1. Paul H. Riley Score Project Director
Application of Thermo-Acoustic, electrical generating engines in rural areas.
Paul H. Riley Score Project Director

2. Market Survey (from Score Project)
Nepal survey (results confirmed in Kenya)
Yangalot village in Hagam
Husband see chart on right
Wife
better cooking position
low smoke
better education for children
Business case
Household:
70p per month saved on kerosene for lighting,
Score pays back in < 3 years
Village
shop sells and maintains score to offset kerosene sales.
Country
carbon credits
cascade manufacturing.

3. Achieving low cost Options
PV, thermo-pile, off grid generators, steam turbine Hydro, wind.
Capital outlay and maintenance dominate cost of electricity.
Large scale penetration (100 millions) requires cost below €90 (5000 rupees), very large subsidies, or significant CO2 emissions.
Thermo-acoustic engines (TAE) convert heat to electricity with no moving parts, are thus potentially cheap to manufacture
However, best efficiency is 18% and very difficult to design.
Electrical conversion efficiency not important when cooking stove thermal efficiency is ~10%
The potential low manufacturing and maintainability cost and zero emissions of TAE, more than off-set difficulties. Design costs can be amortise over large volumes.

4. Possible TAE Applications
Electrical output
Domestic stoves that also generate electricity (Score Stove) ~ 100We
Community power generation 3k- 11kWe
Combined Heat and Power (CHP) 3kW – 15 kWe
Fuel
Wood
Bio – gas
Agricultural waste
Fossil: Propane, Kerosene etc.
Waste heat recovery
Solar

5. How does Score work? Uses Thermo-Acoustics [2] Wood or dung is burnt
Exciting new technology
No moving parts
Stirling engine with no pistons Relies on acoustic waves
Making it cheap and reliable
Difficult to design but low cost manufacture
Used in Space probe and a Natural Gas liquefying plant
Wood or dung is burnt
A specially shaped pipe gets red hot
Another part of the pipe is cooled
This generates sound at 100 Hz
very noisy inside >170 dBA
Outside whisper quiet hum
Then a Linear Alternator turns the sound into electricity
The waste heat is used for cooking

6. The Principle of the ‘Standing-Wave’ Thermo-acoustic Engine (Yu and Jaworski, 2009)
Bangkok Nov 2009 6

7. Types of TAE [3]

8. Low onset temperature design [4] [5]
Electrically powered rigs
Omit parasitic heat losses
Field implementations
Conductive heat loss can dominate > low efficiency
Two ways to tackle
Lower parasitic loss
Lower TAE onset temp
Multiple regenerators
Can lower onset
Aster 70K Th-Tc with 4 stage
Useful for waste heat recovery #1
p_c #2
Twin heat exchangers and regenerators #1 #2 #3 #4
Quad TAE

9. Score Twin Results Score Demo0#3 onset temperature Th-Tc = ~100 K
75mm feedback pipes
onset temperature Th-Tc = ~100 K
loop power > 80 W at Th-Tc = 180 K
At 4600 Pa
near traveling wave SWR  1.8, 7We
100mm Pipe
15We achieved
(half wavelength design)

10. TA Engine load characteristics
Constant temperature heat source
Heat exchangers
Maximum loop power independent from load
Load #1
Load #4
Load #3
Load #2

11. The Score Stove Mission
The Score Stove Mission. For £20 it will cook and generate electricity To help over 2 billion rural poor people world wide, (600 Million on the Indian sub-continent) Powered by wood, dung or other fuel Potential to save 10 Mt Carbon per year

12. Why Score?
2 billion people cook on an open fire with no electricity: 600M[1] in India-sc
Smoke bad for health
Over-use of scarce wood supply
Many stove designs
Insufficient impact
need billions, not 100’s thousands
Understanding social context is key
Poverty < $2 per day
Motivation, e.g. mobile phone
Inhibitors
Low power (20W) is enough to start
Familiarity with local culture
EPSRC and DFID* want impact
From research money
To increase UK science base
Photographs courtesy Practical Action
* EPSRC = Engineering and Physical Sciences Research Council. DFID = Department for international development, each are UK government funded organisations

13. The Score Stove Project
The Charity Practical Action and the Universities of City, Manchester, Nottingham, Queen Mary
£2M research
fuel burning Stove that can cook, generate electricity and provide cooling for use in Developing Countries.
5 years started in 2007
research to 2010 thereafter exploitation part funded until 2012
Both High Technology and Social Science content
Two way learning is an important element in research
Target of 100 Watts electrical for £20 in 1 million quantities
with half the wood and no smoke
World-wide interest
in 60 publications, over 10 different languages
Score Community Launched
engaging with 10 developing countries and growing

