Wood Pellet boilers

[kirismith]

Does anyone have experience of living with a wood pellet boiler for their household heating and hot water? I'm really interested in switching my existing gas system to a wood pellet one and want to know the realities.
Cheers!

[kenneal - lagger]

A friend of mine imports pellets from Argentina.

Find a supplier before you find a stove. In fact if you find a supplier he will probably find you a stove. CAT have used wood pellet heaters and have a help line for this sort of information at

http://www.cat.org.uk/information/info_content.tmpl

and welcome to Powerswitch.

[mikepepler]

And if you find a reliable (local) supply of pellets, the next thing is to make sure your pellet stove will still work when the grid is down - I think most of them need some electricity, though I know some also have a 12V input ready to use...

[snow hope]

My only concern is that there are not many wood pellet suppliers and wood pellets require quite a bit of energy intensive processing to produce...... you can't make them yourself.....

[kenneal - lagger]

I, also, would be concerned about the long term sustainability of supply of wood pellets. The boilers aren't cheap and are relatively complex so maintenance could also be a problem. Personally, I would prefer a log stove. There are boilers available now that can be stacked with a days, or at least several hours, supply and that burn efficiently with a down draft so only the bottom of the heap burns.

I'm trying out various jet fire stoves that will be used for the cooking at the Gathering. I'm going to build one to help heat the water for our new composting loo/shower block but the showers won't, unfortunately, be ready in time for the Gathering although the loos will. We'll all have to smell natural together. The idea would be to uprate the design to do our central heating when our present stove reaches the end of its life.

For Jet fires see http://www.aprovecho.org/

[emordnilap]

An 'eco' shop I was in had one and it seemed clean, safe and efficient. Lots of buts, though.

My worries would be the technology involved - if you're going for pellets because you think they're somehow 'greener' than other fuels, I'd want the technology to last 25 years with minimal maintenance. Can't see that somehow.

Plus, how energy-intensive is pellet making? Again, the machinery used: would it last 25 years?

Thirdly, when the grid's down you're in trouble unless you have some off-grid kit to run it. I suspect 99.9% of owners would not.

Overall, it seems that the 'green-ness' is over-inflated - it's a toy which would appeal to the owners of spotless FUVs.

[Mark]

From the Envirolink NW website:

Biomass Fuel Supply in England’s Northwest

It is often said that one of the barriers preventing the greater use of modern biomass systems is security of fuel supply.

Within the Northwest of England this is simply not the case. It has the best woodchip supply chain in the country developed from an industry which supplies reprocessed woodchip to wood panel manufacturing plants. They deal in over 2 million tonnes annually. The Northwest is now the major biomass fuel supplier to other region’s of the UK. Where problems do occur it is often providing smaller amounts on an irregular basis. Even here, there is a rapidly expanding sector of small and medium sized businesses supplying local markets. No matter where you are in the Northwest you can obtain pellets in small bags on a pallet delivered to your door.

While this leaflet principally concerns the supply of woody biomass, other solid biomass fuels such as olive stone waste, palm oil expeller and other agricultural residuals are used as biomass fuels. These are easily imported in large quantities via the region’s ports.

Link to the leaflet:
http://www.envirolinknorthwest.co.uk/En ... enDocument

It gives useful supplier contacts for those of us in the sunny NW.
Thought it might be useful for people in other areas as well ?

[adam2]

I would avoid pellet fired boilers for the reasons already given re cost complexity and reliance on external suppliers of parts and fuel, and remember that those suppliers are almost certainly grid reliant.

A log burning boiler or stove can generaly also burn coal, generally with the addition of a grate.

The ability to burn coal for a few years could be very valuable indeed, every month in which coal is burnt is another months worth of wood not used, and therefore still available for the future.
If you have healthy trees on your land, burning coal for a year or two would allow the trees to grow a bit more, and actually increase the firewood available in the future.
(any dead, dying, rotten or diseased trees should of course be cut ASAP)

[Mark S]

My company recently tendered for a bio mass woodchip boiler for Kent County Council.Good project but we didnt win it.The KCC are booked to fit 11 biomass boilers over the next 5 years. There is a wood pellet supplier in Sussex we got prices from, i will find his details.

[emordnilap]

I agree with adam2.

I'm doing a brochure for a pellet stove company at the moment. The mechanicals in it would frighten you; it needs a constant source of power; there are so many caveats you'd be a fool to buy one, but that's the small print; the pellets themselves must have a very high embodied energy; the brochure is telling for what it doesn't tell you. I am complicit in furthering this con. There again, I print stuff for gun clubs too. I'm between a rock and a hard place and a brick wall feeling as hypocritical as the rest of you should, though not as much as the governments that give grants for them.

They're gadgets, these pellet stoves, that's all. Like Nigerian scams, there are plenty out there who will fall for it. But that's all they are - stupid, unendurable fads which will endure just that bit too long.

[Joules]

My company recently tendered for a bio mass woodchip boiler for Kent County Council.Good project but we didnt win it.The KCC are booked to fit 11 biomass boilers over the next 5 years. There is a wood pellet supplier in Sussex we got prices from, i will find his details.

I think KCC are hooking-up with someone at Blean Woods for their supply, which should make it reasonably sustainable, and wood chips must surely be a better option than pellets, assuming thay are a by-product of natural forestry processes, rather than created especially for the boilers...?

