System Design Requirements for the SCORE Project Catherine Gardner Chris Lawn Queen Mary, UoL Nottingham Conf. April 2012

TOPICS Sources of information on cooking and electricity requirements Specification of requirements for the Project stove and thermoacoustic device Implications for system design Nottingham Conf. April 2012

Sources of information on cooking and electricity requirements Nottingham Conf. April 2012 SCORE Requirements, report on Nepal Visit, 2007, by the Project Director, Paul Riley, and address to this Conference Cooking and Lighting Habits in Rural Nepal and Uganda: SCORE Project, Teo Sanchez, Ron Dennis and Keith Pullen, this Conference, 2012 Target : Households in Yangalot in Nepal

Specification of requirements for the Project stove and thermoacoustic device 1) Fuel Nottingham Conf. April 2012 Wood as the primary fuel Sticks/ logs up to 750 mm, with diameters between 25 and 60 mm Wood drying area in the stove Consumption < 4.4 kg /dwelling / day with operation 3 hours /day

Specification of requirements for the Project stove and thermoacoustic device 2) Normal performance Nottingham Conf. April 2012 Boil 4 l of water in 15 mins Provide some space heating Meet Nepalese ambient air quality standards Flue pipe up to 3 m can be installed Operate for > 5 years with some maintenance Footprint < 1 m 2

Specification of requirements for the Project stove and thermoacoustic device 3) Electricity generation Nottingham Conf. April 2012 No maintenance No interference with normal cooking Stored in car batteries at 13.6 V Providing 300 Wh from 3 hrs operation Quiet <50 dBA at 1m Pre-assembled parts with unit price in Kathmandu of <£40 Weight < 20 kg

Implications for system design Energy (1) Nottingham Conf. April 2012 Battery charge/ discharge efficiency of 67 % implies 150 W e must be generated through the 3 hours to give 300 Wh Generator efficiency of 50% determines that 300 W of acoustic energy must be absorbed by the alternator Efficiency of conversion of thermal to acoustic energy of 15 % (?) requires 2000 W thermal input

Implications for system design Energy (2) Nottingham Conf. April kg wood /hr of average LCV (low moisture) : 6.0 kW 2.0 kW thermal power for electricity generation : 4.0 kW for cooking plus 1.7 kW rejected at cold end (for cooking or space heating) Boiling 4 l in 15 mins requires 1.7 kW Boiler efficiency of 75 % implies 1.5 kW lost and 2.5 kW for cooking on hobs Overall efficiency of electricity supply : 1.7 % !

Nottingham Conf. April 2012 Implications for system design: Sankey energy diagram Heat to Water (AHX) = 1.7kW th Heat to cooking hob = 2.5 kW th TAE heat input (HHX) = 2kW th Acoustic power = 300W a Alternator Loss = 150W th Battery loss =50 W th Electrical Output to devices = 100W e Combustion = 6.0 kW th Losses= 1.5 kW th Heat to Water (AHX) = 1.7kW th Heat to cooking hob = 2.5 kW th TAE heat input (HHX) = 2kW th Acoustic power = 300W a Alternator Loss = 150W th Battery loss =50 W th Electrical Output to devices = 100W e Combustion = 6.0 kW th Losses= 1.5 kW th

Implications for system design General Nottingham Conf. April 2012 Helium at high pressure not an option (availability and containment) Air at pressure difficult (maintenance and cost) Natural circulation for cold end cooling (maintenance and cost) Natural draught stove (chimney to improve air quality) Thin material for loop likely to be too noisy

Implications for system design Heat transfer Nottingham Conf. April 2012 Maximum area of regenerator interfacing with the stove : 0.07 m 2 ? 2.0 kW hot-end transfer requires 30 kW/m 2 Radiation between black-bodies at 1120 K and 1000 K gives 32 kW/m 2 Convection in steady flow of 20 m/s through a 10 mm pipe across a 120 K difference gives 6 kW/m 2

Acknowledgements Funding by the Engineering and Physical Sciences Research Council: EP/E04462X/21 Partners in the SCORE Project Nottingham Conf. April 2012