Wood to Warmth – Biomass Fuels and Heat Energy Calculations Michael Beech TV Energy September 2010

Biomass Fuels As general guide, the energy available from different biomass fuels can be summarised as follows: Logs Seasoned to 20%MC, 4100kWh/tonne, 1900kWh/m3 (hardwood, stacked), 1400kWh/m3 (softwood, stacked) Pellets <10%MC, 4700kWh/tonne, 2800kWh/m3 minimum Chips 30%MC, 3300kWh/tonne, 950kWh/m3 (hardwood), 720kWh/m3 (softwood) September 2010

Biomass Fuels CV hardwood (broadleaves) = CV softwood (eg. pine, SRC) Higher growth rate of softwood offset by its lower energy density CV goes down as moisture increases. But weight of fuel increases with higher water content. September 2010

Biomass Fuels Moisture content, energy, density comparisons September 2010

Biomass Fuels - Costs September 2010

Heat Energy Calculations Calculating heat load & woodfuel use Fuel bills (existing build) -> kWh i/p -> system efficiency -> kWh o/p -> % from biomass boiler -> biomass efficiency -> Biomass fuel kWh -> biomass fuel kWh/tonne -> tonnes/m3 System efficiency – old boilers, EE improvements possible? Biomass boiler heat >90% of annual heat load ideally Biomass efficiency – losses during start up, thru’ buffer tank For new build, need to know the calculated annual heat demand to determine woodfuel use September 2010

Heat Energy Calculations Heat loads – Mixed commercial/ domestic Winter Summer September 2010

Heat Energy Calculations Heat load variation - seasonal January June/ July December September 2010

Heat Energy Calculations Biomass and conventional boilers - winter Heat outputs. 150kW biomass boiler, 350kW oil boiler Buffer tank activity. 5000litre, 20deg.C deltaT Maybe no oil boiler, so larger biomass boiler and buffer, or more than 1 biomass boiler September 2010

Heat Energy Calculations Biomass boiler - summer Heat output Buffer tank activity Run biomass September 2010

Heat Energy Calculations Summer heat supply – alternative options Additional smaller o/p biomass boiler – higher capital cost, available space, central heat losses vs. heat use, cost/ benefit, flexibility Conventional boiler – convenience, use existing? energy costs / CO2 emissions Electric immersion heating – convenience, low capital cost, highest operating cost/ CO2 emissions, night rate option? Solar thermal system – capital cost, space requirements, orientation, lowest operating cost/ CO2 emissions, size carefully, cost/ benefit vs. biomass fuel use Or a solar thermal system! September 2010

Thank you michael.beech@tvenergy.org September 2010