Batch cookstove with a small riser

[coastalrocketeer]

Just learned NOT to use square brackets inside a post... Could not figure out why everything I'd written past (link goes here) would not show up... Was that I originally used square brackets.

[patamos]

Long flywheel 'stored solar thermal' is so very interesting.

I have been building Annualized Geo Solar heating systems for a number of years now. Pumping hot air (gathered from a collector array) into a large body of earthen mass under the mainfloor slab of the dwelling. In drier regions with hot summers an open bottom(uninsulated) earthen battery can work. Here on the coast it is best done with an insulated battery. Back in the north east US a fellow named Bob Ramlow has implemented a number of 'solar sandbed' systems using hydronics to gather and elver the heat to the sub-floor mass.
Although earth does not have nearly the specific heat capacity of water, it is more stable and easier to contain over the long term.
The best air-based collector system i have seen is 'OM Solar' from Japan, although the do not go for the long term storage.

I think a hybrid of the above three systems using OM Solar collection with a bigger (deeper) insulated earthen mass storage is the way to go...

apologies for the thread drift.

[Orange]

hmm, what about "shoebox rocket" covered with refractory slab and metal plate on top? Then the riser is not needed and the firebox is lifted from the ground.

[Deleted]

Hi Orange,

For a few reasons :
- we don't know the ISA of the DSR yet, maybe it's higher
- the DSR is not performing as good as this core (in terms of average CO ppm) as what Peter said
- we don't know how stable it is (in terms of O2%)
- we don't know if the DSR will scale well or not
- we don't know if the DSR can be longer or shorter
- we don't know the longevity of the secondary air in this arrangement
- we don't know how the top of the DSR will resist the fire fountain

Otherwise it's very promising. The shape allows very compact designs with for examples a symmetrical contraflow design or with a gaz path underneath and the chimney flue on the far right corner.

Regards,

Edit : And I said so because I will build these cookstove in people's homes.. I don't want to be so experimental then.

[coastalrocketeer]

@yasintoda said:

Although earth does not have nearly the specific heat capacity of water, it is more stable and easier to contain over the long term.
The best air-based collector system i have seen is 'OM Solar' from Japan, although the do not go for the long term storage.

I think a hybrid of the above three systems using OM Solar collection with a bigger (deeper) insulated earthen mass storage is the way to go...

apologies for the thread drift.


My reply:

No worries! I love all things sustainable energy related, just live in the cool and rainy and very forested Oregon coast, and wood is a primary local resource, but once I saw rocket heaters I realized how unrewarding, time consuming, expensive and less environmentally friendly feeding our box stove 4 cords a winter is, while still waking up to a cold house in the AM.

Re: sand bed storage/solar geothermal:
Do they use heat pipes or lens concentration in those systems to increase delta-T and heat the sand beds hotter than water could go at ambient atmospheric pressure?

Another point that comes to mind I remember from researching hydronic heating systems is if you are doing a slab on grade heated floor, thermally decoupling that slab from the ground underneath and the foundation at the perimeter is critical to efficiency because the ground is essentially "a 55 degree Fahrenheit heat sink of INFINITE capacity."

One of the things I like about his giant water based thermal batteries, is when they are central to the interior of the insulated structure, any heat that is lost through the tank's insulation just goes to heating that interior.l, like a sand bed probably does under a house.

You could do the same thing with air/hot gasses, with a giant "gravel silo" centrally located inside your structure, and heat the gravel much hotter than water with no fear... If it is in an insulative geopolymer refractory silo, you could heat it up REALLY REALLY hot! lol!

You could use hot air sucked convectively through the hot gravel, from inside the structure down low, to feed heat to an air to water heat exchanger system and heat water with a failsafe that if the pump fails and water gets close to "too hot" a thermo-mechanical actuator of the type used to automatically open greenhouse windows could close the damper letting hot air convect heat from your gravel silo to the water heating loop. If the gravel silo temp stays below the temperature the heat exchanger can tolerate (solder or braze or weld melting temps, depending on exchanger construction method) then the actuator fail-safe, could instead be obviated by using a pumped, "passive drain-back" heat exchanger design.

My entire water and structural heating load for our not well insulated 2600 sq ft house would probably be met with a 100-200 gallon insulated water tank running radiant floor and wall heat year round, and could be heated by a combo of solar thermal, direct hydro electric-thermal storage, (No batteries, generator power goes directly to heating element in tank), wind power, and wood,

Even though we rarely get up to or above 70F, we also rarely go too far below 40F. And not really ever dip below 20F. Usually when we don't have sun we have water and wind, and if we don't have any of those, we ALWAYS have wood... Especially after wind storms, if we have a way to use branches and twigs.

