David Palmer

Improving efficiency through accurate-boiler sizing and good flue design

Transcript

1. David Palmer Director, The Campbell Palmer Partnership Ltd
2. Improving biomass efficiency through accurate boiler sizing and good design Energy Now Expo 2013 David Palmer BSc MSc CEnv MIEMA The Campbell Palmer Partnership Ltd
3. The Campbell Palmer Partnership Ltd (CPp Ltd) • Biomass & Renewable Energy Consultants • Renewable Energy System Designers • Led the development of the Biomass Boiler System Sizing Tool at the University of Strathclyde • Lead author on a CIBSE Application Manual on Biomass Heating (in preparation) • Delivered the first comprehensive technical training on biomass design, operation and maintenance for CIBSE in October 2012
4. Biomass Efficiency Key success factors: • Assess loads accurately • Size boiler accurately • Incorporate a thermal store • Good control of fossil fuel boilers • Good hydraulic design • Get the flue right • Ensure fuel is within specification
5. Assess Loads Accurately • Model the building(s) to: – Produce heat load profiles – Not just peak loads • Establish load profiles for industrial loads eg dairy, grain dryer • Assess hot water loads • Produce a composite load profile for a cold winter day (the design winter day)
6. Establish the Peak Load Profile Peak load profile at Outside Air Temperature = -3C
7. Size the Boiler Accurately • Most biomass boilers are oversized • Significant capital cost implications • Oversizing results in reduced efficiency
8. Incorporate a thermal store • Boilers work more efficiently when used with a thermal store • Allows size of boiler to be reduced while increasing the amount of heat available from biomass
9. Use the Biomass Boiler System Sizing Tool 400kW boiler = 55% of peak load Thermal store size 97% of annual energy from biomass
10. Biomass Boiler Operation with Thermal Store Biomass boiler runs continuously Building’s load profile
11. Good Control of Fossil Fuel Boilers • Essential to optimise the energy from biomass system • Use temperature sensor on thermal store to disable other boilers when heat is available from biomass • Often requires controls in addition to those available on the boiler
12. Good Hydraulic Design • Essential to achieve RHI compliance • Use a competent mechanical systems designer • Use an installation company with biomass experience • Ask to visit existing installations and speak to their owners • For district heating networks use an experienced district heating designer
13. Get the flue right • Biomass flues have to: – Provide a negative pressure at the boiler under all situations, including an electrical power failure – Disperse fumes and particulates safely & adequately • Consequently, biomass flues need to be significantly higher than gas or oil flues • Keep horizontal sections to a minimum • Incorporate cleaning access, draught regulation & explosion relief
14. Health & safety Too short a flue, or a badly designed flue can: • Cause carcinogenic gases to circulate down to ground level and into adjacent buildings • Result in fumes and smoke release into the boilerhouse, including carbon monoxide Wind direction
15. Health & safety Too short a flue, or a badly designed flue can: • Fail to remove explosive gases from the boiler with the potential for explosion within the boiler • A particular problem with log boilers 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 0 20 40 60 80 100 p p m Minutes Flue Gas CO Concentration Manual Ignition Boiler Entering Slumber Mode Flue Gas CO (ppm) Lower Explosive Limit Upper Explosive Limit NEVER open the fire door when the boiler is slumbering
16. Ensure Fuel is Within Specification • Log boilers: – Logs must be 20% moisture content or less – Wet fuel produces tars which line the boiler and flue and will result in a flue fire • Woodchip boilers: – Ensure the boiler is specified for the wettest fuel likely to be used – Can be difficult to maintain moisture content within specification over the winter
17. QUESTIONS? David Palmer BSc MSc CEnv MIEMA The Campbell Palmer Partnership Ltd t: 01360 312000 e: consultants@campbellpalmer.com