Eric Hammond wrote:The original poster wants to use a rocket stove, not a mass heater. This is a perfect way to make steam.
No...the same laws of thermal dynamics apply. A BTU is a BTU is a BTU...
In the case of a rocket stove it uses less FUEL because of the application, a quick hot fire to perform work, which is heating up food for a short duration of time. This is much more efficient then using a standard woodstove and heating the stove to cook food because the
wood would still be burning long after the food was cooked. In that sense it is a waste because heat is being produced for nothing.
In the case of a rocket stove making steam, all it would do is flash water to steam, but unless an continuous supply of wood was put into the rocket stove, the fire wood quickly burn out too, and returning condensate would no longer flash to steam.
A cord of wood, whether it be saplings, or a cord of wood from mature
trees, has still the same MASS (128 cubic feet). With the saplings, the same btus are produced (assuming the wood is of the same species), the wood is just consumed much faster due to air space around the wood as it burns. While with the standard sized
firewood, the same btus are derived, it is just burned over a longer period of time. The key is time, but the BTU's do no change. To illustrate this, take a cubic foot of wood and run it through a rocket stove with a kettle of water on top of it. At the same time do so with a cubic foot of standard size firewood with a kettle on top. The rocket stove will flash to steam quicker, but also come off boil quicker too. The standard sized firewood will take longer to come to a boil, but will boil longer too. In fact, assuming the tests can be done with the kettle the same distance from bed of the fire, the standard firewood
should give a SLIGHT amount more BTU's because it is derived of more heartwood and less bark like the saplings, but it would be a negligible amount granted.
* That is why a rocket stove is great for cooking food. Short, quick fire.
* A standard woodstove is rather inefficient because most of the heat goes up the chimney (50% efficiency) It is poor at cooking food, and as we will see, poor at heating a residence.
* A
rocket mass heater uses mass to absorb more heat that would normally go up the chimney as wasted heat, and radiates it slowly thus being more efficient for the amount of fuel burned.
1
