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Eco fan for top of woodburning stove

Last post Sun, Dec 1 2013 23:58 by Peter Wells. 28 replies.
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  • Mon, Nov 11 2013 23:33

    • Peter Wells
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    Eco fan for top of woodburning stove

    A steel framed fan is placed on top of a wood burning stove and according to a Canadian University study, saves up to 18% of fuel. It does it by better distributing the heat around a room thus leading the owner to regulate the 'burn' better. 

    A blurb from Google reads. "The Ecofan generates its own electricity through the difference in temperature. The base must make contact with a heat source of at least 85°C (150°F) and the top of the fan must remain cool. The Ecofan needs to draw cooler air from behind in order to operate. The actual rotation of the blade as well as the cooler air and the heat source are the essential elements needed for the Ecofan to operate."

    I bought one a year ago for my daughter's wood burning stove and decided the other day to buy one for my own stove.

    Has anyone else tried them?

  • Tue, Nov 12 2013 6:47 In reply to

    • mursal
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    Re: Eco fan for top of woodburning stove

     

    Peter Wells:
    The Ecofan generates its own electricity through the difference in temperature

    No Peter not yet, but really interested if it generates electricity for the fan motor? 

    Expensive? 

  • Tue, Nov 12 2013 13:53 In reply to

    • Peter Wells
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    Re: Eco fan for top of woodburning stove

     

     

    mursal:
    really interested if it generates electricity for the fan motor?

     Mursal.

    The quotation below is the nearest I have got to an explanation as to how the Eco Fan works without batteries or connection to the mains. It is silent in operation and the blades spin so fast you cannot see the movement. It shifts a lot of air (without you feeling it) to the back of the room and so the Inglenook is not a 'sink' for the heat from the wood burner.

    "As you read this page, your computer is using a Peltier chip to cool its central processor unit. In this scenario, electricity is put into the chip to create a hot side & a cool side, and the cool side is attached to the CPU. An EcoFan does the reverse - using a hot & cool side of a Peltier chip to generate electricity & run the fan motor.

    The Eco fan  features an attractive black brushed aluminum finish, with lightweight brass, nickel blades or black painted blades.". Made in Canada!  "

    I have an all black one as I didn't want a silver or gold coloured disc whizzing around on top of the burner. I paid £95 inclusive of everything and hope to save that in the effort I need to put in to prepare the wood, including chainsaw, splitting, tractor time etc.

  • Wed, Nov 13 2013 7:03 In reply to

    • mursal
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    Re: Eco fan for top of woodburning stove

     Thanks Peter very interesting, I haven't come across this system before.

    Sounds like free energy (to run the motor), but I must be missing something

  • Wed, Nov 13 2013 8:35 In reply to

    • Jacobus
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    Re: Eco fan for top of woodburning stove

    mursal:
    Sounds like free energy (to run the motor), but I must be missing something

    It's a thermopile (several thermocouples wired together).  If you google 'thermopile' you won't get much but 'thermoelectric generator' will give you more.
  • Wed, Nov 13 2013 9:02 In reply to

    • henarar
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    Re: Eco fan for top of woodburning stove

    mursal:

     Thanks Peter very interesting, I haven't come across this system before.

    Sounds like free energy (to run the motor), but I must be missing something

    You don't get free energy it must come for somewhere it must be using some of the heat from the wood burner to run the fan therefore the wood burner will give out less heat

     

  • Wed, Nov 13 2013 9:29 In reply to

    • 2658336
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    Re: Eco fan for top of woodburning stove

    henarar:

    mursal:

     Thanks Peter very interesting, I haven't come across this system before.

    Sounds like free energy (to run the motor), but I must be missing something

    You don't get free energy it must come for somewhere it must be using some of the heat from the wood burner to run the fan therefore the wood burner will give out less heat

     

     

    Absolutely right, or almost.   The thermo-electric generator does absorb energy and turn it into electricity to turn the fan, but the electric energy all gets dissipated as heat again, so there's no nett loss.  The whole point of the fan is to blow air across the stove, and therefore put more heat into the room for a given stove skin temperature, which means you get a bit more useful energy per unit fuel consumed.

    The word "thermopile" is usually reserved for arrays of metal thermocouples, most likely chromel-alumel types which will give about 10 millivolts with the cold side at 0C and the hot side at 50C.  You used to be able to buy cylindrical mounted stacks of these things in the US, designed for running a small electric motor to power a boat for fishing.  I think they were mostly gas fired, but I suppose in principle you could have used a small fire of sticks or something.  You'd certainly need a thousand or more separate thermocouples.

    The things on the ECO fan are slightly different in that they employ a semiconductor junction made of something horrible (to a semiconductor engineer such as myself)  like bismuth telluride rather than two metals.  The details of the physics are just a little different, but you get something over 100 millivolts for a 50C drop, so a lot less junctions are needed.  Identical devices are used in cold boxes for the car and suchlike.

