Power Generation Pack

Transcription

1 Power Generation Pack Louis Reid Peter Iannaco Kirstin Torento Matthew Garland Wentworth Institute of Technology Department of Mechanical Engineering and Technology Mechanical Engineering Technology Prepared for Professor Richard Roberts Special Topics in Engineering Technology Submitted April 29, 2011

2 Table of Contents Abstract... 2 Introduction... 3 Objective... 4 Background Research... 4 Budget... 7 Table 1.0 Budget and Time Allotment... 7 Table 2.0 Itemized Report... 8 Sample Calculations... 9 Calculation 1.0 (Electrical to Mechanical Power)... 9 Calculation 2.0 (Hooke s Law & Newton s Second Law)... 9 Calculation 3.0 (Two springs connected by one mass)...10 Calculation 4.0 (Two Springs in Parallel)...11 Procedure Data Results Discussion of Results Conclusion References Appendix (Drawings) WIT Abstract 1

3 Abstract Electronic devices have become essential to daily life. They offer a multitude of great features and tools and currently have only one major drawback; battery life. Most modern smart phones have a battery life between 4 and 6 hours with constant talk and web browsing time; with the advent of apps the battery suffers yet another source of constant draw. Laptops, which use even more power, have an even more limited battery life. The majority of people carry some type of bag around; whether it s a purse, backpack or briefcase, and as humans walk, their bodies move in a repetitive motion. This can be mathematically represented as a frequency. This frequency can then be translated into a linear motion and then converted into electrical power. The solution to this problem is a unique stand-alone device that can be placed in a person s bag that uses their natural frequency to charge an electronic device such as a phone or laptop. WIT Abstract 2

4 Introduction The current life of an American revolves around technology. MP3 players, laptops, cell phones and other mobile electronics are becoming essential to everyday life. Power hungry Smartphone s in particular have become very common. Because Smartphone s are more powerful and have a wider range of uses than the traditional cell phones, they receive more hours of use. The short battery life and high importance of these smart phones creates a serious need for a mobile charging solution. Humans exert a usable amount of kinetic energy on a daily basis through everyday actions (i.e. walking). This mechanical energy could be harnessed with a mechanism and then converted to electricity. This electricity could be used to provide the necessary charging power to smart phones. Many people use backpacks; students carry them everywhere they go, and it is common to see the average working adult carrying one as well. Since the backpack is a common accessory between people and has a decent volume, it would be ideal to use the backpack as housing for an energy creation device. The proposed project idea is to create self-contained mechanism for kinetic energy recovery that converts mechanical energy produced by natural movement into electrical energy. This system will be small and light enough to comfortably be carried by the user on or in their backpack. The projected goal is to create a device that can conveniently charge a Smartphone while the user is in an area where traditional charging is not available. WIT Introduction 3

5 Objective The objective of this project is to create a mechanical device that efficiently harnesses the kinetic energy of walking. This will be completed in multiple steps. First it will require researching the field of physics; specifically frequency and vibration to find applicable concept(s) to apply to our problem. These concepts will be used to create physical working models; we will test and refine these models, both physically and theoretically through the use of Solidworks and other tools to produce an efficient, physical, and conceptual device. The intent of this project is to learn about and research the fields of energy recovery, vibration, and frequency. We will spend a large amount of our time; developing theory, designing the test devices on paper and or computer, building them, and finally testing with them. Background Research From a census taken in 2010 there are approximately forty five million people in the United States that own a Smartphone; a Smartphone being a cellular phone with personal digital assistant (PDA) like capabilities. That represents about a sixth of the percentage of cell phone subscribers considering nine out of ten people in the United States own a cell phone. The main reason to own a Smartphone other than the growing trend is because you need the computing capability on the go. This unfortunately leads to one of the biggest problems which are the battery life. Most Smartphone s battery last for around four to six hours with just continuous talk time (see Graph 1.0). This raises a need an ever growing need for power on the go. WIT Objective 4

