Glossary · Row layout
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.
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Definition
No norm sets the row spacing: it is pure sun geometry. A row casts its shadow northwards, and the longest shadow falls on the winter solstice, when the sun’s declination is −23.44°. If rows do not shade each other on that day, they will not shade each other for the rest of the year within the same window of hours.
At noon the row pitch equals the table’s horizontal depth plus the shadow of its top edge:
P = L · (cos α + sin α / tg h)Example: Kyiv
At Kyiv’s latitude the noon sun height on 22 December is about 16.1°. A one-panel portrait table (L = 2.35 m) at 30°: P = 2.35 · (0.866 + 0.5 / 0.289) ≈ 6.1 m. That is over six metres between the front edges of neighbouring rows, while the table itself occupies only 2 m horizontally.
Requiring no shade over a window, say 10:00 to 14:00 solar time, rather than just at noon makes the pitch larger still. A flatter tilt shortens it: the shadow is shorter, but annual yield drops and the snow load grows. The pitch always balances plot area, shading loss and panel count.
How Solispec applies it
The Solispec engine takes a declination of −23.44°, computes the sun’s height and azimuth every 5 minutes within the chosen window around solar noon and finds the longest north–south shadow of the top edge. The pitch is the table depth plus that shadow, rounded up to 10 mm. With a zero window it is exactly the noon formula. Both the tilt and row spacing calculator and the constructor work this way.
Related terms
- Panel tilt angleThe 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°.
- 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.
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.