Project Proposal and Feasibility Study Team 1: Empower

Transcription

1 Project Proposal and Feasibility Study Tea 1: Epower Tea Mebers: Scott Vander Laan Joe Holtrop Nate Wybenga Tiothy Hirschberg Tea Advisor: Prof. Nielsen Calvin College ENGR 339 Deceber 5, 008

2 Table of Contents 1. Abstract...1. Custoer Profile Proble Stateent Lack of power grid reliability and availability Need for alternative power generation Need for low cost design Design Requireents Syste Overview Charging Syste Power Conditioning and Distribution Syste Storage Syste Cost Charging Syste PCAD Syste Storage Syste Syste Maintenance Design Context Cliate / Weather Patterns Water availability Local incoe / Affordability Project Necessity Christian Perspective and Design Nors Integrity Transparency Stewardship Cultural appropriateness Alternative Systes Alternative Charging Systes Huan Powered Wind Solar Charging directly fro the power grid Alternative Power Conditioning and Distribution Systes Direct Connect Rectification Power Factor Correction Voltage Control Current Control Alternative Storage systes... 1

3 Batteries Syste selection Charging Syste Power Conditioning and Distribution Syste Storage Syste Syste Paraeters Charging Magnet/Coil paraeters Power Condition and Distribution Syste Cost Efficiency Flexibility Regulations and Standards Energy storage syste Preliinary Design Charging syste Power Conditioning and Distribution syste Storage syste Intellectual Property Charging Syste Previous Work Current Siilar Projects Future Ties to our project Power Condition and Distribution Syste Project Manageent Project Tietable Projected Costs Labor Hours Charging Syste Bill of Materials PCAD and Energy Storage Systes Bill of Materials Project Deliverables Project Suary...41 Appendix A: Wind Generator Efficiency Calculations... A1 Appendix B: Solar Panel Cost per Watt... B1 Appendix C: Magnet Power Generation Derivation and Analysis... C1 Appendix D: Magnet and Coil Optiiation Calculations... D1 Appendix E: Flutter Band Power Calculations... E1

4 Appendix F: Patent 6,73,680 extraction of energy fro flowing fluids... F1 Appendix G: Charging Syste Related Patents...G1 Appendix H: Project Gantt Chart...H1 List of Figures Figure 1: Syste Block Diagra... 4 Figure : Map of South Africa... 7 Figure 3 Siple Flutter Band Figure 4: Repelling agnets wind power design Figure 5: Solar Radiation Potential in South Africa Figure 6: Input Voltage Control Figure 7: Output Voltage Control Figure 8: PCAD Block Diagra... 4 Figure 9: The two priary agnet/coil configurations studied Figure 10: Power generated as a function of tie Figure 11: Magnetic Material Options... 9 Figure 1: Charging Syste Layout Figure 13: Grid Input Power Supply Figure 14: Boost DC-DC Converter Figure 15: Upcoing Mechanical Work List of Tables Table 1: Econoic easures of South Africa,... 9 Table : Poverty Incoe by Household Sie Table 3: Properties of various rechargeable batteries... 1 Table 4: Charging Syste Decision Matrix... 3 Table 5: Material Properties of NIB and ceraic agnets... 9 Table 6: Labor Hours and Cost Table 7: Charging Syste Bill of Materials Table 8: PCAD and Energy Storage Bill of Materials... 41

5 1. Abstract Epower is a tea of two echanical and two electrical and coputer engineering students at Calvin College. For their yearlong senior design project, the tea proposes to design a sall-scale power generation, storage, and distribution syste for South Africa. This syste will help alleviate the load shedding proble in South Africa, and provide electricity to those who do not have access to the power grid. This idea was inspired fro conversation with Cape Peninsula University of Technology. Epower has chosen the flutter band as a eans to generate electricity. The flutter band uses aeroelastic flutter to transfor wind energy into electrical energy. The idea of a flutter band is relatively new and no coercial applications are yet available. As such, the tea will use an iterative design and prototype approach to coplete the echanical aspect of the project. Based on initial calculations and the experients of others, the tea believes the flutter band will be a feasible ethod for generating electricity. On the electrical side, the tea has decided to use lead-acid batteries for storage and to build a power conditioning and distribution syste. The general application of the electrical syste has been proven in other sall-scale alternative energy systes. However, the tea faces the unique challenge of aking the syste inexpensive as well as integrating it with the flutter band. Based on initial research the tea has decided that the power and conditioning syste is also feasible. 1

6 . Custoer Profile Epower will design a sall-scale power syste that will be charged using alternative energy such as wind or solar power. The syste will store the electrical energy and be able to discharge it at a rate eeting the end users needs. In order to specify these requireents and ensure the design nors are et, a custoer profile will guide the objectives as well as deliverables for the project. The end users live in various cliate regions of South Africa either on the edge of shantytowns with liited access to reliable power or in reote regions with no power. Due to the poverty in these locations, the end user s electrical load consists priarily of a few light bulbs, a radio, or other sall electronic devices. End users on the edge of shanty towns typically have an electrical need of 150 watts for 3 hours every other day during load shedding. End users in reote locations typically have an electrical need of 50 watts during the day and evening. End users in reote locations have a lower electrical rate than those in shanty towns due to the siplicity of their lifestyle. It is assued the end user has liited education on echanics and electricity and ay not be able to read or write, but will be able to perfor basic aintenance tasks. The end users ay not all speak the sae language. The end user typically has an incoe of $1500 USD/year and has little savings. The end user does, however, have access to icro-loans. 3. Proble Stateent 3.1. Lack of power grid reliability and availability South Africa suffers fro frequent power outages due to electrical deand exceeding supply. South Africa has about 8% reserve electrical capacity copared to the worldwide average of 15%. To copensate, power supplier Esko schedules regular load shedding. In this situation, any regions of the country have scheduled power outages, typically every other day. These power outages are a few hours long. In the event of unexpected increased deand, power outages occur alost without warning.

