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Youda's off-grid LAB


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Hi guys,

let me share my current solar LAB setup with you:

PV modules

The only installation option was the roof,  which unfortunatelly has a bad orientation: one side of the roof is facing East while the other is to the West. So I decided to install panels on the both sides of the roof. Luckilly, the panels are not so expensive and are going to last for decades, especially when compared to price and endurance of batteries. It's 36x 275Wp facing West and 36x 280Wp facing East. All together it's almost 20kWp of solar modules, but because of the orientation, the maximum possible power is quite a bit less than that. Panels are wired in four high-voltage string,  each having 18 panels connected in a series. The actual voltage of each string is 600V. Inverters, that I use, have a maximum allowed DC voltage of 900V, so there is a plenty of room for voltage increase that is going to happen during cold winters that we're experiencing here. For the DC cabling, I used 6mm2 solar cable.







Photo from mounting the modules:




All the high-voltage strings are connected directly to a pair of InfiniSolar Plus 5K inverters, that are paralleled together. So, there's no combiner box under the roof. Of course, there are fuses placed in each string, one fuse for positive and one for negative. Every string has a surge protection too (Citel). The inverters are set in OffGrid III mode, so they use ESKOM just for syncing their frequency with the grid, but the grid itself is disconnected (there's a grid disconnect relay in each InfiniSolar). Therefore no energy is supplied back to the grid, nor can it be physically supplied. When a power spike on the AC output of the inverter occurs, the inverter sends the excessive energy to the battery. Such a spikes occurs whenever a strong appliance is turned off, for example geyser or kettle. If the battery is completely discharged, the inverters can automatically switch to the bypass from the mains. In such a case, solar energy is used only to charge the battery until the battery voltage reaches an acceptable level again. So far, it has not happened, but since winter is comming, I'm awaiting this to happen soon. If the grid fails, nothing happens, the inverters do not need the grid to run. Synchronization of both Infinis with the grid is drawing 4 Watts total. Well, I'm looking forward to see the invoice from the ESKOM :) The combined power of the inverters is 10KVA, so it can run ANY appliance that I need, even some combinations are not a problem. So I'm running a washing machine, geyser, fridge with ice maker, tumble dryer, induction cooktop, etc. Not counting numerous computers, laptops and TV's.

InfiniSolar Parallel:




Just to be safe, the LAB is backed by 3kVA UPS and the 8kVA genset with electric start. So I left the UPS to supply the light circuits, internet routers, firewall, DVRs, surveilance cams and other crap. The genset is wired in a way that it can supply the AC to the InfiniSolars in order to power the LAB and/or charge the batteries in a case of a real emergency. To be honest, I'm running a genset just once per month to do a regular "fire-drill", since it's cheap and loud as hell.

Battery bank

The battery bank is a 48V 200Ah LFP box that I've purchased as a product built to order. There's 16x100Ah Winston cell. So far, it works great, but my LAB has a night consumption of about 6kWh, so the battery is small in the long run. There's 16x 1A balancer, coordinated by a central BMS. The BMS has a small OLED display, so you can check the SoC, AmpHours, charging current etc. directly by looking on the box.



BMS cyclically send all it's status and all the values to the UART interface. So I hooked UART with Z-Uno and pass the values through Z-Wave wirelles network to the home automation (Fibaro). The Fibaro is already monitoring all electricity meters that I set up on AC in/out. It's also monitoring and controlling a number of electrical appliances I have. And sice I wanted to have everything in the one place, I'm monitoring the RS232 interfaces of both InfiniSolars. Thanks to this, with just a cellphone I can see how the laboratory works while I'm on the other side of the world. For example, I can turn any appliance off/on or change the temperature of the heating in each room separately. Well, I hope that this supercomplicated system won't kill me in somewhere in the future. BTW, the geyser is operated in the same way - Fibaro turns it on when the batteries are full and there's a lot of sunlight. Values from Fibaro can be easily transferred to EmonCMS, so I do in order to keep a history charts. In each InfiniSolar, I have an SNMP Web Pro Card installed, so I do not need the SolarPower and SolarPower Pro software at all. Built-in webserver on SNMP cards is quite usable, and in fact you can also set up parallel mode with it's help. The downside is that after a few weeks the SNMP card got stuck - obviously the watchdog circuit is missing. At first I thought that one of the cards was faulty, but after the second card experienced the same issue, I realized that it is "a feature".

36x PV module delivered:




Edited by Youda
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7 minutes ago, Jaco de Jongh said:

I am with you on that one. I am busy installing 28 panels on my roof , alone, installing the rails, pulling up the panels, align and fasten them . :(

I found the rails being the real pain in the ass. So the rails was the only part where I hired a contractor.

First 18 panels I installed with a help from my friend, but he was badly sunburnt on that day, so it looks like our friendship is not as good as before :)

Therefore I have to pull and mount rest to 72 by myself... 

Edited by Youda
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18 minutes ago, Youda said:

I found the rails being the real pain in the ass. So the rails was the only part where I hired a contractor.

First 18 panels I installed with a help from my friend, but he was badly sunburnt on that day, so it looks like our friendship is not as good as before :)

Therefore I have to pull and mount rest to 72 by myself... 

Also the angle of your roof must have made working on it rather risky?

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Couple of days ago, I was asked about the max power that my system is able to provide to the AC loads. So I did a quick test and it looks like supplying 10.000 watts is not a problem:


For this test, I turned on all the electric appliances around the house, even the floor heating. By that time, the electric meter that I've installed on AC-out reported 46.5 Amps at 230V. To be honest, I was not a brave enough, so after a four minutes I've turned all the loads off.

