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Micro Inverters


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What do you guys think of these little inverters: http://www.i-energyinc.com/en/products/i-micro-inverter.html


For small systems, this seems perfect?


Getting a MPPT controller and inverter, then connect it to your DB board following all the T&C's are expensive.

Versus adding panel for panel with inverter, reducing your power consumption.


Just need to sort out the anti-islanding in case Eskom is off.

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I've investigated it a few years ago; for some people it might work, but I think the idea behind them is more to supply power and feed back into the grid during daytime when the sun shines. It is not really a solution if you require power at night or during load-shedding. I still prefer my all-in-one hybrid.

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ExSolar evaluated the iEnergy inverters at one point, 3 years ago or so. I spoke to Gerard at the time (he is no longer with them) who explained to me that the inverter is perfect in every sense except one: Price. At the time it was just too expensive. I don't know to what extent that has changed.


My main issue with these grid-tied jobbies is still that they provide no means of adjustment for us folks with prepaid meters that can't push back into the grid. I heard that some of these units support GFPR (Renesola?), but that means you have to throw in a Victron or a Sunnyboy as well... which kills the price advantage.

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So far all sounds encouraging.


Yes there are, as with all solar solutions, pro's and con's and then the cost factor.


I am going to see what the guys say, as I gather I can grid tie my 3 x 310w panels, using the 2 x 200w on a Victron MPPT controller to keep the Trojans charged, and power only my computer with spare power.


Quick Google search leads me to believe / hope I may be wanting to pay +-R1800 per inverter per panel. Do one, then the next one and so forth.


250w peak power per panel will go a long way to cut daily consumption, but, always the but ... the costs of getting grid approved as well as what it will cost me to buy back, may be a deal breaker.

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The one necessary evil in my home, the tumble dryer, is a prime target for micro-inverter-offsetage :-) This item alone will cut my consumption another 10%-20%. Only problem is, at peak power it uses 2.3kw, but when it is not in use, the rest of the house (not on the Mutiplus) uses 80 watts. So I literally need a way to turn the juice on and off when needed, preferably automatically. It can be done, I know it is within the realm of possibilities because the larger GTIs do it... Fronius for example... Microcare with their grid limiter, etc

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I have bloody +-300w of power used every hour that is not on solar, to costly extending to the flat.


If I can eliminate that every hour and then as in your case there is a additional load of say 2kw added, the remaining power can offset that a bit from spare being generated ... 


And then the old tipe aircons can work cheaper per hour ... and no inverter to up-size to handle all on sunny hot days. :-)


Just add more micro inverter connected panels if you want.  :D

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One thing I don't understand... So sometimes you need the power for the tumble dryer or aircon, but what are you going to do with the available power if the tumble dryer and aircon is not in use?  Are you going to export or just not make use of the surplus power? Is it worth it financially - buying panels and micro inverters etc. etc.? 

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Good question superdiy.


Listen, I am against grid tie all the way due to costs from municipalities, and if I can run with no surplus, just reducing the usage more efficiently at a lower cost than inverter up-sizing, more batts and panels ... 


Over years I have added more and more devices to powered my inverter. It is now increasing again, but I am stuck.


So, issue one is to save as much using solar as one can - grid tied is perfect for this, that is until issue two comes around and you need backup for Eskom grid failures. Now grid tied becomes seriously expensive.


So, thinking left around the problem ... 

Have backup if Eskom dies. My current setup.

Have 300w used every hour of the day that cannot go onto the inverter.


So, keeping the current system in place, adding more panels, one by one with Micro inverters, wisely to cover the +-300w per hour used every day.

And if I want to power aircons in summer, add a few more micro inverter panels so that in winter, when the EV tubes are also producing less, I can use the spare to offset the additional power required to heat the geyser?


Of am I missing the plot?


NOTE!!! It all depends on what the Municipality wants ito grid tied fees, for I do not plan to send surplus back.

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Would have been perfect if I could have connected the micro inverters to the inverters output, but as always, it never is that simple. Cannot work as they need utilities ... for now. :-) 


So, with the micro inverters, I would start with 1 panel, monitor the nett result. Then add another one and so on to ensure I never have a 'credit' with municipality.


Assuming it is that simple off course, no funny charges and all that.


Not sure if I can get past not feeding back ... will find that out once the guys come and see me.

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You ask good questions Super :-)


Money is a funny thing, evan a relative thing. Especially when you're self-employed and its up and down from month to month (I'm salaried again since December, had my first proper holiday in 5 years... didn't know what the heck to do with myself. Anyway....) So in a good month you might have some extra dosh that you want to blow on something that saves you money in the long run. Now this is where things get relative: R5000 might not be a lot of money if you have it, but on the flip side, R50 might be a LOT if you DON'T have it. So in this line of thinking, I am often prepared to blow money (in a good month) on something that makes my life easier, even if I never get the money back. That is to say, insert here the mindset of your average BMW driver. If he truly cared about value for money, he'd be driving something Japanese :-)


In addition, I like playing with this stuff, so there's reward in that already, something that's hard to put a price on.


So with that out of the way, if I did put up some grid-tied microinverters that are suitably restricted so they don't even feed back, then yes... there will be lots of times that they just sit there mostly idle, not paying back their money. That is okay. Over time I will find ways of using that power, maybe heating more water with it, running the dish washer during the day rather than at midnight, and so on and so forth. In the mean time however, there is this technical challenge of combining the neat features of the micro-inverter (which is that it allows a modular approach for under 10k a piece) with the reality of a stupid prepaid meter that can't handle back-flow.


In essence, do the same with micro-inverters as the existing solutions from ExSolar (for the Fronius) and SolarEdge. This is the challenge :-)


Now to get to something you already touched on, adding them to the current setup. So if you already have a Multiplus (don't know about the Phoenix), you tie them to the output of the inverter. Then you program the inverter to disconnect from the grid if the power draw is too low. You also load the GTI assistant. This adjusts the "grid frequency" according to the power requirements. As long as your GTIs support GFPR (I'm told that the Renesola units do), they scale back their production based on the shifting frequency and the inverter controls them.


So this is how you'd add them to an existing solution, but this requires what is in Victron lingo called a hub-2 setup. I don't want to do that. My inverter is too small to even dare using a tumble dryer or a dishwasher, or an AC on it. So what I want is what is called in Victron-lingo a hub-3 system. I can't use GFPR with this. I need something like the protocols used by the Fronius or the SolarEdge inverters. And so far I don't know of a micro-inverter that can do that.


So that's where my thinking is right now.

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The guys came to see me. We think the same re; costs of being grid connected. But, seems to me, City of Cape Town is friendly-ish ...


Apparently if you are in credit they could offset your rates and taxes or such on your bill, but no monetary refund if you feed a lot back.

City of Cape Town is buying at +-R95c ex vat per kw.

You can buy back at night at +-R1.35 ex vat per kw.


Cost to change the meter: R3000 once off

Cost to get the certificate: R4000 once off

About: R450 pm grid connection fee.


Waiting on the quote for the smallest initial setup with installation and based on that experience, see where to go from there, because when I pay the above costs, I am going to see if I can grow to the point where the credit can offset the rates and taxes on the property. All is currently in a flux as CoCT and Eskom are getting their systems in place for they do get it that solar panels are coming to a roof near you.

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