Rocket stove mass heaters...

interesting concept... can be used to heat your BOL with an eighth of then wood...

rocket stove mass heater

rocket stove and butt warmer (alternative energy forum at permies)

 

Combine them with cob building and you've got the heated bench.

 

Almost all of the stoves in the videos have a cleanout just after the combustion chamber. It seems that the more efficient and cleaner burn created from the combustion chamber's high temperature and dwell time burn the smoke (unburned carbon fuel) nearly complete. That means there should only be fly ash in the exhaust pipes. It also seems that the system creates one heck of a draft, so fly ash should not be a constant problem.

I really like this design.

 

I wonder if it could be used with a concrete bench or floors to heat a building /room with instead of cob materials...

 

Me like. Nice concept and design! I can see the advantages of combining a rocket stove and a mass heater. The lower fuel requirement, the use of the waste heat, everything.

 

Don't get me wrong, these aren't miracle devices. There is only so many BTU's in a given piece of wood. The stoves in the videos are heating a rather small area with a large mass/heat battery.

If you would build this type of heater into a house (average of 1500 to 1700 square feet, two stories) you will still be feeding it several chords of wood per winter. Plus you would have to figure out a way to get the heat from floor to floor, room to room.

Did you notice that the buildings that they were heating were usually only one room? Or that they had to embed the combustion chamber into a wall to spread it out between rooms? There is a reason for this. I think you would have to have several stoves of this type for a typical given dwelling, especially if it is a multi-story house.

These facts aside, I'm sure an intrepid and engineering homeowner could figure out a way to get a rocket stove mass heater to work for them.

Anyway, I still like the design. There are a few companies making a version of a metal or part cast iron home rocket stove. I'll have to find the old literature and put them up post haste.

 

More efficient combustion means less ash

As explained by Gunbunny, there ought be less ash produced by a rocketstove design. It is possible to incorporate an aperture for ash removal for vertical fuel loading designs, but the apperture would need to be insulated and sealed during combustion for optimal burning efficiency.

 

IF anyone wants to try building one here is a spreadsheet.

Rocket Stove Design Base - RocketStove Design Tool Instructions

 

It looks like a good resource

It looks like a good resource to design a heater to the dimensions of the raw materials at hand. getting the proportions right for the fuel aperture, fire chamber and chimney are important to the efficiency of the stove. Using insulation to contain heat in the fire chamber and chimney is important to combustion efficiency also.

 

As there is an effect needed for draft, stack temps etc: I'd follow the formula.



Quotes from users
<dl><dd>p. 80: "It is extremely efficient, reaching 90 percent combustion, and almost all the heat is then stored in the cob mass bench, to be slowly released over days!" -Ianto Evans</dd></dl> <dl><dd>"As for our own bench, it takes about four hours to get totally warm. From a 4-6 hour burn time once a day or every other day, we can maintain a comfortable temperature in the house of about 65 [degrees] F, even on cold days." -Tom and Calleagh</dd></dl> <dl><dd>p. 89 ibid: "On days with no sun we run our stove two to three hours in the evening, burning about a five gallon bucket full of wood. For regular winter temperatures of 35 to 50 [degrees] F, this keeps our house at a comfortable 60 [degrees] to 65 [degrees]F." - Bernhard Masterson</dd></dl> <dl><dd>p. 93 ibid: "Ianto and I measured 1000 [degrees] C (1800 [degrees] F) in the combustion chamber and 32 [degrees] C (90 [degrees] F) in the top of the chimney --- the rest of the heat was kept inside the house." - Flemming Abrahamsson</dd></dl>Rocket mass heater - Wikipedia, the free encyclopedia


In addition to gunbunny's posts; raising outside temperature from 35 to 55 to 60-65 inside is a 30 degree increase. A 30 degree increase over outside temps won't get it done here on the mountain.

 

That 30 degree change is not set in stone. If the house is draft free, and insulated, a huge change would not be difficult. I've been in an igloo, where body heat, and a single candle made it unbearably hot.

Lets also not forget that the rocket stove seat is going to be enjoyable to sit on when it's a bit chilly elsewhere. Just need a good implementation.

 

Upon reading these posts on the rocketstoves, I was lead to a website from a company making portable rocketstoves: www.stovetec.net I was rather impressed with the specifications that they gave, and the price was rather inexpensive for what I was expecting to see.

So, I ordered one. (Actually a single door metal lined stove, and a water pasteuriser) Stove-tec replied rather quickly, and emailed a UPS tracking number about two hours later. When I checked the tracking number, the packages were not only out of the store but already out of the UPS shipping facility onroute to my location.

The two boxes arrived on Saturday. I just opened then and inspected the contents today. The stove is well built, and the pasteuriser is made of stainless steel with a cast aluminum spout. According to the manufacturer, it holds 4 liters. Why Liters? The top of the pasteuriser has embossed oriental letters on it, indicating that the unit was made somewhere that uses the metric system. The stove is marked made in the USA.

