Solar panels produce simple form of electricity which is called DC (directed current) where polarity is constant all the time. This means that solar panels have a positive wire (the one with the small red ring) and a negative wire.
Power point tracking
In your electricity grid the (average) voltage is more or less constant. The panels, however, produce a varying voltage depending on the light intensity an on the current you draw from them. The voltage will be between 0 and 50V and the power they deliver is always the product of current and voltage; this product can be optimized by drawing a certain amount of current. A piece of software and hardware inside the inverter, called the “power point tracker” constantly tests how much the voltage of a panel (or a string of panels) will go down if a little bit more current is taken out. And how much the voltage would rise if less current were drawn.Thus it identifies the “optimal power point” where the product of voltage and current reaches its maximum.
In an ES-Micro system each panel ist directly connected to a micro inverter. Every micro inverter manages four panels and sits close to them. The inverter has an individual power point tracker for each panel. The inverter output is a sine voltage of 220V which fits exactly your AC grid. Therefore micro-inverters have plugs which can be put directly into a wall socket – or in our case into a construction site switch box which has several sockets combined with dedicated fuses.
An ES-Hybrid system has only two power point trackers. Each of them is connected to a number of panels which are linked in a row. The inverter is typically placed some 10 or 20 meters away from the panels. On its output side it produces a so-called 3-phase AC output, which means that you get three times 220V but with a phase difference of 120°.
If the inverter is connected to the grid it adapts perfectly to the grid so that it can insert its energy into the grid without disturbing the many devices which are taking energy out of the grid. This means that you will see some (minor) voltage differences between the three phases. Also the frequency may deviate by 0.1% or so from the perfect value.
If the grid is down the (battery) inverter will produce AC 220 (single phase for ES-Micro or three phase for ES_Hybrid). This will be a “homegrown” sinus wave of 50Hz and more or less exactly 220V. In the moment when the grid returns the inverter must adapt itself instantenously to the grid before it can be reconnected. This will happen automatically, so you do not have to care about.
Switching over to “island mode” happens really fast, typically in less than half a second. Once the maion grid has been separated from your home your solar system can deliver energy from its battery. It can also provide enetrgy (and/or refill the battery) if there is enough sunlight.
When the official grid comes back there will be a series of switching steps during which your loads will not have power for two or three seconds. After that your home is reconnected to the power grid.
You can then draw energy form the grid for your loads, you may even be able to refill batteries form the grid.