6 Graph Battery Life Chart with average There are many devices on the market today to generate power without the need of an electrical outlet. These generators are found in applications that require little power like flashlights, especially those that use light emitting diodes. They have also been used in radios and other applications. There are several types of these generators which all operate based on different motions and systems. Some of these systems include a hand cranked and squeeze powered generator which operate by turning a series of gears ultimately to spin a larger flywheel in turn spinning a small generator. Another popular mechanism incorporates a magnet and a coil of wire. As mechanism is shaken the magnet passes back and forth through the coils creating a charge. A rectifier is used to reverse the charge on the magnets return pass through the coil. Another system which is used primarily in watches is a small weight that is on a pendulum and as a person swings their arm the weight spins 360 degrees and winds the watch. Also, a spring mass system has been utilized to acquire energy in order to create electrical power. There are also some devices that use piezo electric devices like in children s WIT Background Research 5

7 shoes to get them to light up. Some of these devices require movement which isn t natural to a human well others however do. Humans have a natural frequency when they walk. Assuming the average human walking speed is three meter s per second that translates to about 120 steps per minute for a frequency of two hertz. The frequency of a person can change slightly due to physical characteristics, layout and condition of the terrain, and even the mood of a person. People have some distinct movements as they travel. There is a constant swing from the arms and legs as a person steps as well as a vertical displacement. Most people displace about two to two and a half inches in the hips with each step. This up and down motion is something that is repeated and utilizing it would not impede a person. Since Smartphone s are used for on the go needs it is safe to assume that a majority of people using them are on the go a lot like students and working professionals, most of who carry a bag or pack with them. This makes for a large space to utilize having a device. In 2005, a research at the University of Pennsylvania, Lawrence Rome, developed a backpack that operates with a suspended load between a set of springs that can travel about four to five inches. As the device moved up and down it spun a generator and was able to produce seven and a half watts of electricity. Some downfalls to this were that it weighed 13 pounds by itself and only produced that much power with a load of 45 to 85 pounds which isn t very discrete. Rome s design produced about 300 times what the shoes with the piezo electric would produce. Rome s idea was very innovative but not very practical and would also require the need for a whole backpack and not just a standalone device. WIT Background Research 6

8 Budget The original budget included a one hundred dollar contribution from each team member, which put the overall budget at $ It was estimated that the group would use about 75% of the overall budget and there would be an emergency fund of sixty dollars left for last minute expenses. Final costs came to $162.21, a considerably lower number than expected which was due to the inability to make a complete working model and the group not needing money for any remodeling. Consulta tions Project Budget & Time Allotment January February March April Group Work Equip ment Consulta tions Group Work Equipme nt Consulta tions Projected Hours Actual Hours Projected Cost $0.00 $ $50.00 $ $0.00 Group Work Equip ment Consult ations $ $0.00 $ Actual Cost Remaining Budget $ $ $ $ Group Allowance $ Total Projected Cost $ Total Actual Cost $ Estimated Remaining/Overage $60.00 Actual Remaining/Overag e $ Group Work Equi pm ent $50.00 $47.85 Table 1.0 Budget and Time Allotment WIT Budget 7

9 Itemized Report Item Qty Total $14.1 $14.1 Multipurpose Aluminum (alloy 6061), 3/8" Thick, 4" Width, 1' Length $10.1 Chrome-Coated Low Carbon Steel Rod, 1/4" Diameter, 1' Length 2 $ $15.1 $30.2 Self-Aligning Linear Ball Bearing, Closed, for 1/4" Shaft Diameter External Retaining Ring for Linear Bearing, for 1/2" Bearing OD 4 $0.29 $1.16 Steel Extension Spring, 2-1/2" Length, 3/16" OD,.016" Wire, Packs of 12 1 $7.62 $7.62 Steel Extension Spring, Zinc-Plated, 4" Length, 9/64" OD,.018" Wire, $12.8 $12.8 Packs of Ball End HSS Two-Flute End Mill for Alum 1/2 Mill Dia, 1/2" Shank Dia, 1- $28.3 $28.3 1/4" Length of Cut Ball End HSS Two-Flute End Mill for Alum 1/4 Mill Dia, 1/2" Shank Dia, 1" Length of Cut 2 $4.89 $9.78 High Speed Motor 1 $5.49 $ Volt Regulator 1 $1.49 $1.49 Wire (pack of 3 rolls) 1 $7.39 $7.39 Plywood Sheet 1 $ $ Project Variable Gear Box 1 $8.99 $8.99 $14.9 $14.9 Soldering and multi meter kit Cost Per Total $ Table 2.0 Itemized Report WIT 8

