Multi-Disciplinary Senior Design Conference Kate Gleason College of Engineering Rochester Institute of Technology Rochester, New York 14623 Project Number: 12441 Thermoelectric Power Pack for Next Generation Cook Stove Andrew Phillips/Electrical Engineer Lauren Cummings/Electrical Engineer Colin McCune/Electrical Engineer Xiaolong Zhang/Electrical Engineer Abstract A thermoelectric power pack was designed and built with the goal of coupling it to an existing cook stove. The stove utilizes air flow generated by a fan in order to be more fuel-efficient and reduce emissions. A thermoelectric generator (TEG) is employed to harvest energy by use of the temperature difference created by the fire and the fan. The purpose of the power pack is to take the energy from the TEG and use it to provide power to the fan and also to a USB, which can be used to charge cell phones and other electronic devices. 1
Transcript
Multi-Disciplinary Senior Design ConferenceKate Gleason College of Engineering
Rochester Institute of TechnologyRochester, New York 14623
Project Number: 12441
Thermoelectric Power Pack for Next Generation Cook Stove
Andrew Phillips/Electrical Engineer Lauren Cummings/Electrical Engineer
Colin McCune/Electrical Engineer Xiaolong Zhang/Electrical Engineer
Abstract
A thermoelectric power pack was designed and built with the goal of coupling it to an existing cook stove. The stove utilizes air flow generated by a fan in order to be more fuel-efficient and reduce emissions. A thermoelectric generator (TEG) is employed to harvest energy by use of the temperature difference created by the fire and the fan. The purpose of the power pack is to take the energy from the TEG and use it to provide power to the fan and also to a USB, which can be used to charge cell phones and other electronic devices.
Introduction
Background
The use of open fires and inefficient stoves as cooking and home-heating devices is prevalent in many areas of the world, with 3 billion people using them regularly. The fuel source for these devices is typically biomass (wood, animal dung, crop waste) or coal. The use of these devices indoors causes
concentrated air pollution, which can be fatal to those who are regularly exposed to it. Almost 2 million people die each year as a result of illness stemming from indoor air pollution. Poor ventilation can also cause the problem to be further exasperated, with indoor smoke levels as large as 100 times higher than acceptable levels for small particles [1].
A further characteristic of these types of heating methods is that because they are
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inefficient, they require a large amount of these biomass fuels to run. A great deal of time and effort is required to gather the fuel necessary for heating and cooking. The use of so much fuel can also be damaging to a region’s ecosystem.
This environmental impact is particularly evident in Haiti. While 90 years ago 60% of Haiti was covered in forests, today this number has decreased to less than 2%. This deforestation has caused soil erosion and a resulting reduction in agricultural yields. Deadly landslides are also a concern. Wood and coal continue to be used as a primary source of fuel in Haiti, which is becoming a growing issue as these resources are being exhausted at a fast pace. The problem of developing alternative fuel sources and more efficient means of utilizing current fuel sources continues to be a growing concern for Haiti [2].
One strategy for developing more efficient combustion of fuel is by adding oxygen to the combustion process through the use of a fan. As it is expected that this stove will be used in areas that do not have ready access to an external power source, another source of energy is required.
A thermoelectric generator (TEG) is one such device that can be designed to provide power to the system. The TEG functions by use of the Seebeck Effect, whereby a temperature difference can be directly converted into a source of electricity.
A diagram of a typical TEG is shown in Figure 1. The TEG is made up of multiple p- and n-type semiconductors, which are arranged in pairs known as thermocouples. The pairs are connected to each other by metal interconnects. When a temperature difference
is maintained across the two ceramic surfaces of the TEG, this creates a flow of electrons which in turn create a temperature difference and in turn creates electrical power. One advantage of the TEG is that it does not utilize any moving parts to achieve this, minimizing the risk of malfunction.
Figure 1Thermoelectric Generator [7]
Device Charging via USB
The TEG is also important to the stove system as some of the power it supplies can be used to charge external devices through a USB. This feature is used to provide additional value to the system. Haiti has a history of destructive earthquakes and in January 2010 it was struck by a 7.0 magnitude earthquake. The capital, Port-au-Prince was devastated by the quake and now has no power grid and no landlines. While cell phones and radios are the main means of communication in Haiti, there are few available methods for charging these devices. It is not uncommon for a person to have to travel tens of miles and wait in a line in order to charge their cell phone [6]. The integration of a USB charging port into the stove system will help to mitigate this problem while making the stove more appealing to prospective customers.
