Multi-Disciplinary Senior Design ConferenceKate Gleason College of EngineeringRochester Institute of TechnologyRochester, New York 14623Project Number: 11462THERMOELECTRIC AND FAN SYSTEM FOR COOKSTOVEJared Rugg / Project LeadBradley Sawyer / Lead EngineerThomas Gorevski / Electrical EngineerFahad Masood / Electrical EngineerJeffrey Bird / Mechanical EngineerABSTRACTThe objective of this project was to design athermoelectric module to be coupled with an existingHaitian style cook stove. The purpose for this projectis to work toward a dependable and affordable unitthat could be used in Haiti. The unit would not onlyincrease the efficiency of the stove, but also generatepower for its own fan and possibly auxiliary charging.The target market for Haiti would be vendors cookinglarge quantities of food and over long periods of time.The vendors cooking habits would allow for the mostpower generation through heat. A design wasimplemented which utilizes an axial fan to provideairflow into the stove. Heat energy is taken from thecombustion chamber via a steel rod. The heat energy isconverted to electrical energy by the thermoelectricunit. The unit was tested rigorously and its strengthsand weaknesses became apparent. A significanttemperature differential was able to be maintainedacross the thermoelectric unit but the desiredtemperature differential was not achieved. The mainissue with the system is how the limited powerprovided by the thermoelectric is budgeted betweenthe components and loads. The thermoelectric unit wasable to power the fan, and therefore the system is selfsustaining to a certain degree. Improvements to boththe thermal system and the electrical system could bemade to increase the functionality of the system.NOMENCLATURECFMPWMTEGhDhcubic feet per minutePulse Width Modulationthermoelectric generatorconvection coefficienthydraulic diameterINTRODUCTIONBillions of people around the world dependon biomass for everyday cooking fuel. Cooking isoften performed on a semi-open stove or over a simplethree-stone fire. These methods of cooking are veryinefficient and lead to high fuel usage and airbornepollution. Cooking is often performed indoors andtherefore the use of biomass cooking has a negativeimpact on the health of people who must live in theheavily polluted air conditions. Inefficient cookingmethods have especially had a major impact on Haiti,the poorest country in the western hemisphere. Haitiwas once covered with forests, but is now less than 4%forested. Much of the deforestation is a result of theneed for cooking fuel. The most popular fuel used inHaiti is charcoal.The introduction of oxygen to anycombustion process will, in general, allow for moreefficient, complete and clean combustion. The primaryCopyright 2008 Rochester Institute of Technology
Proceedings of the Multi-Disciplinary Senior Design Conferencefunction of the thermoelectric and fan system is toprovide forced airflow to the combustion chamber ofthe cook stove without the need of an external powersource. A thermoelectric unit is utilized to convertthermal energy taken from the combustion processinto electrical energy. Electrical energy provided bythe thermoelectric unit is used to power a fan and aUSB port. The USB port can be used to charge thebatteries of an „auxiliary‟ device such as a cell phone.The thermoelectric generator, which is theheart of the system, develops electrical power when atemperature differential is maintained across it. Thethermoelectric generator (TEG) takes advantage of theSeebeck Effect to create electrical power. The SeebeckEffect happens when a temperature difference iscreated between two different metals orsemiconductors. A voltage differential is createdbetween the materials and when connected in a loop(circuit) current flows. This configuration is alsoknown as a „thermocouple.‟ Figure 1 shows how theSeebeck Effect works. Wires constructed of twodifferent metals (metal A, metal B) are joined at twopoints. When a temperature differential between thetwo junctions is present (T1, T2) a voltage is created.FIGURE 1 – SEEBECK EFFECTA thermoelectric generator consists of multiple “legpairs” of p-type and n-type semiconductors. Each legpair is a thermocouple which produces electricalpower when a temperature difference is created acrossit. The leg pairs are connected together in seriesthrough thin metal interconnects. The leg pairs aresandwiched between two thin wafers of ceramicgiving the thermoelectric generator structural rigidity.The ceramic substrate also provides a smooth contactsurface that thermal energy is conducted through.Figure 2 shows a typical thermoelectric generator.This is the style generator that is used in thethermoelectric fan module.Page 2FIGURE 2 – THERMOELECTRIC GENERATORThe target market for this thermoelectric andfan system is Haiti and, more specifically, a streetvendor; therefore, one of the major design