question

frank-in-thailand avatar image
frank-in-thailand asked

Most basic question ever :-)

I have a strange but simple basic question.

It appears there are 2 choice for solar.

Grid tied: passing through the AC from the grid as much as needed, and provided solar to reduce the actual used electricity from the grid.

To my knowledge most say 3kw grid tied are limited to 3kw solar, but if you use 5kw, it will use the 3 kw from the solar, and 2 kw from the grid.

It doesn't stop or burn or other trouble when you ask more then it is rated.

Great setup, but doesn't work with a battery. (Or uses the grid as Giant battery)


+++++


Hybrid/ inverter

Apparently invented to be used "off grid"..

It provide the electricity via battery and solar, can add some from the grid, but is limited to it's own capacity.

Say you buy a 5kw, but want to use 6kw.. you are screwed. It doesn't feed trough. (98% of china available option)


That brings us to Victron.

Pass trough 50A or 100A according to the specification.

If we choose 8kw multiplus or quattro.. Thailand is HOT, 35-45c..

And we want to use 10 kw for say an hour.


The specification informs me that we won't be getting 8kw at 40c.

(Rated 8kw at 25c, higher temperature is reduced performance)


What will happen if you ask more then it can deliver???

As that is when the passthrough gets important, yes?


The China ones simply stop working if you ask 10kw on an 8kw inverter.

Screaming "overload" and reboot after 5 minutes or so.


If you can provide 7 or8 kw, and you ask 10 for a too long period of time.


3 possible situation:


- The inverter will stop, electricity will stop. Probably reboot itself after a few minutes.. Power outage even when there is AC from the grid available.

(Typical China inverter)


- The inverter protect itself and stop providing power, yet, the passthrough should continue to be available, so there isn't any problem for power availability.


Best option would be:

- The unit provide the 7kw (or maximal what it can) and provide the rest from the grid.

So if it can give 7kw continuous, it will continue to provide the 7kw, and get 3 kw from the grid when you ask for it.


As it can do 100A passthrough in theory a peak of 22kw is possible, where it provides as much as it can (battery/solar) but..

Does provide the 22kw.


Not realistic as we never use above 10kw, sometimes a peak when a pump or other electric motor starts.


++++++


Strange and simple question as it's something that should be known and promoted...

Yet...


I'm not a total NoNo, working with solar and lithium for the last 4 years.


My setup is off grid, and that prevent all kinds of trouble my friend is having.

(14kw solar, 15kw inverter, 55 kWh lithium)


Yet, everywhere on forums I see people struggling when connected to the grid.

Is this standard for "all China brand"?

Is this the same with Victron?


So please, can you shine a light on this basic question?


Thanks!!!


Frank


What we need is Kinda like an e-bike :-)

I can go with a bike down hill 60km, Easy.

Yet, getting up hill is a challenge.

So.. e-bike, up hill...

We go 25km as that is the max it can deliver.

Great.

Now going down hill... I still should be able to go 60 and not be limited by the E-bike to 25km!!


Yet most China inverters do exactly this.

They are taking all "control" and aren't what they are supposed to be, an assistant.

ESSoffgridgridcurrent limit
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frank-in-thailand avatar image frank-in-thailand commented ·

pass-through current... How does it work?


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Alexandra avatar image
Alexandra answered ·

@Frank in Thailand

The unit you choose will pass through its max transfer ability, unless you set the input current down on the inverter itself. Then it will power assist from the battery if you exceed the input limit.

Air condition the room, heat derating problem will be solved. It is generally cheaper to air con that size up the system.

Install ESS, i added the tag, some resources should appear on this page for more 'light' reading.

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frank-in-thailand avatar image
frank-in-thailand answered ·

Thank you for the reply.


Basically what happens now with the China inverter... If I use more then 10kw the system turns in a fault, and stops, also stopping all electricity.

Reboot after 5 minutes and that's it.


The spikes is the biggest problem.

There is grid, solar and battery.

We like to continue to use the grid like it has no inverter installed.


The China inverter sits between the grid and house, and if we use more then the unit is rated for... Poef.. dark.


We like an inverter that adds electricity to the house, bit doesn't limit the normal house connection (63A)


While it can be solved by installing 15kw units... They are expensive and have high own electric consumption.

(Roughly an inverter (also victron) use 100 watt per 5kw possible power.

15 kw unit will eat 300w 24/7.


(Yes, I know the specification sheets, we are talking real life here hahaha...

Where there is a continuous power draw of say 1000-1500 watt.. so no sleeping standby numbers.


1500 watt on a 5kw unit will draw 1600

1500 watt on a 10 kw unit will draw 1700

1500 watt on a 15kw unit will draw 1800


8-10 kw unit is realistic to buy.

For the power consumption and what the inverter needs to provide.


All heat aside...

As there is abundance of grid available, what will the victron do when we ask more then it's rated power??


Are you absolutely sure it provides as much as it can (till rated capacity and temperature restraints) and will provide the rest from the grid??


Or will it beeb, red light and "overload"??

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Michelle Konzack avatar image Michelle Konzack commented ·
Where did you got this:

Roughly an inverter (also victron) use 100 watt per 5kw possible power.

My MultiPlus-II 24/5000 has a self consumption of around 23W.


The Victron Inverters (no matter which one) will provide the power for which it is rated.


If you realy need 10kW even in a grid failure, maybe you go with a 8kVA MultiPlus Inverter and if you see, that you exceed the limits add a second one in parallel. I assume you use with this power 48V Batteries.


If you need additionally a GenSet, use the more expensive Quattro.

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frank-in-thailand avatar image
frank-in-thailand answered ·

Ps... I'm doing some "light" ready now and watch the videos..

That will take a few hours to absorb all :-)


Thanks

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ejrossouw avatar image
ejrossouw answered ·

Hybrid grid parallel systems are actually becoming more prevalent today and functionality depends on the individual manufacturer. Interestingly, you will find some seldomly have critical loads (off-grid) capability and may only offer it as an option. This makes installation very simple and overcomes the limits you mentioned. I find that many domestic customers use the Victron systems in this way (only ACIN used) given their grid is stable and additional requirements for earthing and rewiring etc. is seen as an unjustifiable investment for critical loads functionality.

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