Solar lights function based on the principle of ‘photovoltaic effect’ and solar panel is the key component of photoelectric conversion in solar LED street lights. They convert solar energy into electric energy to illuminate the LED lights from dusk to dawn. A PV module is made up of solar cells, ethylene-vinyl acetate (EVA), glass, back sheet and frame. There are mainly three types of solar panels - monocrystalline solar panels, polycrystalline solar panels and amorphous (thin film) silicon solar panels.
The most often used panels are monocrystalline and polycrystalline solar panels and the most common query of solar buyers is which panel is suitable for solar street light. Both the panels have around 25 years of warranty and technology wise, one is not inferior to another. Depending on your lighting needs and your location, you may choose the type of solar panel. Though both these panels work on the same principle, there are some differences between the two.
Polycrystalline solar panels are the most used for solar street lights as they are priced at a lower rate than monocrystalline solar panels. They do not require individual shaping during their making and are more eco-friendly. They are able to perform better even in low light conditions and have a higher temperature coefficient and high power density. Polycrystalline solar panels are best suited for most parts of India as they are more effective in warm weather conditions. For polycrystalline solar panels, the maximum accepted temperature is 85 degree Celsius.
Polycrystalline solar panels consist of multiple solar cells, where each cell contains silicon crystals which help it to act as a semiconductor device. Fragments of silicon are melted together to form solar panel wafers. The whole vat of molten silicon is allowed to cool on the panel and this cooling process causes multiple crystals to form. This gives a ‘marbled’ or ‘mosaic’ effect with a shining blue hue.
Polycrystalline panels contain either 60 or 72 solar cells and having multiple crystals in each cell makes it difficult for electrons to flow. This type of structuring brings down the efficiency rate of polycrystalline panels slightly lower than monocrystalline solar panels. The efficiency rating of a polycrystalline panel is usually around 13% to 17%. With the recent technological advancements, the efficiency of polycrystalline panels is becoming almost the same as monocrystalline panels, close to 20%.
Polycrystalline solar panel technology is the most predominant technology in the solar industry. They are also known as multicrystalline panels and are a popular choice among home owners looking to switch to solar-powered lighting units on a budget. Solar panels either come as separated units or are integrated into the solar LED street lights, depending on the type of street light.
Statistically, a solar panel experiences around 0.8% efficiency loss per year. If a solar panel is maintained well, the performance of the panels can be improved. India overall has a moderate climatic condition; hence the degradation rate of solar panels is relatively low here. However, polycrystalline solar panels have a higher degradation rate than monocrystalline solar panels. But as long as the panels are not damaged and if they continue to produce adequate electricity for your needs, they may not need replacement even after their warranty time.