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Power to the people : new Student Union Building energy harvesting Sotola, Sean; Hau, Becky; Anderson, Catherine; Tokuhashi, Naoki 2011

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UBC Social Ecological Economic Development Studies (SEEDS) Student Report Power to the People: New Student Union Building Energy Harvesting Sean Sotola Becky Hau Catherine Anderson Naoki Tokuhashi University of British Columbia MECH 457 Capstone Design Project April 9, 2011 Disclaimer: “UBC SEEDS provides students with the opportunity to share the findings of their studies, as well as their opinions, conclusions and recommendations with the UBC community. The reader should bear in mind that this is a student project/report and is not an official document of UBC. Furthermore readers should bear in mind that these reports may not reflect the current status of activities at UBC. We urge you to contact the research persons mentioned in a report or the SEEDS Coordinator about the current status of the subject matter of a project/report”.NEW SUB ENERGY HARVESTING   STATEMENT OF THE PROBLEM  The new Student Union Building  for  the University of British Columbia  is being designed  to be one of  the most  sustainable  and energy efficient  green buildings  in  the world.   To  achieve  this, many  different  types of energy  saving systems are being implemented in the new SUB.  The goal of this project was to design a multi‐function energy harvesting system that was creative, interactive, and  would educate the public about energy harvesting technologies and sustainable building design.  BACKGROUND INFORMATION  ENERGY HARVESTING  Due  to  growing  concerns  about  global warming  and  resource  depletion,  finding methods of harvesting wasted  energy is becoming an increasingly popular area of research.  There are many different types of wasted energy that  could potentially be scavenged for practical use.   Some examples of possible untapped energy sources are body  heat energy, human footstep energy and waste water energy.   PIEZOELECTRIC EFFECT  Piezoelectric ceramics are a special material that can create an electrical voltage when it is squished or stretched.   This voltage can be used  to power a variety of  low  input power devices, such as  lights or speakers without any  additional help from batteries.  ANALYSIS  Many different methods of energy harvesting were  initially  investigated before finally deciding upon using stacks  made from a piezoelectric material.   There were several promising design applications using these special stacks  that could be  integrated  into the new SUB.   The top three designs were a piezoelectric floor tile, a piezoelectric  stair  case  and  a  piezoelectric  gaming  unit where  users  could  compete  against  one  another  to  see who  could  generate the most power.    To  promote  student  involvement,  an  online  pole was  posted  on mynewsub.com  and  in‐person  surveys were  conducted to see what current SUB users would most want to see  in their new SUB.   The piezoelectric floor tile  was the most popular application because it was thought to be accessible to the widest audience.   DESIGN  The floor tile consists of three major components, the system that allows the weight of the person on top of the  tile  to  squish  the  piezoelectric  stacks,  the  circuitry  that  connects  the  stacks  to  the  lights  and  the  supporting  structure.  A user can step, walk across or dance on the tile and watch it light up with their movement.     CONCLUSIONS  The finished prototype is one tile that is able to light up several lights inside the tile when a user jumps or walks on  and off the tile.  The brightness of the lights is proportional to the weight and impact with which the user steps on  the top of the tile.  The tile will bring people together while playing with the tile and also give visitors to the new SUB an idea of all of  the potential sources of useable energy that we neglect every day.  People will be able interact with the device and  view their own personal energy being scavenged into something useful.  While  other  piezoelectric  floor  tiles  do  exist,  it  is  still  a  very  new  and  cutting  edge  form  of  technology.    This  application and specific method of harvesting energy from footsteps using this type of system is rare and has never  before been done.  RECOMMENDATIONS  The design of the tile would have to be modified before it could be implemented in the new SUB.  An ideal location  for the tile would be somewhere dimly lit, but frequently accessed by the SUB patrons.  The  components of  the device  could be made of more  sustainable materials, but  this was not  feasible due  to  budgetary constraints for the prototype.    If the tile were to be manufactured on a  larger scale,  it could be more  economic to use more recycled parts, as their cost would be less in bulk.  Future improvements to the design could also potentially increase the output power of the device, allowing more  lights to be lit up, or perhaps power something requiring even more energy.   T HE  UN IVE R SITY  O F  BR IT ISH  C OLU MB IA                 PO W ER  TO  TH E  PE O PLE  M EC H  457  C APST O NE  DESIGN  PR O J ECT  W I NTE R  2010/2011 N EW  STU DE NT  U N IO N  BU IL DIN G  E NE RGY  H AR VE ST IN G DE SIG N  PH ASE  T H IR TE EN  –  F IN AL  R E POR T    Revision Date 0 April 05th, 2011 1 April 09th, 2011  Word Count: 1,726  Design Team Members  Sean Sotola Becky Hau Catherine Anderson Naoki Tokuhashi  Client’s Representatives:  Justin Ritchie Liska Richer  Team Design Instructor:  Ramin Khorasany 1 Table of Contents 1 Introduction .......................................................................................................................................... 