The Electric EcoFogao - BioEnergy Discussion Lists

The Electric EcoFogaoDan MastbergenDr. Bryan WillsonSachin JoshiColorado StateUniversityRogerio MirandaWinrock International

The Problem2.4 Billion people use biomass for cooking and heating1.6 Billion people have no access to electricity

The Problem• Most people usingstoves do not havemodern lightingUsing . . . .• Light from openfire• Burning sticks• Kerosene Lantern

The Solution• Most stoves generate a very large amount ofthermal energy ~ 1-515 kW• Much of this energy goes right out the chimney• Our goal was to create a device to turn a smallfraction of this energy into electricity• The most promising design is a thermoelectricgenerator (TEG)

Lighting Options• Candle 12 Lumen• Kerosene Wick Lantern 40 Lumens• 1 W LED 40 Lumens• 3 W Cold Cathode Fluorescent Light (CCFL) 120 Lumens• 13 W Compact Fluorescent (CFL) 800 Lumens• 60 W Incandescent 730 Lumens

Thermoelectric Generator• Develop a Thermoelectric generator toconvert waste heat to light• Thermal energy is converted intoelectricity by the Seebeck effect

Thermoelectric GeneratorConsists of• Thermoelectric Module•Cooling Fan•Hot heat Sink•Cold heat sink

The Ecoforno StoveThe TEG was incorporated ontothe Ecoforno StoveThe goal was to produce enoughenergy to run a 15W compactfluorescent light for 3 hours45 W-hrs per day15 W-hrs per meal

Incorporating the TEG• Initial chimney locatedTEG• Produced just over 1 W• Temperatures were toolow (150 – 200 C)• Need (300 – 400 C)

Incorporating the TEG

Modifying stove for TEGEcoforno with oven removedReconstructed for use with TEG

TEG Design – Module and HeatSink Selection•Heat sinks were modeled using a heat sink modeling softwareprogram•Various heat sink – module combinations were modeled in aspreadsheet

Heat Sink SelectionThe following heat sinks were identified ascandidatesBonded Fin Heat Sink Pin Fin Heat Sink Extruded Heat Sink

Bench Top TestingHeat sink thermal resistance and Module powerwere determined from a series of bench top tests

Preliminary TestingPreliminary testing wasperformed to asses:•Generator power•Stove Temperatures•Transient behavior

Stove and Generator TemperaturesTemperature Vs. Time900800700Temperature (C)60050040030020010000 10 20 30 40 50 60 70 80 90 100Time (min)T Comb. Chamber (C )T hot gas (C )T hot sink (C )T cold sink (C )

Preliminary Test ResultsPower and Energy Accumulation vs. Time for Two 10W Modules2520W and W-hr1510Power (W )Energy Accumulated (W-hr)500 10 20 30 40 50 60 70 80 90 100Time (min)• 17 W-hr Wper meal with 3 meals per day generates51 W-hr Wof energy per day• Desired amount: 45 W-hrWStove set-up with two 10-Watt modules produceenough energy to power a 15-Watt CFL for 3 hours

CSU vs. Field TestingComparison of Combustion Chamber Temperatures at CSU and inthe FieldTemp (C)100090080070060050040030020010000 20 40 60 80 100 120 140Time (min)CSU test 1 CSU test 2 Ecoforno LunchEcoforno (wet wood)Ecoforno Tea• CSU testing followed similar path as on-site field testing

Electrical Power Management• Needs to boost voltage to charge12 V battery• Needs to regulate charging anddischarging of battery• Needs to turn DC-DC converterand fan on and off

Electrical Power ManagementThe power circuit is still in development, estimated cost is $15

Total System CostIn quantities of 1000, TEGsystem cost is $170 20W$7.75/wattIn larger quantities, localmanufacturing ~ $5-6/WItemQuanityCost per item(@ 1000 units)CosttotalHot heat sink (Thermaflo) 2 $7.00 $14.00Cold heat sink (Thermaflo) 2 $20.00 $40.00Module (Thermonamic) 2 $35.00 $70.00Thermal spreader 2 $3.00 $6.00Battery (Power Sonic) 1 $6.00 $6.00Fan (Vantec) 2 $10.00 $20.00Power Circuit (Maxim, Mouser) 1 $15.00 $15.00Solar power $5-8/wattTEG System Cost $171.00The next generation ofthermoelectric modules willreach 3-4 times the poweroutput of current modules $2/wattCost per Watt @ 24 W $7.13Stove Cost 1 $100 $100Total Cost for TEG system andStove$271

Conclusion• A thermoelectric generator has been successfullyincorporated into the Ecoforno stove• In order to generate the power desired the TEGmust be incorporated into the stove design• The generator produces enough power to run a15 watt CFL for three hours• The system cost for 1000 units is $170 $7.75/watt• Costs will be further reduced through highvolume/local manufacturing

Future Work• Complete construction of power managementcircuit• Develop a standardized test cycle• Hot side heat sink redesign (less restrictive)• Continue to incorporate the latest technology inmodules, manufacturing, and electronics toreduce cost• Field Testing – reliability, user interation, , etc.

Questions?

Average Energy FlowsNet Battery Power: 11.25 - 1.0 = 10.25 W