I was dubious about your claim that agas are efficient, so I did a little calculation. Assuming that a solid fuel aga requires the same amount of energy whatever the fuel, aga suggest you need 47.5kg of solid fuel to get 220kWh. Unless I've done something wrong, that makes it about 70% efficient. That's pretty impressive for a slow burning cooker!
T
I haven't checked your maths, nor do I know the calorific value of your fuel but coke burning devices always look good because the LHV and HHV are the same. My beef with the aga is that it gives you the heat when it wants to. Now this is fine with solid fuels because they all have this thermal inertia problem but it's an unnecessary restriction when burning inherently "better" fuels like gas or oil.
AJH
According to Wikipedia, coal is about 6.67 kWh/kg. According to Aga you need 47.5kg of fuel a week. My only issue with agas is that when you want to cook, but don't want the heat all day, that's when you start to waste money. If I could afford to run one, I'd probably get one. At the moment I'm after a solid fuel cooker that's a bit more off- and-on-able. It's quite difficult getting information on heat up times, but I reckon the Stanley Errigal should heat up fairly quickly, though I do prefer the look of the Rayburn 300W or Esse woodfired cooker.
T
My guess is thats about right. Ours certainly is a heater first, cooker second as far as I am concerned. Its oil tho. not solid.
You could get even more with flue heat recovery type stuff.
It ought to be possible to calculate efficiency from burner temps (bright orange/yellow?) and flue temps..as I said about 55C at the top of the stove pipe where it enters the flue..
One would hope so ,but as in many things in life there is not always a one size fits all answer My comment is more to do with suddenly extinguishing a hotbed fire than solely a means of controlling a burning flue .What instead of a flue fire there is a sudden blockage. Soot lump breaking free and falling or a poorly maintained chimney having the bricks fall in. When I had to do it was not admittedly in a normal domestic situation but a stove with a steel stove pipe going out through a ships deck. Common years ago very rare now. Had to get the stove out quickly as a load being slung from a crane whacked the outside part so hard it broke the mounting brackets and caused a fracture on the stove joint. It also dislodged a load of soot which blocked the flue so there was no way a draught was going up the tube.Meanwhile the combustion products were filling the accommodation So I have done it,just in different conditions.
G.Harman
I thought agas burned smokeless coal, which will be nearer to coke and hence less volatiles (hydrocarbons), so I was referring to the lack of water in the flue gases, so you could run a very low flue gas temperature, as long as the little water never saturated the flue gas.
Which is why a modern solution is a gas cooker and gas central heating system. If I needed to heat with wood and cook with wood I doubt I'd try to get one device to do the same job and there are some reasonable solutions to cooking with wood, some 2 billion people depend on it.
AJH
The aga ticks over at around 1KW continuous. Thats about right we find for march to June, and September to November. That heats about 200 square meters of house floorage.
June,July and august, its out.
December January and February we chew three times as much oil heating the house conventionally with an oil boiler, as the aga uses all year.
Then the aga is capable of heating just the kitchen, about 30 sq meters.
The key to all this is plenty of thermal mass in the house. It makes more sense with a high occupancy ratio.
which we have also. The house is seldom empty for more than 2 hours.
To be honest, if we had 24x7 wood burners all over he place, ticking over at 1kw per room,. that would be fine as well..if you bother to manage them.
I guess thermostatically controlled dampers might be useful as well.
Bur the great thing about burning fuel where you are - and free fuel at that - is that its very efficient and low collateral energy fuel.
15 minutes with a chainsaw (about 100cc of petrol) and 20 minutes with a hatchet has me a weeks supply of firewood. I'd estimate something like 300kwh worth. In terms of open fires. More if nrnt in a stove.Probably around £15-£20 of oil equivalent. At least. More in a stove. A lot more.
BUT it needs managing..
For oil, the efficiency is worse according to Aga - about 54% efficient. That's the price you pay for the silent operation!
T
A lot depends on what sort of coal it is.
Also according to Wikipedia anthracite has an LHV of 33MJ/kg which gives 9.17kWh/kg.
