September Wood to Warmth – Bioenergy Appliances Michael Beech TV Energy

September Bioenergy Conversion Combustion Complete oxidation of biomass Energy -> hot combustion gases Gasification Partial oxidation of biomass Energy -> fuel gas (low heating value) + tars, particulates Pyrolysis Thermochemical conversion of biomass w/o oxygen Energy -> bio-oil (fast pyrolysis) + gas, solids (charcoal)

September Bioenergy Conversion Combustion (Boiler) Simple technology, heat -> water or steam via heat exchanger. Wide range of biomass fuel types and specifications possible, boiler designs can accommodate. Gasification (Gasifier) Fuel gas -> furnace or IC engine. Intermediate gas stage affords higher efficiency & control, often for CHP applications. Usually demands tighter biomass fuel quality. Pyrolysis (Pyrolyser) Bio-oil produced. Gives higher density fuel, decouples process to provide energy storage (although unstable), useful for CHP. Fine, dry biomass particles usually required.

September Bioenergy Appliances Stoves (room heater) Pellets or logs (coal may be substituted for more power!) Heat to surrounding space via radiation, + some convection Poor control of heat output with log stove, pellets better With back boiler or heat bank - to radiators, hot water tank Up to 20kW possible Efficiency - up to 75% (cf. open fire 10 – 20%) £ £4000 installed (w/ back boiler)

September Bioenergy Appliances Stoves Log stove with flow and return pipesPellet stove feeding thermal store

September Bioenergy Appliances Boilers Specific designs to accept logs, pellets or chip Hot water to space heating, hot water systems, industrial/ agri-processes, swimming pools etc Steam for direct application, process heat, CHP (large scale) All larger than equivalent size oil or gas boiler, plus space for fuel store (woodfuel has low energy density vs. fossil fuels)

September Bioenergy Appliances Log boilers Domestic applications mostly Require daily manual loading, regular cleaning Accumulator tank or back boiler for heat storage and output control Advantage of widely available, minimally processed fuel Logs £120/tonne bulk delivery, typical Typically £7,000 - £15,000 system installed

September Bioenergy Appliances Log boilers With accumulator tank

September Bioenergy Appliances Pellet boilers Often domestic scale, but also non-domestic applications where space or fuel delivery access is difficult (e.g. urban locations) Automatic ignition, compact boiler with integral hopper (small domestic) and/ or separate fuel store Hot water to end use, or via buffer tank for additional control Pellets supplied in bags (small domestic) or bulk delivery via tanker, free flowing fuel, relatively energy dense for biomass Bagged delivery equivalent to heating 55p/litre Bulk delivery equivalent to heating 40p/litre ~£10,000 + system installed (small domestic scale)

September Bioenergy Appliances Pellet boilers 60kW domestic

September Bioenergy Appliances Chip boilers Large domestic scale, or non-domestic applications Automatic ignition, bulky, with separate fuel store Hot water to buffer tank, or district heating network can provide buffer on larger systems Chip delivered via container vehicle under gravity, fuel bridges easily, low energy density £100/tonne or 3p/kWh typical (1/2 – 2/3 cost of LPG/ oil) Fuel cost variable with source, delivery quantity, distance Higher capital cost vs. pellet systems (boiler & fuel store) Lower fuel costs than pellet systems

September Bioenergy Conversion Chip boilers - Types Stoker burner Compact, lower cost, fast response, low minimum output, <30%MC/ consistent fuel required Moving grate More bulky, higher cost, efficient combustion, higher minimum output wet/ variable fuel possible

September Bioenergy Appliances Woodchip boilers 540kW Kob boiler 220kW Froling boiler

September Bioenergy Appliances Woodchip boiler & feed system 500kW Endress boiler Woodchip auger feed

September Bioenergy Emissions Emissions from combustion of woody biomass NOx (nitrogen oxides) Cause acid rain and smog. A by-product of complete combustion, minimised by combustion air control, control of residence time of flue gas, combustion temperature. CO (carbon monoxide), soot, hydrocarbons, tar compounds and unburned particles Generally harmful. Arise from incomplete combustion, result in sooting up of flue. Emissions must be adequately dispersed. NOx and CO result from combustion of fossil fuels too

September Bioenergy Emissions Emissions can be managed Boiler/ stove design & maintenance Fuel specification/ control Exhaust stack design Adequate flue height above roof, and termination above any roof ridge in close proximity. Biomass boiler/ flue supplier can assist, or consult Building Regulations Part J for guidance.

September Bioenergy Emissions Permits Regulations depend on boiler size, location and fuel type. For boiler plant <20MW heat input using clean wood - Under Clean Air Act 1993, a Local Authority may declare: Smoke Control Areas – therefore plan to use an Exempt Appliance AQMAs - approach LA for guidance, seek emissions information from the boiler supplier For fuel input rate >45.4kg/hr (~135kW output with 30%MC fuel), LA will approve the flue height

September Thank you