PUMPS AS TURBINES (PAT'S)
Robert Honders of New York is a member of the micro-hydro forum on Yahoo. He has a small micro-hydro
installation that consists of a pump with a directly coupled induction motor that is run in reverse to act as a turbine.
Check this page out for a selection chart that compares PAT's to Pelton and Turgo turbines.
The following is a discussion on how to use an induction motor as a generator with a link to his blog providing more detail information and I mean detail info. There are electrical schematics, advice on what type of pipe to install, control of the turbine power output, etc. Thank you very much Rob.
Hi fellow micro hydro enthusiasts.
First, let me say that I enjoy the back and forth on this site very much. Most of the time the info being distributed is really good sound engineering advice. Sometimes not so accurate. I must take issue with the following statement:
"Possible to use the induction motor as a generator but NOT an economical idea."
This is not only possible but very economical, especially when you use a 3 phase induction motor as a single or 3 phase generator. Please see: http://energyindependence-rob.blogspot.com/ for the details pictures and diagrams. Three phase motors are a bit of a mystery to most folks on a single phase grid. Maybe that is why three phase motors are so cheap. You can pick up a 3 phase 30HP (21KW) motor on Ebay for around $250 or sometimes less if you can pick it up locally. Now to run it as a 3 phase generator you'll need to add 2 oil filled capacitors, one 50MFD and one 100MFD across 2 of the phases and spin the shaft with your water power. That is all. Now this arrangement is good for at least 10Kw without overheating the motor due to unequal phase currents, but where else can you get a 10 KW generator for a couple hundred bucks and recycle an otherwise useless 3 phase motor? I am off the grid and on a 12KW 3 phase motor / generator as described. If you have lower head pressure you will want a 6 pole (1200 rpm) or an 8 pole (900 rpm) 3 phase motor to match to your turbine which, of course would be a recycled centrifugal pump run in reverse! It all works both ways. You might sacrifice a few percentage points in efficiency but during most of the year we have plenty of water to put a few extra gallons / minute through the pump / turbine to make up for this. Efficiency really only becomes a consideration during very low flow times when we have to shut down the system anyway because we need to provide water to maintain the aesthetics of the waterfall we harness. Now, it can also be argued that induction generators have poor reactive power, but there are solutions to that problem which I'll describe on the blog. In the mean time check Ebay for 3 phase centrifugal pumps that might be suitable for your site. I got all our "rotating" machinery in one pump/motor package for $500! Reduce Reuse and Recycle economically!
Due to certain limitations of Rob's web hosting service he is unable to provide a clear pdf version of the electrical diagram of his hydro installation. Therefore, he has agreed to let me offer it here on his behalf.
see articles on pumps as turbines on this web page: pumpworld.htm