Steam Dreams

I’m in the process of designing a simple 3kW steam engine for both a combined heat-and-power gasifier system and our solar power generator system. I can’t help but think about the future possibility of small-scale steam power for both stationary and mobile steam power applications.

In absence of a really suitable open source 3D CAD program, I downloaded a free trial version of Alibre Design Xpress 3D solid modeling software – to do a basic 3D model of the engine we’re building, for which we have a $250 bill of materials:

The basic concept is – as mentioned in a previous post – a high performance modern steam engine of 20% efficiency can be made without much technical difficulty. Remember that our present solar turbine design requires only 5% efficiency to become feasible.

Moreover, a simple direct coupling of the steam engine to a linear hydraulic pump

means that you have a super-simple hydraulic power source for devices like our open source tractor, LifeTrac. This brings LifeTrac much closer to the reality of being powered by high performance, modern steam – via local production. As such, LifeTrac would become integrated into the local agricultural ecology – capable of being powered by a gasifier or pyrolysis oil from local biomass.

Now I’m busy on the standard steam engine of the 3D drawing above – so if you want to see the latter hydraulic pump hybrid come to reality sooner rather than later – contact us right now and let’s start talking about fabrication. By the way, there is a resurgence of interest in such hydraulic drive in the mainstream economy.

Stationary Power:

Stationary biomass power in most temperate areas has a lot of potential and can be quite sustainable if done properly. In particular I am attracted to the idea of developing a fully integrated gasifier, flash boiler, steam electrical generator. The design could be broken done into three different processes.

  1. Combustion: Combustion would be done in a two-stage process known as gasification. In the first stage a minimal amount of air and heat are combined to generate wood gas, in the second stage a full amount of air is delivered and combustion is completed. This process is cleaner and has the added benefit of generating a char that is much higher in carbon an is claimed to be highly beneficial for soil.
  2. Steam Generation: The next stage is where heat is transferred from combustion to the flash boiler. Here the hot portion of the flame is in close proximity to the end of the monotube flash boiler and produces high temp steam. As the combustion air is driven up and out it passes over the incoming tubes and warms the water before it is heated into steam.
  3. Steam Power conversion: The last main process occurs in the steam engine, here the steam is expanded against a cylinder which is driving a generator AC or DC or else doing mechanical work. The steam is then exhausted into the condenser. The condenser is also a large 500-1000gallon thermal storage tank for hot water and space heat. Finally the condensed steam is pump as water back into the monotube flash boiler to go through another cycle.

Here is a diagram of the process I am proposing.

In summary with the cogeneration of electricity or mechanical work and heat all energy from the biomass is used. Additionally the clean combustion process produces little to no emissions typical of biomass combustion and furthermore even produces a very useful agricultural component known as biochar.

Mobile Applications:

For mobile applications I believe steam may also be due for a renaissance. It is well documented that 1920 steam engine vehicles often beat their gas counterparts in emissions, acceleration, and equaled them on fuel economy. Much less known is that they also were the first vehicle to be driven off of solar thermal energy. In 1915 an inventive Dr. Robert McEleroy used a tank of refinery byproduct to store heat at 900 degrees, from a heat exchanger he was able to produce steam to travel up to 35 miles with his vehicle. So steam does have an interesting vehicle power history, particularly before well refined petrol products arrived (a condition necessary for the internal combustion engine to survive).

So here is an idea I would like to bounce off all creative minds out there. Right now hydraulic hybrid vehicles are receiving a lot of attention as efficient drivetrain choices. One advantage is that the pump can be tuned backwards against a high-pressure accumulator for regenerative braking additionally there is no longer a need for a transmission. So given the advantages of hydraulic drivelines in vehicles and machinery why not design a free piston steam hydraulic pump. In concept it might look like this.

The concept would be quite simple; steam is expanded against a hydraulic cylinder which stores energy in a high pressure accumulator. As the steam loses pressure due to expansion the hydraulic cylinder forces slow the cylinder, by the time the steam cylinder uncovers the exhaust port the steam cylinder is nearly stopped and the pressure on the hydraulic cylinder accelerates the steam cylinder back towards the steam inlet port. Steam is then admitted by either an electronic solenoid valve or a mechanical valve and the cycle starts again. There would also need to be two check valves arranged as shown in the diagram to allow the hydraulic fluid to enter the cylinder from the low-pressure accumulator and also to provide a route back for hydraulic fluid on the compression stroke.

