Small Water Turbines

Just a thought, but couldn't you find out what your lowest flow rate is and size for that flow. Then adjust your flow rate by mechanically restricting it to keep it at that rate. A small flow meter with a feedback could adjust a valve or gate to maintain an even flow.

The stream eventually dries up in the late spring. I would like to produce as much power as possible. As the flow is reduced I would still like to produce power as low as I could go. Thanks!

How are you going to access this potential energy?

Dam?

GA for the first sensible idea that I read.

If you have a constant 38 foot head of water, why would the flow rate effect the turbine speed?

If his stream dries up, he's gonna have problems no matter what.

A Kaplan turbine has a variable pitch runner.

it's all about the power controller you use .look into it.

Bioramani,

"The frequency of the generated power depends on the rpm if you are generating AC power"

For a small water turbine an inverter could provide the desired voltage and frequency right up until the water can no longer turn it fast enough. RPM would not be a problem.

A lot of new emergency generators operate that way. The engine speed automatically changes to match power demand. Therefore, if you're powering only some small appliance or lights, the generator runs at a low engine rpm. Then, as power demand increases, the engine revs up accordingly. The key is its multipole rotor with a small stator and Pulse Width Modulation inverter. This design is smaller and lighter than a conventional two-pole alternator and large stator.

Most generators can't power anything with microcomputers or sophisticated electronics — their generated power has too many spikes and irregular wavelengths that can mess up and even destroy sensitive equipment. With an inverter system's Pulse Width Modulation (PWM) wavelength distortion is less than 2.5 percent. It's ideal for equipment that requires stable frequency and voltage.
A water turbine driven inverter generator would be ideal for your application.

Jon

Thanks Jon! I am learning a lot and look forward to living off the grid!

You want the tail to wag the dog?

Hi

I install micro-hydro for a living and make use of variable flows all the time. I use ES&D or Harris Turbines with four nozzles. I size the nozzles (using 1, 2, 3 or 4)for the flow variables throughout the year and activate/deactivate as the flows change seasonally. These are DC turbines and batteries, inverter, etc are required equipment. Good luck.

Thank you! What is the lowest flow you would recommend at thirty eight feet of head for use of the harris turbine? This would tell me which turbine to look at. I would be looking at a hybred ( solar/water) system for my power supply.

The Harris Pelton Turbines can operate on as little as 4 gpm, but at 38 feet of head that isn't going to produce much (~16 watts). At 48 VDC they are rated up to 2.5kVA. If you can pick up a little more head by tapping farther up the creek you would be better off, but simply, you can expect your production as follows:

(Flow[gpm]*Head[feet])/10=output[watts]

so at 100 gpm*38 feet/10=380 watts. +/- for system efficiency. 9.12kVA/day.

Remember to size your diversion load to carry both your PVs and your hydro combined.

Thank you!

Egertolearn you would get more from this, and all these folk, if you knew your approximate flow rates, so we knew your installation scale.

Volume affects everything, including the type of turbine best suited, the power capture electrical approach, so water flow and/or electrical regulation choices.

If you have a big variation, you may even consider a dual system of Pelton + Francis. Also with a big seasonal flow variation there is usually a big variation in rubbish. Pelton's small jets mean they need cleaner water than Francis. This effects how and where you place intakes and strainer design and maintenance. These links may be useful.

http://www.absak.com/pdf/peltonspec.pdf

http://www.brighthub.com/engineering/mechanical/articles/26551.aspx

http://www.absak.com/catalog/product_info.php/cPath/33_89_92/products_id/18

Thank you for all the informational links. I have a flow rate estimate from 1000's gallon/min. to an actually test in late spring before dry season of 78 gallons/min. I would like to size this so I take advantage of all the flow possible. Rubbish is not a problem, thought soil sediment will be.

Landscape cloth does part sediment from flow of water very well.

I have another question. I have a pond at the bottom of my water falls. Would it make sense to put in a wind mill water pump to pump water back to the top of the falls? I would need to find one that would pump as much water as possible.

For pumping water, I suggest investigating Sum Pumps- solar-powered pumps that I have installed with no battery backup- they pump when the sun is shining, and rest at night. Fairly effective, when one does not need constant water supply...

I've set up pumps as a diversion load. You would still need a resistive element as a backup diversion load, but a pump can be used.... you won't get as much water back as you dropped down, but it's something.

Adding a water wheel may aid/supplement the windmill when de wind does not blow?

Trouble with windmills at the bottom is getting the mill high enough to get some wind.

Other than that, it should work quite well.

The suggestion of a solar pump would probably be better (and more expensive I suspect).

A pumped storage can be quite an effective energy store.

You will, of course, need some sort of dam up the top.

How about a dam below and a basin above?

Thank you all for your input. I need to look into the wind mill at the top with a total lift of approx. 50 feet from the pond below. The top is somewhat flat so a pond at the top would be a challenge. Solar would be expensive and the efficiency may be a problem as the average days sun shine is around 1 day of sun to 7 days of clouds. Nice huh!

Full heavy clouds will diminish PV efficiency however broken cloud cover can producer increased efficiencies over that of a cloudless day due reflection off the clouds too.

I, too, am working with a small hydro installation using Harris Turbines with multiple nozzles, apparently same scheme you are using (activate/deactivate nozzles to accommodate varying flow rates). So far, it works...