Renewables: "talking 'bout my generation"

EricMears

Kernel_Sanders wrote: »

I've been looking back over this thread at what I've been missing in my absence and discovered the source of the 'O':In tribute to Oscargrouch??:shocked: A whole year previously on this very thread I was proposing virtually the same concept....

The concept was flawed then and the 'O' is still irrelevant.

The crude ratio completely ignores location, slope of the roof and the angle at which it points.

To take a very crude example, a 1 kW panel pointing due South at 30 deg might well generate 8kWh on a good day this week. Move it onto a N facing roof with a slope of 60 deg and you'd be lucky to see half that. Obviously in real life nobody would ever choose the second option but there must be thousands of SP installations where the roof doesn't face due South and the inclination isn't the optimum value. (indeed, for any fixed installation it would only at best be at the optimum angle on two days per year)

Oscargrouch

EricMears wrote: »

The concept was flawed then and the 'O' is still irrelevant.

The crude ratio completely ignores location, slope of the roof and the angle at which it points.

As does the kWh result....so are you suggesting that the whole thread be abandoned, as all results posted do not take into account 'location, slope of the roof and the angle at which it points' ? Apart from the kWp result which does of course, take into account at least sytem size......:rotfl:

EricMears

Oscargrouch wrote: »

As does the kWh result....so are you suggesting that the whole thread be abandoned, as all results posted do not take into account 'location, slope of the roof and the angle at which it points' ? Apart from the kWp result which does of course, take into account at least sytem size......

No, it's still useful to know that A has had his best ever day or B his worst. But comparing A's results with B's is pointless unless you know all the variables.

shafeeq

Oscargrouch wrote: »

you suggesting that the whole thread be abandoned, as all results posted do not take into account 'location, slope of the roof and the angle at which it points' ? Apart from the kWp result which does of course, take into account at least sytem size......:rotfl:

YES cause my figures are always low :mad: it will make be feel happier :rotfl:

Martyn1981

EricMears wrote: »

The concept was flawed then and the 'O' is still irrelevant.

The crude ratio completely ignores location, slope of the roof and the angle at which it points.

I don't understand why you keep complaining about this. I appreciate that there are lots of factors to consider if you were trying to compare two systems and account for all differences BUT the very, very, very (imagine a lot more verys) first thing you'll need to do in any comparison is equalise the size. This would be done by dividing by the kWp of the system, thereby effectively comparing systems as if they are all 1kWp.

My system is quite big, but also off-south, by presenting my generation in O's I'll usually do worse than most others, unless there was a large discrepancy in the weather.

So O's might be a little crude, but they are the first port of call when comparing generation. Unless you can honestly state that you would consider another factor more important than size?

I would suggest the order of importance would be, size, orientation, location, pitch. Weather is also very important, but depends on size of sampling period.

So, yes I agree it's a crude measure, but it's certainly not flawed or irrelevant, it's step one and both accurate and relevant, but the comparison data needs expanding if you want greater accuracy.

Mart.

EricMears

Martyn1981 wrote: »

I don't understand why you keep complaining about this. I appreciate that there are lots of factors to consider if you were trying to compare two systems and account for all differences BUT the very, very, very (imagine a lot more verys) first thing you'll need to do in any comparison is equalise the size. This would be done by dividing by the kWp of the system, thereby effectively comparing systems as if they are all 1kWp.

My system is quite big, but also off-south, by presenting my generation in O's I'll usually do worse than most others, unless there was a large discrepancy in the weather.

So O's might be a little crude, but they are the first port of call when comparing generation. Unless you can honestly state that you would consider another factor more important than size?

I would suggest the order of importance would be, size, orientation, location, pitch. Weather is also very important, but depends on size of sampling period.

So, yes I agree it's a crude measure, but it's certainly not flawed or irrelevant, it's step one and both accurate and relevant, but the comparison data needs expanding if you want greater accuracy.

Mart.

I don't think I'm complaining about it - feel free to quote in whatever silly units you like in addition to the basic information of daily generation in real units, size of installation, direction of roof, slope, location (and it's amazing how few of us include the additional info !).

Just don't expect me to join in.

Oscargrouch

EricMears wrote: »

I don't think I'm complaining about it - feel free to quote in whatever silly units you like in addition to the basic information of daily generation in real units, size of installation, direction of roof, slope, location (and it's amazing how few of us include the additional info !).

Just don't expect me to join in.

I look forward to your 'once a year post' on how your system did in comparison to the previous year....:rotfl:

Bye the way; weather forecasts can vary within 1/2 a mile......so unless you are going to sit there for a few hours waiting for your Lat Long to come up; you will have to 'grin and bear it'.

zeupater

Hi All

I'd propose that the only relevant comparative measure between systems, if this is the requirement, is to quote %age achieved against individual system PVGIS target, this is the only way that orientation, roof angles and location can be accounted for.

Of course, the version of PVGIS and the associated losses would need to be standardised and it would need to be recognised that any change to the database would need everyone to adopt rebased targets in order to standardise comparisons for new members, but .....

.... then again, I'll just keep spot-checking MPPT1 DC generation against MPPT2 to see if the panels are all working and then see how our weekly/monthly averages compare to target and some very local systems, even though we automatically collect masses of data. The reason for this, well, whether the system is performing well or disappointingly, if it's working properly it's where it is and pointing the way that it does, so seeing that I can't do anything about the weather, why worry ? .... :cool:

HTH
Z

EricMears

zeupater wrote: »

I'd propose that the only relevant comparative measure between systems, if this is the requirement, is to quote %age achieved against individual system PVGIS target, this is the only way that orientation, roof angles and location can be accounted for.

Indeed. And I've done just that for several recent months. A month being just about long enough to iron out short term 'bad days'.

Quite happy to call that the 'Z measurement'

jimjames

EricMears wrote: »

No, it's still useful to know that A has had his best ever day or B his worst. But comparing A's results with B's is pointless unless you know all the variables.

ALL the variables would also include temperature and sun/cloud cover so it gets pretty impossible to compare.

I think the concept is useful as it does allow comparison between sites even taking into account the restrictions.