Steam Engine Discussion

Well, this is going to be a lengthy post. I think I need the additional words to make a clear argument. Please read carefully and critically as the information is likely to challenge your beliefs.

I believe that a small piston steam engine has the potential to be superior to a wood gas engine system for combined heat and power in the off-grid/remote residential setting. I realize that this option is severely hobbled due to a lack of hardware, and just as important a general lack of knowledge (even engineers often don’t have a firm grasp on the principles, but the lack of real hands-on experience is even more damning). Also, please note that a conventional piston steam engine is not going to cut it. The thermal efficiency of these systems is generally too low to be practical. However, certain things can be done to dramatically increase the efficiency of a piston steam engine system.

The main problem I see with a wood gas engine system in this setting stems from the fact that a modest off grid home does not require electricity generated at a high rate. A wood gas engine system can generate electrical power with impressive efficiency. However, this is not useful when much of the energy is lost in batteries and inverters. More important, the losses associated with operating a constant speed generator at part load is significant. An engine capable of 20% thermal efficiency near full load might see 10% at 25% load, and small wood gas engine systems suitable for residential scale combined heat and power are generally only about 15% efficient at best. The best compromise I’ve seen is the system maintained by Ken Boak. The configuration he uses does a great job of minimizing the losses while recovering most of the heat for useful purposes. Most interesting in his case is the way he loads the engine down to pull air through the gasifier at a sufficient rate and to see high engine efficiency. He does this by operating electric space heaters off the generator head. While effective, I don’t consider this to be an efficient use of electricity in the off grid setting. The generator head provides ac power while also charging the batteries, and heat from the engine cooling system and engine exhaust is stored in water. When the engine is shutdown during most of each day, then the battery provides electricity with an inverter and the store of heated water provides heat.

It seems to me that a slow moving piston steam engine that operates at a low and near constant output for long periods could be superior. The engine can operate at much lower speeds for superior longevity, there would be a lot more heat captured from the system (proportionally speaking), and the gasifier could be a lot simpler. The engine can be used to drive an efficient permanent magnet alternator for charging a modest battery (the ability to maintain a smaller battery here is an advantage), and ac electricity can be provided with a good inverter. Matching the alternator output more closely to actual loads in the home will minimize battery losses.

Again, the problems with this alternative were mentioned in the first paragraph. My point is this: why not find a way around these problems?

It’s possible for a piston steam engine to see a thermal efficiency equal to and superior to a wood gas engine system. There are several configurations that can do this, but I tend to favor the compounded piston engine with reheat and heat regeneration as this approach does not require extremely high steam temperatures. A small engine with this general design constructed during the late 1920’s saw a net thermal efficiency approaching 30%, and this was with peak steam temperatures under 900F as I recall. Peak steam pressure was well under 1000 psig. It’s possible for a two cylinder compound piston steam engine with reheat and heat regeneration to see a thermal efficiency of 15% with steam pressure under 500 psig and with a peak steam temperature under 600F (need special attention to minimize thermal losses here with good heat exchangers and good thermal insulation). The reason this configuration works so well is that adding steam reheat between the cylinders allows for increasing the steam temperature as the steam expands through the system. Increasing the steam temperature increases the steam pressure in direct proportion, and this increases engine power. Since the steam is already a superheated vapor while expanding through the engine, then most of the heat added to the steam with this reheat process is converted to additional engine work. The low pressure steam finally exhausted from the low pressure cylinder is highly superheated, and this heat can be regenerated back into the system with air heating (both the air supplied to the gasifier, and the air used to support combustion). Furthermore, since this process increases furnace temperatures (which is not required for a limited steam temperature), then a lot of excess air can be used, and this provides a greater mass of air for full heat regeneration. So, most of the heat added with reheat is converted to additional engine work, yet a lot of this heat can be returned to the system. Looking at the system in this way makes the most sense to me, and I believe that most people with a mechanical mind can see the benefit when presented this way.

