Akshaya Srivastava, Daryl Duran, Mark Pinder, Vrishank
Raghav, Narayanan Komerath
Daniel Guggenheim School of Aerospace Engineering
Georgia Institute of Technology
Atlanta, Georgia USA
INTERNATIONAL CONFERENCE ON POWER, SIGNALS, CONTROL AND COMPUTATIONS
Trissur, India, January 3-06, 2012
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Georgia Institute of Technology komerath@gatech.edu
Experimental Aerodynamics & Concepts Group
Micro Renewable Energy Systems Laboratory
Conceptual Design of a
Thermoelectric Edu-Kitchen System
Introduction
Improve air quality, fuel efficiency,
steady lighting and clean drinking
water supply to kitchens.
Issues & Objectives
•Multidisciplinary testbed for micro
renewable energy technologies.
•Demonstrate closure of conceptual
design for an integrated solution.
• Active Control Problem to optimize
power, air quality, fuel use, storage.
Approach
•Thermoelectric (TE) generation.
•Battery storage.
•DC fan/blower to optimize fuel-air
ratio,ventilation and TE cooling.
•Ejector nozzle.
•Thermocouple/ RTD for feedback.
•LED floodlamp for lighting.
•UV LED for water purification.
Georgia Institute of Technology komerath@gatech.edu
Experimental Aerodynamics & Concepts Group
Micro Renewable Energy Systems Laboratory
Aim
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Add-on, modular solution to existing kitchens
Charge battery on fire used for cooking evening meal
Provide enough light for one child to do 3 hours of homework each day
Provide enough air flow range to optimize fuel-air ratio at cooking intensity
Safe, rugged, simple for use by residents
Inexpensive components (in mass production)
Adaptable to wide range of operating conditions
Georgia Institute of Technology komerath@gatech.edu
Experimental Aerodynamics & Concepts Group
Micro Renewable Energy Systems Laboratory
Requirements
Woodburning kitchen stoves provide a source of power to bring electric lighting,
pollution control and water sterilization to communities.
A 13-watt thermoelectric converter module operating at 225 degrees Celsius
recharges a battery using the heat from the fire.
Battery-powered DC fan drives air into the stove, cooling the TE module and
optimizing the fuel-air ratio for high fuel efficiency and least pollution.
A temperature sensor provides feedback to adjust fan flow.
5-watt LED floodlamp provides steady lighting so that a child may learn.
A milliwatt LED is used to sterilize drinking water.
1. Does the design close with the selected parameters?
2. Is enough air flow variation available from the fan to ensure optimal
stoichiometry in the flame?
3. Can costs at wholesale level be brought down to reasonable levels for
adoption by NGOs and community programs?
Georgia Institute of Technology komerath@gatech.edu
Experimental Aerodynamics & Concepts Group
Micro Renewable Energy Systems Laboratory
Concept & Question
Experimental Aerodynamics & Concepts Group
Micro Renewable Energy Systems Laboratory
Components Identified
Georgia Institute of Technology komerath@gatech.edu
Experimental Aerodynamics & Concepts Group
Micro Renewable Energy Systems Laboratory
System Concept
Georgia Institute of Technology komerath@gatech.edu
Bismuth
Telluride alloy
13 watts rating
225 Deg. C max temperature
Still working to achieve anywhere near this power curve!!
Georgia Institute of Technology komerath@gatech.edu
Experimental Aerodynamics & Concepts Group
Micro Renewable Energy Systems Laboratory
13-watt thermoelectric converter module
•12 volt DC Fan from discarded computer
•Nozzle/casing from 12-oz aluminum
beverage can
TSI “Velocicalc” integrated
hot-wire anemometer sensor
traversed across nozzle exit to
obtain mass flow rate by
integrating velocity profiles.
Georgia Institute of Technology komerath@gatech.edu
Experimental Aerodynamics & Concepts Group
Micro Renewable Energy Systems Laboratory
DC Fan/Blower Performance
•1kW heating rate assumed in stove.
