Idaho farm microhydro

Posted by  Joseph Hartvigsen to the microhydro discussion forum on Monday, 04 Jan 1999 

We built a system using an ES&D 10 cm plastic pelton runner which I purchased through a local place.  The system is on the family farm in the mountains of south eastern Idaho.  My father had just put up a new house on the farm as his full time home when I started this. It is miles from power lines so we had to set up a system of our own.  He started with a Trace 2624SB inverter and 4 Trojan L-16 batteries charged by an 8kW Miller welder generator running on propane.  I am a bit slow getting the system completed.  The batteries gave out and were replaced last year with 12 large surplus 2V cells from a mountain top radio installation.  The generator is now 5 years old and is on its 2nd engine with 3000-4000 hours total time.  We have got some power from the hydro system but it is not delivering at full potential yet.

We started work on the hydro system in the fall of 95 when we put in the pipe.  We put in about 1/4 to 1/3 mile (0.4-0.5 km) of 6" (15cm) PVC to get about 92' (28 m) of head.  The pipe is buried at least 4' (1.2 m)deep, much deeper in a few spots to maintain grade. The first 20' (6 m) length is 18" (45 cm) diameter with hundreds of 0.5" (12 mm) holes.  It was put in a trench parallel to the stream and covered with rock for our intake structure.  This way we did not have to excavate or pour concrete in the stream bed.  When we were ready for water, a few shovel strokes (human powered) let water run over the intake and back into the natural stream bed again.  We then had a few lengths of 8" (20 cm) pipe and an air vent riser before going to 6" (15 cm) for the rest of the run.  Near the bottom the pipe crossed the stream under a culvert.  The pipe was terminated with a thrust block of 2 yards (~ m3) of concrete which also served as  the foundation and floor for a small (3.5'x4.5') powerhouse.  A 2" (5 cm) drain line extends out in line with the main line and a 3" (8 cm) riser comes up at one end of the slab.  Next to the riser, a 7" deep by 14" wide channel in the concrete floor directs the water back to the stream.  The battery bank and inverter are in an old military surplus aluminum "radar shack" near the house, 700-800' (230 m) away.  A direct burial #10 AWG 10-2-G cable was installed between the powerhouse and the radar shack.

I used a surplus 3hp 208V induction motor that I got free from work as the generator.  It is mounted on a ~18" (0.5 m) pedestal (shaft horizontal) to allow room for a nozzle above and below.  The shaft extends through a Plexiglas wall to keep water off the motor. The water comes up into a PVC cross.  A pressure relief valve and pressure gauge are on the top of the cross.  From the two sides the water goes out, up on one side, down on the other, out toward the generator then turns to the tangent of the pelton runner.  Most of the joints are glued but there are enough threaded joints to give 3 axis of motion to align them.  It stays 3" until the last straight sections to the nozzles reduces to 1-1/2" where it goes to ball valves and replaceable brass nozzles.  There are a few problems with this compared to a commercial ES&D turgo or Harris pelton.  I didn't get it exactly right so the two nozzle "arms" are parallel but offset about 0.5".  This makes the upper nozzle jet always hit inboard (motor side) of the splitter on the pelton runner.  The lower "arm" flow path (over-down-over-up) tends to collect debris until the nozzle plugs.  Alignment can be like taking a very cold, very strong shower (unless the big drain valve is open for 5 min first).

The pipe and concrete were done late 95.  I put in the generator, nozzles, pelton, etc.  and started it up late spring 96.  My brother in law was making a LCB (switch mode buck DC-DC converter) which he tried and fried on Thanksgiving Day (Nov) 96.  After a succession of failures he put in an old industrial 24V transformer based charger about Labor Day in 97, our first power to the batteries.  We just got 5A for a couple of months until it was discovered (about Thanksgiving 97) that the lower nozzle was plugged.  After cleaning and aligning the nozzles, he got 15-16A.  Then a new problem came up.  Due to my father's watt watching the batteries overcharged, the inverter shut off due to high voltage which only made it worse.  The charger had a regulator in it, but it was designed for fixed voltage input.  Here, as the regulator squeezed off the current, the input voltage would go up making the regulator work even harder.  My solution was to take the "window watcher" circuit in Home Power Magazine and have it trigger an AC solid state relay which would connect a load across the AC to put the brakes on the generator. The load was an old heating element from an electric clothes dryer which we mounted on the aluminum wall of the radar shack by the charger.  This worked until about this past Labor Day when the overworked regulator in the charger burned out.  We just need to bypass it as it isn't effective and only fights itself.

A little over a year ago I started looking into LCB type systems for my work.  We are developing fuel cell systems and want to control the fuel cell voltage.  We purchased two units from SunSelector.  They are nice but not quite what we need.  We had a consultant design and build custom units for us.  It is a two part design.  We have a control board that works for a wide range of systems and a power module which is made for the needed voltage and current.  The consultant had some left over parts when we were done and made me a control board.  I built a power module a blew it up about a year ago, and a few times since.  The consultant, in helping me with the farm system figured out problems which also affect our SOFC units at higher voltages.  We redesigned the board and are just getting the new ones.  It has fixed problems we were having with higher voltage fuel cell systems, and I expect it will work well with my hydro system too.  The hydro system is much more challenging to the electronics than the current fuel cells.  Our biggest fuel cell will be 100-110VDC while the 265VAC hydro goes to ~360VDC at open circuit.  It also has considerable kinetic energy to be absorbed as voltage (speed) is changed.  Otherwise, they both have a nice linear I-V curve and parabolic power curve.  I may test it on the hydro later this month.  It's a shame to have all that investment in pipe and trenching and still have to run the generator so much.

The nozzle alignment (and possibly the shallow bucket design) are hurting performance considerably.  There are two attachments which are both in acrobat format.  One shows my calculations estimating that power should be at least close to 800W at the battery (92' eff head 2 nozzles 0.5").  The other shows single (upper nozzle) performance.  This was measured AC across two phases with resistors at the radar shack.  Two nozzle OCV (freewheel voltage) is 265V AC. I didn't measure the I-V curve with both nozzles but of I cut the single nozzle slope in half and start at 265V I get a peak power of ~400W.  This is also the best power we have seen DC to the battery (16A).

I have built a 16 bucket turgo with "spoons" from Cargo&Kraft with a 15 cm hydraulic diameter.  I may get a chance to try the turgo runner in a few weeks.  I can send a jpeg picture if there is any interest.  I also have some pictures of old Sulzer turbines if there is any interest.

I'm curious how much a new ES&D bronze turgo might put out with this head and two 0.5" nozzles?  I also wonder if a permanent magnet or induction generator would be best for high voltage transmission?
Another design choice relates to AC vs.  DC transmission.  What are the pros and cons of AC->transformer, or DC-> buck regulator?  I've been doing some calculations recently on how to size transformers and choke filters if there is interest.  I have a list of resources on this I'll post separately.

Joseph Hartvigsen, ChE


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