objectivesis to produce a low cost unit. In conjunction with thelow cost, the system should also be simple and easy touse. The beauty of a thermoelectric unit is that it is asolid-state device, meaning it has no moving parts, andis intrinsically simple (from a physical stand-point).Another design requirement is that the unit requires aminimal amount of user actions in order to operatecorrectly. User interactions can include adjustment ofany knobs, switches or any general physicalinteraction with the unit. Simple operation of the unitalso includes a design that can easily be removed orconnected to the stove.The design of the thermoelectric and fansystem has five main facets. The first facet istransferring heat energy from the combustion chamberof the stove to the hot side surface of the TEG. Thesecond facet is removing heat from the cold sidesurface of the TEG, the third is providing a source offorced airflow to the stove, the fourth is controllingand managing the flow of electrical energy and thefifth is packaging the components in an efficient andsimple manner. This thermoelectric and fan project(P11462) is a second generation design as a previousRIT Senior Design team attempted to fulfill the samerequirements. The design of the P11462 unit attemptsto take the previous team‟s design successes andfailures into account.LITERATURE REVIEWProject 11462 is the second iteration of thethermoelectric and fan system. The previous project(P10462) documented much of the importantinformation from their iteration. This year the teamattempted to learn from this documented information.The main issues faced by P10462 were amalfunctioning electrical system and insufficientcooling of the TEG. The custom heat sink used byProject P11462
team 10462 appears to have insufficient surface area; afact echoed in their technical write-up. In addition, useof a simple bent metal fan may have provided too lowa flow for proper cooling. Another issue that wasmentioned was a suspected problem with thermalresistances between the ceramic substrate of the TEGand the surfaces of the thermal bridge (heat conductionrod) and heat sink. The team felt that heat was notbeing conducted well between the ceramic substrate ofthe TEG and the surfaces on the conduction rod andheat sink.On the electrical front, team 10426experienced multiple problems with managing thepower allowances between the electrical devices. Animportant consideration that was discovered throughreading the research by previous thermoelectric teamswas that the thermoelectric must be operated in arange where it can provide sufficient power. Whilemainly the shortcomings of team 10462‟s design havebeen addressed, several test methods from their designprocess were also used. A similar approach is used tobetter model and empirically determine the heattransfer coefficient of the fire. Also, ideas fordetermining the flow rate out of the combustionchamber of the stove are used.function of the system is to provide air to the stovefire. In all, 13 functions were enumerated. For eachfunction different ways to satisfy the function weredetermined during brainstorming sessions. Forexample, for the provide air to the stove fire function afan, compressed air source, and bellows werebrainstormed.After the brainstorming sessions werecomplete, charts known as Pugh Diagrams were usedto compare the different means. The selection criteriaused were cost, complexity, life-span, durability,safety, package-ability, efficiency, and functionality.For this design we used the 2010 design as a datum.An example of one of the Pugh diagrams used isprovided in Figure 3. Using the “passing” designs foreach function several final permutations were created.Ideally, all of these permutations should satisfy thecustomer needs. These different overall designs werethen also compared using a Pugh diagram analysis anda final overall design was selected.PROCESSThe final proposed design was the result ofcareful consideration of past team experiences,pairwise comparisons of possible solutions, and firstprinciple feasibility calculations. The design processwas driven by several important customer needs. First,the system needed to provide forced airflow into thecurrent stove (P10461). As stated earlier the systemhad to work with a charcoal fire and have a relativelycheap cost. Fourth, the customer wanted the system torequire no user interaction to protect the system.P10462 planned to use an LED light to tell the userthat the system was overheating. The customer did notlike this approach and wanted to reduce the reliance onuntrained users. Additionally, for obvious reasons theproposed system needed to be safe to operate andeasily transportable. Finally, use of a thermoelectricdevice was required.From these customer needs severalengineering specifications were developed. Ideally, thefinal proposed design must be able to satisfy all ofthese