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1KW + Grid Tie inverter with 80VDC+ input


Travis

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Good evening,

I am hoping someone can point me in the right direction.

I have 6x170W 82V-112V Solar Frontier panels that I am running into my DC Geyser through a Microcare MPPT.

By 11-12o'Clock, the geyser is up to temp (65-75c). I want to have the panels drive a grid tie inverter for the rest of the day. I have the DC SSR's and Temp Relay sorted. Now I just need an inverter to match.

I am battling to find one around 1-2KW, with grid tie that has a solar input range of

 

The Sunplug ECO 1.2 would be perfect, but I cannot find a price

http://www.currentautomation.co.za/files/sol/1445594717_SUNPLUG ECO 2.0 TL1ix.pdf?cache=5468

Are the Axpert's grid tie?

http://www.bonanzatech.co.za/index.php?id_product=7928&controller=product

 

This would also work and is cheap but I cannot find one with shipping to SA

http://www.ebay.com/itm/IP65-1200W-Solar-grid-tie-inverter-isolating-transform-DC56-220v-AC110V-LCD-play-/142114884484?var=&hash=item2116b50b84:m:mbm41MFvy1ZvuLGcMOQZedw

 

Has anyone got any ideas? I could also connect a grid tie inverter to the output of the MPPT 48V, but what grid tie will work with a 48VDC input?

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I know only a few GTIs with low voltage inputs, and most of them are hybrids. The GTI with the lowest input voltage that I know is the Fronius Galvo, and that needs 140V input to start up (which is too close to the max voltage of the MC MPPT). The other two options is the Infini, and I left this one for last due to fanboy status: The small Multiplus Compact (1200W) can operate as a hybrid and in hub-1 or hub-4 mode it can grid-tie, but even that is a 15k option and can't run without batteries. Micro-inverters are usually quite affordable (per unit at least) and step up from a lower voltage, but you can't put a whole 1kw array on one, usually limited to around 300 watts.

Looks like you have to call for a price on that SunPlug :-)

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1 hour ago, plonkster said:

Micro-inverters are usually quite affordable (per unit at least) and step up from a lower voltage, but you can't put a whole 1kw array on one, usually limited to around 300 watts.

Uhm, they are per panel, not 1kw string. Then you have the actual inverter they feed on top of that.

Per panel it is a cost per micro inverter plus the main inverter on the DB board. 

What is nice you can mix and match panels, each one on their own micro inverter, but T&C apply.

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Uhm, they are per panel, not 1kw string. Then you have the actual inverter they feed on top of that.

Per panel it is a cost per micro inverter plus the main inverter on the DB board. 

What is nice you can mix and match panels, each one on their own micro inverter, but T&C apply.

That's what I meant. You can't just wire your existing 1Kwp array into one.

Don't confuse optimizers with micro inverters. An optimizer is an mppt able boost converter with a dc output. The second stage -- making AC -- is done by a second inverter below. This is how the solar edge inverters work. By contrast, a micro inverter has both the boost and AC making stages in the same box sitting on the roof, each one individually tying with the grid. They're little GTIs.

Sent from my GT-I9195 using Tapatalk

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? Micro inverters produce 230 V directly, don't they? So no inverter at the DB. But as far as I know, they're not available as a stand alone thing, they are allowed integrated into the panel.

There is an Axpert model (so 60-115 Vdc MPPT input) that is grid tie, I think the V series. But I think they might require a battery, and have two inverters inside (a true hybrid), so I'd expect even a low end model to cost too much.

I believe that solar optimisers work on a 48 VDC bus. So the back end of that has to be. 48 V input grid tie inverter. So that might be economical and available.

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23 minutes ago, Coulomb said:

Micro inverters produce 230 V directly, don't they? So no inverter at the DB.

The small little inverter per panel cannot handle the intricacies of powering a house.

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1 hour ago, viper_za said:

If you have enough of them you should be okay with it ;)

R u going to try it then, see if it can be done and how without the inverter inside? :P

6 x 300w panels micro inverter is about +-R6k. 

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This is a seriously hard nut to crack.

 

Only price I can get on a Sunplug ECO 2 is R20k, and that is the last price from Current automation has, new shipment will be more. At that price its cheaper to use the money for  adding 8 panels to my Infini Array

Victron Multplus compact also doesn't look viable either at R16000

Infini won't work as its startup voltage is to high. My SF panels run at 82V each and are connected in parallel into the MC MPPT.

 Could I run 3 micro inverters from the MC 48V output in parallel?

I need to try complete this project for around R10k

 

 

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8 minutes ago, The Terrible Triplett said:

R u going to try it then, see if it can be done and how without the inverter inside? :P

Uhm...
Microinverter is the grid-tied inverter and mppt all in one (just small)
you connect a couple of them up together and magic you have enough to power the house.
Think you need to go look at the link Tinker left earlier.

