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   ‘Simple Rankine’  Hot Water 
Powered alternator systems

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One of the members in the group asked about a small system that can be run from a wood stove supplying the hot water.

   This is the first layout  I came come up with for something fairly simple.   The member wants to use a scroll compressor backwards as an expander.  I haven’t ever worked with one so I really don’t know what the capabilities of one are.    This system is a modification of one of the drum engine setups that will hopefully run continuously as long as it is supplied with enough hot and cold water.

 I’m still working with that idea and the more I look at it the better it looks to me.  A simple Rankine engine is not really very complicated.  Here is the next version of the system with some info on the propane temp versus pressure expansion ratios.

This is the third version layout and I think I have everything there now that would be needed for the system to operate manually or by electrical control.  I’m still not too sure about how much power the system would actually generate as I haven’t worked out all the math for the heat exchanges.  By just general guesstimation I would say somewhere around a minimum or 250 watts and possible much as a kilowatt.  It basically depends on the amount of hot and cold water available to the system.

I have added the Big-Buzz generator to a system layout.  Someone in one of the Yahoo groups I’m in suggested I look at a webpage for a company was doing something like this but on a much bigger scale.

             Here is the link to that site.
  They build a  commercial system that much more powerful and is way out of my league. My ideas and designs are for relatively low pressure systems that the backyard mechanic can build mostly from salvaged hardware. 

  Instead of a mechanical feed pump system, they are using a small pressure container that can be heated or cooled to provide the feed pressure to the main boiler system.

  This is a simpler fluid layout for the same system without the tube and shell heat exchangers mixed in.  I’m still trying to design the system so that minimal modifications would have to be done to anything.  It would be a simpler layout with a with a few tank changes.  I may draw up a layout showing that too.

  Almost everything is off-the-shelf parts except for the “BIG-BUZZ” engine/alternator itself and the “pump” boiler and it can also be made from standard copper , brass or steel pipe parts.

This is pretty much the same flow layout as the one above. I’ve used modified tanks on this version.  It should still fit in the average washing machine size box.


In this drawing I have added what I called the “mini-tide” system  This gives the system the ability to generate power for battery charging by the Big-buzz or an alternator could be hooked up to the hydraulic motor output.  The motor output could also be used to power other machines such as a saw, etc….

  The hydraulic motor would run in 3 minute cycles as the fluid transfers through it from one tank to the other one. At the end of the cycle, the change over using the current setup would only take a few seconds as the system could be getting the boiler ready for the next cycle while a current cycle is taking place. 

 It wouldn’t be a continuous run system using the tanks but it would be close.