2 1.1 Purpose of Report ......................................................................................................................... 2 1.2 Format ........................................................................................................................................... 2 2 Objectives.............................................................................................................................................. 3 3 Background ........................................................................................................................................... 4 4 Design and Testing ................................................................................................................................ 5 4.1 Major Components ....................................................................................................................... 5 4.2 How It Works ................................................................................................................................ 5 4.3 Testing and Results ....................................................................................................................... 7 5 Conclusions ........................................................................................................................................... 8 6 Recommendations ................................................................................................................................ 8  2 1 Introduction 1.1 Purpose of Report The purpose of this report is to summarize the results of our design project.  Over the course of the past eight months, an energy harvesting floor tile was designed and built using piezoelectric stacks to generate a voltage that was used to power a series of LEDs in the device. 1.2 Format  The report is divided into four sections: 1. Objectives: the problem statement and interpretation of the problem 2. Design and Testing: the major components, how they work, testing and validation 3. Conclusion: how the final prototype performs and solves the problem 4. Recommendations: suggestions on improving the design and implementation of the device This report is a compilation of a series of previous design phase reports. References to the previous reports will be made in footnotes.   3 2 Objectives A new Student Union building is being designed and planned for the Vancouver UBC campus.  The new SUB building is intended to be a world leader in sustainability and energy efficiency.  The purpose of this project was to design and build some sort of energy harvesting device that could be installed in the new SUB.  The clients for this project were the New SUB AMS.   Based on the needs that were identified by the clients, the purpose of this project was as follows: Problem Statement To design a multi-function energy harvesting system that is creative, interactive, and educates the public about energy harvesting technology and sustainable building design. There are many methods that can be used to scavenge wasted energy from our surroundings.  Many different forms and applications of energy harvesting were researched and analyzed before determining that using piezoelectric technology would be most suitable for this application. 4 3 Background  The early concept generation phases of this project generated a number of different design types. Many things were considered, including a variety of energy harvesting ideas. Designs ranged from widely used technologies like wind turbines, to more obscure concepts such as energy harvesting trampolines. A series of winnowing stages ultimately narrowed the plausible concepts down to just three shown in Figure 1. They use piezoelectric elements to convert walking energy into useable electricity.  Figure 1 - Piezoelectric design choices considered  In order to decide between these options, the choice was taken to the public for feedback, and the general consensus was that the piezoelectric floor option was the most popular. The basic concept of operation can be seen below in Figure 2. A user interacts by walking on the clear top of the tile. The force of walking is transferred to the piezoelectric stack, which powers LED’s through a signal processing circuit. The user experiences the tile lighting beneath their feet with every step.  Figure 2 - Conceptual function of a piezoelectric floor tile   5 4 Design and Testing 4.1 Major Components  The upper section of our design consists of a clear Lexan sheet, a steel frame, and basic circuitry. The bottom part consists of a mechanical leverage system, a base and piezoelectric ceramic stacks. Users will only interact with the Lexan sheet, which will be flush with the surrounding floor, and supports will be press fit into the Lexan to allow room for LED lighting effects. The leverage system provides fourteen times force amplification. In the final circuit design as shown in the ciruit diagram in Figure 3, there are two capacitors, a bridge rectifier, and a number of LEDs.   Figure 3: Electrical Circuit Diagram  4.2 How It Works  The vertical force of the user is applied to four identical lever arms. Figure 4 shows a side view of the system. When the vertical force is applied, the lever arms pull the two metal blocks, tensioning the attached bolts.  Figure 4: Leverage system  The middle section of the leverage system converts the tension created from the lever arms to compression around the piezostack. BRIDGE RECTIFIER 400V 2A LEDS C2 C1 450V 47μF 6  Figure 5: Section view of piezostack system  Force 1 applied, on the left of Figure 5, creates a tension force in bolt 1 and transfers it to block 2.  Then block 2 pulls on bolt 3 which pulls on block 4.  Block 4 squishes the piezostacks (5) against block 6.  