Improving an old off-grid system

triplem

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Joined
May 14, 2022
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7
Good afternoon,

We bought a small piece of land a few years back (in France). We'd like to improve the system, and we have some questions as we are new in this

Here is what we have so far

Input
- 1 wind turbine (no ref)
- 2 solar panels (no ref)
(Both are up a metal tower, we'll need to climb up there, but aren't equipped yet to do it safely, so we don't have any ref)

Storage
- We have 2 CPM12 solar charge controller (1 per panel)
- 1old controller for the wind turbine (no idea for the reference its a very old one in an old metal box)
- We have 4 batteries in series (each are 6v) so 24v out.

Output
We have:
- a small wood cabin 20 meter from the installation
- a small barn at 100 meter from the installation

But we only power 24v lightbulb that's it, we'd like to improve the system to plug more appliances.

Here are our thoughts for the system with our questions.

Input:
- We'd like to gather production data (how much our solar panel and wind turbine produce per day)
- Have a single charge controller (for both the solar panel and the wind turbine)

Is there a controller that can do this ?

Output:
- We'd like to plug some powertool in the barn for light wood's work. So we are looking for an inverter 24v -> 220v and around 1.5 kW - 2kW.
- The inverter would only be used while doing the work, then it will be removed and stored away.

Are there good reference for such inverter ? What should we avoid ?
Are there inverters that can be switched on forever ? or is it better to switch it on/off as necessary ?

Last question: is there a necessity to have a 24v system instead of a 12v ?



Thanks for your time and consideration.
 

12VoltInstalls

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Is there a controller that can do this ?
I’ve seen combo units. They exist.

But why? I’d keep them separate because inexpensive quality solar charge controllers are readily available. The wind controller not as much
What should we avoid ?
modified sine inverters. Get pure sine wave
Are there inverters that can be switched on forever ? or is it better to switch it on/off as necessary ?
yes but you do get some loss. Unplugging or turning off while not there makes sense.
Last question: is there a necessity to have a 24v system instead of a 12v ?
It’s not necessary.
around 1.5 kW - 2kW.
This will work on 12V

I’m thinking you’ll want a few more panels. I’d be inclined to use 12V but then again what will be your daily consumption in watts?
And it sounds like you have 24V already?
 
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Rednecktek

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On a boat usually.
I'll post my stock blurb here in a minute, but first here's a couple thoughts:

- 2 solar panels (no ref)
(Both are up a metal tower, we'll need to climb up there, but aren't equipped yet to do it safely, so we don't have any ref)
You can get a pretty good clue of what those are from the ground with a multimeter and read the volts between the + and - wires from the panels. Then put your meter on DC Current and connect it between the + and - and see what kind of amperage you get. That will give you a pretty good idea of the VoC and the Vmp. Multiply the 2 and you'll get a pretty good clue on what the wattage of the panels is.

We have:
- a small wood cabin 20 meter from the installation
- a small barn at 100 meter from the installation
Those are going to need either some pretty hefty wire OR you're going to want to get your inverter and AC setup close to the panels and pipe it as AC from there. DC is less forgiving of wire length than AC.

Input:
- We'd like to gather production data (how much our solar panel and wind turbine produce per day)
You'll need to get a shunt wired into your battery bank that can track the wattage over time to be accurate. Not difficult.
- Have a single charge controller (for both the solar panel and the wind turbine)
I've seen pictures of them on the interwebs so they must exist. I can't definitively state how well they work. You're probably going to want separate solar and wind setups and just parallel them to the batteries. I do know that the wind is going to require some sort of dump load or braking mechanism to not destroy the turbine.

Output:
- We'd like to plug some powertool in the barn for light wood's work. So we are looking for an inverter 24v -> 220v and around 1.5 kW - 2kW.
Power tools, and anything with an electric motor, have 2 power draws. The first is the startup surge current which can be upwards of 3-5 times the Running current of the tool. Are you familiar with the difference between High and Low Frequency inverters? High frequency inverters are smaller, lighter, cheaper, and more efficient than Low Frequency, but their "Surge" time is usually in the milliseconds and not long enough to spin up a power tool very well. Low Frequency are designed to handle a much greater startup surge but are heavier and more expensive. If you're able too you might want to think about 2 inverters, 1 for power tools that only gets turned on when you're cutting lumber and 1 nice efficient high frequency for the lights and espresso machine and such.