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General Requirements
This project was designed with the target market of Haitian street vendors, so certain desired characteristics were kept in mind during the design process. Haiti is the poorest country in the Western Hemisphere with 80% of the population living under the poverty line and 54% of the population in abject poverty. Most Haitians live on less than $2 a day [6], so it was important that the finished project be within the budget of the target customer ($15 for the power pack). It was also desired that the device be user-friendly with minimal interaction required to maintain proper function, and that the unit had a rugged enough design that it would have at least a 5-year lifespan and be operational outdoors (surviving rain and humidity).
Design Process
Complete System Overview
A general system functionality overview for the power pack is shown in Figure 2. Figure 3 displays the complete system schematic designed to carry out these functions. Each section of the circuitry will be described in detail in the subsections that follow.
As Figure 2 shows, energy first flows into the power pack system from the TEG. The energy then flows into the MPPT circuitry, which is designed to harvest the maximum power possible from the TEG. Next the energy is stored in a battery, where it can be applied to power the fan and/or charge the USB output.
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Figure 2Block Diagram of Electrical System
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Figure 2Block Diagram of Electrical System
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Figure 2Block Diagram of Electrical System
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Figure 2Block Diagram of Electrical System
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Figure 2Block Diagram of Electrical System
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Figure 2Block Diagram of Electrical System
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Figure 2Block Diagram of Electrical System
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Figure 2Block Diagram of Electrical System
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Figure 2Block Diagram of Electrical System
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Figure 2Block Diagram of Electrical System
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Figure 2Block Diagram of Electrical System
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Figure 2Block Diagram of Electrical System
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Figure 2Block Diagram of Electrical System
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Figure 2Block Diagram of Electrical System
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Figure 2Block Diagram of Electrical System
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Figure 2Block Diagram of Electrical System
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Figure 2Block Diagram of Electrical System
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Figure 2Block Diagram of Electrical System
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Figure 2Block Diagram of Electrical System
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Figure 2Block Diagram of Electrical System
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Figure 2Block Diagram of Electrical System
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Figure 2Block Diagram of Electrical System
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Figure 2Block Diagram of Electrical System
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Figure 2Block Diagram of Electrical System
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Figure 2Block Diagram of Electrical System
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Figure 2Block Diagram of Electrical System
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Figure 2Block Diagram of Electrical System
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Figure 2Block Diagram of Electrical System
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Figure 2Block Diagram of Electrical System
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Figure 2Block Diagram of Electrical System
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Figure 3Circuitry of Complete Power Pack
System
Figure 4Current vs. Voltage plot of TEG at various temperature
differences with different loads attached
Figure 3Circuitry of Complete Power Pack
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Figure 3Circuitry of Complete Power Pack
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Figure 3Circuitry of Complete Power Pack
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Figure 3Circuitry of Complete Power Pack
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Figure 3Circuitry of Complete Power Pack
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Figure 3Circuitry of Complete Power Pack
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Figure 3Circuitry of Complete Power Pack
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Figure 3Circuitry of Complete Power Pack
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Figure 3Circuitry of Complete Power Pack
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Figure 3Circuitry of Complete Power Pack
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Figure 3Circuitry of Complete Power Pack
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Figure 3Circuitry of Complete Power Pack
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Figure 3Circuitry of Complete Power Pack
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Figure 3Circuitry of Complete Power Pack
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Figure 3Circuitry of Complete Power Pack
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Figure 3Circuitry of Complete Power Pack
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Figure 3Circuitry of Complete Power Pack
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Figure 3Circuitry of Complete Power Pack
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Figure 3Circuitry of Complete Power Pack
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Figure 3Circuitry of Complete Power Pack
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Figure 3Circuitry of Complete Power Pack
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Figure 3Circuitry of Complete Power Pack
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Figure 3Circuitry of Complete Power Pack
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Figure 3Circuitry of Complete Power Pack
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Figure 3Circuitry of Complete Power Pack
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Figure 3Circuitry of Complete Power Pack
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Figure 3Circuitry of Complete Power Pack
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Figure 3Circuitry of Complete Power Pack
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Figure 3Circuitry of Complete Power Pack
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Figure 4Current vs. Voltage plot of TEG at various temperature
differences with different loads attached
Figure 4Current vs. Voltage plot of TEG at various temperature
differences with different loads attached
Figure 4Current vs. Voltage plot of TEG at various temperature
differences with different loads attached
Figure 4Current vs. Voltage plot of TEG at various temperature
differences with different loads attached
Figure 4Current vs. Voltage plot of TEG at various temperature
differences with different loads attached
Figure 4Current vs. Voltage plot of TEG at various temperature
differences with different loads attached
Figure 4Current vs. Voltage plot of TEG at various temperature
differences with different loads attached
Figure 4Current vs. Voltage plot of TEG at various temperature
differences with different loads attached
Figure 4Current vs. Voltage plot of TEG at various temperature
differences with different loads attached
Figure 4Current vs. Voltage plot of TEG at various temperature
differences with different loads attached
Figure 4Current vs. Voltage plot of TEG at various temperature
differences with different loads attached
Figure 4Current vs. Voltage plot of TEG at various temperature
differences with different loads attached
Figure 4Current vs. Voltage plot of TEG at various temperature
differences with different loads attached
Figure 4Current vs. Voltage plot of TEG at various temperature
differences with different loads attached
Figure 4Current vs. Voltage plot of TEG at various temperature
differences with different loads attached
Figure 4Current vs. Voltage plot of TEG at various temperature
differences with different loads attached
Figure 4Current vs. Voltage plot of TEG at various temperature
differences with different loads attached
Figure 4Current vs. Voltage plot of TEG at various temperature
differences with different loads attached
Figure 4Current vs. Voltage plot of TEG at various temperature
differences with different loads attached
Figure 4Current vs. Voltage plot of TEG at various temperature
differences with different loads attached
Figure 4Current vs. Voltage plot of TEG at various temperature
differences with different loads attached
Figure 4Current vs. Voltage plot of TEG at various temperature
differences with different loads attached
Figure 4Current vs. Voltage plot of TEG at various temperature
differences with different loads attached
Figure 4Current vs. Voltage plot of TEG at various temperature
differences with different loads attached
Figure 4Current vs. Voltage plot of TEG at various temperature
differences with different loads attached
Figure 4Current vs. Voltage plot of TEG at various temperature
differences with different loads attached
Figure 4Current vs. Voltage plot of TEG at various temperature
differences with different loads attached
Figure 4Current vs. Voltage plot of TEG at various temperature
differences with different loads attached
Figure 4Current vs. Voltage plot of TEG at various temperature
differences with different loads attached
Thermoelectric Generator
Tests were performed on the TEG in order to gain an understanding of its functionality. Various temperature differences were applied to the TEG in order to observe the resulting available output power. A plot of the results of these tests is shown in Figure 4.
Maximum Power Point Tracker (MPPT)
In order to obtain the maximum power possible from the TEG, an MPPT was used by implementing a divide-by-two algorithm. We can represent the internal resistance of the TEG as RS and the open circuit voltage across the TEG (due to the temperature difference) as VOC. The MPPT input voltage and current can be represented as VTEG and ITEG, respectively. The output power of the MPPT can then be found [3]:
Therefore, it is known that the maximum output power will correspond with an input of half of the open circuit voltage [3]:
The divide-by-two algorithm functions by sampling the output voltage from the TEG and applying the appropriate load current to maintain half the open circuit voltage at the output of the TEG.
The two main options for implementing the MPPT technique were by analog circuitry or via a microcontroller. It was determined that implementation via a microcontroller would cost at least twice as much as an analog circuit and would also be difficult to repair in the field, and therefore the MPPT was designed using
analog circuitry. A previous successful implementation of MPPT via analog circuitry [3] was used as a starting point for the design of this system. Figure 5 displays the schematic for the MPPT circuitry developed for this project.
Figure 5MPPT Analog Circuitry Schematic
In addition to the divide-by-half output, it is required that the MPPT circuitry provide a steady output of 6.5 V regardless of input voltage. For this reason a comparator, as well as buck and boost converters, are included in the MPPT design to adjust the voltage as necessary.
Fan Converter
The circuitry to power the fan was designed around the fan chosen by the Stove Team. The fan chosen required that it be supplied with 1.2 W and 12 V. The circuitry designed to fulfill these requirements is shown in Figure 6. A DC-DC switching topology was chosen because of its high efficiency, low cost, and small footprint.
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Figure 6Fan Converter Circuitry Schematic
USB Converter
The requirements given for the USB were that it be able to charge 2 cell phones over the course of 1 cook cycle (a cook cycle is defined as starting the stove, maintaining it at the desired cooking temperature for 2 hours, and then turning the stove off). The USB charger was designed to adhere to the USB 2.0 charging standard. To meet this standard the USB output must be 5V ±5%, support up to 0.5A, the data pins must be grounded, and the system must support short circuit protection. The schematic of the USB converter used in the power pack design is shown in Figure 7.
Figure 7USB Converter Circuitry Schematic
Battery
There are two requirements of the battery. The first is that the battery is able to charge two cell phones via USB without the stove being on. The second is that the stove is able to go through three start-restart cycles without being completely discharged. Therefore, a Panasonic LC-R064R5P Lead Acid battery was chosen for the design because of the high storage capacity, low cost and the simple charging algorithm.
In order to design parts of the system around the battery, the discharge curve of the battery was determined through testing. Details of these testing procedures can be found in the Appendix. The plot of the battery’s discharge curve is shown in Figure 8.
Due to the requirement of performing three cold starts in a row, the battery could not be depleted so much during operation that it would not be able to start and power the fan during the warm-up cycle. With this in mind, the circuit was designed to automatically disable the USB output if the battery voltage drops below 5.9 V, and disconnect the fan from the battery if the battery voltage drops below 5.7 V.
A further concern with the battery is overcharging. If the battery is overcharged, it could become damaged and lose functionality. For that reason the battery was designed to automatically disconnect from the charging circuit if its voltage reaches 6.2 V.
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Results/Discussion
Subsystem Tests
Test procedures were written for the individual subsystems of the power pack unit to determine if they met the electrical specifications as laid out in the design process. A brief description of these electrical test procedures is shown in Table 2 below. A detailed description of these test procedures can be found in the Appendix.
At this time several of the electrical test procedures have been performed on the system. The HVLV Disconnect test was run and it was found that the system disconnected at a low voltage of 5.7 for the USB, 5.9V for the Fan and 6.4V for the battery, as was desired. The fan and USB converters were also tested with success. The specific results of these tests can be found in the Appendix.
Customer Acceptance Tests
A Customer Acceptance Test procedure has also been written to determine if the entire system has met the engineering specifications. A detailed description of this procedure can be found in the Appendix. At this time the full procedures have not been performed. However, preliminary tests on the entire system have been carried out using the same test set up as shown in the Customer Acceptance Test Procedure. Plots of the current, voltage, and power at different points in the system can be seen in Figures 9, 10, and 11, respectively.
The results of this test revealed that the system is able to power a fan and charge a device via USB. However, the MPPT circuitry is currently not functioning properly and could affect the functionality if this test were carried out over a longer period of time.
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Figure 8Battery Discharging Curve
Figure 8Battery Discharging Curve
Figure 8Battery Discharging Curve
Figure 8Battery Discharging Curve
Figure 8Battery Discharging Curve
Figure 8Battery Discharging Curve
Figure 8Battery Discharging Curve
Figure 8Battery Discharging Curve
Figure 8Battery Discharging Curve
Figure 8Battery Discharging Curve
Figure 8Battery Discharging Curve
Figure 8Battery Discharging Curve
Figure 8Battery Discharging Curve
Figure 8Battery Discharging Curve
Figure 8Battery Discharging Curve
Figure 8Battery Discharging Curve
Figure 8Battery Discharging Curve
Figure 8Battery Discharging Curve
Figure 8Battery Discharging Curve
Figure 8Battery Discharging Curve
Figure 8Battery Discharging Curve
Figure 8Battery Discharging Curve
Figure 8Battery Discharging Curve
Figure 8Battery Discharging Curve
Figure 8Battery Discharging Curve
Figure 8Battery Discharging Curve
Figure 8Battery Discharging Curve
Figure 8Battery Discharging Curve
Figure 8Battery Discharging Curve
Figure 8Battery Discharging Curve
Table 2 Brief Description of Electrical Test ProceduresTest Title Description
MPPT Converter Voltages between 0 V and 4 V are input while an output of 6.5 V ±5% is expected.
MPPT Tracking Various temperature differences are applied to the TEG. The MPPT outputs half of the input voltage.
Fan Converter
Given an input voltage range equivalent to the battery terminal voltage range, the Fan converter must convert the input to 12V with current output of 100mA.
HVLV (High Voltage Low Voltage) Disconnect
Given input of 6.2V which is slowly increased to determine if system disconnects. Given input of 5.8V which is slowly decreased to determine if system disconnects.
Battery Charging MPPT is used to charge battery while voltage across terminals of battery is regularly measured.
Battery Discharging
The battery is connected to the system and the battery terminal voltage is measured as it runs the system without the stove to assist.
USB Converter
Given an input voltage range equivalent to the battery terminal voltage range, the USB converter must convert the input voltage to 5V with current output of 500mA.
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System Current
-1.000
-0.500
0.000
0.500
1.000
1.500
2.000
0.00 50.00 100.00 150.00 200.00 250.00
Temperature difference [C]
Curr
ent [
A]
TEG
Fan
USB
Battery
Figure 9Current measured at various points in circuit during full
system test
Figure 9Current measured at various points in circuit during full
system test
Figure 9Current measured at various points in circuit during full
system test
Figure 9Current measured at various points in circuit during full
system test
Figure 9Current measured at various points in circuit during full
system test
Figure 9Current measured at various points in circuit during full
system test
Figure 9Current measured at various points in circuit during full
system test
Figure 9Current measured at various points in circuit during full
system test
Figure 9Current measured at various points in circuit during full
system test
Figure 9Current measured at various points in circuit during full
system test
Figure 9Current measured at various points in circuit during full
system test
Figure 9Current measured at various points in circuit during full
system test
Figure 9Current measured at various points in circuit during full
system test
Figure 9Current measured at various points in circuit during full
system test
Figure 9Current measured at various points in circuit during full
system test
Figure 9Current measured at various points in circuit during full
system test
Figure 9Current measured at various points in circuit during full
system test
Figure 9Current measured at various points in circuit during full
system test
Figure 9Current measured at various points in circuit during full
system test
Figure 9Current measured at various points in circuit during full
system test
Figure 9Current measured at various points in circuit during full
system test
Figure 9Current measured at various points in circuit during full
system test
Figure 9Current measured at various points in circuit during full
system test
Figure 9Current measured at various points in circuit during full
system test
Figure 9Current measured at various points in circuit during full
system test
Figure 9Current measured at various points in circuit during full
system test
Figure 9Current measured at various points in circuit during full
system test
Figure 9Current measured at various points in circuit during full
system test
Figure 9Current measured at various points in circuit during full
system test
Figure 9Current measured at various points in circuit during full
system test
9
System Voltage
0.000
2.000
4.000
6.000
8.000
10.000
12.000
14.000
0.00 50.00 100.00 150.00 200.00 250.00
Temperature difference [C]
Volta
ge [V
]
Fan
USB
TEG
Figure 10Voltage measured at various points in circuit during full
system test
System Power
0.000
0.500
1.000
1.500
2.000
2.500
3.000
3.500
4.000
4.500
5.000
100.00 150.00 200.00
Temperature difference [C]
Pow
er [W
]
TEG
Fan
USB
Figure 11Power calculated at various points in circuit for full
system test
Figure 10Voltage measured at various points in circuit during full
system test
Figure 10Voltage measured at various points in circuit during full
system test
Figure 10Voltage measured at various points in circuit during full
system test
Figure 10Voltage measured at various points in circuit during full
system test
Figure 10Voltage measured at various points in circuit during full
system test
Figure 10Voltage measured at various points in circuit during full
system test
Figure 10Voltage measured at various points in circuit during full
system test
Figure 10Voltage measured at various points in circuit during full
system test
Figure 10Voltage measured at various points in circuit during full
system test
Figure 10Voltage measured at various points in circuit during full
system test
Figure 10Voltage measured at various points in circuit during full
system test
Figure 10Voltage measured at various points in circuit during full
system test
Figure 10Voltage measured at various points in circuit during full
system test
Figure 10Voltage measured at various points in circuit during full
system test
Figure 10Voltage measured at various points in circuit during full
system test
Figure 10Voltage measured at various points in circuit during full
system test
Figure 10Voltage measured at various points in circuit during full
system test
Figure 10Voltage measured at various points in circuit during full
system test
Figure 10Voltage measured at various points in circuit during full
system test
Figure 10Voltage measured at various points in circuit during full
system test
Figure 10Voltage measured at various points in circuit during full
system test
Figure 10Voltage measured at various points in circuit during full
system test
Figure 10Voltage measured at various points in circuit during full
system test
Figure 10Voltage measured at various points in circuit during full
system test
Figure 10Voltage measured at various points in circuit during full
system test
Figure 10Voltage measured at various points in circuit during full
system test
Figure 10Voltage measured at various points in circuit during full
system test
Figure 10Voltage measured at various points in circuit during full
system test
Figure 10Voltage measured at various points in circuit during full
system test
Figure 11Power calculated at various points in circuit for full
system test
Figure 11Power calculated at various points in circuit for full
system test
Figure 11Power calculated at various points in circuit for full
system test
Figure 11Power calculated at various points in circuit for full
system test
Figure 11Power calculated at various points in circuit for full
system test
Figure 11Power calculated at various points in circuit for full
system test
Figure 11Power calculated at various points in circuit for full
system test
Figure 11Power calculated at various points in circuit for full
system test
Figure 11Power calculated at various points in circuit for full
system test
Figure 11Power calculated at various points in circuit for full
system test
Figure 11Power calculated at various points in circuit for full
system test
Figure 11Power calculated at various points in circuit for full
system test
Figure 11Power calculated at various points in circuit for full
system test
Figure 11Power calculated at various points in circuit for full
system test
Figure 11Power calculated at various points in circuit for full
system test
Figure 11Power calculated at various points in circuit for full
system test
Figure 11Power calculated at various points in circuit for full
system test
Figure 11Power calculated at various points in circuit for full
system test
Figure 11Power calculated at various points in circuit for full
system test
Figure 11Power calculated at various points in circuit for full
system test
Figure 11Power calculated at various points in circuit for full
system test
Figure 11Power calculated at various points in circuit for full
system test
Figure 11Power calculated at various points in circuit for full
system test
Figure 11Power calculated at various points in circuit for full
system test
Figure 11Power calculated at various points in circuit for full
system test
Figure 11Power calculated at various points in circuit for full
system test
Figure 11Power calculated at various points in circuit for full
system test
Figure 11Power calculated at various points in circuit for full
system test
Figure 11Power calculated at various points in circuit for full
system test
Conclusions/Recommendations
Currently the MPPT circuitry in the system is not outputting the maximum power possible. Although several designs were able to function as individual subsystems, functionality was lost when the system was connected to the rest of the power pack circuitry. Future work should focus on designing and building this subsystem to integrate with the back end of the circuitry.
Future should also focus on designing the system use power as efficiently as possible. It is important that the maximum power possible is harvested from the TEG to power the fan and USB. Therefore, some components of the system, such as the DC-DC converters, should be redesigned to be as power-efficient as possible.
The cost of the system should be lowered as much as possible. Currently the system costs roughly $12 a piece for a quantity of 10,000. The specification given for this project was $10-$15, but when combined with the price of the stove unit, this is most likely higher than a typical customer can afford.
The goal for the finished product was to have the circuit on a PCB and placed in an enclosure with the battery. Currently the circuit is on a breadboard. When the future system is placed in an enclosure it will then have to undergo testing to determine its durability according to the customer specifications.
When the entire stove system is completed, it will be sent to Haiti for field testing with potential customers.
Acknowledgements
We would like to thank Professor Edward Hanzlik, Dr. Robert Stevens, Jagdish Tandon, Neal Eckhaus, Dr. Lynn Fuller, James DeJager, and Satchit Mahajan for their support and involvement in this project. We would also like to thank RIT and H.O.P.E for making this project possible.
References
[1] United Nations. World Health Organization. Indoor Air Pollution and Health. Sept. 2011. Web. 26 Apr. 2012. <http://www.who.int/mediacentre/factsheets/fs292/en/>.
[2] United States. Federal Research Division. Country Profile: Haiti. Library of Congress, May 2006. Web. 26 Apr. 2012.<http://lcweb2.loc.gov/frd/cs/profiles/Haiti.pdf>.
[3] S. Kim, S. Cho, N. Kim, and J. Park. “A maximum power point tracking circuit of thermoelectric generators without digital controllers,” IEICE Electronics Express., vol. 7, no. 20, pp. 1539-1545, Oct. 2010.
[4] J. Rugg, B. Sawyer, J. Bird, T. Gorevski, F. Masood. “Thermoelectric and Fan System for Cook Stove,” Multi-Disciplinary Senior Design Conference, 2008.
[5] H. Nagayoshi, T. Nakabayashi, H. Maiwa, T. Kajikawa. “Development of 100-W High-Efficiency MPPT Power Conditioner and
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Evaluation of TEG System with Battery Load,” Journal of Electronic Materials,
[6] Ministère des Travaux Publics, Transports et Communications. Haiti: Plan de Développement du Secteur de l’Energie. November 2006. Web. 8 May 2012. http://www.mtptc.gouv.ht/pdf/energie/plan%20national%20developpement%20energie-%20francais.pdf
[7] Johnston, Hamish. “Multiple valleys boost thermoelectric performance.” PhysicsWorld.com. 5 May 2011. Institute of Physics. 12 May 2011 http://physicsworld.com/cws/article/news/2011/may/05/multiple-valleys-boost-thermoelectric-performance
1. Test Name: Battery Charging using MPPTTest Author: Xiaolong ZhangDescription: MPPT is connected to the battery through a Boost converter which provides 6.5V output at maximum current of 600 mA. Voltage across the terminal of the battery is measured every 15 minutes with system connected. The results are collected and a scatter graph can be created to show the relationship of battery charging.
1 Multimeter 1 Measure voltage across the terminals of the battery every 15 minutes
2 Power supply 1 Provide steady voltages3 MPPT with boost converter 1 6.5V @600mA
Table 1: Required equipment and its settings.
3. Test ProcedureStep 1: Connect power supply to the input of the MPPT and connect battery to the output pins of the MPPTStep 2: Verify MPPT output 6.5V at 600mA with battery connectedStep 3: Measure the voltages across terminals of the battery every 15 minutes and record data in MS ExcelStep 4: When the battery terminal voltage reaches 6.4V disconnect the MPPT and battery
4. Test ResultsStep
# Description Spec Measurement
1Length of time for the
battery terminal voltage to reach 6.4V
time period Time (Minutes): ? Minutes
Table 2: The results of the test procedure.