14. Travelling wave design, Manchester
Bangkok, Nov 2009
Operating Frequency 71 Hz.
Atmospheric pressure
Audio loudspeaker as alternator
Max We generated [6] 14

15. Thermo-acoustic Loop, Manchester
Bangkok, Nov 2009
Comparison between DeltaEC and experiments
Measured Maximum electric power W when Q= 900 W (limited by alternator’s maximum excursion)
The rig has potential to produce 37 W when Q=900 eff=4%, using alternator with higher excursion.
Confidence is gained for designing 100 Watts generator using Nottingham’s alternator. design 15

16. Travelling Wave Implementation
Bangkok Nov 2009
Diagram courtesy Queen Mary University of London [6]
15 Watt rig at The university of Nottingham (Propane driven) 16

17. Rigs that prove performance
Design for Low Cost [7]
User requirements
Eg 15W – 100We, 30 - €90 (5000 rupees)
System design
Rigs that prove performance
Eg 100Hz operating frequency
Work with large scale manufacture
Component design
Design Iterations
Field tests
Cost evaluation
Market Evaluations

18. Where to manufacture?
To make impact (100 Million pa) needs mass manufacturing technology
India well placed for TAE technology manufacture
Linear Alternator: Dai-ichi Philippines, China
High volume high quality speaker manufacturer
Also needs route to market
Training
Sales and marketing
Maintenance
Transport cost
Can dominate in remote areas, eg Nepal (especially for heavy items)
Current thinking is therefore to have some local assembly to include heavy items, locally sourced
Requires training in local areas

19. SCORE Stove design City University
Bangkok, Nov 2009

20. Is Score useful? [8] Simulated Score Stove Satisfaction
12 houses in Nepal
10 – 20 W electrical
No smoke, less wood
Similar number in Kenya
Satisfaction
100% used electricity for lighting helping education, social
80% used for radio
32% mobile phone charging
16% sold electricity
Interest from Developed world
Benefit can be gained from as little as 15We, longer term 100We required

21. Scientific challenges present and future
Current tools
One dimensional only
Difficult to use for novice
Only validated over limited range
Parasitic losses dominate the conversion efficiency. Must pay significant attention to detail to improve efficiency
Requirements
Library of reference designs
Performance
Validated
Optimised for application
Single, dual, triple quad and multi, TAE’s
Ability to describe 3 D effects
Both analytical and diagnostic capability
Ability to design with manufacturing constraints
develop low cost designs
adapt to manufacturing process
Variety of TAE gases and pressures
Air, Argon, Helium
1 Bar to 30 Bar

22. Acknowledgements
The Score project is funded by EPSRC, the UK Engineering and Physical Research Council.
Thanks to the Score Team
Professor Chris Lawn, Dr Catherine Gardner
Queen Mary University London,
Dr Artur Jaworski, Dr Zhibin Yu
University of Manchester
Dr Keith Pullen and Dr Ron Dennis
City University London
Dr Teo Sanchez
Practical Action
Professor Mark Johnson, and Dr Chitta Saha.
My Nottingham colleagues
Aster Technology the Netherlands, Mr Kees deBlok

23. References
People with no electricity (millions) in 2008, Afghanistan = 23.3, Bangladesh = 94.9, India = 404.5, Nepal =16.1,Pakistan = 70.4, Sri Lanka =4.7, Total for South Asia = 613.9,
Backhaus, S., G. W. Swift, Traveling-wave thermoacoustic electric generator. Applied Physics Letters, 85[6], pp , 2004
Scott Backhaus, Condensed Matter and Thermal Physics Group, Los Alamos National Laboratory “Thermoacoustic Electrical Cogeneration” ASEAN-US Next-Generation Cook Stove Workshop
K. De Blok Aster Thermoakoestische Systemen, Smeestraat 11, NL 8194 LG Veessen, Netherlands“Low operating temperature integral thermo acoustic devices for solar cooling and waste heat recovery, Acoustics 08 Paris.
K. De Blok Aster “Novel multistage traveling wave thermo acoustic power generators” ASME August 1 August 2010, Montreal
Yu Z, Jaworski A J, Backhaus S. In Press. "A low-cost electricity generator for rural areas using a travelling wave looped-tube thermoacoustic engine". Proceedings of the Institution of Mechanical Engineers - Part A: Journal of Power and Energy.
Catherine Gardner and Chris Lawn “Design Of A Standing-Wave Thermo-acoustic Engine”, The sixteenth International Congress on Sound and Vibration, Krakow 5-9 July 2009.
Riley, P.H., Saha, C., and Johnson, C.J., “Designing a Low-Cost, Electricity Generating Cooking Stove”, Technology and Society Magazine IEEE, summer Digital Object Identifier /MTS , /10/$26.00©2010IEEE