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%.
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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).
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One (1) horse power, thermal efficiency? Please!
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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
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Steve, that is exactly what I would have said if I could have said it in a paragraph or so but I couldn’t. 
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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
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Mark, After re-reading the posts I see that you did not get much of what you asked for. Twenty years ago I messed around with some small mono tube boilers ( homebrews) I still have the last one in my shop. The pictured unit has fifty feet of half in tube for a coil. The pump is a hypro good to about 700 psi, it takes about 3/4 hp to run the pump, The shell is SS and I used propane fuel. You would need a fire box or some kind of a rocket stove may work. For a steam engine you may want to look a reworked Wankel rotary.
Go for it Mark
Dave
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MarkG you missed the point completly.
Ken Boaks British made engine is a converted diesel internal combustion engine. Shame the US EPA made importing these and many other good simple old timers illeagal into the USofA anymore. I sold mine off. No way to reliably get parts anymore. Everything wears and needs repairing.
The Marathon engine, the Honda CHP engine could also be woodgas fuel converted in one afternoon also. Just like any methane/propane set up engine.
Woodgas IS bio-mass.
Charcoal gas is biomass.
US and EU spec fuelwood pellets are biomass.
US/Canadian and EU spec heating fuel woodchips are biomass.
I full expect with the intense European interest and now growing use in commercial fuelwood pellets in thier in home heating systems that out of Italy, Poland, the Chech Republic, Romania or the Unkraine someone will bring to market a small CHP external combustion engine based system offered that fuels with EU spec fuelwood pellets.
One NZ company is betting on a CHP Stirling cycle engine. Takes metal killing delta T’s to operate these if comparably small to IC piston engines.
The Germans and the Japanese and US companies are commited to doing this home CHP with internal combustion piston engines. California CARB certification of the Marathon and Freewatt/Ecowill systems show thier commitment to home CHP IC piston engines.
The Real in the World actual Users will be the ones again to say which of these three systems survives and will be the long term winner. And it will be manufacturing, operating and maintences costs that prove out the winner. These ARE efficiency numbers too.
Honda puts more piston IC engines on the face of the planet annually than anyone else.
That is where my last two engines purchased money and effort now gets commited.
This rest is just, “could of”, “would of”, “should of”. . . . never generate an actual real kilowatt used talk.
Pictures and actual commited developement work is what counts here on the DOW.
You really want to sell an idea, a concept here then you need to be burning through some actual biomass to prove your talk like KenB does. Ken is real. And puts it up real.
Like I do.
Like DousieR, MattR, ArvidO, and just about any other person posting here right down to one of the newest active members KeonKL does.
If you want your efforts to taken as real and relevent then you have to make yourself real and relevent. Talk is cheap and will be valued as such.
Cheerleading others on to do your actual developement work and Internet researching with no commitent from you at all except for key punching is better done with personal emails and personal websites.
Anyone wanting some actual in use/been used modern small steam systems work representing decades, and actual lifes works read here thoroughly:
http://kimmelsteam.com
Over 130 system critiqued and pictured here by modern steam enthusiast Tom Kimmel. He has layed out lots of time, money, years and effort in real paper and bent and formed even destoyed metals to collect up and put out this information trove. Use it for gain and he does aske for a site support donation.
Washington State Steve Unruh
Steve, I expected the conversation to reach this point. It seems you missed my point completely. My only purpose here is to encourage people to consider another way to make use of scarce resources (i.e. biomass) that can be more efficient. I suppose the only hope in bringing back small scale steam is for a lot of money to get thrown at it.
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I composed a reply and changed my mind content to let Steve speak for me but what the hell. From reading all the posts I think you are sold on steam and steam alone. There is nothing wrong with that and good luck to you. The problem seems to be that you are trying to convert a group that has a great solution that uses existing cheap available technology to buy into a plan that may or may not work will cost a fortune and will reward you with insignificant increases in efficiency… maybe. I would prefer to work on recapturing heat from my working system…The only part I agree with is matching generator to load and DC charging. You might check out the microcogen group they talk a lot about that end of things
Best regards, David Baillie
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Thank you David Baillie for the courteous reply. It seems misunderstandings are easy to foster here despite an effort toward clarity. I’m actually very excited about future developments in small scale wood gas engine systems. I think there is a lot of potential there for many applications.
My efforts here were pretty much doomed to fail. I was prepared for it. I don’t disagree with most of the arguments made by Mr. Unruh. He’s mostly right. Period. The fact is that the existing infrastructure supports internal combustion, so small scale steam is not a practical alternative. I knew this going into the discussion. Still, the physics says clearly that it can be superior for combined heat and power with biomass fuel, and in all respects. Yeah, it’s unrealistic to expect individuals with limited resources to pursue it. However, if more people had a better understanding of steam power, then this would make it more likely for interesting developments to take place in unlikely places. That was really my purpose in starting this discussion: education. People who think they understand steam power generally do not. Thanks again David.