The reason I am mentioning this is that it’s clear from reading this forum that there are many people here with the fabrication skills to make something like this. Myself, I have good ideas and a solid foundation in physics and engineering principles, but I don’t have the tools nor the fabrication experience to do this in a cost effective way. I believe a slow moving piston steam engine optimized for continuous operation at 1 KW output for extended periods with special emphasis on heat recovery for useful purposes, and with a net thermal efficiency on the order of 15% would be superior to any small wood gas engine system in the residential combined heat and power setting. I believe it will provide what’s needed with a lot less fuel consumption. Think about it.

Mark Hello
Here is a short read for you on boiler water chemistry.If you don’t do it right you won’t have a boiler for long,
High pressure and low pressure boilers are not the same. You would need a monotube type like the old White steam cars. You might get one built for $25.000 that would fit your needs. Parts coils, high pressure water pumps,water softeners.return water tanks,chemical pumps, feed water tanks to name a few things. then license and insurance.You are right it could work well but it won’t be small scale.
Dave

Dave, I’m not sure we’re considering the same thing here. Why not small scale? First, a monotube is the way to go, but 25K for a steam generator at the low steam rates and modest steam pressure/temps I’m talking about is ludicrous. I’m talking about water feed rates on the order of 3 gallons per hour for a 2 hp engine. The surface area of the steam generator need be on the order of 5 square feet, and it can be made to be very compact… 50 feet of 3/8" steel tubing could do it, maybe add a copper tubing preheater on the furnace exhaust for efficiency. License and insurance for such a thing? Really?

A high pressure water pump suitable for this application can be fabricated as a single plunger from a small pipe nipple, couple check valves, and a stuffing box at one end to seal the plunger. That’s not a problem. Seriously. Also, any small piston or plunger water pump at a sufficient rated pressure would serve here. The feed pump doesn’t present a problem.

A small steam generator with modest temperatures and pressures can do very well will with distilled water, and emphasis on maintaining a tight system (free of oxygen) would ensure a very long life. There is no need for water softeners or any chemical treatment whatever. Also, when you’re talking about a steam generator fabricated from 50 feet of steel tubing, then it’s not a big deal to replace when necessary, and a rupture would not be dangerous here.

The only real problem is not having a suitable piston expander available that can see the required efficiency and reliability. One of the main problems is preventing damage to lubricating oil under the conditions of reheat and when a condensing system is used (assuming lube oil is used at all). Personally, I suggest moving away from oil lubrication, and with sustained low power at very low speeds I believe this can be effective.

… actually, the main problem is getting people to think seriously about this alternative, and to challenge a lot of the myths on steam power.

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Hi Mark, As much as I love steam, you cannot get around the tremendous amount of energy it takes to turn water at 212 F into steam at 212 F. This latent heat of vaporization is unusable energy. Take the same amount of energy and put it into an internal combustion engine and use it. Steam components are expensive, can be violently explosive and regulated. Even small monotube boilers over a certain capacity have to be certified and inspected, at least in PA. When coming to these conclusions, I went down the charcoal gas road.
Gary in PA

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Mark,
5 sq ft heating surface = .5 hp you would need at least 20 sq feet for 2hp steam. The oxygen is in the water and will attack steel.
The State of Minnesota MN Boiler Section oversees all boilers and pressure vessels in the State of Minnesota. The State has adopted the ASME Boiler Pressure Vessel Code (including CSD-1 for controls and safety devices for automatically fired boilers) and requires “R” stamped repair entities for welded repairs. Your state my be different.
Steel @ 900 deg. F is getting close to red hot and does not have the strength of cold steel. You may be able to get a coil from a pressure washer to fit your needs but the coil is only a small part of the system.
All of the old steam cars used steam oil in the system for lube.
I’m not saying it won’t work, to get it reliable it won’t be simple. I know I run two Claytons and one Dutton HP boiler. If boilers were’nt a pain in the --s we would all be driving on steam.

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Gary, I love your gasifiers for their simplicity. However, the low net efficiency bothers me. There is a lot of energy wasted in making the charcoal. It makes great sense for intermittent use in fueling small engines, and in that case it seems unbeatable. However, what I’m considering is a system for primary heat and power in an off-grid setting. I have a good foundation in steam power as I used to be a steam plant operator and I also having training in boiler water chemistry control. I also have a physics degree. I’m convinced the problems you are describing here can be overcome. For example, most of the superheat added to the steam can be converted to work with sufficient expansion of the steam, and any superheat remaining can be regenerated back into the system within limits (but in practice quite a bit of heat can be regenerated). Compounding with reheat allows for adding this superheat without increasing peak steam temperatures. It’s an elegant configuration that I believe can be practical with relatively modest steam temps/pressures, and in a small system designed for a constant output at low power.

