Specifications

Below are two examples which detail the calculations for identical situations using dierent boiler types:
Example 2 - Wood pellet boiler
Wood pellet boiler - 20 kW output, 90% eciency, running for 1,750 hours per year (typical)
kWh required = 20 / 0.9 x 1,750 = 38,888 kWh per year (note divide the kW output of the boiler by the
eciency to get the actual fuel input energy required)
Wood pellet energy content = approximately 4.8 kWh/kg @ 8% moisture content.
Therefore:
Annual pellet requirement = 38,888 / 4.8 = 8,101 kg = 8.101 tonnes.
Example 3- Wood gasication log boiler
For a wood log boiler, an additional requirement is a buer cylinder. Approximately 55 litres of buer cylinder
capacity is required per kW output of the boiler.
Wood log gasication boiler - 20 kW output, 90% eciency, running for 1,750 hours per year (typical)
kWh required = 20 / 0.9 x 1750 = 38,888 kWh per year (note divide the kW output of the boiler by the
boiler eciency to get the actual fuel input energy required)
Wood log energy content = approximately 4.0 kWh/kg @ 20% moisture content.
Therefore
Annual wood log requirement = 38,888 / 4 = 9722 kg = 9.722 tonnes.
Note: Typical energy contents of wood fuels are given in Table 1.
The SEAI domestic heating cost and carbon comparison tool can be used to analyse the possible fuel
consumption and running costs per year of dierent heating sources in a dwelling.
Quality Standards for Wood Fuels
The Committee Europeen de Normalisation (European Committee for Standardisation) (CEN) has published
a number of standards for solid biofuels. These standards have been adopted by the National Standards
Authority of Ireland (NSAI) and therefore represent the default case in Ireland. Other standards are common
in the EU and represent approximately equivalent standards, for example Germany DIN 51731 (pellets &
briquettes); Austria ÖNORM M 7135 (pellets & briquettes); Swedish Standard SS 187120 (pellets) and SS
187121 (briquettes); French Pellet Club Voluntary Quality Charter.
The standards cover characteristics including raw material used, dimensions, moisture and energy content
to ensure high quality, standardised fuel. Fuels that do not conform to the European standards may contain
contaminants that cause harmful emissions and damage your heating system. It is therefore recommended
that you check your fuel conforms to one of the above standards or that your supplier can reassure you that
the fuel conforms to an equivalent standard, for example in Canada or USA.
In countries where wood fuels have been established for many years, for example Austria, it is common to
nd “markers” in the fuels. The marker usually contains a serial number that can be traced to a manufacturer
or supplier.