Inter national J our nal of Electrical and Computer Engineering (IJECE) V ol. 8, No. 1, February 2018, pp. 497 504 ISSN: 2088-8708 497       I ns t it u t e  o f  A d v a nce d  Eng ine e r i ng  a nd  S cie nce   w     w     w       i                       l       c       m     Solar Photo v oltaic P o wer F or ecasting in J ordan using Artificial Neural Netw orks Mohammad H. Alomari 1 , J ehad Adeeb 2 , and Ola Y ounis 3 1 Electrical Engineering Department, Applied Science Pri v ate Uni v ersity , Amman, Jordan 2 Rene w able Ener gy Center , Applied Science Pri v ate Uni v ersity , Amman, Jordan 3 School of Electrical Engineering, Electronics and Computer Science, Uni v ersity of Li v erpool, United Kingdom Article Inf o Article history: Recei v ed: Jul 21, 2017 Re vised: No v 8, 2017 Accepted: Dec 3, 2017 K eyw ord: Solar photo v oltaic solar irradiance PV po wer forecasting machine learning artificial neural netw orks ABSTRA CT In this paper , Artificial Neural Netw orks (ANNs) are used to study the correlations between solar irradiance and solar photo v oltaic (PV) output po wer which can be used for the de- v elopment of a real-time prediction model to predict the ne xt day produced po wer . Solar irradiance records were measured by ASU weather station located on the campus of Ap- plied Science Pri v ate Uni v ersity (ASU), Amman, Jordan and the solar PV po wer outputs were e xtracted from the installed 264KWp po wer plant at the uni v ersity . Intensi v e training e xperiments were carried out on 19249 records of data to find the optimum NN configura- tions and the testing results sho w e xcellent o v erall performance in the prediction of ne xt 24 hours output po wer in KW reaching a Root Mean Square Error (RMSE) v alue of 0.0721. This research sho ws that machine learning algorithms hold some promise for the predic- tion of po wer production based on v arious weather conditions and measures which help in the management of ener gy flo ws and the optimisation of inte grating PV plant s into po wer systems. Copyright c 2018 Institute of Advanced Engineering and Science . All rights r eserved. Corresponding A uthor: Mohammad H. Alomari Electrical Engineering Department Applied Science Pri v ate Uni v ersity 166 Amman 11931 Jordan +962 560 9999 Ext 1165 m alomari@asu.edu.jo 1. INTR ODUCTION The importance of solar Photo v oltaic (PV) systems is increasing with the ongoing industrial gro wth and the increased ener gy demand for de v eloped and de v eloping countries [1, 2]. Ener gy production by PV systems is becoming one of the mai n rene w able ener gy sources as it turns the po wer of the sun into electricity and this can be done repeatedly without causing an y damage to the en vironment. The term “Photo v oltaic” is first used in English since 1849 as the process of light con v ersion into electricity [3]. Solar PV po wer plants are installed in tw o modes: grid-connected and a stand-alone (Of f-Grid) [4]. Of f-Grid systems are used for isolated or remote areas that are normally on smaller scale. On the other hand, grid-connected systems are widely operat ed and the y are pro v en to be hugely beneficial b ut the y were kno wn as uncertain systems, uncontrollable, and non-scheduling po wer source [5]. This is because such type of po wer production depends on the v ariable weather conditions according to the geographical area of the system. T o maintain a stable po wer quality and scheduling and impro v e in v estment feasabi lity , man y studies were reported in the literature suggesting dif ferent modeling, simulation, and prediction methods for the e xpected po wer production of solar PV plants [6, 7]. In [8], the accurac y of one-day ahead predi ction for the po wer produced by 1MW PV System is compared for tw o methods, Support V ector Machines (SVM) and M ultilayer Perceptron (MP) Artificial Neural Netw orks (ANNs). It w as found that the tw o algorithms approximately obtained almost the same accurac y with 0.07 KWh/m 2 and 0.11 KWh/m 2 Mean Absolute Error (MAE) and Root Mean Square Error (RMSE), respecti v ely . V arious forecasting methods of PV po wer output were re vie wed in [9]. It w as demonstrated that an y model J ournal Homepage: http://iaescor e .com/journals/inde x.php/IJECE       I ns t it u t e  o f  A d v a nce d  Eng ine e r i ng  a nd  S cie nce   w     w     w       i                       l       c       m     DOI:  10.11591/ijece.v8i1.pp497-504 Evaluation Warning : The document was created with Spire.PDF for Python.
