Aside from the quantity of solar panels that will be needed to offset a family or business’ electrical consumption, the most important decision to be made when deciding to go solar is where the panels are to be mounted.
If the roof of a home or building is not ideal for mounting, a ground mount racking system is most likely the only other option.
To correctly install a ground mount racking system, the first step is to find out what the best foundation for a ground mount solar array is going to be.
And the short answer is: it depends.
There are a few factors to take into account when choosing a foundation for a ground mount racking system. Soil composition, weather conditions and size of the array are the main factors.
In this article we will highlight three of the most popular foundation types and explain when and why each may be chosen.
1. Driven Beams
Driven beams are large support beams, usually made of steel that are driven into the ground at a pre-determined depth. The racking structure and panels are then attached to the beams.
Most of the time only a single beam is used for support, therefore it must be driven deep into the soil at depths of 8-10 feet or more in order to have the underground support needed to hold and brace the weight that will be set upon it.
Some installers opt to burrow holes, place the beams inside of the holes and pour cement into the holes to encase the beams, while others use heavy machinery like pile drivers to drive the beams into the ground with extreme force.
The driven-beam method is thought to be the most durable for the ground mount racking system as the beams are very sturdy and hold a lot of weight.
Of course, if the soil is extremely rocky or if there is shallow bedrock under the soil, the driven beams will not suffice as they need the extreme depth and another method must be used.
2. Anchors
Another method that works well, especially in soil conditions that may have obstructions such as rock, shallow bedrock or even soft, sandy soil with low friction are foundation anchors.
Anchors such as ground screws or helical piles allow for a shallow foundation installation, usually 3-5 feet deep opposed to the driven beam’s 8-10 feet.
Anchors can be installed into burrowed holes with concrete poured around them, but most installers use light machinery such as a skid steer with an auger adapter to drill the anchors into the ground, much the same way a drywall screw is driven into a wall.
Most anchored ground mount racking systems require two anchors, one in the front and one in the rear to hold the weight of the racking materials and panels.
The ground screws, with its pointed tip drills easily into the soil and push away rocks as it protrudes into the shallow depths. A percentage of the screw threads must be driven below the frost line to prevent frost heave over time.
Ground screws can also be driven into bedrock after a pre-drilled hole has been made if the soil is too shallow above the bedrock to hold the screws in place.
Helical piles do not install well into rocky soil as the helix blades can bend or break when coming into contact with rock or hard clay.
The helical piles are best suited for softer soils with sandy loam as the helix blade creates a cone effect allowing it to resist high pullout loads. The helix blade must be driven below the frost line in order to prevent frost heave over time.
3. Ballast
Ground-mounted systems do not always have to penetrate the earth.
There are some situations in which a driven beam or anchor cannot be used at all. Those situations include shallow bedrock, buried electrical or water lines, extremely hard, compacted dirt or capped landfills and brownfields among others.
When the ground cannot be penetrated at all due whatever factor, a ballasted foundation is a great method for installing a ground mount racking system when the traditional methods will not suffice.
A ballast foundation is a man-made foundation that is heavy enough to hold the racking system and panels in place as it sits firmly on top of the ground. Most racking systems that require a ballast foundation use afront and rear post to distribute the weight of the materials that hold the rack and panel in place.
Most ballast foundation systems are made of concrete as that is the fastest and easiest way to form a heavy pad large enough to hold the ground mount racking system into place.
Although there are other types of ballast systems, such as the Geo Ballast by APA Solar Racking that use a large steel basket, containing quarry rock or other aggregate with enough weight to equal the durability of the more common concrete-made ballast blocks.
To view the Geo Ballast and see its technologically-advanced features, visit www.apasolar.com where there are photos and videos of the Geo Ballast used in multiple large and small-scale solar projects.
The stationary ground mount foundations highlighted in this article are just a few of the methods used to mount solar panels as there are many other ways as solar design progresses.
As the solar industry grows, there is sure to be advancements and improvements in the technology used to harness the power of the sun.
Single poles, vertical fencing and even water floatation devices are used in the modern realm of mounting solar panels in the most ideal way to capture and industrialize solar power.
In fact, an 8.9 megawatt floating solar array went online in 2023 in New Jersey, unveiling North America’s largest solar project on water. Click on the following link to read about this ground-breaking solar project and how floating solar farms have several advantages over land-based installation. https://solareyesinternational.com/solar-news-the-largest-floating-solar-farm-in-north-america-comes-online/#google_vignette
When it comes to mainstream residential and commercial solar projects, ground mount racking systems are king when roofs are impractical for mounting solar panels.
It is useful to know what other options are available and to what extent those options can be used for maximizing production when investing in a solar system for home, business or industrial needs.
