Talk:Masonry heater
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I have added the following exchange - can any one add some emissions data for these stoves, and any other useful comcments?
Thanks
Engineman.Engineman (talk) 05:53, 18 May 2008 (UTC)
Bill / Dave O
yes I think it is " horses for courses" , clearly some off grid houses can be upgraded to Dave O's German standards , but very many won't be for the kinds or reasons you state - and these could easily have the Swedish stoves, I think - much better than pellet boilers, or metal stoves.
I agree with you about the pellet boilers in low demand houses - to run at low output they must in effect smoulder, which is inefficient and highly polluting. but in the right application - eg heating the RAF Wroughton hangers, quite acceptable I would have thought.
The great thing, on the face of it, about the Swedish stoves, is apparently that they burn all the fuel at high temperature, (much higher than you can get in a metal stove) and then condense out all the tars etc due to the labyrinth of cold brick they have to pass through on the way out. this accounts for their high efficiency and on the face of it, it seems obvious they must approach 90% simply because the flue gases leaving must necessarily be quite cold. (where else can the heat go but into the house)
I assume the tar condenses, and trickles down into the combustion zone, as the fire cools and is all burnt off next time round as more fuel is put in next day.
Any way, can someone come up with some emissions data?
This is of course a side show - and neither here nor there in the scheme of energy disaster heading our way, but quite interesting as to why we don;t have them over here.
http://en.wikipedia.org/wiki/Masonry_heater
According to Wikipedia, the Swedish version, they were designed on the orders of the Swedish King in the 18C when they were worried about their forests been burnt down. (its déjà vu all over again)
I don't think Dave O ' s comparison with CEGB chimneys is valid - we will be talking of tiny amounts of flue gas by comparison with power station emissions and immensely lower SO2 levels.
The other point to be drawn from this, in my humble opinion, is that comfortable storage heaters can be made, and whilst I agree that hopeless British storage heaters are uncomfortable, I don't see why they should not be made so, along the Swedish stove lines, and used for storing surplus wind energy, another point which David O has not addressed yet.
Dave A
David Andrews
From: claverton@yahoogroups.co.uk [1]Subject: [claverton] Re: Those pesky Swedish stoves again.
Dear All
1. Yes, these would be useless for the mass of useless British houses, unless upgraded.
2. While radical upgrades as proposed by David are practicable in some circumstances, one often runs into constraints - space, planning, cost, technical risk - and then a combination of a practical upgrade plus a simple, efficient heat source can make sense.
3. But where it also makes sense to burn wood - e.g. with the right house in a rural location off the gas grid and with a local timber supply - then these might fill an important slot for a relatively low-tech, low-maintenance, high-efficiency, reduced-pollution alternative to a normal woodstove. I am not very happy about the capital cost, maintenance requirements, and supply chain requirements of pellet boilers for these purposes.
We need more efficiency and pollution data though.
Bill
On 17 May 2008, at 09:43, David wrote:
Insulate most of these dwellings. Visit Germany; see it happening right now. See past Claverton posting re. a Passivhaus retrofit of a German farmhouse and a reduction in oil consumption (before considering a solar system) from (I seem to recall) 5000 to 500 litres/yr.
Not invented in UK doesn't mean impossible. The house I'm renting while I build my own could easily be externally-insulated, encouraged by (1) bulk contracts (like those used when connecting the UK to N Sea gas) (2) grant aid (as available abroad).
A typical Swedish or Finnish detached house has a peak heat demand of 15-25 kW @ -30 degC. A new UK detached house meeting current Swiss Bldg Regs or the AECB Silver Standard has a peak demand of 3 kW for space heat and say 1 kW for hot water, totalling 4 kW @ -4 degC. A wood fire in such dwellings is near-uncontrollable.
I don't believe 90% seasonal efficiency; show me the evidence. Not even pellet boilers achieve 90% at peak load. Empirically several country people I know who've replaced wood heating in the past by oil or LPG have roughly halved their fuel consumption, suggesting the wood system had nearer to 40% seasonal efficiency. Most wood-burning stoves achieve 60-70% according to SAP-2005 (used to comply with UK Bldg Regs.)
17% of dwellings are off the gas grid. (A few of them might be connected at this late stage or connected to DH if it became available, but the majority are 3-5+ km from the nearest gas main.) Some areas with mains gas (possibly parts of Claverton near Wessex Water, parts of Malvern, no doubt many more) might be too dispersed to connect to DH which is more costly than a gas main. So on checking further the areas concerned might cover nearer to 20% of housing and 10% of non-domestic buildings.
D.
Original Message -----
From: Dave EU Andrews
Subject: RE: Those pesky Swedish stoves again.
Bill and Dave,5
I don’t think these would be appropriate for the mass of useless British houses, but what we are talking about here is surely the quite low 5 -10 % of UK housing ""in the country"" and off the gas grid.
I don’t think David O has given a satisfactory answer - these are houses already built and are not going to slap on extra insulation at this late stage.
Rather than continue to shove wood into a hopeless, inefficient open fire or smouldering stove, the Swedish designs seem to me an ideal solution for the country dweller.
They were not apparently designed by the Russians if you look it up on Wikipedia and translate it
Dave O these things are 90% efficient and so far you have not given any emissions data.
