Proceedings of the 2004/2005 Spring
Multi-Disciplinary Engineering Design Conference
Kate Gleason College of Engineering
Rochester Institute of Technology
Rochester, New York 14623
May 13, 2005
Project Number: 05307
WIND SOLAR PROJECT
Joe Jachlewski – Team Leader,
Mechanical Engineering
Paul Kingsley,
Brian Nealis,
Mechanical Engineering
Mechanical Engineering
Pamela Snyder,
Mechanical Engineering
ABSTRACT
This paper details the development of an outdoor area
light system powered by the combination of a wind
turbine and solar panel. The goal of the project is to
establish an autonomous power system capable of
supporting the required power of the light and to study
the performance of the system’s components. This
paper will focus on the integration of the various
components into a functioning unit and the resulting
performance of the system as a whole.
Aaron Bailey,
Mechanical Engineering
Matt Rose,
Mechanical Engineering
Christopher Wall,
Mechanical Engineering
The purpose of the project is to utilize the advantages
of each and evaluate their contributions to the system
as a whole. The core concept for this system was first
detailed by Dr. Venkataraman in a proposal to the
New York Science Association (NYSA).
A consensus conclusion will be put here to
summarize our findings. Approx 100 words.
NOMENCLATURE
Depends on the level of equation work included.
SYSTEM DESIGN
INTRODUCTION
Over the last decade, public works projects have
shown a greater interest in utilizing “green” power for
their small load applications than in years passed.
This has included the addition of solar panels to area
lights and blinking warning lights. Wind power has
seen increased usage in large scale power production
with the construction of large wind farms composed of
large horizontal axis wind turbines. Vertical axis
turbines have seen limited development for small scale
application in hobby-type fields.
Each source of power, wind and solar, has its own
benefits and limitations. Solar power is dependable
and predictable. Wind power, rising cubically with
wind speed, is capable of high outputs at unpredictable
times. Solar power operates on a cycle following the
daylight hours, while a wind turbine is capable of
producing power at any hour.
The Wind Solar Senior Design Team designed an
area light during the 2004-2005 academic year that
incorporated both of these “green” energy sources.
The driving force behind the design of the energy
production system was the driven electrical load. The
light source chosen was a high intensity 120 LED
array designed to operate on 120V AC power available
through HighTechLighting.com. The power draw of
bulb was provided as 10 watts. Based on an electrical
system efficiency of 50%, a power generation system
capable of 20 watts was targeted.
Solar panels are available commercially in a
multitude of sizes. Their area relates directly to their
power capacity as panels are composed of strings of
small photovoltaic cells. It figures that any expected
contribution from the solar panel would directly
reduce the required contribution from the wind
turbine.
The wind turbine was a major focus of design
effort. Wind power available varies cubicly with wind
speed, and wind power harnessed varies directly with
the swept area of the turbine rotor. A minimum
efficiency for the mechanical power extracted from the
wind against the total power available was set at 15%.
© 2005 Rochester Institute of Technology
Proceedings of KGCOE 2005 Multi-Disciplinary Engineering Design Conference
This efficiency was arrived at following an
examination of available commercial designs as well
as theoretical mathematical limitations on performance
such as the Betz limit. The Betz limit states that,
because slowing the velocity of the wind during the
power extraction process decreases the mass flow of
air through the system, a optimum value exists where
the mass flow and energy extraction are balanced to
achieve the greatest possible power. This value is
59.3% of the available power in the wind[].
A design space was developed to aid in sizing a
rotor size. The power capacity of the solar panel was
used as the independent factor and the resulting rotor
swept area was determined. The average wind speed
in of any given month in the local Rochester
environment as well as the equivalent amount of
sunlight available and its duration was supplied by the
National Oceanic and Atmospheric Administration
database (NOAA.org)[].
Figure 1 - A plot of the rotor size design space.
Readily available commercial solar panels were
considered. A 10 watt panel was selected. A
minimum swept area for the turbine rotor of 1.17 m2
was found.
ROTOR DESIGN
Three core geometries were initially discussed for the
rotor geometry. These geometries were horizontal
axis, Darrieus vertical axis, and Savonius vertical axis.
A Savonius design was selected because of its greater
simplicity in construction.
Figure 2 - Simple Savonius geometry rotor. Top
view.
Page 2
The Savonius rotor uses stagnation pressure on one
side to promote rotation around a central vertical axis.
The blade turning into the wind redirects air around its
self with its rounded shape. This design generally
produces high torques and low rotational speeds
relative to other wind turbine geometries.
The specific rotor constructed in this project was
built using lightweight fiberglass with foam
reinforcement. The central shaft was a length of
schedule 80 PVC pipe that provided structural strength
and rigidity. A hollow center shaft allowed for the
rotor to spin around a stationary shaft of 2” diameter
aluminum. Each end of the hollow shaft was supported
by a thrust tapered roller bearing. Moments created by
wind incident on the rotor, then, were supported by the
stationary center shaft and not the bearings.
The designed rotor was 48” in diamter and 48” in
height, giving it a swept area of 1.49 m2, greater than
the required 1.17 m2.
At the minimum 15%
efficiency, this size rotor would put out 13.15 watts in
mechanical power when subjected to the Rochester
annual average wind speed of 4.58 m/s. Instead of one
rotor running the full 48” length, the rotor was broken
into 2 24” sections that were mounted at a 90 degree
offset. This allowed for the rotor to present a face to
the wind every 90 degrees instead of every 180
degrees. This cuts our peak torque in half, but
produces an identical average torque over a complete
rotation.
Additional, the likelihood of wind
approaching from any radial direction will produce
power is increased.
