Second Wind

Project undertaken in course year 2017-2018 with the Dabiri Lab

Project Goal

Develop a VAWT blade that is capable of self-governing without sacrificing power or efficiency to improve reliability of existing VAWT technology

Project Motivation

Vertical Axis Wind Turbines (VAWTs) can

improve wind farm density
provide access to clean energy in rural communities / developing world
reduce maintenance costs

Background

Vertical axis wind turbines (VAWTs) are a potential key player in generating renewable energy.
A particular problem with VAWTs is their tendency to spin out of control at high wind speeds, throwing their support structure off balance, and in some cases damaging the turbine beyond repair

Failed VAWT blade

High Priority Requirements

Self-governing at wind speeds > 10m/s
Passive mechanism (no active control)
Generates 2 kW power
Easily integrates with existing turbines

Ethical Considerations

Prevent harm
Parts to not fail
Non-hazardous materials
Ensure validity of conclusions and repeatability of data

Solution

A VAWT blade with "feathers" on the leading edge of each blade. The feathers are made of fabric cut to thickness and width, and when the turbine is operating the fabric changes position from the underside of the blade to the topside of the blade based on wind conditions. The addition of these feathers limits the angular velocity at ranges of wind speeds tested from 7 to 15 m/s, while maintaining stable performance.

Model of the feathers, at small scale

Model showing thickness and width of various feather geometries

Test results at small scale, looking at effect of thickness and pitch on angular velocity of turbine. 2 and 4mil PE, at either pitch (0.5-1.0 in), shows improved reduction in angular velocity relative to control

Testing at full scale, fabric

Top view of full scale testing, 4mil ldpe

Bottom View, Testing with 4mil ldpe

Side view, testing with 4mil ldpe

Test results, Full scale

Test data from full scale testing, demonstrates that the fabric has a more pronounced effect on reducing angular velocity of the VAWT than do the plastic materials

Student team

Future Work

Research contines at Stanford

Further investigate data gathering inconsistencies at low rotational speeds
Further understand the relationship between materials and their effect on rotational speed
Optimize material and attachment mechanism

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