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Minor project windbelt
1. Background
The world has become increasingly dependent on renewable energy sources such as solar, wind,
biogas etc. We chose to work on wind energy for this project. In this context, we focused on
developing a product that can generate electricity using the kinetic energy of the wind. All the
conventional wind mills have a simple phenomenon of doing the same. A typical wind mill has a
rotating device called “turbine” which rotates when wind flows over it. The shaft is coupled to a
dynamo and thus electricity is generated. This process sounds pretty good. But, when we try to
apply it on a small scale level, for example lighting a LED or charging a mobile phone etc., there are
a lot of problems involved. Rotation‐based wind turbines don’t scale down well due to friction and
he lower energy of lower wind speeds. So, there is a need to develop a new innovation which does t
not use rotary equipment, to achieve the required targets at the small scale.
By applying TRIZ techniques (TRIZ is a theory of inventive problem solving), one can easily say that
turbine is the part that is causing all the trouble. So, we simply eliminated it! Now, we need some
mechanism to capture the wind energy. After rotation, one can think of vibration. So, let there be a
membrane vibrating due to the wind. If we place magnets at its ends and make them oscillate in and
out of a copper coil, electricity can be produced! Shawn Frayne, an MIT graduate was the first
person to discover this idea and he created something called “Windbelt”. He started a company by
the name “Humdinger” which sells these Windbelts. Inspired by him, we tried out working on the
same principle in this course.
Windbelt Theory
Until recently, the only viable wind harvesting device was the turbine. Humdinger’s Windbelt is the
first non‐incremental innovation beyond this century‐old approach. Instead of using conventional
geared, rotating airfoils to pull energy from the wind, the Windbelt relies on an aerodynamic
phenomenon known as “aeroelastic flutter”. This phenomenon is a well‐known destructive force.
However, it can also be used as a powerful mechanism for catching the wind at scales and costs
beyond the reach of turbines. At its heart, The Windbelt uses a tensioned membrane undergoing a
flutter oscillation to pull energy from the wind.
To picture how this works, think of how you held a blade of grass between your fingers as a kid and
made it whistle—or how the strapping on a truck can be seen moving in the wind. That is roughly
how the Windbelt can pull energy from the wind—then, it’s a second step to turn that energy of the
moving membrane into electricity, which is done by actuating new types of linear generators.
2. The Tacoma Narrows Bridge callapse is a famous example of the destructive power of aero elastic
flutter. The bridge across Puget Sound opened on July 1, 1940. Four months later a strong
continuous wind induced oscillation into the structure, which showed torsional and longitudinal
flutter, eventually causing its collapse. The photos given below are stills from video footage of that
flutter and collapse. Structural engineers studied the failure; newer suspension bridges were built
differently to avoid such oscillation.
How does the Windbelt turn its “flutter” into electricity? A pair of magnets is fastened to the belt, so
as the belt moves up and down the magnets follow the same motion. This motion of the magnets
takes place directly next to the stator (coil). A magnetic field moving next to a coil of wire induces a
current to flow. As generated, the electricity is alternating current (AC). This AC may be converted
o direct current (DC) with the enclosed rectifier. t
Specifications
The Windbelt consists of a taut membrane made of Mylar coated Taffeta, 2 cap magnets, copper coil
and a frame to hold these equipment. Apart from this, it consists of an electrical unit that gives the
desired output power.
4. Cost Analysis
Rough cost of the project we carried out:
Object Quantity Dimensions Co `) st (
Belt 1 1 meter long 15
Wooden frame 1 Slightly longer than belt 25
Magnets 2 1cm diameter 60
Stator coils 2 ‐ 20
Miscellaneous (Nails,
adhesives etc.)
‐ Differe t sizes n 20
Total 140
Rough cost estimates of a final useful product:
Object Quantity Dimensions Co `) st (
Frame 1 1m x 5cm x 2cm 25
Belt 1 1m x 2cm 30
Magnets 4 80
Stator coils 4 30
Rectifier 1 ‐ 15
Nails, Nuts and Bolts ‐ Different sizes 10
Total 190
hus, a basic model of a wind belt costs less than `200 to manufacture. T
7. Advantages of a Windbelt
• The Windbelt is a light weight, low cost, portable, easy‐to‐use device.
• The 1 meter Windbelts are designed to work alone or in groups to provide power to
or any situation demanding 0.1 kWh to 1 kWh of lighting, WiFi nodes, micro‐base stations,
•
energy per month.
It can also be used for lighting bed lamps.
• a mobile A Windbelt can be kept on a moving car and the output can be used to charge
phone while travelling.
• A Windbelt can be placed on poles in high wind zones and used for street lighting.
• An array of Windbelts placed side by side can form a “Windcell” and it may be used to light
up an entire room!
The Windcell have a form factor similar to Solar panels and are designed for larger installations,
targeting applications with 5 kWh to several MWh of energy demand per month, with particular
attention to cost.
On larger installations, the Windcell panels have an initial projected production cost of Rs. 2.5 per
kWh (at 6m/s average wind speed).
Cost combined with modularity, safety and form factor gives the variation of the technology access
to many of the places that wind and solar cannot presently go.
9. Q: The belt is seems to be in torsion, and is generating very little output.
A: Measure the electrical output (if any) with a meter to have a comparison. Then flick the belt with
your finger. If that does not work, the belt tension can be varied with fingers. Try rotating the
indbelt so the air blows through from the other side. Torsional flutter often occurs when the belt
s incorrectly tensioned, misaligned on the bolts, or too close to the stator.
W
i
Q: Is it ok to hook up two or more units together to power a bigger load?
A: Yes, as long as they are hooked up in parallel (positive‐to‐positive, and negative‐to‐negative).
N
o
ote: If they are in series, the induced current from one Windbelt may flow through the coil of the
ther Windbelt, and potentially disrupt the induced current generation of that generator.
Q: Doe
A: No
s it matter if the Windbelt is horizontal or vertical when it is in front of the fan?
Q: What is the expected electrical output?
A: 10mW to100mW (milliWatts), depending on wind speed. At 6m/s wind speed, around 50mW is
delivered to the load. Voltage, unloaded, will be around 2‐3 volts AC before rectification.
Q: How does moving a magnet past a coil generate electricity?
A: This process is called electromagnetic induction
Q: At what frequency does the wind usually vibrate?
A: The 0.5 meter Windbelts will vibrate at around 70‐100 Hz. The 1 meter Windbelt vibrates at a
lower frequency: 20‐50 Hz range ideally. Frequency varies depending on belt thickness, belt
ension, wind speed etc. t
References
• en.wikipedia.org
• www.humdingerwind.com
• www.popularmechanics.com/science/energy/solarwind/4224763
• http://buildingstuffinthebasement.blogspot.com/2009/11/diy‐Windbelt‐with‐wood‐and‐duct‐
tape.html
• http://www.instructables.com/id/Windbelt‐from‐hard‐drive‐voice‐coil‐and‐magnets/