What makes stoves so efficient?

[Khriss]

29 minutes ago, openspaceman said:

That's efficiency of converting your labour into heat rather than the efficiency of converting chemical energy of the log into heat which we were discussing.

Indeed . Basically it's how dry yr wood is - water requires a huge calorie conversion, more than cement from my distant O level Chemistry remembering. So it's that that will be yr overall loss in combustion. K

[openspaceman]

2 hours ago, Khriss said:

Indeed . Basically it's how dry yr wood is - water requires a huge calorie conversion, more than cement from my distant O level Chemistry remembering. So it's that that will be yr overall loss in combustion. K

Yes it takes energy to boil the water off before the log will burn but it's not a large proportion of the energy in the log, the  problem is more that it reduces the combustion temperature and the knock on effect of that is  worse pollution given off. Even burning bone dry wood produces steam in the flue as the hydrogen in the wood turns to water.

 

Comparing it with cement is very apples and oranges

[Woodworks]

19 minutes ago, Big J said:

I'm not sure that a stove is really that efficient. 

 

 

 

Not meaning to be rude Jonathan but your choice of a stove is not exactly the hight of efficient design. If I remember right you like the Champion stoves which just appear to be a metal box you chuck logs into. Great value on the face of it but they may well not be getting the hot enough to burn all the gases so plenty more to be had from the wood. Our current 7kWh stove which is not exactly state of the art but it can still manage to heat the whole house. If we used that exclusively I estimate we would need 8 cube per season. 

[Woodworks]

11 minutes ago, Big J said:

I actually rated the Champion Stove Company stove higher than the one that we have at the moment. We have a Woodwarm 20kw double sided stove which would have been over £2k. We've still burned about 14 cube on it so far this winter. And that's with me letting it go out on the milder days. Living room and downstairs is 20-22c and the upstairs is 16-18c. Not excessive, and just the nature of heating these crappy old buildings.

Eeek!  Yes, I am a big fan of Woodwarm stoves. My folks 12 kWh one is probably the best stove I have ever used. If the Champion ones are better than them I will eat my hat (easy to say as I never wear one)

 

Edit. Maybe being double sided they are not as well insulated with glass both sides. Some thin double glazing cant be a match for 25mm or vermiculite board so maybe still not getting hot enough?

 

Edited January 6, 2019 by Woodworks

[openspaceman]

32 minutes ago, Big J said:

but we've not living in a house with modern insulation thus far.

In which case you will burn a similar  amount of energy in oil.

 

As I said earlier energy released has to be accounted for, it either goes up the chimney as hot smoke, remains in ash pan as unburnt fuel or it enters the room and is dissipated through roof, walls, floor, windows and vents.

 

In point of fact if the glass blackens the combustion is incomplete which means chemical energy is lost as carbon monoxide and other PICs and of course a decent gas or oil condensing boiler will have a flue gas temperature of less than 100C whereas not many stoves will be lower than 200C which represents a significant loss even with a clean burn.

 

 

[billpierce]

I actually rated the Champion Stove Company stove higher than the one that we have at the moment. We have a Woodwarm 20kw double sided stove which would have been over £2k. We've still burned about 14 cube on it so far this winter. And that's with me letting it go out on the milder days. Living room and downstairs is 20-22c and the upstairs is 16-18c. Not excessive, and just the nature of heating these crappy old buildings.

Hope you do get sorted with a new build sometime j. Few pals have build nice wooden well insulated houses, was round there new years day and it was still cosy as owt at 2 in the afternoon, no fire been lit since the night before and no other heating. I couldn't believe it. In out draft stone small houses it's the first thing to do every morning!

[billpierce]

The glass blackening was down to it not having an airwash system. It certainly had an effective secondary burn as it always burned cleanly, with little to no smoke emitted from the chimney. 
 
Interesting point on the comparison of heat loss through the flue on oil versus wood burning. Hadn't thought of that before.
 
I look at the stack of firewood at the back of the house and think for the value in it (even just collected, so not having to deliver it myself), I could buy about 6000 litres of kerosene.

I know what you mean, quite an daily effort keeping fires in as well. Cant be doing with central heating myself though, always end up turning radiators off and opening windows when I stay elsewhere. Feel like a house has a good heart with a fire on in the middle of it.

Also always smug in power cuts still being able to cook, bathe and have a warm house.


Just starting the process of doing a lime and hemp Insulating render to the Inside walls of our stone house the now.

[slim reaper]

16 minutes ago, billpierce said:

Just starting the process of doing a lime and hemp Insulating render to the Inside walls of our stone house the now.

Have you got any info on that system, I am in the near future going to render some stone walls but was going to use lime with cork pellets incorporated. 

[difflock]

Well with our latest Morso, (and the previous 2 are still installed in living room and dining room, and 100% functional)

, despite the never yet cleaned glass being slightly hazy(and 2nd winter of use) but not in any way black,

shows absolutely zero "smoke", even immediately after lighting,

and the flue from this stove  is discharging into the same clay liner lined flue the other Morso used for 20 years.(back to back with the living room stove)

Which has honestly never yet been cleaned, and continues to pull like a train. (And when or if it starts to struggle I shall consider cleaning the flue).

Which is to say it must be burning very very efficiently indeed.

marcus

EDIT

Our bedroom is directly above the living room and it is noticeable how much heat is given off by the 18" square chimney breast running up through the ensuite, which was exactly as I had planned/hoped.

The builder wondered why I wanted the chimney breast inside the cavity wall, when he thought it would be tidier outside thus leaving the ensuite uncluttered!

Edited January 6, 2019 by difflock

[slim reaper]

An interesting read ?

http://www.soliftec.com/efficiency.htm