Solar Inter-Row Shading Distance Calculator
Understanding Solar Array Inter-Row Shading
For solar engineers laying out ground-mount and flat-roof arrays, correctly determining inter-row spacing is crucial. This calculator precisely fixes the row pitch that keeps the 21 December (or 21 June in the southern hemisphere) shadow off the next row's lowest cells. This is the critical scenario that decides whether a roof can accommodate 40 rows or only 34, directly impacting array density and energy yield. It uses the formula D = H * (cos(azimuth) / tan(altitude)) for optimal accuracy.
How to Use This Calculator
- Set the length unit: Choose between meters (m) or feet (ft). Both H and D will use this unit.
- Enter H (obstacle height difference): Input the vertical height difference between the top of the front row (or obstruction) and the lowest point it must not shade on the row behind. This should be in your selected length unit.
- Enter solar altitude angle: Input the winter-solstice solar altitude angle in degrees for your specific site. This is the lowest noontime altitude of the year.
- Enter solar azimuth angle: Input the solar azimuth angle from true south for that same winter solstice moment. 0° means the sun is due south and perpendicular to an east–west row, while ±90° means the sun is along the row.
- Read D: The calculator will display D, the minimum required row-to-row distance. The substituted formula line will also show the numbers you typed for verification.
Frequently Asked Questions
Q: Which solar altitude angle should I enter for inter-row spacing?
A: The lowest noontime altitude of the year — the winter solstice — because that is when shadows are longest; the calculator applies D = H × (cos(azimuth) / tan(altitude)) to that worst case.
Q: Why is the azimuth measured from true south rather than from north?
A: Because the cos(azimuth) term is the angle between the sun and the row normal: at 0° the sun is due south and square to an east–west row, so cos = 1 and the spacing is the full H ÷ tan(altitude); as the sun swings toward the row ends the term shrinks.
Q: What exactly is H in D = H × cos(az) ÷ tan(alt)?
A: The vertical height difference between the top of the front row or obstruction and the point on the row behind that must stay unshaded — a rise, not the module slant length, not the module width, and it must be in the same length unit as the D you want back.
Q: What happens if I enter a solar altitude of 0°?
A: tan(0) = 0, so D is undefined — the sun sits on the horizon and the shadow has no finite length, which is why the calculator flags the case instead of dividing by zero; results here are for preliminary estimation only and are not a substitute for review by a qualified/licensed engineer.