specs. First, the flow rate of the air into the stovemust be marginally 0.3-0.7 kg/min. Second, the unitmust cost 27.50 or less. Finally, based on theproperties of the TEG the maximum temperature ofthe hot side of the TEG is 275 C.Several lessimportant engineer specifications also were developedand helped to drive the design of the system.With these customer needs and engineeringspecifications in mind, functions were determined forthe various portions of the system. For example oneFIGURE 3 – EXAMPLE OF PUGH CHARTOnce the final overall design was determined,a high level system architecture was created. Thatarchitecture is show in Figure 4. The architectureshows each subsystem and the energy flow betweenthe systems.FIGURE 4 – SYSTEM ARCHITECTUREThe final design consists of a square crosssection metal housing which functions as an air duct.Inside the housing resides a fin style aluminum heatsink along with an axial fan to provide air flow. Figure5 shows the design of the thermoelectric and fansystem. The air is ducted axially from the top of the
Proceedings of the Multi-Disciplinary Senior Design Conferencestove to the bottom and is then turned 90 degrees toenter the bottom of the stove. This axial design wasimplemented to fit the system (mainly the large heatsink and fan) in close proximity to the stove. This wasdesirable for both package-ability purposes and alsobecause keeping the unit close to the stove has aminimal effect on the stove‟s center of gravity.The stove the unit couples to is the firstgeneration of the Haitian Cook Stove (P10461). Thestove was meant to reduce emissions and fuelconsumption by 50%.FIGURE 5 – THERMOELECTRICSYSTEMOne of the most important parts of the design isthe heat sink which removes heat from the cold side ofthe thermoelectric. The simple finned heat sink waschosen because of its simplicity and also becausecommercially available finned heat sink extrusions arecheap and plentiful. The finned heat sink also creates aminimal pressure drop when compared to pin styleheat sinks. The heat sink is fastened to the metalhousing via four cap screws.The manner in which thermal energy isremoved from the combustion process for use by thethermoelectric module was an important point ofdebate. In the end a “ruler style” steel thermalconduction rod was selected. Although the thermalconductivity of steel is significantly less than that ofaluminum, initial tests suggested that the temperaturesgenerated by the fire would cause significant damageto aluminum. The conduction rod enters the side of thestove through a slot and protrudes into the combustionPage 4chamber much like a large fin. The other end of therod transfers energy to the thermoelectric through asmall pocket machined in the face of the rod.Compression is maintained on the thermoelectric viafour 6-32 cap screws that thread into the heat sink. Thethermal bridge that these cap screws create betweenthe conduction rod and the heat sink is an issue. Inorder to mitigate this problem contact between thethreads of the cap screw and the hole in the conductionrod in which they pass through was minimized.Stainless steel washers sit underneath the cap of thescrews. A circular recess in the conduction rod securesthe washers with a reasonably tight tolerance. Thesewashers serve a two-fold function. Because stainlesssteel has a relatively low (compared to steel) thermalconductivity the washers help to decrease the thermalbridging through the 6-32 cap crews. Also the washersconstrain the rod from any lateral motions that coulddamage the TEG.The need for a method in which to control theair flow into the stove led to the implementation of the“bypass” design. Initially the air flow into the stovewas going to be controlled by varying the voltage tothe fan. This idea was abandoned due to the need forconstant substantial airflow over the heat sink toprovide cooling to the TEG. The bypass is a simplehinged door located downstream of the fan and heatsink. When opened, the bypass allows some air to beducted to atmosphere instead of into the stove therebycontrolling of the strength of the combustion processinside the stove.The thermoelectric module (Taihuaxing TEP1264-1.5) is used for this project. At a specifiedtemperature difference (200 C) the module willoutput 4 watts. In order to achieve this temperaturedifference the system was designed to operate at asustained hot side temperature of 300 C and asustained cold side temperature of 100 C. Mostthermoelectric modules, including this one, areapproximately 4% efficient. Therefore it was assumedthat for a desired output of 4 watts, 100 watts of heatenergy would need to be passed through the TEG unit.A design value of 130 watts was estimated to accountfor thermal losses in the system and for losses in theTEG unit. Once these design parameters wereselected, the conduction rod and heat sink could bedesigned to pass 130 watts of energy through the TEGwhile maintaining a 200 C temperature differentialacross the TEG.Fan ConsiderationsInitially, the proposed maximum nominalspecification for air flow was 1.2 kg/min. Using STP,this value converts to 36 CFM. The flow into thestove will depend on both the resistance to flow of thestove as well as the pressure drop provide by the fan.Project P11462
