Comparing gassification with steam

Garry Hoddinott wrote:My need is a modest output energy system. My beef with solar is batteries. They are too short lived to be sustainable and just a bit toxic (am interested in capacitor banks).

My property (which I wish to share (grafton NSW Australia)) has ample wood supply - stored solar! What is the best way to convert that to electricity? Gassification seems do-able, but steam??? We don't hear too much about steam. Is it really just too hard?

I met a wonderful old guy in Australia who told me of his dad's very large hot air machine. Umm - his hand guestures indicated it was bedroom sized and used 2 chimneys as monster pistons, and used a very large flywheel. Seems like it turned a crankshaft and powered a stationary sawmill and ran on sawdust from the mill itself.

That sounds funky - any thoughts???

Garry Hoddinott wrote:My need is a modest output energy system. My beef with solar is batteries. They are too short lived to be sustainable and just a bit toxic (am interested in capacitor banks).

My property (which I wish to share (grafton NSW Australia)) has ample wood supply - stored solar! What is the best way to convert that to electricity? Gassification seems do-able, but steam??? We don't hear too much about steam. Is it really just too hard?

I met a wonderful old guy in Australia who told me of his dad's very large hot air machine. Umm - his hand guestures indicated it was bedroom sized and used 2 chimneys as monster pistons, and used a very large flywheel. Seems like it turned a crankshaft and powered a stationary sawmill and ran on sawdust from the mill itself.

That sounds funky - any thoughts???

Len Ovens wrote:Steam? The main thing is that it requires some study to build/operate/maintain, may require certification to run and annual inspection to be legal. I expect they are not quite as dangerous as some people make them out to be, but enough drunks got themselves and worse others killed with lack of care. If they could be used as tractors on the farm, it must be possible to have them be reasonably safe.

Marcos Buenijo wrote:

Len Ovens wrote: may require certification to run and annual inspection to be legal.

For micro scale combined heat and power, a low power system that sustains output for long periods and within a narrow operating range would be ideal. Under these conditions, a simple monotube steam generator would be perfect. These can be perfectly safe, and they require no certifications as far as I'm aware.

Len Ovens wrote:I have heard some states require the boiler to be inspected annually. I got the idea it was any boiler that was for holding steam. Looking at some pictures of monotube steam generators it does seem like it could be safer... at least there is a lot less water/steam in the system at any one time. Both rocket burner and gasifier burner can be kept pretty constant, I would think.

So where do I get one? from your comment above I get the idea many of the parts are not obtainable right now.

Len Ovens wrote:I still don't know that I would want to run it 24/7, but daily during heating season would change battery size needed or maybe allow super caps to fill the night time lighting/entertainment void.... or maybe this would be something to run overnight and let solar panels with a cap bank deal with daytime.

Marcos Buenijo wrote:
You would have to make your own steam generator. This is not a serious difficulty for a low power engine. A small unit suitable for powering a one hp steam engine can be had from 50 feet of 1/4" steel tubing.

A unit suitable for an efficient one hp engine could be little more than a simple coil, just have to made sure the very hot furnace exhaust gases make good contact with the tubes for good heat transfer.

Garry Hoddinott wrote:My need is a modest output energy system. My beef with solar is batteries. They are too short lived to be sustainable and just a bit toxic (am interested in capacitor banks).

My property (which I wish to share (grafton NSW Australia)) has ample wood supply - stored solar! What is the best way to convert that to electricity? Gassification seems do-able, but steam??? We don't hear too much about steam. Is it really just too hard?

I met a wonderful old guy in Australia who told me of his dad's very large hot air machine. Umm - his hand guestures indicated it was bedroom sized and used 2 chimneys as monster pistons, and used a very large flywheel. Seems like it turned a crankshaft and powered a stationary sawmill and ran on sawdust from the mill itself.

That sounds funky - any thoughts???


Hello Gary,

Any piston engine single or multi cylinder easily coverts to steam. A steam pipe goes to the intake port, the rest is left alone. Steam needs be supplied by a boiler, it requires a boiler fill pump, this can be attached to the engine shaft, before the generator is mounted.

