Can flat plate collectors still absorb sunlight effectively in winter?

Winter Solar Performance

Flat plate collectors generally perform well in mild winter conditions, but their efficiency drops significantly in areas with heavy snowfall or prolonged periods of low solar irradiance. In a study conducted in Colorado, flat plate collectors lost about 30% of their winter efficiency when snow covered 10% of the collector surface. To mitigate this effect, consider using a snow-melt system or using a collector with a higher solar irradiance rating.

Collector Orientation and Angle

To maximize winter performance, ensure your flat plate collector is installed at an angle that optimizes solar gain. In the Northern Hemisphere, a south-facing collector with an angle of 30-40 degrees provides the best results. However, this angle may need to be adjusted to 15-25 degrees in areas with heavy snowfall to prevent snow accumulation on the collector surface.

Combining with Evacuated Tube Collectors

If you’re already considering a solar hot water system, consider combining a flat plate collector with an evacuated tube collector. Evacuated tube collectors maintain higher efficiency in cold temperatures and can provide a backup system in case the flat plate collector is snow-covered. By combining these two systems, you can ensure a reliable and efficient solar hot water supply even in harsh winter conditions.