Ground-mount solar for commercial sites

A ground-mount array is a steel or aluminium frame that holds the panels in fixed rows across open land rather than on a building. It suits commercial sites with land to spare: a haulage yard, a former lagoon, set-aside ground next to a unit, or a field a landowner wants to put to work. Because the array is not tied to a roof, the row pitch, tilt and orientation can be set for yield rather than for whatever the building happens to offer, and maintenance access is at ground level.

The engineering question that decides everything else is how the frame is anchored, and that is a ground question rather than a catalogue choice. The two broad routes are penetrative foundations, where posts are driven or screwed into the ground, and non-penetrative ballast, where the frame is held down by weight on the surface. Which one a site needs is determined by the soil, the water table and the wind loading, confirmed by the geotechnical survey for your ground. This page sets out the principles so you know what shapes the design before we model it.

On most ground with reasonable bearing capacity, the frame is anchored by foundations that penetrate the soil. Driven piles are steel posts hammered directly into the ground to a depth the engineering calls for. Screw piles, sometimes called ground screws, are threaded posts wound into the soil like a large screw. Both transfer the array's wind and weight loads into the ground without concrete in the common case, which keeps the groundworks light and the install quick, and both can be removed at end of life so the land returns to its prior state.

The right depth, post spacing and pile type are an engineering output rather than a fixed number, because they depend on the soil's bearing capacity, the wind zone and the array's exposure. A trial pile or pull-out test on site gives the real holding capacity of your ground, and the foundation design is confirmed from that test and the geotechnical survey rather than assumed from a standard table.

Some sites rule out driven or screwed foundations: a capped landfill or contaminated ground where the membrane must not be pierced, a hardstanding slab, made ground full of obstructions, or a site where penetration is not permitted. There the array sits on a non-penetrative ballasted frame, held in place by weight on the surface, typically concrete blocks or ballast trays, with no anchor breaking the ground.

Ballast is a deliberate engineering trade. The frame stays on the surface, but it must carry enough mass to resist wind uplift and sliding across the whole array, and the ground beneath has to bear that distributed load. The ballast mass needed for your site is calculated against the wind loading and the surface it sits on, confirmed by the structural calculation and the geotechnical survey, not taken from a generic figure.

On open land the array geometry is set for performance rather than dictated by a roof. Rows are pitched and spaced so that, through the working day and across the year, one row does not throw shade onto the row behind it more than the design allows. A wider row gap lifts winter yield and cuts inter-row shading but uses more land, so the layout balances energy against the area available. Orientation is usually toward the south for output, though an east-west layout can pack more capacity onto a tight plot.

The tilt angle, row pitch and any tracking are chosen against your latitude, the land area and the shape of the plot, then modelled in PV*SOL so the predicted yield reflects the real geometry and the real horizon. Nearby trees, buildings and the site's own slope are built into that model rather than ignored, because the shading on your ground is specific to your ground.

Ground-mount is where bifacial modules can earn their place. A bifacial panel generates from its rear face as well as its front, picking up light reflected off the surface beneath and behind the array. On the ground that rear-side gain depends on the surface albedo: pale gravel, concrete or grass reflects more than dark earth or tarmac, and a higher frame that sees more reflected light gains more than a low one. The gain is real but site-specific, so it is modelled for your surface and array height in PV*SOL rather than assumed from a headline percentage.

Cell technology is chosen on the same evidence basis. TOPCon, heterojunction and PERC are different cell architectures with different trade-offs in efficiency, behaviour in heat and cost per watt, and none of them is universally best across every site. On a ground array where land is plentiful, a bankable value module on a wider layout can beat a premium module on a tighter one, so we name the specific module, its scheme and its grade for your project and re-verify the credential before contract.

Ground-mount carries obligations a rooftop array does not. Permitted development rights for stand-alone ground arrays on commercial land are far more limited, so most schemes beyond a modest size need a full planning application that weighs landscape, ecology, drainage and access, and that adds lead time to the programme. The grid connection is sized to the array's export and applied for with the network operator early, because the connection terms can shape the viable capacity.

Because a commercial ground array sits above 50 kWp and outside the MCS scheme, the assurance comes from engineering rigour, named component standards and compliance with the CDM 2015 construction duties rather than a domestic certificate. We run the geotechnical survey, the structural calculation, the planning route check and the PV*SOL model as one survey-led process, so the layout you sign off is one that can be founded, consented and built on your land. Installs are contracted by RVTC LTD.

An open-field array is fully exposed, with no building to shelter it, so the dominant force on the structure is wind. Wind acts on the panel plane as both pressure and uplift, and because the rows stand proud of the ground the load tries to lift the front edge, push the array sideways and overturn it about the rear foundation. The frame, the foundations and the panel clamps all have to carry that load path into the ground. Snow adds a downward case that bears on the modules and the rails, and on a tilted array it can drift and slide, loading the lower edge unevenly.

The loads themselves are not a single catalogue number. They are derived from the wind code and the snow code for your specific location, exposure and array height, which in UK practice means the structural Eurocodes for wind action and snow load applied with the national parameters for your site, then carried through the frame design and the foundation design. The fixed electrical installation is built and tested to BS 7671, while the structure answers to structural standards and the CDM 2015 duties rather than a domestic certificate. We do not quote a load figure on a web page, because the right figure is calculated for your ground and your wind zone rather than read off a standard table. That structural calculation, alongside the geotechnical survey, is what fixes the post spacing, the pile depth and the ballast mass before any row is set out.

Most ground-mount problems trace back to the ground or the loading being misjudged, and naming the failure modes is the clearest way to see why the survey work matters. Wind uplift pulling a row free is the headline risk on an exposed plot, so the foundation and the ballast calculation are driven by uplift as much as by the array's downward weight. Frost heave can lift a shallow foundation over successive winters until the rows go out of alignment. Differential settlement, where one part of the array sinks faster than another across variable ground, racks the frame and stresses the module clamps. On sloping or poorly drained land, surface water scour can wash material away from a foundation and undermine it.

Two slower failure modes also sit in the design life. Buried steel corrodes at a rate set by the soil chemistry the survey measured, so the wrong section or the wrong protection shortens the life of the foundation. And ground movement on made or reclaimed land, including ongoing settlement of a former tip, keeps acting on the structure long after commissioning. A ballasted frame answers a different subset of these, because it cannot heave or corrode below ground, but it must instead carry enough mass to resist sliding and overturning across the whole array. Designing against the right failure modes for your ground is precisely what the structural calculation and the geotechnical survey exist to do, which is the same engineer-led process we run for every commercial system.

A ground array changes the electrical job as much as the structural one. The DC string cabling runs across open land between rows and back to the inverters, so it is routed in cable trays or buried ducts, protected against rodents, UV and mechanical damage, and kept to string lengths that hold the voltage drop within limits. Long DC runs across a field are a real design constraint, and where the geometry pushes them too far the inverter positions or the string design are revised so the losses stay within limits.

Earthing and bonding carry extra weight on the ground. The frame, the foundations and the array are bonded and earthed to BS 7671 so a fault cannot leave exposed metalwork live in a space people and machinery move through at ground level, and an exposed open site usually warrants lightning and surge protection that a sheltered roof might not. Because the array sits at head height and within reach rather than high on a roof, isolation, labelling, fencing and DC protection are designed so the system is safe to be near and safe to work on. All of this is part of the survey-led design and is contracted and installed by RVTC LTD, the trading name behind Alectrona, with the whole installation tested and certified before it is energised.