Not to waste time, I pulled some water out of a nearby pond and cut some small branches and split a few 4-5" logs into quarters. I set up the stove and pastueriser, started a fire in it's belly, and proceeded to feed the small sticks in the 4"x4" chamber opening.

The pastueriser has a vial partially filled with wax, so when the water heats to the proper temperature, it melts. Simply remove the indicator and turn it upside-down again to let it solidify for next time.

After about 50 minutes, it melted, indicating that the water should be potable. I haven't tried the water yet... I don't know enough about pasteurisation yet. I don't know if 50 minutes to get to 165 degrees F is long enough to purify water of it's living organisms or not. I could have gotten to temp sooner, if I would have fed the stove more sticks. I'm not sure that you could get the water to boil, though.

I seemed to have cut far too much firewood for the stove. I actually only used a few 1-2" wide sticks about a foot long, and only two of the larger quarter pieces of logs that I split earlier. I did use about a dozen of the smaller branches getting the fire started. It really didn't take much.

I took several pictures of the whole process, and will write up a review later in the week when I can get the time.

 

As I promised, here are the pictures. Sorry it took so long, but that's another story...

#1 - getting water from the pond. COLD COLD COLD
#2 - stove and pasteurizer set up, filled, and wood ready. Ignore the green turtle sand box- it has no relevance to this test.
#3 - closeup of wood. I used less than 1/8 of what is here.
#4 - sealed wax indicator unit before I started the fire.
#5 - stove lit.
#6 - closeup. I tried to shove as much of the little stuff in there.
#7 - bigger sticks caught easily after the previous bunch burned up.
#8 - small chopped logs. These were the only two that I used.
#9 - looking down from the top of the pasteurizer into combustion chamber. There was some smoke, but the wood was wet.
#10 - Indicator says water is potable.

 

A couple of extrainious thoughts;

The unit is actually rather small, and relatively light for a clay filled, metal lined, metal bucket with a cast iron top.

The pasteurizer is well thought out, with handles exactly where you need them to use the spout with ease and accuracy.

The outside of the stove never got hot enough that you couldn't touch it. When I emptied the ashes out of it about an hour later, there were actually still burning embers. I dumped them out on the ground and stomped them out. I could put my hand in the combustion chamber five minutes later.

I cut way too much wood. I could have pasteurized several gallons of water with what I had laying on the ground near the stove.

I am going to email stovetec and ask for some more specific information on the length of time needed to pasteurize water, and how to get one of the stainless steel pots that they show on their website. The pot has a second wall around it to direct the stove gasses around the sides of the pot to make it more efficient.

I still have the water from last weekend. It is in the jug marked "distilled water". It is sitting in the sun, in a nice, warm room. It hasn't gotten discolored, and it doesn't smell. I'll drink it once I converse with the people that I bought the pasteurizer from, to make sure I did it right.

#1 - My daughter doing her science school lesson about life in a pond. Kind of the wrong time of the year for that, if you ask me. We did see some newts, and a pair of small fish swim by. The water is so clear, I almost (not) think you could drink it as it was.

#2 - Picture without the flash. The flames are actually hard to see in the rocket stove; you have to get down and look into the combustion chamber to see them. You have to keep pushing the fuel into the stove every minute or so. You would be supprised how fast it burns those split log pieces up.

#3 - Sitting around waiting for the water to get pasteurized. Since you can't really get any heat off of the rocket stove, we had to use the chimnea. For some reason, you can't see the flames in the picture, but I had it stoked pretty good. At some point I'm going to try a small cast iron dutch oven in the chimnea. I figure one of the rolls from a frozen, premade cardboard tube muffins like Pilsbury. That sounds pretty good.

 

I got an email back answering my questions:

These guys are great to deal with, they get back to you quickly, make a great product, and ship it the same day. What more could you ask for?

 

Gun bunny the research shows that a rocket mass heater uses 1/4 to 1/5 thje fuel that a conventional wood burning stove does. Smoke is unburned fuel and add that to the stack temperature and there is even more waste. With a mass heaters exhaust temperature being around 100 to 120 degrees and the gass coming out clear, consisting of only CO2 and water vapor you can see that it is much more efficient. Add to that the EPA is considering the wood slow burn heaters because of carbon particle polution.

 

If the house is "draft free" then unless one opens a window, where does the combustion air come from ? Did I miss an air intake somewhere ? This is an interesting concept but it appears to have some flaws and would not have any advantages over wood or pellet stoves in the realm of the snow monkeys.

 

The draft comes from the same place your pellet stove gets it.

 

The only illustrated air intake is the top of the feedbox which uses the indoor room air.

What is needed is an outside air intake, which the featured stoves do not have.

When the house is "draft free" it would appear little outside air can enter the house to feed the fire, necessitating the addition of an outside air intake.

One could always just open a window but then your house would not be "draft free" and you'd have a draft blowing cold air across the room, sending your nice warm indoor air up the chimmney