Control of Wood Burning Stoves?

[ericmark]

Particulate pollution it would seems means the pot bellied stove is now a thing of the past, and wood burning heating systems now have a number of methods to ensure a complete, controlled burn to the wood. With sophisticated baffles and air supply control, catalytic converters, electrostatic, or high pressure water these pollutants are removed.

The main change seems to be a double burn where the air in the bottom of the stove controls how quickly the wood burns but a secondary air supply higher in the fire box ensures the burn is full with no tar or other waste products going up the flue and also the flue temperature is carefully controlled.

Reading it would seem when wood is added to a fire there are two stages the first where the stove is allowed to get very hot reducing the logs into charcoal the second with the stove running cooler while the charcoal is burnt.

Theory is great but in practice one does not sit monitoring the fire all day one just checks it from time to time. As the wood reaches the charcoal stage of the burn the air supply into the bottom of the stove needs closing and clearly this gives a need for automatic control. Be this timer or some sensor is really beyond my ken which is the reason for the post. Catalytic converters, electrostatic or high pressure water all need electric power and it would seem the sophisticated baffles and air supply control would also need some electric supply to shut down the air supply once the logs have become charcoal. Yet I read the adverts for wood stoves and there is no reference to electrical requirements. OK could be battery, but to ensure economically use of the wood I would expect some automation needing more than supplied by batteries. Also this two stage burn would it would seem also mean a two stage heat output.

So some method of storing the heat during high output and then supplying it to the home during low output would also be required. This is of course done with solar panels with storage systems like the megaflow but it would also need some indication as to if low or high in energy so the user knows to add more or less fuel. Yet at the same time one would not really want the burner to go out. Look as I can I can’t see how the amount of heat stored is used to regulate the burn rate of the stove. Could anyone point me to the details on how the integrated system is controlled please? Easy to understand each part but not how it all comes together as a whole.

 

[Inky Pete]

Link

 

[Corgigrouch]

Eric, I have never fitted a clean burning stove that has needed an electrical supply... you have an upper air supply lever and a lower air supply lever you adjust them with the big mitten that is supplied with the stove and it burns... They are delightfully simple, no PCB required.....Though some may have a thermostat operated by a bi-metallic arm.

Want to store the heat? simple, clad the stove with big lumps of iron or stone... Have a look at Dan Skan stoves for further details

Catalytic converter? on a solid fuel stove? Never seen one..

 

[Norcon]

Pot bellied stoves a thing off the past? I don't think so.

I think you're referring too gasifiers. Not many wbs's made that way. Certainly not MiE.
But here's an example thats over 90% efficient.....


http://www.thermotec.co.uk/uploads/Walltherm info sheet.PDF

http://www.wallnoefer.it/cgi/sdcgi.exe

It has a output to room of up to around 5 kW and 10 kW to water which is pumped to a large 750+ litre thermal store / accumulator (which can also be heated by solar etc) - to be used for DHW & CH as and when required. It's supplied with a loading/charging unit and has all the necessary safety controls to allow it to be used on a sealed system, if required.

Canada incidently has three million homes with wood stoves fitted!
But then they do have a lot off wood.

 

[Agile]

I removed a very sophisticated wood burning stove for my friend in France.

It had motor driven dampers etc. so that it would control the hot water output. It was very effective but gave so little heat out to the room.

So I fitted a smaller unit with no controls at all but it certainly gave out a lot more heat directly to the room than the servo controlled one which I removed!

 

[ericmark]

Thank you for useful comments and links. My friend has a simple wood stove and is convinced they are bad for the environment some of this is due to the removal of wood which would normally recycle in the woodland to burn instead and I have to agree that will damage the woodland.

However there are clearly also plus points and since he is intent on writing a report I thought it was best to look into the plus points to stop him putting his foot in it.

On finding this site it was clear there are some very clever wood burners although this one is a prototype.

So I started to hunt further this site referred to an "Airwash system" which got me hunting further where I found a host of USA sites which talked about the particulate pollution problem.

Their government gives "Wood burning tips"

Burn only wood. No garbage, plastics, rubber, paint or oil, briquettes, paper, etc. Burning these items releases harmful chemicals into the air.
Burn Wise Program from EPA: Emphasizes the importance of burning the right wood.
Build small, hot fires instead of large, smouldering ones.
Don't "bed the fire down" for the night. Holding a fire overnight is a fire hazard and can create serious indoor and outdoor air pollution problems.
Open your damper if the smoke is dark. Dark smoke indicates more pollution is being produced and fuel is being wasted.
Keep your stove clean and well-maintained. Follow manufacturer guidelines; replace catalytic stove filters every 1-4 years. Have your chimney checked and cleaned at least once a year.

And it would seem there is a lobby to ban wood burning stoves in some areas of the USA and I was reminded of when I was a lad with coal burning everywhere and the smog which resulted in smokeless zones being declared.

He is looking at wood burners from the view point of the woodland owner and clearly to plant trees which take around 20 years before you can get any return and more like 150 years then to plant to supply wood burners only then to find the government bans them would upset the apple cart.

All the people I know with wood stoves are continually on the lookout for sources of free and cheap fuel. Broken pallets, and builders rubbish seem to be common sources all which according to guide lines are to be avoided because of the nasty fumes they produce.

Often on talking to them I find the installation is a real DIY nightmare with things like plastic header tanks made from thermal plastics unable to withstand boiling water clearly not suitable for solid fuel burners which can easy over heat the water.

This also means likely little attention has been paid to the flue and the tar around the outlets clearly confirms this. Reading all the sites it would seem where scrubbers are used the flue gases are clean so clearly no scrubbers fitted.

Talking to my Dad now 88 he tells me all about the problems in his younger days in maintaining solid fuel fires, and tells me how where he worked solid fuel was the last resort because of the maintenance problems. Blast Furness gas was first to select then coal oven gas, then oil with solid fuel last on list. And they only used solid fuel at night when no one could see the smoke as the scrubbers did not work very well. Only a small power station at 12.5MW but multi-fuel so interesting.

It would seem he got his job as superintendent at the power station because of his naval experience where smoke was a real problem as the foe could see you. Adjusting the various dampers it was it seems important not as the song said.

So I am slowly learning and gathering information to present to the woodland owner.

 

[ericmark]

http://www.thermotec.co.uk/uploads/Walltherm info sheet.PDF

http://www.wallnoefer.it/cgi/sdcgi.exe

As a P.S. interesting to see the German site you linked to used the Willis system from Northern Ireland.