Choose a hydraulic micro turbine: Pelton or propeller?

[chatelot16]

the peleton has the best performance of any single turbine, but it has a big drawback for storage: it is not reverssible, we can not use the same thing to pump or turbine

I prefer a centrifugal pump with variable geometry, close to the Francis turbine

a centrifugal pump has a good performance in a fairly limited flow area: bad at low flow ... by simplifying a lot half the mechanical energy makes half the pressure by centrifugal force in the rotor, the other half of energy and given to water in the form of kinetic energy of the speed: this speed must be converted into pressure by the form of the diffuser, and alas for a simple pump it only works with one flow

with a variable geometry diffuser we could make a good performance pump with variable flow ... this principle is also valid in a turbine .... this diffuser transforms half of the pressure into speed so that the water enters the impeller shock-free ... and the centrifugal force in the wheel uses the other half of the pressure

the advantage of a turbine completely full of water and to take advantage of the entire height of fall even if the downstream level is variable, while the flap loses part of the height if the downstream level is variable

we built mill wheels below the downstream level in a chamber filled with compressed air to have an optimum level whatever the downstream variations, but it was bad because the water causes air, and we waste energy replacing air entrained by water

[izentrop]

The link you found says:

4) A turbine design allowing an efficiency of at least 50 to 60%

While all of Pelton's other sources talk about 85-90% efficiency ... it's a lot like a difference!

Yes, but these are micro-turbines on a low budget, it goes with low efficiency

Lilian07, 14l / s, you will need a large diameter of pipe and in less than 3 hours, your reserve is flared.

As the table is proportional (weird, Christophe is right), 12 mm of nozzle would make you debit 3 times less and therefore you expect to get 230 W.
I don't think it works like that. Navymar on the other forum has this type of turbine (it should be asked for confirmation) and produces 70 W max ??

If it is the same generator as the other ebay model that you had given, it is with permanent magnets. The inductive magnetic field being constant, at low power, it brakes and the efficiency decreases.

[izentrop]

https://hydroturbine.info/ give the elements so as not to be mistaken and it is not simple.
By the way 70 W is for more than 10 m http://www.onpeutlefaire.com/forum/topi ... ntry258741

[Christophe]

The efficiency of a Pelton is indeed around 85% (the highest efficiency for a turbine) but this efficiency does not take into account the efficiency of the adduction and other efficiency, injector, fitting ...

Yes at high injection pressure, therefore ejection speed, pressure for which the Pelton was designed ... Then we can play with the nozzles to increase the ejection speed but it is a bit of "DIY" in my opinion .

In short I am convinced that it decreases considerably in medium and low pressure ...

I do not know why you cling so much to the use of a pelton ???

As Izentrop says, it's not easy ...

[izentrop]

Transplanet market another micro propeller turbine for the smallest falls up to 2.5 m, but the output is even more abysmal: 500 w for 45l / s must be within 25%, while emptying the reserve to Lilian in 1 hour http://www.transplanet.fr/boutique/info ... ?num=16697.

Better to invest in a greenhouse whose water supply is all available

[Christophe]

Better to invest in a greenhouse whose water supply is all available

No compreho ???

Uh we would not divide this topic from the moment we talked about the choice of turbines?

[izentrop]

I drifted towards gardening where it could be a very useful reserve in case of drought. Water will become more and more precious in the future. 1/2 KWh it is not worth much from the network.

Ah yes, I saw that there is another subject on mini hydro turbines.

[Christophe]

Ok i understand

As long as we drift: in Corsica there are water reserves like that in the open air here or there ... very useful in case of fire (sometimes it's not enough: see the mega fire of July 23, 2010 ...)

Here I divided the 2 subjects, it remains clearer like that ...

[lilian07]

Izentrop, the table and in my opinion is consistent, the theoretical speed of the water which arrives in the pipe is equal root (2gh) ... for a height of 10m we already have root of 200 which gives 14 m / s we understand with the formula that the speed is not in linear proportion with respect to the height, hence the table figures which seem not to be consistent. You always have to come back to the theory and possibly imagine the feasibility even before having built a prototype ...
14 m / s of ejection speed on a section of 36mm (height of 10m) gives a cylinder of 36mm and a length of 14m in volume of water which passes every second in the pipe (V = 0.014 m3 / s or 14 l / s). we see that a bar is already a lot of pressure, enough to arrive with a theoretical speed of 14m / s that is why I take for my calculations 7 m / s (already fast enough to strike with kinetic energy the spoons of the Pelton).

Of course if this same section comes from a pipe taking water 100m high, we obtain a theoretical ejection speed of (root 2gh = 44m / s) which is not linear.

Why the Pelton simplicity (just a PE pipe) and cost (300 euros) in favor of depreciation in less than 4 years (allows with the injector inverter and a simple PV to reach 250W / H24), which is difficult for renewable energies.

[izentrop]

And then water is life, we can make it profitable in many other ways, crops, fish, ducks ... We can also make an oasis of biodiversity by developing gentle access slopes to avoid drowning.

Lilian, and the pressure drops? you did not see the link on https://hydroturbine.info/ ? The electricity recovered is euro cents.