Solar radiation forecasting with non lineal statistical techniques and qualitative predictions from spanish national weather service
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1) The study uses neural network models to predict half-daily solar radiation values in Spain, aiming to improve predictions for solar energy feed-in tariffs. 2) The best neural network model reduced the mean root squared error of predictions compared to a persistence model by over 9%. 3) While the first neural network model had errors limited by nonlinear signal behavior, a second model further improved predictions, achieving the best error level possible with the presented methodology.
Solar radiation forecasting with non lineal statistical techniques and qualitative predictions from spanish national weather service
- 1. Solar radiation forecasting with non-lineal statistical techniques and 20 08 UN 008 qualitative predictions from Spanish National Weather Service OS r 2 EUR be to BON Oc IS Martín L., Zarzalejo L.F., Polo J., Navarro A., Marchante R. L 1. INTRODUCTION 3. RESULTS Solar energy feed-in tariff is regulated by (RD 436/2004, Errors of the models essayed are measured in terms of 661/2007) in Spain. Predictions must be given for next 72 mean root mean squared deviation (RMSD). The best hours and deviations are strongly penalized. A new method NN(z) model is compared to persistence model (PER) in to predict half daily values of solar radiation is presented. terms of improvement of RMDS. 2. METHODOLOGY 1 N 45.0 ° N ∑ ( xi − xi ) 2 RMSD = ˆ 42.5 ° N Solar radiation is transformed to a new gaussian and N i=1 40.0 ° N • Madrid RRN AEMet stationary variable. “Lost component” (LC) is the difference i − ierrorm 37.5 ° N betwen extratrrestrial and ground measured solar radiation. improvement = 1 − ÷ i − ierror ÷ 35.0 ° N ° 15.0 ° W12 ° ° 0.0 E .5 W10.0 ° W ° E 5.0 ° E 7.5 E 1 p 7.5 ° W 5.0 ° W 2.5 ° W 0.0 ° 2.5 6000 38 5000 Lost Component L 36 NN(1) 4000 C NN(2) 34 Halfday) NN(3) P NN(4) 3000 R NN(5) 32 2 E NN(6) 2000 D NN(7) % RM SE Prediction G (W /m I 30 NN(8) C NN(9) T NN(10) 1000 28 P ersistence I O 0 0 N 26 100 200 300 400 500 600 700 S Half Day 24 Synoptic predictions of sky conditions (SYN) are used as 22 1 2 3 4 5 6 input to the neual network to test the improvement of the 40 Pre diction horizon (Halfdaily ) predictions. AEMET offers this predicitons in its web page W I for each location of Spain and 7 days in adavance. T 35 H NN(1) Halfday) NN(2) 30 NN(3) S NN(4) Y 2 NN(5) %RMSE Prediction G (W/m N 25 NN(6) NN(7) C 20 NN(8) NN(9) O NN(10) N Persistence D 15 I T 10 I O N 5 S 1 2 3 4 5 6 Prediction horizon (Halfdaily) 4. CONCLUSIONS The error of the first model is limited by an upper level which is due to deterministic nonlinear behaviour of the signal which can’t be followed correctly by neural network models. The second model improves Neural Network (NN) is used to predict future values from considerably the prediction. The error has a lower level observations. NN(z) índica el tamaño del vector patrón de of nine percent which is the best prediction error that can entrada empleado z=1…10. be achieved with the methology presented. División de Energías Renovables (Departamento de Energía), CIEMAT, Av. Complutense nº22, Madrid, 28040, (Madrid) España, +34 913466048, luis.martin@ciemat.es