Rachel Koh

Graduated with PhD in Mechanical Engineering

Link to PhD dissertation: Bio-based Wind Turbine Blades: Renewable Energy Meets Sustainable Materials for Clean, Green Power

Rachel is a Pioneer Valley native who was pleased to return to Amherst in 2012 to begin her Ph. D. studies after attaining her B.S. at the University of Vermont. Her academic interests lie in renewable energy bio-based materials engineering. In addition to her academic pursuits, Rachel is also a singer with The Sweetest Key and Strike-A-Chord a-cappella groups and enjoys spending time outdoors.

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Fabricating angle-ply laminates

Project: A Bio-based Design of a 5MW-scale Wind Turbine Blade

Project Description:

The National Renewable Energy Laboratory has issued a call for “incremental innovations” in wind turbine technology which will drive the cost of wind power down in the years and decades to come. Wind energy is becoming increasingly cost-competitive with other sources of electricity, but further technological innovation will drive it to become a leading source of power in the United States.

Turbine blade materials must strike a delicate balance which aims to drive cost and weight of the blade down, and lifetime up. Fiberglass is used almost universally today because of its high strength and stiffness relative to its weight. Wood laminates would offer both substantial cost and weight reductions as compared with fiberglass. Although the strength and stiffness are lower, much of the load that the blade must support is a consequence of its own weight, so wood becomes more competitive when strength is normalized by density. For this reason, small-scale wooden wind turbine blades have met performance requirements for decades. However, with advances in both wood composites and other bio-based materials, it is time to look for their place in large-scale turbines.

The first phase of this research addresses mechanics of wood laminate materials. An experiment to evaluate the shear strength of an angle-ply wood laminate beam using the torsion test was developed and is currently in progress. Future research directions include the development of modeling tools which address some of the unique mechanical aspects of bio-based materials, as well as the integration of economic decision making and design optimization into design tools for high-performance composite structures.