Alternative energy sources are all the rage these days.
The sight of a windfarm or a field of solar panels may not conjure the same level of awe that they did a few decades ago, but that doesn’t mean there are no surprises left for sustainable energy.
Meet Windbeam: a micro generator that captures energy from wind speeds as low as two miles per hour.
How Does Windbeam Work?
The design is surprisingly simple. The generator consists of a beam suspended between two sets of springs housed in an outer frame. A combination of two phenomena—transverse galloping and vortex shedding—cause the beam to oscillate rapidly when it’s exposed to airflow.
The energy from that oscillation is harnessed using an electromagnetic inductor system that generates AC power. The resulting AC power can be rectified into DC, which can then be stored in a battery. Zephyr Energy Corporation is currently collaborating with Epec Engineered Technologies to develop the battery storage technology for the Windbeam.
A notable advantage of this design, particularly when compared to traditional wind turbines, is the Windbeam’s lack of bearings and gears, which eliminates frictional inefficiencies as well as noise.
A Refresher on Transverse Galloping and Vortex Shedding
In case it’s been a while since your last course on fluid dynamics, transverse galloping is the progressively increasing amplitude of transverse vibration that occurs in response to increased wind speed.
In the case of the Windbeam, wind flowing over the beam forms a pressure differential and the beam’s non-circular cross-section produces an angle between the direction of wind flow and the force exerted on the beam.
This force initially pushes the beam upwards until the constraints of the system, i.e., the springs and the frame, force it back downwards. The same wind then produces an opposite pressure differential that encourages the beam to move in a downward motion. This pattern continues, resulting in a self-excited system.
Vortex shedding also contributes to the beam’s oscillations, but to a lesser degree. This phenomenon consists of the formation of alternating vortices that from behind the beam when it is placed in fluid flow. A lift force acts on the beam as these vortices are shed at an intensity directly related to the cross-sectional shape and size of the beam. When the vortices are large enough, they create a low-pressure zone toward which the beam is drawn.
How Much Power Does Windbeam Generate?
Once you get past the ingenuity of the design, the most obvious questions to ask about Windbeam concern its power output.
“At first, we started scaling the system up to see how we could compete with micro wind turbines, and we came up to the size of a 30-inch-length Windbeam which was generating around 3 watts or so, which isn’t a tremendous amount of power,” said Thomas Olsen, president and founder of Zephyr Energy Corporation.
“At that point, we pivoted and started playing toward the strengths of this novel design: it’s silent, it’s low-cost and it can operate at low wind speeds. We actually started scaling the system down to meet the needs of Internet of Things applications like sensors and HVAC actuators,” Olsen continued.
“As we scale down to the size of a six-inch Windbeam, we’re looking at power output from zero to ten milliwatts or so, but it’s a scalable platform technology, so it can be scaled according to the constraints of the environment of use or typical airflow speed,” Olsen concluded.
For a handy reference point on Windbeam size versus power output, see the chart below:
Although the cost-per-watt of Windbeam varies by application, the simplicity of the design is a major factor in keeping cost of the generators low.
“A lot of the components are off-the-shelf: springs, button magnets, small coils and formed pieces of plastic. There’s nothing exotic that requires special manufacturing processes,” said Olsen.
Applications for Windbeam
The scalability of the Windbeam makes it suitable for a host of applications, the most obvious being in heating, ventilation and air conditioning (HVAC).
“The major application right now is in smart building and IoT technologies: companies that are working on putting sensors and actuators into HVAC ducts to get a better sense of the airflow or air quality inside buildings,” said Olsen.
“By using dampers, you can zone the building, which is especially useful in older buildings that aren’t as energy-efficient. Instead of just running off a battery with a limited lifespan or going through the expense of trying to hardwire those dampers, you can use energy harvesting to capture some energy from the air flow already passing through the ducts to keep the batteries trickle-charged,” Olsen said.
The chart and graph below should give you a sense of the power output from such a setup:
Aside from powering dampers and actuators in an HVAC system, installing Windbeams throughout a building can both increase its efficiency by recovering energy that would otherwise be lost and be used to provide power to sensor networks.
“Say you have an exhaust vent with airflow being pumped out of the building,” Olsen explained. “The idea is to capture some of that energy and put it to use. That gives you the ability to power dampers and airflow handlers or sensors in a way that makes the building as a whole more energy efficient.”
Although the units are not in mass production, they can be custom built to suit the needs of, for example, a particular HVAC application.
“The key pieces of information we need are the physical constraints. If you’re talking about a duct, what size are you designing your system around? That would dictate the size of the Windbeam,” said Olsen. “Knowing the typical airflow range is also helpful. Although this works over a wide range, it can be tuned to operate more efficiently in a tighter band. We’d also need to know what your energy needs are and the duty cycle of the sensor or actuator.”
Beyond HVAC, there are several other immediately apparent applications for Windbeam. The technology is modular, allowing the generators to be stacked together to form an array.
From a military standpoint, consider the value of being able to drop a self-powered transmitter on top of a mountain in a hostile country. In fact, Windbeam has its origins in military applications.
“The reason why this technology was created in the first place was in response to a Department of Defence RFP looking for an inconspicuous alternative to a wind turbine at a forward operating base,” said Olsen. “They said that wind turbines interfere with their radar equipment and they’re rather obvious as targets.”
On a more positive note, the micro generators can also be used in developing regions that lack reliable, low-cost sources of power. For example, scaling the generators up to window-sized units could give residents of apartment buildings the ability to charge mobile devices or power low-wattage electric lights.
Other potential applications for Windbeam include:
- Weather stations
- Broadcast towers
- Disaster relief
- Emergency lighting
- Recharging batteries in personal electronics
Do you have another idea for a possible application?
Contact Zephyr Energy or visit the company website for more information.
Zephyr Energy has sponsored this post. It had no editorial input into this post. All opinions are mine. --Ian Wright