Wind Turbine Design and Implementation Final Design Report Team Members: Pranav Boda Fairman Campbell Jennifer Long MIlki Wakweya Advisor & Client: Dr. Venkataramana Ajjarapu DISCLAIMER: This document was developed as a part of the requirements of an electrical and computer engineering course at Iowa State University, Ames, Iowa. This document does not constitute a professional engineering design or a professional land surveying document. Although the information is intended to be accurate, the associated students, faculty, and Iowa State University make no claims, promises, or guarantees about the accuracy, completeness, quality, or adequacy of the information. The user of this document shall ensure that any such use does not violate any laws with regard to professional licensing and certification requirements. This use includes any work resulting from this student-prepared document that is required to be under the responsible charge of a licensed engineer or surveyor. This document is copyrighted by the students who produced this document and the associated faculty advisors. No part may be reproduced without the written permission of the senior design course coordinator. 12/11/29
Table of Contents Pg. 1. Introduction 4 1.1 Executive Summary and Problem Statement 4 1.2 Proposed Solution 4 1.3 System Description 4 1.4 Operating Environment 5 1.5 Intended User and Uses 5 1.6 Risks 5 1.7 Market & Literature Survey 6 2. Design 7 2.1 System Requirements 7 2.1.1 Functional Requirements 7 2.1.2 Non- Functional Requirements 7 2.2 Concept Sketch 8 2.3 System Block Diagram 9 2.4 Component Design 9 2.4.1 Air-X Turbine 9 2.4.2 Outback Inverter 1 2.4.3 Battery Bank 1 2.4.4 Sensing Circuits 12 2.5 Interface 13 3. Implementation and Testing 17 3.1 Turbine, Battery and Inverter 17 3.2 Sensing Circuits 18 3.3 Interface 18 2
3.4 Sensors and Interface 18 3.5 Entire System 18 4. Deliverables 19 5. Financial Details 19 5.1 Earned Value Analysis 19 5.2 Material Cost 2 5.3 Financial Report 21 6. Work Breakdown 22 7. Lessons Learned and Conclusions 23 Appendix 24 3
1. Introduction 1.1 Executive Summary and Problem Statement In 28, President Geoffrey introduced the Live green program, which called for environmentally conscious living. In light of this initiative, it was decided to actively assemble a wind turbine that would supply power to Coover hall and reduce our carbon footprint. The goal of our project is to install and implement a wind turbine system into the Coover Hall grid. The project also includes making the necessary circuits to make the power generated by the turbine gird compatible. In addition to this, we will measure various parameters and display them via a visual interface developed by us. The purpose of the project s is to make a functional system which has practical value and also educational value. 1.2 Proposed Solution In response to the goal of the project we decided to make this project an on-going project. The system is designed to produce 12 watts when all phases are completed but during our phase, the output will be 4 watts. The turbine is an AIR X permanent magnate generator. The inverter is an OUTBACK grid tie inverter with a capacity of 25VA. Our design is focused on sensing and outputting values from the circuits and the interface created by our team. 1.3 System Description The Air-X wind turbine has a permanent magnetic alternator that converts wind energy into mechanical motion. The generator then converts mechanical motion into electrical power. The alternator provides variable frequency and variable AC power, after this it will go into a rectifier that will convert it to DC power of approximately 24V. After the turbine, there will be a fuse that protects the turbine if the current is too high, and after it went through the fuse there should be a switch that turn on and off. Once it goes through fuse and switch, it will go through the battery bank. The battery bank consists of two 12V batteries in series. On the output of the battery bank is the input of the inverter. The inverter will take a 24V DC voltage and convert it to AC 12V at a frequency of 6Hz. Then, the power from the inverter goes into the solid-state relay. The capacity sensor is on the output of the batteries and measures the voltage across the battery, and goes to the control input on the solid-state relay. When the voltage across the battery drops below 23VDC, it will send a signal to the relay to disconnect the inverter from the load. The solid-state relay acts like a switch, and has a DC control input from 5.5V- 1V. After the solid-state relay, the AC power is fed directly to the Coover Hall grid or to an independent load. There will be a current sensor and voltage sensor on the output of the turbine. After the inverter, there will be a current transformer, and it will go into the AC current sensor. We used an independent load like an induction motor that is located in a power lab, or we will connect it to AC load 4
