eta 13180 LP-D, Installation Manual

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Pellet store Calculating pellet supply and store size
73
13.3 Calculating pellet supply and
store size
Heating value and bulk weight of pellets
The energy density of 2 kg of pellets corresponds
to that of 1 litre of extra-light heating oil.
Calculating the pellet supply
Rule of thumb for determining the pellet supply in tons:
divide the heating load of the building by 3.
For the pellet supply in cubic metres (m³), divide the
heating load by 2.
Example for the pellet supply for a single-family house
with average insulation and 12 kW heating load:
•
12 kW / 3 -> 4 tons of pellets per year
• 12 kW / 2 -> 6 m³ of pellets per year
The pellet supply can also be calculated from the
current fuel consumption using the appropriate
conversion factors:
Required pellet store size
The required store size is based on the heating load.
Use the rule of thumb "heat load divided by 2" to find
the minimum required store volume in m³.
Example for the pellet supply for a single-family house
with average insulation and 12 kW heating load:
•
12 kW / 2 -> 6 m³ of pellets per year
To be prepared for colder winters, the store
should hold around 20% more than a year's
supply. For this example, that means a store volume of
7.2 m³ is needed.
Using this volume, we can determine the necessary
room dimensions and the length of the conveyor
screw.
The length of the conveyor screw needed for the store
volume can be determined using
Tab. 13-1: "Useful
cross section of store in m²" . That length also
determines the minimum length of the pellet store.
Example: Room width 2.0 m and height 2.4 m:
•
The table yields a usable cross section of 2.9 m².
The volume of pellets to be stored in the example
above is 7.2 m³:
=> 7.2 m³ / 2.9 m² = 2.5 m length
A discharge screw with a length of 2,5 m is
required.
Example: Room width 2.8 m and height 2.4 m:
•
The table yields a usable cross section of 3.59 m².
The volume of pellets to be stored in the example
above is 7.2 m³:
=> 7.2 m³ / 3.59 m² = 2.0 m length
A discharge screw with a length of 2,0 m is
required.
The conveyor screw should preferably be
oriented along the room's long axis. The narrower
the room, the less space is lost under the 40° tilted
floor. The unobstructed room length of the pellet store
should be at least 100 mm longer than that of the
conveyor screw.
The conveyor screw can be as much as 0.6 m shorter
than the room without any problems. If the store is also
faced with tilted panels at the end, the conveyor screw
can even be up to 1.5 m shorter. For a maximum screw
length of 5 m, the maximum accessible room length is
6.0 m.
Determining usable storage volume
Due to the 40° tilted floor required in the store, room
widths greater than 3 m offer little or no additional
useful volume for rooms of normal height (also applies
for conveyors with suction heads).
Heating value 4.9 kWh/kg
Bulk weight 650 kg/m³
Fuel consumption Factor Pellet supply
1960 l heating oil x 2.04 4000 kg
2060 m³ natural gas x 1.94 4000 kg
2960 l LPG x 1.35 4000 kg
1560 kg LPG x 2.56 4000 kg
2660 kg coke x 1.50 4000 kg
5700 kWh electricity from
a geothermal energy heat
pump with COP 3.4 x 0.70 4000 kg
9500 kWh electricity from
a ground source heat
pump with COP 2.1 x 0.42 4000 kg