Are there inverters that can be switched on forever ? or is it better to switch it on/off as necessary ?
While there is a bit of draw when it's idling, it's often not worth the hassle to fumble around turning the inverter on when you just want to watch TV. At best disconnect it when you leave and turn it back on when you arrive.

Last question: is there a necessity to have a 24v system instead of a 12v ?
Necessary? Not at your loads. Beneficial? Yes as a 24v system will allow for more inverter capacity for things like the power tools and hot plates and such without needing freakishly large wires and fuses.
- We have 4 batteries in series (each are 6v) so 24v out.
Remember that with lead acid based batteries you can really only discharge them to 50% before you start to damage them, so your battery bank (assuming it's still 100% good) is only good for 215Ah @ 24v or 5160Wh.

OK, on to my standard blurb. :)
 

Rednecktek

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On a boat usually.
Well, I'll start the default answer to these questions and we can work from there. Here's you To-Do list:

1: Power audit! This will give you some important information on how big your inverter needs to be as well as how much battery capacity you'll need. There is a link in the FAQ section (I think, or someone here will post it shortly) so fill in the blanks and see what it comes up with. You'll probably need some sort of Kill-A-Watt to get accurate measurements. Are you going to be running a 12v system? 24v system? 48v system? What are the specs on your solar panels? VoC? Vmp? Being as this is a new build, throw together a wish list of what you want and estimate on the high side.

1a: Where do you live? Speccing out a system for Scotland is a LOT different numbers than Arizona due to the amount of light you actually get. Someone here can post the link to the PVwatts.com or JCR Solar Uber-Sun-Hours calculator sites to help figure out how much you'll have to work with. That will be a box in the Power Audit form.

2: Parts list: You don't need a make & model list, just a parts list to start from for reference. You'll need an inverter, a MPPT charge controller, fuses, shunt, buck converter, batteries, wire, etc. Once you have a basic list it can be fine tuned to make & models after that. If you're looking at the All-In-Ones check for correct voltage outputs (120v or 240v Split Phase for North America, 220v Single Phase for European type areas) and make sure it has enough capacity for a little bit of growth and fudge factor.

3: Budget!: Steak is great but doesn't mean anything if your wallet says hamburger. :) Figure out what you're able to spend now vs what you'll have to cheap out on now and upgrade later.

4: Tape measure! Figure out where you're going to stick all the stuff you'll need. A dozen 3000AH batteries sounds great until you're sleeping on the floor because there's no room left for a bed. Is there a compartment that can house all this stuff? Will the server rack batteries fit? Are you going to have to make space? Physics can be pretty unforgiving.

5: Pencil out what you think you need and throw it at us so we can tell you what you've missed (because we ALL miss stuff the first go-round :) ) and help figure out which parts and pieces you're going to want to get.
 

MichaelK

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Mar 21, 2020
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For a cabin, I'm more inclined to keep 24V instead of moving to 12V, and at 24V there are many more QUALITY components then what you can find within the 12V market.

As RNT recommends, get a sine-wave inverter, then you can power any household appliance you purchase at your regular retail store. As a general rule though, AC results in higher power consumption then DC, so you need to scale the system up appropriately.

That's no big deal these days because solar panels have become far, far cheaper than they were just two decades ago. In France, I assume you have some local marketing venue comparable to the American "Craigslist". Here in the US, shopping for panels locally with local pickup gets you far better deals then online purchasing, with shipment. That's a lot of glass, which is expensive to ship. So buy locally, and drive over to the seller.

Shopping for your electronics though online is fine. I personally would stick with quality brands like Victron and Schneider that are European-based. For my own cabin, which powers lights, television, computers, and a refrigerator, I find myself consuming between 2.5 and 4.0 kWh of power per day. Not knowing your location, I'd guestimate you get between 2.5sunhours of power in winter and 5.0 sunhours of power in the summer. Plan on fully powering the cabin on the worst day of the year, not the best. So, to get 4000wh (4.0kWh) you might need 4000Wh/2.5sh = 1600W of solar panels.

That just so happens to be the maximal number of panels I could fit onto a single-pole double-row solar array I built. I always love to show off, so here is a pic of it. This can hold six 260W grid-tie panels, which might be perfect for you. BTW, here in California, I just bought six panels of this size about 3 months ago for 390$US, cash and carry. On a smaller scale, I first designed a single-row array frame I initially designed to hold three 300W panels. So, two of those instead of one double-row. Since they rotate, you can position them eastward in the morning, or westward in the afternoon to increase output. Or, you can do what I do and face one array SE, and another SW, and just forget about them.