If this simple engine proves itself in concept it seems like a potentially ideal candidate for mobile hydraulic applications both on and off road. It would be mechanically simple, capable of storing some energy for intermittent power bursts (acceleration, initial pulling efforts, ect) and because of lack of crank and block it would have a very high power to weight ratio. Mobile steam power for the 21st century? We’ll see….


  1. Evil Rocks

    What happened to using a Boundary Layer Turbine?



    we scrapped it. We would revisit if you can show me any single documented, replicable Tesla turbine with a longevity record and mechanical efficiency at least half that of the 90% steam engine efficiency. Please read supporting information regarding performance of the Tesla turbine:

    for reasons why the steam engine meets required performance specifications, and why the Tesla turbine doesn’t. It just doesn’t have the track record.

    The name Solar Turbine remains only for historical reasons in our project. We are really talking about a solar power generator system.

    The closest example was a 60% mechanical efficiency (from private conversation) claimed by

    and 30% is documented on that page. Moreover, no one has shown longevity in the Tesla turbine.

    Let me clarify that by no means do we have any final word on Tesla turbines – we have never built one. However, when there is a simple steam engine that has about 90% mechanical efficiency for turn-of-19th century examples, and a good track record – we move forward with that. – Marcin

  2. ram

    Has there ever been a closed loop steam system where the steam used for work is reused? I mean like a storage tank with water that is pumped to a flash boiler preferably then the steam recondensed in the storage tank and reused. This would save a lot of energy as the heat is not wasted. The construction of the “Thermal battery” case would be the most difficult part I presume. The tank construction and insulation would be a problem as the thermal fluid would also have to be replenished. This same “Thermal battery” can also be used for power generation at night when there is no sun. This technology is in my opinion the only thing that can either make or break solar power. Do you all have any plans of constructing Solar powered air conditioners and chillers? I mean the ones that use libr or ammonia.

  3. Mathew


    John Todd’s Prince Edward Island Ark had a thermal battery in the basement. Essentially, the basement was a huge pool, and during the summer they pumped water up to the solar thermal system and back into the tank. This massive thermal mass kept the whole house at a moderated temperature, and they didn’t need anything beyond solar to keep it heated, in the dead of winter, with wind whipping and temperatures of 30 below.

    Although no steam power was involved, it seems fairly trivial to add it in to such a system, if the building is built around the thermal battery.

    I’d like to see three stages of heat capture myself- solar-> steam power -> hot water -> thermal battery. I’m not sure how to handle all that water transfer, but If the battery is in the basement, everything could flow downwards slowly.

  4. ram

    Has there ever been a closed loop steam system where the steam used for work is reused? I mean like a storage tank with water that is pumped to a flash boiler preferably then the steam recondensed in the storage tank and reused. This would save a lot of energy as the heat is not wasted. The construction of the “Thermal battery” case would be the most difficult part I presume. The tank construction and insulation would be a problem as the thermal fluid would also have to be replenished. This same “Thermal battery” can also be used for power generation at night when there is no sun. This technology is in my opinion the only thing that can either make or break solar power. Do you all have any plans of constructing Solar powered air conditioners and chillers? I mean the ones that use lithium bromide or ammonia.

  5. Micah

    It seems to me that directly coupling an efficient steam engine or turbine to an electric drive train/in-wheel-motor system is going to be your best bet. Maybe someone out there could put out some open-source designs for modern lead-acid batteries. It shouldn’t be to hard to fabricate something like that with a fab-lab. Also allowing for an electric hybrid “in-series” drive train would mean that the tractor or car could be charged while not in use by solar which is better than burning fuel – even if the fuel is home grown.
    Just my two cents. Good luck with the designing and thanks for your work.

  6. Nick

    Matthew and Ram,
    If you look at the first diagram which is rather crudely drawn by myself you should be able to see that the the water is used in a closed cycle manner as it is condensed in a large tank and then fed into the boiler.

