[Stoves] Practical Stoves- Introducing The Versatile Stove

Wed Nov 16 14:27:05 CST 2016

Kirk and others,

Thanks for the compliments.  An approximate formula I use for burning wood is that the energy content in Joules per gram is 20634-22894*MC where MC is the moisture content on a wet basis, as a decimal (not a percentage).  The 20694 is the lower heating value of bone dry Douglas Fir.  In the second term, 20694 out of the 22894 is the heat no longer available in the wood because it’s replaced by water, and the remaining 2260 is the energy to boil the water itself.  With this formula you’ll have positive energy content up to 90% moisture.  Getting it to sustain combustion would be a limiting factor.  With the downfeed burner I’ve burned wood up to about 50% moisture, though the flames were getting pretty weak.

I imagine drying wood with a stove would work if the wood is fairly small, perhaps up to 2 cm diameter.  Actually, you’ve given me an idea.  The most recent version of the Versatile Stove is side feed with both ends closed, rather than end feed.  See photograph.  The wood going into the side feed door would be angled to the left to burn under the big burner, or to the right to burn under the small burner, or both to heat 2 pots.  This could also allow the small burner, if it is not being used to heat a pot, to serve as a wood holder and allow the wood to dry before going into the fire.  The photograph shows the side feed variation, and the wood drying option.

Currently, I have some sticks soaking in a tub of water to be tested tonight.  If I can get them to burn, along with drier wood of course, then the wood drier option has merit.

More on this later,

Dale

From: Stoves [mailto:stoves-bounces at lists.bioenergylists.org] On Behalf Of kgharris
Sent: Thursday, November 03, 2016 4:48 AM
To: Discussion of biomass cooking stoves
Subject: Re: [Stoves] Practical Stoves- Introducing The Versatile Stove

Dale,

Thank you for the discussion of your recent work.  I especially like the two versatile pot stands.  These look to me to be very useful.  The ability to use thicker and longer unprocessed wood to give a long burn time with low maintenance also adds to the versatility.  I will have to think about the wet wood.  It might be using more energy to evaporate the water then there is energy in the wood.  The Prime stove has a nice design which holds wet wood to the outside of the stove so that waste heat will dry it.  Making provisions to dry it before burning it might be better then burning it wet.  There is a lot to think about in your discussion.

Thank You,

Kirk H.
----- Original Message -----
From: Andreatta, Dale A.<mailto:dandreatta at sealimited.com>
To: 'Discussion of biomass cooking stoves'<mailto:stoves at lists.bioenergylists.org>
Sent: Wednesday, November 02, 2016 8:39 AM
Subject: [Stoves] Practical Stoves- Introducing The Versatile Stove

For some time I’ve been promoting the idea that stoves need to have practical features to make them successful.  Efficiency and low smoke are desirable, but not the primary concern of most users.  Here is my first attempt at providing a stove to do that.  For the moment I’m calling it The Versatile Stove, as it gives the user lots of options for using the stove.

The main features of the stove are:

1.      A very large combustion chamber allows it to burn large diameter wood of any length.  Up to 8 cm diameter has been successfully burned.

2.      It can handle 2 pots, one being up to 20 cm and the other up to 30 cm.  Round or flat bottom can be used.  Actually, a pot larger than 30 cm could be used, but then it is only a single pot stove.

3.      The pots are cradled between the pot supports and are very stable (except pots that are greater than 30 cm).

4.      With the large combustion chamber, fuel tending is minimized.

5.      The stove is powerful, 5 liters is regularly brought to a boil in under 20 minutes.

6.      The stove has some capacity to burn wet wood.  This is still being explored.

7.      Depending on how the fuel is arranged and managed, turn down ratios of about 3:1 are possible.

8.      Unfortunately, fuel use is high and efficiency is low.  This is also being worked on.

9.      Smoke seems to be a function of the fire size, as with most stoves I’ve worked with.  A big fire will make black smoke, the same as any other stove.  Wood that isn’t properly catching fire will make white smoke, the same as any other stove.

Attached is a document with more details and photographs to illustrate what I’m talking about.  There is also information about future testing and modifications, as the development of the stove is continuing.

Also in the pipeline, I’m a very part time professor at The Ohio State University, and I’m working with a senior student group on family size stoves with downfeed burners.  These will be modeled after the downfeed burner developed by InStove for larger stoves.  My work with downfeed burners in August at Stove Camp was very positive, so I think this may also produce a very good stove with a lot of practical features.  More on this after they finish their work in May.

Dale Andreatta, Ph.D., P.E.
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