[Stoves] Hybrid cooking-stoves: solar+fuel? (Martin)

[Boll, Martin Dr.]

Dear Jeff, Crispin and Tom (Reed),

Jeff,
Sorry, I did not realize, you had already the same idea of combining solar
and fuel-stoves (before me!!)
In all my thoughts, especially about stoving, I am nearly sure that I am not
the first with any idea, but I don’t know who and when as well as not pro of
contra of real facts. And so I write. 
Often I realize an unrealistic touch. But when I see the pictures of the
first tries for flying and what came from such ideas, I think you cannot
fail really, because of realizing false ways and then changing. 
- Staying by the subject of flying: Who would not whish an airplane really
driven by wings, even the current and successful constructions went another
way than nature?   
Technology changes, the point of view changes and so possibly "old and
silly" ideas get unexpected new sense.
Mostly my success is: having re-stirred in an old topic and reactivated the
interest of the list participants in that, and then going in another very
unexpected direction, and we all have profit from that.

-The wheel rotates always the same way, but the street is always different.-

(Certainly already said by someone, but I never heard this sentence)

 (Martin)
----------------------------------------------------------------
Jeff Davies wrote:
> Message: 4
> Date: Mon, 17 Jul 2006 19:20:35 -0400 (EDT)
> From: "Jeff Davis" <jeff0124 at velocity.net>
> Subject: Re: [Stoves] Hybrid cooking-stoves: solar+fuel?
> To: stoves at listserv.repp.org
> Message-ID: <31029.152.50.3.3.1153178435.squirrel at www.velocity.net>
> Content-Type: text/plain;charset=iso-8859-1
> 
> This is a petty idea (my idea not Martins) but what if we painted the
> stove black (optional) and set it outside to warm up. That way the stove
> would be started warm/hot. Not a cold startup. Less indoor pollution?
> 
> Jeff
-------------------------------------------------------------

Crispin,

You make me come down to reality, with your comment. I admire the idea of
your Vesto, which preheats the air by re-use of the (not wasted) radiation.
My proposal for (continuous) solar air-preheating is certainly "oversized"
compared by the gained effect for normal stoves, and the price for the
necessary equipment.
But would it make sense to make that, in order to be able to burn bad
burning fuels or run a smaller stove than possible without air-pre-warming?
-I think by that e.g. of a "small-powered"-retained heat cooker. 
-I am aware, that such a retained heat cooker is simpler done with only a
(or 2-4 if necessary) tea candle(s).
-When normal cooking is done normally divided into ("speed-up")-boiling
followed by separately done retained heat cooking, it is important to get
maximum power from the first moment, and the possibility to stop directly
after reaching boiling point. Otherwise it is unnecessary fuel consumption.
I think, your new liquid-fuel stoves can do this very well.
-Generally I do not believe it is (simply!) possible to turn a stove so far
down, that you can keep the - _good_ isolated pot only at a temperature of
85 to 100°C, without boiling. So I think the retained heat cooking must be
done far more than normally done (In all parts of the world, especially more
important in Europe and North America, were electrically cooking is done!)
Frans Peeters suggestions and tests with a Duart-pot for low temperature-
and retained-heat-cooking are remarkable and show, what is possible, if
desired.
Beside a pot-shirt is retained heat cooking so important for economical
fuel-use, so that "hunting" for the last percent of better fuel-use seems to
me far less important.

(Martin)
-----------------------------------------
Crispin wrote:
Dear Martin
 
I think that it is not worth the trouble to preheat air in a separate solar
device because of cost.  IT is much better to preheat air using the stove
because little is lost in the process (unlike with solar heated air which
has to be piped into the stove) and because it is portable, in the sense
that wherever the stove is, the preheating is, with or without sunlight.
 
You are correct in your assessment of the amount of energy needed.  For a
regular cooking fire about 500 watts will do very well.
 
A Vesto recycles about 500 watts of recovered heat back to the fire.  It
does this within a very short time of lighting the fire.  I don't think it
is worth the expense of solar preheating to cover for that first minue or
two.
 
Perhaps it would be useful on a larger industrial system where the losses
are already being recovered and it is really worth the expense to collect
the heat.
 
