Micro Hydro

[Tim in Oregon]

I am building a micro-hydro system in Western Oregon and need some advice from some of you who have more experience at this than I do.

The stream has a flow rate that varies between 900 and 3,000 gpm depending on the season.  There is 26 feet of gross head over a horizontal distance of 300 feet.  I am planning to divert approximately half of the creek's flow using an 8-inch pipe.  The system will supply power to single family residence and will be grid-tied, if I can obtain the necessary permits and permissions.  I have done preliminary power calculations and have an idea of how much power can be generated.

How does one regulate how much water passes through the turbine without simply constricting the flow with a valve?  I want to be able to adjust the flow to take advantage of the higher flow rates during the rainy seaon when the household electricity demand is the greatest. I am not sure how this is done.  I suspect is may depend on the type of turbine used, which leads to my second question.

I am planning on purchasing a turbine. There does not seem to be a large selection of manufactuers or products to choose from.  My application is relatively low head and high volume, so it seems like pelton wheel models would be out of the question.  Should I be looking a crossflows (such as the Stream Engine) or turgos (like the Nautilus)? Can you recommed a suitable turbine for my application?

My final question has to do with power regulation. Since I am planning a battery-less grid-tied system, I will use an AC generator.  Is there an off-the shelf power electronic device that will regulate the output voltage and frequency?  How does one regulate the loading of the generator in such a system?  Is there a device that optimizes the loading?

I would appreciate help with any or all of these questions.

Tim

[Nando]

Tim:

You have your ideas but you did not inform what have calculated.

Also, clearly you indicate that you are not familiar with the hydro electric work and the mechanics of it.

Using 1/2 of the lowest volume you can obtain Gross 2.2 kilowatts or about 1.32 Kw after all the equipment losses.

In winter using 2/3 water ( 2000 GPM) you may obtain around 6 KW.

For this low head and high variable volume a BANKI OR CROSSFLOW TURBINE is the best arrangement with RPM multiplication for the generator,

The Stream Engine or Nautilus may not be the proper ones.

Please indicate the web page and the models you are referring to.

Volume regulation is done with the nozzle size that limits the volume but keeps the water velocity at its maximum.

There are ELC ( Electronic Level Controller) that keeps the generator producing the proper voltage and as well the frequency if that is necessary.

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Since you are GRID tied you could use the GRID to set the operating parameters of the hydro and feed the energy back to the GRID ( maybe you can get paid for such arrangement), In this case you use an Induction motor as a generator -- cheaper idea.

If in case that the GRID drops , like in Winter , then an additional circuit is needed to produce energy isolated from the GRID.

Something like above indicated ( the same Induction Motor) is producing energy but a set of capacitors are needed to make it to produce power and with the ELC you have a stable output voltage.

I can assist you in this project.

Nando

[Tim in Oregon]

Nando,

Thank you for the swift and informative response.  You are right, I do not yet know a great deal about the mechanics of hydroelectric power, but I am eager to learn from you and others.  I am a second-year student studying Renewable Energy Engineering at the Oregon Institue of Technology.  I have taken courses in fluid mechanics and elecrical power; but I know very little about small hydroelectric turbines.

Your statement about regulating the flow through the turbine with nozzles makes sense to me.  I remember studying how larger Francis turbines have guide vanes in the scroll case that adust the amount of water flow. I was hoping for an easier way with very small turbines. If I understand correctly, in very small turbines you must shut down the system and physically replace nozzles to change the flow? You cannot adjust the flow while the system is running?

The results of my power calculations for 300 feet of 8-inch PVC Pipe and 26 feet of gross head are:

At 500gpm, the effective head is 24.5ft, the power output is 1224W (882kWh/month).

At 1000gpm, the effective head is 20.5ft, the power output is 2053W (1478kWh/moth).

At 1283gpm, the effective head is 17.3ft, the power output is 2223W (1600kWh/month).

These calculations take into account major pipe losses, but not minor losses.  The addition of pipe fittings to the system will reduce the power output from the numbers shown.  I am assuming a combined efficiency of 50% for the turbine and generator. I did not do calculations above 1283gpm because 1283gpm is the optimum flow rate for an 8-inch pipe, above which additional flow does not result in increased power output. I also did calculations using other pipe sizes (6-inch and 10-inch).  I am willing to use the size that makes the most economic sense.

I am planning a grid-tied system because here in Oregon we can sell back to the utilities as much power as we use during the year.

I have only started to investigate turbines.  From what I have read, Banki crossflow turbines are ideal for low-head, high volume applications, but I have not been able to find a single manufacturer of small Banki turbines in the United States.  Would I have to build one from scratch?

The idea of using an induction motor for a generator is very interesting to me.  I would very much like to learn how to do this.  

Thank you, Nando, for taking the time to answer my post and share your knowledge. I am eager to learn from you.

[Nando]

Tim;

Send you email address to me, directly, correct the anti-spam protection in my email address, to discuss turbine alternatives.

First error:

The head variation is a problem and one needs to design the system to have minimum head loss at maximum volume, therefore from low to high volume the head loss should be minimized otherwise the Turbine RPM will vary too much and energy generation problems when producing AC power.

Forget the monthly production it does not enter in this small system design, you are not storing energy in a battery bank.( though you are in the GRID system)

Your decision on the pipe size to optimize the power in winter is the important thing, and the possibility of having local power if the GRID drops due to emergencies.

10 inches pipe may be the one you need to have the peak power in winter is such is what you want.

Even a marriage of 10 and 8 inches, you have 300 feet of pipe run, and very low head, so even sewer pipe and or smooth surface drain pipe will do to save a lot o money, of course minimized the couplings and change of direction.

The electrical aspects are simple in this case when connecting to the grid.

Nando

[Ungrounded Lightning Rod]

If I understand correctly, in very small turbines you must shut down the system and physically replace nozzles to change the flow? You cannot adjust the flow while the system is running?

No reason to shut it down to adjust it just because it's small.

Another approach for some turbines (such as peltons) is to have multiple nozzles at various locations around the wheel and turn on as many as you need for the flow you have available.

Not applicable to crossflows, of course.  For those an analogous method would be to have several sections axially, with plates dividing the nozzle and disks dividing the rotor, and turn each section on or off separately to use the available volume without sucking out the head.

For large water supply variations you might make the divisions binary sized rather than identical to save on valvage.  B-)

On the other hand, adjusting the width of the nozzle when in use isn't all that hard a job, even on a small turbine.

[sunshynnn]

Hey Tim,

I'm in western Oregon, also, and new to the discussion board.  I am researching the feasibility of a micro hydro system on our very rural property in Yamhill County that is bordered by two year-round creeks.  I would really be interested in hearing updates on your project, seeing it in person, and talking with you about the general steps you have taken to plan your installation.

You can email me at sunshynnn (at) gmail.com, if you'd like.

I look forward to hearing about your progress ... best of luck to you!

Janine