Suchergebnisse

An exhaustive evaluation of the performance of decomposition models to estimate direct and diffuse components from the global horizontal solar irradiance has been carried out in this work. The main objective of this work has been to compare the model performance for two different time bases, hourly and monthly average hourly bases. An extensive database of horizontal solar irradiance from nine locations in Spain was used for the study. The data span through January 1980 to December 2012 of hourly solar irradiance for the nine locations and thus indicate a cumulative year sum of 132 years. This study first investigated the decomposition of the hourly horizontal irradiance into hourly direct and diffuse components using six decomposition models widely referenced in the bibliography. In the hourly decomposition investigation, it was observed that there are no significant differences between the six models for each specific location. Nevertheless, the performance of each of the models was strongly dependent on cloudiness conditions and the solar altitude at the location which is associated with the climatic condition of each site. Further investigations using the six decomposition models were conducted to estimate monthly average hourly values of direct and diffuse components of the solar irradiance with proper assessment of the different models' performance at various locations. Based on the results of the investigations which present no significant differences in the performance of the different models, an extremely simple algorithm was developed to estimate monthly average hourly values of direct and diffuse solar irradiance, which reduces the statistical errors in all locations investigated. ; Spanish Government (ENE2014-54601R) and the 506 Regional Government of Castile and Leon (BU358A12-2)

Direct solar irradiance has to be determined for the design of many energy applications such as photovoltaic systems and concentration systems, and the generation of solar potential maps for energy use. Knowledge of the accurate values of radiation components in a local area will allow optimal sizing of solar energy conversion systems. The estimated values of direct solar irradiance from models are still necessary at those sites where no measurements are available. In this work, different models used for the estimation of the direct component of solar irradiance are analyzed. First, an evaluation of the performance of eight existing original models was performed from which three were selected. Second, the selected models were calibrated to adapt them to our studied geographical area, which is the important aspect of this work, and an assessment of performance improvements for locally adapted models is reported. Experimental data consisted of hourly horizontal global, direct, and diffuse solar irradiance values, provided by the National Meteorological Agency in Spain (AEMET) for Madrid. Long-term data series, corresponding to a total period of time of 32 years (1980–2011), have been used in this study. Only clear sky models were treated at present. The three selected models were adapted to the specific location of Madrid, and root mean square error (RMSE) and mean-biased error were determined. By comparing the performance in the direct horizontal irradiance estimation from existing original and the corresponding locally adapted models, it is found that the values of RMSE decreased from 9.9% to 5.7% for the Louche model, from 7.8% to 7.4% for the Robledo-Soler model, and finally from 8.8% to 6.7% for the European Solar Radiation Atlas model. Thus, significant improvements can be reached when parametric models are locally adapted. In our case, it is up to approximately 4% for the Louche model. It is expected that calibrated algorithms presented in this work will be applicable to regions of similar climatic characteristics. ; Spanish Government (grant ENE2011-27511) and the Department of Culture and Education of the Regional Government of Castilla y León, Spain (grant BU358A12-2)

Four spatial interpolation methods (Inverse Distance Weighted, Spline, Kriging and Natural Neighbor) and their different variations are employed to map Global Horizontal Irradiation (GHI) in Castilla-León, Spain. The work has been performed using the software ArcGis, widely used in geostatistical applications, showing the versatility of the system and its applicability to climate data. The measuring network consists of 71 ground meteorological stations that use seven complete years of half-hourly data sets, yielding annual daily averages of GHI. The interpolation results are tested against data from the four Spanish National Meteorological Agency (AEMET) stations available in the region using standard statistical indicators (RMSE, MBE, MAPE and MAE). An additional partial cross validation of the results, which excludes five stations from the measuring network, employs different criteria to verify the results of the interpolation methods applied. This work contributes to the classification of interpolation methods to obtain climatological data across large areas with a low number of irregularly distributed of measurement points and with a low topographic complexity. The Universal Kriging method with quadratic semi-variogram shows the best results taking into account the RMSE and MAE statistical indicators ; Spanish Government (Grant ENE2014-54601-R) and Junta de Castilla- León (BU034U16). One of the authors, David González Peña, thanks to Junta de Castilla-León and European Social Fund (Orden EDU/310/2015) for financial support.