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Kris Harbour Natural Building avatar image
Kris Harbour Natural Building asked

MPPT Charging for Hydro. Victron 150v Blue solar not finding correct Maximum power point

Hi all. i have been running my off grid cabin on hydro for over a year now. i have been useing a tristar mppt controller and fixing the correct voltage in order to load the turbine correctly. this voltage is around 50v under load. That is the ideal speed to load the turbine to in order to catch the most energy from the water. that 50v equates to the turbine moving at half the speed of the water leaving the nozzle, this is the optimum relationship between nozzle volicity and rpm.


Now i have had lots of problems with morningstar and decided to try a victron blue solar controler. I planned on useing the mppt controler to find the best voltage instead of me needing to fix the voltage to 50v. I have plugged it in and at first i found that is would be all over the place and not find a voltage and stick to it. It would sometimes get close to the right voltage but then do another sweep and loose it again. I put this down to the fact that it is acting differently from solar and could do with some large capacitors to smooth it out. I have done this now and tested it and it isnt all over the place anymore but it thinks the maximum power point is at 30v and it simply isnt. The maths says it is at 50v. i have been using it for a year at 50v and that has giving me the most power. (I have done endless testing) But for some reason the blue solar controler seems to think the maximum power point is at 30v My question is why? and has anyone got an ideas? It will sometimes do a sweep and the voltage goes up and as it does the wattage produced goes up to. but then it just goes back to the 30v again. at 30v i am loosing alot of my efficiency because that relationship between nozzle velocity and rpm is off.


Thanks for any help.


kris

MPPT ControllersHydro and Wind Power
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lief ryan avatar image lief ryan commented ·

hi kris, old thread i know but i just wanted to say hello, just out of interest, does your turbine run at around 50v without a load? i have a hydro turbine that i made from a washing machine (i'm in tipi valley near Llandeilo, not far from you) but it runs at anywhere between 100 and 600v depending load, the way i get round that is by using a grid tie inverter that has a very high input voltage range.

all the best

Lief.

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markus avatar image
markus answered ·

Hi.

try to limit the MPPT charging current, to not overload and stall the turbine under the 50V Vmpp.

Best Regards,

Markus

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Kris Harbour Natural Building avatar image Kris Harbour Natural Building commented ·

But then i would be limiting the charging current. the whole reason for this post is because my system runs at over 70% efficiency so i cant just limit the charging current. because then i might as well just accept the large loss from the mppt not finding the right maximum power point

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markus avatar image markus ♦♦ Kris Harbour Natural Building commented ·

You said that you found out, that your turbine has a 50V Vmpp.

How many watts does your turbine produce when running on 50V?

What is the maximum charging current of your MPPT charger?

If your MPPT can do more watts than your turbine at 50V then it is possible for the charger to overload the turbine and brake it even under its Vmpp. Then the power is less at the 30Vmpp found, but the MPPT charger gives not enough time for the wheel to spin up to 50Vmpp again.

To avoid that situation, find out what the continuous power is, that your turbine produces at 50V.

Divide Absorption Voltage through max turbine watts and you get the Amp limit you should set in your MPPT chargers settings as max charging current.

When you have done that, the MPPT will not do a sweep at max power and therefore not brake the turbine down below 50V anymore.

Regards,

Markus

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tilo answered ·

Hello,

The fact that you said you had recently also trouble with the Morningstar controller could indicate maybe another problem. Just to discard this possible reason - now in summer there might not be enough water. This can be difficult to detect without a pressure gauge (manometer). I have seen a hydro installation where the owner and his operator were not aware that they did not have enough water, even though they did have a pressure gauge, but did not pay attention to it and/or did not know how to interprete the pressure.

Do you have a pressure gauge installed? How much is the pressure during operation, and how much when you close the tube (and have full static pressure)?

If there is not enough water, your feed stock tube will not be filled completely with water, then you have less pressure, and less water speed at the nozzle, that means lower optimum rpm of the pelton wheel, thus (correct) lower MPPT voltage.

When the MPPT sweeps quickly through the voltage range, it might just temporarily have more power because of the mass inertia of the wheel when it was running at higher speed and then reduces speed.

In case you don´t have enough water, you need to reduce the nozzle diameter.

Regards

Tilo


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Kris Harbour Natural Building avatar image Kris Harbour Natural Building commented ·

Hi Thanks for the reply, yes i have a preausre gauge and very aware of presure drop. i designed the system myself doing all the measurements its a 25.4psi system and i know when the pipe is draining by the presure gage and the output dropping. I can also see it at the intake by seeing if a have excess water. I can also see it by monitoring the free spin voltage. I have monitored it and used it to power my house for a year and a half so im very much in tune with it and i can tell whats going on with it by looking at those things depending on where i am at the time. I also know exactly what flow rate the nozzles do and what it is set at so i can tell by looking at the stream if there is enough water there.


The problem with the tristar controler is that they are not robust and tend to blow mosfets just when you do things like change settings. its a common fault with them and morningstar dont seem to want to change anything so im trying to trile another controler.

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