498 ISSN: 2088-8708 uses numerically predicted weather data will not tak e into account the ef fect of cloud co v er and cloud formation when initializing, therefore sk y imaging and satellite data methods used to predict the PV po wer output with higher accurac y . The article also outlined some k e y f actors af fecting the accurac y of prediction, such as forecast horizon, forecasting interv al width, system size and PV panels mounting method (fix ed or tracking). The aim of the w ork published in [10] w as to study the ef fect of forecast horizon on the accurac y of the method used to predict the PV po wer production, which w as Support V ector Re gression (SVR) using numerically predicted weather data. T w o forecast horizons studied: up to 2 and 25 hours ahead. As e xp e cted, the forecasting of up to 2 hours ahead w as more accurate with RMSE and MAE increased 13% and 17%, respecti v ely , when the forecast horizon w as up to 25 hours ahead. The authors of [11] de v eloped and v alidated a model that adapted an ANN with tapped delay lines and b uilt for one day ahead forecasting. The inputs were the irradiation and the sampling hours. The model achie v ed seasonal MAE ranging from 12.2% to 26% in spring and autumn, respecti v ely . The research w ork of [12] compared tw o short-term forecasting models: the analytical PV po wer forecasting model (APVF) and the MP PV forecasting model (MPVF), with both of the models using numerically predicted weather data and past hourly v al u e s for PV electric po wer production. The tw o models achie v ed similar results (RMSE v arying between 11.95% and 12.10%) with forecast horizons co v ering all daylight hours of one day ahead, thus the models demonstrated their applicability for PV electric po wer prediction. A ne w Ph ysical Hybrid ANN (PHANN) method w as proposed in [13] to impro v e the accurac y of the standard ANN method. The h ybrid method is based on ANN and clear sk y curv es for a PV plant. The PHANN method reduced the Normalized MAE (NMAE) and the W eighted MAE (WMAE) by almost 50% in man y days compared to the standard ANN method. In [14], the PV ener gy production for the ne xt day with 15-minutes interv als w as accurately predicted with a SVM model that uses historical data for solar irradi ance, ambient temperature and past ener gy production. The method demonstrated v ery good accurac y with R 2 correlation coef ficients of more than 90%, and the coef ficient w as strongly dependent on the quality of the weather forecast. A model using multilayer perceptron-based ANN w as proposed in [5] for one day ahead forecasting. The daily solar po wer output and atmospheri c temperature for 70 days used for training the ANN. F or the dif ferent settings of the ANN model (number of hidden layers, acti v ation function and learning rule), the minimum MAPE achie v ed w as 0.855%. In this research w ork, ANNs were optimized to find the best learning configurations and map the a v ailable solar irradiance records into the generated solar PV po wer . The proposed system pro vides real-time ne xt-day predic- tions for the output po wer based on the kno wledge e xtracted from the a v ailable historical data. These predictions can be used by man y ener gy management systems [15] and po wer control systems of grid-tied PV plants [16]. 2. PV SYSTEMS AND D A T A The data used in this research were collected from the e xisting weather stat ion and solar PV plants at Applied Science Pri v ate Uni v ersity (ASU) as depicted in the map of Figure 1. Figure 1. A map sho wing part of ASU’ s campus. There are four separate PV systems installed at the uni v ersity campus for a total generation capacity of IJECE V ol. 8, No. 1, February 2018: 497 504 Evaluation Warning : The document was created with Spire.PDF for Python.
