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pollinator
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Educational and entertaining discussion of the prospect for steam automobiles:

http://www.backwoodshome.com/articles/silveira36.html
 
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it's an interesting and entertaining article, for sure, but some of the fuel issues he talks about could be done with current ICEs, too. Like using wood for fuel.

I'd love a steam setup, but they aren't cheap. And I don't have the resources to build one myself.

http://www.tinytechindia.com/steampowerplan.htm offer the most reasonable steam engines available, that I know of. But even then, they are significantly more expensive than other options, and require a lot of attention to keep going. It's not a case of turning it on and forgetting about it, and I think that's a major issue with the affordable steam systems I've seen. Those issues can be rectified, but they haven't been included in a consumer system, yet.

So, for the time being, stationary power, like an ICE with wood gas in a Combined heat and power setup would likely be the most cost effective route right now.
 
Marcos Buenijo
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Abe Connally wrote:it's an interesting and entertaining article, for sure, but some of the fuel issues he talks about could be done with current ICEs, too. Like using wood for fuel.

I'd love a steam setup, but they aren't cheap. And I don't have the resources to build one myself.

http://www.tinytechindia.com/steampowerplan.htm offer the most reasonable steam engines available, that I know of. But even then, they are significantly more expensive than other options, and require a lot of attention to keep going. It's not a case of turning it on and forgetting about it, and I think that's a major issue with the affordable steam systems I've seen. Those issues can be rectified, but they haven't been included in a consumer system, yet.

So, for the time being, stationary power, like an ICE with wood gas in a Combined heat and power setup would likely be the most cost effective route right now.


I agree. A wood gas engine system is the practical option for stationary CHP (as opposed to steam) simply because suitable hardware for steam is not available. Steam needs serious upgrading. However, I do believe that a modern steam system could be objectively superior with biomass fuel (and by a large margin). I have an interest in small scale steam because I understand better than most what's possible (I've done the research, and I also have formal training as a steam plant operator - the latter actually helps only marginally as small scale steam is a lost art). I may do a lengthy post on the topic for education purposes... but, again, as it stands right now, a wood gas engine system is the practical alternative between the two options.

 
Abe Connally
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Marcos Buenijo wrote: However, I do believe that a modern steam system could be objectively superior with biomass fuel (and by a large margin).

I completely agree with this statement, but like you said, there are no off-the-shelf systems for sale, unfortunately. I do think small-scale steam offers a lot of promise, and I hope some DIY approaches are developed towards the goal of producing something that is as easy to work with as an ICE.
 
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Looks cheaper than anything I've seen in the gasifier community! What issues do they have?? A ready to go 5 hp plant seems reasonable! Engine with boiler! What am i missing? How many hours are these engines expected to work?
 
Justus Walker
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aren't piston steam engines like 11% efficient? So a gasifier ICE rig would be 14%. Wouldn't steam be simpler? Again, please let me know what I'm missing.

so if i wanted 10 kWh of power per day for a year...

Runing a gasifier rig i'd need about 9.6m3 of wood
running one of these steam rigs i'd need about 12.3 m3 of wood.
More, but not by a ton. and the cost is better! And how about longevity of operation,engine maintenance. Please explain why gasifier ice rig would be better!
 
Marcos Buenijo
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Justus Walker wrote:Looks cheaper than anything I've seen in the gasifier community! What issues do they have?? A ready to go 5 hp plant seems reasonable! Engine with boiler! What am i missing? How many hours are these engines expected to work?


I don't know of any commercially available 5 hp steam engine system, and certainly not one that is inexpensive - definitely not one that is efficient. If you are considering a product, then please present it here so I can review it. I can say right off that any micro steam engine system using a "boiler" is a nonstarter for serious power generation. A modern system needs an efficient and compact steam generator.

