The mission of Energy Grade is to provide outdoor enthusiasts with an alternative and better solution to the present problem of not having electrical energy while in the great outdoors. We strive to no longer have stranded backpackers unable to signal for help due to a lack of cell phone power. Additionally, lost hikers unable to find their way home because of dead GPS units will be a thing of the past. We will also aim to eliminate the devastating feeling of not being able to take the “perfect picture” on top of a 10,000ft mountain because your camera or cell phone battery has run dry. Life’s a rocky journey. Energy Grade’s here to help you climb those rocks.
Electrical power is a little bit like the air you breathe! It’s seemingly always there and isn’t really thought about until it’s missing. Most people are used to electricity being available wherever they go. The lack of electrical energy in the great outdoors is a problem for hikers and backpackers using portable electronic devices (i.e. cell phones, GPS devices) over long periods of time, because these devices are constantly consuming power.
The NV Power Pole was created by Energy Grade to access electricity while away from a power grid. It is a portable, lightweight, energy generating device that hikers and backpackers alike can carry with them on a routine basis. A charging system will be integrated into the body of a hiking pole to capture the pole’s dissipated (and usually wasted) kinetic energy, and convert it into electrical energy. To accomplish this conversion from kinetic to electrical energy, a Faraday Inductive Generator was used in the NV Power Pole. The generator is mounted in the handle and upper body of the pole. As the pole strikes the ground, linear movement of the magnet between a series of coils produces an AC Voltage that is then manipulated by a circuit to charge the on-board battery.
How it Works
1. The oscillatory motion of hiking is where the whole process begins for the NV Power Pole. The magnet assembly with springs attached at either end of a Lexan tube was built into the body of the pole. The springs were chosen based on the mass of the magnets so that the frequency at which a person hikes causes the magnet to oscillate at resonance. A series of copper coils wraps around this Lexan tube above the magnet’s rest position. The movement of the magnets through these coils produces a voltage.
2. The voltage is produced from the magnet-spring, coil assembly inside the NV Power Pole. This voltage resembles an AC sinusoidal signal. To charge the on-board battery, the signal must be converted into a smooth DC signal.
3. A four diode rectifying bridge is connected to the ends of the copper coils. This takes the AC signal, which oscillates from negative and positive voltages, and outputs a purely positive signal. Or in other words, the diode bridge rectifies the signal from AC to pulsed DC.
4. The voltage signal after being converted into pulsed DC from the diode bridge. While the signal is now purely positive, the on-board battery still requires a smoother input to properly charge.
5. To smooth out the DC pulse output from the diode bride, capacitors are placed across the negative and positive terminals of the rectifying circuit. These capacitors are used to stabilize the changing voltage signal, providing a DC-like voltage that can be used to charge the battery.
6. The final output voltage from the generator after being manipulated by the diode bridge and smoothed out with capacitors. This is the input voltage for the battery charging circuit.
7. The charging circuit provided with the DC voltage signal. This circuit takes the input and safely charges the on-board battery at a rate of 100mA. The Minty Boost (a portable USB charging circuit) is also wired to this on-board battery, awaiting an electronic device to be connected via the USB port located at the top of the handle of the NV Power Pole.
8. The on-board battery can now recharge your mobile device. The amount of energy available is proportional to the time spent hiking with the NV Power Pole.
Faraday Inductive Generator
To accomplish the task of generating electrical energy from the NV Power Pole, a Faraday Inductive Generator was constructed to fit in the upper portion of the the hiking pole. The concept of the Inductive Generator, based on Faraday’s Law of Induction published by Michael Faraday in 1831, states that “the magnitude of EMF induced in a circuit is proportional to the rate of change of the magnetic flux that cuts across the circuit.” The generator is made up of a series of coil windings forming a path that allows a magnet to cycle through the coils. The motion of the magnet provides a varying magnetic field within the system that induces an electromotive force in the coils that in turn allows electrical energy to be harvested from the ends of the coil arrangement.
The most important variable considered by Energy Grade when designing the Faraday Inductive Generator was the time that it took the magnet to pass through the copper coils. Knowing that a high velocity of the magnet is required to increase the output voltage, a spring-mass system was used to move the magnet through the copper coils. The spring-mass system is designed to resonate at an input frequency that is most often experienced by the system, that being the approximate frequency at which a person hikes (1-2Hz). Two springs run lengthwise in the body of the pole connected to opposite sides of the magnet.
The voltage output by the Faraday Inductive Generator will not only be directly related to the velocity of the passing magnets (as stated earlier), but also the strength of the magnets, cross-sectional area of the coils they run through, and the number of coil windings.
A USB/DC Lithium/Polymer battery charger was used to transfer the energy generated by the Faraday Inductive Generator to the system’s on board battery. The charger will require a minimum of 100mA and a voltage from 5-12V.
An additional circuit board called the Minty Boost, was used to transfer energy from the on board battery to portable electronic devices.
A Universal Serial Bus (USB) 2.0 cable will be used to transfer the generated electrical energy because it is the industry standard for charging many electronic devices. The USB has a constant transfer rate of 500mA at 5V and is capable of handling 2.5W. The 500mA rating of the USB 2.0 allows the average smart phone with a 1500mAh battery to be fully charged in approximately 3 hours. Therefore, the power generated by the pole on an 8 hour hike should average approximately 0.35W (ideally).
Handle and Connector Assembly
Handle Body: The body of the handle has been made hollow to allow all of the systems electrical components to conveniently fit inside. The top of the handle has two USB ports for charging electronic devices and the internal battery of the pole.
