Converting hydro output to battery bank

[GFruge]

Just checking to see if this is feasible at all. I have a hydro generator in mind that would work as supplemental energy at my site. Checked into Langston and others like it, but I don’t have that amount of flow.

The hydro generator is a 24v AC unit. My batteries are 48v DC.

I’ve found where I can use a full wave rectifier to change the AC to DC. After switching over to DC, can get a step up converter from 24v to 56v.

I’m willing to give it a try.

Then, my next question. I have the Growatt 6k inverter working with my solar panels. Should I get a growatt charge controller to tie it in together or get a midnight unit?

My site has a rainy season and I’d like to take advantage of it. I have 77’ worth of drop where I’d build a little water retention.

Is any of this worth it?

The unit I’m looking at below. I like the low water flow to produce energy. Limited around 200-300 watts, but that’s enough to supplement my needs. But even with the lower flow requirements, I can add a second or third unit.

Mini Pelton Turbine 200W | Turbin

Pelton Turbine Hydropower Full ready system for production up to 200W. Key Features: Portable hydroelectric turbine. Recommended for 100W operation with 80% usable load power on 12v & 200W operation with 80% usable load power on 24v. Work more than recommended only with your...

www.turbin.gr

My current setup is as follows:

* Growatt 6k inverter off grid unit, but draws from the grid if needed
* 5.3kWp Pv capacity
* (2) Lifepos4 batteries 12.8kWh total

Planning to add 1 more battery for more storage capacity during the rainy season.

 

[FilterGuy]

Just checking to see if this is feasible at all. I have a hydro generator in mind that would work as supplemental energy at my site. Checked into Langston and others like it, but I don’t have that amount of flow.

The hydro generator is a 24v AC unit. My batteries are 48v DC.

I’ve found where I can use a full wave rectifier to change the AC to DC. After switching over to DC, can get a step up converter from 24v to 56v.

I’m willing to give it a try.

Then, my next question. I have the Growatt 6k inverter working with my solar panels. Should I get a growatt charge controller to tie it in together or get a midnight unit?

My site has a rainy season and I’d like to take advantage of it. I have 77’ worth of drop where I’d build a little water retention.

Is any of this worth it?

The unit I’m looking at below. I like the low water flow to produce energy. Limited around 200-300 watts, but that’s enough to supplement my needs. But even with the lower flow requirements, I can add a second or third unit.

Mini Pelton Turbine 200W | Turbin

Pelton Turbine Hydropower Full ready system for production up to 200W. Key Features: Portable hydroelectric turbine. Recommended for 100W operation with 80% usable load power on 12v & 200W operation with 80% usable load power on 24v. Work more than recommended only with your...

www.turbin.gr

My current setup is as follows:

* Growatt 6k inverter off grid unit, but draws from the grid if needed
* 5.3kWp Pv capacity
* (2) Lifepos4 batteries 12.8kWh total

Planning to add 1 more battery for more storage capacity during the rainy season.

Hmmm... You are going to need some type of dump load to keep from burning up the boost converter.

When the batteries are full they will stop taking current and that means the boost converter will stop taking current.
When this happens the turbine will start freewheeling and the voltage will go crazy high. Likely high enough to blow out the input to the boost converter. In addition to the high voltage, the turbine is going to start spinning very fast. Your turbine probably won't blow itself up, but it will start wearing out the bearings. (Some turbines can actually spin so fast they tear themselves apart.... but they tend to be the larger ones.

You are going to need a load to divert the energy to when the voltage starts getting too high. There are some charge controllers that can facilitate this, but with the converter between the turbine and the charge controller, that is not going to work. You are going to need some kind of voltage controlled relay that can switch in the dump load when the voltage gets too high. The more advanced dump load systems use a PWM signal that is used to ramp up the energy diverted to the dump load as the voltage gets higher.

 

[Hedges]

I would consider stepping up the 24VAC to something above 48V. Then use a suitable charge controller.

