Gdańsk, 4 paź 2023
Autor:
Klaudia Kostogłód

Introductory Information:
● The household power supply cannot be limited.
● The solar panel-generated current is used first.

If electricity is being generated by the solar panels, it will be consumed by the household first.
If the household does not require it, the excess electricity can be used to charge the car
connected to the charger.

The current transformer placed at the main connection measures the electricity consumption
for the entire house with chargers. The electricity generated by the photovoltaic system
through EEG is seen as 'negative load,' which means that if the house's consumption is 20 A
and 10 A is generated by the photovoltaic system, then the consumption balance seen by the
transformer is 20 A - 10 A = 10 A. In this situation, EEG sees the house's consumption reduced
by what is generated by the photovoltaic system.

Case Description:

Let's assume that in the above diagram, the main connection's protection is set to 25 A.
The house, represented as loads (No. 6), consumes 17 A, and the car connected to the
charger (No. 7) consumes the remaining 8 A.
At this moment, the house's connection is at its maximum load. The sky is cloudy, and the
photovoltaic system is not generating electricity.

When the sun comes out and the photovoltaic system starts generating 2 A, EEG sees:
25 A - 2 A = 23 A of consumption. At this point, EEG detects that there are an additional 2 A
available. The car can use them if needed and it will increase the auto consumption level of
the charger. It will happen if the charging station is not currently drawing the maximum
configured current.

Seeing that the sun is shining, the user can turn on additional household appliances (e.g.,
washing machine, hair dryer), increasing the electricity consumption of the house at the
expense of charging the car, which may even be temporarily paused if the available current for
charging drops below 6 A.

If neither the house nor the charger needs these 2 A generated by the photovoltaic system,
the surplus is returned into the grid.