First, the stove‟s impedance needed to be determined;it was decided that this would be determinedempirically. A pressure tap was placed in the inlet tothe stove. Air was then ducted into the stove with asmooth PVC pipe with a flow meter inline. Using apressure transducer an outlet voltage was recorded andconverted to units of inches of water. Using the knowncross-section of the PVC the flow velocity from theflow meter was converted into a flow rate. The flowrate was varied and several data points were taken.The stove‟s impedance was then plotted as pressuredrop versus flow rate and is shown in Figure 6.Pressure Drop(inches H2O)Stove owrate (CFM)FIGURE 6 – STOVE FLOW IMPEDANCE TESTAfter examining this plot and a generaloverlay of an estimate of a very efficient computer fanoperating at 2 watts it quickly became apparent thatthe goal of 36 CFM of flow into the stove would notbe plausible. Subsequently, a desire to betterunderstand the effect of the air flow rate on the fire‟sproperties emerged. In order to do this an additionaltest was run. Again using the PVC with the flow meterinline to duct air into the stove, a fire was started in thestove and the stove was allowed to reach a “hot start”temperature. Next, 2 L of water at room temperature(50 F) was placed in a pot. After the charcoal wastopped off to a set level the pot was placed on thestove and the time to boil was measured. Thisexperiment was done at three different flow rates: 20,30, and 40 CFM. The results are shown in Figure 7.Starting WaterTemp (deg F)Flow Rate(CFM)Time to boil(min)51.1203:5448.6303:1550.9403:13FIGURE 7 – EFFECT OF FLOW RATE ON BOILTIMEAs shown in Figure 7, decreasing the flowrate by half had little effect on the time to boil. Withthis information in mind, the air flow rate specificationwas pushed down to a nominal max value of 22 CFM(0.7 kg/min).The design relies on the fan running at themax flow rate at all times. This is due to the fact thatthe proper operation of the heat sink relies on good airflow through it. The amount of air entering the fire iscontrolled by a bypass. Some of the air flow can beducted out to atmosphere while the rest is ducted intothe stove. Currently, this is done through the use of apivoting door. Because of this design and theengineering specification of being able to produce arange of flow rates into the stove, the fan must be ableto produce the maximum flow rate at all times.An axial fan was chosen to provide the airflow to the stove. The axial fan was chosen for amyriad of reasons. First and foremost, axial fans arecheap and plentiful which fits into the constraint thatthe system must be cheap and easily producible. Anequally important reason is that most axial fans arerelatively efficient and thus require low power tooperate. The fan must operate at a low power becausepower is at a premium in the system. The axial fan isalso desirable because it is well packaged and selfcontained which makes it easy to integrate into thesystem. The life span of an axial fan is also ofimportance. A long fan life span is desirable and anaxial fan provides this. The only real issue presentwith using an axial fan is that they do not providelarge pressure drops.Based on the stove impedance test describedearlier and through some research into the max flowrate and max pressure drop of axial fans that would fitthe necessary size (80mm) and necessary powerallowance (2 W) it appeared that it would be difficultto find a fan that fit the system‟s needs. With thisknowledge the search for a suitable fan proceeded bylooking for an 80mm fan that would produce the mostflow rate and pressure drop for 2 Watts. The fanselected was a Sunon fan model number ME80251V10000-A99.Once the parts had arrived the flow rate andpressure drop capabilities of the fan needed to beverified. This was done using a test rig designed tospecifically test axial fans. The test rig is a PVC tubewith several pressure taps downstream of the fan. Theflow of the fan can be varied using a cone at the outletof the PVC tube. The closer the cone is to the outlet ofthe tube the greater the resistance to flow and thushigher the pressure drop. The flow rate was measuredusing a hot wire anemometer that was inserted into themiddle of the pipe. Because the fan speed is also afunction of input voltage the fan speed was heldconstant at 12 volts during the test (12 volts is therecommended operating voltage of the fan). Thepressure drop was varied and the resulting flow raterecorded. Figure 8 displays the results of the fan test.
