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

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.

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.

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

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

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

Types of TAE [3]

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

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)

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

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

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

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

Travelling wave design, Manchester Bangkok, Nov 2009 Operating Frequency 71 Hz. Atmospheric pressure Audio loudspeaker as alternator Max 11.58 We generated [6] 14

Thermo-acoustic Loop, Manchester Bangkok, Nov 2009 Comparison between DeltaEC and experiments Measured Maximum electric power 11.58 W when Q= 900 W (limited by alternator’s maximum excursion) The rig has potential to produce 37 W when Q=900 W, @ eff=4%, using alternator with higher excursion. Confidence is gained for designing 100 Watts generator using Nottingham’s alternator. design 15

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

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

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

SCORE Stove design City University Bangkok, Nov 2009

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

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

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

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, http://www.iea.org/weo/electricity.asp Backhaus, S., G. W. Swift, Traveling-wave thermoacoustic electric generator. Applied Physics Letters, 85[6], pp. 1085-1087, 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 2010. Digital Object Identifier 10.1109/MTS.2010.937029, 1932-4529/10/$26.00©2010IEEE http://www.score.uk.com/research/Shared%20Documents/Techno-Social/Technology_Acceptance_PA.ppt