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Thread: 1903 six HP steam engine powers modern off grid power system

  1. #211

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    I just became aware of a small scale steam engine system constructed and operated during the early 1980's. It was used to heat and power a modern home in Pennsylvania. It was fueled by anthracite coal. I understand there is an ASME paper describing the details. So, if I can get the paper, then I will post it here.

    The details I acquired show the system was extremely efficient. Well, actually, since it used saturated steam at only 135 psig and atmospheric exhaust, the highest possible efficiency is very low under these parameters. However, it showed 85%+ of Rankine cycle efficiency (or theoretical maximum). I would not have thought it possible to do so well in so small an engine (actually, until I get the ASME paper, then I am going to doubt the figure). It would be necessary to go higher steam temperature and reduce the condenser pressure to increase the actual efficiency. This would increase both the actual efficiency and the theoretical maximum efficiency. However, the percentage of theoretical max would be reduced. For example, the White Cliffs expander was measured at 70% of Rankine cycle efficiency using saturated steam at 540 psig and exhausting to a condenser at 160F (roughly 3.5 psia). There were additional losses in that engine due to the incomplete expansion (since it used high pressure steam plus a condenser under vacuum), clearance volume losses due to the bump valve configuration, thermal losses mainly from the high temperature differential in the cylinder (but also the higher steam temperatures), and the higher pressure likely contributed to steam leakage past the rings. Mainly, small steam engines are very poor at extracting work from low pressure steam. So, a small engine with atmospheric exhaust can potentially show a very high percentage of theoretical maximum efficiency provided the other losses are minimized.

    The expander was a single cylinder, single-acting, uniflow piston engine converted from a small industrial internal combustion engine. The steam admission used a single poppet valve with a push rod and cam. The system operated 24/7 during the heating seasons over a period of four years. Typical operating speed was 600 rpm. Power output was about 2 hp.

    http://www.thesteamboatingforum.net/...ile.php?id=187
    http://www.thesteamboatingforum.net/...ile.php?id=186
    Last edited by buenijo; 12-06-2016 at 12:42 PM.
    “The beginning of wisdom is to call things by their proper name.” - Confucius.
    "When plunder becomes a way of life for a group of men living together in society, they create for themselves in the course of time a legal system that authorizes it and a moral code that glorifies it." - Frederic Bastiat
    "Being well adjusted to a sick society is not a measure of health." - Jiddu Krishnamurti



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  3. #212

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    Still doing a bit of casual reading on steam engine systems. The same engineer who devised the residential scale CHP steam engine system described in the previous post also devised and operated a small steam generator using a simple principle I considered years ago. Apparently, it works very well. A problem with traditional monotube steam generators is the water feed rate must be closely matched to the furnace output. Otherwise, insufficient water flow can lead to excessive temperatures and possible tube burnout (or lube oil destruction), or excess water flow can flood the coil and carry water into the engine. The solution here is simple: just pump excess water at all times, then use a small separator vessel to accept the steam/water mixture from the tube - pressurized saturated steam is taken from the top and saturated water is drained from the bottom. The water level remains more or less constant as long as the orifice to the drain line is properly selected with respect to size. Turns out the mass flow rate of water through an orifice is on the order of 10 times greater than steam. So, very little steam can escape. As long as what little steam escapes has its heat captured and regenerated into the system (along with saturated water that drains through), then there is no loss beyond the very slight mechanical energy needed to operate the pump at the higher rate. Well, this reminded me of another idea. As long as the peak temperature of the water/steam is limited, then oil can be circulated with the steam/water without separation. This has been done before. As I recall, the early Doble steam cars did this for a while. However, they did show some problems that I suspect were caused by excessive steam temperatures. Taking the temperature down a notch while using very good synthetic oil should solve the problem (I speculate). Maintaining a steam generator of the type described here would allow for never superheating the steam - so the oil would be positively protected from excessive temperatures. Yeah, efficiency would be capped, but dry saturated steam can show good results - especially at higher pressures.

