Solar carports and agrivoltaics: structure, clearance and yield

A carport that generates power and a field that grows crops under panels both solve the same underlying problem: land is expensive or unavailable, and rooftops alone will not deliver the gigawatts national plans assume. Elevated PV over parking or farmland recovers land that already has another primary use.

This article is for developers, agricultural cooperatives and facility owners evaluating whether an elevated structure - over asphalt or over soil - is a sound investment relative to a conventional ground-mount, and what changes in structural design, permitting and yield once the land underneath keeps its own job.

Both applications share a structural logic: taller, sparser support points than a ground-mount, larger unsupported spans, and design loads driven as much by the activity underneath (vehicles, machinery, livestock) as by wind and snow. The economics diverge sharply from a simple ground-mount, and that divergence is often underestimated at the proposal stage.

Solar carports: structure and clearances

A solar carport is a cantilevered or portal-frame steel structure supporting PV modules over one or more rows of parking, typically at a single slope of 5-10 degrees or as a double-pitched canopy over back-to-back rows. Clear height requirements are the first constraint: most codes require a minimum of 2.4-2.75 m clearance for standard vehicles, rising to 4.2-4.5 m where the site must accommodate delivery vans, fire trucks or municipal buses.

Column spacing is set by the parking module: a typical single row of perpendicular parking needs columns on a 2.5-3.0 m spacing along the row and a cantilever of 5-6 m over the parking depth if columns are placed only at the back of stalls (avoiding columns between cars). Longer cantilevers cost more in steel per kWp but improve usability and reduce vehicle strike risk.

Loads specific to carports

Carport structures see the same wind and snow loads as any elevated PV structure, but with additional considerations: vehicle impact loads on columns (usually a nominal horizontal design load per applicable structural code, unless bollards are used), drainage design to avoid channeling roof runoff onto pedestrian walkways, and lighting/EV charging integration that adds point loads and conduit runs the structural model must include from the start, not retrofit later.

Agrivoltaics: what dual land use actually requires

Agrivoltaic systems mount PV above active cropland, pasture or, less commonly, aquaculture, at heights and densities chosen to let the underlying use continue. Three configurations dominate:

• High-clearance fixed tilt or tracking structures (4-6 m clearance) over row crops, allowing tractors and combines to pass underneath.
• Vertical bifacial rows spaced widely apart, used over pasture or grazing land, which shade the ground only briefly at low sun angles.
• Elevated fixed structures over permanent crops (vines, berries) at 2.5-4 m clearance, sometimes replacing hail netting.

The defining trade-off is light: crops need photosynthetically active radiation, and PV modules by design intercept it. Reported agrivoltaic trials show land equivalent ratios (LER) above 1.0 for shade-tolerant crops (some leafy greens, certain berries) at module coverage of 20-30 percent, meaning combined crop-plus-energy output per hectare exceeds either single use - but LER falls below 1.0 for sun-loving row crops like maize once coverage exceeds roughly 20 percent, and yield loss becomes the dominant economic factor rather than the energy gain.

Structural and access implications

Foundations need wider spacing than an equivalent ground-mount because the priority is unobstructed ground area, not the smallest steel package per kWp. Typical agrivoltaic foundation spacing runs 6-12 m depending on crop machinery track width, versus 3-6 m for a standard ground-mount. This raises steel content per kWp by roughly 30-60 percent relative to a conventional ground-mount, an increase that must be recovered through land-value or subsidy mechanisms, not through energy yield alone.

Worked example: cost and yield trade-off

Take a 1 MWp array considered as (a) a conventional ground-mount, (b) a solar carport over an existing car park, and (c) a high-clearance agrivoltaic structure over arable land, all at the same site with 1,150 kWh/kWp/year reference yield at ground level.

Ground-mount: structural cost approximately EUR 90,000/MWp (steel + foundations only, excluding modules/inverters), no land-use offset, full reference yield of 1,150 MWh/year.

Carport: structural cost approximately EUR 260,000/MWp (elevated steel frame, larger footings, drainage), but the land underneath (parking) needed no separate acquisition and continues generating its own revenue (parking fees), and reduced ground shading of asphalt yields a small array temperature benefit at the module - assume yield unchanged at 1,150 MWh/year for this comparison.