Your numbers are incorrect. You could reference the steam generator dimensions on systems such as the Doble or White steam cars to verify. Note that high pressure steam sees much higher time in a tube of a given volume as compared to low pressure steam such as atmospheric (which is what you’re figures are likely considering). This is time for a lot of heat transfer to take place. ADDENDUM: Steam boat engine systems call for 5-10 square feet of surface area per hp… 10 square feet for simple single expansion engines, and 5 square feet for compound engines. This assumes fire tube boilers, or Yarrow type water tube boilers. I’m considering an engine with a thermal efficiency on the order of 3 times higher, so it needs a lot less steam (about 3 times less in fact). Also, a monotube sees more efficient heat transfer. The higher pressure steam systems also need less area due to the high residence time mentioned before. Bottom line is that a monotube steam generator for 500 psig steam at 25 pounds per hour can be very compact. I am aware of an efficient steam generator designed for 200 pounds steam per hour at 200 psig and 600F that fit into a 8 inch diameter cylindrical housing a foot in length.

Yes, oxygen in the water is undesirable. Therefore, a closed system is desired as I specified.

I discussed a system with steam temperature less than 600F and under 500 psig. If you have not actually read my initial post, then please do so. The pressure rating of steel tubing suitable for this construction is well over 10,000 psig. Of course the rating drops with increasing temperature, but there is a fantastic safety margin with 500 psig.

I know it won’t be simple or inexpensive, otherwise I would have tried it by now. From what I’ve seen on this forum there are many here with the tools and talent to pull it off in a cost effective way… if only they had an more complete understanding of steam power. There really is a lot of BS on steam power recycled on the internet.

I’m not talking about steam for motive power. That’s a whole different problem. Steam cars cannot be competitive to internal combustion without a fantastic amount of money thrown at it. Yes, all steam cars used lube oil, and this includes the Doble that operated with highly superheated steam at 1000 psig, and with a furnace that operated with peak temperatures approaching 3000F (necessary for high steam rates for such a compact boiler). The solution there was attention to tubing diameter to increase steam velocity and strip the tubing walls of oil and prevent oil from settling in the tubes. I’m talking about steam under 500 psig and under 600F. 15% net thermal efficiency is absolutely possible with steam under these conditions within sufficient expansion, reheat, heat regeneration, and excellent insulation.

I just wanted to add that there are plenty of good reasons to not go down the steam path. The best reason I can think of is to emphasize the simplicity of a wood gas suction engine. It’s pretty damn amazing that an engine can be connected to a little more than a steel can filled with wood chunks, add a few filters and pipes for cooling, and then push a truck down the road. If biomass is desired for automotive fuel, then a wood gas engine system is unbeatable as far as I’m concerned. If biomass is desired to generate electricity at a high rate, then I also see nothing better than a wood gas engine system. If biomass is desired for backup power generation for such things as bulk battery charging when solar panels can’t keep up with demand, then I also see nothing better than a wood gas engine system.

When it comes to small scale steam in the off grid setting, I’m considering a very particular configuration where a piston engine system is optimized for high thermal efficiency, and to deliver heat and power at a constant low rate. It’s purpose is as a primary power plant for an off-grid/remote home where biomass is the primary energy resource. The ideal setting is a cold climate where biomass is plentiful. Sure, one can get a big battery and charge it regularly with a big wood gas engine system, try to recover as much heat from the process as possible, then augment heating with a biomass furnace. It works. However, what I’m considering would be more efficient and elegant. I’m just trying to get people thinking outside the box here.

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Hi Mark
My great grandfather was Richard Trevithick.
So I have always been interested in steam power.
At collage I built a steam car that traveled 1126m on 20 ml of methanol.
It worked on an impulse turbine.
I always thought a peristaltic pump running as a turbine would be extremely efficient.

If you have any designs or videos of what you are thinking of would be great to see?

