Advice on hydro design

[Sifis]

Greetings

I am looking for information and help on designing a micro hydro system.

I have a system in place that consists of a homemade unit that uses an 80 amp alternator and a Harris Pelton wheel.

Specs are as follows:

85. psi static head
    
65. psi dynamic head @ 30gpm
    
    

During the summer water drops to about 10-15gpm, psi increases to about 75.

I make a max of 10 amps at 12 volts with the 30 gpm and do not get any amperage at 10-15gpm.

My goal is to build a system that produce more than the 10 amps at 30 gpm during the winter.  I would also like to utilize the 10-15 gpm during the summer.

Any ideas will be greatly apreciated.

[Flux]

I am not sure what gallons you use, but if it is the US gallon your efficiency is very low, if imperial gallons it is even worse.

Car alternators are not very good for this job, you would do much better with a decent directly driven pm alternator. This would help most in the summer.

I don't see why you have a higher dynamic pressure with the low flow, I would expect it to fall and that you would need a smaller nozzle in summer.

Do you have any idea of the speed of the turbine in summer, I can only assume it is too slow for the alternator to cut in.

I would have thought that you could be managing over 400W in winter and you should get half that in summer.

Flux

[Nando]

What is the diameter of the Pelton wheel ?.

What size nozzles are you using for different seasons and are you sure that the pipe stays filled ?.

Using your 85 PSI the Head is 196 feet = 60 meters

30 GPM = 1.9 l/s

The calculated expected power is 60 * 1.9 * 6 = 684 watts

It seems that you have problems with the Pelton diameter and/or the car alternator.

The car alternator may go as low as 40 to 60 % with an overall efficiency of about 30 % or so % which may be one of the reasons for such low power.

I think that you need a Brushless Permanent Magnet motor to attain the maximum efficiency -- you need to look into the Pelton diameter as well.

[Sifis]

Flux

The info I gave is in US gallons.  I can only assume that the low output of the turbine is do to an oversized and inefficiant alternator.

The higher dynamic pressure is because I have to cut back from four 3/16 inch nozzels to one or two.  The deccrese in volume also decreases my presure loss due to friction.  I am using abou 1700 feet of pipe (200 at 2", 200 at 1 1/2" and 1300 at 1 1/4").  

The rpm of the turbine durring the summer is to low to produce anything close to 12+ volts.

I would like to find a good source for a lower rpm pm alternator that would fit the bill, or possibly help in designing one.

Any ideas?

Thanks

[Sifis]

Nando

The pelton wheel that I am using is produced by Harris and is a "bronze cast pelton wheel with a 4" pitch diameter " (from there web site).  Is there a good formula or ratio for determining wheel diameter to flow/presure?

During the winter we use four 3/16" nozles and the pipe is always filled.  The flow during the summer only allows one or two 3/16" nozzles.  Any more will drain the pipe.

I have tried different combinations of nozzles from 1/8 to 3/8 and have yet to come up with a better amperage.

Do you have any ideas on suppliers or a design for a pm motor?

Thanks again

[Nando]

Checking the 4 Nozzles volume gives 2.44 l/s at 60 meters head.

The RPM is close to 3275 sufficient for the car alternator being able to produce the necessary watts.

You may have different problems:

One : The Jets are not properly set to maximize the torque.

Two : The generator may have too much field current.

Three : The regulator is no producing its voltage, REMOVE THE LOAD AND MEASURE THE output voltage with a small lamp ( like 10 watts ), It should be 14.2 to 14.6 volts -- during this test the Hydro and alternator may Rev up to 6000 RPM, OK for a few minutes.

Four : The Pelton Wheel to Nozzle placement may need adjustment.

Five : The Pelton may have the wrong spoon profile.

SIX : The Hydro is loaded so much that is NOT allowed to generate the necessary RPM, which means the REGULATOR is not the proper one.

For low power Hydro systems, the car alternator can not use the regulator it comes with, because it presents a too high current output which the battery tries to absorb BUT the hydro can not produce much higher power forcing the turbine to slow down and since the battery is loading the alternator, the load just allows the turbine to produce enough power to indicate that is being loaded down.

For small hydros with alternators it is best to have a regulator that can have current limiting to insure that the full power can ge generated and the hydro is now Bogged down by the battery load.

Can you test for this last item ( SIX ). ? - AND REPORT to me ?.

680 watts @ 14.4 volts = 47 Amps but the field current may be taking around 8 to 10 amps, so the output is around 37-39 Amps but the field setting is saying produce 80 to 100+ amps -- all depends on the alternator capacity.

Regards

Nando

[Flux]

I agree with Nando that you may be forcing the alternator field to saturation and using most of your available power. A separate dc switch mode regulator to the field would let you work with less field and core loss and higher speed.

Converting to pm would be better but you would have to match the speed power curve.

Work with Nando and I think you will get there.

Flux

[Flux]

If you want to make your own pm alternator I would choose a dual rotor axial type machine like they use for wind power here. With that type design you can alter the flux density by changing the air gap and you should be able to set the speed and load characteristics to match your pelton.