    Are they worth while?  Quite possibly for a wood burning stove without water jacket, although if the latter does apply and radiators are run, I doubt it.

    Just in case anyone considered it, NEVER eat bismuth telluride: it'll give you the most dreadful indigestion, possibly fatal.

     

  • Wed, Nov 13 2013 12:52 In reply to

    • Peter Wells
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    Re: Eco fan for top of woodburning stove

    2658336:
    Are they worth while?  Quite possibly for a wood burning stove without water jacket, although if the latter does apply and radiators are run, I doubt it.

    My wood burner is in an ingle nook and has no connections to water or radiators. Under those conditions I am glad you think the Fan useful.

    I think the point of henarar  "You don't get free energy it must come for somewhere it must be using some of the heat from the wood burner to run the fan therefore the wood burner will give out less heat" is almost correct however, as 265.........  implies, under the conditions specified, the wood burner doesn't produce less heat, rather the heat produced is dissipated more effectively to where it is needed.  'Interestingly. the fan must be sited at the rear of the burner so that the relatively cooler air coming up from the back of the burner can be used as a contrast to the temperature of the base of the fan which is sitting on top of the burner itself. A difference of around c 150c.

     

  • Wed, Nov 13 2013 13:43 In reply to

    • mursal
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    Re: Eco fan for top of woodburning stove

    Thanks everyone for the information

    Note to self:

    Well that's that knocked on the head ........... Huh?

  • Wed, Nov 13 2013 15:42 In reply to

    • Peter Wells
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    Re: Eco fan for top of woodburning stove

    mursal:
    Well that's that knocked on the head ........... Huh? 

    Why. What where you thinking?

     

  • Wed, Nov 13 2013 18:29 In reply to

    • mursal
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    Re: Eco fan for top of woodburning stove

     I wasn't thinking Peter, got carried away with the thought of not having to plug the fan in

  • Thu, Nov 14 2013 12:26 In reply to

    Re: Eco fan for top of woodburning stove

    We've got a black one sitting on top of our woodburner,...bought in from the same shop with purchased the woodburner from.

     It does indeed do a good job of sending the warm air out into the room and Yes, they are extremely quiet and worth it in my humble opinion.  Does the job well i'd say.

  • Mon, Nov 18 2013 16:51 In reply to

    Re: Eco fan for top of woodburning stove

    I'm sure it works but not sure how it would save fuel. I find our stove gives out most heat when it's got really dry wood in it and it's shut right down with minimal ventilation. Then it burns for hours and really pumps it out. The fan would be acting to more evenly distribute the heat horizontally I guess. But I can't see a way I can burn more efficiently to save fuel. Opening up the vents just increases burn speed and pulls more air into the stove and up the chimney. It's a good idea but practically I don't think it's going to save you on logs. It will just spread the heat your logs are producing more evenly and effectively.
  • Tue, Nov 19 2013 9:47 In reply to

    • Peter Wells
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    Re: Eco fan for top of woodburning stove

    Back In Black:
    But I can't see a way I can burn more efficiently to save fuel

    I agree with you and I'm sure it doesn't per see. As you say it does distribute the heat horizontally and I have found that with an Ingle Nook it shifts some of the heat from the Nook to the room. I have also found that it is during the evening hours, say seven to eleven, that you want the heat in the room and not in the nook or fireplace. The fan does that.

    As for saving logs. During those 'core warming' hours there is no need to raise the burn level of the fire as the fan is bringing the warm air forward.

    I believe the Canadian study involved a typical living room being built inside another room. The heat required to keep that inner room at the required temperature was then measured with and without the fan. Apparently, the fanless fire required some 14-18% more logs (calorific value)  to maintain the required temperature.

    PS. As one gets older one is looking for devices that will save not just money, but labour. Even if the saving in log felling, cutting, splitting, handling is 10%. I'll take it.  

     

  • Tue, Nov 19 2013 15:23 In reply to

    • 2658336
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    Re: Eco fan for top of woodburning stove

     Putting a fan around the stove allows it to produce the same heat output for a lower surface temperature, and therefore a lower burn rate. QED.  Very simple physics if you look at it the right way.  The fan itself has to be energy neutral because it can't store energy.

