Solar power is currently the fastest growing source of renewable electrical energy on a global scale. Typically, solar panel manufacturers guarantee a lifetime of 25-30 years for their panels. However, the surrounding environmental conditions make solar panels prone to different degradation and ageing phenomena. Degraded panels produce less power than those in a good condition. In order to detect the ageing of solar panels, a decent condition monitoring procedure is required. A suitable approach is to utilise the electrical measurements of solar panels that can be implemented by the already existing equipment at solar power fields.
Several condition monitoring approaches based on electrical measurements have been presented in literature. However, only few of them are suitable for practical applications. According to doctoral candidate Heidi Kalliojärvi, two fundamental problems have been encountered.
“A condition monitoring procedure should be independent of external temperature and irradiance measurements. This is because the sensors registering the solar panels’ operating irradiance and temperature seldom exist in practical solar fields,” Kalliojärvi says.
“Secondly, the application of the condition monitoring procedure must not require the rundown of the solar power plant for the measurement period. Most of the existing condition monitoring procedures fail to satisfy these requirements,” she adds.
Kalliojärvi developed a new mathematical procedure that can be used to draw conclusions from the condition of solar panels. In particular, the procedure can be utilized for the detection of possible ageing in the solar panel. The application of the method does not require any preliminary information of the operating temperature or irradiance. In addition, the solar power plant can continue its power production during the diagnostic measurements.
“No sophisticated extra equipment is needed. The inverter is enough,” Kalliojärvi points out.
Heidi Kalliojärvi lives in Valkeakoski and is currently working on the Hervanta campus of Tampere University.
Public defence on Friday 19 January
The doctoral dissertation of M.Sc. Heidi Kalliojärvi in the field of electrical energy engineering titled Detection of single-diode model characteristic values from measured current-voltage curves for online condition monitoring purposes of photovoltaic power systems will be publicly examined at the Faculty of Information Technology and Communication Sciences of Tampere University at 12 o’clock on Friday 19 January on the Hervanta campus, Sähkötalo building, auditorium S2 (Address: Korkeakoulunkatu 3, Tampere). Assistant Professor Patrizio Manganiello from the Delft University of Technology, Netherlands, will act as the opponent. Professor emeritus Seppo Valkealahti from Tampere University will act as the custos.