    You will also be able to see that the condensing tank is a thermal battery like both of you are proposing. Another heat exchanger placed in this thermal battery can pull heat for hot water, or other low temp heating purposes. Typically a system that produces both electricity and heat is known as cogeneration and as you both allude this method is more efficient and effectively uses up to 90% of the available fuel energy depending on boiler efficiency. In practice this is done rarely on large scale power systems. However one example I’m aware of is Denmark’s thermal plants, which provide both electricity and nearly all the cities heat by piping the waste heat from the condenser through the city. It has also been done on smaller scales for places like hospitals that produce their own electricity and heat. Due to the enormous size and remote location of our countries centralized power plants it is not practiced, as a result over 60% of fuel energy is put up the atmosphere or in the river. This is why a small scale cogen system that uses either sustainable biomass or solar is so important to develop. Also please note that although I discussed only biomass the steam engine is being developed just as much for our solar thermal system that is in the works. However I must say solar is simply not in the cards for everyone, solar insolation values for a given area pretty much determine your economics. Luckily cloudy wet areas that can’t do solar usually have more biomass growth to fall back on.

    Micah I agree with you that lead acid batteries should and could be produced on a small scale and already seem to play a big part in most off grid systems. I’m not however convinced that electric hybrid is the best way to go, what makes you prefer this method to hydraulic hybrid? Also how do you propose to charge the batteries with sunlight, through a PV panel or through another method?

  7. Mathew


    Other Hybrid Methods that might be useful:
    Steam/Pneumatic -there are already lots of pneumatic power tools available, would be good in a shop

    Also, the Amish already have many home made pneumatic tools (their shops are almost all pneumatic), and might be interested in cooperating on development. Despite common misconceptions, they are allowed to use computers for business, and might, just might be interested in Open Source development.

    An Aside on Co-Generation:

    I was in Sweden visiting with my girlfriend’s family this summer and saw (generally, but no details) that the Kosta Boda glassware company pipes the waste heat from their glass blowing into a heating system for a whole mall/shopping outlet. I asked after the system and was told that it is a legal requirement for factories in Sweden to incorporate waste heat into municipal steam heat systems, and when new factories are built they are constructed to tie into the grid.

    Marveling at this system back here in the USA, an architect friend of mine informed me that that is nothing new- New York, Boston, Chicago, and most other 19th century industrial towns traditionally tied co-generation systems into steam heat utilities.

    The power plants here in New York still do that- we have oil and LNG plants inside the city that provide steam heat across Manhattan, (70th st plant) sections of Downtown Brooklyn (through the Navy Yard oil plant), and I think some areas in Queens.

    Doing it on a small scale would be great, and a thermal battery tie-in would capture all the waste heat from warmer months also.

  8. Nick


    Yes pneumatic power would be quite useful in a shop. I’ve also read a little bit about London centrally producing and distributing hydraulic power for many years as an alternative to electrical. I’ll have to ask around some of the Amish I know to see if they have any interest.

    It is also interesting to hear about the Sweedish glass factory, from my brief visit of Scandanavia it seems that the generally are quite good about energy efficiency. I was just reading about their WWII experience were 90% of Sweedish vehicales ran off of wood gas and gasifiers, perhaps that experience shaped their highly conservative outlook?

    I guess i was aware that in large US cities their is some cogeneratrion done, but I’d venture to say that by far and away the majority of our electrical power is produced large distances away from the city so the majority of the condensed steam heat is wasted, simply because there is no way to use it. I’m not saying our power companies our bad for this, just that we have a really spread out country and population when compared with say European countries were cogeneration tends to be more practical.

  9. ram

    Hi Nick yes it is a closed loop steam system brilliant :). Have you all tried evacuated heat pipes for steam production?

