Sunday, July 3, 2011

Common Micro Hydro Misconceptions

Hydro power - common misconceptions.

1. If there is a waterfall just let the falling water hit some paddles to which the generator is coupled and you are in business.
2. Rainwater running from the roof could be used to make electricity.
3. Hookup a turbine or Pelton wheel to your faucet, incoming waterline, or garden hose and you can keep the lights on for free. 
4. How about if I have a 2400 gallon tank 100 feet higher on a hill that fills up in 24 hours. How much electricity can I get? Answer: it will light up a night light continuously or brew coffee once in 24 hrs. (1800Watts for 10 min) 
Or 300Watt hrs  = .3Kwhrs about 2 cents worth.


Musibau said...

I am working on feasibility of using PAT within the process industry to replace throttle valves. However it seems early applications failed, do you have any insight to this application?

Rob said...

PATs used as throttle valves, pressure reducers and energy recovery.

Pump and motor may be used in reverse as a turbine / generator.  The centrifugal pump as turbine may be used 'in-line' to reduce water pressure and thereby recover the energy in the form of electricity. This is often done where a reservoir is located much higher than where the water is used, necessitating pressure reduction.

It is important to size the pump/turbine correctly for the net pressure drop/head, flow, and impeller diameter at the desired RPM, usually 900, 1200, or 1800 RPM for 60hz grid connected systems. The head or pressure to be dropped and flow rate (pipe diameter) will determine the electrical power output, the amount of recovered energy.

The output RPM will depend on the impeller diameter and the head/pressure drop. For low head/pressure drop systems, choose a lower RPM motor/generator and choose the impeller diameter to give approximately twice the rpm (with no electrical loading) than the normal operating loaded RPM. This is the operating point for best conversion efficiency assuming a constant head / pressure drop.

Anonymous said...

#4 under COMMON MICRO HYDRO MISCONCEPTIONS, is it feasible for a water tower to generate enough electricity to make it worthwhile to put a turbin in it, if so how much could it generate?