One possiblity we though might fly was putting a Vesto or similar small
stove under the pot sitting on a solar cooker.  It would boost the boiling
rate a great deal and could be fired with wood if the sun failed.  That is a
boimass stove-equipped solar cooker rather than the other way round!
 
Regards
Crispin

----------------------------------------------------------
Tom,
Thanks for the information about raised viscosity by raised temperature of
gasses.
This fact in mind: What do you think to use static-mixers, to get a better
mixing, which I proposed sometime ago, to compensate low draft? 

Regards to all of you


Martin



>    3. Hybrid cooking-stoves: solar+fuel? (Boll, Martin Dr.)
>    4. Re: Hybrid cooking-stoves: solar+fuel? (Jeff Davis)
>    6. Re: Hybrid cooking-stoves: solar+fuel? (Thomas Reed)
> 
> 
> 
> > Dear Crispin,
> >
> > Since sometime, I am thinking how to pre-warm primary and secondary-air,
> > in
> > order to get a better blow without fan.
> >
> > One idea was, to pre-warm air in a concentrating solar-trough, or just
> by
> > a
> > mass with black surface, possibly covered with glass.
> >
> > The second step in reflecting then is:
> >
> >
> >
> >  Why do we not think of hybrid-cooking-stoves: combined solar-fuel-
> stoves?
> > (
> > whatever fuel)
> >
> >
> >
> > In a certain time before starting the fuel-stove, solar heat-collection
> > could be done in advance, so the fuel-stove could run with less fuel,
> but
> > getting a powerful output. The power of the solar-collector I guess can
> be
> > between 300 and 1500W.
> >
> > Advantage was: quickly speeding up the fire and simmering by collected
> > sun-energy. Cooking would work by different weather-conditions, not only
> > by
> > sunshine.
> >
> > Was it worth to try a bigger-scale simple pre-warming of air for your
> > Libhubesi-stove?
> >
> >
> >
> > Regards
> >
> >
> >
> >
> >
> > Martin
> >
> > _______________________________________________
> > Stoves mailing list
> > Stoves at listserv.repp.org
> > http://listserv.repp.org/mailman/listinfo/stoves_listserv.repp.org
> >
> >
> 
> 
> --
> Jeff Davis
> 
> Some where 20 miles south of Lake Erie, USA
> 

> ------------------------------
> 
> Message: 6
> Date: Tue, 18 Jul 2006 09:44:03 -0600
> From: Thomas Reed <tombreed at comcast.net>
> Subject: Re: [Stoves] Hybrid cooking-stoves: solar+fuel?
> To: "Boll, Martin Dr." <boll.bn at t-online.de>
> Cc: 'Frans Peeters' <peetersfrans at pandora.be>,	Stoves-List
> 	<stoves at listserv.repp.org>
> Message-ID: <44BD01C3.4090206 at comcast.net>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
> 
> Dear Martin:
> 
> Your instinct to recover waste heat is admirable.  However, the
> viscosity of gases rises (T^1/2?) with temperature, so you will have
> more trouble mixing hot air with hot gas...
> 
> Good Luck,  and report progress...
> 
> TOM REED           BEF
> 
> Boll, Martin Dr. wrote:
> > Dear Crispin,
> >
> > Since sometime, I am thinking how to pre-warm primary and secondary-air,
> in
> > order to get a better blow without fan.
> >
> > One idea was, to pre-warm air in a concentrating solar-trough, or just
> by a
> > mass with black surface, possibly covered with glass.
> >
> > The second step in reflecting then is:
> >
> >
> >
> >  Why do we not think of hybrid-cooking-stoves: combined solar-fuel-
> stoves? (
> > whatever fuel)
> >
> >
> >
> > In a certain time before starting the fuel-stove, solar heat-collection
> > could be done in advance, so the fuel-stove could run with less fuel,
> but
> > getting a powerful output. The power of the solar-collector I guess can
> be
> > between 300 and 1500W.
> >
> > Advantage was: quickly speeding up the fire and simmering by collected
> > sun-energy. Cooking would work by different weather-conditions, not only
> by
> > sunshine.
> >
> > Was it worth to try a bigger-scale simple pre-warming of air for your
> > Libhubesi-stove?
> >
> >
> >
> > Regards
> >
> >
> >
> >
> >
> > Martin
> >