I first came across Rocket Stoves a couple of weeks ago at Paul Wheatons friendly website. I still do not grasp completely how they work but I am learning a lot (and asking a lot of questions) … in other words educating myself 🙂
Gasification is a word we’ve encountered many times in relation to high-efficiency wood-stoves. Here’s what I’ve been able to understand so far (excluding professional terms which I still have not got down).
When wood is burned some heat is (naturally) generated together with some gasses. These gasses still contain potential burning energy but in regular stoves they simple escape through the chimney. This is both a waste of potential heating energy and a source of pollution. Efficient stoves that include “gasification” create a kind of “second burning” by (1) containing the gasses in a secondary chamber and (2) by insulating the stove, containing the heat and increasing the temperature (the gasses require a higher temperature to burn). The result is much (drastically more) efficient burning and greatly reduced pollution.
The following video demonstrates the “rocket” burning result of gasification:
The Rocket Stoves depicted in Paul’s website is based around the idea of thermal mass – which is a fancy way of saying “something that can contain lots of heat it and slowly radiate it back into the space”. This can be a couch or a wall or even a water heater.
This idea of thermal mass is well known here in Romania. It is used in typical tera-cota village stoves where the heat is directed in a maze of passages that cause the stove to slowly heat up and then stay warm for a long time (a good stove can be lit in the evening and will still be warm the next morning).
At first I assumed that a thermal mass was an inherent part of the rocket stove. But that isn’t necessarily true. This next video demonstrates a rocket-stove used as a cooking stove:
More information and plans for this kind of rocket stove can be found here.
This application of the same rocket stove burning mechanism shows an insulated burner that is designed to keep the heat inside and direct it to a cooking pot. I think this can be a useful design for a cooking stove that can be used during the summer months because it doesn’t radiate unwanted heat into the space.
One of the first ideas we played around with was using the same stoves for both heating the space and heating water. Though this can work it needs careful consideration. Though it’s tempting to think of the stove as heating the water, it’s useful to remember that as this happens the water also cools the stove!
If you add a water heating coil to a traditional Romanian tera-cotta wood stove it will heat the water, but the stove itself will cool down much faster and will have less effect on the space.
It’s empowering to slowly peel away the layers and connect with the common-sense behind heating systems. It makes me wonder about sophisticated technology vs. simple concepts. On the one hand gasification looks so simple to achieve and yet modern central wood-burning heaters, it seems, cannot achieve gasification without electricity!