IJECE ISSN: 2088-8708 499 550KWp: three rooftop mounted solar systems and one ground mounted test field. In this w ork, the po wer production data e xtracted from the PV system ASU09 (F aculty of Engineering) [17] is correlated with the solar irradiance mea- sured for the same period by the weather station [18] which is located about 175m from the engineering b uilding (see Figure 1). 2.1. PV ASU09: F aculty of Engineering The lar gest PV system is installed on top of the f aculty of engineering b uilding with a capacity of 264KWp. It consists of 14 SMA sunn y tripo wer in v erters (17KW and 10KW) connected with Y ingli Solar (YL 245P-29b-PC) panels that are tilted by 11and oriented 36(S to E). The dataset used in this research w as created using all reported solar irradiance and PV po wer records between 15 May 2015 and 30 September 2017. This consists of 19800 PV po wer and 20808 weather station records with one hour frequenc y . 3. THE PR OPOSED PREDICTION SYSTEM 3.1. Pr epr ocessing As sho wn in Figure 2, the first stage of our system is to mak e sure that all data entries are consistent and a v ailable for both solar irradiance and PV po wer per instance of time. Figure 2. A block diagram for the proposed system. A filter w as designed to remo v e out an y irradiance record where no P V po wer v alue is reported at the same time. In addition, man y records were not reported correctly because of some netw ork connection disruptions and in some cases this w as caused by an in v erter f ailure. An irradiance record is associated with a solar PV output po wer v alue at each hour for a total of 19249 samples as depicted in Figure 3. As sho wn in Figure 2, the dataset is then normalized between 0 and 1 for a better machine learning performance. 3.2. Artificial Neural Netw orks ANNs is a m achine learning algorithm that interconnects non-linear elements through adjustable weights. The structure of ANN consists of three layers: input, hidden, and output layers as illustrated in Figure 4 [19]. The input layer recei v es the ra w data, and then these inputs are processed in the hidden layer to be finally sent as computed information from the output layer [5]. Using neural netw ork learning met hod s pro vide a rob ust algorithm to interpret real-w orld sensor data [20], and it has been widely used in the field of solar ener gy [21]. Artificial intelligence techniques can be used for sizing PV systems: stand-alone PVs, grid-connected PV systems, and PV -wind h ybrid systems [22]. There are man y learning algorithms that can be used in our w ork [23, 24, 25], b ut it w as sho wn in the literature that ANN systems were pro v en to pro vide e xcellent prediction and classification results in similar applications such as [26] and [27]. 3.3. ANN Experiments and Optimisation In this research w ork, an ANNs netw ork model w as created with v e inputs representing the solar irradiance ( I r r ) records at the same time of the pre vious v e days that are associated with a current solar PV output po wer ( P ) which represents the tar get function (output node). So, if the mean po wer v alue for the hour h on day d is represented Solar PV P ower F or ecasting in J or dan using Artificial ... (Alomari) Evaluation Warning : The document was created with Spire.PDF for Python.
500 ISSN: 2088-8708 Figure 3. The associated PV po wer and irradiance data (0 on the time axis corresponds to 15 May 2015). Figure 4. The structure of ANN. by P h ( d ) , then it is associated with the irradiance v alues at the same hour h for the pre vious v e days: I r r h ( d 1) , I r r h ( d 2) , I r r h ( d 3) , I r r h ( d 4) , I r r h ( d 5) . All training and testing e xperiments were carried out using the MA TLAB ANNs toolbox with the aid of the back-propag ation learning algorithm [28]. T o optimize the model performance, the number of hidden layers w as IJECE V ol. 8, No. 1, February 2018: 497 504 Evaluation Warning : The document was created with Spire.PDF for Python.
