1. LEAF Log Stove Project LEAF Log stove project Technical team Jacinta MacDermot Rob Gwillim Chris Laughton

2. LEAF Log Stove Project RHI and log stoves RHI =Renewable Heat Incentive Introduced in phases; Non-households first Household phase delayed till 2013 RHPP = Renewable Heat Premium Payment Community groups and social landlords ‘competition’ Biomass boiler - £950 grant (for homes without mains gas heating) No log stoves !

3. LEAF Log Stove Project Why are log stoves not RHI eligible? 1.Difficult to measure heat output 2.Some wood fuel not ‘renewable’ 3.Multi-fuel stove market saturated 4.Air heating without using water – excluded 5.Intermittent vs primary use 6.Fossil fuel – user interaction 7.Fossil fuel (ignition process, pumps, fans) 8.Air emissions 9.Perceived low efficiency

4. LEAF Log Stove Project Improving RHI compatibility - Heat measurement challenges Stoves emit most heat by convection and radiation Some stoves have ‘back’ boilers heating water Pump vs thermosyphon Surface temperatures at various temperatures Chimney losses Combustion air replacing room air Fuel temperature Combustion efficiency varies Calorific content and moisture content

5. LEAF Log Stove Project Improving RHI compatibility - Heat measurement experiment New and old stove installations Machynlleth and Newtown Provide logs of known moisture content Users measure the mass burned each load Temperatures of stoves and flue recorded Flue gas velocity/mass flow calculated at full burn Theoretical efficiency looked up Infra-Red images for spread of heat Theoretical radiant emissivity and convection rates

6. LEAF Log Stove Project Moisture content results Sample Start weight End weight Weight differ Moisture content wet basis Moisture content dry basis Electronic moisture meter ggG%% 60747812921.327.0 A B5654679817.421.0 C100583217317.220.8 D58947111820.025.1 E69756313419.223.8 19.023.523.4

7. LEAF Log Stove Project Recording temperatures

8. LEAF Log Stove Project Infra Red Camera

9. LEAF Log Stove Project Temperature results

10. LEAF Log Stove Project Temperature vs fuel input

11. LEAF Log Stove Project Snapshot averages measured in operation Flue temperature 133 C Top of stove casing 136 C Mid stove casing 106 C Bottom of stove casing 71 C Stove glass 150 C

12. LEAF Log Stove Project Average derived or manufacturer values at rated output Stove efficiencies 75 % (probably gross) Minimum flue draught 12 Pa Mass flow-mass 7 grams/second Flue speed 0.44 metres/second 290 C

13. LEAF Log Stove Project Method A Erhi = Eligible heat for RHI Ein = Calorific value of wood Effic = Efficiency of combustion net (lower) Method A Ein * Effic = Erhi Ein * Effic Erhi

14. LEAF Log Stove Project Method B Ein = Calorific value of wood Eflue = Lost energy up flue Eair = Energy lost through combustion air change Esundry = Energy lost from cold fuel, opening doors Eelec = Pump or fan or ignition power Erhi = Eligible heat for RHI Method B Ein – Eflue – Eair – Esundry – Eelec = Erhi Ein EflueEsundry Eelec Erhi Ein Eair Ein

15. LEAF Log Stove Project Method C Erhi = Eligible heat for RHI Eemis = Energy emitted from stove as radiation Econv = Energy convected from stove by hot air Ewater = Energy circulated from the stove to water Erhi Method C Erhi = Eemis + Econv + Ewater Ewater Econv Eemis

16. LEAF Log Stove Project Method D Erhi = Eligible heat for RHI Eair = Energy lost through combustion air change Esurfaces = Energy heating room surfaces Method D Erhi = Eair + Esurfaces Eair Erhi Esurfaces

17. LEAF Log Stove Project Proposals for improving RHI compatibility For new stoves and chimneys or re-lined For stoves tested to EN 13240 Maintenance service agreement Known wood supply to less than 25% MC Primary heat source – not intermittent use Not possible for appliance to be multi-fuel Thermosyphon heat to be deemed Recording method for proof of use

18. LEAF Log Stove Project Margins of error Temp sensor calibration and insulation Recording (logging) failures Deviation of moisture content samples Chimney calculation – Missing Appliance Data Fuel not meeting manufacturer’s minimum Non-compliant installations – Combustion air Non-representative temperature locations

19. LEAF Log Stove Project The Solar Design Company 0845 519 7914 www.solardesign.co.uk