Thanks
Patrick

“When it comes to small scale steam in the off grid setting, I’m considering a very particular configuration where a piston engine system is optimized for high thermal efficiency, and to deliver heat and power at a constant low rate.”

Mark,

I’ve been a steam enthusiast before I was into woodgas. I love steam engines and firmly believe they’ve gotten the short end of the stick over the past hundred years. Steam has lots of potential.

But I’m also realistic. Everything I’ve ever read or saw indicated that piston steam engines are slow and reliable. But they are also very inefficient. There are several reasons:

The temperatures of the steam must remain low, and therefore efficiency is low. Hi-temp steam has more efficiency but will carbonize the oil for the steam valves and piston. THis limits efficiency to around 15% or less. The steam you’re talking about is correct for the engine type; however it won’t be “high thermal efficiency”. And that’s just the expander (engine); the boiler will lose tons of heat out the stack.

Mike Brown sells steam engines in this size range. http://www.mikebrownsolutions.com/mbsteam.htm

He highly recommends generating your power in the morning and using batteries to get through the day. He quotes fueling rates: “Our 2-cylinder 3 horsepower steam engine will provide 1500 watts of electrical power and over 100,000 BTUs of exhaust heat…It will require 20 pounds of wood per hour.”

20 lbs/hr is energy equivalent to 1 gallon gasoline per hour, to produce 1500W. Most 1500W generators will use a quart per hour at full load, or 4-5 lbs of wood.

Keeping a boiler stoked up all day for an idle steam engine is not a smart use of your firewood. You’ll want some sort of storage to account for peak demands and idle periods, not to do so is very inefficient.

CHP can be useful to reclaim some waste heat - but at this point you might as well have a gasoline engine do the work, and reclaim the heat from that. There will be far less waste heat to deal with.

If you’re mostly concerned about the noise, I’d be looking into the Lister slow speed engines. They’re quiet and just as reliable as a steam engine - but no boiler to mess with.

As for the auto engines, I’ve got to respectfully disagree. It has been done and will be again. Check out Cyclone Power engines, they’ve got a 100 HP automotive steam engine that’s coming to market in a couple years, which claims 35% or better efficiency. They’re using supercritical steam and a completely self contained uniflow radial engine and condenser. These guys are for real, they make engines for the military. This is our best shot for the future of steam cars. http://cyclonepower.com/

Until this happens, we’re stuck with the good old ICEs. They’re hard to beat for efficiency and versatility. I’m ever thankful that they run on woodgas as well!!

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Chris, I’m familiar with the Cyclone engines. Cyclone is doing amazing things - really cutting edge stuff. I’m behind their work and I’m even a shareholder, but I stand by my previous comment… it will indeed finally take a fantastic amount of money for steam cars to be competitive with conventional automobiles. The Cyclone uses extremely high temperatures, high expansion, heat regeneration, and even reheat to see high thermal efficiency, and they do it without compounding. Peak steam temperatures approach 1500F, and they’re shooting for a lot higher (scary!). I’ll mention some details that you may not be aware of, just for interest - you’ll love it… most of the residual steam in the cylinder that is not exhausted through the exhaust ports is recompressed at a high compression ratio into a reheat tube that is exposed to the highest furnace temperatures (furnace is mounted on top of the cylinders). The length of this reheat tube is tuned to set up a standing wave of superheated steam to optimize heat transfer. There is a cam and push-rod operated needle valve in the cylinder head that admits steam from the supercritical steam generator into the cylinder head during each stroke. The “spider” bearing they use to connect the radial pistons to the crank sets up a very interesting cycle on the pistons such that the pistons dwell at the top of their stroke, and this buys time during each cycle to reach higher steam pressure in the cylinder head, and helps increase expansion during the power stroke. The cycle resembles a two stroke Diesel in many ways. There is also NO oil lubrication (water lubricated) by using piston rings and bearings made of polyetherketone (PEEK) and actively water cooling and lubricating the piston rings and bearings. The friction is so low that their 100 hp engine can be cycled at the rated speed of 3500 rpm with only 3 hp. The pistons are unlike those in any internal combustion engine as there is a large carbon heat shield on the piston face and the piston ring is set very low in the piston to protect from the highest temperatures. I could go on, but I’ve found a lot of people familar with the Cyclone engines aren’t aware of some of these details. Amazing stuff indeed. Cyclone also has a 20 hp stationary steam engine with a total weight (including condenser, pumps, steam generators, etc… total package) less than 100 pounds. Net thermal efficiency was measured at 31% with steam temperature in steam generator limited to 1000F (high efficiency largely due to reheat tube and water cooled condenser).

