HelioClim-3 Similarity Forecast - Methodology
|Last update: Jul. 2017|
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The principle of the Solar Forecast Similarity Method algorithm is to search in the HelioClim-3 past irradiance database the closest period to the current day. The closest period is defined by considering the minimum of the square distance. Once the nearest period(s) is(are) determined, the following day(s) is(are) used as a prediction for the day following the current day.
This search for the most suited day could be very time consuming, and a lot of work has been done to reduce this time by a factor up to 50. Different parameters had been adjusted, and the best compromise is given by:
- a temporal window of 15 days before and after the date independently of the year
- a search in the previous 4 years is considered
- the code is searching for the 10 closest days
The days following the 10 selected days in the past are averaged to produce the prediction. With this configuration, the bias is null ; the algorithm outperforms the persistence by 20% and the error is similar to existing methods.