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

Cardew

jackieblack wrote: »

Don't have monthly prediction figures to work out a %, but my 2.22kWp system produced 50kWh in Dec, 65 in Jan and 71 in Feb

I think those figures put the savings for using more electricity in the house(not the FIT) into perspective.

In 3 months it has generated 186kWh. So the difference in savings between someone who used 50% in the house and someone who managed to use 60% would be less than £2 for the whole period of 3 months.

jackieblack

Cardew wrote: »

I think those figures put the savings for using more electricity in the house(not the FIT) into perspective.

In 3 months it has generated 186kWh. So the difference in savings between someone who used 50% in the house and someone who managed to use 60% would be less than £2 for the whole period of 3 months.

I agree, savings on electricity bill are a bonus, but financially they are not enough to justify the initial outlay.

Although during periods of low generation the majority of what is generated will be used in the house, will it not?

eg our elec bill in January, on the day the (import) meter was read the pv system had generated 153 kWh. Comparing that bill with the bill for the same quarter last year, we have imported 156kWh less.

Not especially scientific I know, but seems to indicate that we are probably using almost 100% of whatever is being generated ourselves at the moment?

free_juice?

If you have an old meter that goes backwards when exporting you can get a pretty good idea of what percentage is being used in-house. In my case unless the sun is out reasonably strongly I am always using 100% myself.

25 days in January generated 59.32 kWh and February scored 95.52. I have never seen such a protracted period of filthy weather. (3.29kW system unshaded due south).

dobbers

Does anyone know how to calculate the expected output from a system per month? I can use the calculators on the Encraft website to get an idea of the total solar energy available at my postcode per month but then if I have a 3.04kWp setup based on 20 square meters of panels working at 15% efficiency how does that convert into expected values per month?

Eg: For my postcode the Encraft calculations yield:

Jan 19.53
Feb 36.68
Mar 71.92
Apr 105.90
May 144.77
Jun 141.90
Jul 143.22
Aug 121.52
Sep 81.60
Oct 48.67
Nov 23.10
Dec 14.57

This equates to a total of 953.38 kWh per square meter per year.

So for Jan is it 19.53 x 20 = 390.60 Kwh for total array but it is only 15% efficient so will get roughly 390.60 x 0.15 = 58.59 kWh for whole month or 58.59 / 31 = 1.89 Kwh per day in Jan?

regards,

Dobbers

zeupater

dobbers wrote: »

Does anyone know how to calculate the expected output from a system per month? I can use the calculators on the Encraft website to get an idea of the total solar energy available at my postcode per month but then if I have a 3.04kWp setup based on 20 square meters of panels working at 15% efficiency how does that convert into expected values per month?

Eg: For my postcode the Encraft calculations yield:

Jan 19.53
Feb 36.68
Mar 71.92
Apr 105.90
May 144.77
Jun 141.90
Jul 143.22
Aug 121.52
Sep 81.60
Oct 48.67
Nov 23.10
Dec 14.57

This equates to a total of 953.38 kWh per square meter per year.

So for Jan is it 19.53 x 20 = 390.60 Kwh for total array but it is only 15% efficient so will get roughly 390.60 x 0.15 = 58.59 kWh for whole month or 58.59 / 31 = 1.89 Kwh per day in Jan?

regards,

Dobbers

Hi

Probably better to use PVGIS-4 available here ..... http://re.jrc.ec.europa.eu/pvgis/apps4/pvest.php ..... and select the "CLIMATE-SAF PVGIS" dataset as it's more accurate for specific locations.

It will do the hard work regarding efficiencies etc for you and if you select the 'Show Graphs' & 'Show Horizon' options it will give some interesting charts too.

HTH
Z

Cardew

Most specification sheets for PV systems give the estimated output in kWh per kWp. This varies between 700kWh/kWp to, say 1,000kWh/kWp - the latter figure would be an optimally sited system in Southern UK.

Your set of figures seem like that sort of spec sheet and of course it works out to roughly the same results you get from from your calculations i.e. 19.53 x 3.04 = 59.37KWh for Jan.

P.S I assume you live down South?

dobbers

Many thanks that was just what I was after. Allows us to check that the suppliers are being accurate.

Dobbers

dobbers

Cardew: No I am based in Wetherby in Yorkshire.

regards,

Dobbers

dobbers

I saw the SMA Sunny Beam demonstrated at a supplier today and the question I had that they could not answer was regarding the historical data it displays in graph format. I was told you can download a whole bunch of data from this device via plugging it in to your computer via the USB port on a PC.

What data can you extract from the SMA Sunny Beam using this method? If say I was away on holiday for a week, when I get back could I look up the exact amount generated in kWh each day that I was away for instance in a numerical format rather than trying to judge what the bar graphs are telling me?

regards,

Dobbers

free_juice?

Page 69 of the manual may help.

http://download.sma.de/smaprosa/dateien/8584/BeamBT-BEN094911.pdf

My SMA webbox allows the facility, a 15 minute log until you fill up your XD card and accessible via the web from anywhere. You could read mine if I told you the password. :cool: