Final Report - Harding University
Contents
1. Battery The battery was charged by excess DC voltage produced by the thermoelectric generator It served as a regulator as the output of the thermoelectric generator fluctuated Input 14 V and 23 A DC 322 W Output 12 7 V and 18 A DC 228 6 W Inverter The inverter converted the DC power from the thermoelectric generator or battery into AC power and stepped up the voltage Input 12 V and 18 A DC 216 W Output 120 10 VAC greater than 1 5 Amps 60 0 05 Hz User Interface This circuitry controlled the flow of power to the outlet as well as indicated to the user when sufficient power was being supplied to the outlet When the user switch was in the on position power was available and the user could plug in a device using 200 watts or less When it was in the off position no power was supplied to the outlet Additionally a single indicator LED would light up when at least 12 volts was being supplied by the battery The user interface worked as expected except for the low power output of the thermoelectric generators If the power output from the thermoelectric generators could be increased then the battery could be charged while operating the fans The inverter needed to be run from the battery alone However the thermoelectric generators simultaneously charged the battery Input 12 7 V DC and 1 5 A 60 0 05 Hz User controlled switch Output LED indicator Unit Outlet The unit outlet was a standard household outl2. Capacity 18 000 mAh 18 Ah Rating 216 Whr Connector R Terminal Length 7 13 inch 18 11 cm Width 3 03 inch 7 70 cm Height 6 57 inch 16 69 cm Color Gray Weight 11 02 lb 4 998 56 g Warranty 1 Year UPC Code 880487220647 28 Part Name Inverter PowerVer ter Supplier Buy com Manufacturer Tripp Lite Model Number PV375 375 Watts Datasheet Unavailable Specifications See Below General Specifications Weight Device Type Miscellaneous Cables Included Manufacturer Warranty Service amp Support Service amp Support Details Power Device Input Connector s Output connector s More Information Shipping Weight in pounds Product in Inches Lx W x H Assembled in Country of Origin Origin of Components 2 2 Ibs DC to AC power inverter external 1 x power cable 1 year warranty Limited warranty 1 year 1 x automobile cigarette lighter 2 x power NEMA 5 15 2 25 6 0 x 3 0x 4 0 Imported Imported 29 Appendix E Encasement Parts Reduced energy loss lower heating amp cooling bills High R value Unsurpassed durability Moisture resistant facers Lightweight easy to install Part Name Encasement Exterior Utility Plywood Supplier Lowe s Datasheet Unavailable Specifications Thickness 5 2mm Area 4x 8 Feet Name Insulation Supplier Lowe s Manufacturer Dow Model Number 263063 Datasheet Unavailable Specifications See Below Insulation Type Poly
3. TEG voltage Battery Voltage Current Out of Battery 13 3 V 12 6 V 200 mA Table 5 Results of system testing without extra power source TEG Voltage Battery Voltage Current Into Battery 13 5 V 12 63 V 85 mA These results Tables 4 and 5 show that the battery can be charged but with our current configuration all TEGs in series we are not able to power the fans as well We connected two TEGs in parallel and connected those in series with the remaining eight and the results of that test were less than from Table 5 The current into the battery was approximately 30 mA and 13 1 volts These results were taken with the extra power supply working in tandem with the circuitry We believe that the reason behind this is because the voltage of the two TEGs is not equal to the voltage of the other eight Most of the time you would connect two sources of equal voltage potential to double the current output However with this configuration the output voltage from the two TEGs and the other eight would be approximately 2 8 V at 0 6 A and 11 8 V at 0 6 A 19 Encasement By size alone the encasement is the largest section of the Wood Burning Generator Because the generator is required to be easily moved and stored 5 0mm utility plywood was chosen to be the encasement material to keep the generator light yet sturdy The encasement is pictured in the figure below Figure 11 Encasement The encasement holds all of the other subsystems of the gener
4. route harmful gases carbon dioxide carbon monoxide nitrogen oxides and aldehydes out from the house Due to the large variety of sensors needed along with the associated costs this will be judged by visually observing if there is a change to the amount of smoke in the room when the device is in use compared to when it is not in use Nature of Fuel The device will work with a fire built with wood logs not wood chippings or sawdust The user will not be required to cut the logs to certain dimensions provided the logs will fit in the fireplace User Intervention The user will be responsible for maintaining the fire An indicator on the device will notify the user if the fire is not hot enough sufficient power is not being produced see Indicators and Controls The device should not require the user to burn more than 25 pounds of wood per hour Indicators and Controls The device will indicate visually e g LED to the user when enough electricity is being generated to run a device Additionally the user will be able to cut off power to the outlet by shutting off the device with a switch Electrical Safety The electrical system must be grounded by a connection to an existing wall outlet s ground All internal wires should be able to handle the maximum amount of current in order to prevent electrical fires Wire that is at least an AWG gage 10 nonmetallic insulated wire will provide this safety General Safety Any exposed o
5. 12 VDC 20 mA Heat Sink 14 6 VDC 0 6 Amps 95 C lt T lt 100 C Battery Thermoelectric 12 VDC 18 A Generator Excess heat Inverter 100 C without cooling 120 10 VAC A gt 1 5 Amps 60 05 Hz Cooling Device Unit Outlet Functional Description of Blocks Fireplace The user s fireplace acted as the combustion chamber and contained the wood burning fire The fire provided temperatures between 100 C and 500 C The fireplace performed as expected and successfully supplied heat to the thermosyphon Input Wood Output Temperatures between 100 C and 500 C Thermosyphon The thermosyphon collected heat from the fire in a boiler changing liquid water to water vapor which then exited the fireplace and delivered temperatures ranging from 95 C to 100 C The vapor condensed in copper coils was stored in the holding tank and then returned to the boiler The thermosyphon went through many changes throughout construction see Thermosyphon section for more information but performed as anticipated Improvements could be made by increasing the pressure of the boiler and therefore the temperature of the steam which would increase the energy production of the thermal electric generators Input Temperatures between 100 C and 500 C Output Temperatures between 95 C and 100 C Hot Side Heat Sink The hot side heat sink transferred the heat from the thermosyphon to the hot side of 10 thermoelectric gener
6. Thermoelectric Generator Final Report April 28 2010 Kevin Jensen Drew Messick Jeremy Verzosa Table of Contents Requirements Specific rana odia AL AG LALA IL 3 Project Overview RO ARA AA Dia LR eni iii 5 Introduction ae Be se A AAA AAA 6 Budget aT I A E EE EA EE EEEE cada e 7 BIOCK Diagram 2 EEEE A E E E nn 8 Functional Description Of Blocks sise 9 Sub System Details gt Anr ireland 11 Thermosyphori as nare alal RI 12 Thermoelectric Generator 24er Hier Dl 13 Cooling syste ernannte A das 14 User Interface and Inverter sii iaia aaa nola isla is nn nn Isis hans 15 Encasementisi A 2 lla arri nia aiar i 20 Testing Results Ananas latenza la ai 2 rare te dt eee dl dre ds 21 Recommendations ee aa a iata stu p adi da taia data Da a e aaa 03 22 Appendices a 2 cicala 23 Appendix A Thermosyphon Parts i 24 Appendix B Thermoelectric Generator Parts ss 25 Appendix C Cooling System Parts idees 26 Appendix D User Interface and Inverter PartS ss 28 Appendix E Encasement Parts siae a a RA nani 30 Requirements Specification Background There is a large interest in today s market for sustainable energy Consumers are looking for devices that can provide electricity to their home not only when power is unavailable but also in addition to their normal usage The trouble with most products is that they are complex bulky and expensive Additionally ene
7. ally desired by the team but the voltage needed was achieved Additionally the output of 14 6 V was very steady and only fluctuated within 0 05 V during steady operating conditions The thermal electric generators were successfully used to power the circuit and charge the battery Unfortunately this was only possible when the fans were being powered by an external power source and the inverter was turned off 13 Cooling System The cooling system removes heat from the top of the thermoelectric generator It consists of 10 finned heat sinks and two fans One 0 60 C W thermal resistance heat is attached to the top of each TEG and secured by a worm clamp system and thermal paste Above the heat sinks are two 80mm diameter fans mounted to the bottom side of the top panel of the encasement The fans provide an essential temperature difference to the TEGs During testing the average output of the TEGs was 11 6 V higher after the fans were turned on miT T A I Un ii 111 A Tia ULE LO LEELA SINO LULL LIS Figure 6 Cooling System Using an equation determined during the design process the expected resultant thermoelectric generator output for the final design was 25 7 W This is 14 1 V higher than the actual results The equation s main purpose was to determine the number of fans It served that purpose well Nevertheless this equation was not good for estimating the actual output of the thermoelectric generators This is due t
8. as measured and found to be 1 92 x 2 08 x 1 08 feet 0 59 x 0 63 x 0 33 which is only approximately 1 inch over the size limit of 2 x 2 x 1 5 feet 0 61 x 0 61 x 0 46 m in the middle dimension height The weight was measured at 55 Ibs 24 9 kg which was slightly over the weight limit of 50 Ibs 22 7 kg The generator was taken to a home with a fireplace and tested Nothing was permanently installed satisfying that specification Whether the usage of the generator increased the dangerous gases in the room was judged visually and the amount of smoke in the room did not change significantly The fire built to test the device was built with wood and therefore passes that specification Once power generation began an LED light indicated to the user when something could be plugged in The user could also shut the power off by the use of a switch The external temperature of the device was measured using an infrared thermometer All of the readings were below 43 C and therefore this specification was satisfied The wood burning generator went through many tests before it could be considered finished and operational Ultimately the device fulfilled seven out of nine specified technical requirements while coming very close to satisfying the remaining two size and weight 21 Recommendations During the construction of the first prototype the team came up with design variations of the wood burning generator that could not be implemented due to either co
9. ator with the exception of the boiler section of the thermosyphon that is placed inside the fireplace itself The dimensions of the encasement are as follows 31 1cm wide 29 2cm long and 61 9cm high Two sections of the encasement have doors held shut by magnets The first section is for the user to interact with the system and add water to the holding tank The second section is for easy access to the electrical components and would be left out of a production model of this generator The encasement was spray painted black for aesthetics 20 Testing Results To ensure that the subsystem integration went smoothly and then to ultimately test the device given the requirements specification the wood burning generator went through three levels of testing sub component testing integration testing and finally requirements specification testing Each sub component had its own tests to pass before it was considered complete The thermosyphon had to transport heat from the fireplace to the thermal electric condensing chamber This test was passed when the temperature of the thermal electric generator pad reached a temperature above 95 C The thermosyphon was also checked to make sure the boiler could be successfully refilled The cooling system fans were connected to a 12 volt power supply and tested to ensure that they worked The electrical systems were tested by modeling the thermal electric generators as a power supply and the output was verified to me
10. ators 40mm x 40mm each It was maintained at temperatures between 95 Cto 100 C Input Temperatures between 95 C and 100 C Output Temperatures between 95 C and 100 C Thermoelectric Generator The thermoelectric generator used the temperature differential that existed between the hot side heat sink and the cold side heat sink to produce approximately 14 6 volts and 0 6 Amps DC or 8 76 Watts ten individual thermoelectric generators providing approximately 1 5 Volts and 0 60 Amps each assuming a temperature differential of 50 C all ten placed in series The thermal electric generators did not produce the amount of power initially expected of them However this was due to changes in the thermosyphon Additional thermoelectric generators or an increase in thermosyphon temperature could potentially increase power output Input Temperature between 95 C and 100 C Output 14 6 Volts and 0 60 Amps DC 8 76 watts Excess heat 100 C without cooling Cooling Device The cooling device removed approximately 2149 W or more of heat from the thermoelectric generators This was achieved through forced convection by two fans over ten finned heat sinks The cooling device successfully cooled one side of the thermoelectric generators The system might be improved with larger heat sinks or heat sinks made of material with great heat conductance e g copper Input Excess heat 100 C without cooling Output gt 2149W heat removed
11. e project while allowing the theory to still be tested Construction began during the spring semester Unfortunately some design changes were made during this time resulting in increases to Figure 1 Stage 2 and 3 Design research and development costs Many of these changes simplified the final result and brought down the actual manufacturing cost as well as making a better product Construction was completed with some time to spare Initial testing of the system yielded electrical problems which were fixed before the prototype was ready for unveiling The system as a whole worked as designed The thermosyphon successfully transported heat from the fireplace to the thermoelectric generators and the cooling system effectively cooled the other side of the thermoelectric generators Unfortunately the thermoelectric generators were not able to produce enough power to charge the battery and power the fans due to the steam temperature of the thermosyphon being lowered By using an external power source for the fans the circuit was successfully used to charge the battery with the thermoelectric generators The wood burning generator project was an excellent test for the mechanical and electrical engineering skills of the team members Despite challenges and setbacks encountered during both design and construction the team delivered a prototype which satisfied seven out of nine technical requirements and came very close to satisfying the other two s
12. et NEMA type B that the user plugged their device into Originally the neutral pin was to be connected to the metal frame of the device However during construction the encasement material was changed to wood and it was determined that the outlet was safe without this extra precaution Input 110 VAC 125 VAC greater than 1 5 Amps 60 0 05 Hz Output 110 VAC 125 VAC greater than 1 5 Amps 60 0 05 Hz 10 Sub System Details Thermosyphon The purpose of the thermosyphon is to transfer heat from the fireplace to the thermal electric generators This is done by boiling water in a boiler located inside of the fireplace The steam produced then travels to a heat exchanger where the energy is transferred to the thermal electric generators Any remaining steam is then condensed in copper tubes and eventually recycled back into the boiler The design of the thermosyphon consists of three main parts The boiler is located in the fireplace and facilitates liquid water being turned in to water vapor The thermal electric condensing chamber and the condensing tubes extract energy from the steam and return it to the liquid phase The holding tank stores this water and allows the user to refill the boiler starting the process over again A boiler gage allows the user to know the temperature and pressure of the boiler Many of the design changes throughout the spring semester were driven by safety concerns There are many standards that affect boi
13. et requirements The encasement was tested to ensure that it was sturdy enough to support the weight of the other components Initially the encasement failed this test but by replacing the brackets the encasement passed the test Further tests were performed while integrating the sub components with one another The thermosyphon was tested with the encasement to ensure that the pipes had holes to go through as well as the tanks having enough space inside the generator The thermal electric generator pad was tested to make sure there was enough space between it and the top of the encasement for the thermoelectric generators the heat sinks and the fans to fit Initially this test failed but by changing the length of one pipe on the thermosyphon the test was passed The cooling system thermal electric generators and the thermosyphon were integrated and tested for electrical output Initially one of the cooling system fans failed and the output was much less but in a second test both fans worked and the output was found to be 14 6 V and 0 6 A The last major integration test involved connecting the circuit to the thermal electric generators This test was initially failed but modifications were made and the circuit performed as expected However the thermal electric generators could not produce enough current to both power the fans and charge the battery The last set of tests involves satisfying the requirements specification The size of the device w
14. isocyanurate Thickness Inches 0 5 Length Feet 8 0 Width Feet 4 0 R Value 3 0 Installation Instructions included Yes Weather Resistant Barrier Yes 30
15. istance lt 0 007 C in2 Watt 0 001 inch layer Average Particle Size lt 0 38 microns lt 0 000015 inch 67 particles lined up in a row equal 1 1000th of an inch Temperature Limits Peak 150 C to gt 180 C Long Term 150 C to 125 C Coverage Area At a layer 0 003 thick one tube will cover approximately 20 square inches 2 5 gram 0 8 cc tube 25 Appendix C Cooling System Parts Part Name Fan Supplier Newegg com Manufacturer Link Depot Model Number 8025 B Datasheet Unavailable Specifications Size 80x80x25mm Current 0 16A Air Flow 38 2CFM Speed 3000RPM Power 1 92W Bearing One ball bearing Voltage 12VDC Noise 32 1dBA Name Heat Sink Supplier Cool Innovations Model Number 3 151511U Datasheet Attached Name Aluminum Scrap Metal Supplier Harding University Physical Resources Manufacturer Unknown Model Number Unknown Datasheet Unavailable 26 Part Name Worm Clamp Supplier Lowe s Home Improvement Manufacturer King Seal Fastener Technology Model Number BCMMA4SS09P10 Datasheet Unavailable Part Name Picture Wire Supplier Unknown Manufacturer Unknown Model Number Unknown Datasheet Unavailable 27 Appendix D User Interface and Inverter Parts Part Name Battery Supplier atbatt com Manufacturer Amstron Model Number AP 12180NB Datasheet Unavailable Specifications See Below Specifications Chemistry Lead Acid Voltage 12
16. ith no parts exposed that could cut or burn the user Additionally the electrical aspects should present no risk of fire or shock The NEMA Type B outlet should be properly grounded Input The input of the device is a wood burning fire in an open hearth fireplace The heat from the fire will serve as the energy source for the electric generator Closed stoves and gas burning fireplaces will not be supported Output The generator s output connector will consist of a NEMA Type B electrical outlet The outlet will provide 125 VAC 15 and at least 1 5 A 10 at 60 Hz 0 5 For comparison most normal household electrical outlets in the United States provide approximately 125 volts and 15 amps at 60 Hz when connected to the power grid Technical Requirements The following requirements must be met 1 Size The device should be small and light enough to be carried by a single person The generator should be no greater than 0 6 x 0 6 x 0 46 meters 2 x 2 x 1 5 feet This does not include the device for collecting and transporting heat from the fire to the generator Weight The device should not weigh more than 22 7 kg 50 Ibs Installation The generator will sit on the hearth and a device will be extended into the fire for heat collection There will be no permanent attachments such as bolts or screws to be affixed prior to use Harmful Gases The device should not compromise the existing effectiveness of the fireplace to
17. ize and weight Budget Analysis The team s total budget for producing a working prototype of the wood burning generator was set at 850 The team ended the year having spent a total of 841 01 leaving 8 99 left over in the contingency fund The actual cost for producing the device was found to be 695 16 Mass producing the device could bring this cost even lower The research and development cost of the wood burning generator is broken down by subcomponent in Table 1 The actual production cost is shown in Table 2 Table 1 Research and Development Cost by Sub Function Sub Function Original Current Thermosyphon 55 00 324 35 Thermoelectric Generator 215 00 205 36 User Interface 65 00 113 65 Inverter 60 00 47 22 Cooling System 70 00 113 20 Encasement 35 00 37 23 Contingency 350 00 8 99 Total 850 00 850 00 Table 2 Production Cost by Sub Function Sub Function Original Current Thermosyphon 55 00 194 85 Thermoelectric Generator 215 00 205 36 User Interface 65 00 104 61 Inverter 60 00 47 22 Cooling System 70 00 113 20 Encasement 35 00 29 92 Contingency 350 00 154 84 Total 850 00 850 00 The team came close to going over budget but through judicious spending and careful choice of parts and vendors the total cost was 841 01 with 8 99 left over Block Diagram Encasement Boundary 100 C lt T lt 500 C 95 C lt T lt 100 C Fireplace User Interface Hot Side
18. learned a lot from the first prototype both in design and in construction An even better product could be made by building a second prototype including some innovative upgrades that would make the device more efficient and easier to use 22 Appendices Appendix A Thermosyphon Parts Part Name Brass Piston Check Valve Spring Loaded 1 NPT Female Supplier McMaster Carr Catalog Number 7746K83 Datasheet Unavailable Specifications Maximum Pressure is 200 psi 225 F Cracking Pressure 1 psi Temperature Range 33 to 225 F Connections are 1 NPT Female Part Name Brass Ball Valve Supplier Lowe s Home Improvement Manufacturer American Valve Catalog Number M100 Datasheet Attached 24 Appendix B Thermoelectric Generator Parts Model Brand Model SPEC Specifications Features Features Part Name Thermoelectric Generator Supplier Thermal Enterprises Manufacturer Thermal Enterprises Catalog Number HT1 12710 TEG Datasheet Unavailable Specifications 40mm x 40mm x 3 3mm Operates from 0 16 volts DC and 0 10 5 amps Operates from 60 deg C to 225 deg C Fitted with 6 inch Teflon insulated leads Perimeter sealed for moisture protection Part Name Thermal Grease Supplier Newegg com Manufacturer Arctic Silver Model Number Ceramique Datasheet Unavailable Specifications See Below Arctic Silver Ceramique Thermal Conductance gt 200 000W m2 C 0 001 inch layer Thermal Res
19. ler design and boiler safety that were unknown during initial design Due to this the operating pressure of the boiler was reduced from a gage pressure of 150 psi 1034 kPa to 1 psi 6 9 kPa This significantly increased the safety of the device but drastically lowered the temperature of the hot side of the thermal electric generators from 180 C to 100 C To accommodate this change an available 1 psi check valve replaced the 150 psi pressure relief valve To further increase safety a boiler gage reading both temperature and pressure was added to the front of the device Thermoelectric FT wi Generator Condensing iu Boiler Gage Pressure Relief Check Valve Boiler Condenser Figure 3 Thermosyphon The thermosyphon was tested successfully independently and as a component within the larger system The water in the boiler successfully boiled from this input and was able to pressurize the boiler to 1 psi 6 9 kPa The temperature of the copper pad on which the thermal electric generators sit was measured at approximately 95 99 C The piping between the thermal electric condensing chamber and the boiler also measures a similar temperature The condensing tubes were tested to ensure that they were long enough and that only liquid water would exit at the end The thermosyphon was a major component of the wood burning generator During construction a lot of extra time was devoted to ensuring that it would work successfully and
20. o the different configuration of the thermoelectric generators and an 83 C temperature drop in the hot side thermoelectric generator temperature 14 User Interface and Inverter The circuit layout shown below Fig 7 is a representation of the professional circuit board originally designed last semester The circuit was designed to charge the battery as well as provide power to an inverter The program used is called PCB Artist and was designed by Advanced Circuits to allow customers to design and order simply The red trace and blue trace indicate a two layer board which benefits our project in the way of size They are flexible with their dimensions and allow for a max of a 0 038709 m board for the cost of 33 00 This rate is based on a student discount which allows for us to spend more inexpensively and receive a quality product Turnaround time is fairly quick being only approximately five days Inverter 8 Figure 7 Professional Circuit Board Layout Fig 8 on page 16 is a design of a switching circuitry that will allow the battery to be charged separately from using the inverter The TEGs in series configuration do not provide enough power output to run the fans and also charge the battery This design will work best with more TEGs supplying more current to the battery charging circuit An extra power supply is needed for our design to charge the battery However our tests indicate that it is possible to charge the battery and p
21. ower the fans with enough TEG power The idea is to switch the power from the TEGs and power to the fans ON while keeping the other switch to the inverter OFF Then when the battery is at a charged state approx 12 13V switch the power from the TEGs and to the fans off and turn the switch to the inverter ON 15 This is a design of the professionally fabricated board that has been finalized and ordered The reason behind the consideration of this modification is because we were getting close to 90 mA into the battery with the circuit in Figure 7 but we were having trouble providing enough power to the inverter If you refer to Tables 4 and 5 on page 19 you will see the difference in the circuit output with the circuit working independently as opposed to working in tandem with a separate power supply If this modification does not work then we will work with what we are given from the circuit in Figure 7 above Figure 8 Professional Circuit Board Schematic The LED circuitry is important to our project in a sense of allowing the user to know when the battery is at a sufficient voltage approx 12 V minimum With the circuit shown in Figure 7 the LED lights properly and does the job that it was intended to do from the beginning The designs above Figure 7 and Figure 8 are based on the circuit diagram on page 17 Fig 9 We are using a 3300 uF capacitor before the battery to smooth the output from the TEGs The 18 Ah sealed lead acid ba
22. rgy sources for these generators are not always available wind solar fossil fuels What is needed is a low cost storable easy to use device that provides supplemental energy to the home or emergency electricity if the power is out We believe that a generator using an already built fireplace as the energy source is the natural choice for this request The major benefit of this generator is that the combustion chamber is already available and safe users know how to use it and fuel is readily available The Deliverables There are five deliverables as listed below 1 Working Prototype 2 System Specifications a Design Concept b Block Diagram c CAD Drawing and Analysis 3 Circuit Schematics and Simulation Results 4 User s Manual 5 Bill of Materials Principles of Operation The user will begin by installing the generator to their existing fireplace The device will not be permanent but instead will be installed only when used The actual generator will sit on the hearth outside of the fireplace A device will extend into the fireplace to collect heat and transport it to the generator Once a fire is built and the chamber reaches a sufficient temperature the generator will begin to produce electricity and notify the user that they can plug in a device The user will then be able to plug in any electrical device which uses less than 150W of power to a standard NEMA Type B outlet Special Restrictions The generator must be considered safe w
23. safely Despite many setbacks a working system for heat transport was developed and implemented 12 Thermoelectric Generator Thermal electric generators TEGs were used to convert the temperature differential provided by the thermosyphon and the cooling system into electricity This is done by utilizing the Seebeck effect which consists of a current loop being created by two metals joined in two places with a temperature differential between the junctions This current loop is then used to provide electrical power Preliminary testing of the first thermal electric generator suggested that each generator could produce approximately 7 V and 4 6 A from a 130 C differential To have an output of approximately 14 V and 23A the thermal electric generators were designed in the configuration shown in Figure 4 cl a pmi EZES 7V 4 6A 7V 4 6A 7V 4 6A Figure 4 Original Thermal Electric Generator Configuration 7V 4 6A After the thermosyphon pressure was reduced the team knew that the original configuration would not produce the needed voltage After further testing was completed the thermal electric generators were connected in the configuration shown in Figure 5 This configuration produces 14 6 V and 0 6 A using a temperature differential of approximately 50 C 14 6 V 0 60 A Figure 5 Final Thermal Electric Generator Configuration The thermal electric generators did not provide the total power output that was origin
24. st restrictions or time restrictions These modifications could possibly be implemented in a second prototype The thermosyphon went through many changes during design and construction Some of which left a few parts obsolete In a second prototype the holding tank could be much smaller if not eliminated all together It could be replaced with a simple port allowing the user to refill the boiler The distance between the boiler and the generator should be increased to facilitate larger fireplaces This length could possibly be made adjustable so that the user could personalize the device Lastly the boiler and piping could be built according to ASTM boiler standards to allow higher pressures and therefore higher temperatures to be used This would increase the power output of the thermal electric generators The thermal electric generator design was very successful and worked well with the device as a whole If the thermosyphon could be designed to provide higher temperatures it might be possible to incorporate a microprocessor that would adjust the configuration of the generators to allow maximum power output For example at lower temperatures the thermal electric generators could all be put in series to provide the necessary voltage At higher temperatures the configuration could be modified by putting a few thermal electric generators in parallel therefore increasing the current while keeping the voltage close to 14 volts The current cooling sys
