between that emf and the current is not linear but logarithmic so the output voltage tends to stabalise whilst the current can increase as higher levels of illumination occur. Hence the fairly 'static' voltage whilst not at extreemly low levels of 'sun' power received (start up conditions).
The cells are also in an electronic circuit so the load (inverter) has an effect too.
Unlike a battery that tends towards constant voltage output the solar cells tend towards contant current output so there are complex interactions taking place. If reall interested there is a good technical article at https://en.m.wikipedia.org/wiki/Electromotive_force#Solar_cell


So we are left with, at low energy/'light' levels, lower values of generated voltage that need to exceed a threshold before generation. All the cells and for a single string are connected in series so their voltages need to add up to that '100v'minimum that is a function of the invertor design. The more panels and cells (once generation has overcome the bandgap) the earlier that 100v is reached.

So it can be seen that there are a lot of factors affecting the situation.
16 panels ought to reach that 100v threshold sooner all other things being equal - which they will not be!


As regards cloud cover: bright sunlight suffers most from shading owing to shadows even when only on part of a string owing to that series connection mentioned above being (at least)partially broken. Progressively as it gets more cloudy the illumination becomes dispersed (efectively no longer a point source with strong shadows) shading is less of a problem but generation is substatially reduced.


Why are you so concerned about start up? Overall you may miss an hour of very low generation but that should be more than matched once generation has started, should it not?


Do enjoy your tea!!

JKenH

Thank you, Heedtheadvice for that explanation.

You are quite right, the amount lost is not that great (enough for my morning cuppa) but waiting an hour for my panels to wake up makes me think I might be missing out on a lot more.

zeupater

Hi

No need to worry about current & power as there won't be any until the DC side is switched on, so all you're interested in is the DC voltage threshold across the panels that is needed for the inverter to switch on ...

HTH
Z

JKenH

Hopefully my late starting issue has now been resolved with a change of inverter to Solis. The new inverter is starting up much earlier at 33 watts (168.5 volts dc, 0.1 amps x 2 strings if anyone is interested.) I had taken to monitoring the old inverters with the Solarman app and it was taking approximately 90 watts before they got going. They are still not starting up as early as my near neighbour’s Solar Edge system which displays power as low as 5 watts on start up!

The new inverters also stay on much later. Last night it was 5.27pm when the second one switched off at 10 watts and it was dark outside - more than an hour after the nearby Solar Edge system under overcast skies.

Some of you may recall I have also had a problem with my inverters/panels tripping the RCD on start up. The RCD had been changed a month ago from 30 to 100 mA but it didn’t solve the problem. Although the new inverters only went in on Monday so far they have started up both mornings without tripping the RCD. Fingers crossed.

My latest problem is trees! I cannot believe how low the sun’s trajectory is as we approach the winter solstice and almost 2 months still to go. I can only blame myself as I did plant several hundred when we moved here 28 years ago. During the summer I never imagined they would interfere so much in the afternoon - from about 3pm my west facing panels are in shade. At least I won’t be short of firewood next year.

I am also suffering from distant trees on the horizon first thing in the morning which just weren’t a problem a month ago and a nearby giant Leylandii which robs us of 15 minutes sun in the morning. I suppose I should take some comfort from my PVGIS daily estimate only being 0.65 Os in November and 0.42 in December so there isn’t a great deal to lose.

Does anyone else find trees (or neighbour’s chimneys and roofs) a big problem this time of year?

Finally, some of you may have noticed something has disappeared from my signature. If you are interested please pm me.

zeupater

JKenH wrote: »

... Finally, some of you may have noticed something has disappeared from my signature. If you are interested please pm me.

Hi

Binned the batteries for a while ??

Z

ASavvyBuyer

JKenH wrote: »

I am also suffering from distant trees on the horizon first thing in the morning which just weren’t a problem a month ago and a nearby giant Leylandii which robs us of 15 minutes sun in the morning. I suppose I should take some comfort from my PVGIS daily estimate only being 0.65 Os in November and 0.42 in December so there isn’t a great deal to lose.

Does anyone else find trees (or neighbour’s chimneys and roofs) a big problem this time of year?

Our problem is the mountain we live on, from now until about mid February we get very little direct sun (if any) because the sun goes below the horizon for most of the day.

Our PVGIS estimate from Nov - Feb is between 0.25 & 0.5 O's a day.

The view is nice though, towards the Brecon Beacons

JKenH

:

zeupater wrote: »

Hi

Binned the batteries for a while ??

Z

:T For now.

zeupater

JKenH wrote: »

:

:T For now.

Hi

Storage capacity not sufficient & energy management system capabilities disappointing? ...

Z