  10. Micah

    The reason why I see electric hybrid as superior to hydraulic hybrid has to do with efficiency (in terms of labor, maintenance, and system integration). An electric hybrid system could be integrated into the electrical system powered by the solar concentrator. Converting electricity generated by the solar boiler into mechanical work would be much less labor intensive than making fuel. Also, as I see it, electric cars are going to become more and more mainstream in the future. This means that if we are able to build electric hybrid systems we will be able to take advantage of the future electric charging stations when it is necessary to travel long distances. Also I suspect that in the future it will become easier for us to develop more efficient means of storing electrical energy – whether through ultra-super capacitors or various kinds of fuel cells. If these kinds of technologies can be produced locally through open source design then powering everything off of electric will become a no-brainer (in my opinion). Of course this does not negate the value of a hydraulic system by any means. It may be the case for now that simpler is better. In any case developing multiple ways of doing things can only serve to further empower the move toward human liberation.

    On another note I have a suggestion about steam engine design and fuel. You may want to consider also developing a steam engine that is designed to run on hydrogen. I once looked into this and came up with a very interesting (though rudimentary) design. The engine is known as a quasi-turbine steam engine. This engine takes advantage of both external and internal combustion. Essentially a hydrogen fueled pulse jet is mated with a Wankel engine. The burn in the pulse jet is kept stoichiometric lean. The result is when the hydrogen and oxygen disassociate under compression in the Wankel engine the excess o2 allows for a secondary internal combustion. The exhausted steam could then be used in an endothermic reaction to produce more hydrogen (an example being aluminum oxidation and in this case the aluminum can then be reclaimed through electrolysis from the aluminum oxide).
    Understandably this engine is probably too complex for our purposes at this time but even if we just developed a hydrogen pulse jet that could run a simple turbine for a generator in an electric hybrid vehicle this might be worth while. The advantages being that you eliminate the complexity of having a boiler and all that mess. Also a solar concentrator could be set up full time for the creation of hydrogen as fuel for a steam engine (and maybe in the future an open source fuel cell). Just something to think about. God speed.

  11. Abe

    Good 3D work, guys. I have a question about the steam engine – why? After looking at your proposed design for converting biomass into mechanical energy, it seems that a steam engine isn’t the most efficient or cheapest solution here. Why did you choose that component in the above system.

    I may be missing something here, but if you are using a gasifier, why not just burn the gasses in an ICE? the ICE has a higher efficiency than a steam engine, is readily available all over the world, has available parts and knowledgeable technicians. It seems like it would be a better fit. Your steam engine in this situation is looking at 15%-25% efficiency as that component, but an ICE has 20%-30% in this sort of application (with liquid cooling, even higher efficiencies, up to maybe 35%).

    I can get a 5 HP ICE for $300 online, and it is ready made, ready to go. What am I missing here?

    The choice of the gasifier is a great idea. Have you seen the gasifier kits at:

    Also, what about a hydraulic accumulator for energy storage for the home, instead of batteries. Sure, the efficiency is not as high, but it is cheaper to maintain and would last longer. Pump up the accumulator with an ICE/gasifier combo or the Solar thermal engine, then have a hydraulic motor coupled to an alternator/generator for on demand uses or to keep a smaller bank of batteries charged. Anyone know of this being used?

    Abe, what you say is true for _existing_ steam engines. We aim to build _open source steam engines_ at Factor e, such that the cost is lower. This allows us to operate on biomass, biomass gasification, or oil -or any fuel for that matter. Steam engines also have a 10-fold larger lifetime compared to standard internal combustion engines. Plus, we are interested in local production, such that any community can produce steam engines. Furthermore, the steam engine is applicable to the solar thermal electric generator as the heat engine of choice. On top of that, linear steam enginge-hydraulic pumps can be a high-efficiency solution to generating hydraulic fluid power – such as for powering LifeTrac, or hydraulic hybrid cars. These reasons should make it clear, from an ecological technology perspective, as to why we’re choosing the steam solution. Add the possibility of hydraulic accumulator storage, and we may be talking of possible applications to solar energy storage with the solar generator package. The hydraulic accumulator is a new concept to me at least – we should pursue this topic to figure out suitability for renewable energy storage. – Marcin

  12. ram

    Have you all thought about an organic rankine cycle engine? It would be really useful for low temperature power generation.

