Browsing by Author "Meli, Menelaos"
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- ItemA unique radiometric measurement station design incorporating spectral and image data collection(Stellenbosch : Stellenbosch University, 2022-04) Meli, Menelaos; Rix, Arnold J.; Strauss, Johann; Stellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering.ENGLISH ABSTRACT: The performance of photovoltaic (PV) panels is determined under standard test condi tions (STC). However, in practical PV installations, it is rare for PV panels to operate under the STC at which they are rated. The variation in spectral irradiance under dif ferent atmospheric conditions significantly i mpacts t he p erformance of P V p anels. The output of a PV power plant is also significantly a ffected a s a l arge c loud b ank travels across the sky above. The passing clouds attenuate the received solar spectral irradiance and reduce the output power. Sudden changes in output power of a grid connected plant, as a result of clouds, may lead to voltage and frequency oscillations and result in system instability. Accurate short-term irradiance prediction models are important tools used to manage these power fluctuations. However, many irradiance prediction models and software tools used in the PV industry do not take these spectral impacts on PV performance into account. There is a lack of measurement stations dedicated to collecting the data necessary to improve these prediction models and software tools. A unique radiometric measurement station is designed and built in this thesis for the collection of data required by researchers to improve upon irradiance forecasting models and PV software tools. The instruments on the measurement station include: a pyranometer, a pyrheliometer, a wide field-of-view (FOV) spectral irradiance meter, a narrow FOV spectral irradiance meter and a digital camera. The instruments are mounted on a pan/tilt unit that is able to accurately track the position of the sun in the sky throughout the day for solar elevation angles greater than 10◦ . The data collected by the station includes temperature, humidity, air pressure, broadband irradiance and spectral irradiance. Images of the sky correlating to the various irradiance measurements are captured by the onboard digital camera. The measurement station is designed to be solar powered, compact and weather-resistant, allowing it to be deployed in remote locations for data collection. The station is configured t o c apture a m easurement s et o f d ata o nce e very 1 0 minutes in 4 distinct measurement positions: facing directly towards the sun, facing north with optimal tilt, facing north with a fixed 30◦ tilt, and facing north with a 0◦ tilt. The mea surement frequency and measurement positions can be configured by the user as necessary. The broadband irradiance measurements are validated by comparison to data collected by an independent measurement station nearby. The correlation between the spectral irradiance measurements and the AM1.5 reference spectrum is shown, as well as the vari ation of the solar spectrum during different seasons, different times of day and different cloud conditions. The measurement station is found to fulfil all requirements and successfully collects the data required to improve irradiance prediction models and PV software tools. This station has the potential to help optimize PV power stations as well as domestic PV installations.