Light Shelf Development Using Folding Technology and Photovoltaic Modules to Increase Energy Efficiency in Building

Some recent research in the area of light shelves has been focused on applying photovoltaic modules to light shelves to save building energy. However, due to the modules installed on the light shelf reflectors, most such light shelves have failed to improve both daylighting and generation efficiency. This study proposes a folding technology to improve light shelves’ daylighting and generation efficiency that uses photovoltaic modules and validates their performance using a testbed. The major obtained findings are as follows: (1) The proposed folding technology has a structure in which reflectors and photovoltaic modules fold alternately by modularizing the light shelf. The reflector and photovoltaic modules are controlled by adjusting the degree of folding. (2) Because light shelf angles for improving daylighting and generation differed depending on the application of the photovoltaic module, the optimal light shelf specifications differed. (3) Compared to previous light shelf technologies, the light shelf with folding technology and a photovoltaic module reduced energy use by 31.3% to 38.2%. This demonstrates the efficacy of the proposed system. (4) Applying a photovoltaic module can lower the indoor uniformity ratio, which means that the daylighting performance of the light shelf is degraded due to the reduction of the area occupied by the reflector.

Application of Infrared Thermography in an Adequate Reusability Analysis of Photovoltaic Modules Affected by Hail

Infrared thermography, in the analysis of photovoltaic (PV) power plants, is a mature technical discipline. In the event of a hailstorm that leaves the PV system without the support of the power grid (and a significant portion of the generation potential), thermography is the easiest way to determine the condition of the modules and revive the existing system with the available resources. This paper presents research conducted on a 30 kW part of a 420 kW PV power plant, and demonstrates the procedure for inspecting visually correct modules that have suffered from a major natural disaster. The severity of the disaster is shown by the fact that only 14% of the PV modules at the test site remained intact. Following the recommendations of the standard IEC TS 62446-3, a thermographic analysis was performed. The thermographic analysis was preceded by an analysis of the I-V curve, which was presented in detail using two characteristic modules as examples. I-V curve measurements are necessary to relate the measured values of the radiation and the measured contact temperature of the module to the thermal patterns. The analysis concluded that soiled modules must be cleaned, regardless of the degree of soiling. The test results clearly indicated defective module elements that would result in a safety violation if reused. The research shows that the validity criterion defined on the basis of the analysis of the reference module can be supplemented, but can also be replaced by a statistical analysis of several modules. The comparison between the thermographic analysis and the visual inspection clearly confirmed thermography as a complementary method for testing PV-s.

Effects of Reflectance of Backsheets and Spacing between Cells on Photovoltaic Modules

In the photovoltaic (PV) module manufacturing process, cell-to-module (CTM) loss is inevitably caused by the optical loss, and it generally leads to the output power loss of about 2~3%. It is known that the CTM loss rate can be reduced by increasing the reflectance of a backsheet and reflective area through widening spaces between the PV cell strings. In this study, multi-busbars (MBB) and shingled PV cells were connected in series, and a mini-module composed of four cells was fabricated with a white and black backsheet to investigate the effects of reflectance of backsheets and space between the PV cells. Moreover, the MBB modules with cell gap spaces of 0.5 mm, 1.5 mm, and 2.5 mm were demonstrated with fixed 3 mm spaces between the strings. The shingled modules with varying spaces from 2 mm to 6 mm were also tested, and our results show that spacing between PV cells and strings should be well-balanced to minimize the CTM loss to maximize the output power (efficiency).