7 Load shedding will continue to occur at least through when Esko hopes to have excess electrical production capacity of 3000 MW during peak hours. There are still any rural regions in the country which are not connected to electrical infrastructure. According to Electric Capitalis: Recolonising Africa on the Power Grid : Although Africa is the ost under-supplied region in the world for electricity, its econoies are utterly dependent on it. There are enorous inequalities in electricity access, with industry receiving abundant supplies of cheap power while ore than 80% of the continent's population reain off the power grid. 3.. Need for alternative power generation Load shedding and lack of electrical infrastructure akes alternative power generation sources necessary for electrical consistency in the daily life of South African residents. Siply storing energy fro the grid in a bank of batteries for use during power outages actually increases the need for load shedding as it increases deand without increasing capacity. The only solution to the current load shedding proble is to increase electrical production capacity by eans such as alternative power generation. Also, for those residents who currently have no access to electrical infrastructure, h aving a sallscale power syste at the end-user s hoe is the quickest way to achieve electrical power Need for low cost design The target end user typically has an incoe of $1500 USD/year and has little savings. This eans that the sall-scale power syste needs to be inexpensive. A key factor in creating the least expensive syste possible is ensuring that the syste does not exceed the power production needs of the end-user. The typical cost of building a power generation source (using wind, solar, natural gas, etc.) is $1-5 /watt. Therefore, any 1 Load Shedding Part of life for 5 years. Nov. 007 All Africa.co. 16 Nov. 008 < Huan Sciences Research Council. Electric Capitalis : Recoloniing Africa on the Power Grid. Ed. David A. McDonald. London: Earthscan,

8 production capacity beyond what is necessary for the end-user will add unnecessary costs to the project. 4. Design Requireents 4.1. Syste Overview Since the syste will serve as a backup power source during load shedding, the proposed design will provide electricity for only a liited nuber of iportant appliances that the end user ay require such as incandescent or fluorescent lights, a sall refrigerator, and fans. Additionally, if the syste is used in a poor area without access to the electrical grid, the power requireents will generally be inial. Therefore, the proposed syste will be designed to output electricity at a rate of 150 watts for roughly 3 hours. In order to eet this power requireent, the syste s design will incorporate three sub-systes: a charging syste, a power condition and distribution (PCAD) syste, and an electrical storage syste. The sub-systes will be connected as seen in Figure 1 below. Figure 1: Syste Block Diagra 4.. Charging Syste The charging syste s design will be such that it provides electricity to the PCAD syste at an average rate of 50 watts. Potential non-fossil fuel energy sources that will be considered in this feasibility study will include huan-produced power, wind, and solar. Furtherore, the charging interface s design will allow straightforward assebly using locally-available aterials and coon tools, such as screwdrivers and pliers. 4

9 4.3. Power Conditioning and Distribution Syste The PCAD syste will be the interface between the charging syste, the energy storage device, and the end user s load. The syste will take the electricity fro the charging syste and condition it. The condition electricity will then be used to charge the energy storage device. The charging of the energy storage device will be regulated by the PCAD to prevent the battery fro being overcharged. The PCAD syste will also be used to regulate and transfor the output fro the battery to single phase 0/30 volt AC at 50 H, which is the standard power supply voltage in South Africa Storage Syste The storage syste will need to store electrical energy. The design requires that the storage syste be able to provide 150 watts for 3 hours Cost As previously entioned, a ajor constraint to the syste s design will be its cost. For this reason, the total syste cost is $00. The prototype target cost will be larger as soe coponents in the final design could be purchased at a reduced bulk cost Charging Syste The target cost for the charging syste is in the $60-$80 range PCAD Syste The target cost for the PCAD syste prototype is less than $100. This budget provides soe argin for changes in the syste design. Also, it will allow ultiple copies of key coponents in case one is destroyed or daaged. The final PCAD design should cost less than $50. This price reduction should be achievable if parts are ordered in bulk Storage Syste The storage syste cost will likely be deterined by arket costs. However, Epower projects a target cost of $80 for the storage syste. 5

10 4.6. Syste Maintenance As a whole, the power syste ust be easily-serviceable; that is, any required aintenance ought to be straightforward, requiring little knowledge of the syste s details. The syste should be generally easy to aintain with little echanical or electrical skills needed. 5. Design Context 5.1. Cliate / Weather Patterns South Africa has both diverse cliate and weather patterns. This is due in large part to the country s specific geography. As its nae suggests, South Africa is located on the southern tip of the African continent. See Figure for a ap of South Africa, courtesy of the University of Texas Libraries, The University of Texas at Austin. 3 Though uch of the country can be generally classified as sei-arid with teperate cliates, there also exists a wide variation. South Africa has a long coastline, with nearly 3,000 kiloeters (k) of coast bordering both the Atlantic and Indian Oceans. Yet South Africa s inland is coprised of high plateaus. Due to these higher altitudes in uch of the country, t he cliate is cooler than other regions at siilar latitudes, like Australia. The coastal area around Cape Town has a Mediterranean cliate with war dry suers and wet cool winters. Average wind speeds vary fro 8 to 16 knots, 4 with a standard deviation of. knots. The eastern side of the country, especially along the border with Moabique tends to be sub-tropical. In the Northwest, the cliate is doinated by the Kalahari Desert. 5 3 "South Africa Maps." Perry-Castañeda Library Map Collection The University of Texas at Austin. 15 Nov. 008 < 4 South Africa W indspeed Statistics Windfinder. 01 Dec. 008 < 5 Cliatic Conditions in South Africa South Africa Travel. 15 Nov. 008 < 6

11 Figure : Map of South Africa 7

12 5.. Water availability The country of South Africa receives an average of of rain each year. The world average is a year, so South Africa has significantly less water available than other regions of the world. Due to low aounts of rainfall, water is a scarcity in South Africa and highly valued. Additionally, ost of the population does not have direct access to rivers or streas as an energy source. With low aounts of water, the deand for clean safe drinking water is harder to fill. South Africa currently has a shortage of drinking water. The drinking water shortage liits the aount of water available for energy production. The other ajor consuer of water in South Africa is the anufacturing sector. Manufacturing processes often require large aounts of water to operate. South Africa s Industry is developing and expanding, causing the deand for water in industry to increase. With large deands for water in other areas, the availability of water for energy production is liited Local incoe / Affordability The apartheid in South Africa fro 1948 to 1990 held back the developent of the country, and as a result it still faces high uneployent, poverty, and lack of econoic epowerent aong the disadvantaged groups. 8 Table 1 shows the econoic easures of South Africa. 8 6 Suitte, J. M., S. G. Reynolds, and C. Battelo. " Grasslands of the World." Food and Agricultural Organiation of the United. 17 Nov. 008 < 7 South African Tours and Travel. 17 Nov. 008 < 8 South Africa: Incoe. Encyclopedia of the Nations. 16 Nov. 008 < 8

