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!
In a country like Romania it is not unheard of to live on a property of land that has running water – so we’ve put that on our wishlist. In such cases hydro-electricity can be a very appealing source of electricity (though I have asked myself what would happen in case of freezing). With that in mind have a look at this interesting invention – the hydro-electric-barrel:
Though living off-the-grid is tempting it probably isn’t as ecological as you may think it is. Electricity is an infrastructure that is best provided through collaborative systems instead of independent ones. It is unfortunate that so much of it is generated with an unnecessarily high ecological price – which is good enough reason to want to do it better on your own.
Being off the grid isn’t necessarily a smart financial choice either (at the present) because a completely independent system is still so expensive that it may never really repay itself (taking into consideration your level of consumption and price of grid electricity). Living off-the-grid is morally better but necessarily financially better.
Step 1: On The Grid
There are enough challenges and expenses when building a new house. Getting off-the-grid doesn’t need to be a top priority. If you are building a home and can connect to the grid then consider starting connected to the grid. You can design your home so that eventually it may be completely off-the-grid but you don’t need to implement it right away. You can designate places for photovoltaic panels, for wires, for batteries, converters, etc. but you don’t have to install them right from the start.
If, like us, you are building your own home then you will need a reliable source of electricity during construction. If you don’t have a grid-connection then you may need to bring a generator on site instead.
Step2: Self Generated
The next step, when you are ready for it is to start generating your own electricity. You should start with the natural resource that is most available to you. In the area of Cluj the leading sources are probably sun and water (if you’ve got running water on your property with enough altitude difference to generate the needed flow). If you are living in the mountains you may also have wind power available to you, yet it seems that commercial wind-powered generators are prohibitively expensive. In addition to the generating source (such as solar panels) you will need converters to convert and regulate your source current into 120v so it is compatible with all of your existing appliances.
It’s comfortable to do this while still connected to the grid because your self-generated electricity is backed- by the grid electricity (though you will need a grid-tie system to connect to the grid). If, for example, you rely on solar power then on cloudy days you still have all the power you need from the grid. If you generate more electricity then you consume then there is a good chance that your electric company will buy it from you. So in the end you may still be benefiting from grid-electricity but your bill will be zero or the electric company may pay you.
An efficient electric generating system and a low consumption home can generate a monthly revenue for you – so you may want to consider staying in this configuration and not going off the grid.
Step3: Off The Grid
To go completely off the grid you need to add to your electrical system a battery array. Batteries store energy when it is generated and make it available when it isn’t. If, for example, you rely on solar power then you will need batteries to supply you with electricity during the night when your solar panels are not providing you with electricity. Good batteries (that will work for 20 years) are initially very expensive to install. You may need additional converters to integrate them into your system and you need to be careful and monitor their use when your sources are not generating electricity (more on that in a separate post).
When you go off the grid you are completely on your own so regardless of any expenses (and potential losses) involved in doing so, make sure you are ready to be on your own (for example, in our house we are planning heating and hot-water systems that can operate at least basically when there is a power-out).
We want to have a really pleasantly warm house when it gets cold outside. Building with hemp insures that we enjoy a wonderfully insulated home. Now we need to deal with heat – which includes both environmental heating and water heating.
In typically built houses which tend to be cold when it gets cold outside it’s more a brute force challenge. With an ecological house it is actually more complicated because it’s easy to design a system that overheats the house. We still don’t have a clear picture or understanding of our heating needs – though we are working at it.
In the meantime I wanted to share with you some great resources that we are using to educate ourselves:
- Stoves Online (UK) – it s great resource for learning about the different elements that make up a heating system with a very rich offering of solutions if you happen to live in the UK.
- Boiler Stoves (UK) – seems like a sister website which specifically explains how boiler stoves work and can be incorporated into a smart and efficient heating system.
- Radiant Design Institute – though not an appealing website has a lot of really well-grounded and useful information I believe can be very useful especially to do-it-yourselfers.
You may also want to visit these two pages:
IMPORTANT: this note was added after the post was published but seemed important enough to be inserted at the beginning of the post. I am just now realizing that my perception of heating requirements are based on experience of poorly insulated homes. This is why I expect stoves to be lit numerous times a day. But, in a properly insulated home the need for heating should eb drastically reduced. If this is true – then all our elaborate plans to use stove-heating may be irrelevant – since the stoves may not be lit long enough to generate hot water. Having a super-energy-efficient home may lead to us to simpler, existing ready-made solutions. We don’t know, and we don’t know yet someone who knows … so for the time being it’s all up in the air.
Some weeks ago we described an imaginary-heating system and since then we’ve come across numerous resources and refined our understanding a bit.
I think there are two core ideas that shape and guide our understanding and wishes of a heating system:
- Most of the time we can shower when hot water is available – though it’s comfortable we don’t really need hot water to be available on demand.
- Enough direct heat is generated by our wood-stoves to indirectly supply most if not all of our heating needs.
So what we can say about our envisioned heating system?
- It will be an integrated water-based system – the same systems is used to generated running hot water and water for a radiant heat system.
- The system relies as little as possible on electricity – we would like to have a warm house and hot water even during a complete power-out (though it may run better when powered with electricity).
- The system will include an indoor cold-water container that will bring the water to room temperature.
- The system will include a central hot-water tank (not a boiler!) that supplies both the radiant heat water and flowing hot water to facuets and showers.
- The primary source of heat will be classic Romanian-village-style terracotta wood stoves. We expect to have one or two primary stoves in the living-space and kitchen. We both work from home a lot and cook a lot so these stoves will already be working.
- We would like to design and build the wood stoves to include an efficient coiled water pipe that is connected to the radiant heat water circuit and feeds back into the central hot-water tank.
- We would like to install a on-demand gas water heater on the running water hot-water circuit as a backup in case the water in the hot-water tank is not yet hot enough.
Following are someuseful web-resources:
- Some basic explanations about boiler-stoves
- Design Constraints for Water Central Heating Systems
- Sample (Do-It-Yourself) Central Heating Design
- Collection of posts on radiant heating at RadiantDesignInstitute
- Romanian forum thread with images on a self-made heating circuit