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Shaun0007

Off grid Home DIY project on river

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Good afternoon..

To all the electricians and solar fundies out there, I need some advise, help with a diy off the grid power project for our home

I am planning to build an off the grid electrical system using a home made water turbine which will be running on a river using a treadmill motor as a generator / alternator and up gearing to achieve the rpm needed to output anything from 12 to 24 volts DC.

From this it will go to a charge controller and charge the battery bank of say 2 x 12v 105 ah deep cycle battries..

I want to then run a 5kva pure sine wave inverter to supply us our electricity for our home.

This system is very much a like a solar panel set up, however it will not need solar panels to charge the batteries and unlike solar where it's dependant on the sun it will be charging the batteries 24 hours a day.

I have been doing alot of research on the internet on diy projects making off the grid diy waterwheels and wind turbines.

So I've got a good idea how I want to go about seting up this system, but need advise from someone who works with solar systems, electricians that have better experiance knowledge on the electrical side as in will I need to have a big battery bank?

Or any ideas or suggestions that may help me get this system running as well as possible.

Thanks









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Hi @Shaun0007,

Welcome to the forum. Personally, I would simply treat the watermill outpit as a type solar input for an inverter. You just need to match the voltage range of the generator to the input of the inverter. That may be tricky on a 12 - 24 volt generator output. Maybe a genny that produces 60 V would work better. Typically, wind gennies produce higher voltages, so maybe a better source. But one must use what one has. Even if you happen to source such a inverter, that would taken better care of the charging regime.

Don't fully discard the solar panel idea. I think it's a small price to pay, even just 2 x 400 W panels should be fine to start. So perhaps a 24 V system with 2 x MPPT's (one for the watermill genny and the other for future solar use) will ensure continuity in case the river does dry up.

I'm sure others will have better comments / ideas

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Shuan,

I red your "request"  If you are of the grid re think your complete house.  Led lights works on 12V therefore fit your house with 12V Led's lights. It is simple to get a 12V battery charger for solar charging the batteries.  Then go for a bigger solar charger and run your house lights on that.  For TV and so on you will use a DC - AC inverter and then rather use 250W panels.  That eliminates the need of an MPPT.  You get many types of 12 / 24V inverters.  You also get "smaller" inverters for TV ...

Thus when you rethink the possibilities this method will give you 24/7 lights ...   If you have a problem you can easy charge your 12V batteries with a set of jumper cables from your car.  Your car provides +/- 60 amp @ 12V.  Else you can get a 12V or 24V alternator (refurbished) for R600 and a nice petrol engine for +/- R 1900 from Turner & Morris. One pully and you have the best standby battery charger in the world.  This is a out of box way of thinking a lot more affordable and ...  My complete house works on LED's and a gas stove and  small inverter.  For the rest you supply your plugs with a 3Kwatt inverter.  That drives vacuum cleaners and dish washer.  This way the $ you save on MPPT's is worth it.
There is no more reason for 240V circuits for lights as LED's works on 12V DC actually the technical correct version is current that's important with 1 - 3V . 

There are many more cost effective methods.

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I think 2 x 12V 105 ah is too small for a 5KVA inverter. Shortcut: google some solar kits and benchmark their battery bank sizes. More correctly, reference the max current draw on the battery spec sheet and work out if you will exceed this when the inverter is at max power.

But before spending on the inverter & batteries, compare the turbine's actual generation capacity to the total daily loads in kWh, understand your baseload, and time and size of peak demand. Ask how much storage you need in kWh to cover evening peak needs until the turbine can charge the batteries again. Consider if you can expect the same output throughout all seasons and water levels. And if a treadmill motor is reliable enough for this application in the long run (no pun intended), or if you shouldn't just use it to supplement a solar system.

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I would definitely go solar and hydro, for redundancy. Drought or flood, the hydro turbine may not work, but will work in cloudy weather and at night. Solar works only in the day, but is cheap and robust. Mechanical things have minds of their own.

12V or 24V LEDs for lighting are very simple to set up and 2 105 Ah batteries should be able to drive quite a lot of them.

What do you want to drive from 220V? As that will dictate the size of inverter and batteries you will need.

Edited by DeepBass9

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8 hours ago, Erastus said:

rather use 250W panels.  That eliminates the need of an MPPT.

Not at 12V. 250W panels are usually either 60-cell or 72-cell modules, so Vmp will be somewhere between 30V and 36V. I know your stance on MPPTs... but in this case the loss would simply be too terrible to contemplate.

(Note: I did once see a 250W module that was made up of 2 x 18-cell strings... but these are rare).

A better idea, if you wanted to avoid the cost of an MPPT, would be to use a 36-cell module (Vmp around 18V). And even then the hit is still around 30%, but below 250W of PV the additional cost of an MPPT (iso the cheaper PWM controller) is usually not worth it.

If you wanted to use the trick of matching your PV modules to the battery voltage (and use a physical tracker to get the max out of it) you'd need a 30-cell module.

9 hours ago, Erastus said:

Your car provides +/- 60 amp @ 12V

Be careful. Alternators are often not rated to do this for long periods of time, at least not at low RPMs. You'd run into the same issues as when charging LiFePO4 batteries from an alternator. Alternators are also terribly inefficient (maybe 50%), though in an emergency you might not care.

