Screw piles are fast becoming one of the most commonly used means of securing solar arrays. They’re cost-effective, easy and fast to install, and they work in a wide variety of ground conditions. But one of the main concerns that solar project managers should be concerned with is “uplift”. The design of solar arrays makes them inherently vulnerable to uplift, particularly in exposed locations and high wind events. In worst case scenarios wind can “catch” the solar panels and tear from the ground leading to massive unforeseen costs. So, what can you do to protect your solar arrays against the damaging effect of uplift?
Preventing Uplift in Solar Arrays with Screw Piles
What impacts uplift in solar arrays
As mentioned above, wind is the primary cause of uplift in solar arrays. But the potential for uplift is impacted by three main issues:
- The way that the solar arrays are anchored – There are various means of anchoring ground solar arrays. These include screw piles, shaft piles, ground screws, concrete pads and driven piles. One of the reasons that screw-piles are so popular is because they can provide some the best uplift protection.This is because their “end bearing plate” which as well as supporting the load of the panel, also acts as an anchor.
- Wind direction – While you can’t control the direction of the wind, you can familiarise yourself with the typical conditions in your region. Although weather systems, thunderstorms, and differing terrain all have an influence, the Coriolis force, typically deflects wind to the right in the northern hemisphere and to the left in the southern hemisphere. And this knowledge can provide a useful guide when assessing the placement of your solar arrays.
- Panel tilt angle – Similar data can be used to determine the most resilient panel tilt angle for solar arrays.
Why are screw piles considered a good choice for limiting uplift in solar arrays?
The primary value that helical piles bring to reducing uplift in solar arrays is the ability to conduct lateral load testing and pull testing. Uplift typically takes place when too much lateral or pull force is applied to the solar array. By performing in-depth lateral and pull load testing, you can ensure that your solar arrays have the maximum capability to withstand lateral forces. This testing removes the guesswork by giving you accurate data with which to base your screw-pile design.
What influences lateral and pull load capacity in screw piles?
There are several factors that can influence the lateral load capacity of a screw-pile foundation.
- Soil conditions – A dense soil type, such as clay, will always offer more lateral strength than a loose sub soil, such as sand.
- Depth of embedment – The deeper a screw pile is embedded, the stronger the foundation it will provide.
- Width of the piles – Thicker screw piles are typically used for heavier applications. However, because they deliver a higher tension and compression load rating, they can also be useful where stronger lateral forces are likely.
- The number of helices in place – The more helices a screw pile has, the greater the lateral capacity it can deliver. Recent research has shown that an extra flight of helices can increase lateral resistance by 5-10%.
- Size of the Helix. Roughly speaking the bigger the helix the better load and pull capacities of the pile
Reducing the risk of uplift will always be a challenge in the installation of solar arrays. But it’s the high performance of screw piles in this area that is proving invaluable in solar fields around the world.
Do you need advice on the use of screw piles for the installation of solar arrays? Get in touch with UK Helix.