Winter in Canada
As we know, winter in Canada means shorter days; the sun rises late and sets earlier. For those who rely on solar energy for their electrical needs, it becomes even more challenging with 50% fewer hours of sunlight compared to summer. That's why it's said that in winter, it charges less...
Cold Increases the Efficiency of Solar Panels
Why? Just like any semiconductor (electronic component), low temperatures increase electrical efficiency. This is why it's important for a computer to stay tempered to remain efficient. It's the same for solar panels. The colder it is, the better they perform.
Solar panels are more efficient in winter, which compensates a bit for the lack of sunlight. However, to fully benefit from this, a MPPT solar controller is needed, a more sophisticated controller that offers better performance. With a regular (PWM) controller, you will hardly notice any difference.
How to calculate it
There are several calculations to assess the efficiency of solar panels in cold weather. Normally, on the back of solar panels, you'll find a table with values based on STC standards, which include several environmental factors, including the temperature at 25°C.
To make the calculation, we need to know:
- the STC value;
- the temperature coefficient* for the desired value, whether it's watts, amperage, or voltage;
- and the temperature difference between the desired temperature and 25°C (STC).
*Temperature coefficients are generally found on the panel's technical datasheet.
Calculation Example at -30°C
For example, let's see how much more efficient a 140W panel is in winter at -30°C. The power temperature coefficient (W) is -0.45%/°C. The temperature difference is 55°C [-30°C (desired temperature) - 25°C (STC) = -55°C].
So, the formula would be: (140W x 55°C x 0.45%) = 34.65, 140W + 34.65 = 174.65 Watts.
Since the power temperature coefficient is negative and the temperature is dropping, we need to add the difference in watts to the original value.
The panel performs significantly better at -30°C with 174 Watts compared to 140 Watts at 25°C.
Calculation Example at 40°C
We want to know how performance is affected at 40°C. The temperature difference is 15°C [40°C (desired temperature) - 25°C (STC) = 15°C].
So, the formula would be: (140W x 15°C x 0.45%) = 9.45, 140W - 9.45 = 130.55 Watts.
Since the power temperature coefficient is negative and the temperature is rising, we need to subtract the difference in watts from the original value.
The panel performs significantly worse at 40°C with 130.55 Watts compared to 140 Watts at 25°C.
Other Uses for This Calculation
This calculation method helps us to:
- Determine the maximum voltage of a series of solar panels to ensure we do not exceed the MPPT controller's limits.
- Determine the maximum power of the solar panels to know which fuse and/or circuit breaker to install on the regulator when designing a solar system.
In Conclusion
Even though solar panels perform better in the cold and you're using an MPPT solar controller, the shortened daylight hours in winter can be more problematic. A good analysis of your energy needs with one of our experts when designing a solar system will help you better cope with the winter.