Midnight and Outback probably have hydro curves. I don't know that voltage will be as wild as FilterGuy suggests. Wind would be, but hydro has fixed velocity water, and RPM of turbine should double with no load.
Midnight addresses dump loads called "Clipper" for their Classic. Ask the company about hydro application.

AC coupled, older SMA Sunny Boys had "turbine" mode, then called hydro boy or something like that. They recommended a regulator for wind but again may not be needed for hydro.

Just a suitable PWM regulator probably works. Maybe it needs a limiter.
Seems to me it could be good to have an alternator or generator with controllable windings rather than permanent magnet. But I think most are permanent magnet.

 

[GFruge]

Yes, I listed the 24v to 56v step up converter above in my posting. Wouldn’t an MPPT serve as the same purpose as the PWM?

 

[FilterGuy]

Wouldn’t an MPPT serve as the same purpose as the PWM?

The PWM we were talking about is not a PWM Solar Controller.



The simplest dump load controller will simply bring the dump load onto the circuit when the voltage reaches a certain level. If there is not enough difference between the voltage it turns on the dump load and the voltage it turns off the dump it can chatter as the dump load goes in and out of the circuit.

If it is a PWM controller, it will switch the dump load on and off at a reasonably high frequency, but at a varying duty cycle based on the voltage.
As the voltage starts going up, the duty cycle will be low so not much energy will go to the dump load. As the voltage increases, the duty cycle increases and more energy is dumped.... at some point the duty cycle is 100% and the dump load is 'fully' in the circuit. This results in a gradual increase in the dump energy as the voltage increases.

 

[GFruge]

Thanks for the diagram. It helps to give me a pathway to understanding a little more. But at the same time, please forgive my ignorance. I had my system professionally installed. Works like a dream and customer support is over-the-top for any question I ask. One guy tinkers with the hydro stuff, but everything he’s done was configured to work with the battery pack, like a 48v dc hydro generator that works with 48v battery pack. Plus where my system is installed, Central America, sometimes there language barrier doesn’t allow me to understand him fully when the technical stuff comes up.

So, please help me understand more about the dump controller. The attached website is what I could find that made sense. And I’m assuming a dump would just be a standard dump, like the attached photo of the green device.

Wind Turbine PWM Dump Load Controller - At TechLuck

Green Energy Forum, Solar, Wind, Turbine, Generator, Grid Tie Inverter, Off Grid, DIY, Thermal

techluck.com

 

[Hedges]

Yes, I listed the 24v to 56v step up converter above in my posting.

The hydro generator is a 24v AC unit. My batteries are 48v DC.

I’ve found where I can use a full wave rectifier to change the AC to DC. After switching over to DC, can get a step up converter from 24v to 56v.

That's DC-DC step-up, a switch-mode boost power supply.
What I meant was, since it is AC (of some frequency, will vary with load), I think a simple transformer would provide boost.
Need to know if the turbine has 3-phase or single-phase alternator.

But you don't have the turbine yet? Should be able to get one with 48V alternator, rather than stepping up. Although, may be difficult to find as small as 100 ~ 200W.

You have 77' of head. How much water flow, what range over the season?
I've imagined a turbine with multiple nozzles. One or two for lower flow, and when water in catch basin rises near the top a solenoid valve opens additional nozzles. That way a variable amount of flow can be 100% utilized, cycling between two flow rates.

The PWM we were talking about is not a PWM Solar Controller.

If it is a PWM controller, it will switch the dump load on and off at a reasonably high frequency, but at a varying duty cycle based on the voltage.
As the voltage starts going up, the duty cycle will be low so not much energy will go to the dump load.

The neat thing about PWM into a resistor, with a capacitor in the circuit (part of boost converter shown) is that the generator experiences a variable but constant load. It depends on the voltage across the capacitor, and that is almost flat, just a slight saw-tooth riding on DC.