13 Table 1: Econoic easures of South Africa GDP per capita (007 estiate) $9700 Per capita household consuption (001) $554 Uneployent rate (007 estiate) 4.3% Nuber of poor persons (001) 5.7 illion Percent of population below the poverty line (000) Household incoe by percentage share (000) 50% Lowest 10%: 1.4% Highest 10%: 44.7% Table below shows poverty incoe by household sie in South Africa. 9 Table : Poverty Incoe by Household Sie Household Si e Monthly Incoe (R, 001) Monthly Incoe ($US, 001) The econoic situation of South Africa places heavy financial constraints on the design. The target end-user is a faily of 3 or 4 people with a typical incoe of about $1500/year or $100-$130/onth Project Necessity Having consistent electrical power is not a atter of survival. However, it is a atter of necessity in order to be a part of odern society, and thus this project is iportant for those without power or without reliable po wer. If the designed syste is affordable it will becoe a beneficial syste for any residents in South Africa and for the continued developent of their country. 9

14 5.5. Christian Perspective and Design Nors As a senior design tea, Epower seeks to produce a design that not only works but also eets specific goals relating to Christian perspectives. These goals help the tea to shape the scope of the design, and their consideration is discussed throughout this report Integrity Tea Epower seeks to display integrity in the conduct of their project. As a tea of integrity, work will be done honestly and accurately. Tea Epower desires to be a group that can be trusted and relied upon to follow through with their proises and provide truthful responses. To have integrity all work ust be done thoroughly with credit given to all sources. If an idea is not fro Epower, the sources ust be properly identified and given credit for their work. In designs all aspects need to be addressed. Nothing should be assued to be correct; all aspects should be tested and verified Transparency With a project that cae fro a desire to help people, transparency ust be a priary focus in ensuring that the original intent of the project is fulfilled. As a tea Epower ust be clear about the otives of our decisions. Doing work that is transparent will strengthen the relationship tea Epower will have with potential custoers. Being transparent builds trust and adds creditability to tea Epower. Being a trustworthy and credible tea will ake Epower ore likely to succeed Stewardship Stewardship is an iportant concept for the design. As discussed in Sections 3.1, reliable access to the power grid has been and will likely reain a proble in South Africa. This fact, coupled with South Africa s dependence on foreign capital investent, 10

15 eans that electricity supplies will reain below the level of deand for the next several years. 9 An inexpensive alternative energy supply would allow South Africans to better utilie current resources. Most North Aericans take electricity for granted and so do not realie how uch their daily lives depend on it. By providing a reliable backup source of electrical energy, Epower will allow people to better utilie existing resources and cultivate further talents and investents. In addition, an alternative energy source will help in the effort to use resources wisely. Global Waring has becoe a rather coon topic these days. And as such, renewable energy sources see to be a cliché answer to the proble. However, Epower believes that such sall-scale systes will help the situation. Every little bit counts, especially when all of the little bits are added together. Despite the stereotypical nature of the response, it is still a good response renewable, alternative energy sources are a way to practice good stewardship Cultural appropriateness With all the benefits of sall-scale alternative energy sources, it is critical that these benefits can be used by the people. In Design for the Other 90%, Barbara Bloeink argues that designers and engineers are so used to their own situation and resource allocation that they often ignore constraints that those in developing nations face. 10 Designing for these people eans taking into account their cultural, social, and econoic situation. In South Africa, the fall of apartheid has led to uch reconciliation between various social, econoic, and racial classes. However, there still exist inorities and people relegated to the argins. Epower seeks to design a syste that will not accentuate these differences the design needs to be accessible to a wide range of users. The design needs to fit into the South African context. For the design to be culturally 9 "South Africa Foreign Investent." Encyclopedia of Nations Sep. 008 < 10 Sithsonian Institution. "Design for the Other 90%." Museu Editor, Head of Publications. Ed. Chul R. Ki. New York: Cooper-Hewitt,

16 appropriate, it ust be usable by South Africans, and yet not take away or detract fro those aspects that ake South Africa unique. South Africa has 11 official languages, and nuber of ethnic inorities. 11 Epower ust design a syste that does not arginalie such groups. It is hoped that the widespread push toward electrification will ake Epower s design both useable and culturally appropriate for ost if not all of the population. 6. Alternative Systes 6.1. Alternative Charging Systes Huan Powered Eploying huan otion for electrical power generation has been coonly used on a relatively sall-scale, one of which requires a stationary bicycle-generator syste. Due to its siplistic design, Epower initially chose to ake this option a secondary energy source for the charging syste. Using a highly-efficient generator (95%) and a personnel of average fitness, such a syste can provide a charging rate between 10 to 300 watts; however, the duration for which this rate can be held ay vary fro roughly 4 to hours based on an individual s fitness Wind Aeroelastic flutter A flutter band (FB) uses the vibrations fro a thin belt of aterial to capture energy fro the wind. The belt oscillation is caused by aeroelastic flutter. Aeroelastic flutter occurs when a oving fluid oves across an object, causing it to vibrate. The positive feedback provided by the oving fluid causes the vibration to increase. The flutter band consists of a thin belt stretched across a certain area so that wind is allowed to flow over the belt. Figure 3 shows how a flutter band will vibrate. 11 "The languages of South Africa." South Africa: Alive with Possibilities SouthAfrica.info. 15 Nov. 008 < 1 DeSteese, JG. Electric Power fro Abient Energy Sources. Pacific Northwest National Laboratory. Septeber 000 1

17 Figure 3 Siple Flutter Band Magnets are attached to the band typically on one side of the band. The agnets vibrate in between a set of coils generating an electrootive force in the coil and producing electrical power. The siplicity of the flutter band design akes it a flexible energy option. The aterials necessary to ake the wind belt are sall and inexpensive. There any different ways designing the wind belt so that it fits in different locations. The flutter band s ain drawback is that ost of the work done with the is experiental. Flutter bands are not currently available for coercial use Repelling agnets A repelling agnets wind power design such as is shown in Figure 4 is a siple ethod of generating electrical power. Figure 4: Repelling agnets wind power design 13

