Experimental Study of Pulling-Out Capacity of Foundation for Solar Array Mounting Frames

Abstract

Solar energy became the cheapest mode of energy generation in recent years because of the cost-effective techniques causing exponential reduction of solar installation cost. Solar arrays installed in these solar farms are susceptible to wind-driven forces, which may uplift array and mounting frame foundation. Due to high wind, extensive damages of the solar panels, array mounting frame, and foundations have been observed globally in the recent past. A number of the solar array foundation failed due to the uplifting of the foundation by intensive wind-induced lift forces. To improve pull-out resistance of solar array foundations, a comparative experimental study was done to determine the pull-out capacity of steel pile having varying diameter and length in three different soil conditions, i.e. clayey soil, sandy soil, and mixed soil. Helical piles were found to be a cost-effective improvement over plain piles to resist uplift forces. A mathematical expression is also proposed based on a number of soil and pile parameters, to determine the pulling-out capacity of helical piles, and analytically determined capacity is compared with experimental findings. Reliability analysis was also done to determine the effectiveness of the proposed mathematical expression to determine the pull-out load. Earlier, a numerical study has been carried out for the determination of wind loads over various solar arrays tilted at different angles and subjected to extreme wind. Computational fluid dynamics techniques for turbulent wind flow using Reynolds-averaged Navier–Stokes equations have been used to predict lift and drag coefficients on ground-mounted solar arrays with varied tilt angle and wind incidence. To effectively resist lift forces induced over the solar array, the foundation should be carefully designed with optimum pulling out capacity for precise lift forces determined using numerically obtained force coefficients.