With the booming solar photovoltaic industry, more and more people are using solar systems in their homes, or solar-powered items in daily life, like solar-powered heaters, solar garden lights, etc.
Sometimes, people will focus on the solar panel quality as they want more lighting at night, as a better solar panel enables more energy stored in the batteries, which can ensure long-lasting time.
It is well known that the power of the solar panel is a vital factor to decide the solar panel quality. The wattage is higher, the working current is higher, the charging efficiency is better. Most people choose solar panels by comparing solar panel power.
However, if we dig inside the discharging characteristic of the solar panel, we will find that solar power is one of the factors that affect the solar panel quality, but not the only one.
Here is an example:
Assume that we have two solar panels A & B, they are all with the voltage 6V, power 30W, theoretically their charging performance is same. But is it correct?
Based on an ideal algorithm, within a standard sunshine daytime, the rated output current is I=30W/6V=5A. However, it will never get a constant 5A current through the whole day.
In practical application, due to the various kinds of geographical environment and weather conditions, there is almost no theoretical sunshine. Sometimes it rains, sometimes it has too many clouds in the sky, the sunshine change between weak or strong. As a result, the solar panel works in an unconventional environment 80% of the daytime probably, especially during dusk and dawn.
Now you may understand that it is meaningless to focus on the theoretical calculation formula, as the output current you calculate requires stable sunshine all the time, but it won’t happen even a day. Most of the time the solar panel receives weak sunshine and is hard to reach the rated output current.
Thus, the most important factor we always ignore is the low light performance of the solar panel, which decides how the solar panel works under weak sunshine.
What is the low light performance for the solar panel?
Low light performance, or low light efficiency of the solar panel, is the discharging efficiency of the solar panel during low light conditions.
Quoted from the academic sites:
“The low light performance/behavior of a solar panel is mainly dependent on the shunt resistance and series resistance of the cells.”
During low light condition, the solar panel discharging perfomance ensure the lowest value of the solar system charging, we can say it as a basement of the solar panel quality.
How can I know a solar panel’s low light performance is good or not?
Unfortunately, the testing of solar panel low light performance is difficult, it requires specific professional equipment, many factories or manufacturers don’t even have this testing ability.
However, we consumers can still have a way to compare the low light performance of solar panels by doing simple testing.
Assume you have two solar panels from different suppliers, the solar panels have the same power, same voltage, etc. Of course, you need to confirm the battery spec is also the same, it means these solar panels have the same system solution. Make them work under the sun during dawn, noon, and dusk, test and check the output current and working power respectively, then you can have the result that which solar panel has the better low light performance.
There will be no big difference during sunny days, but when it comes to rainy days or cloudy days, the low light performance will make big difference.
Welcome to contact us if any questions about this topic.