18 Electrical power generation is initiated by wind blowing into the ebrane. This force pushes the agnets closer together. However, the agnets are aligned with siilar poles facing each other as to repel. This causes an opposing force on the ebrane as the agnets push away fro each other. Because the force of the agnetic repulsion is always changing, the ebrane oves in an oscillating otion. By placing a coil of wire around the region of agnetic repulsion electrical power is generated. Such design is a worthy candidate for use in the sall-scale power syste. The frae of the device can be ade out of any available aterial; wood, etal, plastic, etc., ensuring that building aterials would be locally available. The siple design eans the device would be lightweight and easy to transport. The transparency of the design eans locals would be able to understand and perfor inor repairs on the device. The general challenge of such a design would be generating the required 50 watts of electrical power within the budget constraints and while aintaining a sie that is easily transportable. This design was conceived by tea Epower, and appears to be copletely original. No siilar designs could be found, so the feasibility of the design given the constraints can only be deterined with further analysis Horiontal Axis wind turbine The operation of sall-scale horiontal axis wind turbines is hapered by high friction. This eans greatly reduced syste efficiency. Based on existing sall-scale wind turbine design, expected efficiency is around only %. See Appendix A: for these efficiency calculations. Costs also tend to be very high for horiontal axis wind turbines. Purchasing a coercial syste which operates at 50 W will cost around $ Horiontal axis wind turbines are also notorious for rapid bearing deterioration. All of these factors greatly reduce the feasibility of using a horiontal axis wind turbine in the sall-scale power syste. 13 Phieco Phieco.net. 4 Dec. 008 < 14

19 Solar Photovoltaic cells Solar panels or ore specifically Photovoltaic (PV) cells are a coon source of alternative energy. The basic concept behind PV is that solar energy in the for of a photon is converted into electrical energy. Electricity is produced when the photon hits a seiconductor, typically silicon, and this energies electrons enough to flow. The flow of electrons is then captured by etal conductors and results in Direct Current (DC) electricity 14. Photovoltaic cells have a nuber of benefits. First, the technology has been proven in nuerous applications fro the international space station to everyday calculators. Solar panels are typically quite robust and can handle any nuber of environents. PV cells do not contain any oving parts and they require little to no aintenance, aside fro keeping the panels clean. Solar panels can be ounted once and left out in the eleents with little care required fro the owner. Moreover, South Africa has an abundance of solar energy. As shown in Figure 5 uch of South Africa receives ore than 6 kwh/ /day 15. Despite the benefits of PV, there are also a nuber of disadvantages. First, solar panels are relatively expensive when copared to other eans for generating electricity. Typical costs for a solar panel are $4.50 $6.00 per watt, while conventional sources such general produce for $ $.00 per watt. 16 Appendix B: Solar Panel Cost per Watt provides a cost breakdown for solar panels and copares the cost per watt for a nuber of anufacturers. Solar panels are generally only econoically feasible with governent grants, tax credit, or where the electrical grid or other sources are unavailable. 14 Neaen, Donald A. Microelectronics: Circuit Analysis and Design. 3rd ed. New York: McGraw-Hill, "Maps of Wind and Solar Energy." Solar and Wind Energy Resource Assessent (SW ERA). Nov UNEP/GRID-Sioux Falls and INPE-Brail. 15 Nov. 008 < ea=-1&energycategory=17&orderby=geoarea>. 16 Solarbu. Oct Solarbu, Inc. Nov. 008 < 15

20 Another proble facing solar panels would be the installation. Aligning panels to achieve axiu energy capture is no trivial task and would likely require soeone with expertise or previous experience. Figure 5: Solar Radiation Potential in South Africa A third difficulty that would be particularly detriental in South Africa is that PV panels, depending on the type, tend to lose efficiency as their teperature rises. 17 Especially during the suer, teperatures in South Africa can rise to as uch as 35 degrees Celsius, 18 which would detract fro potential energy generation. 17 Borenstein, Severin. "The Market Value and Cost of Solar Photovoltaic Electricity Production." Center for the Study of Energy Markets (CSEM) Working Paper Series (008). 18 Werner Louw 16

21 Finally, solar panels can generate electricity only when they receive direct sunlight. This eans that any electricity needed at night or on a cloudy day would have to be stored. Although Figure 5 shows South Africa has a large potential for solar energy, uch of this area is desert and largely uninhabited. With closer inspection, one sees that uch of the population lives in areas with less solar potential. While proven, solar panels siply do not eet the needs for inexpensive energy generation in developing nations. Supply of the panels becoes a proble and often requires that the parts be iported which leads to further increases in cost as well as directing cash flow out of the country Charging directly fro the power grid Charging directly fro the power grid is an option for those end users who have an available but unreliable power grid. Soe end users ay have a higher energy need than renewable energy or huan powered sources can provide. Although charging directly fro the power grid increases the proble of load shedding, it enhances the appeal of the power syste and extends its usefulness. 6.. Alternative Power Conditioning and Distribution Systes One critical aspect of the syste design is the PCAD syste. This portion of the design will connect the charging source, battery, and load. The paraeters of the PCAD syste will be dictated by the charging syste output, battery capabilities, and load needs. Epower seeks to design an efficient and flexible interface to eet these needs. The PCAD ust control the voltage wavefor and as well as the voltage level. In order to eet these requireents, active regulation will be needed. Figure 6 shows the block diagra for the input side of the PCAD syste. 17

22 Input fro Grid/Charging Source Input Rectification and Filtering Wavefor Shaper Output Transforer Output Rectification and Filtering Output to Battery Controller Figure 6: Input Voltage Control Figure 7 shows the block diagra for the output of the PCAD syste. These two figures show the basic functions that the PCAD voltage control ust perfor. Within these blocks there are a nuber of options. Input fro Storage Source Input Voltage Step Up Inverter Output Transforer Output Filtering Output to Load Inverter Controller Figure 7: Output Voltage Control Direct Connect The ost efficient option to power a load is to connect the source directly to the load. While reliable high quality power is iportant, each transforation or power conditioning step results in loss of efficiency. However, in order to connect the syste to the source the output voltage and current need to be either alternating current (AC) or direct current (DC). Unless the charging source can produce an acceptable voltage wavefor and an adequate voltage level, conditioning will be necessary Rectification Rectifiers are one of the basic building blocks in any circuits. These circuits utilie the ability of diodes to let current pass in one direction, but not the other. 18

