So in regular operation, connected to grid your micros are fully operational though right?
DC coupling is not bad, I guess.
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Ampster
Renewable Energy Hobbyist
Yes because they just pass through the SolArk and serve the loads and battery charging and export any excess to the grid. Actually their output gets mixed with the DC coupled solar that gets inverted and some mix of both gets exported.
Ampster
Renewable Energy Hobbyist
Yes, that is exactly how a mix of DC coupled and AC coupled solar can be implemented optimally in my situation.
Nice. What are some things you liked better about the radian?
Ampster
Renewable Energy Hobbyist
Actually it was a Skybox, but did have a Radian at another home and the Skybox offered everything All in One and much better TOU scheduling than the Radian. In the end I could not get Outback to accomodate closeed loop communication with my BMS and that was important to me. I did accomplish that with the SolArk which also improved on the TOU scheduling. I recently migrated from my DIY pack with an Orion JR2 BMS to Pytes V5 batteries and as I mentioned I am now using my pack more actively than with the DIY pack. They are almost the same size and I don't have a rational explanation.
Yep.
If most of your usage is PV to grid, AC coupling makes a lot of sense in terms of efficiency.
If most of your usage is solar to battery then battery to load, DC coupling makes a bit more sense.
I would also add that the primary driver of efficiency in a standard nonisolated converter is similarity in voltage, input to output. A 500 volt to 48 volt converter isn't going to be very efficient, but a 500 volt to 400 volt converter is a lot more efficient. Same thing with conversion to 240 volts AC. So high voltage systems will help with DC coupling efficiency.
If most of your usage is PV to grid, AC coupling makes a lot of sense in terms of efficiency.
If most of your usage is solar to battery then battery to load, DC coupling makes a bit more sense.
I would also add that the primary driver of efficiency in a standard nonisolated converter is similarity in voltage, input to output. A 500 volt to 48 volt converter isn't going to be very efficient, but a 500 volt to 400 volt converter is a lot more efficient. Same thing with conversion to 240 volts AC. So high voltage systems will help with DC coupling efficiency.
Copy that. Sounds like the solark is an improvement in almost every way. I think a lot of these boxes are really good, but hampered on the software side
olivinelife
New Member
You're missing the factor of price/TOU. It's increasingly worth it to take the conversion losses for battery storage because the $/kWh value of that energy is so much higher in the evenings for typical TOU structures.
You can thank non-DIY solar for that!
97.5% per the spec sheet.
A string inverter will be as good as a microinverter. They both do the same job, PV to AC, so why wouldn't they be similar in efficiency?
Are you accounting for the clipping since microinverters are often less power than the panels they are attached to.
For PV to AC, microinverters and string inverters are going to be basically the same. String inverters will less often be clipping since they are less often installed derated.
For PV to battery to AC, string inverters will be more efficient. They convert to AC only once, not twice, and AC conversion has loss.
Mike C.
The solark has charge controllers so they charge the battery and the solark then has to invert from battery to AC to run loads or power the grid.
Looking at the images In this thread, the efficiency is around 93-94% at high output
Post in thread 'Sol-Ark 15k Current Capabilities' https://diysolarforum.com/threads/sol-ark-15k-current-capabilities.78308/post-1002422
Ampster
Renewable Energy Hobbyist
Yes that is where my biggest economic return comes from. This time of year I get credit for export at those peak rates and the SolArk helps me avoid importing any kWhs at those rates.
maybe the answer is to have both ac and dc coupled pv
That is not how it works when PV is available.
The MPPTs make the panel voltages into the desired voltage for the AC inverter (usually about 350 volts DC which is optimum for making 240 VAC and why making strings that produce about 360 volts DC is best for MPPT efficiency). There is no going through the battery for PV to AC.
The battery charger works from the MPPT output voltage. The battery discharge runs through a booster to make the 360 volts DC for the inverter. The battery path is not involved in the PV to AC direct path. In this way, the string inverter is really just a big microinverter, same energy conversion process, but with a battery charger and booster to the side.
This is one reason why inverters with high voltage batteries are more efficient, the battery buck and boost conversions are more efficient than doing it at 48 volts, and cheaper since current is what drives cost for the most part.
This design is also why an inverter can have 12 KW AC output (the size of the AC inverter) but take in 18 KW of PV (like the EG4 18KPV). 6 KW is being used by the battery charger separately from the AC power path.
Basically, the AIO hybrid is NOT a battery charger followed by a battery inverter. There is a direct path of PV to AC.
When there is no sun, then the system has to charge the battery during the day and then use the battery during the night. But this is done with more efficient DC conversions than doing AC twice like a microinverter.
Mike C.
Fair enough. However my point stands that a battery inverter is not going to be as efficient as a pv inverter at high output.
Also, while power may be coming directly from the mppts without hitting the battery first,my belief is it's still being converted to 48v DC for the inverter section to do it's thing, unless you are telling me that the inverter can convert both 360v DC and 48v DC to AC, which I doubt.
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Vigo
Solar Addict
In an all in one the inverter is feeding from high voltage DC bus. It's impossible for the inverter to work off 48v without stepping it up first. But, in situations where the solar power can cover the entire load, no or almost no 48v power is being stepped up and fed to the inverter.
ok i think i understand. so the inverter is always converting from high voltage dc to ac. either directly from mppt, or by stepping up 48v to the high voltage and then inverting that to AC?
Vigo
Solar Addict
Yes, exactly. The MPPT has its own buck/boost converter function to always spit out power onto the DC bus at correct voltage. Then there is a buck/boost converter which can either a: step voltage from AC input down to charge batteries, or b: step voltage up from batteries onto dc bus to feed inverter.
Thus, most all in ones cannot power loads from AC input and battery power simultaneously because each process requires use of the buck/boost converter and there is only one to share, so it can power loads from either AC input or battery power but not both simultaneously.
Thus, most all in ones cannot power loads from AC input and battery power simultaneously because each process requires use of the buck/boost converter and there is only one to share, so it can power loads from either AC input or battery power but not both simultaneously.
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Right, I am just speaking for efficiency. Things like load shifting, zero-export times or even a good sale on microinverters will change the economics.
Ok I get this now. One more question- what path does pv DC take to battery? So it first goes from mppt to hv DC bus, then is there a converter that steps that down to 48v DC?
DIYrich
Solar Wizard
Correct.
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