Coover power grid. In the appendix, is a detailed diagram of our system. The AC current, DC voltage, and DC current are all measured, and are inputs to the NI DAQ 68. The NI DAQ 68 then goes to the LabView interface. 1.4 Operating Environment The turbine will be mounted above Coover Hall. It will be subjected to all the elements of Iowa's weather. The extremes of Iowa's weather are ice, wind, rain, heat, and lightning. The turbine itself should be able to withstand all of Iowa's weather but the inverter and battery bank will need to be in a controlled environment. The battery bank in particular will need a specific temperature range to be most effective. This is why both the inverter and battery bank will be placed indoors. 1.5 Intended Users and Uses The turbine will be mounted on the Coover Hall roof. The turbine will service Coover Halls electrical grid and will be used by Iowa State Electrical and Computer Engineering faculty and students. The turbine can be used for research within the university along with undergraduate students for class work. Using the LabView interface users can view the power generated in the past. This design will also serve as a useful educational tool and will enhance one s learning experience. 1.6 Risks & Solutions 1. The tower mounted can t withstand the high wind speed a. Tower will be mounted by professional 2. Battery bank suffers complete discharge a. Inverter has a charger to prevent total discharge b. Capacity sensor will disconnect inverter from the load when batteries get too low 3. Battery bank suffers overcharge a. Turbine has controller that will not allow overcharging 4. LabView interface gets outdated and not sufficient 5. Will not have the turbine mounted on the roof for IRP a. Build stand in Coover 112, and use drill to power turbine 6. Components won t be installed in time 5
a. Assemble mock setup in Coover 112 7. Will not be able to hook up to Coover Hall power grid a. Create a load dump or alternate load to test design on 8. LabView interface gets outdated and insufficient a. Update the interface and excel file. Expand its function 1.7 Market and Literature Survey In today s world, the need for alternative, environmentally friendly energy generation has never been greater. The Department of Energy (DOE) has set plans and taken the initiative to have wind energy account for 2% of total energy generation or 3GW by capacity in the United States by 23. This would cause a huge increase in demand for more efficient wind turbine designs to maximize energy generation while minimizing losses. 6
2. Design The focus of the project was to erect the turbine and design sensing that would output values from the system along with a safe work environment for those working with the system. 2.1 System Requirements The system comprises of Functional and Non-functional requirements that were to be met in this project. These requirements are listed below. 2.1.1 Functional Requirements 1. Produce 4 watts of electrical energy to the Coover Grid at 12 volts with a 6 Hz frequency 2. Convert turbine DC voltage to useable AC voltage 3. Sensing circuits read DC and AC voltages and currents 4. Sensing circuits send information to display on a computer using LabView 5. Protect batteries from total discharge 6. Turbine is mounted high enough to receive non turbulent wind 2.1.2 Non-Functional Requirements 1. All wiring and electrical work complies with university and state electrical codes and regulations 2. Battery bank is in controlled temperature and stable environment 3. Tower mounting complies with building standards 4. Turbine is mounted high enough to allow maintenance to walk under turbine 7
2.2 Concept Sketch Fig-1 8