Steam is the last energy you should be contemplating, it has huge heat needs for very little energy. My preference is CO2 its active at -40*C , at +50^C it has the same energy of steam at +600*C. +30C will provide all household needs and more, and working on 1 litre per second so the device is very small.

Almost same setup as steam, hot CO2 goes to the intake port, hot CO2 comes out the exhaust manifold into a drum where the CO2 is allowed to cool before being pumped into the heater/boiler.

Len Ovens wrote:Like brake tubing?

My first thought is that the steam would be just as likely to push the water back out the input as into the engine. I am guessing there would need to be at least some kind of injector? Would a simple ball valve work for that? (fluid diode) have the steam pulse in time with the piston, or would the pressure need to be continuous? (and need continuous injection)

I am also assuming a piston engine as compared to a turbine? Single stage? Two stage? Double acting I would guess. Would a hydraulic cylinder work? I am guessing that HP would depend on steam pressure/flow as well as engine size (bore and stroke).

Just found some stuff to read.... more questions when I am done.

Peter Mckinlay wrote:Any piston engine single or multi cylinder easily coverts to steam. A steam pipe goes to the intake port, the rest is left alone.

Steam is the last energy you should be contemplating, it has huge heat needs for very little energy. My preference is CO2 its active at -40*C , at +50^C it has the same energy of steam at +600*C. +30C will provide all household needs and more, and working on 1 litre per second so the device is very small.

Almost same setup as steam, hot CO2 goes to the intake port, hot CO2 comes out the exhaust manifold into a drum where the CO2 is allowed to cool before being pumped into the heater/boiler.

Marcos Buenijo wrote:

See https://archive.org/stream/steamengineprinc00crofrich#page/n0/mode/1up

Brake tubing will work and has been used before in some projects. Steel tubing of all sizes can be had cheaply. You need a check valve (i.e. "ball valve" as you mentioned) on the pump discharge to prevent back flow. The simplest pump for this application is a small plunger or small piston pump (see Hypro brand). You could make this also fairly simply... you need a sealed plunger that reciprocates in the end of a small tube or pipe section with check valves at the end (one to take in water from the collection tank, and one to expel water to the steam generator), and this can be driven by the engine shaft. There are small check valves with compression fittings designed for use with small tubing. The pressure will vary slightly as the pump operates, but the volume of the steam generator and action of the expander (i.e. engine) will keep pressure within a narrow range. You may also require a bypass valve on the pump to set steam generator pressure - generally a relief valve is used, but a small needle valve might serve as a means to set the desired pressure. This can be useful to prevent flooding the steam generator coil. I think you'll find that the most difficult part of this prospect will be feeding water to the steam generator coil at the proper rate. A solution can be had in using a larger steam generator coil and keeping a tight system and low water mass so that most of the water in the system is stored in the coil at all times. Also, a long steam generator coil positioned for good heat transfer can serve to heat excessive water pumped into the coil so that the pressure rises above the limit set by the relief valve on the pump discharge - this will send excess water back to the pump suction and limit the feed rate - a hot furnace operating at a controlled rate will then superheat the steam that is now set at a constant pressure by the relief valve on the pump discharge. This could work well as long as the engine were set for a constant rate and the furnace output were constant. Things get difficult when one desires a highly variable load, and I don't want to even consider it even though I know what's required.

Do not consider a steam turbine for micro scale applications. Very small steam turbines require ridiculously high speeds to see any appreciable efficiency, and even then they won't meet the efficiency of a good piston steam engine. There is also the problem of having to gear down the high speed provided by a turbine. A piston engine is the only way to go for micro scale (meaning less than 10 hp).

Good thinking - a hydraulic cylinder will work and has in fact been done before. However, the seals in the hydraulic cylinder are not useful for the project and would have to be replaced. Other projects have converted piston air compressors successfully. Generally, converting a gas engine to a steam engine will not result in a good system because internal combustion engines are designed to radiate heat for cooling, and the steam engine must be highly insulated for good results. It can be done, but select a design that can be properly modified (see White Cliffs steam engine for the best example of an engine conversion I've seen: http://www.rossen.ch/solar/wcengine.html).

