I'm not a Hvac guy, but,
I want to use high pressure refrigerant as steam, to run a compressor (backwards) to run a generator. (to run my house, or charge a battery pack)
Is there anyway to match all of this together? What rating on the compressor would tell me that its strong enough to run a (say) 20hp generator?
I want to put the refrigerant steam into the drive side of the compressor to subsequently run the generator. How much pressure out of how large a line will turn the right size compressor.
I'm sure this is not a normal question. Its diffinently in the DIY area. And, probably no one has all the answers, but I would appreciate any answer, even a pretty good guess, to help me get started.
Not a DIY site, especially not for a wonderment like this idea.
I'm not sure what refrigerant you are planning to use as the "steam", or how you would go about modifying a compressor to act as a "steam" engine to drive your generator, but if you are planning on driving a 20 hp load with it, the quantity of refrigerant "steam" needed would be huge, as would the size of the compressor.
Even if you somehow managed to create a device that is fairly mechanically efficient, with a closed loop system, the energy requirement to cool and condense the refrigerant "steam" back to a liquid for reuse would exceed the output of the generator. No free lunch in the cold harsh reality of physics.
If your idea is to operate the refrigerant "steam" side as an open loop system, that would be highly illegal with most chemicals used as refrigerants. The refrigerant cost would also greatly exceed the fuel cost of a conventional generator.
If more government is the answer, then it's a really stupid question.
Instead of reinventing the wheel, why not get a Solar PV Panel to charge your batteries and a generator?
Originally Posted by clockou
Google "Refrigerant Steam Engines". Surprisingly, there's a lot of discussion going on out there. Mostly "pie in the sky" stuff, but a few thought provoking ones.
I particularly like this one where it talks about using scroll compressors:
Theoretically, I suppose it's possible. Using a refrigerant instead of water allows for the the boiling of the refrigerant to create high pressure "steam" utilizing a relative low temperature heat source and condensing it with a cool medium as a heat sink.
However, to attempt to build such a machine using a device designed as a refrigeration compressor would appear to have far too many stumbling block to be even remotely practical.
In any case, you won't get much detailed help here...even if there is someone familiar with such applications...because this site doesn't allow such discussion in an open forum.
Honestly, I doubt a compressor as manufactured today would do it. There is too much restriction to be efficient, think discharge and suction valves. What you would need is one with no valve plates, and a way to control the "steam" flow. the least amount of resistance to flow would be best to spin your generator. to me, a centrifugal type arrangement might be best as the wheels dont have high lift and spin rather freely in comparison. but then again WTF do i know?
I did a little searching around and found that such "reverse compressors" already exist and are used extensively in industry. They're called "turboexpanders".
Check out what Wikipedia says about their use in power generation applications.
More interesting to us refrigeration guys though is how turboexpanders can also be used to replace expansion valves in a system...and generate power in the process.
I read where a turboexpander connected to the compressor shaft can generate around 15% of the power required by the compressor.
Last edited by icemeister; 05-28-2010 at 04:25 PM.
Reason: Ooops...Forgot to add link.
Condensing back to liquid, wouldn't be that much of a problem.
Finding a suitable compressor could be the main problem.
But, as Stamas said, We can't help you.
Turbine would be easier. And then why not just use water rather than refrigerant. But first, do the math and you'll find because of losses due to efficiency you'll have a net loss. Our electrical grid is only 32% efficient.
Now, if you had a fast moving stream in your backyard you'd have something.
Tracers work both ways.
What you are describing is an ORC (Organic Rankine Cycle). It uses the same basic thermodynamic cycle as a steam powerplant (steam meaning water for the working fluid) although it uses a organic (meaning carbon in the molecule) working fluid. Some even use typical commercial refrigerants such as R134a. There have been special refrigerants that are designed specifically for ORC applications (R245FA for example).
The cycle efficiency is dependent on the temperature gradient that you have (how cold the cold sink, or condensor, is versus how hot the heat source, or evaporator is). In very basic terms it is a refrigeration cycle in reverse. If you have a "hot source" of about 200F and a cold source of 70F (typical outside air temp) then the cycle efficiency will be somewhere around 5-6%.
You read that right Five to Six percent efficient.
That means that in order to generate 20 HP, you need about twenty times that from your heat source. This also means that you have to reject about nineteen times that to the cold source (this means a fairly large condensor is required).
You could build one on your own, but it would be fairly costly and you really need to read up on it (and thermodynamics). I would suggest using a screw compressor, they have been used in some small applications as expanders. A centrifugal compressor would most likely need to be re-wheeled to be an expander (the blade angles are basically completely different, plus you need some kind of guide vane to guide the gas into the wheel). A screw compressor run backwards is much simpler.
If you really feel the need after reading this to learn more, I would suggest RefProp, which is a thermodynamic software that can be used to design the cycle.
Also, for those HVAC guys interested, Carrier built some small ORC's (~200 kW) using chiller parts. They are now built by UTC under the brand Pratt and Whitney (the power division). The marketing geniuses came up with the name "purecycle".
Yeah yeah yeah... Keep giving him links so he can go blow himself up.
Not as lean, not as mean, but I'm still a hardcore, ass-kicking, hard charging Marine! Oohrah!
Gotta give the guy credit for thinking somewhat outside the box, it's a pretty cool idea.
The nice thing about steam vs refrigerant though, is it's easy to generate steam with fire, and it's tough to give fire a horsepower rating, but generally fire would be easier / cheaper to create steam with vs refrigeration methods and the means to move it.
While we can't help you (especially me, cuz I can barely wrap my brain around the refrigeration cycle when running the right way), I wish you luck if you're determined to keep pursuing this. Stay safe!
"If you call that hard work, a koalas life would look heroic."
It's on the market, I bought one from jc witney,It works great! 375.00 + shipping.
I use it to power my dope grow lights and sell the remaining power back to the local utility and clear 1500 a day!
Google "ACME perpetual motion machine". I believe Wlie E. Coyote holds the patent
Go here for your best alternative process: http://www.toolbase.org/Technology-I...ned-heat-power
Last edited by btuhack; 07-08-2010 at 01:04 PM.