7.1 Fuel storage in on-site pellet store
Sizing the pellet storage room
The storage room should ideally be rectangular and large enough to
accommodate a year's supply of fuel. This reduces the number of
deliveries. The size of the storage room depends on heat load of the
building, which in turn depends on the building's heat demand. How-
ever, the floor area of the pellet storage room should not be less
than 2 x 3 m.
To calculate the annual fuel demand in pellets in m
3
, as defined by
the heat load of a building, use the following
rule of thumb
accord-
ing to the ÖNORM M 7137.
Calculating the annual fuel demand in pellets, as defined by the
heat load of a building:
Annual fuel demand [m
3
] = heat load of a building [kW] x factor 0.6
[m
3
/kW]
Storage rooms without sloping floor
■ The volume for the annual fuel demand [m
3
] corresponds to the
volume of the storage room [m
3
].
■ Volume of a storage room without sloping floor [m
3
] = volume for
annual fuel demand[m
3
]
Storage rooms with sloping floor
■ Empty space must also be taken into account to ensure that the
volume for the annual fuel demand [m
3
] is covered. About 1/3 of
the volume is lost due to the sloping floor.
■ Volume of a storage room with sloping floor [m
3
] = volume for
annual fuel demand[m
3
] x factor 1.5
Converting storage room volume into the amount of pellets:
Amount of pellets [t] = storage room volume [m
3
] x 0.65 t/m
3
Example:
Pellet storage room with sloping floor
Heat load of building (e.g. detached house) 50 kW
Volume for annual heat demand [m
3
] = 50 kW x 0.6 m
3
/kW
= 30 m
3
Amount of pellets [t] = 30 m
3
x 0.65 t/m
3
= 19.5 t
Volume of a storage room with sloping floor [m
3
] = 30 m
3
x 1.5 =
45 m
3
Room height: 2.3 m, floor area of the storage room = 45 m
3
÷ 2.3 m
= approx. 20 m
2
A minimum room size of 4 x 5 m is adequate for storing a year's sup-
ply of fuel.
Stored amount of energy = 19,500 kg x 5 kWh/kg = 97,500 kWh
A
B
C
D
E
F
G
200
500
45°
A
Fill connector
B
Return air connector
C
Air space
D
Sloping floor
E
Empty space
F
Viessmann discharge system
G
Available volume = ⅔ of the room
Fuel storage
70
Viesmann
VITOFLEX 300-UF
7
5682428
