This paper presents an integrated thermal and electric simulation model for the operation of photovoltaic (PV) modules and strings. The dynamic thermal model is based on the total energy balance in the module in which all essential heat transfer mechanisms between the module and the environment are modeled theoretical. The electric model is based on the well-known one-diode model and a method is introduced to derive the unknown parameters from the manufacturer's information datasheet. The complete model has been implemented in Matlab Simulink software for a PV module and a PV string of six series-connected modules and validated using environmental and electric measurements of the TUT solar PV power station research plant during 20 days of the summer and autumn in 2013. The input parameters used by the integrated simulation model are the received solar radiation on the tilted plane of the PV modules, the global and diffuse solar radiations received on the horizontal plane, the wind speed and direction and the ambient temperature. The accuracy of the predicted module temperatures and the complete power voltage (P-V) curves has been evaluated by means of the root mean square error (RMSET) and the normalized root mean square error (NRMSEP), respectively. The results show a good agreement between the predicted and measured module temperatures and P V curves. The average RMSET and NRMSEP values during the measurement period were 1.34 degrees C and 1.98%, respectively. (C) 2014 Elsevier Ltd. All rights reserved.