It is evident that they are quite comfortable since 90% of Finnish dwellings have them so I don't think we are going in circles, you have just not answered my questions, (I think)
Kind regards
David Andrews
Claverton Energy Group
From: Bill Sent: 17 May 2008 16:45
Subject: Re: Those pesky Swedish stoves again.
Dear All
My understanding is that these stoves are most effective in houses which have a tendency to be cold and benefit from a steady source of heat, and where the gains in combustion efficiency more than counterbalance any wastage, e.g. from unnecessary heating overnight. This is certainly what they were developed for.
They can also make some sense in new, well-insulated houses in colder climates (e.g. Sweden and Finland) in which a gentle, continuous source of heat is appropriate. These can do this effectively with short bursts of firing, as already described. So, for example, you can fire them up for an hour in the evening and that carries you through the next 24 hours.
Problems begin to arise:
1. Where you need faster warm-up response. These are partly resolved by putting fans in the units.
2. Where heat carry-over leads to waste (e.g. overnight in poorly-insulated British buildings which do not hold their heat).
3. Where heat carry-over leads to overheating and, window-opening for example, e.g. in lightweight buildings with high daytime internal or solar gains.
I suspect there is also a cultural dimension. For example, they would work best in situations where one was happy live with a fluctuating temperature.
Sue Roaf put one in in her Oxford Ecohouse, but very much as a standby unit I think, as there was also had gas-fired heating. I'll ask what her experience is of it.
With good wishes
Bill
______
On 17 May 2008, at 03:32, David wrote:
Uncontrollable. Developed for almost uninsulated houses in Russian winters, not insulated houses in western Europe. Put yout thermal mass in the building not in the heat emitters.
Dirty (unless you think particulates and PAHs an order of magnitude more than from an oil boiler are clean).
Waste of a valuable chemical fuel. Insulate houses, don't waste solid biofuels on them which could better supply transport sector, chemical feedstocks, gas for glass-making, CHP plant, etc etc.
Sweden has a tiny fraction of the population density of the UK, so can presumably support more air pollution per dwelling without exceding a certain threshold.
As it is, particulates shorten the life of EU citizens by an average 8 months according to medical research. I can't understand why so many people are prepared to risk public health for a gain which is so illusory and could be gained by retrofit insulation, solar and backed up by fluid biofuels.
Read past Claverton postings as this goes round in continuous circles.
D.
Original Message -----
From: Dave EU Andrews
Subject: Those pesky Swedish stoves again.
Dave () - what is your objection to this kind of thing for use in the country areas, and supplemental heating by surplus wind farm electric?
There Swedish so by definition they must be good.
Kind Regards
Dave A
http://www.buildingforafuture.co.uk/summer03/22-43.pdf page 36.
TThe Scandinavian kakelugn is normally constructed in its
simplest form, that is as a space heater designed to perform
that one function very efficiently. Tests in Swedish government
research laboratories have rated the heating efficiency of
these stoves at over 90% and their environmental efficiency
at over 80%. They have been granted exemption from the
Clean Air Act in this country due to their extraordinary ability
to consume practically all of the pollutant normally produced
by burning wood and this without the use of a catalytic conversion
system. Their impressive heating efficiency is a product of
the same factors that allow the stove to consume the pollutants;
the high temperature in the combustion chamber, the
channelling of the hot smoke and gases around the interior of
the stove instead of straight up the chimney, the use of stone
with a high heat-retention value and slow release rate and the
employment of a damper to keep the heat in once the fire has
gone out.
The burning cycle differs from conventional stoves in that
the fire is alight for relatively short periods of time, generally
a couple of hours. During this period, the wood is being
consumed at maximum efficiency with normal combustion
temperatures of around 1,000∞C. The fire is then allowed to
go out and the damper closed (the Scandinavians close theirs
completely, but in this country where we are less familiar with the
concept we are required to construct a damper that will only
close to 80/90% to allow for the escape of any residual fumes).
So the fire is either roaring away like a furnace or it’s out, thus
avoiding the smouldering cycle that is inherent in the design of
many conventional woodburners, which is both inefficient and
produces so much pollutant. The heat stored in the stone and
tile mass is then released in the form of long-wave radiant heat
until the stove reaches ambient temperature or until it is re-fired.
The length of time that the stove retains useful heat depends on
its size (mass) and the ambient temperature, but a stove that
was alight in the evening will still be warm the following morning
and some large European stoves are capable of retaining heat
for 30 hours; it goes without saying that more heat gain will be
felt in a well insulated building. Stoves built in houses with a
lot of brick and stone construction also heat the fabric of the
building itself which will contribute to the heat storage capacity,
but well-insulated houses of wooden construction have also
been found to have benefited from the inclusion of a high-mass
stove in the heating plan. This stove would normally be built on
its own foundation and travel right up through the house very
much as a conventional chimneybreast would. This produces
a core of comfortable heat as near to the centre of the house
as feasible with the possible inclusion of hotplates, ovens and a
warm seat upstairs in a bedroom or bathroom. As a general rule
of thumb a ceramic stove of average dimensions (about 2m
high and 80cm in diameter) will heat about 150m3, in return for
a daily burn of about 15kg of wood. This is such an effective use
of biomass that over 90% of new Finnish homes have a ceramic
stove of some sort.