If you use a radial field machine you will probably need a buck converter to match the speed or play with belts and they are a source of power loss that you are better off without.

If you feel that you have the facilities to make your own alternator I will try to help but at that speed you will need to fix the magnets in a better way than relying on polyester resin.

Flux

[Sifis]

Nando,

I will give check the system this weekend and see what I can figure out.  I may need some additional info on how to find and or build a regulator that would be more apropriat for this system.

I will let you know what I find sunday or monday.

[Sifis]

Flux

I am not sure what a dc switch mode regulator is.  Where could I get aditional information or a diagram of one?

I am very interested in building a pm alternator.  I have a project involving another creek with very low head but much higher flow.  When I get this first unit figured out I will move on to the second one.

thanks

Sifis

[Nando]

please connect directly with me.

Nando

[hydrosun]

I was doing the same thing you are trying to do. I found out from Don Harris that I needed to use an alternator with an external regulator  (like the 70 amp motorcraft built in the 1980s), and then controll the field current with a heavy duty rheostat . I  once cut open an internal regulator and was able to insert a rheostat in the circuit, but it wasn't as efficient as the motorcraft.

Having said that I've now switch to the PM alternator from Harris as it produces 40% more power  than the car alternator. To me it was worth it to spend the extra money to be able to keep producing when the flow was much lower than the car alternator needed just in internal losses.  A lower price alternative is the fisher/paykel motor conversion from ecoinnovation.com or any of the wind generator designs on these pages, but I don't have any direct experience with these.

Chris

[Vtbsr]

I agree that the Harris alternator with the adj. field strength is the way to go. As you change nozzels and flow you fine tune the alt. speed with the field strength knob to get max amps. The waste heat from the alternator will keep the whole set up from frost problems all winter, if it is in a insulated box. With PM alternators i don't think you get that much heat. Another problem i see is the size of the penstock. The 1 1/4 pipe has to be undersized.  Reducing the pipe size down the length of 1700 feet only cuts the head. There is a misconception that reducing dia will increse speed of the jets, but it comes down to the pressure at the nozzels. With that length, 6 inch dia. would give you enough pressure to run the few small nozzels in the summer and get some output. Also what volt is the system? Your system should also heat  most of your domestic hot water by way of the diversion load system. Try to find a 80 gal  electric hot water tank. You can change the electric hot water heater elements 2500 w to 1500w. If you can't run the 1500 w with ac you can run it with dc to cut watts even more. 48 v system would cut it to 750w approx diversion load. Call Don and see if he will sell the parts you need since you have the wheel all ready. Try to get the white base with the stubs and nozzels, the alternater wound to your site paramerators. If you don't get all the shutoffs and plumbing you might get a better price.

[Sifis]

Hydrosun and Vtbsr,

It looks like talking with Don Harris may be the way to go.  It sounds like he may have some of the easier fixes for this site.  

I would like to find a good source for larger pipe  but am running out of luck.  Any suggestions would be apreciated. I am located in Oregon.  The 1 1/4 is the source of much of my problem.

As far as the different color bases on the Harris system, what is the difference?

Thanks Again for all the help.

[hydrosun]

I've used the 4 inch  pvc gasketed sewer  pipe as the lowest cost large pipe I could find.  Here in Washington State I found the lowest price at a local wholesale plumbing supply, Familian Northwest. It was cheaper than 2 inch poly pipe but needed to be better protected.

By keeping all the valves and final pipes and fittings insulated to the ground I've never had any problem from the lower heat given off by the PM alternator. I've upgraded several systems from the Motorcraft alternator to the PM alternator and people have loved the higher output and not having to replace brushes every few years. I mailed the pelton wheel to Don Harris and he mounted it on the new unit and accurately set up the nozzles. I feel the extra money for the better alternator makes the investment in the rest of your system  more effective.

Chris

[Vtbsr]

The white is for the regular car alternator. The green is Harris pm alternator. Don needs the head and flow and will wind the exact  specs for your site. You will not have to go through all the trial and error. For pipe you could go with sr35 drain pipe for the first part with low pressure. I was thinking  sch 40 pvc with couplings for the high pressure end. Maybe 4 inch might work but when you run the larger, the pressure will stay the same when you open nozzels. The yellow pages should have pipe supply houses. You could try used snowmaking pipe from a ski area. I found 1/8 inch wall  8 inch dia used irragation pipe in 20 ft lengths for $15. With steel prices high it might not be to cheap today.  Vtbsr

[roddy]

I have exactly the same situation (small creek with good gpm/decent head in winter, lower to none in summer I want to utilize but have been waiting until I own both sides of the creek, pleast keep updates if you get a decent solution.

Similarly I also have a large creek with high flow low head with serious potential I don't know exactly how to tap. any input would be appreciated. I am researching floating  raft style designs since making a dam here is not an option. The creek varies from 4' deep to rapid style in the 1000 ft. or so of bank I own, so I have plenty of places to experiment, just little time to do it. Please keep up posts..Thanks

Roddy