Excel TableExcel scatter plot
5. Pass/FailDid the unit pass or fail the test? Defend your decision.
PASS
FAIL
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Table 3: PASS/FAIL
1. Test Name: Battery DischargingTest Author: Xiaolong ZhangDescription: Battery is connected to a decade resistor box, the resistance is set to 8 ohms (6.5V and 750mA) to simulate the current draw, voltage across the terminal of the battery is measured every 15 minutes with the resistor box is connected. The results are collected and a scatter graph can be created to show the relationship of battery discharging. Then high voltage and low voltage disconnected voltages can be determined based on the resulting curve.
1. Test Name: Fan ConverterTest Author: Xiaolong ZhangDescription: Battery provides different level of voltages when it’s at different battery level. A fan converter is used to convert various input voltages to 12V with current output of 100mA to run the fan correctly.
1 Power supply 1 5V – 7V varied input voltages2 Multimeter 2 Current (A) and Voltage (V)3 Fan (KD1204PFB2) 14 Fan Converter 1
Table 8: Required equipment and its settings.
3. Test ProcedureStep 1: Connect the power supply to the input pins of the Fan converter, and the mulitmeter in series with the output pins of the Fan converter
Step 2: Slowly increase the power supply voltage from 5V to 7V
Step 3: Measure the output voltage and current of the Fan converter
4. Test ResultsStep # Description Spec Measurement
2Measure the output voltage
and current of the fan converter with an input of 5V.
Vout: 12V +/- 10%Iout:.075A +/- 10%
Vout:12.5VIout:.082A
4Measure the output voltage
and current of the fan converter with an input of 6V.
Vout: 12V +/- 10%Iout:.075A +/- 10%
Vout:11.75VIout:.074A
6Measure the output voltage
and current of the fan converter with an input of 7V.
Vout: 12V +/- 10%Iout:.075A +/- 10%
Vout:11.76VIout:.074A
Table 9: The results of the test procedure.
5. Pass/FailDid the unit pass or fail the test? Defend your decision.
15
Table 10: PASS/FAIL
1. Test Name: High/Low Voltage DisconnectTest Author: Xiaolong ZhangDescription: The high voltage disconnect is integrated to protect the battery from overcharging and low voltage disconnect is integrated to disconnect the USB and fan so the battery will have enough power to restart the system for one hour.
2 Oscilloscope 1 Trigger on the rising/falling edge3 HV/LV disconnect system 1
Table 11: Required equipment and its settings.
3. Test ProcedureStep 1: Build the HV/LV disconnects system as seen in the system schematic.
Step 2: Connect the power supply to the +12V rails of the circuit.
Step 3: Connect the output of power supply two to the battery terminal pins of the circuit.
Step 4: Adjust the output of power supply two to 6.2V, slowly increase it by hundredths of a volt until the battery is disconnected from the circuit. Record the voltage.
Step 5: Adjust the output of power supply two to 5.8V, slowly decrease it by hundredths of a volt until the USB output and fan output are disconnected. Record the voltage.
4. Test ResultsStep # Description Spec Measurement
1 High Voltage Disconnect Voltage Voltage: 6.2V +/- 5% 6.24V
2 Low Voltage Disconnect Voltage Voltage: 5.8V +/- 5% 5.8V
Table 12: The results of the test procedure.
16
PASS
FAIL
Pass
Figure 2: Output voltage drops when the battery terminal voltage reaches 6.24V
Figure 3: Output Voltage drops when the battery terminal voltage goes below 5.8V
5. Pass/FailDid the unit pass or fail the test? Defend your decision.
PASS
FAIL
PassTable 13: PASS/FAIL
17
1. Test Name: MPPT ConverterTest Author: Xiaolong ZhangDescription: MPPT provides different level of voltages when it’s at different battery level, a MPPT converter is used to convert various input voltages to 6.5V with current output of 750mA.
2 Multimeter 2 Measure voltage and current at the output pin of the MPPT converter
3 MPPT Converter 1
Table 14: Required equipment and its settings.
3. Test ProcedureStep 1: Connect the power supply to the input pins of the MPPT converter, and the mulitmeter in series with the output pins of the MPPT converter
Step 2: Slowly increase the power supply voltage from 0V to 4V
Step 3: Measure the output voltage and current of the Fan converter
4. Test ResultsStep # Description Spec Measurement
1
Measure the output voltage and current of the MPPT
converter with an input of 2V.
Vout: 6.5V +/- 10%Iout:.750mA +/- 10% ?