10 Sample Calculations Calculation 1.0 (Electrical to Mechanical Power) Calculation 2.0 (Hooke s Law & Newton s Second Law) Then adding frequency, and f = We obtain the general solution: WIT Sample Calculations 9

11 Calculation 3.0 (Two springs connected by one mass) Consider a mass m with a spring on either end, each attached to a wall. Let and be the spring constants of the springs. A displacement of the mass by a distance x results in the first spring lengthening by a distance x (and pulling in the direction), while the second spring is compressed by a distance x (and pushes in the same direction). The equation of motion then becomes So the effective spring constant of the system is, frequency is and the angular oscillation We obtained.39 lbf/in for our spring rate using the described calculations WIT Sample Calculations 10

12 Calculation 4.0 (Two Springs in Parallel) The force exerted by two springs attached in parallel to a wall and a mass exert a force on the mass. Thus, the effecting spring constant is given by Procedure Building our Test Weight System Weight System Bill of Materials: (1) 10 x12 x 3 / 8 Plywood (2) 1 x10 x 3 / 8 Plywood (2) 2 x10 x 3 / 8 Plywood (2) 4 x4 x 3 / Aluminum Plate (2) ¼ x 12 Precision Ground Steel Rods (2) Self Aligning Linear Ball Bearings for ¼ Shaft Diameter WIT Procedure 11

13 (3) Steel Extension Springs 2 ½ Length, 3 / 16 OD,.016 Wire (5) ¼ x 20 Set Screws, ¾ Length (Standard Socket) (3) 1/16 Roll Pins (8) #4, 7/8 Long Wood Screws Aluminum Plates (Do to both plates): After cutting plates to final dimensions, using a ball end mill, mill a 5 / 16 grove 1 from the vertical edge the length of the plate, repeat 1 from the opposing edge for two parallel grooves. Using a ½ ball end mill, cut a 1 long groove, ½ in depth, 1 inch from the vertical edge and 2 inches from the horizontal edge. Repeat from opposing vertical edge. Drill and tap 4 holes ¼ x ¼ from each corner for retaining bolts (set screws) and another in the exact center of the plate. (¼ x 20) Drill three 1/16 holes 1/16 from the top of the plate 1 ½, 2, 2 ½ (respectively) from the vertical edge. Plywood Frame: Cut Plywood to above dimensions. In the 1 Plywood pieces, drill ¼ holes through, 4 from each short edge and ½ from long edge. WIT Procedure 12

14 Putting it together: Place each linear bearing in a groove of one of the aluminum plates. Slide a rod into each linear bearing. Place the other aluminum plate on top of the first plate, locking the bearings into position. Slide each of the three springs in between the two plates, lining them up so that their end loops are concentric with a given hole. Feed a roll pin into each hole in the plate to hold the springs in place Screw all 5 set screws into the plates to hold them together; they should be flush with both sides of the plates. Feed the rods into the pre-drilled holes of the 1 plywood pieces. With the 1 plywood flush against the edge of the 10 x12 pieces of plywood, drill and install the wood screws (2 per side) to hold the plywood pieces together. Use the 2 pieces of plywood on the outside of the frame to retain the rods by mating their faces together and screwing them into the 10 x12 piece (2 screws per side). WIT Procedure 13

15 Data Graph 2.0 shows the necessary force required to produce 2.5W in 1 second over an estimated restricted Graph 3.0 Battery Life of Smart Phones (PC World) WIT 14

16 Results The resulting spring coefficient from calculations #2 and #3 was.39n m -1. Using calculation number four, springs in parallel, it can be deducted that with our available springs it is necessary to have a minimum of 3 springs (whose spring coefficient is.19n m -1 ). It is also understood that when using a universal serial bus (USB) type connection that the minimum requirements for power are 5 volts at ½ amperes, for a power total of 2 ½ watts. Depending on the frequency of the human walking the gear ratio will be determined to either step up or step down the power. It will be necessary to use a voltage regulator as a source of protection for the motor and the device being powered. Discussion of Results Acquiring results on the mechanism and as the device as a whole was very challenging. Developing and manufacturing the spring mass system took a considerable amount of time and there were several problems along this route that were encountered. The tolerances on the linear bearings that were acquired were not as high tolerance as were needed and thus they did not travel along the aluminum rods smooth and offered a lot of movement. It was calculated that there needed to be a total spring constant of 0.40 lb-in. The springs that were ordered ended up having a spring constant les s than 0.20 lb-in and therefore a third one was needed to get to the required spring constant. This could be redesigned so that the same springs could be used by changing the mass. A difficult task after the spring mass device was created was measuring the frequency to see if it matches the walking frequency of 2 Hz. This is important to make WIT 15

