OUTDOOR THERMAL AND ELECTRICAL CHARACTERIZATIONS OF PHOTOVOLTAIC MODULES AND SYSTEMS

RESEARCHER IN THE SPOTLIGHT

The worldwide total installed solar photovoltaic (PV) capacity has increased approximately 50 times over the past decade (from 3 GW in 2005 to over 180 GW in 2015), and is set to be one of the main technologies which can provide power with almost no carbon dioxide emissions. Investors of PV systems have a few potential questions on their mind when considering photovoltaics. These questions revolve around “How well is my system performing now, and how will it perform in the future?” and “Will I recover my investment?”.

Similar to a car with a broken or imprecise speed meter, a PV system without (specialised) monitoring will do the job, yet the owner may not know how good or bad, the system is working. If the measured yield is approximately the same as the promised or expected yield, then the customer will be happy. However, a very sunny or cold year may have skewed the results positively, and the customer may have paid too much for the system. On the other hand, a very hot year may lead to lower than expected performance, where a customer may come to the wrong conclusion on their system's performance. Therefore, one of the first aspects to look at is to compare the energy output of the system to the amount of solar energy received over the same period, which is called the Performance Ratio (PR). This PhD thesis introduces the power equivalent of the PR, which is called the normalised efficiency.

Using the measurement set-up which was designed and built in this PhD, it is shown how the normalised efficiency and similar tools can be used to determine how good a system is working, even in real-time. The effect of temperature (the efficiency of PV systems decreases with higher temperature) can be corrected and other aspects that influence the system performance may be observed. Shading (which can lead to large energy and therefore monetary losses) can be detected, and the performance of one system can be compared to the next – such as between neighbouring systems. With these results, businesses and their customers can enter a dialogue on the performance of the system based on objective instead of subjective criteria. An easy-to-apply model is also developed, which can later be used for active system performance monitoring – such as calling maintenance for a system at an earlier stage, so that more energy is produced and the customer’s return on investment guaranteed.

Bert Herteleer