Path-Q Solar

How should a chimney's shadow be modeled before deciding whether to use that roof section?

Answer

Model the chimney as a three-dimensional obstruction over the full year, not as a single daytime shadow observation. The analysis should include the chimney's height and position, roof geometry, sun paths by season, nearby obstructions, panel layout, and the electrical effects of partial shading.

Key points

  • Shading is often most important during lower-sun periods, when shadows are longer.
  • The impact depends on when the shadow falls relative to valuable production hours and how many modules are affected.
  • Panel-level or string-level electrical design can change the effect of partial shading.

What it depends on

  • Chimney height, width, location, and roof orientation
  • Site latitude, seasonal sun position, and nearby obstructions
  • Panel placement, module electronics, and system design

Risks and trade-offs

  • A simple visual check can understate annual losses.
  • Moving panels away from the chimney may reduce shading but also reduce usable roof area.
  • Removing or modifying a chimney may affect building operation and should not be assumed feasible.

Information you may need

  • Accurate roof and chimney dimensions
  • A site-specific annual shading report or time-based simulation
  • Alternative layouts and their estimated production

Your next step

What to do next

Ask the installer to provide an annual shade analysis showing the chimney's effect on each proposed panel area and layout.

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SQ02383