The Glaring Effects of Solar Panels
For some locations, the addition of solar panels may cause a concern, the blinding glare created from the reflective surfaces can make a safety concern as it can impact the daily operation of staff. WINAICO has several design features to help counter such effects without affecting its performance.
Maximising Performance and Minimising Reflected Light
Any material exposed to light will to different proportions absorb, transmit and reflect the light. Materials that are ‘darker’ will tend to absorb more light, whereas ‘lighter’ materials will be more reflective. Materials with a lower density (like water or glass) will allow more light to be transmitted, as there are less particles for the light waves to ‘bounce’ off as they travel through the material. These materials will refract (i.e. bend) the light if it strikes the material at an angle
Figure 1 Solar Panel Layers
Figure 2 Light incidence, reflection, and refraction (not to scale) (https://www.pveducation.org/pvcdrom/design-of-silicon-cells/light-trapping)
Solar panels are made of layers, with a glass front sheet protecting the silicon solar cells which produce the electricity, with the panels sitting on a polymer back sheet and encapsulated (i.e., laminated) in an EVA material.
Solar Glass is designed to transmit the maximum amount of light so that the solar cells can absorb it. Glass as a material has a good light transmission, however normal glass has some reflection, and this becomes much greater as the angle of incidence of the light increases.
To counter this a low iron glass is selected which has high transmission in the wavelength suited for solar power production. Solar glass can also use an anti-reflective coating which greatly reduces the reflection of light, especially at high angles of incidence. The below figure shows the improvement in light transmission from the application of an anti-reflective coating:
Figure 3 Comparison of light transmission Coated vs Uncoated glass
Solar cells are designed to absorb as much light as possible to maximise electricity production. This is achieved in part by texturing the cells, effectively making their surface ‘rougher’, and meaning that any reflected light will be scattered often back onto the cell leading to higher absorption.
Figure 4 Solar Panel Texturing (https://www.pveducation.org/pvcdrom/design-of-silicon-cells/surface-texturing)
Solar cells also use an anti-reflective coating to allow more light to be absorbed. These coatings increase transmission, and also utilise refraction effects to trap as much light as possible in the solar cells.
WINAICO solar panels use low iron tempered glass with a transmission of over 94% in the visible spectrum. This glass minimises light reflection and maximises the amount of light our panels absorb. This not only increases our panels’ performance but means they reflect less light than other building materials and therefore are suitable for reflection sensitive insulations.
Figure 5 Transmission of light for WINAICO Solar Glass (Official test report)
WINAICO panels are installed at Fiji’s Nadi International Airport due, with a 200kW array powering the Air Traffic Services facility. WINAICO panels were selected due to their low reflective properties, high resistance to salt mist corrosion and excellent all-around performance. Additionally, WINAICO’s extensive dynamic mechanical load testing was a crucial factor in selecting a panel which could withstand cyclone wind speeds regularly experienced in the pacific islands.