FEA Rotor Analysis by Brian
The rotor drives a permanent magnet DC motor
with a 1:1 ratio chain drive. The motor responds to
input rotational motion with a linearly increasing
voltage. Amperes drawn off the motor increase the
torgue required from the rotor. With the exception of
the teeth of the cogs and hardware, all the structural
and drivetrain part features were machined by the
team.
STRUCTURAL DESIGN
The rotor and generator assembly were mounted to the
top of a 16 foot long pressure treated wood post
measuring 5.5” x 5.5”. The post was planted 3 feet
into the ground in a 12” diameter concrete footing.
Additionally, four 5-gallon buckets were filled with
concrete along with a metal spiraled stake. These
buckets were buried in the ground 8 feet from the foot
of the post in each direction to provide anchors for
steel guy wires that were attached to the post at an
above ground height of 8 feet.
The solar panel was mounted 10 feet above ground
level with custom aluminum brackets and an 18” arm.
The brackets held the solar panel at a 45 degree angle
facing south. Rochester, NY, is at a latitude of 43
degrees, indicating that the peak of the sun’s path to
the south averages approximately 43 degrees above
horizontal. Given the rotation of the Earth and
Paper Number 05nnn
Proceedings of the Winter KGCOE Multi-Disciplinary Engineering Design Conference
change in rise of the sun with season, exactly
angling the solar panel was not possible.
The light fixture was also mounted at a 10’ above
ground height on the north side of the pole with an
inline light switch to control our power draw cycles.
The 12 V marine battery was housed in a
polycarbonate case at the base of the pole. The drive
train residing under the rotor was also encased using
polycarbonate and acrylic. Electrical lines running up
and down the post were run through conduit for
protection.
Figure 3 - Complete system model.
ELECTRICAL DESIGN
The solar panel and generator both produce DC
voltages. The solar panel voltage in full light can rise
as high as 13 volts. It was connected directly, then, to
a battery charge pump for a 12V battery capable of
charging with supplied voltages as low as 7V DC.
Due to the low design rotational speed of the rotor
and the low gear ratio in the chain drive of 1:1, the
voltage produced by the generator at general operating
conditions was on the order of 1.2-3 V DC. Directly,
this voltage was too low to supply an identical charge
pump. The voltage then, was passed through a pulse
width modulator to increase its voltage. Then, the
signal was passed through the circuit shown below to
produce a one way current into the charge pump.
Both charge pumps were then connected to the 12V
marine battery. The battery had a XXX watthour
capacity, capable of powering the light for YYY hours
on a full charge. Lines from the battery were then run
to a commercially available AC inverter. The inverter
powered the light.
Sensitive components were safeguarded with
quick-blow fuses.
DATA ACQUISITION
The data acquisition system (DAQ) was composed of
three primary areas: system voltage measurements,
system current measurements, and local weather
measurements.
The DAQ system was interfaced with a laptop
using three National Instruments USB based DAQ
devices and LabView 7.1. The devices are capable of
measuring voltages directly. The generator, battery,
solar panel, and light circuit voltages were then
measured simply by tapping into each end.
Current could be measured by measuring the
voltage drop across a small resistor in each circuit. 1
Ohm resistors were found to yield voltage drops for
measurement. The currents in the generator, battery,
solar panel, and light circuits was measured in this
manner.
A anemometer attached to the post with a 4 foot
length of PVC pipe was used to measure wind speed.
Page 3
A weather vane and solar sensor were also included.
Measurements from the weather vane, attached to an
encoder to report direction, were neglected as wind
direction does not vary vertical axis wind turbine
performance so long as the flow is horizontal. The
anemometer emitted a frequency with its rotation.
Prior to installation the response of the anemometer
was compared to a calibrated anemometer at identical
conditions to determine its response characteristics.
The resulting data yielded a linear calibration curve for
the response.
Solar measurements were only
collected to verify that the solar panel responded
linearly with light intensity. Include calibration
data for the anemometer? fairly unimportant.
RESULTS
This will be a fairly long section composed of some
graphs. Figures will include:
Generator Voltages Vs. Wind Speed
Rotor Speed Vs. Wind Speed
Wind Power Vs. Wind Speed –> Efficiency
Solar panel power Vs. Time
Maybe a composite power graph.
CONCLUSIONS
Numbers would help solidify this.
FUTURE WORK
The structure of the system allows for different rotors
to be attached. Initially, simple Savonius designs of
varying height to diameters can be tested and
evaluated. Should adequate funding become available,
the electrical efficiency of the system could be greatly
improved with a gearbox and generator pair designed
to run optimally at the nominal rotor rotational speed.
The DAQ system current measurements currently are
a source of noticeable power losses. A less invasive
method of measurement is desirable.
ACKNOWLEDGEMENTS
The Wind-Solar Team would like to thank their
mentor, Dr. Edward Hensel, whose input was
invaluable. Additionally, the team would like to thank
Dr. Venkataraman for providing the initial concept and
his continued input throughout the project. The team
received machining assistance from Dave Hathaway,
Steve Kosciol, and Rob XXXX in the RIT machine
shop. Installation was made possible by David Harris,
Josh XXX with the RIT Physical Plant. John Wellin
assisted greatly in the design of the DAQ system.
Electrical help was provided by Dr. Wayne Walter,
Dr. Daniel Phillips, and Dr. Vincent Amuso. Joel
Slavis from HighTechLighting??
Put acknowledgments here. Be sure to acknowledge
your sponsor or customer. You may acknowledge
other individuals who have helped your team
Copyright © 2005 by Rochester Institute of Technology
Proceedings of KGCOE 2005 Multi-Disciplinary Engineering Design Conference
throughout the course of the project. It is appropriate
to thank suppliers, technical support staff, and others
who
made
a
significant
contribution.
Acknowledgments may be made to individuals or
institutions not mentioned elsewhere in the paper who
have made an important contribution.
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