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