IJECE ISSN: 2088-8708 501 incremented from 1 to 30 and at each v alue of hidden layers, ten e xperiments were carried out using a dif ferent set of randomly mix ed samples consisting 80% of the samples (15399 samples) for training, 5% for v alidation, and 15% for testing. The a v erage RMSE for each of ten e xperiments is calculated to e v aluate the performance per specific number of hidden layers. A total of 300 sets of training, v alidation, and testing e xperiments were handled and the best ANN config- urations were found to pro vide an a v erage RMSE of 0.0721 and best v alidat ion MSE of 0.0053397 using 22 hidden layers for the testing performance illustrated in Figure 5 and Figure 6. These results are v ery good compared to the methods and measures reported in the literature and related to the current research. Figure 5. Correlation coef ficients calculations. A tw o-days prediction for the PV ener gy production for 23 and 24 May 2015 w as simulated using our model (see Figure 7 (left)) and the system pro vided a RMSE=0.0234 and correlation coef ficient of R=0.9983 which means an almost perfect linear relationship between solar irradiation and the output po wer generated. In addition a ten-days simulation for the duration from 20 to 30 July 2015 pro vided RM SE=0.0333 and R=0.9965 as illustrated in Figure 7 (right). 4. CONCLUSIONS In this w ork, a machine learning model is proposed to analyses historical solar PV output po wer and solar irradiance data to pro vide a set of decision rules that represent a proper prediction system. All data records in the duration from 16 May 2015 to 30 September 2017 were used in this research w ork and the ANNs-based system pro vided promising results. W e belie v e that this w ork is the first to predict the ne xt-day solar PV output po wer using real time irradiation data measured accurately at a weather station that is located at the same geographical area of the PV plants. Solar PV P ower F or ecasting in J or dan using Artificial ... (Alomari) Evaluation Warning : The document was created with Spire.PDF for Python.
502 ISSN: 2088-8708 Figure 6. ANN e xperiments using 22 hidden layers. Figure 7. Measured and forecasted PV ener gy production for 23-24 May 2015 (left) and 20-30 July 2015 (right). A CKNO WLEDGMENT The authors w ould lik e to ackno wledge the financial support recei v ed from Applied Science Pri v ate Uni v er - sity that helped in accomplishing the w ork of this article. REFERENCES [1] W . Hof fmann, “Pv solar electricity industry: Mark et gro wth and perspecti v e, Solar Ener gy Materials and Solar Cells , v ol. 90, no. 18, pp. 3285 3311, 2006. [2] I. E. Agenc y , “T echnology roadmap: Solar photo v oltaic ener gy 2014 edition, P aris, France, 2014, last accessed: IJECE V ol. 8, No. 1, February 2018: 497 504 Evaluation Warning : The document was created with Spire.PDF for Python.
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504 ISSN: 2088-8708 02 2014. [27] R. Qahw aji, T . Colak, M. Al-Omari, and S. Ipson, Automated prediction of cmes using machine learning of cme flare associations, Solar Physics , v ol. 248, no. 2, pp. 471–483, Apr 2008. [28] S. E. F ahlman and C. Lebiere, “The cascade-correlation learning architecture, in Pr oceedings of the 2Nd Inter - national Confer ence on Neur al Information Pr ocessing Systems , s er . NIPS’89. Cambridge, MA, USA: MIT Press, 1989, pp. 524–532. BIOGRAPHIES OF A UTHORS Mohammad Alomari is currently an Associate Professor of Electrical Engineering (Solar Systems) at Applied Science Pri v ate Uni v ersity , Jordan. He recei v ed his B.Sc. and M.S. de grees in Electrical Engineering (Communications and Electronics) from Jordan Uni v ersity of Science and T echnology , Irbid, Jordan, in 2005 and 2006, respecti v ely and the PhD de gree from the Uni v ersity of Bradford in 2009. His research interests include smart and green b uildings, solar PV applications, space weather and solar ener gy , computer vision, brain computer interf ace and digital image processing. J ehad Adeeb recei v ed his B.Sc. de gree in Mechanical Engineering from Al-Balqa Applied Uni- v ersity , FET , Amman, Jordan, in 2015. He is mainly responsible of Systems Monitor ing and Main- tenance, alongside with training of students and supporting graduation projects technically . His research interests include Rene w able Ener gy and Ener gy Ef ficienc y , Green Building and PV P anels T echnologies. Ola Y ounis is currently a full-time PhD student at the School of El ectrical Engineering, Electronics and Computer Science at the Uni v ersity of Li v erpool, United Kingdom. She recei v ed her B.Sc. de gree in Computer Science from Jordan Uni v ersity of Science and T echnol ogy , Irbid, Jordan, in 2010 and her M.S. de gree in 2012 from Philadelphia Uni v ersity , Jordan. Her research interests include digital signal, image, and video processing, computer vision, vision impairment assisti v e technology , and Bio-inspired Softw are Engineering. IJECE V ol. 8, No. 1, February 2018: 497 504 Evaluation Warning : The document was created with Spire.PDF for Python.