Based on Cyclone’s work it’s clear that the steam temperatures do not have to stay low as you wrote here. However, I don’t suggest that very high steam temperatures be used for a small residential scale unit developed by garage mechanics. I suggest limiting the temperature to 600F at 500 psig. Even the Stanley Steamer operated at this steam temperature and pressure with a superheater below the fire tube boiler, and this was more than 100 years ago… the White worked with these temperatures in the late 1800’s (but lower pressure). Also, you’re talking about stoking boilers. I’m not talking about 200 year old steam practice here. I’m talking about flaring hot wood gas from a wood gasifier to heat a compact steam generator. Supply the gasifier with air preheated by superheated steam exhausted from the engine (before the steam goes to a condenser), and mix the hot wood gas with preheated air in the flare. I’m talking about using a gasifier similar to those used to generate engine grade gas, but without gas cooling or filtration.

Yes, high temperature steam is bad for oil, but look what Cyclone is doing. With temperatures limited to 600F or so, and with a very slow moving engine, I believe it’s possible to do away with oil lubrication. It’s not the scope of the message here to suggest possibilities as I’m only pointing out the potential of steam while trying to correct misconceptions, but I suggest experimenting with different kinds of high temperature compression packing as piston seals to move away from oil lubrication. Very slow moving and low power might work here. There are piston steam engines working with no oil lubrication and superheated steam that are manufactured in Germany by Spilling, but they’re fairly large piston engines not suitable for the application I’m talking about. I understand one being dissuaded from trying to develop something like this as it would be a serious challenge and would be costly, but misinformation should not play a part in that decision.

Now, since I’ve written so much what’s the harm in a little more. To investigate the thermodynamics of a compounded piston steam engine with reheat and heat regeneration, one might take a look at www.newsteamengine.com. Dr. Bourque has done a lot of research into a particular automotive steam engine design he devised. His cycle shows a net thermal efficiency of 36% with peak steam temperature of 1100F (2000+ psig) and with a condenser saturation temperature of 280F (engine exhausts into condenser maintained at about 35 psig). Without reheat and heat regeneration such an engine would barely exceed 20% efficiency. Drop the condenser to a vacuum, and peak steam temperature can be decreased to 1000F for the same efficiency (he put condenser under pressure for higher temperature and better cooling in the automotive setting - needed a compact condenser). Similarly, a two cylinder compound piston engine capable of of 6-8% thermal efficiency with saturated steam at 200 psig and with condenser can double its efficiency with higher steam pressure (500 psig), superheat (600F steam temp), higher expansion, steam reheat, and heat regeneration. Sounds complicated, but we’re talking about small heat exchangers at 1-2 hp.

If we are going back to external combustion I suggest this:

http://www.proepowersystems.com/

Perhaps a turbine, hybrid electric and woodgas generator could make forestry machinery and the like run on wood with effisiency north of 40%.

Chris, I didn’t touch on some other comments. The problem with an engine system that uses a Mike Brown expander would be a low thermal efficiency on the order of 4-5% at best. It’s a non-starter for any serious work.

As far as using a wood gas engine system with heat recovery, yes that is the next best thing to the kind of system I’m talking about. I cited Ken Boak’s work in the first post. What he’s doing is great. However, a rugged and compact 1-2 hp steam engine system with a similar thermal efficiency would be superior in the sense that it would see superior heat recovery (all waste heat is available at condenser), fuel gas requires no cooling or filtration, would be quieter, the electrical output would be more closely matched to actual loads in the home for fewer battery losses, and a smaller battery is required and/or there would be less discharge on the battery for longer battery life (lower battery costs in either case).

One (1) horse power, thermal efficiency? Please!

