¿Thermoacoustic Co-Generation? -...
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1/22/2010 1 Engineers in Technical and Humanitarian Opportunities of Service (ETHOS) 30 January 2010 ¿Thermoacoustic Co-Generation? Steven Garrett United Technologies Corp. Professor of Acoustics Penn State University
Transcript of ¿Thermoacoustic Co-Generation? -...
1/22/2010
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Engineers in Technical and Humanitarian Opportunities of Service (ETHOS) 30 January 2010
¿ThermoacousticCo-Generation?
Steven Garrett
United Technologies Corp. Professor of Acoustics
Penn State University
1/22/2010
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The LogicCook stoves generate heat.
Engines convert heat to workEngines convert heat to work.
Work can generate electricity.
Electricity can power a fan.
Fans improve cook stove efficiency.Fans improve cook stove efficiency.Also improves health and fuel flexibility.
Excess electricity is valuable!Rural Cambodians pay $2/kW-h.
Purpose of this Demonstration
• There are some very simple heat engines.
Si l h d t• Simple has advantages.– Inexpensive
• Does not require “exotic” materials
– Few or no moving parts• Low maintenance
• Nothing’s free.– Simple is usually not as efficient (e.g., TE modules)
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Heat Is Not All Created Equal
• The 1st LawE i d
Thot
Combustion
– Energy is conserved
Qexhaust+ Work = Qinput
• The 2nd Law– Entropy increases
ΔS = ΔQ/T
Heat
Engine
Work
Qinput
ΔS = ΔQ/T
Exhaust
TambientQexhaust
hot ambient
input hot
T TWorkEfficiency
Q T−
= ≤
Thermodynamics
“It is the only physical theory of universaltheory of universal
content that, within the framework of
applicability of its basic concepts, will never be
overthrown.”
Albert Einstein, "Autobiographical Notes", 1949
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Familiar Heat Engines
Pistons, Pushrods, Cams, Valves
It’s all aboutabout
phasing!
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Closed-Cycle Engine Technology
1895 Rider-Ericsson 2001 WhisperGen
Resonant Acoustical Phasing[For a natural engine]
Gas MassGas Spring
No Motion All M ti
Gas Compliance ↔ Gas Inertance ⇒ Harmonic Oscillations
No MotionAll Compression
All MotionNo Compression
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Thermoacoustic Engine Demonstration
• Heat and Heat Engines
– Cook stoves are hothot– Heat can produce work
• Convert work to electricity– Generators
– Linear alternators
• External combustion– Free piston Stirling
– Steam (piston or turbine)
– Thermoelectric
– Thermoacoustic
• Engine Requirements
– Robust
– Inexpensive
– Low maintenance
Standing-Wave Prime Mover - Lagrangian Model
Hot HeatExchanger
Stack Cold HeatExchanger
λ/4
T+++ 3 T+
T++
δκThermalDiffusionDistance To1T++
Qhot
42 Qcold
T++++ T-
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Optical Laser - Acoustical Laser
Some working examples from LANL
100-Watt Class TASHE and Alternator,Collaboration with Northrop GrummanTh=650oC; Tc=30oCThermal-to-electric efficiency = 18%
Three-stage Cascade engine.Thermal-to-acoustic efficiency~20+%
m
1.5
m
Slide 14
20 c
m
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Overview of the alternator
Preliminary Modeling Results (LANL)
80
90
100
1200
1400
TW Heat input
30
40
50
60
70
80
Elec
tric
al o
utpu
t (W
)
400
600
800
1000
1200
Hea
t inp
ut (W
)
SW Heat input
TW Elec. output
0
10
20
0 0.005 0.01 0.015 0.02
Engine cross-sectional area (sq. m)
0
200SW Elec. ouput
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The SCORE Project*• Stove for Cooking, Refrigeration and Electricity
– Goals were unrealistic – 100 watt battery charger
– Refrigeration has been put “on hold”Refrigeration has been put on hold
• Efforts were directed toward self-education– They tried running before they could crawl.
– 18 months spent writing thermoacoustic design code.• DELTAEC has been functioning worldwide for 20 years
– Stove development not existing stove adaptation.
– Experiments on topics with published results.
• Gross misrepresentations to press!
* or how to misdirect $3.3M (2.0 M£) of development fund toward purely academic pursuits.
Initial Design Concept for Thermoacoustic Duct
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Current Stove and Thermoacoustic Duct Design for a Travelling Wave
Thermoacoustic Loop at Manchester: Original Configuration
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Thermoacoustic Loop at Manchester
B & C speaker :Rc = 5.5 Ω
Thermoacoustic Loop at Nottingham
cFn = 40 HzQms = 4.5
Load fn(Hz)
HHX (oC)
AHX (oC)
P1(mBar)
VL(V)
IL (A) Pout
36 Ω 74 414 47 40 19.5 0.557 10.8 W
24 V battery
74 412 46 42 29.6 0.662 19.6 VA
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Original Energy Flow Requirements for STOVE
Bangkok, Nov 2009
Heat to cooking Hob = 1.6kWthHeat to Water (AHX) = 1.7kWth
TAE heat input (HHX) = 2kWth
Acoustic power = 300Wa
Alternator Loss = 150Wth
Storage Battery loss = 50Wth
Electrical Output to devices = 100WeCombustion = 4.4kWth
Losses0.8kWth
S u m m a r y
• Cook stoves can leverage proven technologies.– Electrical co-generation exists but needs to be merged. g g
– Improves ease of use, reduces cost, increases durability.
• Success requires deployment of a billion units!– This requires low cost, incentive to adopt, and financing.
C ti ld d i d ti• Co-generation could drive adoption.
• High-efficiency LED lighting, charge cell ‘phones.
