Glossary · Row layout
Panel tilt angle
The angle between the panel plane and the horizontal; it affects yield, snow (μ), wind (c_f) and row pitch. Kyiv’s optimum is about 36°.
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Definition
The tilt α is the first decision in a ground PV design, and it touches almost everything else. No norm sets it, but standardised quantities depend on it: the shape coefficient μ of DBN V.1.2-2:2006 and the force coefficient cf of EN 1991-1-4:2005.
What changes with tilt
| α | μ (snow) | cf uplift |
|---|---|---|
| 20° | 1 | −1.3 |
| 25° | 1 | −1.6 |
| 30° | 0.857 | −1.8 |
| 35° | 0.714 | beyond Table 7.6 |
A steeper table sheds snow but is lifted harder by wind, and the row pitch grows because the shadow gets longer. A flat table is more compact but carries all the snow and yields less in winter.
Example: Kyiv
Solispec’s annual yield model gives an optimal tilt of about 36° at Kyiv’s latitude (50.45°). A few degrees either way changes annual energy little, so in practice 30° is often chosen: μ = 0.857 instead of 0.714 at 35°, but cf stays within Table 7.6 of EN 1991-1-4:2005 and the row pitch is shorter. For a table 2.35 m long along the slope, the noon sun on the winter solstice (16.1° high) gives a pitch of about 6.1 m at 30° and 6.6 m at 35°.
How Solispec applies it
The Solispec engine takes the optimal tilt from a polynomial fit of the annual optimum over latitude — the same annual yield model the constructor uses. The chosen tilt then sets μ and cf in the load calculation, the row pitch and the truss geometry. You can compare options in the tilt and row spacing calculator and see the effect on returns in the payback calculator.
Norms and clauses
- DBN V.1.2-2:2006, cl. 8.7, Annex Zh, scheme 1
- EN 1991-1-4:2005, Table 7.6
Related terms
- Row spacing (pitch)The pitch of ground PV rows at which rows do not shade each other in a set window around noon on the winter solstice.
- Snow shape coefficient μThe conversion from ground snow to roof snow: μ = 1 up to 25°, 0 from 60°, linear in between (DBN V.1.2-2:2006, Annex Zh, scheme 1).
- Aerodynamic coefficient Caer (cf)The multiplier turning wind pressure into force on a shape; for panels Solispec takes c_f from Table 7.6 of EN 1991-1-4:2005, as cl. 9.8 of the DBN allows.
- BallastDead weight (concrete blocks, gravel trays) that keeps a PV table from wind uplift and sliding without anchoring into the ground or roof.
- DBN V.1.2-2:2006 “Loads and actions”: what matters for a solar plantNorms explained
Solispec’s calculation is preliminary: for a design it has to be checked by an engineer. The values and clauses follow the current editions of the norms on the date of the page.