question

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project-eco asked

Technical Capability of Victron ESS system where export must be zero


Can Victron Energy be used in the way I Describe below?

I want to take 35 KW's of power from the roof, pass this to a number of parallel Victron MPPT charge controllers. From here the energy will go in to a lithium battery. From the lithium battery there will be a parallel connection on to a grid connected inverter. The grid connected inverter will assess the loads in the property and use the energy storage and the available solar simultaneously to power the loads. It's very important that the inverter can be controlled as a function of measured demand rather than export. I'll say that again - It must work off demand not export.


I see people are having issues with battery charging in the UK with SMA and Victron where grid export is limited by throttling or limited to zero. The reason is twofold. Firstly, these energy storage systems work as a function of exported energy. Secondly, a 1-second compliance limit is enforced by the national grid. Generators must be able to switch off or throttle down power output before export capacity is exceeded. Within 1 second. The problem is, inverters are throttled down or turned off before the energy storage system had a chance to act as a load and open the switch. Thus, batteries are not receiving the full charge.


Inverters are throttled or turned off to stop export. But the export is the message which tells the battery inverter to turn on and charge. Because the inverters are throttled or turned off before the energy storage charger turns on, the system deems there to be no export available. The reality is, lots of surplus power has been turned off.


What would you suggest is the best solution for a grid connected system utilizing export management and energy storage? Can your solution act as above?


If we use a grid connected inverter, is there a way we can tell the inverter to ramp up and down to meet property demand?

ESSEnergy Meter
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1 Answer
Guy Stewart (Victron Community Manager) avatar image
Guy Stewart (Victron Community Manager) answered ·

Hi @project eco,

It's a complex set of questions, I would first suggest finding the support of a local distributor who has experience with Victron and your local wiring and grid compliance rules.

Victron MPPTs will charge the battery efficiently, regardless of what is happening with the grid.

If the battery is full, and grid export is disabled, then the MPPT will ramp down to maintain battery voltage.

If the inverter has some way to see the load, then it will discharge the DC bus to provide it, and then that will come from the PV first and then battery if there isn't enough PV.


It is not clear from your description how the loads are connected to the inverter.


Is it via the AC output on the MultiPlus?

Or

Is the MultiPlus AC Input wired into the grid, and connected to an energy meter wired before the grid utility meter and the loads are measured through the energy meter, and the MultiPlus is pushing back through the AC input to bring the grid import/export to zero?


I am presuming the issues you are seeing with other systems not using AC PV efficiently are where the AC PV limited export is constrained by a 3rd party energy meter that isn't part of the Victron system.

Then Victron is just looking for excess AC PV, measured as export, before using it to charge batteries. But that doesn't happen because export is limited.


However in your example you talk about using DC Victron MPPT charge controllers, which don't suffer from this issue at all.


This will also not happen in a Victron system and a AC PV inverter that has native zero export support where the zero export is managed by Victron, for example Fronius.


I am working on some training right now to help improve the description of this behaviour, for now there is also this documentation:

https://www.victronenergy.com/live/ess:design-installation-manual

https://www.victronenergy.com/live/ac_coupling:fronius

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