National Grid ESO says its collaboration with the Met Office has improved solar forecasting, in turn sharpening the accuracy of national demand forecasts on the transmission system.
The project, funded under Ofgem’s Network Innovation Allowance (NIA) programme, began in 2016.
UK solar PV generation capacity stands at around 13GW, all connected to the distribution system, where National Grid has limited visibility. Swings in solar generation create significant effects on the operation of the transmission system, with National Grid creating programmes that incentivise increased consumption when demand dips in a bid to maintain system stability.
As such, accurately forecasting solar irradiation levels can have a significant impact on how the system operator manages to keep supply and demand in balance while maintaining frequency levels within set tolerances.
Moreover, National Grid has predicted significant growth in solar generation for decades to come. That means the challenge will only increase.
Getting meaner on error
The Met Office uses different models to provide NG ESO with solar forecasts, from hourly out to two weeks, but it’s difficult to get it right all the time, particularly as the forecasts get further out.
Solar forecasts use a metric called ‘mean absolute error’, based on the spread of forecasts around the true value. The NIA project team focused on four pieces of work to reduce error and bias within those forecasts.
“The first area we looked at was all about how we could develop models that improve our ability to forecast cloud, because this has such a significant effect on solar radiation levels,” said senior Met Office scientist Ian Pearman.
“Another work package looked at our forecasting in the very short term (out to a few hours), which is significant to ESO’s operations. This is what we term our ‘Nowcast’.
“A third element of the study looked at our statistical processing – in other words, could we refine how we use the data from our observation stations to remove any biases.
“Finally, we studied the potential to introduce a weighted blended forecast taken from all our different models rather than the current approach that takes a simple average of the solutions from one ensemble forecast model.”
The results were significant, according to National Grid ESO.
“Over the last financial year, we’ve seen improvements of between 5 and 9% for the in-day and day-ahead national demand forecasts. One of the reasons for this improvement was the successful collaboration with the Met Office and the implementation of the project’s work into our forecasting operations.”
NG ESO said the project will bring wider benefits – as better forecasts feed into multiple areas, not just in the energy industry, where it impacts buying and hedging strategies, but retail, manufacturing and aviation.
More detail here.