Spacing and tilt

The Spacing & Tilt group holds two numbers — the tilt angle of the module plane and the row pitch between rows of tables — and both are derived for you by default. The group contains nothing but two override checkboxes and the two value fields they unlock, because in the normal case you enter nothing here at all.

It appears in Fixed Tilt mode only. A tracker has no fixed tilt and no derived pitch, so choosing a tracker mode at launch removes this group; see Tracker configuration.

The fields

Two definitions before going further. Tilt is the angle between the module plane and the horizontal, measured toward the equator — south in the northern hemisphere, north in the southern. Pitch is the row-to-row repeat distance measured on the ground, perpendicular to the rows, and it is not the gap between rows: it includes the ground the tables themselves stand on.

The automatic behaviour

With both boxes unticked, which is how the group ships, tilt is derived from where the site is and pitch is derived from that tilt.

Tilt from latitude

The tilt angle follows a latitude rule of thumb:

tilt ≈ latitude × 0.76 + 3.1°

Latitude is the site latitude in degrees, taken from the geographic position of the boundary file. The rule tracks the well-established result that the best fixed tilt for annual yield sits somewhat below the site latitude, and flattens further as you approach the equator.

A KMZ or KML boundary carries its position already. A CAD drawing or an image does not, which is why those two inputs offer a coordinates window when you load them. Supply the coordinates there and the derivation has what it needs.

Energy yield is a separate matter: with no coordinates, Calculate Energy is disabled outright, so no misleading generation figure is produced. See CAD drawing boundaries.

Pitch from the winter solstice

The automatic pitch is the closest row spacing that produces no inter-row shading at solar noon on the winter solstice:

pitch = L × cos(tilt) + L × sin(tilt) ÷ tan(solar elevation)

Every term:

So the pitch is the table's own footprint plus the length of the shadow its top edge throws at the chosen moment.

What the winter solstice condition buys

The winter solstice is the day of the year the midday sun sits lowest in the sky, so it casts the longest midday shadow. Sizing the pitch for solar noon on that day means:

• No inter-row shading at solar noon on any day of the year. Every other day's midday sun is higher, so its shadow is shorter than the spacing you have already allowed for.
• Not "no shading ever". Early in the morning and late in the afternoon the sun is low on any day, and rows do shade one another. That residual loss is what the shading figure in the energy settings accounts for; it is not designed away by the pitch.

This is the standard, defensible starting point for a fixed-tilt plant, and it is deliberately conservative. Sites where land is expensive routinely accept a tighter pitch and a small shading loss in exchange for capacity, which is what the override is for.

Ground coverage ratio

Ground coverage ratio — GCR — is the collector area divided by the ground it is spread over:

GCR = table height ÷ row pitch

The table height here is the same L as above, the tilted face length, so GCR is a plain number between zero and one. It is not a field: you never enter it. It is reported from the geometry once tilt and pitch are settled, and it feeds two calculations — the row-to-row shading loss, which is computed from GCR automatically unless you switch that off, and the rear-side irradiance of a bifacial module, which falls as GCR rises because dense rows leave less lit ground to reflect.

What a higher GCR trades:

Because GCR follows from pitch, the way to move it is to move the pitch. Read the resulting shading loss before accepting a tighter figure — see Shading losses.

Overriding either value

Tick Override tilt angle or Override row pitch and the matching field becomes editable; the derivation for that value stops being used. The two are independent — you can override one, the other, both or neither.

Override tilt when the site is anything other than an unshaded flat field facing the equator: a fixed structural standard across a portfolio, a slope that makes a shallower angle sensible, a soiling regime that rewards a steeper one. Override pitch when land cost, a road grid, an existing pile layout or a specified GCR sets the spacing rather than a shading condition.

After a run, the derived values are shown and pre-filled

Generate a layout with the overrides off and the group changes usefully. Each automatic label reports the value that was actually used — for example Auto → 12.3° (latitude-based) and Auto → 7.42 m (no-shading, latitude-based) — and those same values are pre-filled into the greyed-out override fields.

This is the sequence worth using deliberately:

In the summary table under the plot, a tilt or pitch that was derived rather than entered carries a trailing asterisk, so a printed summary always says which of the two figures you chose and which the application worked out. The marking appears for Fixed Tilt designs only.

Tilt and pitch are coupled

Tilt appears twice in the pitch formula — once projecting the table onto the ground and once setting the height of its upper edge — so a change of tilt is a change of automatic pitch. A steeper array stands taller, throws a longer midday shadow in midwinter, and needs more room behind it.

That makes the four combinations meaningfully different:

Overriding one and leaving the other automatic is a deliberate choice, not a half-finished one. Fixing the tilt and letting the pitch follow keeps the shading condition; fixing the pitch and letting the tilt follow keeps the land use. Fix both only when an external constraint gives you both numbers.

Where to go next