[snow hope]

I agree with adam2.

I'm doing a brochure for a pellet stove company at the moment. The mechanicals in it would frighten you; it needs a constant source of power; there are so many caveats you'd be a fool to buy one, but that's the small print; the pellets themselves must have a very high embodied energy; the brochure is telling for what it doesn't tell you. I am complicit in furthering this con. There again, I print stuff for gun clubs too. I'm between a rock and a hard place and a brick wall feeling as hypocritical as the rest of you should, though not as much as the governments that give grants for them.

They're gadgets, these pellet stoves, that's all. Like Nigerian scams, there are plenty out there who will fall for it. But that's all they are - stupid, unendurable fads which will endure just that bit too long.

That's a bit harsh emordnilap.

I don't think they are that bad. I have a friend who has one and he has now had it for 2 winters in a 2 year old house with underfloor heating and apart from a few teething problems he generally seems reasonably happy with it. The house is good and warm, but that may be down to the extra thick insulation which I advised him to install and which I am satisfied to say he took on board and had his architect design in (wider cavity walls). He also used a special breeze blocks which are warm to the touch for all inner external walls - expensive but very beneficial.

[JohnB]

Here's a couple of pics of a cutaway Ökofen pellet boiler.

What I haven't got a photo off is the stuff related to the auger feed, and electronics. It's an impressive piece of kit, but is pretty complex, and without mains electricity, it's useless. In a BAU world, when you can call out an engineer if it goes wrong, it's fine, and probably no more complex than any other boiler, although there are very few heating engineers who would know how to fix it. I wouldn't like to rely on one in an uncertain future world though.

[kenneal - lagger]

He also used a special breeze blocks which are warm to the touch for all inner external walls - expensive but very beneficial.

When you have good levels of insulation in a wall the inside leaf will always feel warm, provided of course the energy you put in is equal to or greater than the energy which is being lost.

The best block to use in this situation is a cheapo dense aggregate solid concrete block, the denser the better. This will absorb any excess heat in the room and re-emit it later when the heat in the room drops.

If you use a lightweight, insulating block for your inner skin with a high level of cavity insulation it is, firstly, a waste of money because it will be twice the cost of a dense aggregate block: secondly, the insulation value of a lightweight block is peanuts compared with the insulation value of proper cavity wall insulation (Rockwool) so the block adds a negligible amount to the insulation value of the wall: thirdly, as above the dense block will store heat if the sun shines into the room or you have a crowd of people in while the lightweight block will require the extra heat to be dumped.

If you are aiming for a passive solar house you will need the heat storage of a dense wall block.

With a wall construction of 100 external brick, 120 Rockwool cavity wall batt, 100 dense aggregate concrete block and 13 dense plaster you get a U-value of 0.302: with a lightweight block instead of the concrete, 0.257. With 200 Rockwool the figures are 0.197 to 0.178 and with 300 Rockwool, 0.141 and 0.132.

The 120 Rockwool satisfies the current Building Regs while the 300 Rockwool satisfies Passivhaus standards. At the Passivhaus standard the extra cost and loss of thermal mass does definitely not justify the added .009 to the insulation value. You can argue the standard Building Regs case but I've lived in a lightweight and a heavyweight house and the heavy weight one is by far the most comfortable, especially in hot weather.

A builder will tell you otherwise because he doesn't like handling the heavier block, not from any knowledge of building science. The dense aggregate block will not move with heat change and moisture as the lightweight block will. Lightweight blocks are the reason that new houses are riddled with cracks in the plaster.

I've been using the 100 external brick, 120 Rockwool cavity wall batt, 100 dense aggregate concrete block and 13 dense plaster construction for 30 years now, and the Building Regs have only just caught up. My clients, some of whom were a bit sceptical at first, have been well pleased over the years with the levels of comfort achieved and the money htey have saved. I go for the 300 cavity now, where I can.

[emordnilap]

I agree with adam2.

I'm doing a brochure for a pellet stove company at the moment. The mechanicals in it would frighten you; it needs a constant source of power; there are so many caveats you'd be a fool to buy one, but that's the small print; the pellets themselves must have a very high embodied energy; the brochure is telling for what it doesn't tell you. I am complicit in furthering this con. There again, I print stuff for gun clubs too. I'm between a rock and a hard place and a brick wall feeling as hypocritical as the rest of you should, though not as much as the governments that give grants for them.

They're gadgets, these pellet stoves, that's all. Like Nigerian scams, there are plenty out there who will fall for it. But that's all they are - stupid, unendurable fads which will endure just that bit too long.

That's a bit harsh emordnilap.

I don't think they are that bad. I have a friend who has one and he has now had it for 2 winters in a 2 year old house with underfloor heating and apart from a few teething problems he generally seems reasonably happy with it. The house is good and warm, but that may be down to the extra thick insulation which I advised him to install and which I am satisfied to say he took on board and had his architect design in (wider cavity walls). He also used a special breeze blocks which are warm to the touch for all inner external walls - expensive but very beneficial.

Not harsh considering the people (possibly a majority) who might not follow your excellent advice.

I have a strong bias against over-engineering, on solutions which create more problems than they solve.