VAWT is (the new) HAWT

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

Project Goal

Design lower cost turbine blades to reduce the lifecycle cost of VAWTs in Igiugig, Alaska in order to promote a viable, clean alternative to diesel fuel in the winter

Project Motivation

Protect the environment by reducing CO2 emissions associated with the use of diesel generators in Igiugig, Alaska, while making clean energy technology more accessible from an economic perspective

Background

Vertical Axis Wind Turbines (VAWTs) allow increased energy density when positioned in arrays, relative to horizontal axis wind turbines (HAWTs)
Alaska is the 3rd highest generator of CO2 per capita in the US, largely from use of diesel generators in the winter time
Cost of delivering diesel to remote locations in the winter is high
Fabric blades could reduce cost of delivering turbines to Igiugig dramatically, but they have been shown to stretch and lose shape quickly, reducing performance

Fabric blades that deform over time, losing performance

High Priority Requirements

Reduce cost below $1000/blade
Prevent fabric deformation to less than 3" to avoid excessive deflection
Operate for a winter season without need for maintenance

Ethical Considerations

Prevent financial, physical, environmental and social harm
Stay consistent with local values for materials, accessibility, and culture

Solution

Fabricating the blade out of Dyneema fabric, with an aluminum central structure with a single rib support for the fabric, meets the overall objectives of lowering capital cost of a VAWT in comparison to conventional aluminum VAWT blades, and would not require re-tensioning during an operating winter season in Igiugig, Alaska

Full-sized prototype of a single blade after it has been wrapped with Dyneema

A view of the end-piece, how it shapes the fabric blade

The end-piece is fixed onto the internal structure with two pins

full-size prototype of a single blade without the fabric wrapping

Strain energy testing

After testing various materials at different temperatures, Dyneema was determined to be the best choice as it required the greatest strain energy (tear resistance) with a given displacement at cold temperatures

Relaxation testing

When creating fabric turbine blades, it is important to keep the fabric taut over time, to maintain an airfoil geometry. However, fabrics relax with increased tensile loads. These results show the different tensions maintained over time.

Deformation of fabric vs tension

Evaluation assessing the deformation of the fabric under wind-load as a function of the span of the fabric. To ensure the deformation remained below 3 in, and for wind-loading expected up to 240N, 1 central support rib was required in the blade structure

Deformation of fabric vs time

Having selected the 1-rib support structure, this evaluation looked at the relaxation of the fabric under cyclic loading to confirm that deformation remains below 3 inches over the season

Working

carefully assembling the system

Working?

Relaxing next to the blade structure

Student team

Student team shown with full-size prototype

Future Work

Fabricate multiple blades for testing at Lancaster Wind Farm
Finite Element Analysis on structural elements
Additional cost reduciton strategies

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