Personally, I think there is promise in converting a hydraulic cylinder by replacing the piston seals (normally butyl or other high temperature rubbers) with high temperature compression packing like teflon or graphite. In particular, I think the graphite packing can be used successfully, and both have been used in model steam engines with high success. I have not seen them used for larger engines that generate useful power. In my opinion, an engine that operates at a low speed could use this kind of piston sealing with high success as long as a crosshead were provided to prevent all piston side loading. Best of all, a tight system that fully contained the water and steam (condensing for reuse) and prevented all air from entering the system could get away with no oil lubrication under these conditions as there would be no metal to metal contact, just have to keep all oxygen out to prevent corrosion.

Double acting could be done if a hydraulic cylinder were used. A single long piston valve might be used to control intake and exhaust for both ports, and the piston could be driven by a single eccentric off the engine shaft - or, poppet valves might be used with uniflow exhaust in the center of the cylinder for both pistons (actually, just a single large piston would be used - I considered this seriously once with a 4" bore hydraulic cylinder by connecting two pistons together in an 8" cylinder with a 4.5" stroke - the large 1.5" dia. piston rod was to be replaced with a much smaller rod and the cylinder end converted to a packing gland for the new piston rod - the rod was to be connected to a crosshead, and used to drive a large flywheel at low speeds on the order of 2-3 hertz - a single port in the bottom of the horizontal cylinder would have provided exhaust to the condenser). There are all kinds of possibilities... even multiple stages (compounding) can be done, and I've considered several unique configurations here.

I tend to emphasize a continual low output at low speeds to simplify the system, extend life, and make things easy to repair and/or cheap to replace when any problems arise. This could also minimize the required energy storage (i.e. battery). Really, this is the main reason I think small scale steam can be useful - if a low speed engine can be made to operate at low power for long periods, and be reliable and easily repaired, and fueled by biomass with little processing, then this seems ideal to me. Throw in the high quality heat from the steam exhaust and it seems like a winner. The main problem beyond getting a reliable system is getting sufficiently high thermal efficiency to make the system worthwhile.

Len Ovens wrote:Thank you. I understand the theory quite well, but that gives much of the practical information I lack.

Len Ovens wrote:Yes check valve was the word I was looking for I had thought a variable stroke pump might work well as an injection pump, run off of a cam (simple eccentric) rather than a crank. The cylinder body could be moved to adjust the water flow and could be manually pumped to prime the steam generator, or moved to an off position. A spring would provide the pump suction. The load should be constant as you say. Changes in speed or load would need to be manually supervised. I am thinking a capacitor buffer to provide motor start peaks and such. With a continuous run application a battery bank could be dispensed with.

Len Ovens wrote:I think if I had a lister(oid) I would use it as is. The amount of work to convert seems as high as a new build and the control and starting seems less than reliable in the long run. Also, lubrication seems more involved. It is certainly not simple.

Len Ovens wrote:The hydraulic cylinder seems more promising. I do not have a machine shop beyond a good drill press, so the more expensive off the shelf parts method is for me... though I would be quite happy to acquire a lathe and a mill. (a mill would be a learning experience in itself though as my machining experience did not progress that far)

Len Ovens wrote:This assumes the working cylinder is vertical. It seems to me a horizontal configuration would have gravity adding to wear on one side of the seals. Could the oxygen be purged by use of another gas? Or would water itself work? I am thinking that if the system is at rest, the cylinder needs to be empty and not filled with water. Or would the air be purged from the system at startup? through the condensing setup. A water reservoir with an open top I guess. How would the cylinder be filled with a room temperature gas at shutdown?

Len Ovens wrote:I am thinking single stage. It seems best to start simple. I would like to do stages, furnace first, then steam generator and finally the engine. With a single stage, the steam temperature could be lower too. Though a larger piston area would be needed I would guess. It is apparent that the HP rating comes from the steam generator in pressure/flow rate and the HP rating of the engine is the maximum it can handle from the steam generator.

