Going Solar - Adding a solar PV battery system to our house

[routercnc]

Well, the time has finally come for us to add a solar PV battery system to our house. We eventually decided on the specification, signed up, and are awaiting an installation date for all the bits.

While we wait for that, time for some custom parts . . .!


https://youtu.be/GUgtPUpgXPk

[Lee Roberts]

Nice! will follow along as usual :emmersed:

[routercnc]

Thanks Lee. Looking forward to seeing what it can do.

[A_Camera]

Had this since over 3 years.

31787

It's a Solaredge system, producing about 11 MWh each year which is about half of our need. We didn't invest in battery packs because it was not worth the price. Looked at battery packs again just two weeks ago and is still too expensive. We sell back what we don't use. One of the best investments we ever made, especially since we use electricity to heat our home and also charging our cars. One EV and one PHEV, both will be upgraded later on this year with two new EVs, which we ordered last year.

Good luck. You won't regret it.

[routercnc]

Had this since over 3 years.

31787

It's a Solaredge system, producing about 11 MWh each year which is about half of our need. We didn't invest in battery packs because it was not worth the price. Looked at battery packs again just two weeks ago and is still too expensive. We sell back what we don't use. One of the best investments we ever made, especially since we use electricity to heat our home and also charging our cars. One EV and one PHEV, both will be upgraded later on this year with two new EVs, which we ordered last year.

Good luck. You won't regret it.

Thanks I remember you talking about your system a while ago, very impressive. From my research it looks like everyone is different as their needs and use pattern is different so hopefully this will work for us. Selling back in the UK is not great and I think it is about 5p / kWh whereas they sell it for ~40p / kWh at the peak rate. So a battery pack was OK for us to charge in the day and use in the evening and overnight. We have gas central heating and electric storage heaters are very expensive so we will stay with that for now, so that lowers our requirement. We would also have to go up massively in spec to charge a car so we are going with overnight cheap rates on something like one of the Octopus tariffs. Let’s see how this goes.

[routercnc]

This time we upgrade the battery shelving to cope with the batteries . . . . getting closer to installation date!


https://youtu.be/4669HQRXyAE

[routercnc]

Episode 3. After all the planning and prep work this is finally starting! But as you might expect there were issues along the way . . .


https://youtu.be/h30qG6xMkmM

[routercnc]

OK, we finally finished! Now all we need is some sunshine . . .


https://youtu.be/DEvQjGllLSI

[routercnc]

Apologies that this video series might not mean much to people without solar, or with AC coupled systems, but for hybrid inverters it not possible to see the DC readings for the battery or panels on a third party app. Well, when I say not possible, it can be read through the RS485 onto something like a raspberry Pi running home assistant software, but I wanted it on the Myenergi app as for me that was much more convenient.
So I decided to do something about it - here is the start of the journey!

https://youtu.be/SPCqaTQxiN8

[routercnc]

For those following along here is episode 2 . . .

https://youtu.be/4arVX3kK0gA

[routercnc]

I've finally got it working to a reasonable level . . plus there is some actual machining in this one!


https://youtu.be/e2-jCLWncrA

[routercnc]

Making some improvements - open loop to self-calibrating closed loop!


https://youtu.be/JT4Evjn5NK4

[Space_ranger]

Great set of videos! I’ve got a similar problem and wanted to ask about how to build the AC side of the circuit. I have the power data scraped from the inverters modbus port so just need to simulate the signal for the harvi.

I’ve found some ac 240v to 5v transformers so was planning to put that into a small box with an esp32. Then use the esp to generate the signals to control the simulated ct clamp.

I just can’t work out what components you’ve used or how the ac part functions. How does it deal with the ac? A lot of the components I’ve found for variable resistance only allow dc

[routercnc]

That’s why it took several months to solve the problem. The Harvi needs a varying AC current to determine the current in the cable (using a CT clamp). Getting a simulation of this signal took some working out.
My solution uses an AC transformer (AC to AC) and an LED/LDR combination to control the AC current. I couldn’t find another way to do it. The LED is pulsed by the microcontroller and this varies the LDR resistance in the AC side. That is the principle but it also took several hundred lines of code.

What system have you got in terms of panels, batteries, and inverter?

[Space_ranger]

I’ve got a solis hybrid inverter with 48v dc coupled batteries. I had botched some code to read the inverter registers but then someone else wrote a really good integration for home assistant. It can read out all the power info from the inverter and can even can control some inverter settings.

Unfortunately the myenergi api doesn’t allow for sending data otherwise it consuls all be done in software.

Your solution is a great workaround to send info to the system. I have a lot of work on currently but am going to look into the variable ac signal control some more. Im hopeing someone makes an ic designed for the task. I found a digital potentiometer on RS that can deal with AC up to 12.5V (MCP 4551)

The only issue is the current limit is really low, 2.5mA so out of range from what you found for the ct clamps.

[routercnc]

Ok my batteries are 160V so probably helps with a detectable level of current for my CTs. What sort of DC current flows there in your system? Would a CT detect it? You can wind the cable around them multiple times to upscale it, assuming the cable will bend enough!
After that you are into intrusive options like shunt resistors and current sensor boards but you will have to decide how safe those are, insurance risk etc.

Software interfacing would be a great option as it is so customisable compared to hardware solutions. These always have a valid range of operation which means many options are not suitable.

The other thing I looked at was the main chip inside the Harvi can read all sorts of protocols including i2c which is what the Arduino can output! But it would require significant changes to the Harvi and probably more knowledge than I have. But it would cut out all the AC current creation and just tell the Harvi the current level directly, but still would need the CT clamp to detect it.

Also try posting on the myenergi forum and I think there was a Home Assistant forum too?