Nonbuilding and Special Structures
Solar energy has seen unprecedented growth across North America and around the world. As generation capacity from solar power plants is becoming a more critical part of the worldwide energy infrastructure, solar power plant reliability becomes increasingly important to protect investment and minimize risk. These large scale solar power plants consist of ground-mounted solar systems of both the fixed-tilt and tracking variety. The directionality factors affecting both types of systems with long rows are examined in this paper. These factors are analogous to the Kd factor in the ASCE 7 Standard. The wind tunnel data from a large, rigid model solar array are integrated with several representative local wind climate models to produce directionality factors for different segments within a fixed-tilt and tracking array. The local wind climate models are created from historical wind speed and direction data obtained from meteorological stations. For hurricane-prone regions, the historical wind data are augmented by modeled hurricane data generated through a Monte Carlo approach based on the same methodology used to determine the design wind speeds in the ASCE 7 Standard. Based on the historical (and hurricane, if applicable) wind data, the local wind climate model describes the strength and directionality of wind speeds for any return period of interest. As tracking systems are generally designed to go into a stow position during high winds, they have two design regimes with different return periods: strength and serviceability (or operational). The directionality factors in these two design regimes are presented and contrasted against the ones obtained for a fixed-tilt system in the same location, as well as the ASCE 7 value of 0.85. The potential benefits of installation-specific directionality factors are also discussed in this paper.