    An interesting dynamic on heat transfer is counterintuitive to many. Consider the following: compare two steam generator tubes (one steel and one copper) that have the same dimensions. Now, with all else equal, which one will generate steam at the higher rate when heated by the same furnace? The answer is the rate will not differ by much. The higher thermal conductivity of copper is not a significant factor here because it's the low rate of heat transfer from the flue gases to the outer tubing wall that is the bottleneck. It turns out the temperature of the inside tube wall is on the order of only 10F higher than the steam/water flowing within. The outside tube wall temperature for the copper might be just 2-3 degrees F hotter than the inner wall temperature. The outside tube wall temperature for the steel will be higher than the copper, but only on the order of 20-30 degrees F (based on the thermal conductivity of copper being roughly 10 times higher than carbon steel). So, this lower outer tube temperature for copper makes negligible difference to heat transfer rates when the furnace temperature is 1500F. Now, if one were using a liquid heat transfer fluid to generate steam, or using much lower temperatures, then copper might make sense - but not when using a furnace directly. Anyway, considering this, then it seems reasonable to circulate oil with the water/steam provided the steam generator tubing is always flooded with some water thereby making superheating impossible. If the pressure is set at say 300 psig, then the temperature of the oil could never rise above the saturation temperature for water at this pressure (which is 421F). Many synthetic lube oils can handle this temperature. Yeah, the efficiency of the system would be limited, but I've shown that it's possible to achieve 10-12% overall thermal efficiency at this steam temperature - with a good design. If the heat from the system is the main energy requirement, then efficiency doesn't matter so much. However, again, optimizing efficiency is important because good design can increase the efficiency many fold over poor design - and while being simpler mechanically! For example, the steam engine system that started this thread is quite literally 2-3% efficient in converting the chemical energy in wood to shaft work. A safer, simpler, and much more compact system can increase efficiency four fold - and it can be practical in the sense that it need be fueled only once or twice daily while it runs unattended to provide heat and electricity. The most recently described steam system proves it's possible to do this - after all, it was constructed and operated over a period of four years to heat and power a modern home.
    Last edited by buenijo; 12-06-2016 at 12:45 PM.
    “The beginning of wisdom is to call things by their proper name.” - Confucius.
    "When plunder becomes a way of life for a group of men living together in society, they create for themselves in the course of time a legal system that authorizes it and a moral code that glorifies it." - Frederic Bastiat
    "Being well adjusted to a sick society is not a measure of health." - Jiddu Krishnamurti

  4. #213

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    “The beginning of wisdom is to call things by their proper name.” - Confucius.
    "When plunder becomes a way of life for a group of men living together in society, they create for themselves in the course of time a legal system that authorizes it and a moral code that glorifies it." - Frederic Bastiat
    "Being well adjusted to a sick society is not a measure of health." - Jiddu Krishnamurti

  5. #214

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    Quote Originally Posted by buenijo View Post
    I would like to buy one, or a build one. Doesn't appear that it's available in the US.

  6. #215

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    Just found a lead on a 7 HP vertical single, like the one in the OP, in working condition for a decent price.

  7. #216

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    Quote Originally Posted by Anti Federalist View Post
    Just found a lead on a 7 HP vertical single, like the one in the OP, in working condition for a decent price.
    This thread is too long to review, so are you talking about a Lister engine?

    And if is, is it Limey or Injun built?

    Edit:

    Oh, hell.

    I just reviewed the OP.

    Nevermind.

    Steam, huh?
    "Even an establishment Republican like Jerry Moran is far more libertarian you are." Traditional Conservative

    "You're a far more horrible person than she (Bristol Palin) will ever be." angelatc

  8. #217

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    Quote Originally Posted by sparebulb View Post
    This thread is too long to review, so are you talking about a Lister engine?

    And if is, is it Limey or Injun built?

    Edit:

    Oh, hell.

    I just reviewed the OP.

    Nevermind.

    Steam, huh?
    The Limey Listers are going for a small fortune these days, since they have been banned for import by EPA fatwa

    Yup, steam...or the old "make and break engines", those have potential as well.

  9. #218

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    Dan Gelbart is a rather interesting fellow. Here is something he threw together in his free time:

    Through lives and lives shalt thou pay, O' king.

  10. #219

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    Quote Originally Posted by Anti Federalist View Post
    The Limey Listers are going for a small fortune these days, since they have been banned for import by EPA fatwa

    Yup, steam...or the old "make and break engines", those have potential as well.
    You can get the Injun ones, but they require some post purchase fiddling, since to get around the EPA fatwas, they have to be imported as "air compressors" and then the fule system added after the fact.

  11. #220

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    Quote Originally Posted by osan View Post
    Dan Gelbart is a rather interesting fellow. Here is something he threw together in his free time:

    Electronic timing on single stage steam engine...fascinating.

    Was this his invention?

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