Transcript IMETI_VAWT - Georgia Institute of Technology

Prediction and Validation of a Micro Wind Turbine for
Rural Family Use
Narayanan Komerath
School of Aerospace Engineering, Georgia Institute of Technology,
Atlanta, GA 30332, USA
Padma Komerath
SCV Inc, Johns Creek, GA 30022, USA
IMETI 2011, Orlando, FL June 2011
ACKNOWLEDGEMENTS
The work reported in this paper was made possible by resources being
developed for the “EXTROVERT” cross-disciplinary learning project
under NASA Grant NNX09AF67G S01. Mr. Anthony Springer is the
Technical Monitor.
Points Made
A simple self-starting vertical axis turbine design has been demonstrated.
Figure of merit of small vertical axis wind turbines is low.
Measured power levels are low, but these are justified by the cost of alternatives at
these low power levels.
Double-bladed turbine design is effective where blade cost is low.
Flexible-blade designs are fairly effective for the 1m turbine in the 100 watt regime,
but are inadequate for a 2m version of the design at any power level, due to flutter
issues.
Momentum and Blade element theory predictions show that high rotational speeds
are required to obtain good figure of merit where the turbine radius is small.
Need high solidity to bring optimal tip speed ratio down.
Outline
•Design philosophy, requirements and constraints:
Inexpensive blades suitable for cottage industry
Rotating parts from bicycles.
Development steps:
• construction, static testing measurement of performance.
•Numerical simulation issues.
•Moderate success with 1m diameter, 1 meter tall turbine
using inexpensive and commonly available materials and
construction techniques
•Yawed biplane blade design with Savonius and Darreus
features.
•A 2m x 2m design scaled up from the 1meter machine;
Failure with flexible design.
•New design with stronger blade construction being
developed.
Initial Bicycle Wind Turbine Concept
4-Arm 1m VAWT with straight cambered-vane double
blades and guidevane starter.
3-Arm 2m VAWT with straight cambered-vane
double blades and Savonius starter.
Yawed bi-blade 1m self-starting vertical axis
wind turbine: PVC pipe construction
Static Test Results:Choice of CPVC pipe vs. PVC pipe
and wooden rod for main blade spar
Centrifuge effect on blades
Strobe-lit snapshot of the 3-armed VAWT in operation.
Blue guidevane visible to the left.
Steel tube/ wooden rib/foam/fiberglass/ blades for 1KW turbine
54-inch Horizontal Axis Wind Turbine
Electrical Output vs. Wind Speed, with 50 Ohm resistive load (2 tests)
Aspect Ratio Effect on Optimal Tip Speed Ratio
Blade element predictions
of the mechanical power
output of the 3-armed, bibladed VAWT, for different
choices of blade chord
compared to the baseline
chord, with fixed span
Measured VAWT mechanical power in two tests vs.
preliminary predictions from momentum streamtube
theory.
Conclusions
The philosophy behind the design of small, low-cost vertical axis wind
turbines for family use is explained, and leads to a design where blades are
inexpensive and the rotating parts come from bicycles. The measured power
levels are low, but these are justified by the cost of alternatives at these low
power levels. Specific conclusions:
1.
The figure of merit of small vertical axis wind turbines is low.
2.
A double-bladed turbine design is effective where blade cost is low.
3.
Flexible-blade designs are fairly effective for the 1m turbine in the
100 watt regime, but are inadequate for a 2m version of the design at any
power level, due to flutter issues.
4.
Blade element theoretical predictions of the power show that high
rotational speeds are required to obtain good figure of merit where the
turbine radius is small.
5.
A simple self-starting vertical axis turbine design has been
demonstrated.