So now I have a solar PV system how do I make the most of it???

Equaliser123

Cardew wrote: »

That will surely depend on the inverter.

.

Good point. Does that mean that my 3.29kwp panels will never actually produce more than 3kw due to my inverter being a 3kw type?

The installers said that it would not be an issue if it ever went over its rating for a period of time.

zeupater

jackieblack wrote: »

So do you think those predicted figures might be correct after all?

Hi

For the first three months of your dataset the actuals are within 1.3% of the PVGIS prediction, and that's without knowing what inverter, panels, actual cable runs etc are ..... that's pretty good estimate in my opinion.

As for February, well it was a particularly dull month and the Met-Office anomalies map set describes how bad it's been over the country as a whole, so I wouldn't worry too much about your particular bad performance ..... next year could be as good as 2008 to make up for it (check ot the Feb 2008 sunshine anomaly !!).

It's all swings & roundabouts when considering single actual datasets v long term averages, but averaging a few years of your own production should provide a more stable correlation by smoothing out any major monthly anomalies such as we have experienced in February.

HTH
Z

zeupater

Equaliser123 wrote: »

Good point. Does that mean that my 3.29kwp panels will never actually produce more than 3kw due to my inverter being a 3kw type?

The installers said that it would not be an issue if it ever went over its rating for a period of time.

Hi

In the rare case where your panels produce 3.29kW DC, plus whatever their output tolerance is, your inverter (assuming 3000W AC max) will limit the output to 3.00kW AC by 'clipping' any excess.

Assuming that your panels are positive rated on nominal output tolerance, are brand new and therefore have not suffered any performance degradation, this will likely cost you a loss of around 22kWh per year with your setup (less than 1%) .....

HTH
Z

Cardew

Equaliser123 wrote: »

Good point. Does that mean that my 3.29kwp panels will never actually produce more than 3kw due to my inverter being a 3kw type?

The installers said that it would not be an issue if it ever went over its rating for a period of time.

It is important to appreciate just what kWp means in this context.

Panels are given a standard rating for producing their power output in standard laboratory conditions with controlled 'sunlight' density(watts per M2) and ambient temperature.

So your set of 3.29kWp panels would produce 3.29kW under those laboratory conditions. Those conditions exist roughly 35 degrees above and below the equater.

Move your panels to, say Greenland and they will not exceed, say 2kW on the brightest day. Move them to the Equator and you might get, say 5kW. (2kW and 5kW are just to illustrate the principle)

Depending where you live in UK will be a factor in the size of the inverter. There are also losses and the performance of panels deteriorates over the years.

So the choice of the size of the inverter is down to the judgement of the installer. Presumably they felt that a 3kW inverter would be the best compromise for your site and system.

However it is possible that the choice of a smaller inverter, was influenced by it being cheaper.

More technical detail on kWp here:

http://www.solar-facts-and-advice.com/kWp.html

jackieblack

zeupater wrote: »

Hi

For the first three months of your dataset the actuals are within 1.3% of the PVGIS prediction, and that's without knowing what inverter, panels, actual cable runs etc are ..... that's pretty good estimate in my opinion.

As for February, well it was a particularly dull month and the Met-Office anomalies map set describes how bad it's been over the country as a whole, so I wouldn't worry too much about your particular bad performance ..... next year could be as good as 2008 to make up for it (check ot the Feb 2008 sunshine anomaly !!).

It's all swings & roundabouts when considering single actual datasets v long term averages, but averaging a few years of your own production should provide a more stable correlation by smoothing out any major monthly anomalies such as we have experienced in February.

HTH
Z

Thanks zeupater, I wasn't sure that I'd put the info in correctly, but having looked at those met office maps maybe I did it ok after all!

Equaliser123

Cardew wrote: »

It is important to appreciate just what kWp means in this context.

Panels are given a standard rating for producing their power output in standard laboratory conditions with controlled 'sunlight' density(watts per M2) and ambient temperature.

So your set of 3.29kWp panels would produce 3.29kW under those laboratory conditions. Those conditions exist roughly 35 degrees above and below the equater.

Move your panels to, say Greenland and they will not exceed, say 2kW on the brightest day. Move them to the Equator and you might get, say 5kW. (2kW and 5kW are just to illustrate the principle)

Depending where you live in UK will be a factor in the size of the inverter. There are also losses and the performance of panels deteriorates over the years.

So the choice of the size of the inverter is down to the judgement of the installer. Presumably they felt that a 3kW inverter would be the best compromise for your site and system.

However it is possible that the choice of a smaller inverter, was influenced by it being cheaper.

More technical detail on kWp here:

http://www.solar-facts-and-advice.com/kWp.html

Thanks. I was told - several times - that the smaller inverters work better.

Appreciate the point that the rating is under lab conditions. A touch misleading though.

Equaliser123

Equaliser123 wrote: »

Thanks. I was told - several times - that the smaller inverters work better.

Appreciate the point that the rating is under lab conditions. A touch misleading though.

Hit the inverters limit today for 30 mins or so on and off. 3kw recorded on my SunnyBeam.

Now if I had a larger inverter, I wonder if I would have hit the 3.29kwp....

free_juice?

Where are you? There wasn't even two minutes of sunshine in the SE. My 3kW inverter logged 1139.05 at 1pm, next highest 761W and apart from that sub 500.

Equaliser123

free_juice? wrote: »

Where are you? There wasn't even two minutes of sunshine in the SE. My 3kW inverter logged 1139.05 at 1pm, next highest 761W and apart from that sub 500.

Ha! South Wales. I must confess, I was surprised.

Had a poor morning (only about 2kw/h produced up to midday) but as our panels our WSW facing, we tend to generate more later. 1400 - 3kw for 30 mins. Managed 9.5kw/h for the day.

To be fair, whilst a nice day, there have been other nice days where the generation is only 2.2-2.4kw. Today didn't seem especially bright although clearly the panels were happy!

Cardew

Crisp clear and sunny, without a cloud in the sky, here in the Midlands.

Standing by for 'highest of the year' reports after 6pm!!!!