Hydro-newbie questions

[mab]

Hi all,

I'm looking to into making a hydropower system at my new home. The stream falls about 30m (~100ft) and I'm estimating the flow at between 5 and 20litres/sec (~60-240GPM)  over the winter - I suspect it'll be a trickle in midsummer.

Having used powerspouts' calc I think there's potential for 0.5-2kw give or take.
Having used H-hydro's s/sheet I've got a net head of 43psi, and a Vjet of 24m/s = spoon velocity U of 12m/s, which for h-hydro's smallest (presumably cheapest) turgo wheel gives a shaft speed of 2700rpm.

I was hoping to do this as cheap as possible so I was planing on getting h-hydro spoons (or maybe a whole wheel) and making a genny myself.

1st  question: are my numbers in the right ball-park?

2nd Q: how do you figure no. / size of jets? (powerspout calc does give no. (1 or 2) and size, but I don't know how they figure it). Is it better to have more jets or one big one?

3rd Q: do you think an axial flux PMA similar to hugh piggot wind turbine is a good choice for efficiency? (I was thinking something with smaller mags and higher rpm - though 2700 rpm might be a bit too high. possibly use a larger dia. wheel? but that's more $$$ 

As an alternative, I do have a 2Kw 1PH (cap start) induction motor which I could use but don't really want to re-wind or fit permanent magnets, and I wasn't sure how easy it is to get it to self excite.

4th Q: If I have a system sized to provide 2kw when the water's there, how low will it go before shutting down? (if I have to choose, I'd rather have 0.5kw for 6-8 months than 2kw for 1-2 months).

Thx

Mab
PS. Has anyone every tried using actual spoons (like teaspoons) to make a turgo? I can get those really cheap.

[hydrosun]

your numbers are in the right ballpark, 50% efficiency would give you from  .6 to 2.4 kw.  harris hydro can be up to 70% efficient. I have seen regular spoons use but at a much lower efficiency. I'd stick to h-hydro spoons as the best low cost route. The smaller the wheel the faster the rpm. Higher rpm allows smaller alternators to put out more power. An induction motor can be tricky to get high efficiency in stand alone hydro.   I think it has to be rebalance for varied flow. Paul Cunningham of ESD gave up on that method in favor of permanent magnet alternators. Your rpm gives you the option of using stepper motors. the power spout uses a Fisher /paykel washing machine motor.  What you use  may be determined by your battery voltage and distance to your battery. Long distance is easier with a higher voltage.
With multiple nozzles it is easier to adjust how much water is used at different flows.  The maximum sise of the nozzle is determined by the size of the pelton buckets. Turgo allows bigger nozzles for the same diameter runner. A 4 inch harris pelton can use up to a 1/2 inch nozzles and th eturgo on the ESD can use up to ( I think 1 inch). 
Others will give you better info on winding your own alternator for this speed.
Chris

[mab]

Thanks Chris,

it is a good distance back to the house (~100m) so I was thinking 240/400v ish, then step down to 24v.

OK, so the induction motor is not a good choice then.  I'm just wondering how easy it is to make an axial flux generator that can hold together at 2700rpm. I suppose the good news is there's no need to use expensive neo's at that speed. 

[keithturtle]

Thanks Chris,
  I'm just wondering how easy it is to make an axial flux generator that can hold together at 2700rpm.

At the higher speeds the rotor balancing would become a significant issue, I would think.  There is a lot of mass there, and Hugh designed it to work well in the 120-400 rpm range.   If you want to use an axial flux dynamo design at that speed, you might be able to get by with much smaller diameter rotors and fewer magnets, I don't know for sure.

After all, doesn't a regular 3600 rpm generator head only have four poles?  That would only be four pairs of magnets in an AFD, no?

Turtle, still at it

[hydrosun]

you could use an induction motor and add permanent magnets for the rotor. I think that is what  is done on the garbogen wind turbine.
Chris

[mab]

At the higher speeds the rotor balancing would become a significant issue, I would think.

Yes; I would probably get a profesional to do it.

you could use an induction motor and add permanent magnets for the rotor.

maybe, but I might struggle with the engineering for that  - and would still need to keep the mags attached at 2700 rpm.

Realistically I'm thinking a larger wheel might be a sensible option.

[hiker]

any reason not to gear it down ?

