Renewables: "talking 'bout my generation"

WestonDave

December figures of 102.7kWh compared to PVGIS classic estimate of 75 was a nice end to the year - albeit most of that was in the first half of the month. Decent enough day today at 8.3kWh so lets hope this year we get the sort of record breaking sun performance that the rainfall figures turned in in 2012! Happy new generating year all!

(4kWp system split half SE and half SW based in Bath)

The_Green_Hornet

I was wondering why some people, when comparing their actual generation, are still using the Classic (PVGIS-3) database when it is generally accepted that the Climate (PVGIS-SAF) database is the more accurate?

From the PVGIS website:

So which is more accurate?

The new CM-SAF data set has been tested extensively against high-quality measurements on the ground(see documentation at the CM-SAF site). Generally the overall error for the whole year is quite small. A list of ground stations and the yearly error (bias) is shown in the table below. In nearly all places the error is less than 5%. In many places the difference between PVGIS-3 and PVGIS-CMSAF are larger than that. For this reason we are convinced that in most places the new data set is an improvement.

PVGIS radiation databases

Wouldn't it be better if everyone compared their actual generation against the same predictive data set?

sly_dog_jonah

In our location the difference between the two PVGIS models is only 1.9%. Classic gives an annual estimate of 3200kWh while Climate-SAF gives a marginally higher 3260kWh. So in our location the difference between the two models is negligible.

The Mounting Position option selected has more affect on the estimated generation for our system at least, but the calculator only offers two options: building integrated (no airflow behind the panels) or free-standing (free airflow behind the panels). The vast majority of domestic PV installations are retro-fitted to roofs, so something between the two in terms of airflow. In our location and for our system, the two options yield a 4.8% difference in generation estimate. Since we have curved tiles I use the free-standing option as this is probably the more accurate of the two for our system.

KevinG

sly_dog_jonah wrote: »

In our location the difference between the two PVGIS models is only 1.9%. Classic gives an annual estimate of 3200kWh while Climate-SAF gives a marginally higher 3260kWh. So in our location the difference between the two models is negligible.

As you will see from my earlier post, the difference is large for me 1686 vs 1875. I generally achieve roughly the Climate-SAF figure.

WestonDave

@Greenhornet - fair point - will need to update my spreadsheet as I need to combine two sets of data. PVGIS Climate would predict 100.6 for December for me against 102.7 acheived. I suspect as the page defaults to classic most people don't think to change the setting as much as any decision to use one or the other (although it is always nice to think you are doing better than you should!).

Oscargrouch

WestonDave wrote: »

I suspect as the page defaults to classic most people don't think to change the setting as much as any decision to use one or the other (although it is always nice to think you are doing better than you should!).

Think you need to change that to:- (although it is always nice to think you are doing better than you might)! They can't predict the weather yet, never mind the hours of sunshine. :rotfl:

Today 9.43396% of yesterday. Oooopps misled you there, it was 9.0909%

WestonDave

Hmm a 0.5 day - still on the bright side the mild weather is keeping the gas consumption down!

tunnel

As a matter of interest, does anyone have a clue what the next increase is for the FIT,aren't we due an increase in april? Had it in my head it tracks inflation of some sort up to december. Anyone?

Tunnel

Edit:- just checked and the rpi is only available for november,currently 3%

Oscargrouch

tunnel wrote: »

As a matter of interest, does anyone have a clue what the next increase is for the FIT,aren't we due an increase in april? Had it in my head it tracks inflation of some sort up to december. Anyone?

Tunnel

Edit:- just checked and the rpi is only available for november,currently 3%

I will follow the average rail fare increase.:) (4.2%) that will do:rotfl:

tunnel

Oscargrouch wrote: »

I will follow the average rail fare increase.:) (4.2%) that will do:rotfl:

That would be nice,just a little bit less than we had last year(4.8%). If the yanks had gone over their "fiscal cliff" then from what i'd read,i'd have liked to have followed their milk price....it was expected to DOUBLE 100%

We'd all be then :j

Tunnel