The main issue with small scale steam engine systems is that they don't exist. Any that you may happen to find available is based on 150 year old technology that was killed for a good reason - or it's based on something even worse (like the Green steam engine). Sadly, the only hope for an individual to have a truly useful and efficient combined heat and power, biomass fueled, steam engine system is to build it or wait around for someone else to come up with a good product. There are some promising results from a few small companies, but they're not yet ready.

 
Justus Walker
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http://www.tinytechindia.com/steampowerplan.htm

Scroll down the page. There are entire power plants, ready for shipping. I don't know anything about steam. That's why i asked.

And what's wrong with the green steam engine??
 
Marcos Buenijo
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Justus Walker wrote:http://www.tinytechindia.com/steampowerplan.htm

Scroll down the page. There are entire power plants, ready for shipping. I don't know anything about steam. That's why i asked.

And what's wrong with the green steam engine??


I am familiar with Tiny Tech India. I corresponded with the owner Mr. Desai a few years back. I even suggested one of the recent mods he made to his engine after he told me that the city in which he lives is known primarily for the manufacture of diesel engines. You see, he now mounts a steam cylinder onto a two stroke diesel engine connecting the piston rod to the diesel piston using it as a crosshead (without the piston rings which would add unnecessary friction) - note the fins on the lower part of his engines - that's the diesel cylinder (fins are for air cooling). The engines are rugged. Unfortunately, they cannot achieve high efficiency. The best efficiency one could expect to achieve is an overall 5-6%, and this assumes that an efficient steam generator is used along with excellent insulation. These simple engines were never used primarily for power generation. They were always used where steam heating was the primary use with shaft power and electricity a useful byproduct. It's possible to boost efficiency up to about 8% by compounding two cylinders (feeding the exhaust of one cylinder to supply a second larger cylinder, or one of the same size that operates at a higher speed) and condensing the steam to form a vacuum to lessen back pressure. Personally, I think 8% is quite good IF the system were devised for a low output for long periods, but it would be tough to see it in practice. Besides, compounding represents added complexity and expense.

Also, beware that there will be many additional costs involved in importing such a system... and, I highly recommend against purchasing a boiler from this source. First of all, it's not an efficient boiler, but it also cannot be operated unattended. A useful system must be devised to generate steam without operator attention, and only a small monotube generator has a hope of doing this at the micro scale.

The Green steam engine simply cannot be configured for steam at sufficient pressures and temperatures for useful efficiency, and it will not stand up to abuse. It's a toy.

What is needed in small scale steam is an engine that achieves fairly high temperatures and pressures (temperature on the order of 500+ F, and pressure on the order of 300+ psi), achieves high expansion in a single cylinder, condenses the steam, uses a monotube steam generator, operates unattended for long periods at low power, fueled with wood with less processing than required by a wood gas engine system, and is compact. Under these conditions a unit could achieve an overall efficiency of 10-15% delivering both heat and electricity efficiently.
 
Justus Walker
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I see what you say. But surely there is someone out there. Like...

http://www.reliablesteam.com/RSE/RSEengines.html Kit or complete unit
http://www.strathsteam.com/page6.html a stationary unit designed for off the girders!
http://www.tinypower.com/store.php?crn=54&rn=258&action=show_detail or something like this!
http://www.mikebrownsolutions.com/mbsteam.htm - Mike seems like a serious minded guy. a bit pricey but, who knows, is it worth it?

Are these all super low efficient, toys as well.

I'm about ready to jump into gasification full scale, truck, house, etc. So I'm just making real sure I'd rather not do steam.

 
Abe Connally
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Justus Walker wrote:
I'm about ready to jump into gasification full scale, truck, house, etc. So I'm just making real sure I'd rather not do steam.

Do you know about the driveonwood.com resource? It has a good community over there for gasifiers.

The thing Marcos is saying, and I agree with him, is that these steam engines are small, inefficient, and are not leave-alone systems. That means you have to watch the system when it runs. It's not like an ICE that you can start and leave. To me, that is the most significant disadvantage of steam systems available on the market.

