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Beginners idea for going solar


francois

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Hi all,

I'm new here and don't really know that much about solar,but am planning to get my own solar system going and learn a lot from everyone here in the process.

I have a setup in mind and would like to hear your comments and advice please. 

With the budget being the biggest constraint,the aim is to start with a basic system (hybrid inverter and PV panels) to reduce consumption from the grid during the daytime and to then add some battery backup later for basic loads such as lights and a plug or two during loadshedding/grid maintenance, especially when it's dark.

I've seen some positive comments/feedback on the Renesola/Inifinisolar Plus 3kw hybdrid. What I like most about the unit is that it can supply the requested load from more than 1 source at the same time. 

My aim is for the PV panels to supply most of the load requirements during the day, while still relying on the grid at night time. 

If the Efergy meter is anything to go by, the load on the house is between 300w to 400w with things like the tv,fridge,freezer,router running, and from there it goes up to between 1 to 2kw, depending on what's on at that stage.  For instance, when the pool pump is on the load goes to 1kw and if the aircon (inverter type) turns on as well it can go to 1,5kw. Daily consumption ends  somewhere between 20 and 25 kwh. 

Considering that the Inifinisolar Plus 3kw can supply the load from more than 1 source, I'm assuming it would be best to divide the DB into 2 sections?

One for heave energy users like the geysers and stove that can be turned off/isolated from the inverter when the grid fails, and the other for essential lights and plugs which can stay connected to the inverter.

Any comments and advice is greatly appreciated.

Regards,

Francois

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3 minutes ago, francois said:

budget being the biggest constraint

Isn't it always? :-) The Renesola unit you mention is a rebranded Infinisolar. There are enough happy guys here with that inverter. Around 16k I believe (for the 3kva) and has a built-in MPPT.

4 minutes ago, francois said:

supply the requested load from more than 1 source at the same time

That's the definition of "hybrid" :-)

5 minutes ago, francois said:

Efergy meter is anything to go by, the load on the house is between 300w to 400w

For all our debates in the past about the inaccuracy of these meters, I find that when you measure the load of the whole house, it's within 10% of the actual value.

6 minutes ago, francois said:

One for heave energy users like the geysers and stove that can be turned off/isolated from the inverter when the grid fails, and the other for essential lights and plugs which can stay connected to the inverter.

I did it that way. Lights and essential services on output of the inverter. The rest on the grid side. My inverter uses an external grid-limiter implementation, so I can still allow my inverter to push back surplus power to appliances on the grid side, while the grid limiter balances my push-back to avoid pushing to the grid.

@JDP is the infini expert, he'll be able to tell you what is possible.

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Thank you very much @plonkster, much appreciated.

The external grid-limiter implementation sounds awesome. If I understand it correctly, with that setup you can still supply those heavy use appliances like the stove etc on the grid side with surplus solar? Wow :)

Hopefully this can be done with the Infini. 

Edited by francois
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35 minutes ago, francois said:

This shouldn't be an issue if I disable grid feedback on the inverter? 

Cannot say. It depends very much on the meter. Older meters didn't look at the direction of power flow and would simply bill you for anything you pushed back. Using a grid-limiter with these meters works fine: The short periods where you push back small amounts while the inverter pulls back isn't enough to break the bank. The newer meters however...

The newer meters check for backflow. I can't speak for all of them, but the popular Conlog BEC23 is said to trip if you push back more than 40W over a 15 second time window. @Wetkit had a problem with his infini on that meter. My Victron hub-4 setup works fine though, on a similar meter.

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The issue that I never see mentioned when grid tie installations are discussed is the policy of the particular municipality. In Swartland Municipality in the Western Cape where I live, feed in tariff this year is R0.685, same as last year. Consumption tariff is R1.2718 up from R1.18 last year. Also no credit balance or roll over to the next month is allowed. Subsequently one has to generate about 86% more than your consumption just to break even. For the life of me can I not fathom the logic, if any, behind installing grid tie solar under such circumstances. It will surely take a while before you are in the black on the investment. Just too much effort to try and calculate it with such glaring negative factors. Who knows what municipalities will do to you financially if you run a meter backwards. So perhaps the prudent approach is to first establish the ruling policy before making decisions.