That is unlike PWM SCC into battery, where PV panel sees alternately its Voc (no load) and Vbat.

If using a dump load controller, it would be nice to use a water heater as the dump load, so the energy is put to use. That would need a way to also switch to a true dump load dissipating to air if water heater gets too hot.

 

[houseofancients]

Hydro seems to work just about the same as wind..
That means you'll need an ac to dc rectifier, a "normal" mppt charge controller and a dumpload ( could be a waterheaters, or the grid if you have that)

 

[Hedges]

Midnight Hydro PWM

https://www.solar-electric.com/lib/wind-sun/kid-wind_hydro_frontBack.pdf

MidNite Solar The Kid MPPT Wind & Hydro Charge Controller With 1.0 Ohm Clipper

This controller is currently unavailable.

www.solar-electric.com

Midnight Hydro MPPT
I think this addresses using AUX relay to control dump load (likely requires separate power relay.)

https://www.homehydro.com/Classic%20Instructions.pdf

96A Midnite Classic 150 MPPT Solar Hydro Wind Charge Controller - 150VOC

www.bimblesolar.com

SMA Sunny Boy grid-tie PV inverters used to have an MPPT algorithm "Turbine" for wind and fuel cell (should also work for hydro.)
Only found in older models, prior to 2013

https://shop.solardirect.com/pdf/solar-electric/inverters/sb_install_SB50US-80US-IUS094030.pdf

https://www.postwick.co.uk/oak/Large_Files/WB25_30-11-FE0407.pdf

The Midnight and SMA units are good for multiple KW. Likely a small PWM unit would be better for a couple hundred watts.

 

[Hedges]

* (2) Lifepos4 batteries 12.8kWh total

With lithium rather than lead-acid, I think it is more important to use charge controllers that deliver steady current, not toggle between zero and max available like PWM solar charge controllers do. The PWM dump load switching at relatively high frequency would deliver steady voltage.

Otherwise, voltage of battery would shoot up when near 100% charge.
Could be OK if set for a voltage around lower part of knee, so battery can absorb full power (which isn't a lot with 300W turbine, anyway.)


Another thing to consider is failsafe. If dump load fails open, or other charge controllers fail shorted, the PV or hydro source continues to feed battery and drives it over voltage. There is a thread on this topic regarding SCC. If one fails shorted, the BMS tries to disconnect but voltage handling is exceeded and it shorts. Battery then over-charges and fails.

A redundant dump load or brake, simply a relay shorting the turbine, or disconnecting, could protect.

Some charge controllers like Midnight Classic use transformer isolation. If the switching transistors fail, it does not continue to charge.

An SMA branded charge controller from MSTE has an over-voltage signal to disconnect PV array for this purpose.

 

[GFruge]

But you don't have the turbine yet? Should be able to get one with 48V alternator, rather than stepping up. Although, may be difficult to find as small as 100 ~ 200W.

You have 77' of head. How much water flow, what range over the season?
I've imagined a turbine with multiple nozzles. One or two for lower flow, and when water in catch basin rises near the top a solenoid valve opens additional nozzles. That way a variable amount of flow can be 100% utilized, cycling between two flow rates.

This is correct that I don’t have the turbine yet. Didn’t know if this setup would be possible. The 48v systems you mentioned, require lots of flow, like 20gpm to make 300-400 watts. During the non-rainy season, I have a constant stream of 5-6gpm. But during this time, my batteries fully charge around noon, then idles down to maintain full charge. During the rainy season, wow, lots of rain water. Never wanted to stand out in the rain to measure, but it’s a lot.

My intention is to create a retention to collect the rainwater. From there, feed the hydro generator with a constant flow, but over a long period of time. For the larger unit, I’d get a short burst of energy while the rain is falling. With this smaller unit, it only requires 2.77 gpm to produce around 250 watts running on 2 nozzles. I have almost enough minimum flow year round to feed 2 generators. My 77’ drop and 2.77gpm according to their chart and conversations with the manufacturer give me 248 watts.