Len Ovens wrote:This is the one thing that makes it less appealing to me. I have less of a need for extra heat than most people. Cooking, hot water, some space heating... maybe chilling if the energy is wasted otherwise. Then there is the moving of the heat from the steam shed to the house. I guess excess heat could be dumped directly to the ground under the house, heating that mass instead of trying to make everything face south.

Still more to think about and read.

Marcos Buenijo wrote:This might interest some - an automotive refrigerant compressor may provide air conditioning efficiently if operated at its most efficient speed (generally around 1000 rpm for piston units) and used to supply refrigerant directly to a fan coil unit much like is done in split ductless a/c units.

Len Ovens wrote:The added benefit is that these units have a clutch which could be used to keep the load on the engine more constant by dropping out when more electric power is required. I have not figured out how to tell which are piston units and which are not. All of the cutaway drawings seem to show piston units though, so I would guess they are most common. I don't know if buying used from wrecked cars is a good option or not but new ones are around $200. There seems to be no difference in getting rebuilt or new price wise.

R Scott wrote:Small scale steam could work, but getting a consistent supply of clean water is a problem. 1/4" lines will mineral up or leach away REALLY fast if your water chemistry is a little off. It is a FULL TIME job keeping a steam engine running--that is why they had engineers.

R Scott wrote:I almost ordered a powerpallet from All Power Labs. The reason I didn't get a gasifier was the fuel prep. I think the APL unit was close enough to what I needed (it is even better now) but the time/money I would have to invest into fuel prep was the deal breaker. If you have a continuous supply of biomass that only needs shovelling into the hopper, you can generate for less than the cost of battery maintenance on a solar system. If you have to process the fuel at all, your costs climb really fast.

Marcos Buenijo wrote:This is a very good site for learning about steam power: www.kimmelsteam.com

Len Ovens wrote:It seems to me even a gasifier would need some attention. How often would you see needing to "feed the fire". I would think twice a day would be pretty much the max to make it worthwhile for continuous running. How much unattended running could it do? How easy would it be to make sure it shut down gracefully? (In the case of fuel or water running out)

Buying pellets doesn't make sense (easy auto feed) nor does making pellets or some other easy to feed wood chips. Really I want to start with wood in the same way as a stove. (18inch long by 3 to 6 inch diam.)

Marcos Buenijo wrote:A few interesting videos I came upon:
...

Len Ovens wrote:That gave me some info on why the bash valves work so well. It seems a very small amount of steam injected is most efficient. I expect that this achieves much of what a multi-stage engine does with much less complexity. From the Kimmel page: This one from a compressor seems to be the most likely within my current ability. One of the other pages I saw suggested that in general the the heads will last longer than the compressor parts... but I am not sure. Doesn't matter though. There does not seem to be further info than what is on that page, but the concept is so simple that I can see how to do most of it anyway. The exhaust is very simple. I am not sure why they left the rest of the fins on between the exhaust and the head, I would think insulation would make more sense. I can guess what is inside the head too.

The updraft tube steam generators seem to be two coil parts, a bottom cylinder shaped coil that should have preheating water and a pancake shaped steam generator, though I have seen just the pancake part used too. When you say 50ft of 1/4in tubing, is that the preheat as well or just the pancake part?

Len Ovens wrote:
From the Kimmel page: This one from a compressor seems to be the most likely within my current ability. One of the other pages I saw suggested that in general the the heads will last longer than the compressor parts... but I am not sure. Doesn't matter though. There does not seem to be further info than what is on that page, but the concept is so simple that I can see how to do most of it anyway. The exhaust is very simple. I am not sure why they left the rest of the fins on between the exhaust and the head, I would think insulation would make more sense. I can guess what is inside the head too.