Block 6 pulls on bolt 7 which pushes on block 8, which in turn pushes on base 10, assuming bolt 9 is unloaded. Similarly, when force 2 is applied to the right of the figure, a tension force is applied to bolt 9, pulling on block 8.  Block 8 pulls on bolt 7, which pulls on block 6.  Block 6 squishes the piezostack (5) against block 4 which pushes the head of bolt 3 against the base (10). A solid model representation of the system is shown in Figure 6.  Figure 6: A solid model of the leverage system  When subjected to compression, the piezostacks output a positive voltage and will also produce a negative voltage once the compression is released to return to the steady state. A full wave bridge         Fapp 1 Fapp 2 7 rectifier is used to ensure the current flows in one direction. The current is smoothed through two capacitors, which are used to power LEDs. The accumulated charge is able to dissipate over time, resulting in the LEDs being lit up for a longer period of time.  4.3 Testing and Results The main objective of the prototype is to harvest sufficient energy to power LEDs or equivalent. Research was done thoroughly to specify the piezoelectric stacks needed, tests were performed using a compressive rig on one piezoelectric stack connected to an initial electric circuit with four LEDs1. The tests verified that a series of four LEDs can be lit by applying force onto the compressive rig, thereby validating the piezoceramic material. A physical wood prototype of the proposed leverage design to excite the piezoelectric stacks was also built. It identified major areas that required additional support and constraints and potential flaws in the leverage design2. Upon modifications of the leverage design, the final design was finalized after extensive calculations3 and computer analysis in SolidWorks.  Final testing on the entire assembled device included strength tests4 and trials of a combination of activities performed on the floor tile and varying weights of typical adult users5. From these tests, it was concluded that while the device has sufficient strength and structure support for supporting a user’s weight, the tile was not entirely stable at the outer edges. In addition, the optimal number of LEDs is determined from the limiting voltage that the piezoelectric stacks are capable of generating in the case when a light user performs a stepping motion onto the floor tile. The optimal number of LEDs is configured in three strings of two LEDs in parallel with each other. Additional surveys were conducted towards users to question them about their experience after interacting with the device6. These results will aid in generating recommendations regarding the structure of the device and how the device can improve on the user’s experience.                                                             1 See Phase 10+11 Section 3.1 2 See Phase 10+11 Section 3.3 3 See Phase 10+11 Appendix 4 See Phase 12 Section 2.3.1 5 See Phase 12 Table 2 6 See Phase 12 Section 2.3.3 8 5 Conclusions The prototype was successful in the fact that it fulfilled its design requirements. It educates users that even something as small as footsteps, if used correctly, can be put towards doing useful work. The aim wasn’t to educate about piezoelectrics in particular, but educating about sustainability as a whole. We believe the design, if presented correctly, can help inject ideas of sustainability into the mindset of the user. It is innovative due to the fact that piezoelectric harvesting is a cutting edge technology, and it is creative due to the fact that illuminating floors are seldom seen. It promotes exercise because it beckons users to jump on it, it is directly interactive with the user, and it acts as a conversation piece, helping to bring people together and share their ideas of sustainability. If recycled materials could be implemented for the final design, it would promote the 3 R’s, and give it an overall “greener” footprint. In terms of measurable performance wise, the prototype withstood a variety of operating conditions we put it through, and it produced a significant light output for even the lightest of individuals tested. By our criteria, the prototype was a success. 6 Recommendations Through testing of the final prototype, several issues became evident that need remedy before the production unit. They are listed below: 1. It should be fixed to the floor. It would improve stability as well as reduce the tendency for the tile to tilt. 2. Cotter pins should be incorporated into the shafts. Otherwise, the shafts will be pushed out over time. 3. Having thinner or no bushings would be beneficial in the fact that the tile would displace less when it is stepped upon. Ideally, if no plastic bushings are present, the displacement of the tile would be negligible. 4. A proposed lighting effect would be to laser etched the underside of the Lexan with a message or a picture, like “Powered by You”, a picture of a leaf, or the UBC logo. It would illuminate the same matter as an LED edge lit sign. 5. Investigation into the use of more sustainable or recycled materials should be considered if possible. Availability may be an issue, but it is more feasible at large scale. 6. Though white LEDs are the brightest variety, coloured tints can be used to change the colour while still keeping a high light output efficiency for variety or emphasis 7. Seals between tiles may be necessary to prevent debris or water from entering. 8. Doubling the height of the piezoelectric stack will double the performance of the tile, so maximizing the amount of piezoelectric material per unit cost is critical during the final sourcing of components. The lower the cost, the more feasible it is to implement more per tile. 

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