Measuring Actual Operating Conditions of a Photovoltaic Power Generator

Photovoltaic (PV) modules are composed by PV cells, normally connected in series, which convert the energy of solar radiation (direct and diffuse) into electrical energy. However, many factors affect the output power of photovoltaic devices that are operating such as module temperature, incident irradiance and spectral irradiance distribution. Subsequently, the climatic parameters involved on the module temperature, such as ambient temperature, relative humidity and wind speed and direction, must be studied too. In this thesis a state-of-the-art climatic measurement facility is designed and built to measure the climatic and operating conditions of the TUT solar PV power test plant. This climatic measurement system contains an accurate weather station that also includes solar radiation measurements in parallel to a comprehensive mesh of irradiance and module temperature measurements all around the solar facility. First the climatic instruments and possible data-acquisition architectures are introduced in order to understand the measuring methods and the different possible solutions for the system. A market study is needed as well to gather the most suitable devices for the system. In this thesis also a thermal model of the modules is developed using MatlabTM Simulink software to analyse the influence of the environmental parameters on the operating conditions and the performance of the PV modules and strings. Simulations show a clear dependence of the module temperature on the ambient temperature, wind speed and irradiance conditions. Regarding the generated power and string efficiency, increasing ambient temperature and wind speed causes a negative and positive influence, respectively. Measurements of module temperature and irradiance show the appearance of a delay between the curves caused by the thermal inertia of the modules. This phenomenon was not considered in the model, which is meant to predict the module temperature in a stationary state. Small error appears between the measured module temperature and the simulated one as well as with the string performance results. However, the results confirm the right performance of the thermal model and measuring system. /Kir1