Inspecting PV-plants using aerial, drone-mounted infrared thermography system

Paper presented to the 3rd Southern African Solar Energy Conference, South Africa, 11-13 May, 2015.Worldwide more than 140 GW photovoltaic plants are installed. The demand for testing methods for quality control of installed photovoltaic modules is increasing. Imaging techniques, like infrared imaging, are very popular. There are several advantages, providing two-dimensional images, measuring during operating conditions, fast and contactless as well as non-destructive. Mounting an infrared camera to a drone enhances the inspection but some specialties have to be considered. There are several factors influencing the image quality, as the observation angle, the flight altitude, the flight velocity which have to be chosen properly. Besides the influence of the measurement parameters, IR-images of PV-plants and single modules will be shown. Depending on the temperature distribution evidence for specific failure modes are given. Thus, cell fracture, soldering failure, short-circuited cells, by-passed substrings, can be distinguished easily using IR-imaging. Further analyses verify the negative impact of the identified defects on the module performance.cf201

Single-stage sealing of ceramic tiles by means of high power diode laser radiation

An investigation has been carried out using a 60 W high power diode laser (HPDL) to determine the feasibility of sealing the void between adjoining ceramic tiles with a specially developed grout material. A single-stage process has subsequently been devised using a new grout material which consists of two distinct components: a crushed ceramic tile mix substrate and a glazed enamel surface; the crushed ceramic tile mix provides a tough, inexpensive bulk substrate, whilst the enamel provides an impervious surface glaze. HPDL processing has resulted in crack and porosity free seals produced in normal atmospheric conditions. The single-stage grout is simple to formulate and easy to apply. Tiles were successfully sealed with power densities as low as 750 W/cm2 and at rates of up to 420 mm/min. Bonding of the enamel to the crushed ceramic tile mix was identified as being primarily due to van der Waals forces and, on a very small scale, some of the crushed ceramic tile mix material dissolving into the glaze

Defects and performance of Si PV modules in the field – an analysis

Photovoltaic installations will likely become one of the major power sources in the 21st century and we need photovoltaic modules to operate reliably. In this review, we explore what is known today about the status of installed crystalline silicon photovoltaic modules in the world, how different sources classify module defects, and what we might deduce for future installations. Looking at more than 200 results from 132 installations and 79 reports, we find that PV modules in general are robust in outdoor operation, with about one in 250 modules failing completely each year. About one in ten modules will develop a defect resulting in greater than expected power loss throughout their lifetime, and practically every module will develop visually perceivable alterations. We observe no trends of changes over time in these findings, hence there is no indication that future performance will deviate dramatically. We note though that more information is needed. Available studies represent a module fleet with greater age than current installations, and are over-representing multicrystalline – compared to monocrystalline silicon, and AL-BSF – compared to PERC cell architectures. Studies from Asia and Africa and from tropical climates are underrepresented. A major challenge in the analysis was the variety of metrics used. To facilitate easier comparison, we propose reporting guidelines

Quantitative Assessment of the Influence of Camera and Parameter Choice for Outdoor Electroluminescence Investigations of Silicon Photovoltaic Panels

With the spread of photovoltaics (PV) and increasing diversity in PV panel technology, quantitative comparison of the modules is highly desirable for consistent on-site quality assessment. Electroluminescence imaging reveals many defects, such as macroscopic crystal or electrical contact defects, but quantitative comparison outside the laboratory without controlled environment is still difficult, especially for different detector technologies. Here, we show how this problem can be addressed by adding reference spots in the module area: One passive dark spot and an active bright spot composed of a high-power back-contacted silicon PV cell. Those reference spots are used to evaluate the module's electroluminescence signal under different environmental conditions and to establish comparable results. Additionally, the comparison of images acquired with different camera technology detectors, such as silicon and InGaAs, is realised for signal levels