- #1
yahastu
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I am designing a hydro power system that will tie into an off grid solar system. I will be using a 48v carbon AGM battery bank. Will be using the Sol-Ark 12kw inverter/charger, which has 2 built in MPPT charge controllers for solar. Assume the hydro power will be around 5 kw potential, and the turbine will be located ~3000 feet away from the battery bank. The turbine will use an electromagnetic alternator (not permanent magnet).
Based on my understanding/research so far, it seems that there are 3 basic approaches that could be used to tie in the hydro power, and I'm a little confused about which approach would be best...
1) The conventional automotive approach. Use a three-phase alternator with built-in bridge rectifiers to convert the 3-phase AC signal into a bumpy DC signal, then the built int AVR help to smooth it out to your target voltage of around 12V, which is then directly connected to the batteries. I could basically do a similar thing but for 48V and connect directly to the batteries. It seems a big disadvantage of this approach would be the voltage drop...if the integrated AVR outputs 48V at the turbine, it's going to be too low to charge the battery due to resistive losses due to the long line length. Additionally, my understanding (which I'm not sure if correct) is that the AVR increases or decreases the strength of the electromagnet in order to maintain a desired maximum AC voltage under variable current load. Therefore, if the battery is fully charged and the current demand drops, then the alternator would spin freely at a higher velocity, potentially reducing wear on the turbine.
2) Same as #1 above, but instead of 48V, design it to output a higher DC voltage, which I run up to the battery bank. Being a higher voltage, the current will be less, and resistive losses will be less. Then route through an MPPT charge controller (eg, one of the 2x MPPT charge controllers built into the Sol-Ark, or an auxiliary MPPT) located nearby to the battery bank.
Note: I have heard that it makes sense to add a diversion load (ie, hot water heater) here to the MPPT controller to keep the turbine RPM in check. However, I am a little confused in the mental model here: if the AVR senses how much load and only produces enough current to meet demand, then how does that work when you add a diversion load, that can soak up an infinite demand?
3) Design the alternator to output 240v AC voltage, run this AC voltage up to the battery bank, then through an AC voltage stabilizer to correct for resistive losses...and then connect the output AC to the "aux generator"input of the Sol-Ark (normally intended for, eg, propane generators).
Related question: I understand that the turbine should be spinning at 50% of the water velocity for maximum efficiency (if it's free flowing with the water, then it provides no resistance and no power, and if it's 0% then it is stopped, also no power). Would the MPPT charge controller have the effect of essentially setting the turbine velocity to this most efficient point? If so, can someone explain how that works? I am a bit confused because if the AVR increases resistance in response to increased demand, what is to stop it from effectively creating too much resistance and stopping the turbine in response to huge demand?
Based on my understanding/research so far, it seems that there are 3 basic approaches that could be used to tie in the hydro power, and I'm a little confused about which approach would be best...
1) The conventional automotive approach. Use a three-phase alternator with built-in bridge rectifiers to convert the 3-phase AC signal into a bumpy DC signal, then the built int AVR help to smooth it out to your target voltage of around 12V, which is then directly connected to the batteries. I could basically do a similar thing but for 48V and connect directly to the batteries. It seems a big disadvantage of this approach would be the voltage drop...if the integrated AVR outputs 48V at the turbine, it's going to be too low to charge the battery due to resistive losses due to the long line length. Additionally, my understanding (which I'm not sure if correct) is that the AVR increases or decreases the strength of the electromagnet in order to maintain a desired maximum AC voltage under variable current load. Therefore, if the battery is fully charged and the current demand drops, then the alternator would spin freely at a higher velocity, potentially reducing wear on the turbine.
2) Same as #1 above, but instead of 48V, design it to output a higher DC voltage, which I run up to the battery bank. Being a higher voltage, the current will be less, and resistive losses will be less. Then route through an MPPT charge controller (eg, one of the 2x MPPT charge controllers built into the Sol-Ark, or an auxiliary MPPT) located nearby to the battery bank.
Note: I have heard that it makes sense to add a diversion load (ie, hot water heater) here to the MPPT controller to keep the turbine RPM in check. However, I am a little confused in the mental model here: if the AVR senses how much load and only produces enough current to meet demand, then how does that work when you add a diversion load, that can soak up an infinite demand?
3) Design the alternator to output 240v AC voltage, run this AC voltage up to the battery bank, then through an AC voltage stabilizer to correct for resistive losses...and then connect the output AC to the "aux generator"input of the Sol-Ark (normally intended for, eg, propane generators).
Related question: I understand that the turbine should be spinning at 50% of the water velocity for maximum efficiency (if it's free flowing with the water, then it provides no resistance and no power, and if it's 0% then it is stopped, also no power). Would the MPPT charge controller have the effect of essentially setting the turbine velocity to this most efficient point? If so, can someone explain how that works? I am a bit confused because if the AVR increases resistance in response to increased demand, what is to stop it from effectively creating too much resistance and stopping the turbine in response to huge demand?
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