Assumptions need to be made, so here they are!
The output from each station isn't directly available, so it is inferred from the Ofgem reports of certificates issued.
Ofgem manage several schemes for wind producers.
After collecting details of the certificates issued for each station the site calculates the output for that station. This is normally done using the REGO certificates, but if these are not available then the RO or FIT figures will be used.
Where the issued certificates do not relate 1:1 with generation the Ofgem data contains the factor to be used for calculating the output.
The potential output is calculated as
Days in month x 24 hours x Stated Station Capacity
e.g. for a station with a stated 80kW instant capacity, in a 30 day month this would be calculated as
30 x 24 hours x 80/1000 = 57.6MWh
nb On the site these may be shown as rounded to the nearest whole number, but in calculations the full precision is used.
While I am well aware that no station will ever be able to operate 100% of the time, but without information on when the maintenance is being performed it's impossible to adjust the monthly figures and using the above provides a level playing field for all stations.
As the data is based on that provided by Ofgem, if the data is not available from their website it won't be displayed on this site. There are many stations with incomplete data but without more information it's impossible to state why.
Often the stated capacity of a station will appear to be different from the advertised information for the installed turbines.
A good example is where an Endurance E-3120 is installed. This has a stated capacity of 50kW, but is normally listed as 80kW with Ofgem. The difference is normally to allow for wind speeds faster than those used to rate the turbine. Smaller turbines usually have a less complex governor and so at wind speeds above those used to rate the turbine will generate more power.
The industrial scale turbines do not suffer from this issue as they are more complex and are rated in different ways.