Handle Connector: This is the part connecting the handle and the generator section of the NV Power Pole.
Bottom Connector: This is the connector used between the generator and the lower, adjustable half of the pole.
The NV Power Pole contains four main electrical components: Diode Rectifier, Battery Charger, Battery Pack, and Minty Boost.
Diode Rectifier: This electronic rectifier converts AC voltage input created by the generator, to DC voltage output that can be used to charge electronic devices. The generator produces a pulse voltage signal, thus in order to maintain a higher RMS Voltage signal to the charging circuit, capacitors were added to the circuit following the rectifier.
Battery Charger: A charging circuit board made by Adafruit Industries was selected to transfer energy to and from the battery. The charger accepts a voltage between 5 and 12 Volts and can charge a battery at a rate between 100 and 1200mA. Also the circuit board allows the user to charge the internal battery of the pole with an external power supply such as an outlet or charging device via USB connection.
Battery: A 1300mAh 3.7V Lithium Polymer battery is used to store the harvested energy. The Lithium Polymer battery was selected because of its high energy density and minimal loss of energy between charging and discharging cycles. When compared to other batteries, Lipo batteries are usually more compact and lightweight.
Minty Boost: A portable electronic charging circuit made by Adafruit Industries was selected to discharge energy from the internal battery. This small circuit board provides the ability to charge electronic devices via USB connection. The device is set to provide a constant 500mA at 5V which can be used for most modern electronic devices.
A series of cylindrical magnets and low friction Delrin washers are placed over a 1/8 inch length of all-thread. The assembly is secured over the rod by custom made brass nuts with attachment points for a tension spring on either end.
A Faraday Inductive Generator is used to harvest kinetic energy provided by the user to the NV Power Pole. The generator assembly is comprised of a magnet assembly oscillating through a polycarbonate tube. The magnet assembly is suspended in the center of the tube by a spring mounted on either end. Energy is generated when the magnet passes through the copper coils on the outside of the tube. The motion of the magnet is a result of the user’s hiking motion input to the pole.
The hiking pole is adjustable for a variety of users ranging from five to six feet tall. The pole can also be folded in half for easy storage via a bungee cord placed between the lower half of the pole and the lower connector.
Testing and Results
Testing: Hiking with the NV Power Pole was simulated by attaching the upper body of the pole to a shake table. It was then supplied with a linear displacement at a rate equal to the generator’s natural frequency. A series of discharged battery packs were provided with power from the generator over different lengths of time. These batteries were then used to charge a phone; its initial and final battery percentages after charging were compared.
Results: The theoretical charging rate was based on the assumption that the batteries were supplied with the charging circuits rating of 100mA. The batteries were charged by a pulse signal because the generator was not capable of outputting energy at a rate high enough to constantly run the charging circuit. The output was 100mA for approximately 25% of the operating time.
ABOUT THE TEAM
Energy Grade was formed by a group of friends in a Mechanical Engineering senior design class at the University of Nevada, Reno. Each student came from a diverse background with different life experiences that taught each of them how to think ingeniously. Additionally, the importance of renewable energy and love of the great outdoors was a common driving factor between the five students. These commonalities lead to the creation of Energy Grade’s first product, the NV Power Pole.
William Dorough: William is currently working as a manufacturing engineer intern. This experience gives him the ability to manage and improve the project, as well as minimizing its cost. He works with a variety of individuals including engineers, machinists, purchasing personals, quality control representatives and vendors. He is also working as a field technician at a local casino, giving him hands-on job experience that was useful for fabrication. William plans on working as a Junior Engineer at a local mineral company after earning his Bachelor’s Degree. He also plans on simultaneously pursuing a Master’s Degree in Business Administration at the University of Nevada, Reno.
Ernesto Triton Manzo: Triton is currently a undergraduate research assistant for Dr. Miles Greiner focusing on bench-marking CFD simulations for nuclear safety. Triton plans on continuing this work under Dr. Greiner while attending graduate school at the University of Nevada, Reno. He previously was a technical intern at a local geothermal power plant. Working with other engineers has improved his teamwork and communication skills. He has also worked with maintenance crews, observing engineering problems in the field.
Jack McCormack: Jack is currently working as a Research and Development intern at a local company. This experience helps ensure designs are up to date and well documented. He has worked in the automotive industry as a mechanic over the last nine years. Though he is not currently a mechanic, years of experience in the profession have left him with exceptional hands-on capabilities. Jack has been accepted into the Master’s of Business Administration program at the University of Nevada, Reno and will begin coursework this fall.
Jennifer Mello: Jennifer currently works as a supplemental instructor and grader for a freshman level engineering course at the University of Nevada, Reno for Dr. Eric Wang. She has spent the past seven summers working at a summer camp held on the University of Nevada, Reno’s campus, her children wrestling skills improved her ability to manage the other members of Energy Grade. More importantly, her past experiences have taught her the importance of working on a team and the value of one’s opinion. She was also on the newspaper staff of her high school where she learned the importance of design, layout, and professionalism. Jennifer is currently pursuing a dual degree: a Bachelor’s Degree in Mechanical Engineering and a Master’s Degree in Business Administration from the University of Nevada, Reno.
William Nagel: William is currently working as a research assistant for Dr. Eric Wang at the University of Nevada, Reno. He also serves as a supplemental instructor for a freshman level engineering course, also instructed by Dr. Eric Wang. His experiences working in a research environment and aiding lower level students has given him a good understanding of the engineering method and how to apply it. William has been accepted into the Mechanical Engineering graduate program at the University of Nevada, Reno, and plans to begin coursework this summer.