2.3 System Block Diagram Fig-2 2.4 Component Design The system comprised of purchased and designed components. The component design is comprised of the Air X turbine, Outback Inverter, Battery Bank, and sensing circuits. 2.4.1 Air X Turbine The Turbine we chose to purchase is the AIR X from Southwest power. The picture of the turbine can be seen in the Appendix. The reason we chose this particular turbine was a combination of cost and functionality. The turbine itself cost $7 and produces 4W, at peak power at 28 MPH of wind speed. The power curve can be seen in the Appendix. It produces this power by using a permanent magnet alternator. The power from this alternator is converted from AC to DC with inverter inside the turbine housing. The turbine can output 12 or 24 VDC. We will have the turbine output 24V due to the high current that is produced at 12 VDC. For the functionality side we chose the AIR X because of its control of generator in the turbine. The control will stop the turbine when the wind speed is too great. The Rotor Diameter of the turbine is 46 inches. The start up speed is 7 MPH. The total weight of the turbine including blades is 13 lbs. The diagram of the dimensions of the turbine can be seen in the Appendix. The control will also shut down the turbine when the battery bank is at full charge, protecting the batteries from overcharge. We plan to mount the turbine to the side of Coover to eliminate a major tower design and to increase ease of construction. The wire coming down the side of Coover Hall will be 1-AWG wire. The turbine requires batteries to work properly. If there is no load attached to the 9
turbine, then the positive and negative leads on the turbine must be shorted together. If attached with no load, it can cause permanent damage. We began our search looking at three different turbines. We decided the Air X was the best turbine because it offered the best cost to benefit ratio. The benefits of this turbine are that it is light, relatively small, and controls mechanical failure due to high winds. The cons for this turbine are that it does not come with any type of tower set up as well as an inverter circuit with a display interface. Below is a table for the different turbines that we looked at using. In the appendix, there is a power curve for the turbine, and an exploded view of the Air X Turbine. In the appendix the dimensions of the turbine are given. There is also a picture of the Air X Turbine. Turbine Watts Display Inverter Controller Turbine Type Cost Interface Whisper 1 9 W Yes (optional) Included Speed/ Permanent $ 21 Battery Protection Magnate AIR X 4 W NO Not Included Speed/ Battery Permanent Magnate $7 Wind Max 5 W NO Not Included Protection Speed Permanent Magnate $5 2.4.2 Outback Inverter For our project we are using a Outback GTFX2524 inverter. This inverter is capable of taking 25VA of input and converting it to 12VAC at 6 Hz. The inverter inputs a nominal DC voltage of 24 VDC with a range of 21. to 34 VDC. The idle power that inverter will take is 2 Watts. The inverter has an efficiency of 92 percent at 25 Celsius. Continuous AC RMS output is 2.8 amps AC with a peak of 7 amps AC. The inverter has an AC overload capability of 6 VA. It s sealed with a weight of 56 lbs. and is 13 x 8.25 x 16.5". A picture of the Outback GTFX2524 can be seen in the appendix. 2.4.3 Battery Bank The battery will supply a power to the inverter and to the control system. Also, battery has to be fully charged at all time and the battery bank is expandable so that we can add more batteries to it in the future. For this project we are using flooded lead acid battery. For this project we are using 24volt battery, we bought two 12 volt flooded lead acid batteries and we are connecting them in series to make it 24 volt. 1
Flooded Lead Acid Battery: Wet Lead Acid or flooded lead-acid batteries are the most commonly used batteries to store electrical power. Battery (24volt battery) Type: Flooded Lead acid Battery Two 12 Volt Batteries 2 Ah Fig-3 11
2.4.4 Sensing Circuits DC Current Sensor The DC current from the turbine is measured by using a DC current transducer. The current transducer is made by LEM. It is rated at ±7A. This sensor will measure the current after the fuse. The sensor will output a current of5ma when the input current is 5A. The current transducer has a 1:1 conversion ratio. On the output of the DC current sensor, there is a 1Ω, 1/4W resistor. The current sensor has and ±15V rail is needed for the sensor to run. The voltage is measured across the resistor, and is then connected to the NI DAQ 68, and then displayed on the interface. This sensor has low power consumption, and can handle up to 8-gauge wire. The high current never has to touch the board, so large traces are not necessary. In the appendix, there is a copy of the specifications of the LEM component. DC Voltage Sensor The DC voltage sensor measures the voltage coming out of the turbine. The input should be approximately 24VDC. The