Very small hidro questions

[RodN]

Hello everybody, my name is Rodolfo I write from Italy

This is my first message.

Until I'm waiting for my data logger to collect wind-data for a year, i want to dedicate my time to a small hidro project for a site i have near my house.

The amount of water is very low, i suppose about 5-6 litres per second. The head is about ten meters.

So i should have a gross power of about 600 watt. In a year of almost constant use these are 5.100 KWh, that is more than a medium house consuming (3500-4000).

At the highest price in europe for electricity, about 12,54 Eurocent/KWh ($ 0,161), i will save about €500  ( $645  ).

Not enough for a trip to the haway islands, but enough to try.

The most important thing is that for saving money i have to connect to the main grid and use a "net-metering" option, making my electricity rotating in reverse way. It's an option provided by law only for renewable energy.

I wanted to use a small pump reversed as a turbine

Do somebody know how efficient are they?

As alternator i can use a small car alternator, eventually with a pulley to moltiplicate speed until it reach the 2.000 rpm needed, then transform the AC to 120-150 volts, then rectify it and give it to the main inverter.

I can't manage to find a suitable alternator or brushless generatore that is capable to produce even a very small amount of amperes but at high voltage and at low rpm, to do direct connection

So much work because for connnecting to the grid i have to use a validated (by utility company) inverter, actually the most economic one is the SMA windyboy or sunnyboy. It will be the only component i want to buy, and it costs over €1000, i can obtain the other pieces including pipes for no money.  The low voltage versions have not been certified

Any idea for improving my project will be very appreciated.

Thank you in advance and sorry for my bad english.

[RodN]

I forgot:

NET power will be about 420-450 W

[Countryboy]

Small pumps reversed as a turbine aren't very efficient.

If I were you, I'd look into a Banki turbine or a Pelton/Turgo style of turbine.

[RP]

Rather than a car alternator, consider a standard induction motor.  

If driven above its rated speed it will generate power back into the grid.  Going this route may eliminate the need for a certified grid tie invertor.

[vawtman]

Hi Rod

 That type impeller is very efficient at pumping water at high speeds 3250rpms.But in my opinion would be a bad choice for your project.The water flow would just avoid it.No expert and never tried backing them up,just work on em.

[vawtman]

Oh and forgot to mention that it needs its partner called the volute to make it work.the water is drawn into the center of the impeller.Thus the term centrifugal pump.

[Nando]

Rodolfo:

~ 1) 6 l/s and 10 meter head has a GROSS output of.

~ 2 ) 6*10*9.81 = 588 +/- and you may expect around 300 to 360 watts if you do not use the pump as turbine and if you do not use a car alternator as your power source

For your site of ten meter you may need a Turgo ( easier to make ) or a Pelton, then to use a Brushless permanent magnet motor as a generator, and NOT considering the turbine you may have around 200 watts using the car alternator and the idea of the turbine is not defined because the pump as a Turbine requires 30 % more volume that is capable of pumping as a pump and 20 to 38 % higher head than the head as a pump.

another problem is the car alternator RPM, that should be around 4000 RPM to lower the field current requirements.

RESULTS I expect to be quite negative.-- lossy idea

Nando

[RodN]

So, let's change it radically. At the moment i need a project or drawing of a turgo turbine. I know how it works, maybe i can arrange one using real inox spoons. The problem with this hi speed (of water) turbines (pelton/turgo) is that a little piece of grass or terrain can choke the final pipe. So i have to add a filterbefore the charging box, but that's not a big issue.

About the alternator, i assure you i searched all the night without finding a single site that explain how to convert a triphase motor to an alternator.

About a PMG brushless DC motor, can i use it without modification?

Thank you for your help.

P.S. good news: the owner of a small lake near the upper location gave me the assurance i can use the lake as a small reserve. That means that i can use the 6 l/s tho raise the level of the lake about 20 cm. During the rain i can put in the lake more than 40-50 l/s, extracting 10 l/s means that my "water bank" (i know the surface extending) will last about 2-3 month when i return to the dry 6 l/s.

So, in fact my water disposal has raised to 10 l/s

[Nando]

Rodolfo:

Once again, You need to define the "small lake", you need volume of the lake and what is the water volume that feeds the lake.

If you are going to have now "10 l/s" from the previous 6 l/s, then you have 4 l/s from the lake which is 4 * 3600 sec/hour * 24 hours = 345,600 liters/day = 345.6 cubic meter/day.

You new water reservoir NEEDS at least 350 cubic meters per day to keep up with your hydro.

Filtering of the water to remove small debris is not problem and you may have a much better system.

You can convert a small single or three phase motor as a generator, providing AC voltage right at the country GRID voltage levels.

Turgo spoons would be better if you buy them, or even buying the Turgo turbine, visit www.h-hydro.com or send a message to Joe Hartvigsen at joe@h-hydro.com and he may suggest the proper Turgo for your head and volume ( you need to define the motor for the RPM needed for the motor).

Make sure that you have the proper volume and head, define the volume for different seasons to determine the highest power -- hydro system definitions and the lowest volume to determine worse possible set up.

I could as well do the calculations for you.

This hydro power source is more productive than a wind mill with its wind behavior, so you should pay much more attention to it.

Nando

[alancorey]

Not to get off the subject, but what if instead of using the whole pump backwards, you discard the outer housing and aim nozzles at the vanes on the impeller?  





If you aim the jets of water where I've drawn in the yellow arrows it seems like it would be more efficient than trying to run the pump backwards.  Not as good as a real turgo or pelton, but a cheap and easy way to start.

  Alan