Marcos Buenijo wrote:
Also, I believe some conventional air compressor models are very good candidates for converting to a steam engine. Single stage units should make good bump valve conversions, but I also like the prospect of converting a good two stage unit to a compounded expander. I'm convinced such a unit can last a very long time at low speed while delivering useful power with modest steam pressures. There are very rugged cast iron two stage compressors available for reasonable pricing. One would have to fashion suitable valves (some form of poppet valve seems best). Compounding would provide an opportunity to place a reheat between the two cylinders, and this could provide high efficiency even at fairly low steam pressures. There is a problem of water collecting in the crankcase, so a means to separate this water is necessary (however, excellent insulation and superheated steam with a reheat stage might prevent this altogether). I am aware of the practice of placing a heat exchanger in the crank case heated with steam exhausted from the engine to evaporate water from the oil, and it was claimed to work well. A combination of heating oil in some way while keeping the crank case under vacuum should keep out all water. This means connecting the crankcase to a vacuum vessel that collects all steam blow by in the form of condensate - OR, the oil might be pumped to a small heated vacuum vessel for this separation to take place. I have verified that small magnetic drive impeller pumps work well under high vacuum, so these might be used - and they are very efficient. Yeah, it's elaborate, but it might be worth it if these air compressor units were to prove super reliable as a stationary steam power plant. I haven't discounted the prospect. If it could be devised to require little more than shoving wood splits into a furnace and cleaning out ash every few days, and nothing beyond simple routine maintenance and periodic engine overhaul, then it seems interesting prospect. Oh, also, it may be possible to separate water effectively from the crank case using small centrifugal separators designed for separating cream from milk - that is also an interesting prospect.

http://www.surpluscenter.com/Air-Pneumatics/Air-Compressors-Vacuum-Pumps/Belt-Driven-Compressors/23-CFM-AIR-COMPRESSOR-TWO-STAGE-5-HP-CAST-IRON-4-1066.axd An expander this size would generate one hp at only 3 hertz with steam pressure well under 200 psig, and assuming high expansion on the order of 8 fold...

Len Ovens wrote:It sounds overly complex at my stage of the game. My thought is that I need to have something that "turns" to play with first. First I turn it with compressed air then I make a steam gen, then I worry about collecting exhaust and oil separation etc. If I can get something that can run two speed... or two power levels, I have a 3.5kw gen... for wash days? To keep constant load when running that would require a switchable load. Then run at 1 hp with a small alternator the rest of the time. I think though, for learning, just the alternator would be best.

Len Ovens wrote:I have been looking through the cyclone site. The main differences seem to be the water lubrication which allows much higher pressure/temperature and no oil/water mixing problems. They seem also to use a tappet valve with variable timing. Aside from efficiency, this means it self starts (with the 6 cylinder model. not so sure about the 2 in lawn mowers). The bash valve will not self start... except by accident and then there is no surety of direction.

Another thing I noticed both with the cyclone site as well as others, is that the speed is obviously not that stable. I am not sure if this is just because they always show the startup stage and the speed settles as the steam generator does or if this is an inherent problem. I would think it would be fine for motive power, but if used as rotation for AC power it could be a problem. Unless an inverter is used. I would guess that because the the steam generation is somewhat disconnected there is a delay in control. A big flywheel can only help so much. On the other hand, have you ever heard a Hammond organ being run from a gas genset? They wander quite a bit too.

Anyway, I think that because of the infancy of this old tech stuff.... there is a lot that can be done. I am realizing that steam is actually "cool" compared to IC flue gas. I could see myself making a simple crankshaft with a disk and a normal rubber seal roller bearing... Talking lower pressure than the Cyclone of course. In fact almost no real milling.

William Bronson wrote:Is there a way to do steam without building an engine your self?
I skimmed this thread, but every thing steam seems to require a lot of modifications or out right fabrication.
The gasifiers can be very simple, simpler still if they are charcoal gasifiers.
I know fuel processing can be prohibitively labor intensive, but adressing that seems easier than building a steam engine.

Marcos Buenijo wrote:
http://cyclonepower.com/PDF/Cyclone%20Engine%20White%20Paper.pdf This is an interesting read. I can't say I agree with everything, but there is no doubt some opinions are expressed in this paper. James Crank is retired mechanical engineer and world recognized authority on steam car technology.