Now we have completed a full year of operation we can start to check our performance against our predictions.
According to data published by the government here, wind speeds across the UK were about 5% below the average across the last 10 years (it has been a very calm summer as you can see from the graph below)
Our output from 1st Sept 2017 to 31st August 2018 was 1,914,334 kWh, which is about 12% below our projected output in an average year.
Energy output from a wind turbine is not proportional to wind speed – halving the wind speed reduces the energy in the wind to one eighth of the amount. We can see the effect of a reduced wind speed on energy yield from the turbine using the computer model on the EWT website here. This indicates that a 5% lower wind speed results in output falling by about 11%, which very nearly matches our measured output.
All this suggests our original projections for the long term performance of the turbine should be very close.
The graph below shows our output month by month from commissioning to now, and shows the effect of the very calm summer months.