Proceedings of the Multi-Disciplinary Senior Design ConferencePressure Drop (inH2O)flow comes from the material itself. Using theequations for the adiabatic fin and general 1-D heattransfer a Matlab program was developed to testdifferent lengths and widths for a given rod thickness.The program works by iterating on each „half‟ of therod until the temperature at the meeting points of thehalves (which occurs at the outer wall of the stove) isequal. This means that the amount of heat flux that thefin part of the rod is transferring to the insulated partof the rod is the correct amount to achieve a 300 CTEG hot side temperature .12 V Fan Curve0.2Page 60.150.10.0500204060Flowrate (CFM)FIGURE 8 – FAN PRESSURE DROP VS.FLOWRATEThis data was plotted against the stoveimpedance curve. Despite being one of the mostefficient fans available the operating point of thesystem was still too low. In order to combat thisproblem the inlet holes to the combustion chamberwere enlarged. This modification should decrease thepressure drop into the stove and shift the optimal pointto a higher flow rate. This will allow a higher flow rateof air into the combustion chamber of the stove.Conduction Rod ConsiderationsThe design of the heat conduction rodinvolved many factors. The two main constraints onthe design are the desired temperature at the hot sideof the TEG, and also the heat flow into the TEG. Asstated before, the target hot side temperature was 300 C, and the target heat flow through the TEG was 130watts. These pieces of information allowedconstraining the design to sizes that would allow forthat level of heat conduction. A test was run todetermine the overall heat transfer coefficient (Uvalue) of the fire. This test involved inserting a verylong steel rod into the combustion chamber.Thermocouples were placed in the rod just outside ofwhere it penetrated the stove wall which allowed for aheat flow to be calculated. During this test thetemperature of the fire itself was measured. Firetemperatures measured anywhere from 700-1000 C.In the end, the heat transfer coefficient of the fireseemed to vary greatly with the level of the charcoalwith respect to the rod. Heat transfer coefficients from16.2-44.2 W/m2K were measured.With the design constraints in mind, theconduction rod was modeled. The rod was broken upinto two sections. The section inside the combustionchamber was modeled as a fin with the adiabatic tipcondition. The portion of the rod that lies outside thewalls of the stove was assumed to be perfectlyinsulated, and therefore the only resistance to heatHeat Sink ConsiderationsThe heat sink was designed to maintain aTEG cold side temperature of 100 C while dissipatingthe 130 watts of energy coming from the TEG unit.Some of the assumptions made were a worse case of30 C ambient air temperature and a constant flow of20 CFM over the heat sink. In final testing, it wasdetermined that a constant flow of 19 CFM wasachieved at a fan input voltage of 9 volts. In order tocalculate the heat transfer characteristics of the heatsink the convection coefficient (h) must be calculated.The flow between the fins of the heat sink wasmodeled as internal, fully developed flow with. With this Reynolds number, the „h‟value can be calculated using the following equation:(1)The convection coefficient was calculated to be:Once the „h‟ value of the heat sink iscalculated, the dimensions of the heat sink determineits thermal resistance. The calculated thermalresistance of the heat sink used in the thermoelectricsystem is approximately 0.5 C/W. The manufacturersclaim for this heat sink profile is 0.7 C/W/3 inches oflength. It was assumed that this value is for naturalconvection .The final design of the mechanical systemincludes a „ruler‟ shaped heat conduction rod with ashallow pocket milled in it to seat the face of thethermoelectric. The overall dimensions of theconduction rod are 6.95 inches long, 2.75 inches wide,and .5 inches thick. These dimensions were chosenbecause they were the closest standard dimensions tothe ones generated by the Matlab program. The teamalso used an insulated cover over the section of theheat conduction rod exposed to the environment. Thisnot only to protected the user from the heat, but helpedminimize convection losses on the exposed section.Project P11462
The rod is joined to the heat sink through 4 sockethead cap screws, using springs to maintain pressure onthe thermoelectric. The springs were not part of theoriginal design, but after the first experiment it wasclear that something was needed based on how loosethe screws had become due to the heating cycle. Theextruded aluminum heat sink is a seven fin design witha matching pocket milled in it to seat the cold side ofthe thermo electric. The overall dimensions of the baseare 3.15 inches by 4 inches. The height from thebottom of the base to the top of the fins is 2.88 incheswith a base thickness of 0.38 inches. The base surfaceof the heat sink is insulated from the housing surface,but slightly thermally coupled by the two screws thathold the heat sink in place on the housing. Thehousing is a “boot” shaped design with the overalldimensions of 10 inches by 5.18 inches by 3.27inches. The “toe” of the boot fits into the air intake ofthe stove with the long section