Wood Burner Back Boiler

[Stubby]

10 hours ago, Alycidon said:

Arada are working on putting catalyst filters into the top of the stove, they have prototypes in the USA with this system. 

Burley are already advertising for sale  stoves with a cat . The  Burley Swithland 8KW is one I have seen .

Edited April 2, 2022 by Stubby

[Alycidon]

Esse introduced Cats in the uk with their new wood burning models late last year,  however their cat is on a slide and has too be slid into place when using.     Am personally unsure if thats the way to go on boiler stoves as fumes from same would tend to clog the cat up I would have thought.

 

Time will tell,

 

A

 

A

[renewablejohn]

It really is a none problem sorted out in Austria two decades ago. What there trying to do is reduce pollution of PM 2.5 and PM 10 particles escaping from the chimney. Its not a stove function but having a compliant stove approved for use in a smokeless zone is a good start. Its actually a flue/chimney function to stop the PM2.5 and PM 10 being emitted from the chimney. Okofen solved this with an electrostatic filter cowl in the top of the chimney so why it has now become a stove problem I have no idea.

 

Electrostatic filter for wood burning stoves - OekoTube

OEKOSOLVE.COM

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An electrostatic filter for all wood burning stoves and wood heaters with a capacity below 50 kW, mounted on top of...

 

Edited April 7, 2022 by renewablejohn

[openspaceman]

44 minutes ago, renewablejohn said:

It really is a none problem sorted out in Austria two decades ago. What there trying to do is reduce pollution of PM 2.5 and PM 10 particles escaping from the chimney. Its not a stove function but having a compliant stove approved for use in a smokeless zone is a good start. Its actually a flue/chimney function to stop the PM2.5 and PM 10 being emitted from the chimney. Okofen solved this with an electrostatic filter cowl in the top of the chimney so why it has now become a stove problem I have no idea.

 

Electrostatic filter for wood burning stoves - OekoTube

OEKOSOLVE.COM

---

An electrostatic filter for all wood burning stoves and wood heaters with a capacity below 50 kW, mounted on top of...

 

Doesn't it cost £2k, need annual servicing and constantly consume 30 Watt though?

 

I'd love one but don't want to be like Rod Hull and getting people in negates the benefit of free heat from wood.

[renewablejohn]

2 minutes ago, openspaceman said:

Doesn't it cost £2k, need annual servicing and constantly consume 30 Watt though?

 

I'd love one but don't want to be like Rod Hull and getting people in negates the benefit of free heat from wood.

But if the alternative is a ban on all wood boiler stoves then you have no free heat from wood as you cannot buy a stove to burn the free wood on.  Which is precisely the stage were at now with this 2022 legislation taking perfectly good stoves out of the market place for wanting a proper chimney installing. As for 30 watt thats only half the electric of an old 60 watt lightbulb and a decade ago that size lightbulb was the norm.  Dont think theres any annual service apart from a normal chimney sweep which you should do anyway.

[openspaceman]

8 minutes ago, renewablejohn said:

Dont think theres any annual service apart from a normal chimney sweep which you should do anyway.

It actually says "easy cleaning by chimney sweep" which isn't quite the same thing.

 

I'm not knocking the idea but it's just too expensive for me.

 

Yes  30W is a small amount but 80% of the time I don't buy electricity and the months when I use a woodburner tend to be when I am short of electricity by about 200W so it becomes significant to me.

[renewablejohn]

30 minutes ago, openspaceman said:

It actually says "easy cleaning by chimney sweep" which isn't quite the same thing.

 

I'm not knocking the idea but it's just too expensive for me.

 

Yes  30W is a small amount but 80% of the time I don't buy electricity and the months when I use a woodburner tend to be when I am short of electricity by about 200W so it becomes significant to me.

You could easily achieve 30w from a teg on your stove in fact go the whole hog and get a 500w teg then if you are short of electric just crank up the wood stove.

[openspaceman]

35 minutes ago, renewablejohn said:

You could easily achieve 30w from a teg on your stove in fact go the whole hog and get a 500w teg then if you are short of electric just crank up the wood stove.

I wish, I have tried to raise discussion on this in another thread; AFAICS at best a TEG converts 4% of the heat flux through it to electricity.  A 5kW (t) woodburner will keep my house warm down to nought C outside, despite having solid walls.  The stove goes out about midnight but the warmth stays in the house till morning when it is re-lit, I have not seen internal temperatures fall to below 13C.

 

4% of 5kW is 200W(e) but all the 3800W of heat has passed through the TEG  and that extra surface area has to be cooled (preferably to below 50C as the maximum temperature a semiconductor designed for the job will stand, cheaper ones designed for cooling tend to be a bit lower.

 

200W for 16 hours is 3.2kWh, not to be sneezed at but probably still a few kWh I need to make up for lack of sun in midwinter.

 

My issue is that I would need a dedicated TEG woodburner and for safety of the semiconductors it would probably need to be water cooled.

 

Your thought are welcome.

[renewablejohn]

5 hours ago, openspaceman said:

I wish, I have tried to raise discussion on this in another thread; AFAICS at best a TEG converts 4% of the heat flux through it to electricity.  A 5kW (t) woodburner will keep my house warm down to nought C outside, despite having solid walls.  The stove goes out about midnight but the warmth stays in the house till morning when it is re-lit, I have not seen internal temperatures fall to below 13C.

 

4% of 5kW is 200W(e) but all the 3800W of heat has passed through the TEG  and that extra surface area has to be cooled (preferably to below 50C as the maximum temperature a semiconductor designed for the job will stand, cheaper ones designed for cooling tend to be a bit lower.

 

200W for 16 hours is 3.2kWh, not to be sneezed at but probably still a few kWh I need to make up for lack of sun in midwinter.

 

My issue is that I would need a dedicated TEG woodburner and for safety of the semiconductors it would probably need to be water cooled.

 

Your thought are welcome.

Thought some tegs are good for 230C .

[openspaceman]

38 minutes ago, renewablejohn said:

Thought some tegs are good for 230C .

TEGS designed for the job, rather than Peltier coolers pinched for things like stope top fans, will work up to 300C because they are joined with a harder solder. Petier devices can be used as TEGS  but tend to be made with softer solder that melts at around 200C.

 

Peltier coolers are available at  nearly an order of magnitude cheaper than proper TEGS.

 

It's a compromise whether one should go with a much larger array of Peltier coolers and arrange for the same heat flux to go through a lower delta T (say 200 through to 40C) or stump up for a smaller number of higher temperature TEGs and a smaller surface area with the heat flux fro 300 down to maybe 70C and heat water for traditional DHW or radiators.

 

I don't understand the science enough really.

 

What I would like to see is a stove manufacturer to design a wood burner incorporating a Stirling genset, like the free piston Microgen one British Gas were trialing. I think this was developed originally by Sunpower to sit at the focus of a parabolic mirror.

 

Harwell actually had a long life Stirling  which was further developed for powering light buoys, which had no sliding surfaces, using a diaphragm instead of a piston, One apparently ran for nearly three years with only re-gassing (helium) required every 6 months, it converted 10% of the heat flux to electricity  so again the stove wouldn't give out heat directly but a traditional wet system could circulate hot water from it. It hummed rather loudly.