23 Although siple, rectifiers tend to have low efficiencies when dealing with low voltage levels. This is due to the fact the diodes typically have a 0.6 to 0.7 volt drop across the. There are a nuber of front end classifications for rectification circuits. However, the full-bridge is ost coonly used, offering a good coproise between siplicity and efficiency. If the syste has access to the grid, it will only be the single phase coonly seen by consuers. The interface fro the grid will then only require single phase rectification. Rectifiers will be needed to sooth the input voltage fro the grid and possibly fro the charging source. Efficiency will be key constraint of any rectifier used. Rectifiers cannot significantly raise or lower the voltage level; therefore, additional coponents will be needed Power Factor Correction Miniiing distortion and aintaining a power factor near unity are critical for proper power syste operation. However, the battery charging interface will not require any additional filtering beyond rectification and voltage step-down. Additionally, because the output will coe directly fro the battery, haronics and distortion will only result fro the inverter circuitry. This circuitry will need to regulate itself. Specialied power factor correction circuitry will result in lower efficiencies. 19 Moreover, the anticipated end-user load is not going to be large and will be ostly resistive. Therefore the power factor will be near unity and no additional power factor correction will be needed Voltage Control Switching A switching regulator uses the on and off states of transistors to control voltage. Often they include an additional storage eleent such as an inductor. Switching regulators are also ore efficient as they are in either an on state (conducting) or an off 19 Mohan, Ned. First Course on Power Electronics. Minneapolis, MN: MNPERE,

24 state (non-conducting), so the wasted power is iniied. A switching regulator circuit can be used to control the voltage wavefor Pulse Width Modulation Pulse width odulation (PWM) is a versatile ethod of controlling a signal. In power systes, PWM can be used to transfor DC to AC as well as perfor DC to DC voltage transforations. PWM works by varying the length of pulses, and by integrating over these pulses, one can achieve the desired signal. One of the strengths of PWM is its flexibility. PWM will likely be used in the output stage, taking the DC fro batteries and converting it to AC Transforers There are a nuber of options for transforing voltage levels. The first and ost obvious is a standard transforer. These are available coercially or they could be ade fro odified coponents available locally, such as a car alternator. However, traditional transforers have soe disadvantages, naely that they tend to be large and bulky when copared to integrated circuits. Voltage can be stepped up or stepped down using specialied circuit designs. Buck and Boost circuits are the ost coon. Buck circuits can only step down the voltage, while boost circuits only step up the voltage. A third topology, known as the Buck-Boost, can step up or step down the voltage. The Buck-Boost converters offer ore flexibility, but the circuit is ore coplex. Within these categories any specialiations and variations are possible Current Control The syste will require soe eans of controlling the current. The current will be generally liited by the syste; the charging and storage systes will only be able to provide a liited aperage output. However, there will need to be soe for of protection fro current and voltage spikes. 0

25 Fuses are a basic, but reliable eans to control current. They are generally inexpensive; however they can only be used once before they need to be replaced. Fuses would need to be located in such a way that they can be replaced when they are blown. On the other hand, circuit breakers provide protection like a fuse, but can be reset after a fault. Circuit breakers typically cost ore than a siple fuse Alternative Storage systes In order to provide power during outages an energy storage device is necessary. An energy storage device allows energy to be captured at an earlier tie fro a source such as the power grid or a wind turbine and be used when needed. The discussed possibilities ai to present an overview of the different energy storage devices. The eventual goal of the final syste is to be able to choose fro a variety of possible energy storage devices and for the all to be able to be copatible with the syste Batteries Batteries are the ost coon way to store energy that is needed for electrical applications. Batteries coe in variety of types and sies so there are any points to consider when purchasing a battery. Table 3 copares the properties of various rechargeable batteries. Table 3: Properties of various rechargeable batteries 0 Battery Type Cost [$/Wh] Weight [Wh/kg] Sie [Wh/Liter] Recharge Cycles Efficiency Lead Acid $0.17-$ %-9% Lithiu-Ion $.80-$ ,00-3, % NiCd $ ,500-,000 70%-90% NiMH $0.99-$ ,000 66% Lead Acid Lead acid batteries are a coonly used type of battery; their ost coon application is in car batteries. The advantages of lead acid batteries are their cost, versatility, durability, and reliability. Lead acid batteries have been in use for a long tie so there is uch known about the, aking the reliable and widely available. The 0 1

26 reason that lead acid batteries are not used in ore applications is their large sie and weight. For an energy storage device such as a power backup, sie and weight are not big issues because the device does not need to be oved around frequently Lithiu-ion Lithiu-ion batteries have a high energy density and a large nuber of ties they can be charged and discharged. Lithiu ion batteries are coonly used for electronic devices like digital caeras that require large aounts of energy but need to be as sall as possible. The ajor disadvantage of lithiu-ion batteries is their high cost NiCd (Nickel Cadiu) NiCd batteries have a higher energy density than lead acid batteries but do not have the energy density of lithiu-ion batteries. One ajor disadvantage of NiCd batteries is their susceptibility to the eory effect. The eory effect akes the batteries output ore unpredictable as the battery ages. NiCd batteries are also known to be an environent haard and are banned in soe countries NiMH (Nickel-etal Hydride) NiMH batteries are cheically siilar to NiCd batteries but solve soe of the probles NiCd batteries have with eory effect and environental friendliness. However they have a shorter life and are less efficient. Their other benefit over NiCd batteries of having a larger energy density is of little value in their desired application for this project Syste selection Charging Syste The charging syste was selected using the using the decision atrix shown in