[mab]

any reason not to gear it down ?

well, efficiency, for one, and simplicity for another - although, having said that,  it might be easier than building and balancing a rotor for 2700rpm.

I've found a pelton wheel for sale that might be suitable, with a dia of ~7.5" which would be 1200 odd rpm; I'm exploring that route (combined with a small dia axial flux rotor as Keithturtle suggested) at the moment...

thx

M

[dbcollen]

Why is induction out? I have been running an induction machine for quite a while now, and it has been 100% reliable. I have a 1hp 8pole 3ph motor running at 380v 90hz. I have 70gpm and 340ft head, my penstock is a little small at 2" but I have pushed it to 1400W. It has been running at 860W for the last 5 months continuous. it will go offline in the next few weeks due to lack of water. All you need for controls is 3 transformers http://www.antekinc.com/gview.php?d[]=0 a good 3ph rectifier and 3 motor run caps for the field.

[mab]

Why is induction out? I have been running an induction machine for quite a while now, and it has been 100% reliable. I have a 1hp 8pole 3ph motor running at 380v 90hz. I have 70gpm and 340ft head, my penstock is a little small at 2" but I have pushed it to 1400W. It has been running at 860W for the last 5 months continuous. it will go offline in the next few weeks due to lack of water. All you need for controls is 3 transformers http://www.antekinc.com/gview.php?d[]=0 a good 3ph rectifier and 3 motor run caps for the field.

It's not out entirely - but I'm a bit reluctant to re-engineer the rotor for permanent mags, or re-wind for 3ph and I'm generally unsure how to make it work at a speed that suits the pelton rotor, or if it'll work efficiently when I do get it working. Actually I was thinking of just trying the induction motor I've got (as it's there - I can always upgrade later), but it's single phase so would cause vibration - possibly damaging the pelton wheel.

I know I can make an efficient PMA and get it to work at the right speed (I think).

[dbcollen]

You don't need to modify the rotor, you magnetize the rotor with capacitors in paralell with the output wires. On my setup I run a 6uF cap on each phase for small nozzles, 8 uF for medium, and 8uF on 2 phases, and 8+6uF on the 3rd for high power. I use 600v motor run caps. Just be careful running unloaded, I get 1200vac unloaded.

[hydrosun]

Just curious about what efficiency you are getting with that set up. What is the running head at full flow? you said you are using a 2 inch pipe so you must be running at much less than 340. I know what efficiency to expect with permanent magnet alternators but have never seen good numbers for induction hydro into a battery bank.
Chris

[XeonPony]

If you look at my thread I had less water then you and I used an old hot tub pump as is to generate a good amount of power at 135V and it was a 230v motor

volume = voltage pressure = currentby controling the valve you can dial in any you wish based off the load. Naturaly the frequency changes with the speed so just keep that in mind

3600 rpm = 2 poles
1800 rpm = 4 poles

[mab]

your thread is very interesting Xeonpony - is the original pump motor single phase?

I've got this motor 2kw 1ph, L1 ~2.5ohm and L2 ~10ohm. don't know what it's nominal speed is - I could plug it in and check. Annoyingly as it was in a small garden wood-chipper, Health & "£$%^£$ safety have fitted some sort of brake mechanism inside the motor so I can't easily spin it up with another motor - not until I've opened it up and removed the brake.

m

[dbcollen]

What the hell is everyones hang up with efficiency, is too much power not enough? You have a free energy source, why do you need to harvest as much as you can? I find the excess power to be a nuisance, so I usually run smaller jets than I "could" because I don't need the power. My house uses 10kwh/day so 400 watts from the hydro is more than enough with the little the solar produces on cloudy days. I usually run with a single 8mm jet making 860 watts and still waste hot water from the dump load.

[joestue]

2nd Q: how do you figure no. / size of jets? (powerspout calc does give no. (1 or 2) and size, but I don't know how they figure it). Is it better to have more jets or one big one?

PS. Has anyone every tried using actual spoons (like teaspoons) to make a turgo? I can get those really cheap.

I built a turbine for someone in less than 24 hours a couple weeks back and i considered using teaspoons to get it done quicker (he was leaving the country that day)... but i instead cut a turbine blade out of a block of aluminum on my cnc machine.. rather than trying to cut slots in a disk and then mounting 12 teaspoons and trying to balance it.

