Variable grid tie hydro?

[JSNH]

I have a brook that is 300 feet from the house, less if you cross the pond. The brook falls 45-50 feet into a small pond. From the top of the brook to the pond is 300'. I have a weir on the pond and have observed the flow for years. My state now has net metering and it is time to utilize this resource. Power often goes out and I have a backup generator. I would like to add 48 volt battery bank and a grid tie inverter. Current thoughts are an Outback.

Due to cost of this project I will likely spread it over more than a year. The brook dries up most years if it does this year I will do the penstock else the battery bank and inverter. I want to capture as much power as possible since I can back feed the grid.

The numbers

 45 feet of head.

300' penstock needed

Flow 50 to 800 gallons per minute

Flow 800GPM+ 6+/- weeks a year

Flow 400GPM to 800GPM 6+/- weeks a year

Flow 200GPM to 400 GPM 6+/- weeks a year

Flow 50GPM to 200 GPM 12+/- weeks a year

Some years as last year it never dries up.

I was thinking of a 6" penstock feeding a small turbine building with 3 identical permanent, magnet generators. With four 50 GPM nozzles on each I could vary the output from very low to max. I would also be able to add them one at a time and with all have redundant generators for low flow conditions. I have found some permanent magnet generators that are based on alternator cases and I have found turgo turbines also. I can put the pieces together cheaper than the premade systems that are available.

I am looking for thoughts and feed back. This is in the planning stage so I am very open to suggestions.

Thanks.

John Sokol

New Hampshire

[SparWeb]

Will you control the flow of the brook with a dam?  An arrangement of dam, spillway and penstock can give you a steadier flow of water (as long as there is any water).  Creek flows are usually variable, unless you are downstream of something else that controls it.  You could reduce your need to adapt to variation of the flow (which seems to change ten-fold over the season) and then just build one generator.

If the chart I have is reliable, then 300' of penstock 6" in diameter will only cause a 1-foot drop in hydraulic head.  Joints and bends will reduce the head further.  You can still count on at least 1kW of hydraulic power available at the nozzle.  I think you will need a 1" nozzle, probably more.

Here's a reference guide: http://www.goulds.com/pdf/TTECHWP.pdf

There are many examples on this forum that can help you see how it can be converted to electriticy.  My impression is that converted motors is the way to go - but that may not be the consensus.

Good luck.  Let us know what you decide!

[Darren73]

Hi John,

If you are going for a grid tie system then the most efficient method would be to use an induction motor and run it above slip speed, there have been a number of similar posts on here over the past few months, use the google search and you should find the info you need, it also means you can meet the codes for grid tie without having expensive grid tie inverters.

Regards

Darren

[Chagrin]

You might also take a few minutes to contact the DNR in your state to verify that this type of waterway obstruction is permissable.

[Flux]

That was my first reaction Darren, but he probably doesn't want to loose power when the grid is down so the batteries may be a better but far more expensive route.

It still could be done with the induction motor but he would need exciting capacitors and a load controller and the hydro would need to be capable of supplying all the load without battery assistance.

I agree that he has more options than he proposed.

Flux

[thefinis]

You are wanting to capture the water flow above the pond? Do you have the needed setup where it will start/enter the penstock and are you dumping the outflow into the pond or down the creek below the pond?

Heh heh it is often better to ask forgiveness than ask permission when dealing with the gov. Not saying you should knowingly break the law just that it might be better not to ask if it is okay.

To start with I would try going with 1 turbine and 1 genny an induction motor one would be nice (almost said easy) and just grid tie it. If you go net metering try and get it for a year not a month as your water is only there for part of the year. If you already had the battery bank and the inverter or if you were trying to go off grid it would be a different story.

Good luck

Finis

[JSNH]

I want to capture the water above the pond. The penstock intake and line will be work but not too bad. The slope is steep but ok for the backhoe I have avaliable. It is nice to look out at the pond. By passing the pond would only gain 6 feet of head and add 200' of penstock. Our net metering law was just changed to allow yearly banking of excess before it was monthly. Any excess produced in a month went to the utility for free now it can be banked for a year. I run two households on one meter and the goal is to replace as much as possiable since the grid power is around $ 0.15/KW. About 700KW a month for usage. Sounds bad for usage but two households and a lot of welding and wood working tools and wood forced hot water heat it is ok. So 250 watts output would be 25% of the normal usage. The peak flows if captured would provide well. Back up power is a concern. My back up generator is not reliable and power goes out often sometime for days. I would install one turbine at first but have the penstock sized for more and have room for more in the turbine building. All comments and sugestions are appreciated. I will look into an induction generator for the peak flows it might be easier than the way I was thinking.

JSNH

[thefinis]

Yearly net metering makes it so much better. I didn't do the math but 200 ft of run would have eaten much of the extra drop and a nice pond is well worth keeping pretty and full.

I would get in touch with Nando when it comes time to build both for ideas and water wheel parts.

Have fun

Finis

[Darren73]

Hi Flux,

I did miss the part about poor grid reliability, depending on how much of the power John needs as 48Vdc maybe a mix of grid tie induction and off-grid 48Vdc generation would be the better fit from a cost and efficiency standpoint.

John,

How much power would you be looking for as backup when the grid fails? if it is only for essentials then it may be worth you considering the option above.

The more information you can provide on this the more accurate the options posted can be to your requirements.

Regards

Darren

[JSNH]

Hi Darren. The back up I have now is a 3,000 watt Onan and it provides enough for everthing without the workshop but it has 4,000 hours on it. I purchased it used for $50 8 years ago. So 3,000 watts is a good number and an Outback will do that. That why I was thinking Outback. My neighbor is off grid with solar and hydro. His hydro went on line late last year and has worked well but his location is vary difficult compared to mine. I have been looking at that brook for years it it time to put it to work.