25. tem worked well with the thermal electric generator but a few upgrades are possible The current design uses aluminum heat sinks but it may be possible to use copper heat sinks which have a lower thermal resistivity and would cool the thermal electric generators more efficiently Additionally analysis shows that the use of more fans or fans in different configurations increase the cooling capacity of the cooling system This would particularly be effective if the thermosyphon temperature was increased The electrical system could also be improved in a second prototype Since the voltage from the thermoelectric generators does fluctuate this could be made even steadier by the use of a capacitor A larger capacity battery could be used to increase the life of the generator before it needs to be recharged However this would add a lot of weight to the device as a whole The encasement material was changed from steel to wood during construction because of weight and cost concerns A second prototype might be made from aluminum which would be more durable than the wood and weigh less than the originally proposed steel The current generator is difficult to move because it is heavy and there are no clear lifting points besides the bottom Handles could be affixed to the device in locations that are reinforced to support the weight Lastly to allow the generator to be used with more types of fireplaces adjustable legs could be added to the bottom The team
26. ttery we are using is at maximum when charged to approximately 12 8 12 9 volts The battery in the diagram is represented by a piecewise voltage source for testing purposes only The voltage regulator steps down the voltage from the SLA battery so that the fans will run properly Also the fans draw about 160 mA at 12 V each The diode D2 is used to keep current from flowing back into the TEGs and keep the battery from trying to run them in reverse as Peltier coolers 16 Key A J2 D2 J3 Pri Inverter Key Space 75Q 1N4001GP R5 C1 IA 3300pE in T y A A 1N964B J1 LM7812CT Fan Key A ml LINE VREG a VOLTAGE R 1 COMMON R2 126000 Figure 9 Circuit Diagram 17 You can see in the bottom of picture below the blue LED is lit and the battery voltage was at 12 5 V The extra wires are just for testing purposes to tell us exactly what was happening in the circuit aut da nl A SE Figure 10 Electrical Sub System Testing Table 3 Individual TEG voltages TEG TEG output TEG output voltage current 1 1 33 0 62 2 1 58 0 76 3 1 56 0 77 4 1 44 0 65 5 1 24 0 61 6 1 41 0 69 7 1 47 0 67 8 1 65 0 81 9 1 51 0 73 10 1 41 0 71 Table 3 shows the voltage and current outputs of the individual TEGs With the TEGs all placed in series the output overall is 14 6 V with 0 60 A 18 Table 4 Results of system testing with extra power source
27. utside of the fireplace surface of the device should not exceed 43 degrees Celsius 110 F in order to prevent burning the user Project Overview Introduction The team set out to design a low cost storable easy to use device that provides supplemental energy to the home or emergency electricity ifthe power is out The device that the team designed sits on an existing fireplace hearth and uses the heat from the fireplace as an energy source The wood burning generator answers the call for a sustainable small simple home energy source The design of the wood burning generator went through three main stages Each stage was defined by breakthroughs or changes in the method of heat transport In the first stage shown in Figure 1 a heat pipe was to be used to transport heat from the fireplace to the device This approach pe was simple and required little effort of the part of the user However the design proved above the skill level of the team The second stage shown in Figure 2 was ushered in when Figure 2 Stage 1 Design serious design began A thermosyphon was chosen as the best way to transport the heat and the design was changed accordingly Rather than one pipe entering the fireplace two were needed one for steam and one for water returning to the boiler The third and final stage began when the desired pressure of the thermosyphon boiler was reduced from 180 psi to 1 psi This change greatly increased the safety of th
Download Pdf Manuals
Related Search