Hello, and welcome to this video
on the 5 most frequently asked questions
on photovoltaic installations for self-consumption,
in particular how they operate.
I'm here with my colleague Laurent Mischler
Hello!
We have received a lot of questions
on photovoltaic self-consumption.
We have selected the most frequent ones,
let's look at them together.
Let's go
1st question:
how do you switch the power supply
from the grid to the photovoltaic source?
In fact, there is no need to transfer the electricity supply
from one source to the other.
When solar panels produce electricity,
the electrical installation is powered
by both the grid, and the photovoltaic system.
This is possible because photovoltaic inverters
are designed to operate in parallel with the grid
Then, 2nd question:
how do you synchronize
the photovoltaic production with the grid supply?
Grid-tie photovoltaic inverters are current sources.
They do not provide voltage and frequency reference
by themselves.
When connected to the electrical installation,
they measure the voltage and frequency
at their connection point,
and deliver a power output
synchronized with this voltage and frequency.
Thus, the inverters do not generate a mismatch
or instability in the electrical installation.
Now, 3rd question:
How can you be sure
that the photovoltaic energy produced
is consumed by the loads,
and not reinjected into the grid?
The photovoltaic energy produced goes to the loads,
because the electricity takes the least resistant path.
The path to the loads, made of cables and busbars,
has a much lower resistance
than the path to the transformer and the grid.
Therefore, the loads
will consume the available photovoltaic production,
and will pull some additional energy from the grid,
as needed.
When the photovoltaic production
is higher than the loads' consumption,
the extra energy will tend to go to the grid.
I will discuss this topic in another video.
Oh great!
Now, question number 4:
What happens during the night?
Does the photovoltaic system consume energy?
At night, the photovoltaic system does not produce electricity.
Even though photovoltaic inverters are on standby,
they consume a little bit of electrical energy.
Do they consume a lot?
Usually, the night time consumption of photovoltaic inverters
is lower than 1 Watt.
To know the exact value,
you have to check their technical specifications.
Shouldn't we avoid these losses?
Standby power losses
can be avoided by disconnecting
the photovoltaic system during the night.
Anyway, this is rarely done
because disconnection requires the use of additional equipment
and a daily switching operation.
One last question for today:
does the photovoltaic system still operate during a grid outage?
No! As I said, grid-tie photovoltaic inverters
need a source that delivers
the voltage and frequency reference,
such as the electrical grid.
They are not designed to operate off-grid.
In case of grid outage,
the solar inverters disconnect rapidly,
as the voltage in the electrical installation
goes outside of the specified limits.
The electrical installation is no longer supplied.
This fast disconnection, less than 1 cycle
of the grid-tie photovoltaic inverters
also guarantees that the inverters
do not inject power into to the grid,
which is essential for the safety of utility workers.
Vanya, that concludes our FAQ session for today.
Thanks a lot for these detailed explanations!
My pleasure!
And if you have other questions,
you can check our other videos.
You can also download the latest edition of the Electrical Installation Guide,
which includes a dedicated new section
on photovoltaic self-consumption.
Thank you for your attention
and see you in an other video.
See you soon!