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If you go 12V for lighting, think of setting it up as a ring feed type of system, where the batteries are in the centre and the lights on a circular cable. There is a lot of voltage drop using 12V so you don't want too long cables, otherwise you need to use quite thick cables. With a ring feed you effectively double the cable thickness and don't have some lights at the end of a very long cable.

12V is very cheap to set up. You can buy fuses switches and lights at Midas for next to nothing. Remember the fuses! 

Edited by DeepBass9

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5 hours ago, plonkster said:

Not at 12V. 250W panels are usually either 60-cell or 72-cell modules, so Vmp will be somewhere between 30V and 36V. I know your stance on MPPTs... but in this case the loss would simply be too terrible to contemplate.

(Note: I did once see a 250W module that was made up of 2 x 18-cell strings... but these are rare).

A better idea, if you wanted to avoid the cost of an MPPT, would be to use a 36-cell module (Vmp around 18V). And even then the hit is still around 30%, but below 250W of PV the additional cost of an MPPT (iso the cheaper PWM controller) is usually not worth it.

If you wanted to use the trick of matching your PV modules to the battery voltage (and use a physical tracker to get the max out of it) you'd need a 30-cell module.

Be careful. Alternators are often not rated to do this for long periods of time, at least not at low RPMs. You'd run into the same issues as when charging LiFePO4 batteries from an alternator. Alternators are also terribly inefficient (maybe 50%), though in an emergency you might not care.

If you give me the current and voltage ratings required I will provide you a modification to "do it correctly".  Any alternator can be configured to work from 12V to 110V ac.    It is very simple.

An alternator is a 3 phase ac voltage source of up to +/- 120V AC.  Thus if properly set up you can generate 110 V @ 110 amps ( what I have)  +/- 12Kw.  The AC frequency  is +/- 4 x rpm +/- 8000 rpm.  This is a very good device  to charge batteries with. If you buy an alternator you will find the GM ones are the best value for money and very close to the specs. It is proven technology and very few generators or in inverters matches that.
 

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On 2019/10/11 at 10:12 PM, Erastus said:

provide you a modification

Oh yeah I know... people modify these things to work as wind generators (ie higher voltage at lower RPMs), or even as motors for electric go-carts (for that you obviously need a VFD). I meant using an unmodified alternator from the auto-store. Many of them are designed with a certain (lead acid!) size and engine speed in mind. Watch the video. They had the windings hot enough that they started to smoke.

On 2019/10/11 at 10:12 PM, Erastus said:

An alternator is a 3 phase ac voltage source of up to +/- 120V AC.

The voltage is proportional to three things: Number of windings in the armature, strength of the magnetic field (ie design of the field windings), and the RPM of the engine (you can mess a bit with pulley-belt ratios to get this into the torque band of the engine). The more RPMs you stick on there, the faster it wears... so generally getting a higher voltage means rewinding the thing.

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Noe need to modify anything. You change the value of the regulating resistor. The resistor costs +/- R2. Like I said. An Alternator is a 3 phase 1120 - 120V "generator". The way the voltage is "regulated" is by changing the Voltage of the field coils that changed the size of the permanent magnet field if you wish and voila there is the output voltage.  Therefore if I increase the Vref resistor you go from 12V to 24 - 36 - 49  ........ 96.  What I have done is switch 1 12V switch 2 24V switch 3 48V.  It simply takes the resistor down to ground according to the voltage required.

One can even use it as a 3 phase 50 / 60 generator.  That is tricky though as it is difficult to get a good 50 / 60 Hz from it.

But in short no winding is touch.  I think you are over complicating stuff.  Keep It Simple & Streight.

Regards

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1 hour ago, Erastus said:

Noe need to modify anything. You change the value of the regulating resistor. The resistor costs +/- R2. Like I said. An Alternator is a 3 phase 1120 - 120V "generator". The way the voltage is "regulated" is by changing the Voltage of the field coils that changed the size of the permanent magnet field if you wish and voila there is the output voltage.  Therefore if I increase the Vref resistor you go from 12V to 24 - 36 - 49  ........ 96.  What I have done is switch 1 12V switch 2 24V switch 3 48V.  It simply takes the resistor down to ground according to the voltage required.

One can even use it as a 3 phase 50 / 60 generator.  That is tricky though as it is difficult to get a good 50 / 60 Hz from it.

But in short no winding is touch.  I think you are over complicating stuff.  Keep It Simple & Streight.

Regards

image.thumb.png.058b9bf95fb8c2b2e1d65838bb3ab411.png

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3 hours ago, Erastus said:

The way the voltage is "regulated" is by changing the Voltage of the field coils

Yeah, if you want to be pedantic, you change the CURRENT passing through the field windings. I'm also more familiar with the electronic regulator kind. My father's Bedford truck already had electronic regulation, good old Lucas electronics (!) from the late 60s 🙂

 

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Found a good article explaining it.

https://www.electroschematics.com/current-limited-alternator-battery-charger-control/

Thanks for the information! Never too old to learn. I know the modern regulators are sometimes even integrated into the ECU of the car, and they have freewheel pulleys on the front to ensure no overspeed when the regulator disengages, so learning about the old school way is cool.

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