One last item to focus some attention on is your batteries. I'll assume the batteries are rather old now, and showing their age. Maybe, or maybe not. You will at some point reach the point when it comes time to replace them. One thing to think about is what's called "days of autonomy", that is, how long will your batteries support your cabin with no solar. Imagine a winter storm blowing in, your panels are snow-covered, and solar input is zero. You want to scale the battery to how long is can support powering the cabin at your load rate, for the number of days you expect be be without sun. Lets's say you want 2.5kWh per day, for three days without sun, not dropping the battery charge level past 50%. The math works out to be (2500Wh X 3 days)/50% = 15,000Wh. That would be a 625Ah battery at 24V if you are chosing lead-acid, or perhaps a
(2500Wh X 3 days)/75% = 10,000Wh battery if selecting Lithium.
 

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triplem

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Joined
May 14, 2022
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Thanks a lot for the time you took for your answers :

It's true that I forgot to give you the target consumption. The powertools would be used rarely, only for wood work when necessary. So far the highest wattage is 1200 for a circular saw. We will start really simple for the moment and focusing on powertool (and avoid relying on our petrol generator). Then when we get a good grasp of our input and storage we will build upon the current system.

We won't touch the solar and wind controller for the moment then. We will probably improve the wind one first, but at a later date.

So for the powertool I noted a Pure Sine Wave inverter with low frequency.

@12VoltInstalls Yes, currently we have 24v.

I will get the power input of the panels and wind turbine as mentioned by @Rednecktek .
And thanks @Rednecktek I will dive into your todo list.

@MichaelK Thanks for sharing your setup. I will calculate for the worst day of the year scenario. We do have our french craiglist, I had a look this morning, there are some cheap panel out there, I'll probably get 1 or 2 more later, when my consumption will increase.

Once again thanks for your replies. I will probably pop with more questions regarding this system, later.

Have a good day :)
 

rin67630

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Joined
Apr 29, 2020
Messages
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While there is a bit of draw when it's idling, it's often not worth the hassle to fumble around turning the inverter on when you just want to watch TV. At best disconnect it when you leave and turn it back on when you arrive.
Absolutely disagreeing!
The OP probably has 2 x (200W to 250W) panels peak power, on cloudy days without wind, the day harvest is minimal, less then 10% for only a few hours in winter.
An idling inverter 24h/24 can jeopardize that scarce whole day's harvest just for peanuts.
 
Last edited:

rin67630

Solar Addict
Joined
Apr 29, 2020
Messages
919
Good afternoon,

We bought a small piece of land a few years back (in France). We'd like to improve the system, and we have some questions as we are new in this

Here is what we have so far

Input
- 1 wind turbine (no ref)
- 2 solar panels (no ref)
(Both are up a metal tower, we'll need to climb up there, but aren't equipped yet to do it safely, so we don't have any ref)

Storage
- We have 2 CPM12 solar charge controller (1 per panel)
- 1old controller for the wind turbine (no idea for the reference its a very old one in an old metal box)
- We have 4 batteries in series (each are 6v) so 24v out.

Output
We have:
- a small wood cabin 20 meter from the installation
- a small barn at 100 meter from the installation

But we only power 24v lightbulb that's it, we'd like to improve the system to plug more appliances.

Here are our thoughts for the system with our questions.

Input:
- We'd like to gather production data (how much our solar panel and wind turbine produce per day)
- Have a single charge controller (for both the solar panel and the wind turbine)

Is there a controller that can do this ?

Output:
- We'd like to plug some powertool in the barn for light wood's work. So we are looking for an inverter 24v -> 220v and around 1.5 kW - 2kW.
- The inverter would only be used while doing the work, then it will be removed and stored away.

Are there good reference for such inverter ? What should we avoid ?
Are there inverters that can be switched on forever ? or is it better to switch it on/off as necessary ?

Last question: is there a necessity to have a 24v system instead of a 12v ?



Thanks for your time and consideration.
You probably have 2 x 200W to 250W panels with 30V or 36V MPP.

The very best would be to replace your 2 PWM controllers by a single MPPT controller and wire your 2 panels in series (if you haven't shadows on them). You can later expand your panels ad libitum...

Then get test your batteries, if they are still in good shape.