  • Tue, Nov 19 2013 17:33 In reply to

    Re: Eco fan for top of woodburning stove

    I'm not going to argue too much with a study but my point stands I think. I've owned various stoves over the years and I feel the point at which they are generating most heat is when the fire is established, has a good ember bed and all the vents are shut down to allow minimal air through the fire. This could take maybe an hour from lighting. You need really good, dry wood for this but once achieved, a stove gets really, really hot. In this state, it is also burning the wood at it's slowest possible rate isn't it? Maybe not. In my mind, the most efficient burn co-incides with the most heat. I can see that a fan can distribute this heat better than convection alone but can't see how I can use less logs to achieve it. Maybe just have a smaller fire I suppose? I'm not knocking it at all.
  • Tue, Nov 19 2013 17:38 In reply to

    • Hillman
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    Re: Eco fan for top of woodburning stove

    You only have to compare an electric fan heater to a radiant bar fire to appreciate the effect of the fan. This seems to apply to radiator boosters as well as your stove fan. The fan operates using the Peltier effect as used in car cool boxes. Probably could lash up a diy version out of an old cool box with one plate on the stove and the other connected via copper to something cold. The DC output could drive a fan. The only system losses are the mechanical energy driving the fan, and noise, if any. Any heating of the fan windings adds to the room heating. A big chill might set in when Her Indoors sees the engineering masterpiece on the stove though!
  • Thu, Nov 21 2013 13:18 In reply to

    • Brisel
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    Re: Eco fan for top of woodburning stove

    I have an 812 Ecofan. Cost about £120 from my local stove shop.

    Great for pushing the hot air around the room & reducing the cold draught that comes across the floor from the rest of the house towards the 9kW stove.

    Mine is only 12 months old but has already had a new motor under warranty. Even the top cooling fins run very hot despite the fan being at the back of the stove top where it should be drawing relatively cool air through the fan. Apparently the fan motor does not like running hot & it destroys the magnets in the motor. My stove is in a recess so I wonder how good the airflow is into the suction side of the fan. 

  • Thu, Nov 21 2013 19:37 In reply to

    • bosshogg
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    Re: Eco fan for top of woodburning stove

     The Vulcan stove fan looks an interesting beast, a stirling engine so should be bomb proof. A little pricey at £168 though!!!   Fan

    Hot damn. I wish them Duke boys was on my side.
  • Thu, Nov 21 2013 21:19 In reply to

    • concreter
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    Re: Eco fan for top of woodburning stove

    Janovich:
     It does indeed do a good job of sending the warm air out into the room and Yes, they are extremely quiet and worth it in my humble opinion.  Does the job well i'd say.
     

    On the strength of these posts and some testimonials on a well known seller of things named after a South American river I ordered one of these this week, it came today and I think it works well (£93 the one I bought) am trying to cure a problem in a cottage with a deep fireplace but I thought that I would try it up here first.

    Now I need another one.

    Elsewhere some folk were wondering about how sad you have to be to be a forum poster.

    I may be sad but now I am warmer too.

  • Fri, Nov 22 2013 10:47 In reply to

    Re: Eco fan for top of woodburning stove

    Well i'm glad you're warmer for it concreter!,...better that way than the other at this time of year Wink

    And on the notion of 'forum posters' being labelled as 'sad'... Well,... Each to their own,..i've got folks i can talk to face to face and i've also got the pleasure of having online conversations too,..so in my eyes that can only be a good thing  Big Smile

     It's good to talk as they say,...no matter how you do it!!!

  • Fri, Nov 29 2013 14:31 In reply to

    Re: Eco fan for top of woodburning stove

    Nobody will talk to me in real life. No idea why.
  • Fri, Nov 29 2013 16:31 In reply to

    Re: Eco fan for top of woodburning stove

    Back In Black:
    Nobody will talk to me in real life. No idea why.
     

    Same here. Back on topic, we bought an eco fan last week and the jury's still out on it. My daughter swears it's colder in the living room now but I'm thinking it might be colder directly in front of the fire but the room temp is more constant throughout the room ??? It used to be colder at the far end of the room but I don't think there's a significant difference tbh.

    http://www.holidaycambriancoast.co.uk/

  • Fri, Nov 29 2013 23:20 In reply to

    • Peter Wells
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    Re: Eco fan for top of woodburning stove

    welshnwilling:
    My daughter swears it's colder in the living room now
      Take it from me Wnw. Daughters between the ages of 13 and 20 always think whatever father does makes things colder. Mind you it improves from then on.

    Two questions though. What size room and what kw from the woodburner?

    Our snug is 14x14 with a 5kw Clearview. Just the right machine for that size of room.

     

     

  • Sat, Nov 30 2013 7:36 In reply to

    Re: Eco fan for top of woodburning stove

    Peter Wells:
    Two questions though. What size room and what kw from the woodburner?
     

    6kw stove and room is about 20 x 12 ft. It's plenty big enough for the room and we often have to let the fire go out after a couple of hours because the room gets too warm.

    As for the eco fan, a hundred pounds is too much to pay for something that you can't tell if it's working or not.

    http://www.holidaycambriancoast.co.uk/

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