BIOMASS DESIGN BEST PRACTICE
Gas Boiler
CT Flow
Gas Boiler
Gas Boiler
Gas Boiler
Gas Boiler
Biomass Boiler
Back-end Valve
HM
Biomass Boiler Pump
U/F Flow DHW Flow U/F Return
CT Return DHW Return
The characteristics of efficient and reliable installations can be summarised as:
Chimney height determined by technical and emission dispersion needs alone
Chimneys are designed in accordance with harmonised BS EN Standards, have no bends, minimal horizontal run length and are CE marked where they are pre- fabricated system chimneys.
The heating load has been adequately assessed, preferably using monitored data
Minimum loads are adequate throughout the working year
Initial system design was in conformity with the Biomass Decision Support Tool. Typical designs size the biomass boiler at 25% to 50% of peak load. Thermal storage and auxiliary boilers support peak loads
Systems with adequately sized 4-port thermal stores have fewer operating problems
System hydraulics respect basic physics, and are formally proven to provide controllable systems
Biomass boiler control arrangements configured as an integrated system with demand side loads, and not an add-on to an existing system
Effective control strategies properly utilise thermal storage to maximise use of biomass heat, and to support peak loads
Commissioning must be proven for all load conditions.
DESIGN CHECKLIST
to provide robust guidance for the whole procurement chain. And so serious is the risk of poisoning by carbon monoxide that the HSE last month released a Safety Notice on the storage of wood pellets for biomass boilers. Since 2002, at least nine fatalities have been recorded in Europe following entry into inadequately ventilated wood pellet storage areas – three of which were caused when people entered domestic wood pellet stores. Wood pellets for boilers are normally
stored in a large sealed hopper/tank or room. Due to the enclosed nature of these areas, the atmosphere inside can become toxic. Another potential hazard is that wet biomass pellets can self-heat above 105°C and spontaneously combust. Pellets must be kept dry. Rain must be kept out, and
www.cibsejournal.com
condensation must not drip onto biomass. Also biomass chips stored for more than one month with a moisture content of more than 35% can support a mould that causes farmer’s lung – a disease as deadly as asbestosis. In addition to these hazards, there is
also a possibility of carbon monoxide being present in storage areas because of a ‘back-flow’ of flue gases via the fuel supply mechanism from the boiler. This can be caused by inadequate equipment being installed or by poorly designed flues. According to the Carbon Trust, a
survey in 2010 revealed that only 30% of installations are working well. There are around 3,000 commercial biomass boiler installations operating in the UK, with new installations running at approximately
December 2012 CIBSE Journal 23
At the end of 2012, there may be less than 12 people in the UK with adequate knowledge (of procuring biomass boiler systems)
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68