If a were you, I would not invest a lot into an inverter for your tools, but get a petrol generator for that sporadic use.
You need the generator anyway to recharge the batteries and get you over a week of dull and cloudy weather.
A good 24V electronic charger is also an investemnt to consider, the DC outputs of generators are frequently sub.optimal.

You would also want to replace the 24V lightbulbs by LEDs.
You have also 24V/12V DC-DC converters to power the more common 12V appliances if you can't find 24V devices.

What are your electrical skills?
 
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12VoltInstalls

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@12VoltInstalls Yes, currently we have 24v
So basically already 24V lighting? Unless you have or plan to have a lot of DC accessories/lighting at 12V sticking with 24V makes sense. While on the other hand 12V will handle 2000W fine, your current wind is working at 24V so keeping that is a good idea. I’m not even certain upgrading the wind controller would be something I would do if it’s working.

would not invest a lot into an inverter for your tools, but get a petrol generator for that sporadic use.
plug some powertool in the barn for light wood's work. So we are looking for an inverter 24v -> 220v and around 1.5 kW - 2kW.
- The inverter would only be used while doing the work, then it will be removed and stored away
I don’t think they wanted to use a generator
 

triplem

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Joined
May 14, 2022
Messages
7
The very best would be to replace your 2 PWM controllers by a single MPPT controller and wire your 2 panels in series (if you haven't shadows on them). You can later expand your panels ad libitum...
I actually saw a video recommending MPPT controller, i'll dive into it.

Then get test your batteries, if they are still in good shape.
The batteries are quite new, we changed them maybe 2 years ago. Only issue it that there are always fully loaded since we don't use much energy from them (apart the lights that may be on for around 10hours per week during winter time)

If a were you, I would not invest a lot into an inverter for your tools, but get a petrol generator for that sporadic use.
You need the generator anyway to recharge the batteries and get you over a week of dull and cloudy weather.
A good 24V electronic charger is also an investemnt to consider, the DC outputs of generators are frequently sub.optimal.
We do have a petrol generator, but we kind of want to use the electricity generated by the system (instead of letting it go to waste). We probably won't invest much.

For the dull and cloudy weather, our region is quite windy. I don't have the data, but I believe our wind turbines generates more that our solar panels. This is why I'm looking for a way to get the data too ^^, to have better understanding of our input.

You would also want to replace the 24V lightbulbs by LEDs.
You have also 24V/12V DC-DC converters to power the more common 12V appliances if you can't find 24V devices.
Good point, I was thinking about this the other day. Just one thing, with my multimeter I got around 27v-28v. Do you thing this tension can be dangerous for lightbulb ? Or they can survive it ?

What are your electrical skills?
None (apart elementary lesson from school), but willing to learn.

And thank you for the link to PVGIS I'll look into it.
 

MichaelK

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An idling inverter 24h/24 can jeopardize that scarce whole day's harvest just for peanuts.
I've scaled my solar inputs to above maximum because solar is so very cheap now. Thank you Craigslist!!!

I'm exceeding even my own recommendations with the math I usually use here. With my sized battery, I should have installed (568Ah/8) X 50Vcharging X 1.175FF = 4170W. I installed 4500W.

What I'm finding now is that even on a rainy/cloudy day, I'm still making about 2.5-2.7kWh of power per day, amounting to ~0.5sh. So, the cabin can be unattended, and I still get more or less a full charge unless there is a snowfall.

So, I'm at the point now that I really need a good reason to shut off the inverter. It just isn't wortj my time to walk around to set the clocks back to the right time, or reboot the TV or router.
 

triplem

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So basically already 24V lighting? Unless you have or plan to have a lot of DC accessories/lighting at 12V sticking with 24V makes sense. While on the other hand 12V will handle 2000W fine, your current wind is working at 24V so keeping that is a good idea. I’m not even certain upgrading the wind controller would be something I would do if it’s working.
I will need to get the measure from the wind turbine, I believe this is why they kept the system to 24v. Else it means I need to reduce the tension between the turbine and the battery (if I setup everything to 12v) ?
 

MichaelK

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Good point, I was thinking about this the other day. Just one thing, with my multimeter I got around 27v-28v. Do you thing this tension can be dangerous for lightbulb ? Or they can survive it ?
No problem. It's common knowledge that batteries need to charge at voltages higher than the rating, so all the equipment is rated for that. Everything in your car is rated at least at 14.5V, not 12V.
 

