Will evacuated tube collectors work effectively on a shaded roof?

Impact of Shading on Evacuated Tube Collectors

Evacuated tube collectors are designed to absorb and transfer heat from sunlight. However, when these collectors are shaded, their performance decreases. Shading can occur due to nearby objects, trees, or even the roof’s design. The amount of shading can significantly impact the collector’s efficiency, with even slight shading reducing its performance by up to 20%. For example, a 10% reduction in direct sunlight can lead to a 2-3% reduction in collector efficiency.

Mitigating the Effects of Shading

To mitigate the effects of shading on evacuated tube collectors, it’s essential to consider the following factors: the location of the collectors on the roof, the size and type of shading objects, and the collector’s design. In some cases, rearranging the collectors or pruning nearby trees can help reduce shading. Alternatively, using a smaller collector size or increasing the number of collectors can help compensate for the reduced efficiency. Additionally, selecting collectors with a higher efficiency rating or using a more efficient heat transfer fluid can also help offset the impact of shading.

Design Considerations for Shaded Roofs

When designing a solar hot water system for a shaded roof, it’s crucial to account for the reduced collector efficiency. This can be achieved by oversizing the collector array or using a more efficient water heater. For example, a collector array that would normally require 10 collectors in full sun may require 12-14 collectors in a shaded area. By taking these design considerations into account, it’s possible to achieve an effective solar hot water system even on a shaded roof.