Ok, if we like Rankine, what about this?

http://www.vdg.no/index.php?articleid=8

Magne, that Craftengine flew under my radar. I’d like to have more specific information on the engine design. Let me know if you have any additional information as what’s provided at the link is vague (along with a lot of marketing hype). If there are established engine manufacturers working on this system, then it looks very promising. Based on what I was able to find out, it appears to a two cylinder single acting engine with poppet intake valves… possibly uniflow exhaust, and possibly there is cylinder jacketing for cylinder heating. If that’s the case, then the 400F working fluid should allow 10% net thermal efficiency. That’s actually very good for 400F. Something like this would make a wood gas engine system obsolete for this setting (small scale combined heat and power). If the price is right and assuming the system is very reliable, then that product should do extremely well.

BTW, my interest is restricted to very small scale systems that optimize the use of biomass for residential scale cogeneration. My interest is in individual energy self-reliance. I happen to think small scale steam power has more potential in this application than a wood gas engine system.

NOTE: That proepowersystems engine looks like a Brayton cycle engine that I considered several years ago… fundamentally identical. Wood gassers should take a look, as this is a very simple way to construct an external combustion engine that can use existing piston compressors and engines.

NOTE: That 1 hp rating is the low end, but I believe 1-2 hp is sufficient for an engine capable of continual operation. 2 hp will provide 1 KW electrical even after alternator and inverter losses are considered. If the loads in the home are well matched to the engine output, then battery losses are minimized. However, the battery is there as a buffer when required. A low power engine that operates like this for long periods will also allow for using a smaller battery while minimizing battery discharge. The battery is an Achilles heel in the off grid setting, and moving away from heavy reliance on a battery system is a good idea in my opinion. As far as thermal efficiency goes, I believe 15% is within reason for the kind of system I’ve considered. Although, a simpler system at 10% thermal efficiency would be worth it in my opinion.

Hello MarkG
As much as I have wanted to like steam there are three very serious mistakes you are making in your premises.

The First and most serious is not keeping up with currently developed and offered small IC piston engine based commercially offered home size CHP systems. 5-6 different systems out there in the World with at least 50,000 installed and in actual use system. Look at this one with 2.5kW/el sizing:
www.marathonengine.com/index.html
Follow all of the links and downloads and you will find a fully US/Canadian/EU/California certified system. Water-cooled slant cylinder gasious engine with a PM direct driven genrator, incorperated inverter/charger and full intergration support. In home installable and insurable.
They “only” quote 25% fuel BTU to electrical out efficiency but with the pumped engine coolant heat and an intergrated SS exhaust heat exchanger then have 65% input fuel BTU (by the engine) heated water energy recovery available = 90% fuel use cycle efficiency. IF you use the heats Sensibly. House space, domestic HW, shops, greenhouse, hotframe growers, aqua-farming, dog house, water troughs, ect. You DID say off grid - lots of sensible uses for heats. Ha! A person could hot pack/pressure can food with IC engine heat in the summer! 210-240F at 7.5-15 PSI is just the ticket.
Another system in deployment smaller at 1kW/el rated is based around Honda’s new Atkinson cycle engine and marketed under the "Freewatt’ and “Ecowill” names in the US and Japan.
These are all spec. methane and propane fueled based. Easily converted to woodgas or charcoal gas fueling. As already on the market, with all developement and certifications done MUCH better for a DIY to emulating/reverse engineering with off the shelf componets than any new steam system requiring from the ground up developing.
Now to woodgas fuel burner heating for your steam . . .
Without the working IC piston engine suck drawing the gasifer you can figure easily 250 watts of now continous blower power needed then for the gasifer hearth blowing or sucking per every hp/kW of engine shaft power you want to use This is real world expereinces I am stating. Continous duty blowers cost bucks. They Wear out. Need to be a “critical” pre-bought spare. And just like any batteries costs Blower use needs to be calculated as an expendable.