On the number of jets, fewer nozzles is better when it comes to the nozzle efficiency.. but most of the time it is high enough that it is neglected.

so instead, optimize the number of jets for the spoons. its better to have too many jets than too few big ones imo.

[mab]

What the hell is everyones hang up with efficiency, is too much power not enough? You have a free energy source, why do you need to harvest as much as you can? I find the excess power to be a nuisance, so I usually run smaller jets than I "could" because I don't need the power. My house uses 10kwh/day so 400 watts from the hydro is more than enough with the little the solar produces on cloudy days. I usually run with a single 8mm jet making 860 watts and still waste hot water from the dump load.

The first rule of off grid living: efficiency, efficiency and more efficiency. 

Your point is very true of course - if I can get 500w continuous then that's more than I would know what to do with* - except that at some point in a dry year it's going to run out of water, and then getting every watt you can from it is desirable.

*there's a chance of getting a grid-tie system running here (still looking into it/ pricing it) - in which case every Kwh = £0.2 in the bank.

I built a turbine for someone in less than 24 hours a couple weeks back and i considered using teaspoons to get it done quicker (he was leaving the country that day)... but i instead cut a turbine blade out of a block of aluminum on my cnc machine..

Nice - but I don't have a CNC machine, nor a lathe, and I don't think I could carve a turbine by hand - but I do have an angle grinder and a mig.

optimize the number of jets for the spoons.

Would that be so the spoons are never idle? that's surely 1 jet per spoon! Maybe I'll just stick with 2 or 3 of different sized jets to cater for changes in supply.

Thx
m

[hydrosun]

The reason I ask about the efficiency is for marginal sites. If you always have a surplus it doesn't matter. Most of the systems i work on dry up in the summer. So it is important to have th emost efficient setup to not have to run a backup generator when the sun isn't shinging and th estream is only a trickle. My own setup can run down to 3gpm at 115 feet ehad and put out 30 watts 24 hours a day. that is important in the fall when th e stream is just starign to flow. And it is important to me in the winter to get the most output to be able to run a heatpump to heat the house so i don't have to start th ewood stove. I ask th equestion about th einduction motor for hydro so see if a lower cost motor can be as efficient as a pm alternator.  i would like to use the inductions motors. but I have never seen any numbers to show the efficiency is higher than 30% for battery charging.  i'm glad that the induction motor works well for you. But it would be nice to have all the information to be able to compare the options so a person putting in a new system can make an informed decision about cost versus output. I used a car alternator for msny years on my hydro. One of th ebest investments I've ever made was to spend the extra money to buy a PM Harris hydro. the higher efficiency.  for some people and some systems that is important. For others it is not. but if the information from others experiences is available they can make a choice. 

[XeonPony]

yup single phase and I was running it with a meer 95gpm at 20 psi dynamic head when it was cranking out the 356w is capable of 2 had I had an all 4" penstock

[dbcollen]

if you feel like running the numbers, 340ft static head, 8mm jet 1200ft of 2" polyethelene pipe, 860 watts into batteries

[mab]

OK, I've bought a pelton wheel - it's going to be ~1200rpm.

As a starting point I could try this induction motor; I can always upgrade to a PMA if I don't like the results.

If I understand this self-excitation process, I need a larger run cap for lower rpm? is that right?

XP: you appear to have quite an array of run caps on your motor - what sort of capacitance did you use (I can aim for that as a starting point).

I would be putting them across the main run winding (the low ohms winding) I guess.

thx

m

[dbcollen]

The only marginal time of year here is the fall, we have a few weeks of clouds and rain before I have useable water for the hydro. Spring is another matter alltogether, the hydro is still on and it is sunny and 80f. I use about 15 gallons of diesel per year and only in the fall.

[hydrosun]

i get a rough estimate of 34 gpm at 310 feet head and about 40% efficient. But it depend  on the actual pressure drop. it's good to know what is possible when adjusting the capacitor bias to see if different capacitors may put out more power. the 40% is higher than i've seen on other systems it's closer to what I'd expect with a well matched PM system so the lower cost  may make it the better choice in many systems.
from what I know the induction motor needs to a 3 phase motor to work as a stand alone generator. I've always seen the capacitors put accross the windings not connected to the output. is that correct?
Chris

[hydrosun]

i take back my question of needing a 3 phase motor. The 3 phase motors are ususally more efficient so are favored to be used as generators. But as Xeon pony shows it works fine using a one phase motor.  Just use what you got and see what you get out of it. If it is enough output for your needs then you're done. if it isn't you can experiment with other alternators.
Chris

[joestue]

optimize the number of jets for the spoons.

