Part 1 - Building a simple Rocket Stove / demo at Vida Verde
Part 2 - Rocket Stoves all over the World
Part 3 - Downdraft cooking stove with excess heat accumulator
Some time ago, while looking for information on wood-burning stoves on the Internet, we encountered the so called Rocket Stove. The Rocket Stove has been developed to help people in developing countries by providing them with a cooking stove that burns cleaner and uses less wood. Major work in this field has been done by
the Aprovecho Research center. More links at the bottom of this page.
Enthused by the simplicity of this design and the achievable results we started looking for ways to design a Rocket Stove to build in our house. After collecting and reading a lot of information we decided to build a downdraft version and added a heat exchanger. You can read more on this design here
Later we were asked to demonstrate the Rocket Stove principle at the Green Gathering / Vida Verde event, held in mid-Portugal in April 2007. On this page we show one of the many ways to build a simple Rocket Stove as we did for the Green Gathering and you can read about our findings.
=== Clicking on any of the smaller pictures below to view an enlarged version ===
What do you need to create a good, hot and clean burning fire?
When designing a wood burning cooking stove we need to fulfill these requisites plus a few others to make it a practical device for use in the kitchen.
The rocket stove we present here is for outdoor use only, because it doesn't have a chimney to get rid of the flue gasses. What is called 'the short chimney' below is effectively the burning chamber of the rocket stove and not a real chimney.
The Rocket Stove does amazingly well, combining all these requisites together in a simple design that can be build by almost anyone, even with simple basic materials that are available in developing countries. A rocket stove design is based on an elbow pipe where the small wooden sticks (the fuel) lie on a shelf in the horizontal part and the fire burns in the short, vertical chimney. The short chimney should be well insulated to be able to reach temperatures high enough to burn all gasses properly. The elbow can be made of metal or ceramic material that can resist these high temperatures.
A simple and cheap solution is to make the elbow of clay which can be fired to increase durability. Other options include using ceramic tiles, steel pipe, stainless steel, refractory bricks or special insulating bricks made out of a mixture of clay with vermiculite, Perlite or sawdust.
As you can see we used stainless steel chimney pipe to improve durability.
On the picture to the left you see the different parts we used to build our demonstration model.
The shelf on which the sticks lie is not visible in the picture.
Bringing all parts together the result looks like this.
Only one important element is missing: the insulation around the pipe...
Insulation is very important, especially with a relatively small fire, to generate temperatures high enough to burn all combustible products that are formed during the burning process of wood. Good insulating material that can stand the heat is vermiculite or Perlite. Perlite and vermiculite are made out of expanded volcanic stones. Because we didn't have this, we use expanded clay instead. We also tried Rockwool and screening with aluminium foil but found out that these materials clearly could not stand up the heat close to the pipe! A cheap alternative is to use ash. Although ash might compact in time.
The expanded clay granules we used also supported the pipe and pot support. That was a free bonus we got!
Getting the fire started can be a bit fiddly, but the fact that you can slide the metal shelf in and out is especially helpful when starting the rocket stove. Once it's burning the fire is almost without smoke. You can regulated the intensity by the number of sticks in the fire. In normal use only the points of the sticks burn.
At the far right side of the picture you see the shelf on which the sticks lie. The space underneath the shelf is always free to make sure that enough air can reach the fire at all times, even when the fuel magazine is full with sticks.
In April 2007 we demonstrated this Rocket Stove at the Vida Verde event
(Green Gathering) that was held at Quinta Cabeça do Mato in mid-Portugal. Despite the fact that we build the stove in a few days, mainly with 'scrap' materials we had at hand, it performed very well. To quote the cook: ... incredible how fast it cooks and with so little wood...
We also received a lot of attention from the visitors. Some people were so delighted by the simplicity of our model that they wanted to buy it straight away!
Our demonstration model is very basic indeed. There are a lot of simple technical improvements to be made. After creating a clean and hot fire our main concern is to get this heat into the pot to maximize efficiency.
To get the optimal draft through the stove and to reach optimal heat transfer to the pot you need to keep the cross sectional area of the flue route the same throughout the whole stove, underneath and around the pot. In the picture you see how a skirt around the pot forces the hot flue gasses to keep in contact with the pot to transfer the heat. The sizes of the gaps between pot and skirt need to be balanced with the stove size and the size of the pot.
All this information and more can be found in free publications on the Internet.
Aprovecho.net Education for sustainable living
Aprovecho is a non-profit research and education center located outside of Cottage Grove, Oregon. At Aprovecho you will experience live working examples of Appropriate Technology, Sustainable Forestry, Organic Agriculture, Permaculture, and the interconnectedness that is shared by these systems and with the land.
The Aprovecho Research Centre Advanced studies in appropriate technology. The Advanced Studies in Appropriate Technology (ASAT) Lab studies methods for designing, building, and disseminating cooking and heating technology that is made from vernacular (locally available) low cost materials that can be found easily in the towns and villages where improved stoves are needed.
BioEnergy Lists: Biomass Cooking Stoves
This site contains information to help people develop better stoves for cooking with biomass fuels in developing regions.
Discussion of biomass cooking stoves
Lots of useful information from stove builders all over the world.
Quinta Cabeça do Mato
The 2007 edition of the Vida Verde event was held here. Have a look at their blogspot to find out what more they have in store.
The Vida Verde event (Green Gathering) in Portugal
The website of the Vida Verde organization.
The stove on the Vida Verde event was build and demonstrated by caTo-projects (Carolien and Tom, a Dutch couple living in Portugal) More info on our/this website (alas these are the only pages in English, the rest is only in Dutch.