Second premise mistake you are making is saying that the DIY’s here would be capable of 500F/600PSI building and fabricating. The guys with lathes, casting expereince and/or good welding and milling capabilty would be 350F/150PSI steam capable for sure. But your 500F/600PSI is a quantum leap up from that. And very few are going to be willing to commit to a 1,000+ hour multiphased yet to be proven concept project. Low Temperature/Pressure puts you back into that single diget effinecies at the expansion engine. O.K.: up to 16% on the engine IF you go with a triple cylinder compound expansion engine. (Reliable Steam Co.) Or even a bit more efficnecy conceded with your more complex to valve/route and insulate proposal at again this higher not DIY capable 500/600 T/P base.
Why would anyone here want to commit to an experimental 1,000 hour project at new to them continuous high temeratures and pressures when in literally one weekend they could be Gillmore charcoal gasifing, pre-existing IC piston engine running and generating? Or in just a few hundred hours at the most of no machining; just grind cutting, MIG/sick welding, be up and woodgas IC piston engine running and generating for electrical and heat? GEK, Vulcan, S.Abadessa ALL offer base woodgasifier kits to build up off of. ArvidO will sell a base developed woodgasifier hearth to small engine supply build around. These are all at an easy atmopheric pressure +/- 10%.
Lots of us here will help fellows make up thier own designs for their own conditions and capabilites.
Give them hours and hours of two-way expereinced operator running advices with woodgas supplied IC engine running.
Steam they will be hung out there A-L-L on their own.
Take just one comparable componet: a shut off valve. Steam is going to require a metal, pressure rated, corrosion resistant valves. The WK wood gasifer system plan calls for a packge of three common tennis valves for air shut offs!

Third assumed premise is the same as most who’ve never actually woodfueled gasified made IS the fuel wood itself.
So join the crowd with this one. Fellows actually annualy heating with wood it is easy to tell them that woodfueled gasifier or steam generating for now your home electrical power ARE you willing now to source, prep and supply for an individual off-grid home now a minimun of TWICE the amount wood you normally use?? When I say CORDS and TONS of wood fuel they understand. Guys used to thinking in easy dense spec “fuel” gallons/therms/gasious cubic feet really haven’t got a clue what woodfueling will really mean in thier daily life. Same with home eggs and chickens.
The interest I used to have for personal use home power steam was the ability to be able to use the same prepped stove wood that I use for home/shop/greenhouse heating. Cut to 18" “cordwood” split pieces. Searching out; finding; and then traveling to look at actual in use small steam systems showed that most were converted to petroleum burners to avoid the hourly needed restoking with bulk cord wood. Yes you may be able to make a small footprint monotube steam generator but it will NOT remain small and then have an actual useable bulk fuel wood hearth area in it! And Especially they burner converted to get the needed direct heat produced to steam generated CONTROL that monotube types need. Well proven now that only diesel/kerosene burners or even commercial fuel wood pellets burners give can give this finite heat control. Bulk wood burns do not change rates rapidly at all. Very slow to change. WHY most of the oldtime bulk wood steam gnerators were fire tube - with large, large steam chambers for the pre-produced steam reserve power. They were the go BIG BOOM ones!
So out the window for all of that “steam advantage” ballyhooed consept of fueling with anything burnable, scrap, scrounged, found. Wrong!.
Buying out of pocket with post taxed dollars spec. grade petrol fuels I buy no road taxed farm diesel as the best regional BTU fuel value. Then run that in a far, far simpler actual diesel engines. I still have two of those. Turn key. Fuel it up. Change the oil, coolant and battery every so often.

To actually usable woodgas fuel you do need to MORE process the raw fuel wood down from length cut 16", 18" or best of furnaces actual 4 FOOT cordwood lengths or pallet boards.
The least energy intensive way to do this is to chunk down to the gasifier needed chunk sizing. Easy then to batch fuel small systems with chunked woodfuel every 2-4 hours. Two spaced daily cycles and you have enough Off-Grid home daily power and heat produced for 24 hours. Yes batteries and thermal storage needed.
If you are Off-Grid located 200+ days a year of useable solar then PV should have been your initial self-power investment. THEN off-grid you’d already have the batteries and inverter/converter. THEN for the 100-150 days a year of no-low solar you would also already have the back up IC engine-generator also. Most stationary home woodgasing interrested/needing have already made these initial investments and woodfuel now is the way to convert from bought out fuels to home grown fuels.

