Most efficient rocket stove howto

Hi Permies : )

I plan to use a rocket stove to produce all the heat for my home (an old and ruined stone wall house I've been fixing from the gorund up for the past 12 years)

What I have in mind is to heat water AND, at the same time, clean air to heat the house. Clean air would be pumped through two thick pipes around the barrel and then each would go to one of the two floors in the house, to finally split into smaller pipes that would go to each room of the respective floor.

After reading you all, and googeling a bit, I have a fantastic design in mind (see image attached)... but because I have actually no idea on how to do this :[ it would be great if you could tore it apart, and tell me why it won't work how I should actually do it XD

I am thinking on something like the image attached. If by any chance this design made any sense, then these are some doubts maybe you can also help me with:

- is it better to have air pipes that spiral around the barrel, or just a second barrel with an intake at the bottom and two outakes at the top?
- having no mass, would the exhaust be too hot, thus wasting a lot of energy?
- are there any precalculated optimal dimensions for the rocket stove? (burn tunnel, heat riser, distance between heat riser edge and barrel...etc) I've found some variations and wouldn't know which one to pick
- would you take air pipes to both floors, or woud it suffice taking it to each room on the top floor and then have a connection with the room underneath to let air flow as it cools down?

Thanks for your time guys, If this works out I'll share the results with you

Winter is coming!

Hi Pablo;
Welcome to permies !
I highly recommend you  purchase, read and study the "Rocket mass heater builders  guide" Written by Ernie and Erica Wisner acknowledged master builders. Readily available on line.
 
I'm afraid your design is not going to work out for you.   A rocket mass heater core has a very specific design and dimensions.  Although tweeking dimensions is a common practice ... in most cases the tweeks are later removed and tried and true dimensions are followed. From your drawing, I see way to many tweeks with your design. Build a tried design first... enjoy it , then play around and see what else you can make work. That way you have a base design and building experience to revert to.
Your hot water idea is a very dangerous thing to play with. NOT recommended for beginners. Water flash boils and expands...   called squish /Boom ... not something you will want to experience. Don't do it yet.  There are other better ways to make hot water safely.
An RMH is a fabulous thing but its btu  potential has a  limit. Use it to heat your stone house, make sure to isolate from any outside wall ! Your stones would rob heat and give it away outdoors...  you want all that heat indoors.
Your piping / blowing warm air thru pipes to will be inefficient, with heat loss from the pipe as it travels to the other rooms. It is worth trying though.  You may find that one common room with the rmh will be nice and warm , and your other rooms will be cool (nice for sleeping). After all you are in Spain ... how cold does it get ?
If you need to heat hot water may I suggest a separate outdoor rmh specifically and safely designed to heat hot water (no chance of squish boom ) There is a post here on permies showing that build in Australia .  It used large tanks one with water inside the other that a rmh is venting thru.  I will attempt to locate that  post for you, as my time permits.
   

Pablo, welcome!

As Thomas has pointed out there are several major concerns with your design from function on one hand to safety on the other. I also highly recommend getting a copy of Ernie and Erica's builders guide. No matter how much research you can do online, it is an invaluable reference manual that I have zero regrets on purchasing. I balked a long time on getting it due to the cost. Once I had it and read it I kicked myself for not having purchased it sooner.

One thing that jumps out to me about the general design is the principle. It's something that took me a while to recognize is my own design principles, but once you do it opens up all kinds of ideas. It seems to me that you are attempting to take a RMH and make it work like a traditional gas or electric centralized heat furnace. The short of that in general terms is it will not work. That's another area where Ernie and Erica's book will help you tremendously. Trying to heat air and duct it to somewhere else is somewhat contradictory to the principles and functions of a RMH. What could work however, is to look at the house in terms of natural convection currents and cold air returns. Ask yourself questions like; If I create heat over here, and that heat causes an updraft of hot air, where is it going to go? It's going to displace relatively cooler air, so where is that cooler air coming from? Can you create cold air returns along the outside wall edges of rooms on the second floor to allow the coolest air to draft down and the hot air to "fill up" the upstairs and ultimately heating the house?

If you are going to push ahead with centralized heating concept, I would look more at a rocket heater/stove than a true RMH. I would look into means of passive air circulation with cold air returns, creating a natural air circulation.  Instead of trying to wrap pipes around something and heating them consider how the heat riser and barrel/bell function and essentially adding a second bell or barrel over the first one that could be ducted to draw in cooler air from down low and pulls heat off the primary bell and carries it up through other ducts and directs or distributes it elsewhere. There are safety concerns here as well, but I believe they are lower risk and easier to mitigate than your original concept.

I hope that helps.

Caleb, Thomas, thank you very much for the welcome and your advise.

You point me in the right direction. I will buy the book, looks like a very good reference guide.

I will go through with the idea of ducting hot air - even if it is less efficient than heating a mass - because I will need heat to get quick to the diferent spaces of the house, and then I don't care that much if the house cools down quick too when I leave. But I'll do it considering your points (specially safety) and using the book as a reference.

Caleb, you are right it doesn't gets that cold in Spain after all, but it is because of that that the original house was not designed in a way where a central rocket mass heater could heat the whole house. I will have to have it placed on a small storage room on the side of the house, not being able to heat the house.

That's why, looking for efficient stoves, I ended up at permies reading about RMH and trying to understand how I could use that much heat and efficiency to produce hot air for the whole house, and wasting as little heat as possible through the exhaust.


If that's ok I'll keep posting about the design and advancements, maybe you can help me out as I advance and we can all share the results : )

thanks!

Hi Pablo;    I found the video I was looking for and its really cool (    )   Geoff Laughton's  Rocket stove water heater .     This is a safe way for anyone to make hot water.

Here is a link to a specialist heater forum which will provide you with a large amount of background for ideas.

http://donkey32.proboards.com/

thomas rubino wrote:
I highly recommend you  purchase, read and study the "Rocket mass heater builders  guide" Written by Ernie and Erica Wisner acknowledged master builders. Readily available on line.
   

Thanks for the recommendation - I'm wondering - does the Wisner book include information on Peter's batch boxes and its evolution?  

thanks!

If I'm going to purchase the Wisner book, does anyone think I also need the Evans and Jackson book: "Rocket Mass Heaters" ?  I'd rather stick with just one book in the spirit of minimalism and owning less things.

Hi Peter;
If you can only afford one book than the Wisner's book is the one to have.