Among the first order expenses and logistical problems to address when you have infrastructure is the question of energy. The conventional model of energy management is that a building should be some flimsy and empty box with energy, water, gas and oil being piped into it from the outside. In other words, conventional buildings are useless without being connected to a grid of electric cables, gas pipelines and sewer systems. This is obviously not appropriate for our projects.

The focus of this installment of the fascist workshop will be heating, which is usually the primary component of power consumption in northern climates. If you take care of heating and cooking, the rest of the power needs can be met with a minimalistic electric system involving batteries and solar panels.

The easiest source of fuel for heating is undoubtedly wood, especially in the countryside. But conventional fireplaces have many disadvantages:

• They’re expensive and complex to install
• Hard to maintain, and dangerous in case of creosote build-up
• Lots of wood is required
• Fire needs constant maintenance
• The temperature will fluctuate wildly between too hot and too cold

But in the past decade, the DIY crowd has been working on a completely new type of wood heating system: the rocket mass heater. This is an adaptation of the great rocket stove system, developed by whites to help brown people in the third world. The rocket stove is a way to use high speed air currents to burn wood at high temperatures. The higher temperatures means the wood burns more efficiently and cleanly. This makes it great for cooking, especially indoors in mud huts.

The problem, of course, is that the rocket stove burns wood VERY quickly. Far too quickly to properly heat a space; you would have to start new fires every 30 minutes to keep the room temperature at a comfortable level. So how do we take advantage of the rocket stove’s high efficiency and clean burn, without having to constantly monitor and adjust the fire? Enter the rocket mass heater.

The basic concept is that instead of heating the air in the building, the rocket stove will heat a large, heavy mass, which will in turn slowly release it’s energy over time to keep the room temperature stable. This way, it doesn’t matter that the wood burns within a few minutes; temperature fluctuations will be kept minimal. Another advantage is that since the fire’s energy is stored inside the mass, an air leak will not immediately require additional heating to restore the ambient temperature.

Materials

You can’t just buy a rocket mass heater system; the only way to get it is to make it yourself. But the good news is that doing so is accessible to the average bad goy, both in terms of money and skill requirements. The materials necessary are as follows:

• Chimney piping
• Steel drum (a used oil drum will do)
• Fire-resistant bricks
• Cement for the bricks
• Source of mass (cob will do fine here!)
• Insulation (for the combustion chamber)

As always, you should try to get these materials for free (look for classified ads giving away free bricks, or demolition sites throwing away bricks and piping). With a little bit of searching you should be able to get the necessary materials for next to nothing.

Concept

The rocket mass heater has several special features that distinguish it from a conventional stove or fireplace. Let’s look at them in turn.

First, the rocket stove has a pipe for a fuel intake system, situated at the bottom of the stove. This is unlike a normal stove, in which you just put logs in the combustion chamber. Instead, you put smaller sticks in the fuel intake pipe, and only the tips will burn in the combustion chamber. As the sticks burn, they slide downwards until all the fuel is consumed.

Second, the gases and smoke from the combustion chamber don’t escape directly through the chimney and outside, but are instead trapped in the steel drum. This means that no hot air is lost through the chimney, but instead is radiated through the steel drum. Also, the trapped gases and particles are eventually burned as well in the high temperature, which increases the stove’s fuel efficiency.

Third, once the air leaves the steel drum through the output pipe at the bottom of the drum, it doesn’t go straight outside (which would also waste heat) but instead the chimney is embedded in a mass of cob, concrete or bricks, which absorbs any remaining heat before the chimney leaves the house.

Fourth, several aspects of the design are tweaked to maximize the air-flow inside the combustion chamber. There is an air intake vent, typically near the floor (where the air is coldest). The chimney above the combustion chamber is insulated to increase the temperature of the air. By increasing the temperature difference, a stronger air-flow is generated, which makes the fire burn hotter. As a result of this cycle, the rocket stove burns at much higher temperatures than a conventional stove.

Alternate uses

Being a very high efficiency system, the rocket stove can be put to different uses. As we’ve seen, the most obvious uses are for room heating and cooking. These require little further explanation.

The rocket stove can be connected to a Stirling engine to generate quiet and safe electric power. The Stirling engine, unlike a steam engine which isn’t closely monitored, won’t explode.

It’s also possible to heat a water tank with the rocket stove, providing hot water without having a electric water heater. However, any kind of hot water tank system is somewhat inefficient. Better to use a on-demand water heater using propane or electricity, which insures that only the required water is heated. But if propane and electricity are a rare resource, the rocket stove water heater is a great idea.

A clever builder can create a central stove which serves a variety of different purposes, by connecting the combustion chamber to several different appliances by a system of pipes. Levers could redirect the hot air from one appliance to another.

Conclusion

The rocket stove is a versatile concept that can really make our lives easier if we’re operating independently from the system’s resources. And being cheap and simple to make ourselves, it becomes a key component of our infrastructure.

As with anything, of course, it does have drawbacks. If you’re in a urban environment, access to free fuel will be limited, unlike in the countryside where dead trees, fallen branches and agricultural waste can be acquired without great effort. If you use it as your main cooking system, you’ll forego the convenience of modern gas or electric stoves.

If you decide to build your own rocket stove, there will probably be people in your area who can coach you about it. Otherwise, make sure to read up on the finer details and watch some of the many videos available on the subject.