Anna Craig is a PhD candidate in the Department of Mechanical Engineering at Stanford University. Working under Professor Jeffrey Koseff of the Department of Civil and Environmental Engineering and in collaboration with Professor John Dabiri of Caltech, her research approaches wind energy from a relatively new perspective: instead of focusing on large horizontal axis wind turbines (HAWTs) which are designed to operate in isolation with high individual efficiency, she focuses on much smaller vertical axis wind turbines (VAWTs) which have lower individual efficiency but which can placed in closer proximity to each other. It is a shift from considering power output per unit turbine to considering power output per unit land area and preliminary demonstrations with small numbers of VAWTs have indicated a potential order of magnitude performance improvement in this metric over HAWT arrays.
One key to making VAWT arrays viable, however, is to fully understand the interactions between individual turbines and the development of the wind flow as it passes through a large array; these factors determine the energy resource available to individual turbines within the array and therefore the performance of the array as a whole. In order to begin studying this problem, Anna has designed and built a geometrically scaled model array consisting of 300 rotating elements which mimic a possible real-life VAWT array. By varying the element rotation rate, rotational configuration, and geometric configuration, she is working to determine what parameters most effect the flow development and how these parameters might be used to optimize a VAWT array for increased performance.
Anna's interest in VAWT arrays began as an undergraduate at the California Institute of Technology. Her undergraduate thesis, "Low-Order Modeling of Vertical Axis Wind Turbine Arrays,'' was conducted under Professor John Dabiri and focused on rapid numerical optimization of the flow field in medium-sized arrays of VAWTs. Anna graduated with honors in 2012, receiving a Bachelors of Science in Applied Physics, with a minor in Aerospace Engineering.