27 Table 4. Criterion Material Availability Cost Average Charging Rate Safety Sie/Weight Maintenance Installation Table 4: Charging Syste Decision Matrix Weight Bicycle Flutter Band Op. Magnets Wind Turbine P.V Total: As can be seen in Table 4, the flutter band received the highest nuber of points and was chosen for ipleentation in the sall-scale power syste Power Conditioning and Distribution Syste The PCAD syste ust interface with both the charging and storage systes. Therefore, the design of these systes will affect the decision for the PCAD syste. As discussed in Section 6., the PCAD syste has two ain subsystes: the charging control and the discharging control. Figure 8 shows a block diagra of the PCAD syste. 3

28 Noisy Signal fro Flutter Bands Rectification & Soothing Voltage Step Up Switch Battery Charge Control 1 VDC at Battery Voltage Transforer Rectification & Soothing 0/30 VAC fro grid Voltage Transforer Inverter Voltage Step Up 0/30 VAC to load Figure 8: PCAD Block Diagra Voltage Transforer The tea has decided to use a basic power supply set up for the AC grid input. The design tea has experience with the Grayark 803 power supply, and so has chosen to use it. This is a copact power supply that takes an AC input and provides a variable DC output. The power supply is targeted as an educational syste, and so the coponents are easy to replace and odify. This circuit will be used as a building block for the voltage transforation and rectification for the power grid input. It will need to be odified to take 0/30 VAC. The power ratings of this circuit will be sufficient to charge the battery. This power supply is both siple and provides isolation due to the transforer. Moreover, this particular power supply has an adjustable output voltage which will provide flexibility in the prototyping stage 4

29 Rectification and Soothing For the rectification of the flutter band input, Epower will initially be using diodes and capacitors to create a basic bridge rectification circuit. These coponents, available in Calvin s electronics lab, will be used to test a prototype flutter band. The design will be based off of the initial calculations for the flutter band output. However, experients early next seester will reinforce the data needed to design the rectification coponent Voltage Step up A Boost converter will be used to step up the voltage fro the flutter band. Although transforers are sipler and ore readily available, based on the initial calculations for the flutter band output, a transforer would be infeasible. A Boost converter will work on the DC output fro the rectification, and the gain can be adjusted to eet the battery charging needs Switch A siple switch will be used to allow the user to select the charging ethod. This is inexpensive and still provides flexibility for the end user. By choosing a siple switch Epower can aintain lower costs and use locally available parts, which help both the end user and the local econoy Battery Charge Control The battery charger needs to supply the battery with the appropriate voltage and current to safely and efficiently charge the battery. The charging syste also prevents the battery fro overcharging. The tea has not yet selected a specific design for battery charge control. Epower plans to design the syste based on experiental data fro the flutter band prototype Voltage Step-up Before inverting, it is necessary to step-up the voltage fro the battery. This will be accoplished using a DC/DC Boost converter, such as the Linear Technology 5

30 LT348. This will step the voltage up to approxiately 90 volts to allow ore flexibility in the actual inverter stage Inverter The tea has decided to use pulse width odulation to control the AC wavefor. This is a coon ethod used in industry and has a wide range of applications beyond power systes. Moreover, PWM gives the tea controllability that soe of the other ethods lack. This will allow for easier adjustent in the prototyping process Voltage Transforer To achieve the required 0/30 VAC at 50 H, the tea has decided to use a transforer. While larger and ore bulky than an integrated circuit, the transforer offers a nuber of advantages over switching circuits. First, transforers are coon, and are uch ore likely to be available locally in South Africa. Transforers can be built fro car alternators, and are found in any older electronic appliances such as icrowaves and televisions. Second, transforers will provide isolation between the load and the PCAD syste Storage Syste Lead acid batteries are the best choice for the application needed in the sall-scale power syste. Lead acid batteries are widely available and relatively inexpensive copared to other battery types. The cost of the battery is the ost expensive coponents of the syste so by lowering the cost of the energy storage device the syste will be usable for ore people. As Christian engineers, Epower seeks to help as any people as it can, so low costs are critical. The sie and weight of lead acid batteries are not a proble for this application. The battery part of the syste is not intended to be oved around frequently and so saller denser energy devices that are ore expensive are not necessary. 6

31 Additionally lead acid batteries are able to be charged and discharged ore than other batteries. The ability to charge and discharge frequently adds to the batteries life. Having a syste that is robust and will last for as long as possible is iportant. 7. Syste Paraeters 7.1. Charging Magnet/Coil paraeters Initial design criteria for the agnet and coil configuration consisted of the placeent and otion of the agnet relative to the coil. The two configurations considered are shown in Figure 9. Figure 9: The two priary agnet/coil configurations studied for the charging device. (a) agnet oscillation parallel with coil. (b) Magnet oscillation perpendicular to coil. Equations were developed to calculate the power generation of each configuration as a function of tie. Exaple calculated power output is shown in Figure 10. 7

32 Power( t) 0 W s Figure 10: Power generated as a function of tie. Analysis showed that configuration (b) in Figure 9 produced the greatest power output with the sae input paraeters for both configurations. As a result paraeter optiiation was conducted using configuration (b). See Appendix C: for the derivation of the power equations and power analysis for each configuration. Equations were then developed to calculate the power generation in the coil (in watts) as a function of: -The radius of the agnet -The thickness of the agnet -The nuber of loops of wire in the coil -The gauge of the copper wire in the coil -The frequency of the flutter band otion (deterined by prototyping) -The aplitude of the flutter band otion (deterined by prototyping) These equations were then optiied to deterine the agnet and coil necessary for the design. Optiiation work was conducted in accordance with Epower s desire to be transparent about design decisions and good stewards of liited resources. By optiiing design for coponents as siple as agnets and copper coil Epower is ensuring that it is designing the ost efficient syste possible. Optiiation of the agnet paraeters included aterial selection, and agnet thickness and radius (assuing a disk shape agnet). Several options exist for the choice of agnetic aterial as shown in Figure 11. t 8

