Row spacing for ground-mounted systems.

L is the length of the table along its slope, from front edge to rear edge. β is the tilt of the table. c/c (pitch) is the distance between the front edges of two rows, and the clear gap between rows is c/c minus the horizontal depth of the table, L·cos β.

Land use is often given as GCR (ground coverage ratio): the module area divided by the ground it occupies. For long rows this is L divided by c/c. A GCR of 0.5 means the module area is half the ground area.

On level ground the shadow depends only on the height of the table above its own front edge, L·sin β, and on the position of the sun. How high the whole table stands above the ground does not change the spacing between identical tables, but it does affect snow clearance and access underneath.

Requiring unshaded rows at the winter solstice makes sense in southern Europe but costs a lot of land in the north. Winter also carries different weight. With a south-facing panel at 25°, November–January gives 4.3% of annual yield in Stockholm according to PVGIS, 8.4% in Kassel, 15.7% in Rome and 17.6% in Madrid. December alone is 1.0% in Stockholm and 5.7% in Madrid.

In the north, winter shading therefore costs few kWh, and a tighter pitch than the unshaded one can give more energy per hectare. In Spain and Italy, shade around midday costs a larger part of the year. Where the line falls depends on the price of land, the capacity of the grid connection and what the shading costs in kWh – and the last of these is worked out with an hourly shading simulation.

Lowering the tilt from the optimum to 25° costs 1.5–3.9% per kWp in a stand-alone row but shortens the unshaded row spacing by 13–32%. More kWp fit on the same land, and each row casts less shade. A shallower tilt therefore gives more energy per hectare in exchange for a small loss per panel.

The same formulas apply to rows on flat roofs, using the depth of the panel instead of the table. There the roof area is fixed and the clear gap between rows is often small. That is why south-facing rows on flat roofs are compared with east–west systems, which have a guide of their own.

In Ritwerk you set the row spacing for south-facing rows on flat roofs in metres, and the designer shows the c/c between the rows. The rows shade each other in the shading analysis, so the effect of a shorter spacing shows panel by panel.

Sweden. Latitude makes row spacing the big question. At noon on the winter solstice the sun stands 7.2° above the horizon in Stockholm, and in Kiruna (67.9° N) it stays below the horizon all day. There the criterion has to be set for another date, or the winter shading accepted. The optimum tilt from PVGIS for Stockholm is 44°.

Germany. In Kassel the sun stands at 15.3° at noon on 21 December, and the optimum tilt from PVGIS is 38°. EEG § 37 Abs. 1 Nr. 2 sets out where ground-mounted systems can receive support in the EEG auctions – among them already sealed surfaces, conversion areas, a strip of up to 500 m along motorways and railways measured from the outer edge of the carriageway, and arable land or grassland in disadvantaged areas.

Spain. In Madrid the sun stands at 26.1° at noon on the winter solstice, and November–January gives 17.6% of annual yield, so winter shading costs more than in the north. Under Ley 21/2013 (Annex I, group 3 j), PV installations that are not on roofs and occupy more than 100 ha require an ordinary environmental assessment. Smaller ground-mounted systems may fall under the simplified assessment in Annex II, group 4 j.

Italy. In Rome the sun stands at 24.7° at noon on the winter solstice, and the optimum tilt from PVGIS is 36°. DL 63/2024 (art. 5, converted by Law 101/2024) restricted PV with ground-mounted modules in areas classified as agricultural to certain areas and put the rule in art. 20 of d.lgs. 199/2021. That article has since been repealed, and the rule in force is now in art. 11-bis(2) of d.lgs. 190/2024: permitted areas include disused quarries and mines and closed landfills, with exceptions for renewable energy communities and PNRR projects. The rule has changed several times, so check the version in force on Normattiva before a project.