Would that be so the spoons are never idle? that's surely 1 jet per spoon! Maybe I'll just stick with 2 or 3 of different sized jets to cater for changes in supply.

i suppose its easier to visualize with a Turgo wheel, but if the jet is too big then you have water striking areas of the spoons where it isn't supposed to.

[XeonPony]

I started off with 200Uf then after tuning ended being 150.  I used 4 "25uf" and 2 "50uf" and then I had some 10's 5's to fine tune it.

Keep in mind I was running into the upper 2000rpm range, you may need larger or need to go at a faster speed, for your speed range I'd try to find a 1 to 2 Hp 1800 rpm motor.

[mab]

Thanks XP - that gives me a starting point.

I'll try spinning this motor up and see what I can get it to do but if it doesn't look like it'll fly I can always turn to another option.

At the moment I'm trying to find pipe for a penstock at a sensible price  .

joestue: - ah now I understand - THx

mab

[dbcollen]

If you are going to buy a motor go with a 3ph motor, try to find a 6 or 8 pole motor, the caps work fine at higher frequencies. just try to get the volts/freq ratio right (240v/60hz, 360v 90hz, 480v/120hz......) those are loaded volts, unloaded the volts can be scary high.

[XeonPony]

Personaly I find no advantage to using a 3ph motor, give me a good 4 to 8 pole single phase any day, way less head ach with capacitor to load/speed matching and way less conections to go wrong on you.

Matching the frequency to volts?!?! lol Once you are at rated voltage you will be at rated frequancy as the rpm will be "in the band"  frequency is irelivent with most switchmode suplies, my coffe grinder didn't care it was at 49 Hz nore did much ells for that matter.

As the above poster mentioned all ways have a balast heater hooked up!!!! When the puppies would turn the switch off for mine the volts shot to 208v! with the ballast heaters it hung at 135v nicely 

[dbcollen]

Since I have only been playing with induction hydro generators for a decade now, I obviously don't know what I am talking about so I will quit trying to give you misinformation. Carry on.....

[XeonPony]

Well you go ahead and get all bent out of shape becuase some one disagreed with you if you must, but rather petty in my opinion, just as was my preferance for single phased systems.

Sorry I'm not so good at being melow dramatic

(FYI I've knowen people that been in their field for life, and been doing it wrong for just as long, time in of it self is not a qualifier it is their comprehension of the facts and science behind it)

And to the Op remember a good heavy fly wheel makes life easy with any hydro system for smoothing out surge loads and such

[thingamajigger]

@dbcollen

If you are going to buy a motor go with a 3ph motor, try to find a 6 or 8 pole motor, the caps work fine at higher frequencies. just try to get the volts/freq ratio right (240v/60hz, 360v 90hz, 480v/120hz......) those are loaded volts, unloaded the volts can be scary high.

I have used both 3 phase and single phase 4 pole induction motors as generators in island mode as well as tied to the grid and found both work well.
Concerning the unloaded induction generator voltage, I simply rectified one leg, added a series inductance parallel capacitance (an LC filter), then a voltage divider or series zener diodes to charge the gate capacitance of a mosfet or triac to dump current to a dummy load. Another neat trick which is not really common knowledge is to switch in running capacitance in the same manner, I was using this technique in high load/ low power island mode applications where intermittent high resistance loads would siphon off too much reactive current and trip the generator. As well we can use parametric or cyclic switching to add an external current in phase to the generator current to compensate for low reactive current to maintain operating voltage.
I guess what I'm trying to say is that we do not always need to let the system do what it wants and we can design a certain amount of intelligence into the system with little cost to make it do exactly what we want.

Regards

[dbcollen]

it is a good distance back to the house (~100m) so I was thinking 240/400v ish, then step down to 24v.

XP, if you go back to the first page you will see the OP is charging batteries not trying to run hydro direct like you have been doing. I have found in my systems if you keep the volts/freq ratio near what the motor was designed for it runs cooler (more efficient)