DIY Grid Tied Inverter, PV System Update 3.0

About: I am an apprentice electrician, DIY'er and renewable energy hobbyist

Here is the update we have been all waiting for!

So, since the first two Instructables on this topic I've learnt from my mistakes and improved, chopped and changed the system quite considerably, especially since I've moved into the workshop we have been building since the beginning of the year, giving me loads more space to work on this project.

Unfortunately, it’s been taking me a while to get this Instructable done because bee doing little bits here and there since I’ve been inundated with work lately! but we've got there in the end!!

The History of this system:

Part 1

Part 2

The Original Concept:

Many people want to have solar panels to reduce their impact on the environment or reduce the cost of their electricity and there two ways about doing this, going fully off grid that requires a large bank off batteries and a decent inverter or subsidising your electricity with both grid and renewable energy using grid tied inverters that feed your power back into the grid. The problem is that going off grid is not always possible, designing a system that would power everything you want without issue would be very difficult and unreliable. and with grid tied inverters you would need a qualified electrician to install the inverter so it conforms to regulations when feeding back into the grid which is not very cost effective for everyone or ideal for your application. so, my solution is a small-scale solar system with a "grid tied non feedback inverter" using basic components that are easily available. this allows you to produce and use your own electricity without feeding into the grid but still able to use the grid power when you run out.

The New Concept:

· Up-scaling, to be as energy efficient as possible

· UPS functionality to Protect the server

· Better monitoring of the system

· Better Control of the system

· Easy expandability

· Reliability and quality

· Fail safes

Step 1: What’s Changed (Back to the Drawing Board)

Well, in the grand scheme of things the principal is still

the same I still need a battery bank an inverter and solar panels.

In the new design I’ve done away with the small solar array since its output no longer meets my demand and the shed those panels where on has now been removed. The automatic transfer switch (ATS) has also been removed since it’s no longer required along with the battery protect and the 300w pure sinewave inverter.

So, you may be asking yourself…. but you’ve removed everything that made up your grid tied inverter and you would be correct since I moved into a new workspace I saw this as an opportunity to strip my old system and rebuild, it had been modified so many times that there was a lot of redundant cabling that wasn’t required so I had a good sort out and tidy up.

Step 2: What’s New (keeping It Simple)

I’ve always said from the beginning that I want my system to

be easy to install, and for parts to be easily accessible to anyone looking to build their own version of this system.

So to cater to my needs and keep it simple for everyone, I opted to use Victron energy devices primarily a 24v 1200W Multiplus compact, I did a lot of research before coming to this option, I was looking at larger inverters and using multiple automatic transfer switches to switch loads from ac to the inverter, but I couldn’t guarantee the systems redundancy and reliability.

Every time I came up with an idea I always ran into some problem that a Victron product would solve and as a result I ended up with their inverter, I already knew that they provide really good tech support and have lots of forums to help people with their product and going by their charge controller the quality of the products is very high.

Step 3: Parts :

  • Victron energy solar charge controller 30/100
  • Victron energy solar charge controller 50/100
  • Sun tech PV panels 275W (Damaged)
  • 8.33 Solar 300W Monocrystalline Solar Panel (Brand New)
  • 100AH 12V Powerline leisure batteries
  • PLC Controller
  • Rcd, Main switch, MCB’s and RCBO’s, Contactors
  • Multiplus Compact 24/1200
  • Victron’s Venus GX
  • Victron’s BMV 700

Quick Description:

· Victron energy solar charge controller 30/100 And Victron energy solar charge controller 50/100

controls the charging of the batteries from the 275w pv array it turns the 30v output down to 13v to charge up the batteries and stops charging them when there full.

·Sun tech PV panels 275W (Damaged)

They convert sunlight into 30v dc which then goes to a charge controller to charge batteries, I Brought damaged ones cheap then repaired them with a clear resin.

** I have since recoated them, the resin began to peel and turn yellow so I removed the resin and recoated them in a solar panel encapsulant, it is more like silicon so expands with the panels.