DC voltage sensor consists of two resistors in series. It divides the voltage from 24VDC to 5VDC. The resistor values are 1kΩ, and 39kΩ. The resistors are ¼W resistors. The voltage is measured in parallel with the output of the turbine. The power loss is less than 5mW. The output voltage is measured across the 1kΩ resistor. AC Current Sensor After the inverter, there is a current transformer. The purpose of the current sensing circuit is to determine the AC current of the system. The current transformer steps down the current from 1A to 2mA. The circuit is used to ensure that the current limit of the NI DAQ 68 is not exceeded. The current sensing circuit takes the output from the current transformer, and rectifies the signal into DC. The rectified DC is then filtered by the low-pass filter. Then the signal is amplified with an inverting opamp. The current transformer has a 1:5 conversion ratio. The Foster Transformer Company manufactures it. It has a rated current input of.1a-3a. The voltage output is 1mV/A. On the output of the current transformer, we added a 5Ω resistor. We wanted to obtain a 5VAC to go to our current sensing circuit. In the appendix, there are the data specifications of the Foster Transformer. The current sensing circuit consists of a full-wave precision rectifier circuit. The precision rectifier consists of two op-amps, two diodes, and six resistors. The precision rectifier converts the AC input into a DC output. The output of the rectifier has quite a bit of ripple, so it needs to be filtered. Next, there is a low-pass filter. The low-pass filter consists of a 1kΩ resistor, and a 22μF capacitor. After the lowpass filter, the voltage is only 3.2V, and the NI DAQ 68 has an input range from -5V. To boost the voltage up to 5V, there is an inverting op-amp circuit. The op-amps have rails of ±15V. In the appendix, there is the circuit diagram of the current sensing circuit. 12
Capacity Sensor After the battery bank, a voltage divider steps down the battery voltage between zero and five volts. A Schmitt trigger compares the voltage. When the battery voltage drops below 22.5VDC, the output of the Schmitt trigger goes low. The output of the Schmitt trigger goes high again when the battery voltage is above 24VDC. The output goes into the control input of the solid-state relay. The solid-state relay is a switch that connects the inverter to the load. The circuit is used to ensure that the batteries are not depleted too far. If the batteries become too discharged, it can cause irreversible damage to the batteries. In the appendix, there is the circuit diagram for the capacity sensor, and the data sheet for the solid-state relay. A Schmitt trigger is a comparator circuit that incorporates positive feedback. When the negative input is higher 23VDC, the output is high; when the input is below 22.5VDC, the output is low; when the input is between the two, the output retains its value. The comparator we are using is the LM311. The Schmitt trigger s VCC of +15V, and VCC =V. Electrol manufactures the solid-state relay. The solid-state relay needs a heat sink to dissipate the heat, so the metal box will be the heat sink. The solid-state relay has a 1A, 23VAC rating. The DC control input for the relay is from 5.5V-1V. In our system, the control input is 7.4VDC. The relay should only see a 9.8VDC or VDC. To connect the relay to the system, it has quick connected clips on top of the relay. Below is a picture of the relay. Fig-4 http://cgi.ebay.com/ws/ebayisapi.dll?viewitem&item=3162169&rvr_id=&crlp=1_26362_263622&ua=wxf%3f&guid=7a2d5b1125a e22763cffaad8&itemid=3162169&ff4=26362_263622 2.5 Interface The interface used in the project was developed using LabView through a NI 68 data acquisition device (DAQ). The DAQ takes its inputs from the sensors. The DAQ then connects to a computer or laptop via a USB. The interface developed will display real time values of the chosen parameters by reading them continuously. These values are then automatically stored in a spreadsheet for future 13