17 sure that the mechanism is functioning properly because this affects the rotational speed of the gears and ensures that enough RPM s are being put into the motor to achieve enough of an output. Theoretically the spring mass system should have oscillated at a frequency of 2 Hz however it was undetermined if the system was actually adhering to these principals. Conclusion At the start of this project the group embarked on a challenge to create a viable system to harness the kinetic energy that the human body exerts while walking. In conclusion to this project turned out to be more of a learning experience in the fields of both electricity and motion study than previously planned. While our goal was not entirely reached in the completed and physical form it was logically and theoretically proven to work. The device was conceived from a handful of conceptual designs but in the end the most logically feasible design was chosen. The conclusion came by critically thinking about many aspects of the design and what would and wouldn t work in the real world. Once past this part of the process it was our job to break down each aspect of the design and study ways to model and simulate the aspects of the device. Along the way many problems were encountered regarding the modeling of the system in order to find out what kind of power the device would create and finding the optimum weight for the counterweights system for maximum energy production and minimum overall weight. WIT Conclusion 16

18 Considering this was part electrical project the group needed to familiarize themselves with more in-depth concepts and workings of electrical circuitry and DC motors, understanding power and torque curves and how they correspond to RPM. Once these challenges were overcome a prototype was designed and built. Unfortunately the amount of time and cost to manufacture these prototype parts was not taken into consideration and the machining of the prototype took a large portion of the available funds and time. While a completed model was not the end result of the project the group was able to produce a working spring rate prototype to show that the human walking frequency paired with the correct spring rate and mass was able to create the linear motion that was sought after for the driver of the system. WIT 17

19 References Systems Inc., Piezo. "Piezo Systems: Introduction to Piezoelectric Transducers." Piezo Systems: Piezoceramic, PZT, Piezoelectric Transducers, Piezoelectric Actuators and Sensors, Piezoelectric Fans, Piezoelectric Amplifiers, Piezoelectric Engineering, Ultrasonic Transducers, and Energy Harvesters Web. 03 Mar < Cheever, Erik. "Analogous Electrical and Mechanical Systems." Analogs. Swarthmore College, Web. 2 Feb < Beckwith, T. G., Roy D. Marangoni, and John H. Lienhard. Mechanical Measurements. 6th ed. Upper Saddle River, NJ: Pearson/Prentice Hall, Print. Meriam, J. L., and L. G. Kraige. Engineering Mechanics: Statics. 6th ed. Danvers, MA: John Wiley & Sons, Print. Zill, Dennis G., and Michael R. Cullen. Differential Equations with Boundary-value Problems. Belmont, CA: Thomson Brooks/Cole, Print. "Bowtie- Conversion from Rotational to Linear Motion." Siegfried Herzog-- PSU at Mont Alto, Personal HomePage. Web. 03 Mar < "Electrical & Electronics, Ohm's Law, Formulas & Equations." Angelfire: Welcome to Angelfire. Web. 03 Mar < "Eric Weisstein's World of Physics." ScienceWorld. Web. 03 Mar < "LOCOMOTIVE ENGINE Running and Management - THE VALVE-MOTION." Welcome to the Catskill Archive. Web. 03 Mar < "Miniature Metal Gear Motor - 71 RPM." Hobby Engineering Home Page. Web. 03 Mar < Arar, Yardena. "UPDATE: 3G IPhone's Battery Life Beats AT&T Rivals--But EvDO BlackBerrys Run Longer PCWorld." Reviews and News on Tech Products, Software and Downloads PCWorld. Web. 28 Apr < WIT References 18

20 Appendix (Drawings) The following are drawings of both the original design and the prospective redesign Figure 2 - Spring Mass Prototype WIT 19

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26 Figure 3 - Preliminary Final Design WIT Appendix (Drawings) 6

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