· 8.33 Solar 300W Monocrystalline Solar Panel (Brand New)

They convert sunlight into 30v dc which then goes to a charge controller to charge batteries and Can be brought for a great price if you look although delivery was a bit difficult, ill just leave it at “ I got them from wholesale and they came on an very big lorry down a very narrow road”.

· 100AH 12V Powerline Leisure battery

This is where all the electricity produced is stored

· Multiplus Compact 24/1200

An 24v inverter that converts dc power from the solar panels and the battery bank into ac electricity the same frequency as the grid

· Venus Gx

The Venus GX is the communication-centre of the installation. Venus gx allows you to talk to all components in your system and gives you an online portal to control your system.

· Victron’s BMV

Is a battery monitor that counts the amp hours charged into your battery bank and the current withdraw along with voltage to give you an in-depth knowledge of what your battery bank is doing.

· PLC controller

Not necessary but I have used this so that I can program some additional features into my system, such as load shedding and inverter bypass and shut down, its basically a controller that has inputs and outputs that can be programmed to turn on and off in certain circumstances.

Step 4: Re-coating Solar Panels

So before i got onto install the new inverter and making the changes, I made the most out of the time i had whilst the system was offline an decommissioned, it was the perfect opportunity to remove my old solar panels and remove the resin that I had put on previously, i found that a mixture of scraping and a wire brush on my angle grinder worked best for this, although if you have any better solutions for stripping resin off panels let me know in the comments because it was no small task!

once all the resin was removed the panels were vacuumed and washed clean, then i gave them a quick wipe with alcohol to remove any residual dirt or grease.

I lay the panels down on a flat surface then measured out my two part solar panel encapsulant, it works out 1:1 ratio of part a to part b and its sets to a clear silicon material that feels quite strong and durable.

Link To the product i used

I ended up using 1Kg (500g part A & 500g Part B) to coat one panel, this gave me a heavy but durable coat that has adhered really well to the panel., i used a squeegeeto spread it about And i found it had cured by the time i got up the next day (probably 12 hours or so) ive always found its best to just leave these things to cure in their own time if its not done just come back to it, no need to change the temperature.

I then remounted all my panels, gave the wooden frame a quick paint and connected them back into there isolator.

I also recommend this tool for removing the solar panel plugs MC4 Spanner

Step 5: Multi Plus Inverter & Victron Support

The inverter I choose for this installation was the multiplus compact 24v 1200W, becuase my last system was 12v I did have to re-arrange my batteries to give me the desired voltage. This inverter has some key points that make it very desirable:

  • It has a grid feed
  • it will act as a "ups" in the event of grid failure
  • Because of the grid feed the inverter matches the frequency of the grid
  • its easily programmable to not feed into the grid but to use grid power through "ess"
  • can be configured for self consumption
  • It also Monitors the battery bank
  • Along with data logging and the ability to expand and connect to other victron devices

I have configured my inverter to use ess, this is an assistant on the multiplus that allows you to use your system in a self consumption, the software is really straight forward to use and configure and there is alot of support for the community, when i was having issues and had questions everyone was more than happy to help on there forums and alot of the certified victron dealers also will give you alot of support.

If you do have any issues or questions:

https://www.victronenergy.com/support

https://www.victronenergy.com/live/start

And a shout out to these two companies that provided me troubleshooting advice:

http://www.projectoffgrid.com/

and this company provides service and repair for victron products, they were also very helpful!

https://www.energy-solutions.co.uk/

(i'm not being paid by these companies they just offer very good customer service)

Step 6: Configuration Venus GX & Multiplus (VE. Bus) All the Gear But I've Got No Idea!

Just learning as we go! .......

Ill keep it short since there is so much information out there already.

Useful links:

Victron ve configure

Venus Gx setup manual

Programming Inverter

Basically the ve configuration tools allow you to program your inverters parameters, giving it important information like where you are in the world, what grid connection you have, details about your battery bank, amount of amp hours, it also allows you to select what charging voltages you want to use.