Too raw wood chip, classify sort; or, grind and pelletize densify to be able to then auger in woodbased fuel takes a LOT more woodfuel prepping energy imputs. Only fair to quote these mechanical driven processing energys out of the original woodfuel energy system input in your fuel to shaft effinecy calculations. Otherwise you are hidden subsidizing. THESE fuel forms are what is needed for a more continous ran grid tied systems or your continuous ran proposed steam 1kW system. This chipping and grinding/pelletizing WILL cost you a high single diget bite out of your system energy effinency total.

You did say Off-Grid and personal use. Off-grid the most important design criteria is not absolute fuel effincy but Keep It Simple to operate, maintain and repair. These have to be able to be done by more than just one person who did the developing and system building. KISS rules Off-Gridding.

Regards
Steve Unruh

Steve, that is exactly what I would have said if I could have said it in a paragraph or so but I couldn’t. :slight_smile:

Steve, I am restricting my considerations to biomass fuel. The marathon engine you linked is designed for natural gas. Also, any reference to other refined fuels you made is beyond the scope my arguments. My position is that I believe it’s possible to devise a compact and slow moving piston engine to see a thermal efficiency equal to a very small wood gas engine system. Since I believe the primary advantage of a wood gas engine system to a wood fueled steam system in the micro (residential) combined heat and power setting is the much higher thermal efficiency of the former, then with this problem solved I’m arguing that the steam system would be superior.

I’ve touched on all the points you listed here already. I am aware of these problems. However, one point where we differ is that I don’t see 500 psi / 600F steam as so daunting. If the White and Stanley worked with these temperatures using cast iron and carbon steel, then I don’t see this as a game stopper. The most likely game stopper is widespread lack of knowledge, lack of experience, and resulting (and justifiable) apprehension when it comes to steam power. This is a lost art, and my knowledge is sorely limited along with all others. Yet, I believe based on my research and limited experience that it’s possible to devise a compact and highly efficient low power steam system that operates reliably, for long periods, and largely unattended to deliver heat and power (and fueled by a wood gasifier). Is it too much trouble? Perhaps. Still, I think it would be worth it. Also, I’ve got a strong suspicion that should biomass be increasingly exploited in the near future for micro (residential) scale combined heat and power, then we’re going to start seeing piston steam engines developed for this purpose. I’m not the only one who believes there to be potential here.

NOTE: Again, my main purpose is to get people thinking outside the box. I don’t have a problem with disagreement, I’m only trying to be clear. I will emphasize again that I am very impressed with what Ken Boak did with a wood gas engine system. As long as a modern piston steam engine is not an option, then I see his approach as the next best thing.

ADDENDUM: If you are not aware of the White Cliffs solar steam engine project, then google it. The relevant point I hope to make by referencing this project is that a conventional two stroke Lister Diesel engine was converted to steam to show long term reliable operation for actual real world electrification of a rural community. I do NOT suggest this be done. Rather, I wish only to show that conventional materials are compatible with steam at 800F+ and 900+ psig which were the steam conditions of that particular engine. The stock engine lubrication system was retained in that case, and there was an oil separator provided. I can’t help but to lean toward the conclusion that 500 psig and 600F should not be considered untouchable. BTW, that particular engine was a single-acting uniflow (no reheat and no compounding). It saw thermal efficiencies in the low 20% (with boiler losses is would be around 18%, same as a good wood gas engine system of similar output). Again, I’m suggesting a different configuration. It’s an interesting project. I certainly do NOT suggest converting a Lister engine to steam! If I had a good Lister, I would convert it to wood gas.

TOMORROW I will celebrate 3000 miles on my WK firetube gasifier in a Dodge Dakota. Plus 2000 miles on the same gasifier previously powering up a 3/4 ton Ford van. That is 5000 miles (as soon as I fire up tomorrow)( !!! ). All of that on wood chopped up gleefully with a four pound hatchet since last July. (2012)
More to the point, I have been living off-grid the whole time.(17 years) And I will LOUDLY agree with Steve that what works off grid is what works.
Really, what can a man do???
A millionaire would be hard pressed to hire a shop to build a steam system for his little off-grid hide-away. But a man can woodgas!
And one more thing. There are better things in life than electric appliances. The actual fact is the greatest effienciency AND the greatest pleasure AND health are gained from eating food and doing it by hand.

John Stout