I doubt Aga owners will be feeding their beast on 'value' brown coal, more like /Finest/ smokeless or anthracite :)))
cheers, Pete.
It cooks turkies very nicely as well :-)
Actually not true.
The heated metal mass in the core of the cooker is very well insulated from the exterior. The heat is therefore not released in substantial quantities at all.
Not at all. With a gas supply, the burner used is a modulating type, the output of which is a few hundred watts when the core is fully up to temperature. The burner output increases when heat is extracted for cooking and other purposes.
No you don't. The whole point of the massive heat store is that the average over the day is very small and there is plenty in reserve for cooking. The few hundred watts of released heat contributes to the space heating as well as being a very effective way of drying slobberadors, Maine coons and chilis from the greenhouse.
The problem with rapid heatup is that there is rapid cooldown as well and it becomes very difficult to regulate temperature.
Have you measured this by oil consumption?
I timed the gas meter with the cooker in the steady state and go a figure of about 700W.
Also "holo-caust". I imagine it means 'to do with burning'.
Yes you do. If you care about needlessly throwing heat out the window, then the 220kWh (270kWh for the 4 oven) it takes to run an aga a week may be of some concern to you. The vast majority of that energy is not used for cooking. Your aga will be giving off at least a kW of "waste" power all the time it is on - which is all the time. If someone had a normal electric cooker, but left a 1kW electric heater on all the time in their kitchen in case a wet dog walked past, you might be forgiven for thinking they were a bit daft!
But for gas it's even worse! According to Aga, a 2 oven uses 425kWh of natural gas a week, to produce 220kWh of heat. I suppose you could take the view that you are wasting so much energy anyway, what's the point in wasting a bit less by fitting a more efficient burner. A 52% efficient burner is pretty shocking considering you can get range cookers every bit as good as an aga with condensing burners nowadays.
I hope to find a cooker that will heat up in an hour or so. That way in milder weather I'll let the fire go out when I don't need it. I imagine I could light it when I got in from work, and when I'm ready to cook, it will be too. It's up to me whether I keep the fire going till morning or all day.
What do you recommend for a second cooker by the way?
T
I suppose inferior fuels are unlikely to be used by aga owners. In which case the solid fuel efficiency is on a par with gas and oil - ie. really bad considering we are in the 21st century.
Some people care about environmental impact, and are prone to measuring this in terms of CO2 produced. I reckon that an Aga, left on all the time, will produce the following emissions:
solid fuel: 6.8 tonnes CO2 oil: 5.2 tonnes CO2 gas: 4.2 tonnes CO2
Isn't the average CO2 per person in the UK about 10 tonnes!
T
No you don't
Two points.
- The figures provided by Aga are conservatively pessimistic. I have measured my gas consumption at the equivalent of around 700W in the fully charged steady state. It does, of course, use more when cooking on the top plates.
- Heat is not thrown out of the window any more than with any other form of heating.
It doesn't matter. It contributes towards space heating.
Incorrect. As I have said, I have measured mine in steady state at around 700W and the heat is not wasted.
If someone has a "normal" electric cooker I think that they are a bit daft. These things are poorly insulated to the point that the room temperature can rise by several degrees. Hardly surprising when 10kW is added to the room heating. Then the window has to be opened to dump the wasted heat.
No it isn't.
Aga don't make cookers with condensing burners.
Leaving that aside, you are not reading and understanding the figures correctly.
The energy efficiency depends on the gas used and the heat released where it is not wanted. The latter *could* consist of heat released through the case and that would be true if the appliance were installed in an outbuilding as opposed to in the kitchen, where a small amount of space heating is wanted.
The other component would be energy released through the flue. Aga have three options. A conventional flue, a convection balanced flue and a powered flue using small diameter pipe and a fan. The latter two of these of course would result in quite a bit of energy loss through the flue, much as it does with a conventional boiler having a similar arrangement.
I have a conventional flue which runs inside the house through two storeys before passing through the loft and eventually exiting on a ridge tile vent. By the time it is entering the roof space, it is barely warm, most of the heat having been given up in the envelope of the house.