turning upward.ELECTRICALThe electrical systems were designed aroundcertain needs by the customer. From an electricalstandpoint the priority list is as follows: 1) Provide anairflow into the stove and across the cold side of theTEG, 2) be able to charge a battery pack which willallow the fan to run at startup without TEG power, 3)be able to charge a secondary battery pack that will beable to power the USB device. Figure 9 displays thegeneral schematic of the electrical system.integrated circuit was chosen and a Maximtechnologies application was used. After testinghowever, it was found that the MAX668 boostapplication consumed too much power and only wasable to output 6.2v to the fan from the TEG. Thereforeafter conversations with advisors, peers, and onlineresearch the TI PTN04050 boost DC-DC converterwas chosen to provide the regulated output voltagesthat we needed. The PTN04050 was chosen for itssimplicity and its low power consumption.The regulated output of the PTN04050 wasset by changing the value of RSET in figure 10 below.The adjustable DC output range for the boostconverter is; 5v to 15v from a DC input with a rangeof 2.95v to 5.5v and the output that we determinedwas sufficient for the fan was 9v. The input of thefirst converter was being fed directly from the outputof the TEG module. At steady-state the TEG canprovide a voltage of 4v which is a sufficient turn-onvoltage for this boost converter, allowing the desiredregulated output voltage. This boost has its outputconnected to two charging circuits and a primary inputof a switching circuit. The design of the DC-DCBoost Converter may be seen in Figure 10.FIGURE 10 – DC-DC BOOST SCHEMATICFIGURE 9 – ELECTRICAL SCHEMATICBoost ConverterIn order to satisfy the customer‟s needs werequired circuits that could regulate the TEG andbattery output voltages. The design called for threeseparate DC-DC boost converters; one from the TEGto the fan via the switching circuit, one from the fanbattery pack to the fan via the switching circuit, andone from the other battery back to the USB port. Forall three DC-DC converters the MAX668 buck-boostBoth input terminals of the second and thirdDC-DC boost converters are connected to the outputnode of their respective charging circuit (fan batterycharger and auxiliary battery charger). The input ofthe "auxiliary converter" is connected to the output ofthe auxiliary charging battery pack which will providethe required turn-on voltage for a USB cable (5V). AUSB cable was used to be able to charge a personalelectronic device such as a cell phone because it is astandard and readily available interface. The input ofthe "fan converter" is connected to the fan chargingbattery pack. This converter has its output connectedto the secondary input of a switching circuit. Bychanging the value of the resistor, RSET, to 0Ω and
Proceedings of the Multi-Disciplinary Senior Design Conference4.56kΩ in the auxiliary converter and the fanconverter respectively their outputs were set to 5v and9v respectively.Battery Charging CircuitThe bq2003 charging IC was selected due toits low power characteristics and because of itsversatile charging applications. The charging circuitwas configured for a battery pack consisting of fourAA cells, a 12.7 mA trickle charge current, and a 1.25A charging current. The charging circuit alsoincorporated negative thermal coefficient resistors totrack the temperature of the battery pack so thatcharging would cease under high temperatures as asafety measure. The design of this circuit can be seenin the Figure 11.Page 8sufficiently small to ensure that the battery stayscharged to 90% of its capacity and does notovercharge. The trickle charge is set by changing theresistor value of R10 which, the current across thisresistor is determined to be the trickle charge currentinto the battery.The battery packs were chosen with certainconstraints in mind: it had to power the fan at startup,be robust, and be affordable. To satisfy theseconstraints two battery packs were chosen: one withfour AA NiMH cells to charge the auxiliary deviceand the other containing three AA NiMH cells to runthe fan at startup. The chemistry of rechargeablebatteries was taken into consideration and the NiMHchemistry was chosen due to its lack of memory, highenergy density, and relative low cost. These batterypacks had been sized to be able to provide the turn-onvoltage for the boost converter, and to provide enoughpower for their respective circuits.Switching CircuitFIGURE 11 – BQ2003 TRICKLE CHARGECIRCUITThe bq2003 initiates charging by samplingthe voltage at pin 1, CCMD, and if CCMD is low thebq2003 initiates charging provided that the voltage atthe BAT pin is greater than the voltage at the MCVpin in the absence of a battery and BAT is greater thanMCV in the presence of a battery.Temperature sensing in the bq2003 is used asa safety measure to increase the longevity of thebattery packs. A safe battery pack temperatu
The stove the unit couples to is the first generation of the Haitian Cook Stove (P10461). The stove was meant to reduce emissions and fuel consumption by 50%. output 4 watts. FIGURE 5 – THERMOELECTRIC SYSTEM One of the most important parts of the design is the heat sink which removes heat from the cold side of the thermoelectric.