Our big issue is wind and associated cinductive and convective heat loss... And high humidity makes air a much higher heat capacity, conductive and convective medium.

I swear 40 in a humid place feels colder than I have felt at 20 in drier air sometimes!

Air leaky structures like my house (and most buildings built "to code, inspected and approved" in the US, are air sieves...

Especially when you have the differential pressures from one side of a house to another created by the occasional "Arctic blast" storm with cold air, 40-60 mile an hour sustained winds, with gusts to 125mph.

Add to that some side ways rain during the wind and gusts, and you will rapidly discover via water and cold air ingress, exactly where the building envelope failures that would not be an issue most places are.

[coastalrocketeer]

Another interesting concept is that you can use hot air to reduce conductive heat loss from an insulated storage tank better than ANY level of insulation placed directly around that tank.

Envision this:

You have a tank of 90C hot water. Through 3" of poly ISO foam, it loses X number of BTU's through it's insulated surface area.

Now create small but sufficient air gap between the tank and the insulation, and heat that small volume of air to a higher temperature than the water, say 100C.

Now the water tank will lose ZERO BTU's to any outer surface that is in contact with gas (air, or flue gas, for instance, that is warmer than the surface of the tank in that spot, which is 190F (at the top) assuming the tank is stratified.

The air, having a lower conductive heat capacity than the water, should conduct enough less heat into the slightly larger insulation surface area, to reduce total heat loss, and the water in the tank it's self will effectively have infinite insulation.

There will still be radiative heat loss, but I believe this is significantly less of the total losses from a tank with a relatively low temperature, high density her storage medium in it, than conduction is.

[coastalrocketeer]

I believe thermo spa hot tubs use the water heating, control electronics, and pump motor waste heat heat being produced inside the insulation envelope of their design, to do just such a thing and increase their heat maintaining efficiency when covered and not in use GREATLY over competitors. (They insulate heavily the perimeter and less so the floor of the "box" the tub and it's "guts" reside in, and not spray the underside of the tub it's self with insulation...

You could use any source of waste heat hotter than the tank (or gravel silo!) to create this "infinite insulation" effect. Pumps and other heat producing electrical devices that can stand up to operating in air at your desired temperature range can be used.

And even just lowering the delta T (temperature differential) and conductive capacity of the tank (or solo's) solid, conductive surface, and it's coupling to the insulation, should decrease heat loss from the tank (or silo)

Friendly disclaimer: As with all of my ideas and pronouncements, I may be partly or totally off base with any of this, so feel free to provide your own knowledge and experiential data to shoot holes in, or confirm, any of what I say anywhere!)

For the love of learning together and from one another, I thank you all for your participation!

[coastalrocketeer]

I don't know if anyone else using tapatalk is having trouble reading my last two posts... But I am. (Killing the app and restarting cleared issues up... Seems to happen when I make especially long wordy posts, which I've been on a kick for the last day or so.)

On that note:

My apologies for being such a wordy Eco-nerd... Sometimes I get inspired with reading other's comments and ideas, and trying to integrate them into expanding my own understanding, correcting misconceptions I have, and combining intersecting disciplines and areas of knowledge, while documenting the lines of thought that those other parallel and intersecting lines of thought, and new sources of information germinate. If you find it overwhelming I apologize, and I guarantee that, whatever you may think, I am NOT hooked on methamphetamine. Just cannabis, coffee, and tobacco.

FYI, those 3 are listed in order from most to least medicinal, and least to most harmful... :-)

Feel free to skip over my ramblings, or if you find them more disruptive than beneficial to the thread you are trying to enjoy, and/or learn from, just ask me to copy them to a thread of my own.

[kiwinutter]

I am beginning a retrofit of my masonry open fire this weekend.
Putting a batch core in and combination of metal bell with either masonry internal or external mass for heating my 100 year old wooden moderately insulated ( draughtyas hell) 130 sqm house in New Zealand.
We are unlucky if our winter temperatures drop to -5°c more than 10 times a year.
I have between 900mm and 1000mm maximum internal height to place a batch rocket in.
Floor area would be .75sqm.
If I was to try your core modifications yasin what size would you recommend. I have hard fire brick and plenty of it and also access to insulative materials for riser.
Also what riser arrangement do you think at this stage would be the better half octagon/half round at back of riser. From reading this thread it seems that would be the better configuration. Would a curved or 45° ramp at the bottom be a hindrance. I have tried something in my outdoor bath that seems to be working well. I have let the ash build up on the ramp and it has naturally formed a concave ramp this seems to ( can't see it from the top bricks permanently mortared in) assist in a slight tumble of the rams horn back towards the port since I let this build up it goes smokeless significantly faster. I'm waiting for the testo from work to get back from calibration.