Agrivoltaic (high clearance, tracking, 25 percent ground coverage): structural cost approximately EUR 210,000/MWp, with a module-level yield discount of roughly 5 percent from lower coverage tracking optimized partly for crop light rather than pure energy capture, giving about 1,093 MWh/year, but the land retains an estimated 70 percent of its normal crop revenue.

The delta in structural cost for the carport versus ground-mount is EUR 170,000/MWp, or EUR 170/kWp. If land acquisition or lease avoided by using existing parking is worth more than EUR 170/kWp over the structure's life, the carport clears the bar; if the land was cheap or already owned outright, the ground-mount usually wins on pure LCOE. The same logic applies to agrivoltaics: the EUR 120,000/MWp cost delta over ground-mount must be justified by land rent avoidance, crop revenue retention, or a premium tariff/subsidy specifically for dual-use installations, several of which exist in France, Germany and Japan.

Permitting and grid considerations

Carports usually fall under building/planning permission processes similar to any structure over that footprint, plus separate electrical permitting for the array; parking authorities may impose additional requirements on drainage, lighting and fire lane clearance. Agrivoltaic projects increasingly have dedicated planning categories in some EU member states that require a minimum retained agricultural yield (commonly 66-80 percent of a reference unshaded yield) to qualify for agricultural land status and associated tariffs; falling short reclassifies the land as industrial, with different tax and permitting consequences.

Common mistakes

• Sizing carport steel for wind and snow only, ignoring vehicle impact and drainage requirements until construction.
• Assuming agrivoltaic yield loss is negligible without running or reviewing site-specific shading and crop trial data.
• Underestimating foundation spacing needs for farm machinery, forcing later rework of access lanes.
• Treating carport EV charging integration as a bolt-on rather than part of the initial electrical and structural design.
• Skipping the agricultural land-use retention threshold check before committing to a subsidy-dependent business case.
• Comparing agrivoltaic or carport LCOE directly against ground-mount LCOE without pricing in the land-use benefit being retained.

Frequently asked questions

Do solar carports need different fire safety provisions than rooftop PV?

Yes in most jurisdictions; carports require rapid shutdown and firefighter access considerations similar to rooftop systems, plus specific rules for vehicle emergency egress and lighting, which should be confirmed with the local fire authority early in design.

What crops perform best under agrivoltaic panels?

Shade-tolerant crops such as lettuce, certain berries and some forage grasses generally show the smallest yield penalty or even a benefit from reduced heat stress and evapotranspiration; sun-loving row crops like maize or wheat show the largest yield losses at typical PV coverage densities.

Can existing car parks be retrofitted with carports without new grid capacity?

Sometimes, if the site already has adequate grid connection headroom, but MW-scale carports usually require a new or upgraded connection point, and this should be checked with the distribution network operator before detailed design.

Is tracking worthwhile on agrivoltaic structures?

Single-axis tracking can be tuned to shade crops during peak heat stress hours and open up light at other times, improving both energy and crop outcomes in some trials, but it adds mechanical complexity and cost that must be justified by the specific crop's light requirements.

How is land equivalent ratio (LER) calculated?

LER sums the fractional crop yield under PV (relative to an unshaded reference plot) and the fractional energy yield (relative to a full-coverage reference array), so an LER above 1.0 means the combined output per hectare exceeds what either single use would produce alone.

Standards and references

• EN 1991-1-1: Eurocode 1, Actions on structures - General actions, densities, self-weight, imposed loads
• EN 1991-1-4: Eurocode 1, Wind actions (applies to elevated PV structures)
• IEC 62548: Photovoltaic (PV) arrays - Design requirements
• Fraunhofer ISE, Agrivoltaics: Opportunities for Agriculture and the Energy Transition
• IRENA, Renewable Energy and Agriculture reports
• IEA PVPS Task 8/13, land use and dual-use PV analyses
• NREL, InSPIRE agrivoltaics research program publications

See also system sizing, payback calculator, the glossary, and our companion pieces on wind and snow loads on PV structures and array layout and row spacing.