Himalayan Rocket Stove Update July 2017
It has been an interesting, intense and exciting journey so far. I say that almost every time I sit down to write an update, but it seems especially so now, just as we are about to launch into production for the new batch box design of the stove.
Since the last update when I was here in India in April, I came to the conclusion that our first design was good, but could be improved. So Tanzin and I went back to the drawing board with a determination to incorporate the feedback we had received from the various stove users who had been testing our first version in the field over the winter months. The 2 main points were size of wood to be used, and height of the cooking surface.
We needed to make it lower, and we needed a whole new wood feed system that would allow for larger pieces of wood to be used. The latter point sounds contradictory as the whole purpose is to reduce the need for large wood fuel consumption, but the issue I realised as I walked around the villages is that they have already cut their wood for the next few years, and they don’t want to have to turn their logs into splinters just to use it up.
The number one objective when introducing a new concept into people’s homes is to make it user friendly with minimal adaptation, otherwise it will simply not get used. With all that in mind, we came up with our version of a batch box design for the rocket stove (this means it has a door that opens and the user puts their wood inside a box to be combusted). It still needed to meet our other criteria which is clean combustion and high efficiency.
To achieve all that, we had to get a bit more technical than our earlier design and so now we have incorporated clever airflow systems that preheat the air prior to entering the combustion chamber, and preheating the secondary air that injects directly into the rocket tube. This keeps the temperatures high and makes for a very stable, highly efficient and clean combustion that exceeds even our expectations.
We are very happy with the result, as this new design also allows for several other new design features. Low cooking surface at the front for making chapatis (flat bread) with a slightly higher section for general cooking directly over the rocket tube. We also incorporated a valve on the exhaust flow that allows the user to regulate the heat output into the room, so if they are using in the warmer months for cooking, they can reduce the heat output into the room. Additionally, we are working on a movable hot water box that will simply sit on the top front section. This will hold approx. 12 L to be heated and then moved to wherever hot water is needed such as the kitchen or the bathroom. This hot water box will also store up to 1kWh of heat energy that can be used as an additional heater in other rooms… such as the bedroom to take the chill off the air before going to bed.
Another innovation we are working on is a pellet feeder system to be added as an optional extra to the basic stove. In combination with a side project to set up micro-enterprises in various regions making pellets, this will allow the stove to run on waste biomass in a highly efficient format. Pellets are an ideal fuel source and we are now in the process of researching the viability of making and distributing pellets using various forms of waste material such as carpentry waste, apple prunings, rice husks, etc.
More options are coming, but this is an indication of what is on our plate at the moment. This coming month will see the first batch of these stoves come out of the new CNC factory we are working with in Baddi, and of course we will post photos and updates on social media as this process unfolds.
Stay tuned… exciting times!