reference. Below are screenshots of both the system block diagram as well as the front panel of the interface. Fig-5 As we can see due to the size of the block diagram, it was necessary to break it up into multiple screenshots in order to include the entire diagram. In the first screenshot above, we are taking an input via the task created (pranav_task), which goes through the DAQ start and the while which is then connected to the DAQ READ.vi function. This tool reads in the values inputted via the NI 68 USB control. Once the samples itself are read in through the different channels, it is upto us to sort through them and display our chosen values. This was accomplished using an index array. Using this array we were able to read in multiple channels in one task. The first array displays the battery voltage in three forms: numeric indicator, numeric meter and as a waveform plotted against time. The second array outputs a DC voltage which is then converted to a DC current. This DC current is then displayed in the formats as before. The third array displays the output DC voltage in the three formats specified above. The final array outputs a voltage which depending the turns ratio is converted to a an AC current which is again displayed as before. In addition to these measurements we also calculated the instantaneous power by simply using a multiplication function from the functions palette and multiplying the DC voltage and the DC current. 14
Now that we have our various voltages, currents and power calculated and displayed, we move on to writing these values to a spreadsheet. The figure above shows us two of the three while loops created in order to efficiently and accurately display the values in a spreadsheet. Each loop displays a date/time stamp to keep track of the different power generation values throughout any given day. Note that at the top left side of the screenshot we used a file dialog to specify the selected path. Fig-6 15
Below is a sample of our output displayed in the spreadsheet mentioned. As we can see the date/time stamp is displayed in addition to the output power. Fig-7 Fig-8 16
Also included below is the front panel of our project which would be what the user would view when running the program. Each of the parameters is displayed in the three forms.( numeric indicator, numeric meter and as a waveform plotted against time). 3. Implementation and Testing 3.1 Turbine, Battery, and Inverter Turbine & Batteries To test the turbine and batteries, we connected them together, and attached a drill to the rotor of the turbine. The blades were taken off for protection when using the drill. Then, a torque was applied at different RPM s to determine the output power. We measured the current and voltage, and then multiplied the two outputs together to get the instantaneous power. We used a 1-RPM drill, and it produced only 4W. When the turbine is running, the blades are hard to see. We tested the batteries by hooking it up to a load or the wall outlet to make sure it discharged. The batteries were then attached to any power supply to make sure it charges. We used a voltmeter to test the actual voltage of the battery. We tested the Outback inverter by hooking the battery bank to the input of the inverter, and attached a single-phase AC motor as the load. Then we measured the voltage of the system to ensure that the DC is fully converted into AC. Then the load was increased to ensure that the batteries would supply the increased load. 17 Fig-9
3.2 Sensing Circuits Sensors To test the sensors, we used power supplies as inputs, and used an oscilloscope to measure the outputs. Then the outputs were verified to ensure that the sensors were accurately working. When soldering the circuits to the board, a multimeter was used to check connectivity of each line. The output of the DC current sensor was between -5 volts depending on the amount of current passing through the circuit. The output of the DC voltage sensor is around 5VDC. The output of the AC current transformer is between 1.1A-1.5A. The output of the current sensing circuit was 3mV. The oscilloscope output readings of the sensors are shown in the appendix. Capacity Sensing Circuit & Relay To test the battery capacity circuit, a LED was used as the output to verify that the capacity of the batteries is being read properly. When connected to the solid-state relay, the control input was varied to ensure that the control input goes on/off. The output of the capacity sensor will remain high until the battery voltage drops below 23V. The capacity sensor will remain low until the battery voltage rises above 24V. The relay should only see a 9.8VDC or VDC. Then, we verified that the comparator circuit would break the power going to the load. When soldering the circuits, a multimeter was used to check connectivity of each line. The oscilloscope readings of the capacity sensor are shown in the appendix. 