[Stoves] Green Steam Engine

Wed May 15 10:25:04 CDT 2013

Dear Bryce

I couldn't find his claim for 24% efficiency, but it seems to be very high. I calculate that the useable energy in the steam is less than 3%. 

His Horsepower claim also seems high. At 50 psig steam and 18 cubic feet per minute, I calculate the engine could develop a maximum of about 2 HP,  less than 1/2 of what he claims.

System heat losses from the engine will be excessive. Actual engine mechanical efficiency will probably be less than 50% 
Actual HP would likely be about 1 HP. 

18 Cubic feet per minute of 50 psig steam = 2.73 Lbs/Min would require a net heat input to the steam of about 1,150 BTU/Lb or 3,140 BTU/Min, or 188,370 BTU/Hr. If the Boiler was 80% efficient, fuel input would be about 235,463 BTU/Hr.
If the Boiler had a Char Producing Burner, with say 50% of the wood energy leaving as char, the input fuel energy would then have to be about 471,000 BTU/Hr. 

Wood input would have to be about 471,000/8,640 = 54.5 pounds per hour.

That seems like a lot of bone dry wood for 1 HP.

Perhaps someone could review my calculations?  I get nervous when differences are that great. 

Also... the Green Steam engine has a lot of moving parts. The temperature of 50 psig steam is about 297 F. It is hard to imagine the O-Rings lasting very long at these temperatures.

Best wishes,

Kevin

----- Original Message ----- 
  From: Bryce L Nordgren 
  To: Discussion of biomass cooking stoves 
  Sent: Wednesday, May 15, 2013 4:56 AM
  Subject: Re: [Stoves] Green Steam Engine

  Products which turn biomass into heat efficiently tend to be gasifiers. From TLUDs to 30kW+ hydronic heaters, the reason is the same: gasifier-combustors tend to operate more cleanly than their non-gasifier counterparts (woodstoves; open fires). 

  The GEK (not the GEK power pallet) may well serve as a biomass->heat converter if one omits the gas scrubber and uses their "flare" (or a better combustion/heat transfer chamber) to boil water. Recycling the exhaust steam to preheat fuel, then heat water would realize some degree of combined heat and power.

  As to the steam engine plans (not an actual engine)...A back of the envelope calculation, using his low number of 24% efficiency for condensing and recycling steam back to the boiler, yields something like 6.5 kg bone dry fuel/hour. The lower number of 12% for not recycling the steam would double that.

  The relevant question is whether the wobbly shaft drive really adds to the efficiency compared to traditional methods. Of course, you may also want to find out whether the cheap off the shelf parts you are supposed to locate yourself will handle 125psi, or whether the home version that runs off of a pressure cooker isn't really capable of 10hp. Steam power isn't new, and there's places that sell heavy castings with "ample safety factors".
  (http://www.reliablesteam.com/RSE/RSEengines.html)

  Bryce

  On Tue, May 14, 2013 at 6:42 PM, Kevin <kchisholm at ca.inter.net> wrote:

    Dear Crispin
    ----- Original Message ----- From: "Crispin Pemberton-Pigott" <crispinpigott at gmail.com>
    To: "Stoves" <stoves at lists.bioenergylists.org>
    Sent: Tuesday, May 14, 2013 6:40 PM

    Subject: Re: [Stoves] Green Steam Engine

      Kevin,
      Is that not what GEK does??
      Crispin
      From BB9900

    The GEK is a true Wood Gasifier, that takes in wood chips, and converts them to "Engine Grade Gas". (Woodgas with very low tar content.) The woodgas is sent to a Spark Ignition engine as fuel, to generate shaft power. It does produce a small percentage of char (and ash), but the char is pasically a waste product. Char production is fundamentally undesirable in that it represents a waste of input energy.

    The Green Steam Engine runs on steam, as its energy source, to produce shaft power. To get the steam, one needs a boiler, or a steam generating solar system. If a boiler is used, the fuel can be anything that releases heat on combustion... natural gas, fuel oil, biomass, etc. The fuel needs an appropriate "burner system." A "Full Combustion Stove System" can be used, to maximize the energy utilization of the fuel, or, where char production is wanted, a "Char Producing Stove System" can be used.

    Any further questions, please let me know.

    Best wishes,

    Kevin

      -----Original Message-----
      From: "Kevin" <kchisholm at ca.inter.net>
      Sender: "Stoves" <stoves-bounces at lists.bioenergylists.org>
      Date: Tue, 14 May 2013 18:35:42
      To: Discussion of biomass cooking stoves<stoves at lists.bioenergylists.org>
      Reply-To: Discussion of biomass cooking stoves
      <stoves at lists.bioenergylists.org>
      Subject: Re: [Stoves] Green Steam Engine

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