[satamax]

Kiwinutter,

That's you who asked me about this, on permies?

Anyway. Build yourself a Bell un front. Ans use a plunger tube in the chimney and fireplace

Check those threads.

permies.com/t/40/31382/Rocket-Stove-cast-riser

donkey32.proboards.com/thread/1354/build-house-detroit-scrappy-approach?page=1&scrollTo=13248


donkey32.proboards.com/thread/2076/fireplace-batch-box-conversion


donkey32.proboards.com/thread/1274/rocket-heater-fireplace-design

[Deleted]

kiwinutter

I didn't post here for a while, but we have done a lot more work since this version. Here is the link to the current version of the cookstove : webcloud.zaclys.com/index.php/s/zgQgzjo4dCzKvCC
It's not completly ready, but you'll get the sizes and the idea.

If you want to see more detailed explanations and testo results about the former version, have a look here : uzume-asso.org/session_batch_2018.html

I didn't try the ramp because I don't believe in it. I think it will be counter productive because the flames are thrown upwards whithout having the time to make good turbulences down in the riser.
I also think that you don't need insulation materials. Having a by-pass valve that gives you +100°C in the chimney flue is much more important in my opinion. You'll get to a very good combustion soon if you can create a proper draft.

If you want to cook, then use this sketchup file. It's a 160mm batch. 8kg of wood per load. Very nice for cooking !

You'll see on the drawing angle iron around the core to compress it. It's very important if you want a heater that lasts long. This "batchblock" core is cubic so that it can be compressed with this system.
In russia they use it a lot, see here : kirpichiki.pro/gallery.html
This method is coming in France too, and I believe that's a great progress. Everything moves after a while.
Also, don't build it with clay mortar, it won't last.

If you can make testo measures I'd like very much to see them. My CO cell is dead now so I can't measure anymore.

You're a kiwi, I'm a cagou ! Neighbors so to speak !

Regards,

[Jura]

Mar 8, 2018 10:58:21 GMT -8 @yasintoda said:

I didn't try the ramp because I don't believe in it. I think it will be counter productive because the flames are thrown upwards whithout having the time to make good turbulences down in the riser.

After I got know about the ramp I had the same gut feeling but Peter confirmed he noted better results with the ramp.
Have you had time to measure the same setup with and without the ramp?

Dec 31, 1969 16:00:00 GMT -8 @yasintoda said:

You'11 see on the drawing angle iron around the core to compress it.

You mean the part that you named "cadre coeur" in your SKP, right?

[Source] @yasintoda said:

In russia they use it a lot, see here : kirpichiki.pro/gallery.html

This method is coming in France too, and I believe that's a great progress.

Do you have the direct link to the gallery which shows this application?

The link you posted directs to the listing of galleries. (which I'll browse anyway but later)

I have seen this photo before before but gave it a cursory look only and thought the steel frame had been used to speed up the construction process.

Mar 8, 2018 10:58:21 GMT -8 @yasintoda said:

Everything moves after a while.

So Heraclitus was right with his "Pantha Rei" statement :-)

Sorry for the CO probe. What happened to it? "karoshi" ? :-)

[Deleted]

Hi Jura,

I haven't tried the ramp but I think you should remember that this is not the standard setup of a batchrocket. Things that worked before may not work now.

It is the "cadre coeur" layer.

At kirpichiki nearly all their heaters are made like that. Your image shows it well.

For the CO probe it was simply that I used it and it became old. It's a very fragile machine.

Regards,

[Vortex]

"cadre coeur" translates to "Heart Frame"

I've used the technique on several stoves I've built. I first saw it on a stove in Austria.

Neat the way they wrap the stove in wire mess and tile it after

[Deleted]

Nice done, Vortex ! You made a complete frame in which you built the stove or you made it like in the sketchup file ? Were there single skins ? Do you have pictures ?

In french the firebox plus gases combustion chamber is called the "heating heart", "coeur de chauffe".
So that frame is holding the "coeur de chauffe" completely, that's why I called it "heart frame".

In france we need to insure our stoves for 10 years, just like houses. It changes the way you think, for sure !