A gasifier still needs some attendance, but generally, you fill the hopper with wood, get it running, and then you can leave it and just check periodically. The overall cost for a gasifier setup with the same electrical output will be considerably lower.
 
Marcos Buenijo
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Justus Walker wrote:I see what you say. But surely there is someone out there. Like...

http://www.reliablesteam.com/RSE/RSEengines.html Kit or complete unit
http://www.strathsteam.com/page6.html a stationary unit designed for off the girders!
http://www.tinypower.com/store.php?crn=54&rn=258&action=show_detail or something like this!
http://www.mikebrownsolutions.com/mbsteam.htm - Mike seems like a serious minded guy. a bit pricey but, who knows, is it worth it?

Are these all super low efficient, toys as well.



I have looked into all of these before. These are good engines (not toys like the Green steam engine), but all will show low thermal efficiency compared to a good wood gas engine system. If you select a good engine, build a steam generator and gasifier furnace, and insulate the system very well, then you could could get a useful system IF you can make use of the heat. This last point is key. Actually, thermal efficiency may not be so important if you can make use of the heat. For example, it might be more useful in your setting to operate for longer periods a slow speed steam engine at low power rather than operate a wood gas engine system. The gas engine has to operate at a higher output to achieve high efficiency and keep the gasifier at sufficiently high temperatures to produce a clean gas. Generally this means at least 5 hp shaft power along with processing wood down to regularly sized chips or small chunks. It might be preferable to devise a system to use small wood splits or larger wood chunks (i.e. less fuel processing) to generate hot pyrolysis gas for combustion in a steam generator, and put the heat to full use.

I wanted to emphasize more than anything else that if you want to use a steam engine system based on these old expanders, then you can get a reliable system. However, it will not show the thermal efficiency you previously considered (11%) and you will have to build a good steam generator. Best case thermal efficiency is going to be 1/3 to 1/2 of a micro wood gas engine system operated at optimal output.
 
Marcos Buenijo
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Abe Connally wrote:

The thing Marcos is saying, and I agree with him, is that these steam engines are small, inefficient, and are not leave-alone systems. That means you have to watch the system when it runs. It's not like an ICE that you can start and leave. To me, that is the most significant disadvantage of steam systems available on the market.

A gasifier still needs some attendance, but generally, you fill the hopper with wood, get it running, and then you can leave it and just check periodically. The overall cost for a gasifier setup with the same electrical output will be considerably lower.


Right. Without building a gasifier furnace and steam generator that does not require operator attention, then one would have to baby sit the boiler - and that's not practical. I do believe the lower power of most of these steam engine systems to be an advantage for micro scale combined heat and power. It can operate at a low output and very low speeds for longer periods. This would be good to lessen battery discharge and while making use of the heat from the condenser for heating applications. Operating a system at a low power would make it simpler to construct a suitable gasifier furnace and steam generator unit. However, in any case, the steam engine option will require a lot more work to get a useful system on line.

For interest, here is one unit under development that I believe would be ideal. It's only a prototype. In the final form it would be condensing, insulated, and fully enclosed. Also, the company has plans for a 2 KW system that I believe would be more appropriate for individual use: http://www.youtube.com/watch?v=AKvBRP3Wz0Q . This is a more modern design using a high compression, double acting, uniflow piston engine. When insulated and fully condensing it should show a thermal efficiency well over 10%, and could approach 15%.
 
Justus Walker
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Yes, your right I think. I was more or less playing devil's advocate to get your input, and I really appreciate it. Basically the conclusion I had come to a few years ack when I originally looked at these system. 5-6% efficiency in general, 11-15% for the real high end. And costly. Prohibitively so. For $2k I can put together a pretty good gasifier system. for $4k I can put one together that will last a LONG time.

I guess I like the idea of steam. But even back in the day, steam micro power stations (for pumping water or running small farm mills, etc) were not really common. Stirling engines were used more commonly for that kind of thing for the reason mentioned above. What I would LOVE would be a stirling engine but that is a real pipe dream!!