It also allows you to install assistants like ESS. Assistants are a series of "Apps" that you can use to control additional functions. The Virtual Switch is another version of the same thing with less options. You cant mix and match, if you are going to use these its one other other.

As stated in the programming inverter link you dont need to adjust every setting but do have a look at theese ones.

  • Set the AC current limit to match the shore power service you have
  • Set the inverter low voltage shut down to a level that protects your batteries from over discharge, that means you also have to reset the start up voltage and the pre-alarm voltageSet the battery type or adjust the charge voltages to suit your batterySet
  • the AES search mode to save power when no load is connectedIf you have a small generator take a look at the UPS function,
  • the Power Assist function and
  • the Dynamic Current Limiter

Venus Gx

The Venus GX is the communication-centre of your installation. Venus allows you to talk to all components in your system and ensure they are working in harmony. Monitoring of live data, and changing settings is performed by using your smartphone (or other device) via our free-to-use Victron Remote Management Portal (VRM).

the venus gx provides an instant overview of your system: Battery state of charge; present power consumption; power harvest from PV; power provision from mains/generator.

ESS: Energy Storage Systems - 24 hour Monitoring
The Venus GX manages Energy Storage Systems. It keeps back-up batteries at 100% ; kicks-in during power-cuts; and diverts excess (solar) power to self-consumption - saving you money. For examples and more detailed information see the ESS (Energy Storage System) manual.

Step 7: Programming PLC Controller

I wont go into depth on this, and ill keep it simple...

Basically ive set up the out puts of the plc controller to reduce the load in the event of grid failure (basically load shedding) this is done by having the grid feed a NC contractor, when the grid fail this closes the contacts and tells the status input on the controller the grid has failed, as a result it will cut off all unessential loads via contractors keeping our home server and network on! ive also configured the other out put to control the heating within the shed this gives us an occupied setting and frost protection in the shed.

I will upload a video of me programming the controller soon along with some more detailed wiring diagrams!

Step 8: Victrons Online Portal VRM

Usefull Link:

VRM setup

The online portal is a useful monitoring tool that shows you exactly whats connected to your system, what and where power is going and also allows you to configure system settings remotely and update firmware.

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    2 Discussions

    0
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    tytower

    17 days ago

    So what is achived by keeping the battery at 100% all the time ?
    If you are using lead acid then surely you could increase your load to use more.
    If you are smart enough to use LFP , LiFePo4, then you could run much more again .
    I understand you are just putting together a viable system but if you are not using the batteries then you are not testing it fully either.

    BTW I like your work on this and have put in a vote for you in the contest.
    I run a 50AH 24V LFP setup running my TV , Computers and security night lighting from a 1000W inverster but would like to get something going along these lines as I have 22 new solar panels sitting unused in my yard .

    Would it not make sense to dump the 12V controllers for a 24 Volt one and series up your panels? I am moving to 48 Volts system now as this reduces the high currents of 12 Volt and improves efficiency overall .
    For LFP join this group.
    https://www.facebook.com/groups/271980786862023/?r...

    For a LFP 24V setup see here https://www.instructables.com/id/Working-System-LiFePo4-Battery-and-Spotlights-With/

    1 reply
    0
    None
    Kieren-Jtytower

    Reply 15 days ago

    Hi, thanks for commenting!

    the batteries don't stay constantly charged at 100% all the time, the inverter using them as buffer for when it needs large currents quickly, or when the solar drops of in the evening so I can still use solar stored energy at night , during the day it does charge the batteries but the solar also provides enough current that it can power the inverter and charge my battery bank. There is some tweaking to do with battery voltages since the battery doesn't discharge as much as I would like it too, but other than that works well!

    and the 12v controller is a typo. they are actually 12v and 24v and self adjust depending on the battery connected, so currently it is running 24v system although again like you stated I'd probably be better off looking at a 48v system to reduce overall currents in my installation
    Thanks for the vote,
    Regards,
    Kieren