 

[GFruge]

With lithium rather than lead-acid, I think it is more important to use charge controllers that deliver steady current, not toggle between zero and max available like PWM solar charge controllers do. The PWM dump load switching at relatively high frequency would deliver steady voltage.

I have planned to run through a charge controller. Since my system is already setup with a growatt inverter, I figured I’d just add the same brand charge controller to tie it in together. And hopefully at the same time, it allows for more future expansion with anything else that I want to try like more hydro, wind, or more pv. Keep in mind that my system is in Central America. Most products are not readily available there as they are here. Almost everything has to be carried by me personally or imported with ridiculous duty fees.

https://signaturesolar.com/content/documents/GROWATT/1519003-specs.pdf

The 48120, farthest to the right is what’s available down there.

 

[Hedges]

Most charge controllers have a PV MPPT algorithm. May not work well with hydro input.

The hydro generator needs to be designed for your situation. In particular, head determines velocity of water jet (same as if you dropped a weight from 77'), and Pelton wheel buckets move at 50% that velocity (because impinging water turn around in opposite direction, leaving the bucket with about zero velocity relative to stationary earth.) That is a particular RPM, and alternator needs windings that work well at that speed and battery voltage (for PWM controller). I could imagine an MPPT controller that would run turbine at a different optimum RPM, but don't know if that functionality is available especially for small units. Midnight and SMA would let you program a fixed voltage, corresponding to a fixed RPM.

Big enough reservoir, you could toggle between operating (optimum turbine output) and off, based on water level. You could also disable turbine when battery voltage reaches some level, maybe 3.4V per cell.

There are Pelton, Turgo, and other wheels available if you want to build your own generator.

Aluminum Pelton Water Wheel for Micro Hydro Generator / Turbine | eBay

Find many great new & used options and get the best deals for Aluminum Pelton Water Wheel for Micro Hydro Generator / Turbine at the best online prices at eBay! Free shipping for many products!

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Amazon.com : pelton wheel

Some generators, I've read they custom-wind according to your water supply.
To DIY, you might select a suitable permanent-magnet motor. But that would be brush-type. What you really want is permanent magnet armature - an alternator, or BLDC motor with drive electronics removed.

 

[GFruge]

It’s currently rainy/fog season. 8am and this is what it looks like:

 

[GFruge]

I’ll contact the manufacturer about this comment, but it may perhaps be able to run on 48v. I’m assuming by the pattern that it’ll produce more than the 24v 200 watts.

 

[FilterGuy]

This outfit in Canada has a similar unit that can do 48V.

I used a 24V version at a mountain hunting cabin and was very happy with it.

Watter Buddy - Energy Systems & Design

Our Products Features Pricing Manuals Output Charts This little machine generates DC power from a source such as a stream running down a hillside. Water is channelled into a pipeline with enough drop (head) to build up sufficient pressure. It can also be used with water systems that are under...

www.microhydropower.com

 

[FilterGuy]

What size pipe do you plan on running from your catchment? Don't do anything less than 3". 3.5" or even 4 would be better. The pipe losses can be surprisingly high on a smaller pipe.

 

[Hedges]

Need more data than provided:

Mini Pelton Turbine 200W | Turbin

Pelton Turbine Hydropower Full ready system for production up to 200W. Key Features: Portable hydroelectric turbine. Recommended for 100W operation with 80% usable load power on 12v & 200W operation with 80% usable load power on 24v. Work more than recommended only with your...

www.turbin.gr

Graphs give watts vs. flow rate. But say nothing about head.

You can vary the flow through a given nozzle by varying pressure (head).
You can vary the flow for a given head by changing size or number of nozzles.

