ENERGY INFRASTRUCTURE // PARTNER SOLUTIONS
SELECTING THE RIGHT
FOUNDATION FOR
GROUND-MOUNTED
PV PANELS
S
electing the right foundation for a ground-mounted solar PV installation is critical for its success as the use of an incorrect foundation can result in premature refusal, costly change orders and project delays. Selection should be based on a geotechnical study of the project area to determine the best option. Here, we will look at the different types of foundation, and how to select the right one for your installation. Jeff Lawson, National Construction Equipment Sales Manager at Vermeer, said there are four main types of foundation that can be used for ground-mounted solar PV systems. “There are four major types of foundations that are commonly used: helical piles, earth-screws, ballasted foundations and driven piles,” Mr Lawson said. “When selecting a foundation type, and the machinery that will be used to install it, it is important to understand the positives and negatives of each type of different ground condition. “For example, areas with loose sand and a high water table or low soil cohesiveness require the foundation to be embedded at a greater depth so a helical pile or ballasted foundation would be the best choice. “However, in areas with harder, more difficult terrain, earthscrews and ballasted foundations are better. “Driven piles on the other hand are best suited to areas with good soil cohesiveness and low water tables.”
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September 2018 // Issue 8
Helical piles Helical piles are best suited to areas where soil cohesion is poor as they are easily installed using auger attachments on excavators or other equipment that can rotate it into the ground. Once installed, they act as an anchor and lock the structure into the soil. They require only a small amount of earth to be dug out, so contractors can save time and money. They also have minimal environmental impact as there is little noise pollution and little to no ground movement. A pull test needs to be done before installing helical piles to determine the embedment depth and ensure there is enough resistance to satisfy the load requirements of the PV support structure. Earth-screws Earth-screws can be installed by pre-drilling holes into the ground before they are screwed in using excavators and other equipment which use auger attachments. They can also be installed straight into the ground if there are no refusal issues. Earth-screws can have a higher cost of installation than other foundation types if a separate machine is needed to be brought in for pre-drilling. Ballasted foundations Historically, ballasted foundations have been more expensive than driven or screwed foundations, however over
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