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David,
I agree with your last statements. Just like I posted originally, steam has lots of potential and I look forward to Cyclone and other companies pushing the development forward. They have the capital and resources to pursue it. At the personal level there’s very little I can do to further this goal, so I’m content to wait and see, and in the meantime work with woodgas in ICE engines.
BTW, thanks for the details on the Cyclone’s inner workings. It is an amazing project, and it seems very close to fruition. Their WHE is almost exactly what you have described, and will be commercially available sometime next year… barring further delays. (Also thanks for the Bourque engine link, thats some good reading.)
If/when we can get our hands on the Mark V, the acceleration and fuel economy will far surpass every effort with stock gasoline engines on woodgas.
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Mark. If I was disrespectful in my efficiency comments I am sorry. I am not a native english user so things may have different sound in English than in Norwegian. My point was along the same lines as SteveU. If your producing 1 kW, it’s perhaps better to spend a few hours of chopping wood to fuel a woodgas system that CAN be built in resonable time, rather than to chase efficiency in a (massive) technology development project that may turn into nothing.
Craft, engine, I have no additional info, I belive the use some type of CFC-type working fluid.
I have my background in mechanical engineering, 5 years in college and over 15 years as an engineer in various types of engineering (electronics, municipal, offshore oil and gas). The most impressive thing about Wayne Keith and the woodgassers on this forum (myself NOT included, I am a lurker) is that they actually get something built that works. Based on my experience as a design engineer, I must say that deveolping something like the WK system, building it basically in a field!!! , and then using it for years in day to day operations, is off the chart in resourcefulness. I am extremly impressed! Steam I belive is much more difficult to get to a practical level in a DIY-setteting.
Keep up the good work people!
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Mark,
Thank you for your patience and perseverance. There are sometimes people with different ideas that come here to “sell” them, and will leave thinking we are narrow-minded, and write us off as such. You haven’t, and we appreciate it.
You will also find that many here are of the same mindset of the Jeffersonian intellectual agrarian of the 18th and early 19th centuries. If supper was cooked, animals fed and secure for the night, and the kids had warm, dry beds to sleep in, then no one was much concerned about lost efficiencies. As for me, I’m not willing to sweat another 80% to gain back the lost 20%.
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Magne, I perceived no disrespect at all sir. I thank you for the link on the Craft engine. I’m happy to learn of another small scale rankine cycle engine, especially one with so many resources directed at it. Your mentioning the use of a refrigerant is congruent with the low temperature of 400F listed for the working fluid. I suspected so based on that temperature, but without evidence I was unwilling to go there. The higher mean effective pressure should improve efficiency all else equal.
Steam would definitely be more difficult to get to a practical level mainly because the single most important component (the expander) has to be developed. However, you’ve seen some of the talent displayed on this site. If the people here had a better understanding of steam power, then someone might get motivated to put their tools and talent to work on it… then who knows what’s possible. The particular configuration that I believe would be optimal is a low power system that operates more or less continually, and I believe it can be made to be unattended beyond the occasion fuel loading and ash clean out. This would optimize the use of the heat while also minimizing energy conversion losses in electricity generation. I have doubts about a wood gas engine system being able to do this, but I’m convinced that a very slow moving piston steam engine can do it… and heat recovery would be inherently simpler… just gotta get the efficiency up.
Yeah, I’m highly impressed with what Mr. Keith does. The ingenuity he displays impresses me more than anything. That chunker of his, for example, is a brilliant example. Simple and functional. Making the most of what you have. On that note, looks like we’ll just keep making the most of the gas engine until/if modern piston steam engines come along. 
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Thanks Alex. Again, I know what’s up… but I’m a teacher at heart (and training). I do believe steam can be superior, but yeah… we’re not there yet.
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Dave Bloom, I missed your post. Looks like a fun project you had there. I once constructed a similar system, but shut it down midstream once I realized (1) more money than I was willing to spend was required to continue, and (2) conceded that it really wasn’t going to result in anything useful anyway. The practical side of me won out. The main problem in my case was not having a suitable expander to meet the required efficiency. You mentioned a Wankel. That has no hope of passing muster. I believe a compounded piston engine with reheat and heat regeneration is the best prospect mainly because it can see high efficiency with very limited steam temperatures, and it can operate at very low speeds. Another possible configuration is a high compression uniflow that adds a reheat similar to what Cyclone is doing. This approach could allow higher efficiency without exposing the steam inlet valve and steam generator tubing to excessive temperatures… and without resorting to compounding. Still, without getting away from oil lubrication there will likely be problems.
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