Design of a Resonant Wind Engine

Design Team:Rex Oldford - Leader

Douglas Pittman

John Savage

Barry Sullivan

Faculty Advisor: Dr. M. Hinchey

The design project is a research and development exploration of the viability of extracting electrical energy from a resonating member driven by the wind.

Have you ever stopped to watch a street light pole vibrating in the wind? If there is some way of harnessing the energy in a vibrating member and using it to produce electricity, the result would be an inexpensive and simple generator which requires minimum space and maintenance. We call our future design a “Resonant Wind Engine” because it uses wind to create useable power.

The design team began by researching the effects of wind on slender structures. Several case studies have been done on the wind induced “resonance “ phenomenon including the Tacoma Narrows Bridge, famous to all engineers. These case studies are geared to eliminating the effect since it is destructive in civil structures such as bridges, smoke stacks, communication towers, and tall buildings. There are many case studies based on similar effects in water such as buoys used for current speed sensing. While these studies are geared towards eliminating the resonating condition, we are interested in initiating and sustaining the resonant motion.

Several problems must be dealt with to accomplish a workable design. The design must function in varying wind speed conditions and either be immune to or account for gusting and swinging wind direction conditions. The member must be constructed of a material which can be subjected to continuous vibration for extended periods without fatigue problems. A resonating member excited by a forcing frequency very near the member’s natural frequency will vibrate with increasing amplitude to the member’s destruction. Therefore, some means of damping must be incorporated into the design. A generator must be designed to convert alternating, as opposed to rotating, motion into electricity. Determining the cross sectional shape of the member such that it initiates resonant motion also poses a challenge to the design team.

Concept designs have been identified by the team members through brainstorming sessions and group discussion. The design team is currently evaluating the concept designs and developing others. The project is concentrating on resonating members as opposed to fluttering members. Therefore, the concept designs are based on a resonating member configuration.

Upon selection of the most promising concept design, the team intends to develop a mathematical model to determine parameters such as height, mass, stiffness, etc. A workable cross section is to be determined by testing shapes on a flow table.

Design work during term 7 is to be followed in term 8 by the building of a scale prototype for wind tunnel testing and evaluation.