Wood Energy: choose pellets, help, criteria and questions

Heating with wood pellets: the question to ask before choosing this method of heating?

1) Are there one or more loose granules providers in my area?

This is a fundamental question: if not, you can stop your thinking here. Without a bulk pellet distributor who can deliver to your home at a reduced cost, it's a bit like buying a car and the first service station is 150 km from your home and you have to take cans with each refueling .

Indeed; It does not seem (economical) logical to us to supply a pellet boiler with bagged pellets: constraint to fill the hopper every day, or even several times a day in the event of extreme cold and much lower price for bagged pellets (more expensive than fuel oil compared to the energy supplied).

Pellets bag

Pellets in bags on pallets

bag granules are for pellet stoves that are often extra heaters although some are quite powerful, but with the disadvantage of a single-point heating unlike the radiators located in all rooms.
That said, it could be interesting to use bags for a boiler if there were intermediate capacity hopper systems (in 4 5 days), easy to load by hand, and considering a pellet prices in bag purchased pallet a ton about 40 bags.

pellet distributor blower bulk truck
pellet distributor blower bulk truck

Beware the distance provider because the cost of transport is an important part of the cost. Indeed, the bulk transport is done by special trucks very expensive, so with significant cost per kilometer for the supplier. It is good, before embarking, to prospect and ask the price per tonne delivered to you to potential suppliers.

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However, some distributors deliver within a radius of 200 km for free (so 400 km round trip for a delivery!), So do your research before giving up your search!

Be careful though with the accessibility of your house: a 20 tonne truck must be able to access it.

2) Where can I store the pellets and in what type of container: what are the pellet storage solutions?

2ieme The fundamental point is the storage of your fuel. Pellets require quite stringent storage conditions, the main criteria are:
- zero or very low humidity (20% max)
- proximity to the boiler
- accessibility to the distribution blower truck

There are several types of storage and several types partially power-related storage type. Let the quick inventory solutions. I will develop the solution silo hard is my case.

a) FlexiTank: this solution makes it possible to build nothing “hard” since the silo is supported by a prefabricated structure.

However, the device, relative to the volume, is expensive, the stored volume is generally low and in fact limited by the height available in the room and the frequent reloading operations. Nevertheless, up to 5 tonnes of storage in a textile silo is possible ...

Pellet silo textile

Pellet silo textile

This solution is therefore limited to use pellets as an extra but we can well imagine or even make such a silo with one (or more?) Big bag sold in some hardware stores.

Disadvantages: small capacity, expensive compared to volume (if not self constructed) must be installed next to the boiler (not necessarily possible) and therefore loss of space in the boiler room.

Advantages: modular, no humidity problem to solve, easy to install

b) Underground tank: excellent solution in terms of bulk in the house since it is zero but the cost of this solution is very high (earthwork and equipment) so that except in new construction it is difficult to envisage.

There are two systems: spherical or cylindrical tank polyester concrete tank with the system Maulwurf (mole) which here 2 schemes:

Silo for spherical pellets Entere
Silo for spherical pellets entérré

Pellet silo textile
Silo for cylindrical pellets

c) In an adjacent room

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You must therefore find in your house (cellar, garage, etc.) or in the annex (lean-to, garden shed, etc.) a place to store the granules. You can also consider building this annex.

An auger or vacuum that will link local and your boiler.

The endless screw consumes less energy but requires storage quite close to the boiler, ie in the adjacent room.

d) A silo in the boiler room.

If the volume of your boiler room allows it (see below for the necessary storage volume) and it is accessible to the truck, the last solution is to build, either even, in panel or hard (parpain), the silo directly next to the boiler. An example will soon be presented on the site.

3) Conclusions: 2 fundamental criteria before launching into the pellets!

To summarize before choosing the pellets must therefore ensure:

a) ofhave a pellet distributor in your area that you book at an attractive price!
b) to have the possibility storing the pellets strictly a volume corresponding to 3,5 times the volume of oil that your house would have consumed. Why 3,5 time? See details here: Pellet storage and computing necessary volume of the silo

Only a thermal balance can accurately determine your exact energy needs.

Read more: Storage of pellets and necessary volume of the silo

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