System Design Requirements for the SCORE Project

Catherine GardnerChris 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 andelectricity 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 m2

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 designEnergy (1)

Nottingham Conf. April 2012

Battery charge/ discharge efficiency of 67 % implies 150 We 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 designEnergy (2)

Nottingham Conf. April 2012

1.5 kg wood /hr of average LCV (low moisture) : 6.0 kW

2.0 kW thermal power for electricity generation : 4.0 kW for cookingplus 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) = 1.7kWth

Heat to cooking hob = 2.5 kWth

TAE heat input (HHX) = 2kWth

Acoustic power = 300Wa

Alternator Loss = 150Wth

Battery loss =50 Wth

Electrical Output to devices = 100WeCombustion = 6.0 kWth

Losses=1.5 kWth

    

                             

 

Heat to Water (AHX) = 1.7kWth

Heat to cooking hob = 2.5 kWth

TAE heat input (HHX) = 2kWth

Acoustic power = 300Wa

Alternator Loss = 150Wth

Battery loss =50 Wth

Electrical Output to devices = 100WeCombustion = 6.0 kWth

Losses=1.5 kWth

Implications for system designGeneral

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 designHeat transfer

Nottingham Conf. April 2012

Maximum area of regenerator interfacing with the stove : 0.07 m2 ?

2.0 kW hot-end transfer requires 30 kW/m2

Radiation between black-bodies at 1120 K and 1000 K gives 32 kW/m2

Convection in steady flow of 20 m/s through a 10 mm pipe across a 120 K difference gives 6 kW/m2

Acknowledgements

Funding by the Engineering and Physical Sciences Research Council: EP/E04462X/21

Partners in the SCORE Project

Nottingham Conf. April 2012