M. Drapalik

About the usability of a photovoltaic module to monitor air pollution

The responsivity by means of the quotient of photo-current and incident global light intensity of a solar module situated in central Vienna was analyzed during a period where an ash cloud of volcanic origin was spread over central Europe in spring 2010. A timely coincidence between anomalies of the registered responsivity and the concentration of ash particles in the air was found. However due to the lack of reliable directly observed particle concentration no correlation could be established.

A study of vibration induced distortion on the performance of photovoltaic converters

Mechanical vibrations of a solar module cause oscillations in the orientation of the module towards the sun, resulting in a low frequency a.c. current component at the modules terminals. We have investigated this effect and performed model calculations in order to estimate the influence on the feed back control of a converter.

Effects of Ultrasonic Cleaning on Carrier Lifetimes and Photovoltage in Monocrystalline Silicon

Effects of a kHz-frequency ultrasonic cleaning of silicon wafers on free carrier lifetimes and the photovoltage magnitude are addressed. It is found that the initial photovoltage decay, taken before ultrasonic treatments, can be fitted to a double-exponent form, exhibiting the involvement of shorter- and longer time recombination and trapping centers. The decay speeds up remarkably due to the treatment, and the rapid component of the decay grows at the expense of the slow component. It is also found that, before the treatment, the decay time is markedly non-uniform over the wafer surface, implying the existence of distributed sites affecting carrier lifetimes. The cleaning causes an overall smoothening of the lifetime distribution, which is accompanied by the above shortening. A likely explanation of the effects is based on two facts: (i) the cavitating bubbles are capable of locally removing the surface oxide layer affecting the dangling bonds on the bare Si surface, and (ii) the oxygen and hydrogen, decomposed in water at elevated pressures and temperatures occurring inside a cavitating bubble, can micro-precipitate the Si wafer thus affecting the recombination rate.