22 minutes ago, The Terrible Triplett said:

6 x 300w panels micro inverter is about +-R6k.

Normally they start at 2k per inverter.
Please link the model you can get at 1k per inverter
 

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There is a lot of stuff on the market. Coulomb talks of a 48V model. Yup, you get one like that. Its not the same one as is used by Solar Edge for example.

The basic idea which all of them uses is to do per-module MPPT tracking. So much better yield. But sometimes there is more to it.

You have the boost stage, and then you have the AC-chopping stage. The English word "Inverter" is actually such a lazy word, the Afrikaans and German words do much better. A "Wisselrigter" or "Wechselrichter" emphasis the fact that it makes AC out of DC rather than vaguely talking about doing the inverse of something else (a converter, but you might not know that).

So the first inverters, the low-frequency models, made the AC first and then used a heavy iron transformer to boost it. The new inverters do it the other way round, they first do a DC-DC conversion to a higher DC voltage, and then make AC from that.

So if you combine this two-phase process with optimisers, that's when you get stuff like the Solar Edge system. They put the boost stage in the box under the panel, bring 450VDC into the house using a single DC bus, and make the AC on the ground. Using a boost converter in this manner has another advantage: You can do the same impedance-adjusting duty-cycle modification trick to track the MPP with very little extra effort.

Micro-inverters on the other hand puts the AC-making phase into the same box under the panel.

Your big GTIs do both on the ground. Well some do. Others (high end SMA) has no boost stage and you have to feed it with a very high DC voltage to make it work. So that's essentially the difference between the Fronius Galvo and the Symo. The Galvo has a boost stage. Obviously you get better efficiency if you skip the boost stage.

When people talk of "Transformerless inverters" they are either incorrectly referring to modern high-frequency inverters as transformerless (they aren't transformerless, they use a smaller transformer at a higher frequency), or they are talking about high-voltage GTIs.

There is also some debate going on about which split is best for longevity of the system. Some will argue that putting half or all of the electronics on the ground is better than putting them under the panel.

I don't think anybody uses an AC bus to bring the optimised voltage down to another inverter on the ground. There is no advantage to using AC as transmission in this case (unless you just make 230VAC RMS on the roof and be done with it). The size of the cable will be exactly the same, it only relies on the amount of current it has to carry... well not exactly, AC will actually fare worse: It has this thing called skin effect which requires a thicker cable. DC is better for the bus when you use a split system.

However you look at it, what is needed here is a GTI with a very low start-up voltage. I don't know of any. I only brought up micro-inverters because they are basically small GTIs with very low startup voltages and power throughput.

You kinda sorta need something in the middle of that.

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Thanks @plonkster ;)  EDIT: I forgot about the Renesola, that was also where the R1k price came from. Was filed somewhere in the back of my mind till I got konfussed.

 

Having just investigated these again @viper_za, where the price popped into my head http://www.sonopsolar.co.za/product/solaredge-p350-optimiser-350w-mc4-72-cell-1-2m/ mixing it all up with micro inverters, that I also investigated and got a quote for https://enphase.com/en-us/products-and-services/microinverters/family, which was quite stupidly high, the two got mixed up in my thoughts. Must think twice, I agree.

But it was a honest mistake, say I, publicly admitted ...

 

That did not require another snide comment.

33 minutes ago, TinkerBoy said:

Word of advice, use it don't use it. Check you facts before giving advice or only speak out of personal experience.

Jaco, I am trying my level best not to get into another public altercation with you here on the forum, so I am going to let this one also go and ask you very nicely, lets call a truce?

Let us rather help each other if we make a honest mistake, privately being even better, than trying to run each other down. It is not cool.

So can I ask you to please move on from the past and let you and I try and see if we can work together? Better than we both did in the past?

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Considering your budget, you may do better second hand. Some older inverters used lower voltage MPPTs, before it was fashionable to use long series strings. In fact a friend of mine has such an inverter, a Sun Profi that is now redundant, but that one requires a 48 V battery. (That battery will be used with a pair of Axperts, hence that inverter is redundant.)

The problem with that idea might be regulations; typically the older inverters are no longer approved for connection to the grid, as it costs money and time to maintain the certification with the various regulators.

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  • 2 weeks later...
On 9/23/2016 at 11:25 AM, Gidie said:

Thanks. 

They also have a 1K Grid tie inverter that cost 4K with the limiter and shipping. 

This could work if I used 2 DC Optimisers so the voltage does not exceed 90V as the open panel voltage is 112V

I also found this

https://www.aliexpress.com/item/1200W-inverter-PV-Voc-input-85-130v-High-frequency-isolation-solar-inverter-AC230V-50HZ-or-60Hz/32492506480.html

Fits all the criteria but $900 shipping to SA :(

I can have it shipped to Singapore, but not sure what duties and things are there.

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