Gasifier with ICE, here I come!

 
Marcos Buenijo
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I was looking over the contents of this thread again. It sure deviated away from the original post, but that's fine. I felt the need to make a point about the efficiency of a steam engine system as compared to a wood gas engine system. I mentioned the following previously, but it seems it may not be fully appreciated. There is a limitation on wood gas engine systems in that they cannot be operated efficiently at a low power without a very highly processed fuel source. This might be wood pellets, or very small regularly sized (sifted, sorted) wood chips, or perhaps nut shells or fruit pits. Even in this case it's difficult to operate efficiently below about 5 hp because very small gas engines are not very efficient, and the peak efficiency will fall on wood gas. Still, it's reasonable for a very good system to achieve 15% thermal efficiency at a very low output. A larger engine could see 20% with increased compression. This assumes the system is operated at a constant output where efficiency is optimal since the efficiency varies a great deal over the power range. Truly massive and sophisticated engines can do much better, but I'm restricting the argument to micro scale combined heat and power (individual/residential scale).

Perhaps the main benefit of a heat engine in the remote off grid setting is NOT the electricity it might provide, but the heat! In my opinion, any heat engine system operated in this setting that does not make use of the heat is highly inefficient. Therefore, "efficiency" should consider the heat. In this sense, a good micro steam engine system has the wood gas engine system beat right off the line since virtually all the heat available from the system is neatly packaged in a condenser in the form of one of the best heat conveying substances known (i.e. steam). If only a micro steam engine system could see similar thermal efficiencies as a wood gas engine system... but wait, it can! A simple piston steam engine system with bash valve and uniflow exhaust can see 15% net thermal efficiency - no compounding, no reheat, and only a single cylinder is necessary for a low power unit. What's necessary to achieve this is (1) very good efficiency in the steam generator - these have been constructed and demonstrated at 95% efficiency. Let's consider 90% to be a reasonable prospect. (2) superheated steam - needs steam at least 600F. (3) high expansion in the cylinder and sufficiently high steam pressure - a good 10 fold expansion or more can do it with 250+ psi steam. (4) high vacuum on the condenser - saturated pressure for steam at 150F is 3.5 psi, and 150 F is plenty hot for heating applications. (5) excellent thermal insulation on pretty much everything except the condenser.

Those who may have some interest should investigate the performance of the White Cliffs solar steam engine system. It showed an engine cycle efficiency of 22% using steam at 600 psi and 800F. If the steam were generated with a furnace, then 90% efficiency would take the net thermal efficiency down to 20%. The engine showed 20% efficiency with 700F steam, or about 18% with losses from a 90% efficient furnace. Since I'm comparing with a small wood gas engine system, then consider some disadvantages of the internal combustion engine in this setting (micro scale combined heat and power) including noise, additional heat exchange equipment necessary to capture and store heat from the engine, restricted to highly processed particulate biomass, and the inability for the small wood gas engine system to operate at very low outputs efficiently. Generally, to lessen fuel processing requirements and optimize the efficiency of the system, a larger engine at higher output must be used. This means intermittent operation at high power with a large battery and thermal mass. Consider again the system operated by Ken Boak (which I consider to be very impressive). Ken lives in the UK and has a high demand for heating applications. His system cannot be operated efficiently below about 5 hp. However, he can't make use of the electricity generated at more than 2500 watts except to load the engine down with electric space heaters! He provides data on his web site where he uses literally more than half the electricity generated by the engine in space heating. Folks, this is fitting a square peg into a round hole. Yes, I KNOW that a wood gas engine system is the only thing going right now for micro scale combined heat and power with biomass fuel. I am only trying to help the reader understand that a micro piston steam engine system fueled by biomass could be better for this particular application (micro scale combined heat and power with biomass fuel). I'm not trying to persuade more than hoping to educate.
 
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