 

 

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Okay thanks. 

I want to start with some PV panels only and then add batteries later.

From reading the manual I am hoping to use Off-Grid (I) mode with the following settings:

1. PV energy supply priority setting: 1st load, 2nd battery

PV power will provide power to the load first and then charge the battery. Feed-in to the grid is not allowed under this mode. That means the transfer time from inverter mode to battery mode will be less than 15ms. Besides, it will avoid overload fault because grid can supply load when connected load is over 3kw 

2. Battery charging souce: PV or Grid

3. Load supply source:

When PV is available

1st PV, 2nd Grid, 3rd Battery

When PV is not available

1st Grid, 2nd Battery

Except I won't have batteries. Is this possible?

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  • 2 weeks later...
2 hours ago, cvzyl said:

Hein

The Infini has a built in export limiting function. I understand from some people that it can also communicate with a smart meter rather than only looking at its own internal measurement.

C

 

I know about the built in grid limiting function but it still exports a tiny amount from time to time (like other users reported) and this can cause havoc with certain meters.

Are there any external modules that can communicate with the infini solar inveters?

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1 hour ago, HeinTheTerrible said:

still exports a tiny amount from time to time

Technically I don't see any way to avoid it. It takes time to make measurements, so the inverter is always playing catch-up. The prepaid meter has exactly the same problem though! Some meters even have a built-in limit, it allows those small amounts as long as it remains within a certain limit (Conlog BEC23 for example). So the trick is to be faster than the meter.

The only retrofit method I could think of -- which thankfully I didn't need because it turns out the Victron Hub-4 setup is fast enough -- is something @Jaco de Jongh suggested, a Rhomberg SP510 relay. These things detect reverse flow and activate a relay. My plan was to use this relay to turn on a load, something like a couple incandescent lamps, so that large reverse flows is effectively sunk into a load rather than into the grid.

In hindsight that idea seems a little hare-brained but might just work.

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26 minutes ago, plonkster said:

Technically I don't see any way to avoid it. It takes time to make measurements, so the inverter is always playing catch-up. The prepaid meter has exactly the same problem though! Some meters even have a built-in limit, it allows those small amounts as long as it remains within a certain limit (Conlog BEC23 for example). So the trick is to be faster than the meter.

The only retrofit method I could think of -- which thankfully I didn't need because it turns out the Victron Hub-4 setup is fast enough -- is something @Jaco de Jongh suggested, a Rhomberg SP510 relay. These things detect reverse flow and activate a relay. My plan was to use this relay to turn on a load, something like a couple incandescent lamps, so that large reverse flows is effectively sunk into a load rather than into the grid.

In hindsight that idea seems a little hare-brained but might just work.

 
 

Edit: Found this one. The only problem is cable length is limited to 1.2m.

http://www.solarelectricwise.co.za/infini-energy-meter/

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Hein

I think something like this is used by some guys to give feedback to the inverter. The inverter then does total feedback control. As far as I know it connects with a LAN cable.

https://www.aliexpress.com/item/SDM220-Modbus-Single-Phase-DIN-Rail-Kwh-Energy-meter-Pulse-Output-Energy-Meter-RS485-Modbus-Communication/32442937847.html?spm=2114.13010608.0.80.Uddg3a

C

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5 minutes ago, plonkster said:

Probably the usual Modbus setup. I believe you need a Modbus card in the inverter, though that might be standard. Don't know these inverters.

Yip, you get a modbus card for the infini inverters. The manual on the energy meter states that max cable length between the inverter and energy meter cannot exceed 1.2m. This is a massive issue because the inverter won't be installed anywhere near the main DB.

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