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Energy from vacuum

Low pressure from venturi generates power
  (+9, -5)
(+9, -5)
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A venturi tube is a cylinder with a smooth contraction in the middle. If liquid flows through the tube there is a lower pressure at the contraction (This is used for generating vacuum in the laboratory with a device called an aspirator, also called an eductor-jet pump).

How does it work? This tube or aspirator is placed in a river or stream, the flow of water through it generates a vacuum or zone of low pressure. A pipe or rigid hose is connected from the venturi to a turbine or piston engine to generate small amounts of electricity.

The difference between the atmosferic presure and the outlet at the low pressure of the vacuum is used to drive the turbine or reciprocating engine.

atomico, Nov 01 2008

Wikipedia: venturi tube http://en.wikipedia.org/wiki/Venturi_tube
[theGem, Nov 01 2008]

Wikipedia: Pelton wheel http://en.wikipedia.org/wiki/Pelton_wheel
[theGem, Nov 02 2008]

Venturi Siphon http://video.google...=UTF-8&sa=N&tab=iv#
(Notice there is a flow agitator or bubbler screen on faucets, I think venturi siphons with laminar flows just contribute to internal boundary layer effect or compressional flow choke without turbulence) [quantum_flux, Nov 03 2008]

[link]






       Workable, but nowhere near as efficient as a Pelton wheel given the same mass flow rate.   

       There might be certain advantages - no submerged moving parts .....   

       There must be prior art on this somewhere - it's just a hydraulic ram pump in reverse.   

       (We will bestow a bun upon you for at least not coming up with that wretched "Zero Point Energy" thing YET AGAIN....)
8th of 7, Nov 01 2008
  

       Such a process would be horribly inefficient. Why not use the dynamic pressure directly from the main streamflows to run a turbine? What, nuclear or something?
quantum_flux, Nov 03 2008
  

       Well, it would be an exceptional thing to have if you were stuck on a deserted island with nothing but waterfalls and air driven turbines. +
daseva, Nov 03 2008
  

       //We see it so often here.//   

       Indeed. The point of low pressure is *after* the constriction, and the change in pressure is compensation for the increase in velocity. If you make the faster fluid do work, you will slow it down, which will increase its pressure. What you are basically doing is nothing.
MikeD, Nov 03 2008
  

       Just so you all know, Bubba's previous comment points towards a repeated anno of mine, which I have now removed because it embarrases me far more than this explanation.   

       The velocity is highest at the middle of the constriction, and so this is where pressure will be lowest, MikeD.
daseva, Nov 03 2008
  

       /We see it so often here./   

       Yep, another funnel-promoting, Bernoulli-be-damned HB idea.
Texticle, Nov 03 2008
  

       After some much needed research (as pointed out by daseva), I shamefully renounce the first half of my annotation, but haphazardly stand behind the latter.
MikeD, Nov 03 2008
  

       And the conclusion: Use the water pressure (that you must have) to drive whatever axial motion that you desire. That sucking sound is wasted energy.
WcW, Nov 03 2008
  

       Unless the generator is a noise-generator.
quantum_flux, Nov 04 2008
  

       Warning: Long, Humourless, overly serious attempt to defend the indefensible technology below. Proceed at your own risk. *******************   

       A turbine in the water will be of course more efficient, but it was invented already.   

       I agree this is an obviously inefficient device and it will hardly generate any power.   

       Are there any potential benefits at all of this odd configuration?   

       All I can imagine are maybe some practical advantages if you start to think about the maintenance and wear that occur in all machines having moving parts and multiple fluids. For example:   

       1. Since the turbine is off the water, it is easier to access and maintain.   

       2. Since the turbine deals with rarefied air instead of water. There might be less fouling, less erosion, no waterproof seals required, as rarefied air is less conductive, a generator does not need to be waterproofed)   

       Let's not fool ourselves though, if we try to add something like a filter to ensure the rarefied air is clean this will probably add too much pressure drop. Something like a cyclone or settling chamber might do for the grossest particles.   

       In what circumstances would it be useful? Most likely never.   

       Or maybe in a remote, unmanned location where maintenance is expensive, and other alternatives won't work (i.e. too cloudy, rainy, or dusty for solar panels).   

       However the design maybe intriguing enough to get a grant to build a prototype, and evaluate its efficency or lak thereof. All of this possibly paid for by NASA, DOD or DOE, which are always interested in such oddball energy sources for their robotic probes, transmittters, landmines, etc.
atomico, Dec 30 2008
  

       Gee why not have two casimir plates in a perpendicular field of two attracting rare earth magnets?
travbm, Oct 29 2015
  
      
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