33 Magnet Type Coposite Ceraic or Ferrite Alnico Ticonal Earth Saariu- Cobalt Neodyiu-Iron-Boron (NIB) Figure 11: Magnetic Material Options For use in the charging device two agnet options were considered: ceraic and NIB. These two options seeed ost viable because of their aterial properties, as shown in Table 5. Table 5: Material Properties of NIB and ceraic agnets NIB Ceraic Corrosive Highly, unless coated Not very with nickel or plastic Strength MA/ on average 100 ka/ on average Brittle Quite Quite Cost $44/kg (008) 1 $5/kg Based on the required power output of the design NIB agnets were selected. The high strength of the aterial greatly increases the power generation of the syste. 1 Neodyiu Magnets. Wikipedia. 16 Nov. 008 < Magnet Price Perforance Princeton Electro-Technology, Inc. 16 Nov < 9

34 The actual agnet used in the design was selected fro the NIB agnets available fro Epower s supplier. 3 Power calculations were ade with each agnet to deterine the levalied power generation of each agnet in Watts/Cost/agnet Paraeters for the copper coil design included wire gauge and nuber of coil turns. Typical wire used for this type of application is 0 30 gauge. Epower found that a larger wire diaeter (saller wire gauge) allows for exponentially larger power generation. The nuber of coil turns is the variable which will be used in the flutter band prototyping for echanical ipedance atching; ensuring that the axiu aount of power on the band can be converted to electrical power. Turns will be added to the coil during prototyping to generate as uch electrical power as possible at the flutter band operating paraeters. See Appendix D: for optiiation calculations Flutter band paraeters The design of the charging syste capitalies on the energy that can be harvested fro aeroelastic flutter. Design paraeters of the belt include: Material Width Length Thickness Tension Based on the experience of Hudinger Wind Energy group, the flutter band length should be no greater than eters. This is due to increased noise pollution with band length. Hudinger also recoends Mylar coated Taffeta for band aterial. They have experiented with nuerous aterials and have found this to be the ost reliable aterial for the design. The flutter band s wind-to-electrical energy efficiency is based on a prototype developed by Hudinger Wind Energy group and is roughly 9.5%. Assuing this efficiency and the charging syste s specified 50 W output rate, rough calculations show

35 that about 39 bands would be required for the charging syste. These calculations are based on a 1 eter band length with an expected oscillation agnitude of 7.5 c (as specified by Hudinger Wind Energy) and an assuption that all bands generate power at the sae rate at an average wind speed of 13 knots. Average wind speeds in South Africa are discussed in section 5.1. See Appendix E for band power calculations. Because aeroelastic flutter is highly nonlinear, the band s otion is hard to accurately odel using equations. The approach of Epower will be to use a siple ode 1-3 odel of the otion of the belt. Epower will also work with prototyping to confir the accuracy of the odel and prove the power output of the syste. Band paraeters of width and tension will be deterined over the reainder of the school year via prototyping and odeling. 7.. Power Condition and Distribution Syste Cost The load interface syste needs to be siple and cost-effective. Though inverters, power regulators, and other systes are available coercially for distributed-generation and off grid applications, these products would be too expensive for the end user s of Epower s syste. The following list of coponents will be useful in the interface circuitry: Rectifiers Voltage control o Boost Circuits o Transforers o Pulse Width Modulation Fuses Switches 31

36 7... Efficiency Efficiency will be a key factor in deterining the feasibility of various interface options. With each step in the regulation and transforation process, energy is lost and so efficiency decreases Flexibility Epower seeks to design a flexible load interface syste. This will allow the end user to power a wide variety of loads and use the syste as local needs require. Additionally, because of the experiental nature of the wind belt, the interface syste needs to be flexible so that it can be integrated throughout the prototyping stage. An effective interface will allow for ore holistic debugging of the syste Capture/Storage/Discharge connection options The syste has a nuber of potential options for connecting the charging, storage, and load portions. Directly connecting the charging source to the load would provide axiu efficiency, but would also severely liit flexibility. On the other hand, connecting the syste to a storage syste, and powering the load via regulation of the stored energy would have the ost flexibility but would liit efficiency Nuber of Capture/Storage/Discharge connections The nuber of capture, storage, and discharge connections will depend on the nuber of capture, storage, and discharge pieces. One energy storage device will probably suffice, and will help to siplify the design. However, there will likely be a nuber of charging sources (i.e. ultiple flutter bands), and the final design will need to account for issues of different phases, haronics, voltages, and current levels associated with each of these bands. The syste will be able to deliver 150 W, however, the user will be able to power ultiple loads, such as two 60 W light bulbs. The design should support any load requiring less than 150 W. 3

37 AC/DC Initially, Epower wanted to provide both AC and DC outputs with ultiple voltage levels. However, after corresponding with contacts in South Africa, considering the custoer profile, and receiving advice fro their advisor, Epower feels that it would better serve the custoer to have a siple inexpensive syste. Therefore, the final design will only support the 0/30 VAC at 50 H that is standard in South Africa. This will eet the end users needs while keeping costs down. Although less flexible, this decision will allow Epower to design a syste that is accessible to ore people Regulations and Standards There are a nuber of standards and regulations guiding the design and installation of power systes. Safety and reliability are both high priorities for Epower, and so by adhering to codes and standards, the design tea will ensure a good final design. A nuber of codes and standards will be used as guidelines. IEC SANS 6104, Protection of structures against lightning Part 1: General principles. IEEE Energy storage syste The sall-scale power syste has a target output of 150 Watts for 3 hours. This results in using 450 Watt/hours of energy needed. When the battery is discharged there will be soe energy lost due to inefficiencies in inverting the power to an AC signal. If the discharging syste can achieve 90% efficiency the resulting energy needed to be discharged fro the battery would be 500 Watt/hours. To axiie the life of the battery the battery should only be partially discharged before being recharged. A typical deep cycle lead-acid battery should not be discharged ore than 50%. Discharging the battery to 50% and still getting 500 Watt/hours out of it would result in needing a 1000 Watt/hour battery. 33

38 8. Preliinary Design 8.1. Charging syste The agnets used for the design will be Neodyiu Iron Boron and will have a diaeter of 0.5 inches and a thickness of 0.5 inches. The copper coils used for the design will be gauge and will have an expected 00 turns. The flutter band will be ade of Mylar co ated Taffeta and will have a thickness of The band length will be 1 eter. The width and tension of the flutter band will be deterined over the reainder of the school year through prototyping and odeling. Preliinary design of the charging syste layout is as shown in Figure 1. Figure 1: Charging Syste Layout The charging syste clearly is feasible, as ore bands can always be added until a power generation rate of 50 W is achieved. The practicality of such syste, however, is to be deterined by the design work this year. To decrease the total nuber of bands needed Epower will have to axiie the power generation of each band by axiiing band length (until noise is too large a factor), band otion aplitude, and 34