2 Measure the output voltage and current of the MPPT
converter with an input of 3V.
Vout: 6.5V +/- 10%Iout:.750mA +/- 10% ?
3 Measure the output voltage and current of the MPPT
converter with an input of 4V.
Vout: 6.5V +/- 10%Iout:.750mA +/- 10% ?
Table 15: The results of the test procedure.
5. Pass/FailDid the unit pass or fail the test? Defend your decision.
PASS
FAIL
18
Table 16: PASS/FAIL
1. Test Name: MPPT TrackingTest Author: Xiaolong ZhangDescription: MPPT (Maximum power point tracking) is used to track and keep the system to provide the maximum output power at different temperature difference between the cold side and hot side of the TEG (Thermoelectric generator). MPPT should track half of the input voltage.
Oscilloscope capture when the input voltage is 2V, 4V, 6V and 8
5. Pass/FailDid the unit pass or fail the test? Defend your decision.
PASS
FAIL
19
Table 19: PASS/FAIL
1. Test Name: Customer Acceptance TestTest Author: Lauren Cummings, Andrew PhillipsPurpose: To determine if the full system meets the customer requirements.Description: The disconnect voltages of the USB and fan are tested.
1 Battery 1 Just above 5.9 V2 Power Pack 13 TEG testing equipment 1 Temperature difference of 200⁰C4 Cell phone 2 Fully discharged5 Multimeter 56 Computer 1 Must have spreadsheet software
Table 20: Required equipment and its settings.
Figure 4: The system setup.
3. Test ProcedureStep 1: Record starting voltage of battery; connect battery to the system and power on the circuit.
20
Fan
USB Connector
Multimeter (A)
Multimeter (A)
Battery
Thermoelectric Power PackTEG
TEG Test Fixture
Multimeter (A)
Multimeter (A)
Step 2: Run the system until USB disconnects. Record the battery, fan and USB voltage every 15 minutes in a spreadsheet.
Step 3: Run the system until the fan disconnects. Continue to record the battery, fan and USB voltage every 15 minutes in a spreadsheet.
Step 4: Attach the power pack to TEG testing equipment. Set the temperature difference to 200⁰C and start the test equipment. Record voltage input and output of MPPT every 15 minutes. Continue to record the battery, fan and USB voltage every 15 minutes in a spreadsheet.
Step 5: Continue to run the system. When the TEG starts powering the system record the time elapsed. Continue to record the battery, fan, MPPT and USB voltage every 15 minutes in a spreadsheet.
Step 6: Continue running system. When the fan starts receiving power, record time elapsed. Continue to record the battery, fan, MPPT and USB voltage every 15 minutes in a spreadsheet.
Step 7: Continue running system. When the USB starts receiving power, record time elapsed. Continue to record the battery, fan, MPPT and USB voltage every 15 minutes in a spreadsheet.
Step 8: Continue running system. When the battery disconnects, record time elapsed. Continue to record the battery, fan, MPPT and USB voltage every 15 minutes in a spreadsheet.
Step 9: Disconnect the TEG from the system.
Step 10: Connect a cell phone to the USB output. Continue to run the system until the phone is fully charged or until the USB disconnects. Continue to record the battery, fan, and USB voltage every 15 minutes in a spreadsheet. Record the battery terminal voltage when the battery is reconnected to the system.
Step 11: If the cell phone becomes fully charged attach a second cell phone and continue to run the system, recording the battery, fan, and USB voltage every 15 minutes in a spreadsheet. Repeat this until the USB is disconnected.
Step 12: Power off the power pack and disconnect the system.
4. Test Results
Step # Description Time ElapsedMPPT
Voltage Input/Output
Battery Voltage
USB Voltage Fan Voltage
1Initial Battery
Terminal Voltage
2 USB disconnect
21
3 Fan disconnect
5System begins
receiving power from TEG
6 Fan reconnects
7 USB reconnects
8Battery
Disconnects
9Battery
Reconnects
10 USB disconnect
11First Cell Phone
is Charged
11Second Cell
Phone is Charged
Full running time
Table 21: The results of the test procedure.
Comment on the number of cell phones charged/time spent charging:
5. Pass/FailDescription Pass/Fail
System can be powered on at will
System can provided needed power to the fan
USB disconnects at 5.9 V
USB reconnects at 5.9 V
Fan disconnects at 5.7 V
Fan reconnects at 5.7 V
22
Battery disconnects at 6.4 V
Battery reconnects at 6.4 V
MPPT provides maximum power to the system
2 Cell Phones are charged
System can be powered off at will
Table 3: Pass/Fail
6. AppendixUSB, fan, MPPT, and battery terminal voltage data here.