Sounds like a lot of trouble.....
Nothing. It isn't necessary.
So, a "few hundred watts" is now 700W! Please make up your mind. I choose to accept aga's official figures which I consider overly optimistic, based on the electricity bills of two neighbours who had electric agas installed this year. If you were being honest with yourself you would quote your gas consumption for the average week, but you are not. Strangely, my central heating consumption is pretty low too when my house is up to temperature.
I'd agree if it were normal behaviour to leave a kW heater on permanently, but it's not, and would be regarded as utterly foolish. If the 425kWh of gas that a 2 oven aga uses a week were put through a modern condensing boiler, that would be equivalent to 2.5kW heater!
Incorrect. Your aga is cooling if it is only consuming 700W at 52% efficiency. Please don't be so foolish as to argue this point, just give it a moments thought instead. If you claim that an aga can be kept at temperature by 4 lightbulbs, I will just laugh. I thought it was "a few hundred watts" anyway.
This is so funny, hoist by your own petard!
Sandyford do, so do Rayburn.
You are the one with the comprehension problems. An aga needs 220kWh of heat a week according to aga. A gas aga requires 425kWh of gas a week according to aga. The inefficiency has nothing to do with heat being released where it's not wanted. It seems agas are just over 50% efficient whatever the fuel (apart from electricity).
You are conveniently ignoring the fact that the burner is of low efficiency.
Here's a recent article you might find enlightening:
I didn't say it was necessary - it's just sensible.
I did. 700W is "a few hundred". It's not a "few thousand" is it? I have always consistently said that I have measured an inout rate of
700W in the steady state.Please yourself. I know what I measured and Aga's figures for gas consumption are pessimistic.
The only way to do that would be to have a separate meter just for the Aga, since the main CH boiler is also gas. Taking a whole house measurement would be pointless anyway because gas consumption depends on the size of the house, the insulation and the pattern of hot water use. It is reasonable to take the Aga consumption is isolation with the boiler turned off because the heat input is practically constant and very much less than the requirement for the house in total.
Likewise.
During the heating season, if the heater were gas and contributing virtually all of its heat into the house, it would be entirely reasonable.
I measured approximately 30% of that based on the gas input rate.
You're getting confused.
I have.
I haven't said that, and neither have I mentioned any efficiency figures, let alone 52%. The gas input rate, measured, is 700W in steady state.
You are arguing from sets of figures that you have pulled from goodness knows where.
700W is a few hundred watts.
Not at all if you read what I wrote rather than what you think I wrote. This was one of the reasons for disposing of a "conventional" cooker and hob.
On the contrary, you are.
Do you own an Aga? No.
Have you actually measured one? No.
I already told you that the figures are conservative. They also don't specify the pattern of use.
Of course it does.
That would depend on how you measure efficiency.
That depends on what is measured and where. If you measure in terms of energy in and what comes out of the flue immediately at the appliance, it is one thing. However, if the flue runs through the envelope of the house and gives up further heat there, where it is wanted, then that certainly contributes towards overall system efficiency.
I am certainly not going to fuss over the difference of a few hundred watts of heat in the cooker, when the boiler is using at least an order of magnitiude more heating the rest of the house and the hot water. It is also why I won't have anything to do with low energy light bulbs and all the other silly green nonsense.
Guardian. Nothing written therein can be relied upon as trustworthy.
I am not in the least bit interested in articles by people who choose to pontificate about the carbon emissions that others make.
As soon as the guy starts to make comments like "society urgently moves to a carbon-negative economy" and makes comparisons with solar electric panel installations then it is safe to say that he is testiculating (i.e. waving arms around while talking bollocks).
If I had bothered to implement an additional cooker, it would hardly be used and would frankly gather dust and use space. Even the microwave is seldom used.
Welsh dry steam coal mostly, It burns a little easier than anthracite. Or coke or pre-made coaldust pellets.
Low bitumen content was the key. And low residual rock content to avoid too much slag.
I'd hate to go back to coal fired anything frankly. Open fires maybe.
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