power electronics integration, packaging and thermal management
TRANSCRIPT
Score StoveGenerating electricity in developing countries using thermo-acoustics
powered by burning bio-mass
Paul H. Riley, Score Project Director
www.score.uk.com
Partners: Universities of Manchester, QMUL, City London and the charity Practical Action.
Background
Score•
Stove cooks, generates electricity and cooling
•
£2M project » 3 years research» 2 years exploitation
•
Large volume manufacture after 2012
•
Extended partnerships
In Poor Rural areas•
>2 Billion are without electricity and cook on an open fire
•
Smoke is a real hazard
The Bid Process
Bid Timetable
May 2006, EPSRC* away day•
Warwick University•
~50 people attended•
Theme: Energy for developing countries
Call for proposals from EPSRCConsortiums formedIdeas crystallisedProposals submittedOne grant (out of 8 submissions) AwardedMarch 2007 Research began
* EPSRC = Engineering and Physical Sciences Research Council. A UK government department that funds UK research up to 80% in value The other 20% comes from the recipient university
Constraints
Unusual call requiring multiple outcomes•
World class research•
interdisciplinary•
Impact on communityPartners•
Universities, produce peer reviewed papers. Recognition•
Charity, deliver measurable improvements. ImpactThe target community•
Improved standard of life. Timeliness, coverage
“God gave us two ears and one mouth; he is telling us something important”
Juxtapositions
Team building•
Ensure they have relevant skills, not just bring in old friends•
Must be able to work as a teamTechnology•
Radical, innovative, world leading•
Based on solid understood technologyProduct•
Low initial cost (can cause high maintenance)•
Low operating cost (requires reliability and low maintenance)Delivery•
Take time to explore the science•
Ensure delivery to developing countryPlanning•
Adventurous, high risk•
Believable and deliverableManagement•
Co-ordinate to minimise duplication, effective use of resources, meet deliverables•
Individual freedom to undertake research
“Imperfect people make perfect teams”
Technical Options (back of envelope sums during submission formation)
Thermo-acoustic engine•
Travelling wave» Currently expensive, but options for cost reduction» Units have been developed in power range» Reasonable efficiency
•
Standing wave» Potentially the lowest cost» Predicted efficiencies just acceptable.» Lack of experimental data at the output power required.
Internal combustion engine with bio-gasifier•
Expensive, high maintenance requirementThermo-piles with wood burning stove•
Expensive, low efficiency, lack of robustnessBio-Fuel fed Stirling engine•
Expensive, maintenance may be an issue
NB: Only low/ zero CO2 options are shown
Project Commencement
The early days
Equalisation of understandingMore detail planning•
Evaluate technical solution, choose front runner•
Identify areas of technical concern•
Acquire resources, match skills with work
Better interface definitionEarly requirements capture, to bound problem•
Followed up by full survey
Define experimentsLearn and re-plan
Standing Wave TAE
Fractional wavelength design•
Frequency determined by alternator, not duct length.
•
Complex acoustic - LA matchingCombustor•
Initially wood burning•
High efficiency•
Low emissions•
Waste heat used for cookingHot Heat Exchanger (HHX) (1)•
500OC gas temperatureStack•
Heats and cools gas packets•
Provides time lag at required frequency, eliminates displacer.
Ambient Heat Exchanger (AHX) (2)•
80OC gas temperature•
Ambient heat exchanger Water cooled, also used for cooking.
Top level Requirements
Power output•
Cooking = 1.6kWth full power 0.75 kW for simmering
•
Electrical = 100We
Cost•
People are very poor so low cost is the main driver
•
Target = £20 delivered to capital city of country
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2 billion units at £20•
60 million units at £60Weight•
In many areas hand carrying is the only option
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Target = 10 – 20 kgFuel•
Consumption < 0.3 g/s (<2 logs per hour)
•
Material initially wood. Looking at Dung and other bio-mass, LPG.
Cost £
Optimisation of the design
A non-trivial, multi- variable problem
Optimisation: Cost
Paradox•
Smoke free stove Nepalese manufacture ~ £25
» Low labour costs» Excludes profit and transport
•
Gas stove (LPG) in UK» £14.99 includes:» Local tax and transport» Profit (manufacturer and retailer)
Low material content is key•
Thin sections•
Strengthened by geometric shape•
High operating frequency
Leads to low weight design
Optimisation examples•
Increased frequency» Alternator efficiency » Thermo-acoustic efficiency
•
Increased pressure» Power output per volume» Mass of containment
•
TAE topology» Standing wave less complex, (Hence
lighter for given efficiency)» Travelling wave more efficient
(Hence less weight per Watt)
•
Working gas» Air is cheapest» Helium allows higher frequency
(hence lighter alternator and TAE)» Discovered travelling wave/ hybrid design
allow high frequency with air
Optimisation: Cost Issues
Power to thickness ratio
0
500
1000
1 2 3 4 5 6 7 8 9
Bar
Demonstrators
Demo #0 To “get our feet wet”Using off the shelf parts.(car radiator, loudspeaker, caravan oven burner)
Travelling wave design Manchester
Linear Alternator for rig work
Stove Design, City
Combustion Rig, QMUL
Business model; Lessons learned
Sustainability•
Low initial capital cost•
Acceptance by community•
Maintenance to achieve long life•
Training•
Low running costBusiness case and benefits•
Individual» £0.70 spend on Kerosene for lighting, gives 3 - 7 year payback
•
Village» Sell units through shop keeper to offset reduction in kerosene sales» Sell electricity to neighbours
•
Country» Minimise imported costs
Partnerships•
Government, manufacturers, distributors, maintainers, financiersIntellectual property protection•
Ensure free to developing country, therefore need control.•
May need to sell to developed world to generate financial interest•
Developed world sales subsidise developing countries? » Even more reason to keep control of IP
Delivery models
Partner with large organisation•
enables rapid deployment•
requires large capital outlay» But sponsors more likely to work with large organisaion
•
Profit motive may be considered against ethosLocal manufacture•
Different skill levels in each country•
Non-centralised training•
Slow ramp up, low penetration•
Low capital outlay•
Need to route to market
•
~ Not necessarily lowest cost of ownership solution•
Aids balance of payments
•
~ Job generation
The answer is not obvious, so we are being flexible with our approach
Final comments
Expectation management•
A technical challenging project that will take time to perfect•
Score Stove in over 55 world wide publications•
Interest from wide area» Communities themselves» Social entrepreneurs» Non-developing country. Eg Tree huggers in Canada.» Government
•
Need to keep interest through research phase, but not put too much pressure on researchers.
Decouple work packages to accommodate plan changes, preserve end dates.Extend partnership through community initiative
Acknowledgements
The Score project is funded by EPSRC, the UK Engineering and Physical Research Council.Thanks to •
Professor Chris Lawn, Dr Catherine Gardner QMUL, Dr Zhibin Yu and Dr Ron Dennis City for permission to use their slides, my Nottingham colleagues Professor Mark Johnson, and Dr Chitta Saha and the Score partners, Dr Artur Jaworski University of Manchester, Dr Keith Pullen City University London, and Dr Teo Sanchez from Practical Action.
Back pocket slides
System losses = 0.8kWth
Power flow (pre-optimisation)
Heat to cooking Hob = 1.6kWth
TAE heat input (HHX) = 2kWth
Heat to Water (AHX) = 1.7kWth
Acoustic power = 300Wa
Alternator Loss = 150Wth
Storage Battery loss = 50Wth
Electrical Output to devices = 100We
• Laptop and light or
• TV, Radio and lights
•Charge mobile phones
Combustion = 4.4kWth