Water jet velocity is fixed by head.
Turbine efficiency is maximum when bucket velocity is 1/2 of water velocity.
Higher voltage for higher RPM.
If you connect it to a higher voltage battery, no load until voltage rises high enough, but some of the water's energy is wasted as velocity as it leaves the turbine.

Given graph of optimum voltage vs. head, you could better tell how it would perform.

The one FilterGuy provided has some of the data, power output vs. head. Watts vs. head for two different output voltages (just not a continuous voltage range.)

 

[DIYrich]

Control the water flow (bypass/spill way if you must) instead of a dump load.

Is it all on your property? Back up water onto someone's property? Run of river (down stream rights)?

 

[FilterGuy]

You can vary the flow through a given nozzle by varying pressure (head).
You can vary the flow for a given head by changing size or number of nozzles.

The watter buddy comes with several nozzle sizes to adjust the flow. Generally speaking, a higher flow will result in lower pressure at the nozzle due to pipe loss in the Weir.

One thing I just noticed is that they have changed the design at the turbine My unit had two nozzle ports but it looks like there is only one nozzle port now. I wonder what prompted the change.

 

[FilterGuy]

Control the water flow (bypass/spill way if you must) instead of a dump load.

I am not sure how that would work. It would need to adjust the flow based on the battery SOC.

 

[FilterGuy]

Generally speaking, a higher flow will result in lower pressure at the nozzle due to pipe loss in the Weir.

Just like a solar panel, a turbine has a maximum power point. You want to first find the maximum power point by adjusting the flow. As the flow increases, the power output increases but the water pressure decreases due to the flow through the weir. At some point, the pressure gets so low that the power starts decreasing.

Once you have the flow rate dialed in, the charge controller can fine-tune by adjusting the output current till it finds the MPP. This is where a controller with hydro curves for its MPPT algorithm comes into play. A typical dollar MPPT has a very fast search algorithm that is designed for a typical solar I-V curve. A water turbine usually needs a slower search algorithm with a turbine curve.

I tried a Victron MPPT on my 24V turbine and it made no difference compared to the old 'dumb' C35 I had before. I never spent the money on a controller that could do a Hydro curve so I don't know if it would have improved the output or not.

 

[Hedges]

Lost pressure due to higher flow had better not be significant. If it is, pipe is too small.
Pressure at the nozzle makes velocity, and turbine speed needs to drop water velocity near zero to extract all the energy.
Normally done by winding alternator for a given head and voltage. Controllable field winding would accomplish same, has efficiency loss compared to permanent magnet. Switcher (e.g. MPPT) could electronically match generation to battery voltage.

 

[Hedges]

I am not sure how that would work. It would need to adjust the flow based on the battery SOC.

PWM. Open a dump valve, or cut off water to turbine, when battery voltage hits target.

Diverter at nozzle could also do it. I understand large turbines deal with sudden load dump by turning nozzle away.
Small system, maybe open a solenoid valve to dump excess. Avoids water hammer compared to shutting off flow, but wastes water.

Can't do good linear control with a valve, that wastes power dropping pressure across valve.
Ideally would have an adjustable orifice nozzle, allowing water to back up in reservoir.
Maybe a needle motored into center of nozzle.
Multiple nozzles, turn each on/off to vary flow. Several diameters and it would be like a binary code.

 

[FilterGuy]

PWM. Open a dump valve, or cut off water to turbine, when battery voltage hits target.

Diverter at nozzle could also do it. I understand large turbines deal with sudden load dump by turning nozzle away.
Small system, maybe open a solenoid valve to dump excess. Avoids water hammer compared to shutting off flow, but wastes water.

Can't do good linear control with a valve, that wastes power dropping pressure across valve.
Ideally would have an adjustable orifice nozzle, allowing water to back up in reservoir.
Maybe a needle motored into center of nozzle.
Multiple nozzles, turn each on/off to vary flow. Several diameters and it would be like a binary code.

Seems overly complicated compared to a dump load with a pwm controller.