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

2. 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

3. 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

4. Biomass Fuels Moisture content, energy, density comparisons
September 2010

5. Biomass Fuels - Costs
September 2010

6. 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

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

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

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

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

11. 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

12. Thank you
September 2010