  13. Nick

    Thanks for further explaining your preference of electric hybrid vehicles. You may very well be right, but it does all seem to boil down to how well we are able to store electricty. Right now it doesn’t seem like battery technology has progressed that far nor does it seem efficient to generate and store hydrogen and then convert back to electricty in a fuel cell, but who knows what innovation will bring. Every time I consider the whole transportation problem I am amazed at how simple and energy dense liquid fuels are, too bad for the CO2 and lack of supply. Really though it makes me think even in a world without fossil liquid fuels that we still may be using some bio liquid fuel simply because of the high energy density per volume.

    You bring up good points, I’ve pondered over your point about overall efficiencies for a while and am glad this part of the dsicussion is brought up online.

    Here are a few points that steered us away from a gasifier ICE route.

    -Fuel Flexibility: All literature I have read (particularly “Handbook of Biomass Downdraft Gasifier Engine Systems” by Thomas Reed) states in no uncertain terms that to run an ICE succesfuly on a gasifer it must be designed for that specific uniform fuel source. Different woods at different moistures all vary in performance enough that you really must have the gasifier and clanup zoned in for that fuel. This would seem to make the technology somewhat challenging for entry level users like ourselves. Were in a boiler we can have less than perfect gas cleanup and combustion and still run well.

    -ICE Complexity: If we stick with conventional ICE engines we are stuck also with a pretty high level of complexity wich again limits access to entry level users across the globe. Even simple carb ICE engines or diesels require machining capabilities that are out of reach for us at present:

    -Ability to accept different heat Inputs: this is really the main point of using a steam engine. We intend to utilize solar thermal energy whereve applicable and only use the biomass as a supplement. To do this we need a thermal engine that can accept heat inputs from both solar and combusted fuel. The water Rankine cycle is a simple way of doing this and the steam engine is the simplest Rankine engine.

    I’m with you 100% about needing to achieve high efficiencies. Cogeneration goes a long way in helping out the low electrical efficiencies of this setup, but what about applications that really have no use for waste heat?

    I’m also leaning towards the idea of a hydraulic accumulator for cheap robust small storage. However the energy densities are noweher near on par with batteries and off the shelf accumulators seem to cost quite a bit more. For example i saw 10 gallon new accumulators for $800 wich at 3500psi would store under 1kwh of power. However it would be pretty handy for welding so that you don’t need to run a 15kW generator when you only need that much power 1/5 off the time you are welding.

  14. Abe

    I am not sure I agree that running an ICE on wood gas would be difficult for a beginner. Thousands of vehicles world wide have been converted by beginners, not professionals. But what we are talking about here is small engines for home energy production, which is well within the reach of a DIYer. The GEK guys seem to really illustrate that point, and they even offer kits.

    I do agree on the other points, but I don’t know that they are really relevant. First of all, complexity is about the same, especially when you talk about higher efficiency steam engines. A 4 cycle engine from a generator is pretty basic, and fairly efficient, readily available. I just bought a Honda 8 HP for my welder for $400, including shipping. I can get parts locally and basically keep the thing running for years. I don’t have to machine anything, no do I have to melt metal or deal with steam. I can just make a gasifier and go!

    I can get a 3Kw ICE/generator for under $300. I don’t think you would be able to make the steam system for that, including the generator.

    So, I think it is a matter of economics as well as efficiencies.

    Another question – how hard would it to be to copy an ICE? Just cast the parts and go, like India does with the Lister Diesels. Again, you get the benefit of starting with something that works without having to develop everything from scratch.

  15. elliot

    I was concerned about the issues involved in corrosion of the engine block when made from cast iron, and the problems involved with oil to prevent it. It just occurred to me that small steam engines with corrosion problems existed before aluminum became widely available. Today, many engine blocks are made of aluminum anyways.

    Aluminum bores can be coated in a nickel/silicon carbide protective layer that i think fairs decently against steam corrosion. The bores can be replated and remachined as maintenance requires, jjust as in modern internal combustion engines. Nikasil is such a product that is widely used.

    I discovered this while reading about other topics, and thought I’d mention it here for future benefit.

  16. Marcin

    Elliot, Please cite your reference on the aluminum vs steel. Do you know anything about how easy it is to apply Nikasil?

  17. Bob Fairchild

    TinyTech Steam Plants India:

    Mike Brown Steam Engines:

    Small Vertical Fire Tube Boilers:

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