Solar Panel Guide Discussion

Cardew

ronlizpatsimon wrote: »

Good Evening Roxy,
I still find it hard to believe that any system can exceed its potential. I think you must have been standing on the apex of your roof, balancing a large mirror directing the sun at your panels!

What do you mean by 'potential'?

The rating on a panel is that achieved in laboratory conditions at a set temperature and sunlight(luminescence)

So the potential of a, say, 250w panel might be well in excess of 250w in UK - over 300w in Spain.

The limiting factor of most PV systems in UK is the output of the Inverter.

zeupater

Cardew wrote: »

What do you mean by 'potential'?

The rating on a panel is that achieved in laboratory conditions at a set temperature and sunlight(luminescence)

So the potential of a, say, 250w panel might be well in excess of 250w in UK - over 300w in Spain.

The limiting factor of most PV systems in UK is the output of the Inverter.

Hi ronlizpatsimon/RoxyK

To add to Cardew's post above, the nominal performance is rated at 1000W/m2 @ 25C, so cool panels at 10C could give arount a +5% to +7% increase if receiving a direct 1000W and cloud edge could have an additional effect resulting in a few extra percentage points too .... then again there's the manufacturing tolerance on the panel performance which could add another +3% to +10% to the output if the pack received is towards the higher end of the band.

Perm the possible variables and you can exceed the nominal rating of the array for short periods ... however, the inverter rarely registers these momentary peaks as the recorded generation is usually averaged over a period which is long enough for the panels to warm a little and the cloud edge effect to be diluted by time ...

HTH
Z

ronlizpatsimon

Cardew,
What I meant by potential was the official rating of the array. I can agree with "zeupater" that variations are possible but consider this:- If you have a set of 250w panels and mount them in the UK or in the tropics, their official maximum wattage is surely the same. Its just that 250w is more easily reached in the tropics. Not only is the UK far from the tropics, but we are only about halfway between our best chance of high generation and our worse generation.

RoxyK

ronlizpatsimon wrote: »

Good Evening Roxy,
I still find it hard to believe that any system can exceed its potential. I think you must have been standing on the apex of your roof, balancing a large mirror directing the sun at your panels!

LOL darn you got me!

I always wondered why my inverter was 4.4 for a 3.84kWh system. Makes sense now. So interesting.

RoxyK

zeupater wrote: »

Hi ronlizpatsimon/RoxyK

To add to Cardew's post above, the nominal performance is rated at 1000W/m2 @ 25C, so cool panels at 10C could give arount a +5% to +7% increase if receiving a direct 1000W and cloud edge could have an additional effect resulting in a few extra percentage points too .... then again there's the manufacturing tolerance on the panel performance which could add another +3% to +10% to the output if the pack received is towards the higher end of the band.

Perm the possible variables and you can exceed the nominal rating of the array for short periods ... however, the inverter rarely registers these momentary peaks as the recorded generation is usually averaged over a period which is long enough for the panels to warm a little and the cloud edge effect to be diluted by time ...

HTH
Z

Very interesting explanations My inverter produces a daily graph and these peaks did not last long at all, just glad they are recorded as its quite fascinating.

I managed to remember how to do a screen print so at least I have it permanently

davidanddeirdre

ronlizpatsimon wrote: »

Cardew,
What I meant by potential was the official rating of the array. I can agree with "zeupater" that variations are possible but consider this:- If you have a set of 250w panels and mount them in the UK or in the tropics, their official maximum wattage is surely the same. Its just that 250w is more easily reached in the tropics. Not only is the UK far from the tropics, but we are only about halfway between our best chance of high generation and our worse generation.

Very interesting points. Especially about the tropics and comparison with the UK. Our big disadvantage of course is the variation through the year, short days and sometimes very overcast ones in the depths of winter, but we must score relatively in other ways, which may give us temperate latituders an overall advantage. For example, on the equator,
1. The theoretical best inclination for panels would be horizontal, which would have the big disadvantage of collecting a lot of dirt, and getting very hot around midday, I should think. Putting them at a slope to keep them clean and cool would also reduce insolation to them and thus potential output.
2. We have a generally cooler climate than the tropics, which gives us a more efficient panel performance most of the time (particularly noticeable at this time of year)

sly_dog_jonah

I've seen 3.82kW instanteous output from our 3.7kW array connected to a 3.68kW inverter (measured using a SoloPV reading the TGM LED). It didn't last long, but Iong enough to get a photo.

grahamc2003

Interesting points about the reflected and refracted light effect. It looks like typically, the amount of direct radiation (i.e. from the sunlight direct from the sun) is about 50% of the total generation - the other 50% being reflection and refraction from clouds (and I'd say most of that is refraction). Before I googled around, I would have expected the direct sunlight to be by far the major contributer.

It does explain my situation, where two days ago I had the massive tree my panels pointed at 'pruned' (I asked them to leave about 10 feet of what was an estimated 70/80feet beech). In the 2 dull days since then I've generated around 3.5kWh/d, whereas before, such a day would give me about 1.5kWh (from a sw facing 45degree 1.75 system). Today I saw my highest peak, which was 1.7kW (although the nominal max of the inverter is 1.6kW). The sunny days generated about 7.5kWh with the tree - just waiting for a sunny day now to see how that has improved - I'm expecting around 9.5kWh/day max at this time of the year, which I think is OK for such a small (and inexpensive) system.

ronlizpatsimon

Good Afternoon Graham,
Your post is interesting.
Which town are your panels installed in?
No sun at all here today - just rain!
2.2 kw today - so far

davidanddeirdre

grahamc2003 wrote: »

Interesting points about the reflected and refracted light effect. It looks like typically, the amount of direct radiation (i.e. from the sunlight direct from the sun) is about 50% of the total generation - the other 50% being reflection and refraction from clouds (and I'd say most of that is refraction). Before I googled around, I would have expected the direct sunlight to be by far the major contributer.
It does explain my situation, where two days ago I had the massive tree my panels pointed at 'pruned' (I asked them to leave about 10 feet of what was an estimated 70/80feet beech). In the 2 dull days since then I've generated around 3.5kWh/d, whereas before, such a day would give me about 1.5kWh (from a sw facing 45degree 1.75 system). Today I saw my highest peak, which was 1.7kW (although the nominal max of the inverter is 1.6kW). The sunny days generated about 7.5kWh with the tree - just waiting for a sunny day now to see how that has improved - I'm expecting around 9.5kWh/day max at this time of the year, which I think is OK for such a small (and inexpensive) system.

Dear Graham2003, you must be a young fellow, sounds about right. We have 10 X Sharp 175w panels, c. 40 deg slope, facing slightly E of SE. There is no shading except for minutes after dawn (distant trees, roofs, electric cables). We started March 2011. I'm not always here to get the daily total, but the biggest recorded day so far was last June 3 exactly 12 units. April 1st this year, (no joke!), was 9.22. Both I recorded as cloudless days, at least during the time direct sun was on the roof.
NB hope you got the logs off the tree!