Environmental Engineering Reference
In-Depth Information
12.5.1 Firewood Boilers
Certain facts need to be determined before a fi rewood boiler is installed. Wood-fi red
systems may save on carbon dioxide, but they release harmful substances such as
dust and carbon monoxide. As a result, the use of solid fuels is regulated in certain
cities and towns. The local chimney cleaning company can be contacted to clarify
these conditions. A fi rewood boiler also requires suffi cient storage area for fi rewood
and a suitable chimney for operation.
If no impediments to the installation exist, the next step is deciding on the dimen-
sions of the fi rewood boiler system. The performance of the boiler should at least
comply with the rated building heat load, in other words the maximum expected
heat power requirement. A boiler has to run constantly when outdoor temperatures
are extremely low. It is best to have a boiler large enough so that it only has to be
fi lled up once a day under average heating conditions.
Boiler Output and Buffer Storage Size for Firewood Boilers
The minimal boiler rated output
Q
B
results from the rated burning period
T
B
of one
stocking of fuel and the rated building heat load
Q
H
:
B
=⋅
6.
QQ
T
.
B
With a building heat load of 10 kW, which corresponds approximately to that of a
standard new single-family house, the rated output of a boiler based on a rated
burning period of 2.5 h is:
64
25
.
.
h
h
Q
B
=
10
kW
⋅
=
25 6
.
kW
The necessary volume
V
S
of buffer storage can be approximated from the boiler
rated output
Q
B
and the rated burning time
T
B
:
1
VQT
=⋅
⋅
13 5
.
.
S
B
B
kWh
As a result, the buffer storage can absorb the total heat volume of a boiler with a
fully stocked burning area. A boiler rated output of 29 kW and a rated burning time
of 2.5 h results in a storage volume of
1
V
S
=
29
kW
⋅
2 5
.
h
⋅
13 5
.
=
979
l.
kWh
12.5.2 Wood Pellet Heating
The general guidelines on fi rewood heating can also be applied to wood pellet
heating. As pellet heating systems normally transfer fuel automatically to the burner,
