By Scott Beressers
Research interest include: wind and vibration energy harvesting, piezoelectric and magnetoelectric non-linear effects, drivetrains, biomimetic airfoil design, induction machine design, and continuum fluid dynamics.
Current projects include:
“Contact-less” Piezoelectric Wind Turbine
Conventional wind turbines rely on electromagnetic generators for electro-mechanical energy conversion. While electromagnetic generators are highly matured and efficient for larger-scale power generation, they are limited by several factors including high cogging torque and high rotational speeds. In low altitudes (below 50 ft from ground) and in areas with low average wind speeds, conventional wind turbines are not able to operate consistently at high rotational speeds. Hence, piezoelectric materials have explored as a low-torque, low-rotaional speed alternative for electro-mechanical energy conversion in wind turbines. In the case of small-scale (blade swept area below 5 in2) wind turbines, the more continuous operation from using piezoelectric materials can offset the corresponding decrease in efficiency from switching away from electromangetic generators. In the “contact-less” wind turbine concept, the effectiveness of using piezoelectric materials is increased by using alternating-poled, permanent magnets to excite the piezoelectric materials; hence, there are no frictional losses from contact between some mechanical actuator and the piezo’s. The efficiency of wind turbine configuration can be further increased through performing detailed blade design, using high “d31” piezoelectric materials, and designing for resonance.
Residential, Duct-Augmented Wind Turbine
The third research area being investigated in wind energy harvesting is a “middle-scale”, duct-augmented wind turbine for use in residential areas. While using these “middle-scale” (often referred to as “small-scale” within the wind turbine industry) are not a new area of research, there has been an increased interest in alternative energy solutions for the average consumer. Unfortunately, there are number of issues with residential wind turbines that push consumers to look towards solar as an alternative. Among these are excesive noise and limited usability due to low wind speeds. It was, therefore, determined that the use of a duct or “shroud” placed circumferentially, around the blade rotor may not only reduce noise and lower cut-in wind speed, but also improve the overall performance of the turbine. While such a duct may be infeasible on the full-sized, industrial models, the relative cost of the duct compared to the traditional components of a residential wind turbine is greatly reduced. Thus far, our investigations have included basic CFD evaluations of the duct design, the use of a multi-stage rotor, and the implementation of a direct-drive generator. The overall goal is to provide a wind turbine capable of producing 1-10 W of power at a cut-in wind speed of 3-5 mph.