39 power conversion efficiency. Furtherore, designing the syste for a location in South Africa having higher average wind speeds ay be another option for reducing the required nuber of bands. By cobining band otion odeling and prototyping Epower will use the design nors to work over the course of the year to increase the axiu power generation of each band and develop a practical charging syste design. 8.. Power Conditioning and Distribution syste The tea will be finaliing the PCAD design during Interi of 009, whe n the electrical ebers of the tea will be taking ENGR-W83 Intro. to Power/Energy Systes. In this class the tea hopes to odel and siulate the PCAD syste. As shown in Figure 8, the tea has a block diagra for the electrical syste design. More specifics for the workings of this block diagra are provided in the following section. Figure 13 shows the circuit diagra for the voltage transforation and rectification fro the power grid. AC Grid Input DC Output Figure 13: Grid Input Power Supply Figure 14 shows the scheatic diagra for a Boost DC-DC converter. 35

40 Figure 14: Boost DC-DC Converter The control of this circuit will be provided by a PWM controller, such as the ON Seiconductor NCP The other integrated circuit used in the design will be the Linear Technology LT348 90V Boost DC/DC Converter with APD Current Monitor. 5 This will provide the needed voltage step fro the battery to the inverter circuit Storage syste The goal for the sall-scale power syste resulted in the need for a battery with 1000 W/hr of energy. This is equivalent to an 83 A/hr battery if the battery is at 1V. Batteries of this sie are widely available but typically cost $30-$50 ore than the target cost of $80 for the energy storage device. The sie of the battery could be reduced by increasing the depth of discharge of the battery. By discharging the battery ore a saller battery could be used, aking the battery eet the target cost. But by increasing the aount the battery is discharged the life of the battery is decreased. So if the custoer intends to use the syste for a short period of tie or the custoer is willing to periodically invest in a new battery, the lead acid battery syste would be financially feasible. The battery syste could also work if the custoer is willing to invest ore oney initially to purchase the higher capacity battery. 4 "NCP1603 PFC/PWM Cobo Controller with Integrated High Voltage Startup and Standby Capability." ON Seiconductor. Apr On Seiconductor. 5 Dec. 008 < 5 "LT348 90V Boost DC/DC Converter with APD Current Monitor." Linear Technology Linear Technology. 5 Dec. 008 < 36

41 9. Intellectual Property 9.1. Charging Syste Previous Work The use of aeroelastic flutter for energy harvesting is a relatively new concept. This is priarily due to the belief that prolonged periods of fluttering would ultiately lead to the destruction of the airfoil. Patent 6,73,680 in class 416/79, 416/81 was filed by Lee Arnold on March, This device is for extraction of energy fro flowing fluids, and its design is shown in Appendix F: Patent 6,73,680 for extraction of energy fro flowing fluids This design uses the sae concept as Epower with aeroelastic flutter of an airfoil. However, Epower does not foresee any patent infringeent issues for two reasons. First, patent 6,73,680 has shaft work as an output instead of electrical power. Second, because patent 6,73,680 uses shaped and ostly rigid airfoils as oppose to a flexible band aterial with a rectangular cross section Current Siilar Projects Epower s design concept of using aeroelastic flutter as an energy-harvesting device capitalies on the design of the Windbelt invented by Shawn Frayne of Hudinger Wind Energy, LLC. Hudinger s designs are currently patent pending in the United States. The legal notice given by Hudinger Wind Energy is: The windbelt technology has U.S. and PCT patents pending. The intent is to license the intellectual property within the US, Gerany, and Japan in the new sector of consuer level wind power using wind power to run applications such as wireless sensor nodes. This will generate the funds necessary to travel the uch longer road of building an international business for the windbelt in developing countries. However, because of the one-nation nature of patents, anyone working outside of these patent pending countries is free to refine, use, anufacture, and sell the technology. For the work that IDDS is focused on, this eans the technology is open source and 37

42 free to replicate, iprove, sell, etc. in virtually all developing countries Future Ties to our project Because Epower seeks to anufacture and distribute the flutter band power syste in South Africa, patents attained by Hudinger will not be applicable for this project. Modifying and experienting over the course of this year at Calvin College is also perissible by patent law under the educational clause. Therefore, Epower foresees no patent infringeent issues with the developent of this technology, but will seek to have transparency in syste design to prove the designed syste does not infringe on the rights of patent owners 9.. Power Condition and Distribution Syste A nuber of systes exist for controlling voltage output fro various distributed generation and off grid applications. Many of these systes have patents to protect their intellectual property; however, none of the systes found dealt with low cost, low power systes such as the one Epower is designing. All of the systes found dealt with either a large nuber of controllers or very high accuracy relating to specific applications such as telecounications or coputer power supplies. As such, Epower does not believe that there is any legal intellectual property restriction on the load interface syste. As the syste is refined, further research will be needed to ensure that no infringeents take place. Classes that related to power conditioning and distribution systes can be seen in Appendix G: Charging Syste Related Patents. 10. Project Manageent Project Tietable Appendix H contains the project s Gannt chart for this seester. The Figure 15 displays how the reaining echanical work will be perfored for the reainder of the year. 6 Tech Brief. Hudinger Wind Energy Group. Dec. 008 < 38

43 Figure 15: Upcoing Mechanical Work The next step for the electrical work will be perfored during interi as part of the special topics class on power systes. The tea plans to odel and siulate the PCAD syste, as well as finalie the design and order coponents. 11. Projected Costs Labor Hours The nuber of hours worked to date by Epower is shown in Table 6. Table 6: Labor Hours and Cost Labor Cost [$/hr] Hours of work Total Cost [$] , Charging Syste Bill of Materials Costs for the charging syste will be delegated on a per flutter band basis, as shown in Table 7. Table 7: Charging Syste Bill of Materials Unit Quantity Total Coponent Description Cost [$] per band Cost [$] Magnet NIB, ½ diaeter, ¼ thickness Copper Wire -gauge, expected length /