A Quick Hydro History

Using falling water to do work has been around for a long time. How long? Since before Christ was a carpenter, before Buddha was a baby, before Mohammed knew his mom, before well, you get the picture.

Making electricity, from falling water, called hydroelectricity, has been around since the turn of the century. Since that time, there have been many improvements in both the wheels that convert the falling water to a rotary motion, called runners, and in the generators themselves. Most of the generator and runner design work was done long ago. Current manufacturers of microhydro equipment have built on what was already available, adding relatively minor improvements. Hydro system designers need to match the runner correctly to the hydro site and the alternator to the battery system voltage.

Hydro Primer

Every renewable energy site is unique, whether it's for photovoltaic, wind, or hydro. Within the scope of renewables, hydro is the most site specific. You probably can't make the hill any higher, or the water flow any more. In order to assess the site for small hydroelectric capability, there are four questions that need to be answered:

1. What is the head (vertical fall), from intake to hydro plant placement?
2. How many gallons of water per minute (gpm) will you be able to devote to hydro power? Keep in mind that water flow will vary from winter to summer.
3. What is the length, size, and type of pipe from the intake to the hydro plant?
4. What is the distance from the hydro plant site to the batteries?

The ES & D Stream Engine

The Turgo Runner

The Stream Engine is designed to operate over a very wide range of heads and water flows. The ES&D machine uses a Turgo runner to achieve this. The Turgo is a vertically shafted turbine-type runner with the nozzles pointed downward at a 20° angle from horizontal. The great advantage of this type of runner is its ability to digest a lot of water efficiently. This can give us the ability to use more water during peak winter flows. Depending on the head and number of nozzles, up to 300 gpm (1160 liters per minute) can be utilized. Quite an accomplishment for a wheel with a 4.5 inch pitch diameter!

The PM Field Alternator

The ES & D alternator uses sixteen strong magnets embedded in a top plate which is spun by the runner. The twelve stator windings are stationary. Electricity is generated by passing the spinning magnets over the stator windings. The output is determined by the right mixture of rpm, configuration of the stator windings, and the distance between the magnetic field and the stator.

The field to stator distance is adjusted by a bolt within a bolt arrangement, which lowers or raises the spinning magnets. The stator windings can be configured into parallel, series, Delta or Wye wiring. The windings terminate on three studs for easy reconfiguration. The studs are before the rectifier, so it's easy to take the output as a higher voltage three phase ac for long transmission lines.

This may be a little confusing, but either the manufacturer or your system designer will provide the machine with the right configuration for your site. The beauty of this alternator is in its high efficiency and lack of moving parts. Since no electricity is required to energize the field, every watt generated goes towards output. The three ball type #6203 bearings supporting the shaft should last for years. They should be available from all bearing distributors. The machine can be disassembled for bearing replacement in about 15 minutes on a workbench. A bearing press and properly sized mandrel are suggested for removing and replacing the bearings. Any machine shop can do this very quickly.

New Nozzles

Older Stream Engines had the nozzles threaded into the bottom of the 1 1/2 inch nozzle holders. The new nozzle incorporates both the nozzle and the nozzle holder into one molded plastic piece. The new nozzles attach to the housing with four stainless steel Allen-headed screws. An Allen wrench is provided.

The new nozzle tapers all the way down to a 2 mm orifice. To get the right orifice diameter for your site, cut the nozzle back with a hacksaw. There are graduated lines and markings on the nozzle to use as a guide. The cool thing about this arrangement is that the end user can create virtually any nozzle size from 1/8 to 1 inch (3 to 25 mm). Wring the last watt from that water source!

Documentation

The Stream Engine owner's manual is a wealth of information on hydro siting, pipe friction loss, nozzle flow charts, and overall system design. Unfortunately, there are no page numbers and no index. This makes it very hard to find specific information. Still, all of the information you need for a successful set-up is in there--somewhere.

Test Site

The Stream Engine was installed on Camp Creek in Northern California. Camp Creek is a gradually falling watercourse that can range from 20 cubic feet per second during winter runoffs to drying up in the late summer or fall. The total head is 31 feet. The penstock is about 900 feet long. From the top, the pipe consists of 6, 5, and 4 inch PVC. The 4 inch PVC branches to two 3 inch PVC full flow valves. The outlet of each valve is reduced to a 2 inch insert adaptor. Each adaptor is then connected to a 2 inch flexible rubber hose. Each hose is hooked up to a bell reducer, which decreases the diameter of 2 inches even further to 1 1/2. The two bell reducers are connected to the two nozzle holders. From there, it feeds into the hydroplant.

Warts

I'd like to see the nozzle mounting flange a little wider for easier access to the mounting screws. As it is now, almost all of the plumbing needs to come off before a nozzle can be changed.

The metal plate that covers the box containing the stator winding studs, rectifier, and output wire terminals is far from waterproof. Something with a gasket would be welcome.

As with all permanent magnet motor/generators or alternators, the maximum output is limited by the strength of the magnets. The ES&D machine uses very strong magnets but still maxes out at about 850 Watts. This is more power than most watercourses can produce. For those with greater potential, the standard electrically charged field alternator will go nearly twice as high. This is not really a wart; it's just a fact until someone invents stronger magnets.

Operation

Turn the water on. Aside from adjusting the air gap between the magnets and the stator, that's about it. Unlike a regular alternator, there is no need for a diode between the battery and the field windings. Should the alternator stop due to nozzle clogging, the output will just fall off to nothing. There is no chance of the field staying energized and actually discharging the battery.

Adjusting the air gap is a trial and error operation. It involves stopping the machine, holding the rotor with the provided pin, and loosening or tightening the bolt-within-a-bolt. This moves the rotor closer or further away from the stator. It's a case of making an adjustment, spinning the machine up, letting the water flow stabilize, and observing the ammeter. It may take a few tries, but once you find the maximum output setting, it will not vary unless you change nozzles.

Conclusions

This is a very cool machine. It represents a major breakthrough in microhydro design. The probability of going four or five years between maintenance shutdowns is a BIG advantage. Over most of its power curve, it will outperform a standard alternator by 15-30%.

During peak flows at my hydro site, I got 280 W from a Turgo driven alternator fitted with a specially wound stator for low head. With the new ES&D PM field Stream Engine, output increased to 325 W. That's a 15% increase at a less than optimum hydro site. Can I find a use for those extra watts? You betcha!