Well, it's good to know that I can turn on a tumble dryer and dishwasher at the same time, while still having more than 50% headroom. Is such a system having a good ROI? The answer is NO. But it's a very similar feeling like to drive a decent car - usually, you're not running 160mph all the time, but it's good to know that you can, if there's a good reason to do it ;)


BTW, normally I'm having just 3 to 4kW peaks during the day:


Edited by Youda
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Well, I travel a lot to see my customers and attend some corporate meetings from time to time. But let's say, that at least 4 days in a week I spent working remotely from my LAB. You know - preparing offers, creating designs and trying to sharpen my weapons in order to fight the ruthless competition.

When I'm traveling, I try at least to turn-on dishwasher and washing machine in the morning  or via a timer. Since the washmachine has a small heat-pump integrated, it works like a tumble dryer too, which I found as a great feature.

But Chris, what do you think about winter time? I'm a bit affraid that on winter dawns, the sun will not be appearing on the East, but will start to shine too late to hit my East panels and will fade too early to spend enough time shining on the West PV array too.

So, I'm looking forward to winter, in order to check whether I will be able to survive or will have to switch back to the local "ESKOM".

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While reading my first post, I found an error in the battery specs, as I wrongly stated that there's 16 x cell. The correct specs are:

There's 32 x 100Ah Winston LFP cell and 16 x balancer. Each two cells are connected in parallel and equiped with a balancer module. For battery-to-inverter connection, I've used 50mm2 cable and tried to keep it as short as possible, in order to minimize voltage drop under a high loads.

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  • 3 months later...

Hi Gnome,

I'm using the home automation system called "Fibaro". So, I have a power measurement and remote control for every important wall socket, and for some lights, etc, too.

For most of the loads that fall under 2500W, like dishwasher, fridge, PC's, I'm using just the wirelless plug.
Some other devices are powered via smart-relays and modules and the devices with a huge amps draw  have a separate DIN-rail wirelless smart-meters installed.
As for the floor-heating, I'm using termostats that directly measure the consumption of every room.

Does it make economical sense? No.
Is it fun? Yes :)







smart module.JPG


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  • 2 months later...

Hi guys a short update...

A couple of weeks ago, I've added a second LiFePo4 battery pack to my Solar LAB. So, it's 20kWh of lithium now.





Also, I was not really satisfied with the reliability of my wireless monitoring. Originally, I used Z-Uno boards to read-out the RS-232 serial data from the inverters and send them over the wireless Z-Wave protocol. It worked, but sometimes half of the monitored values got stuck, while the other half was okay, etc. Therefore, this time I went for a small DIN-rail mounted PLC (Tecomat Foxtrot). Did a bit of coding and now I'm transferring the data over the ethernet, with the help of RestAPI and JSON. It's much faster and rock-solid :)

Since this PLC has a built-in display with UP/DOWN buttons underneath it, I used it for debuging and for displaying the operational state of both InfiniSolars too.

Current layout of the distribution board:



Detail of the PLC display, Screen 1 of 6:



Since I had to code anyway, I did a small improvement in my home-automation logic and now I'm able to switch ON/OFF each inverter directly from the phone.

Detail of the first inverter in the mobile app, note the ON/OFF buttons that I've added:

Screenshot_20190303-121506.png.3c0b102d57a4fb2a772de7032074c05b.png    Screenshot_20190224-144305.png.3054c101e5bc8519af4fc96dc7093f59.png


Now, I'm thinking of adding some more logic, that will enable me to automatically cascade both inverters:
- For the AC loads under 3kW, only one 5kW inverter will be active, while the other will be in the low-consumption charger-mode.
- Once the AC loads will go above 3kW, the logic will turn-on the second inverter too.
- Once the load will drop under 2kW for ten minutes, the second inverter will be switched back to the charger-mode

Shame is, that I'm feeling toooo lazyyyy now.....

Edited by Youda
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Another update on my LAB...

Couple of days ago, I did a small improvement on my 160L geyser. This project had two parts:
1) Clean the geyser
2) Use the solar energy to heat the water while keeping the grid as automatic backup

The unit is 7 years old and since the purchase, I performed zero maintenance on it. So I drained the tank, opened the flange and took a peek on the guts.

This is flange cover, with the casing for heating element and termostat probes. It's fully covered by the "limestone" sediments and the magnesium sacrifice rod is totally dissolved:



Inside the tank, there was a full bucket of lime sediments:



Luckilly, after a quick cleaning I realized that there was virtually no corrosion inside:



I've put old flange cover in the garbage, since I already had a new one, with the casing suitable for the larger heating element. Also ordered a new sacrifice rod and a ceramic element in a standard 3-phase configuration (star):

L1=1333 W
L2=1333 W
L2=1333 W

I rewired the element and split it into two parts. One will be fed by solar, the other will be connected to a grid and will switch-on only if there will be bad weather for a number of days.

L Solar = 2666 W
L Grid = 1333 W

Ceramic heater rewired:



The original panel had just one thermostat (plus one safety thermostat). So, I've added a second thermostat, some wires and LED's in a way that allows me to control each half of the heating element independently:



The actual wiring of the panel:


Upper part will be fed from Inverter. Bottom part will be fed from the grid and it's thermostat will be set to a minimum temperature suitable for taking a shower or bath :) Drawing on the side represents the location of the probes for each thermostat. Since hot water tends to collect in upper levels, grid thermostat has it's probe located the most high. Therefore, it will turn-on heating only if the water in the tank will be really cold. Contrary, the thermostat associated with the Inverter is located at the bottom, so whenever the water at the bottom will be even slighly cold, it will turn the heating on.


Edited by Youda
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