•Wood properties assumed as sample (Black Spruce)
•Heat release rate per unit mass consumed
•Mass of wood consumed per second
•Mass of air needed for perfect reaction (stoichiometry)
•Factor of 2 for imperfect mixing
•Fan flow rate needed
•Fan power needed, from experimental data
•Range of stoichiometry/ excess air available
•Power excess left at design conditions
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Georgia Institute of Technology komerath@gatech.edu
Experimental Aerodynamics & Concepts Group
Micro Renewable Energy Systems Laboratory
Conceptual Design Estimation Process
Georgia Institute of Technology komerath@gatech.edu
Experimental Aerodynamics & Concepts Group
Micro Renewable Energy Systems Laboratory
How much power does the fan need to provide twice the
minimum air flow
needed to ensure complete fuel consumption? Only about
2 watts.
•UV Waterworks system by Ashok Gadgil and Vikas Garud
at Lawrence Livermore national labs, sterilized drinking water and eliminating
several harmful bacteria including e-coli.
• Broadband content of 40- watt fluorescent black light sufficient for effective
sterilization.
•254 nanometer far-UV radiation killed well over 99 percent of bacteria present
in water, quickly enough to use the blacklight over slow-flowing water.
•Luckiesh General Electric Corporation (1920s): dosage of over 200 microwattminutes per square centimeter was adequate for 100 percent destruction of ecoli in water even if strain had evolved through previous doses of same
radiation.
•260 to 270 nm, centered probably at 264 nm, is much more effective, since this
includes resonance wavelengths of the DNA of these bacteria.
•LEDs with output over this narrow range can thus achieve the same results as
the earlier fluorescents, at milliwatts.
Georgia Institute of Technology komerath@gatech.edu
Experimental Aerodynamics & Concepts Group
Micro Renewable Energy Systems Laboratory
Ultraviolet Germicidal Unit For Drinking Water
Power Budget:
Fan: 3 watts
LED lamp: 4 watts
LED water purifier <1 watt
Total < 8 watts
Steady-state TE Module supply for DT > 170 C
Charging of battery above this level during operation
Single-Unit Costs
TEM $100
DC fan $8
Coke can $0
LED light $25
270nm LED
+ power unit $200
Total: $333
Per unit, mass-production targets
TEM $5
DC fan $2
Coke can $0
LED light $5
270nm LED + power unit $1
Total: < $13 (INR 650)
Less than the cost of treating a child for one day’s hospitalization!
Project funding must come from enlightened govt. health/education programs.
Georgia Institute of Technology komerath@gatech.edu
Experimental Aerodynamics & Concepts Group
Micro Renewable Energy Systems Laboratory
Technical Design closes, Policy Case for Economics OK
•Computing the heating from a stove burning assorted scrap wood,
•Enhancing mixing inside a cluster of wood pieces,
•Modeling and improving entrainment by a low-Reynolds number fan nozzle,
•Designing the EduKitchen insert,
•Protecting the thermoelectric module and
•Cooling TEM enough for optimal power generation and safety.
Current work
• TEM testing not successful yet: needs optimization of TEM system.
• Detailed characterization of jet boundaries and flow entrainment.
• TEM envelope cooling
• Scrap wood combustion modeling
• 264nm LED incorporation.
• Possible application of Thermo PhotoVoltaics (TPV)
Georgia Institute of Technology komerath@gatech.edu
Experimental Aerodynamics & Concepts Group
Micro Renewable Energy Systems Laboratory
Challenges Leading-edge Research Capabilities In Several Areas
Micro Renewable Energy Systems Laboratory
First conceptual design of the EduKitchen, shown to close.
Basic concept of integrating devices for thermoelectric generation, fuel
efficiency improvement and air quality improvement, and basic lighting and
drinking water sterilization, is technically viable.
Power levels obtained with single TEM at very modest heating rates and
temperatures from a domestic wood stove are sufficient to operate a DC fan,
DC LED floodlamp generating the equivalent of a 40-watt incandescent lamp.
Fan-driven air reaches a speed of several meters per second, adequate to
greatly augment natural convection and ensure clean, efficient heat release.
An estimation procedure is laid out to estimate stoichiometry and to generate
design curves for various levels of heating needed from the stove.
The paper is also intended to convey the multidisciplinary nature of this
research project.
Georgia Institute of Technology komerath@gatech.edu
Experimental Aerodynamics & Concepts Group
Conclusions
This study was enabled by NASA Grant NNX09AF67G S01, the
EXTROVERT initiative to develop resources for cross-disciplinary
innovation. Mr. Tony Springer is the technical monitor.
Georgia Institute of Technology komerath@gatech.edu
Experimental Aerodynamics & Concepts Group
Micro Renewable Energy Systems Laboratory
Acknowledgment