Rocket Stoves: Simple & Efficient Systems for Heating Water & Other Stuff

Just to clear the air, rocket stove systems do not involve rockets, nor is it rocket science.

What are they then?

The original rocket stove was designed to be an efficient cooking stove powered by a small fire fueled with twigs and tiny sticks rather than wood logs. It’s burned in a simple high-temperature combustion chamber containing a vertical chimney and a secondary air supply, which ensures almost complete combustion prior to the flames reaching the cooking surface. In summary it’s super efficient, simple and low-tech, meaning almost anyone can build one anywhere in the world. 220px-Rocket_stove The basic design for both a small or large rocket stove can be seen above.  Due to their low-tech nature, they have been particularly valuable and appropriate for environments where people don’t have easy access to electricity or abundant resources. Of special note, are some developing countries which have benefited from building small rocket stoves for cooking purposes, improving quality of life and use of resources. As they’re so easy to build, there are very few barriers (if any) for people making their own – no engineers required (yay).  At a cook stove level they have also been mass-produced at very low prices.

The principles were described by Dr. Larry Winiarski from the Aprovecho Research Center in 1982 and since then stoves based on this design have won many awards, and others have gone on to develop other ‘rocket powered’ items including mass heaters and showers.

A rocket powered shower?  This works by directing the heat from a rocket stove to heat water.  This can simply be a tank situated above the fire, or a water jacket system as used in conventional wood fired water heaters.  For the direct heat systems featured below you require bricks to fashion the fire, a hot water tank (preferably recycled), flue materials, a tank stand and plumbing fixtures. On top of this you need a dose of enthusiasm and a large bucket of mud!

Rocket power shower sketch

Warning: We know this is exciting but there are a number of things to take care of.  Firstly be careful not to burn anything you don’t want to burn.  Secondly and most importantly a hot water boiler contains considerable energy and if poorly designed can reach high pressures and even explode -that is why your home system has a pressure release valve.  Low-tech alternatives can prevent a high pressure situation, familiarise yourself with how to do this safely if you wish to proceed.

Here are a couple of examples of rocket powered showers built by Tim Barker, an international rocket power expert who’s based in S.E Queensland and just happens to be teaching our rocket powered shower workshop this April 25-26 in southern Tasmania!

In it’s most basic and super function form – a rocket shower can look like the one you can see below. You don’t need to spend time, energy and dollars on beautification to get easy, hot water. Tim built this system at the Permaculture Research Institute, you can watch this short youtube flick (narrated by Geoff Lawton) to be talked through the full process of how to build it yourself.

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Using the same design, Tim also built the rocket powered shower below with Very Edible Gardens in Vic recently. The corrugated sheeting means you don’t have to build a rain cover over the top. Brilliant.

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Image by Very Edible Gardens

 The fire is lit in the cob structure below the corrugated iron cylinder. The heat from the fire is directed into this cylinder where it heats up the water.  The water in the tank is not used directly to shower with.  Cold water is piped through a copper coil in the water tank.  The water heaps up in the coil and is then plumbed to the shower stall.

13947568659_b75f1de5a8Tim Barker on the left with a rocket powered shower system part-way built. This photo hilghlights the insulation layer which keeps the water hotter for longer. Image by Very Edible Gardens

Example number two is from Milkwood Permaculture, their design is slightly different to Tim’s in that their hot water tank is vertical instead of horizontal. It is much more similar to a conventional “wet back” hot water system seen on many rural properties.  In this system the rocket stove is contained in the cob structure at ground level.  The hot flue gas then heats a “wet back” (the steel box)  The wet back circulates water to the storage tank on the right and from there can be used later.  The photo below shows it in the “nude”

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3420481892_e1a4b4c736_bMilkwood’s diagram showing how it all works

rocket-stove-water-heater19Sealing it all up with cob adds an extra layer of insulation plus it looks beautiful.

Something else we’ll be featuring and making  on our upcoming workshop is the portable rocket stove, used for cooking in the home, on the farm, at a street party, when you’re camping or at your local tool library – as you can see Megan doing below. These systems are wonderfully basic and effective and can be made from items found in a junk pile.

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Portable rocket stove for easy cooking anywhere, any time – as demonstrated by Megan at the Brunswick Tool Library. Image by Very Edible Gardens.

Rocket power is for people looking to decrease their energy consumption and increase their connection to simple and sustainable methods of generating energy for their own needs. Whether you’re in the urban environment or on the land – live by yourself or with a whole mob of folk there’s a rocket system appropriate for you and your context.

** Join us at our Rocket Powered Showered workshop with Tim Barker this April 25-26 in southern Tasmania to build your own. You’ll also get to make your own portable rocket stove for cooking! **

Great resources…

5 Responses to “Rocket Stoves: Simple & Efficient Systems for Heating Water & Other Stuff”

  1. Rob Sylvester

    This system is very similar to bathroom hot water “chip heaters” (using twigs, bark and small pieces of wood) that were used – certainly in the 50’s, to heat bath water for the “once a week bath. So I guess the wheel has been re-invented! (perhaps a little rounder).

    Reply
    • Adrian

      There is one major difference though: In the 50s design there was no Insulated riser allowing the gases to burn completely before extracting any heat. The chip heaters were pretty inefficient and produced dark smoke consisting of unburned wood gases.

      Reply
  2. Ralph

    Hi,
    I came across a professional wood-chip heater on the East coast of Tassie. I think it was called an “Eli” or something like that. I’m looking for a similar one, just enough to heat a bath. Does anyone know of one or the correct make?

    Many thanks, Ralph

    Reply
  3. Brian Price

    I want to build a water heater for my swimming pool and have decided that I would apply your technique here. Two questions:
    1. Buffer Tank: I’ve seen on Geoff Lawton’s youtube video that the internal “buffer” tank should be stainless steel. I have a mild steel 40-gal tank readily available and stripped. Is it crucial to use SS? Should I weld a flame baffle on the tank to prevent a hot spot and creosote buildup?
    2. Rocket Stove: I have seen so many designs for the rocket stove, I need to narrow down one for a beginner. Ok to use mild steel pipe for entire thing? I would use loose perlite for flu pipe insulation. Need it for burn chamber as well? This will be a mobile project b/c I’ll use it sporadically. I was envisioning two parts for easy mobility: Tank with stand and rocket stove. I need to figure out an attachment method for that as well.

    Hope you can direct me to a project that might be in my wheelhouse.

    Thanks,
    Brian

    Reply

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