3.3 Interface While testing the interface, we used the LabView compiler to verify our design. We also tested and verified our results using DC and AC power supplies in the labs. To ensure that the system as a whole runs smoothly, we used and tested the interface in conjunction with the turbine and sensing circuits and eliminated any glitches and minor errors. 3.4 Sensors & Interface To test the sensor together, attach all the control components to a power supply to ensure that there is no interference with each other. Then a 24VDC, 8A supply was used to test the DC sensors and comparator circuit. In addition, a 12VAC, 5A supply was used to test the AC sensors. To test the sensors and the LabView interface together, they are connected through the NI DAQ 68. Then the program was started, and each output was verified. 3.5 Entire System To test the entire system, we connected the turbine, battery bank, inverter, sensors, and LabView interface together. Then, a drill was applied to the rotor of the turbine, and the interface was monitored to ensure that all the sensors were reading the values correctly. The drill speed was increased and checked that the DC power went up accordingly. The LED on the capacity circuit was monitored to ensure that the relay will disconnect the load from the inverter when the battery voltage becomes too low. 18
4. Deliverables These are the project deliverables: AirX turbine capable of producing 4 Watts Outback inverter capable of converting 25VA of DC to AC Sensing circuitry that can sense DC and AC voltage and current LabView interface which takes its inputs from the sensors LabView data is stored in an Excel spreadsheet for future reference 5. Financial Details 5.1 Earned Value Analysis T-2 Team Member Semester-1 Earned value Semester-2 Earned value Total Earned value Pranav Boda $15*89 $15*57.5 $22 Fairman Campbell $15*85 $15*76.5 $2422 Jennifer Long $15*87 $15*79.5 $246 Milki Wakweya $15*8 $15*44.5 $1867.5 19
5.2 Material Cost Fig-1 2
5.3 Financial Report Fig-11 21
6. Work Breakdown Schedule (Semester 1) Fig-12 Schedule (Semester 2) Fig-13 22
7. Lessons Learned and Conclusions The first lesson we learned in this project was the fact we needed to decide on a plan at the beginning and stick with it. There was far too much indecision to make this as productive as it needed to be. Funds for this project needed to procured more quickly and this was a major setback. The group needed to have a full scale plan for no funding. Once funding was procured the project costs were not assessed correctly and we were found to be vastly under budget. In conclusion, this project had a very large upside that will be seen in later continuations. The group as a whole preformed well given the situations and was able to produce something that can be built on in the future. 23
APPENDIX Fig-14 Turbine Dimensions 24
Fig-15 Exploded View of Air X Turbine Fig-16 Fig-17 http://www.tande.com.tw/rn-wg-manual/airxland-manual.pdf 25
Air X Turbine Fig-18 26
Outback Inverter Fig-19 27
Entire System Testing Fig-2 28
V+ 8 7 4 V+ V- 4 V- V+ 7 7 4 V+ V- Sensor Circuit Diagram AC Current Sensor R2 1k 2 V4 D18 V12 R1 VOFF = 1k VAMPL = 5 FREQ = 6 DC Voltage Sensor 24Vdc ua741 2 D1N914 3 - + U3 2 V7 OS1 OUT OS2 V1 1 6 5 R1 39k R7 1k D17 D1N914 R3 2k V3 2 R5 R4 1k 2k ua741 2 1 - OS1 6 OUT 3 5 + OS2 U4 V2 2 R8 1k C1 22u R9 1k U6 3 5 + OS2 2 - ua741 2Vdc V6 2Vdc 6 OUT 1 OS1 V5 R11 3k 22 Battery Capacity Circuit V7 R1 1k R2 2.2k 3.67VDC V6 R7 1k 15Vdc V2 R4 3 R6 1k U1 2 6 + B/S 7 OUT 3 - G 1 4 LM311 V- R5 1k Vdc V1 B 5 V R3 1k Sensor Testing Oscilloscope Outputs DC Voltage Sensor Fig-21 Fig-22 29
DC Current Sensor Fig-23 AC Current Sensor (After Rectifer) Fig-24 3
AC Current Sensor (Output) Fig-25 Capacity Sensor Fig-26 31
LEM 55-p DC Current Sensor Fig-27 32
NI 68 USB Fig-28 Specifications: 8 analog inputs (12-bit, 1 ks/s) 2 analog outputs (12-bit, 15 S/s); 12 digital I/O; 32-bit counter Bus-powered for high mobility; built-in signal connectivity OEM version available Compatible with LabVIEW, LabWindows/CVI, and Measurement Studio for Visual Studio.NET NI-DAQmx driver software and NI LabVIEW SignalExpress LE interactive data-logging software 33
Foster Transformer: Current Transformer Data Sheet Fig-29 34
List of Figures and Tables Figures: Fig-1 Pg: 8 Fig-2 Pg: 9 Fig-3 Pg: 1 Fig-4 Pg: 11 Fig-5 Pg: 13 Fig-6 Pg: 14 Fig-7 Pg: 15 Fig-8 Pg: 16 Fig-9 Pg: 16 Fig-1 Pg: 17 Fig-11 Pg: 2 Fig-12 Pg: 21 Fig-13 Pg: 22 Fig-14 Pg: 22 Fig-15 Pg: 24 Fig-16 Pg: 24 Fig-17 Pg: 25 Fig-18 Pg: 25 Fig-19 Pg: 26 Fig-2 Pg: 27 Fig-21 Pg: 28 Fig-22 Pg: 29 Fig-23 Pg: 29 Fig-24 Pg: 3 Fig-25 Pg: 3 Fig-26 Pg: 31 Fig-27 Pg: 31 Fig-28 Pg: 33 Fig-29 Pg: 34 Tables: T-1 T-2 35