MichaelK

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I will need to get the measure from the wind turbine, I believe this is why they kept the system to 24v. Else it means I need to reduce the tension between the turbine and the battery (if I setup everything to 12v) ?
Please stay at 24V. Please do NOT downgrade to 12V. I myself regretted that I designed my own first system around 12V, not knowing any better, and now I advice everyone here to bypass 12.

The best option you have here is to collect your own data in real-time as to what your turbine is putting out. For everyone operating a solar system, I recommend getting a clamp meter like this one. The clamp lets you measure the amp flow through a wire in real-time, without disconnecting the wire from what it is powered/powering.
This is the brand I am using right now on a daily basis. There are cheaper meters that read AC amps only, then AC and DC amps as a step up, and then inrush current, for which this meter reads all three. Every solar operator should get one.

Getting back to the idea of buying one or two more panels, no, buy 6-12 more panels. Most likely your turbine is outproducing your solar array right now simply because it is so small. I'll assume that you could easily increase your solar output by a factor of 10 without too much of a monetary input.
 

triplem

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May 14, 2022
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The best option you have here is to collect your own data in real-time as to what your turbine is putting out. For everyone operating a solar system, I recommend getting a clamp meter like this one. The clamp lets you measure the amp flow through a wire in real-time, without disconnecting the wire from what it is powered/powering.
This is the brand I am using right now on a daily basis. There are cheaper meters that read AC amps only, then AC and DC amps as a step up, and then inrush current, for which this meter reads all three. Every solar operator should get one.
I was wondering if I could plug something like a raspberry pi or else to aggregate data for a long period of time, and get the data back with a usb or with bluetooth. Or any other devices that does that.
 

rin67630

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I've scaled my solar inputs to above maximum because solar is so very cheap now. Thank you Craigslist!!!

I'm exceeding even my own recommendations with the math I usually use here. With my sized battery, I should have installed (568Ah/8) X 50Vcharging X 1.175FF = 4170W. I installed 4500W.

What I'm finding now is that even on a rainy/cloudy day, I'm still making about 2.5-2.7kWh of power per day, amounting to ~0.5sh. So, the cabin can be unattended, and I still get more or less a full charge unless there is a snowfall.

So, I'm at the point now that I really need a good reason to shut off the inverter. It just isn't wortj my time to walk around to set the clocks back to the right time, or reboot the TV or router.
Did you measure the no-load drain of your inverter ? Good ones low frequency type in the 3-4KW range easily need 10W to 20W just for idling, some a lot more. 10W idle means a full KWh wasted every 4 days. 20W, every two days.

By the way: the router runs perfectly on a DC/DC converter, no need for AC.
And also that one needs a KWh every 4 days.

Same for a fridge, a 24V DC compressor fridge is ways more efficient than one on AC + an inverter.
 

camelCase

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For the occasional power tool loads, you might consider a small generator. That way, you can keep your solar installation at a more modest size as well as have a redundant, backup power source. You will also save a lot of money by not buying copy a lot of copper wire to reach your barn.

I like the Honda eu2200i with a propane conversion kit. The propane stores indefinitely and you will have fewer issues with the engine with intermittent usage.
 

rin67630

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Messages
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I was wondering if I could plug something like a raspberry pi or else to aggregate data for a long period of time, and get the data back with a usb or with bluetooth. Or any other devices that does that.
I made a powerful monitoring system based on an ESP8266.
It runs todays on a small 33W panel with a PWM controller, but is scalable to nearly every other system.
The code ist on
Github.
I initially wanted to perform the MPPT controller function as well, but i gave up (too much blue smoke) and now it's a measurement only system.
You can see it in action here:
Dashboard
But you need a few soldering and programming skills.
On the other side it is extremely informative, much more than what you get commercially and the dashboard is available worldwide.
You can aggregate the data on excel and do much more...
In the next weeks I will publish some schematic diagrams for severla variants from very simple low power battery monitor to a full fledged 48V 5KW system.
 

12VoltInstalls

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will need to get the measure from the wind turbine, I believe this is why they kept the system to 24v. Else it means I need to reduce the tension between the turbine and the battery (if I setup everything to 12v)
What I answered earlier is that 12V would work because you asked. However is not a specific recommendation to do so in your situation.
As far as monitoring https://www.amazon.com/dp/B07T8GN61Z/ref=cm_sw_r_cp_api_i_F5K2XASHBBZV89YFCR4H?_encoding=UTF8&psc=1
 
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