Renewables: "talking 'bout my generation"

Kernel_Sanders

19.75 kWh on Friday.

KevinG wrote: »

That would be great, but you may find the difference between April/May and June/July is less than you expect. My generation seems to peak between late April and late May. Summer brings longer periods of good generation but the higher temperatures knock it back.

Also, in that latter pair of months, the Sun is spending much more time in the NE and NW, therefore offsetting much of the longer production period. Do you have a steep pitch?

Dodo0808 wrote: »

Sweet jeez....what shiney corner of the country are you all in:o

Only 9.2kWh for me today.

North Notts, actually...think I topped 13 kWh on Thursday (from 3.92 kWp).

jimjames

KevinG wrote: »

It's the panels rather than the inverter that are the issue - output drops as temperature rises.

I did an experiment the first year we had them. Hosed them down on a baking sunny day to see what effect it had. Looked to add about 300W to the output from what I remember. I think the official numbers are 0.5% drop for each degree of temperature rise.

shavy65

jimjames wrote: »

I did an experiment the first year we had them. Hosed them down on a baking sunny day to see what effect it had. Looked to add about 300W to the output from what I remember. I think the official numbers are 0.5% drop for each degree of temperature rise.

Was that a 300W power hose?

Oscargrouch

EricMears wrote: »

If I divide 28.777 by 6.5, I seem to make it 4.427


If the alleged purpose of these 'O' units is to enable comparisons, shouldn't there be some consistent approach to calculating them ?

You are of course, correct. Just goes to show how incorrect working out the average over three figures can be........:D

EricMears

Oscargrouch wrote: »

You are of course, correct. Just goes to show how incorrect working out the average over three figures can be........

The concept of averaging three unrelated numbers is fundamentally flawed ! You could only justify trying if all three were from identically rated sets of panels; otherwise, you'd need to apply a weighted average (which would get the same result as adding the individual outputs up and dividing by three but is more complicated to work out).


But for a clear demonstration of how useless the 'O' is as a comparator between different installations, just look at the three sets of Os for the same day in the same place (as least I assume all three sets are within a few yards of one another - I guess it's just possible that one set is half a mile away in a far corner of the Grouch Estate ?).


ESE 9.928kWh (5.06 O's)
SSW 10.68kWh (5.23 O's)
WNW 8.169kWh (3.26 O's)


If two adjacent installations (enjoying identical weather conditions) can produce 3.26 & 5.23 Os on the same day, which of those would be the one that you'd propose for comparing with another installation in a different county ?


Given that often as not these Os are trundled out without any attempt to specify latitude, longitude, elevation, ambient temperature, panel angles or any of the other factors that affect generation, how might one adjust them to give a meaningful comparison with one's own installation ?

jimmyboy420

They face different directions, so some are going to be more productivr than others, on any given day.

Os reflect this relative production perfectly.

shavy65

Wow these O`s really rile some people
I wonder in what simple way these doom-gloomers would compare totally different systems?
It`s a simple way for us simple people to compare generation.
Leave the simpletons alone.

KevinG

Kernel_Sanders wrote: »

Also, in that latter pair of months, the Sun is spending much more time in the NE and NW, therefore offsetting much of the longer production period. Do you have a steep pitch?

About 37 degrees, not particularly.

EricMears

shavy65 wrote: »

Wow these O`s really rile some people
I wonder in what simple way these doom-gloomers would compare totally different systems?
It`s a simple way for us simple people to compare generation.
Leave the simpletons alone.

They don't 'rile' me - I just hate the way that people here think that they might help to compare different systems when (as demonstrated above) they don't.


Autosig for shavy65 (and indeed my own) gives the main pieces of data required for anyone to adjust raw kWh to their own situation. Majority of others appear to think that reporting an 'O' value would do the same - but it doesn't.


And to answer the question, you'd need to use the information given to calculate expected daily generation from the pvgis webpage then work out what percentage of that has actually been achieved. If you do that for two different installations, it will become obvious that (say) 103% is better than 96%.

Martyn1981

EricMears wrote: »

But for a clear demonstration of how useless the 'O' is as a comparator between different installations, just look at the three sets of Os for the same day in the same place (as least I assume all three sets are within a few yards of one another - I guess it's just possible that one set is half a mile away in a far corner of the Grouch Estate ?).

ESE 9.928kWh (5.06 O's)
SSW 10.68kWh (5.23 O's)
WNW 8.169kWh (3.26 O's)

If two adjacent installations (enjoying identical weather conditions) can produce 3.26 & 5.23 Os on the same day, which of those would be the one that you'd propose for comparing with another installation in a different county ?

Eric, why are you having so much trouble with the concept of kWh/kWp (shortened on here to an 'O' for Oscar).

Those 3 numbers ARE the comparison, we can clearly see how the 3 systems did in comparison to each other, the ratio is 5.06:5.23:3.26.

That's it, there's nothing more to be done - there is your comparison. Now the reasons for the difference may be many, orientation, pitch, weather changes through the day, panels, inverters etc etc. But all of those things are what makes the generation figure, that is then standardised (to a single kWp) for comparison purposes.

It really is as easy as that. What you've described as an example proving it's uesless is actually the complete opposite, Tunnel can instantly compare the relative performances of his systems.

If you don't like kWh/kWp (O) then don't use it, what's the problem, nobody is forcing anyone, it's all supposed to be a bit of fun, but for some reason the anti-O's keep moaning!

Mart.