Renewables: "talking 'bout my generation"

sly_dog_jonah

Notched another 22.6kWh yesterday which nudged our 7day average up to 20.8kWh and 14day up to 17.3kWh. 30day average is still 1.5kWh below the peak of 15.3kWh reached in mid-April.

Depending on the next few days we should beat PVGIS by 10-15%, happy days!

Martyn1981

jackieblack wrote: »

I certainly didn't intend to come across as smug, apologies if it did.
I've always been curious as to whether 16kWh is likely to be the maximum, for us, for any single day. The days that have been '16' days have, so far, all occurred in the month of May.

Not at all Jackie, quite the opposite. I was suggesting that if you wanted to do a little 'smug dance' then I'd happily cheer you on. :T

I think my max is 24, but it all depends on afternoon weather. Got a couple of 22.5's.

May the sun keep shining, or the May sun keep shining!

Mart.

Kernel_Sanders

KevinG wrote: »

I used a wet towel wrapped around the end of an extendable cobweb brush thing and stood on a platform ladder (luckily it's a bungalow so not too high).

I would never rub my panels with a towel, or anything else other than fine bristles (such as on a car washing brush). You may have made tiny scratches in your glass caused by minute particles of grit already sitting on it. You won't notice any reduction in generation, but over the course of decades I would have thought that the accumulated losses would far exceed the small gain you made by your efforts*.

KevinG wrote: »

Yes, my 2kWp SSE facing system has never quite managed to exceed 13kWh. What's the rating of your inverter? I'm fairly sure mine is limiting the output as although it's rated for a maximum of 2kW of panels, its rated maximum output is 1575W and I have only occasionally seen higher than this.

Why did you not have an inverter matched to the kWp of your panels? Mine has max input 4200W (DC) with 4000W (AC) output. Are these the two ratings to which your figures correspond?

* Or for Eric, 'the small loss that you avoided'

rogerblack

Kernel_Sanders wrote: »

Why did you not have an inverter matched to the kWp of your panels? Mine has max input 4200W (DC) and 4000W (AC) output. Are these the two ratings to which your figures refer?

The losses from having too small an inverter are very small, unless you go _very_ much larger.
For the vast majority of the day - even on good days - a solar system will not be outputting at peak.

For example.
Take the graph at http://pvoutput.org/intraday.jsp?id=3744&sid=2940&dt=20120526

This shows a beautifully sunny day - with generation from 5AM to 5PM.
It's a 3.75kW array, and peaked at 3.2kW.
If, for example, you had put a 3000W inverter on it, on this day, you'd have lost about .5kWh.

But this is the worst case - pretty much.
The losses are way, way smaller than 165kWh/year - simply as most days are not this good.
It only exceeds 3kW by much when it's a very sunny day between 10AM and 2PM or so.
If it's sunny at any other time - it doesn't hit the limit.
If it's even slightly cloudy - it doesn't hit the limit.

I did some numbers using the above installations generation figures - taking the 10-minutely data - and computing what-ifs about panel/inverter size.

If you double the panel size - you only lose 20% off the top of generation.

Kernel_Sanders

The Sun just emerged for the first time in four hours. I looked to see if I had the requisite 2900W with which to top up the immersion heater and was quite taken aback to see it displaying 4187W; I haven't seen anything like that for a while! Can this really be due to a sudden lack of haze, or is the 'cloud reflection' effect more marked than we thought?

EricMears

Kernel_Sanders wrote: »

The Sun just emerged for the first time in four hours. I looked to see if I had the requisite 2900W with which to top up the immersion heater and was quite taken aback to see it displaying 4187W; I haven't seen anything like that for a while! I didn't realize that the 'cloud reflection' effect was so marked.

We must be all of 10 miles apart but weather couldn't be more different !

Here we've had bright sunshine virtually all day with just the occasional cloud scudding by. No idea what our best instantaneous result might have been but of the 5min averages logged we've had several in excess of 3Kw & an absolute best (@14:20BST) of 3.5Kwh - which was also best this week. BUT we've also had several dips - some right down below 1Kw.

Daily yield was 13 Kwh at 3pm; anything might happen between now & 9pm !

Kernel_Sanders

EricMears wrote: »

Here we've had bright sunshine virtually all day with just the occasional cloud scudding by.

Daily yield was 13 Kwh at 3pm;

Those two statements don't appear to tally, unless haze has increased.

Currently, I'm on 11.50 kWh

KevinG

Kernel_Sanders wrote: »

I would never rub my panels with a towel, or anything else other than fine bristles (such as on a car washing brush). You may have made tiny scratches in your glass caused by minute particles of grit already sitting on it. You won't notice any reduction in generation, but over the course of decades I would have thought that the accumulated losses would far exceed the small gain you made by your efforts

I'm surprised at that suggestion - I thought a wet towel was about the kindest thing I could have used.

Kernel_Sanders wrote: »

Why did you not have an inverter matched to the kWp of your panels? Mine has max input 4200W (DC) with 4000W (AC) output. Are these the two ratings to which your figures correspond?

That's right. It is matched to the panels in that sense - the recommended PV power range is 1300-2000Wp. Had I known then what I know now I probably would have done a lot of things differently.

WestonDave

Pretty good few days down here, averaged 24kWh for the last week with a high of 27.2 on the Friday. Not going to be as good today - might struggle on to 16.5 but its still above the predicted average for our system (4kWp split part SE part SW).

EDF have acknowledged the FiT application - lets see how long it takes them to actually process it!

EricMears

Kernel_Sanders wrote: »

Those two statements don't appear to tally, unless haze has increased.

Not sure why you want them to 'tally' ?

It was always a sunny day (as opposed to a 'grey day'). Even when clouds were obscuring direct view of sun there was plenty of blue sky visible nearby.

The 13Kwh at 3pm eventually worked up to 19.2 Kwh for the day. Generation curve vaguely resembled (with a lot of imagination) a normal distribution but with obvious large 'bites' out of it.

Day bore absolutely no resemblance to any of the forecasts I'd consulted.