Balcony power plants consist of solar panels and an inverter. As a rule, these plug-in systems cannot be used in so-called isolated operation, ie the generation cannot be used directly, for example to supply an electrical device with it - without first going through the 230V power grid. This article explains why this is the case and what possibilities there are nonetheless.
There is a relatively large pond in the vicinity. One day the owner asked if he could use a balcony power station to operate the pond pump. Unfortunately, this is not possible with the usual systems , although one could imagine using a multiple plug to connect both the balcony power plant and the pond pump.
The inverter is missing the grid frequency
The solar modules first generate direct current, which is converted into alternating current by the inverter. The difference between direct current, where there is always "plus" on one cable and "minus" on the other, is that with alternating current there is a constant exchange between plus and minus. This happens about 50 times per second. The inverter needs a mains connection so that it gets the clock from it (the 50 hertz) if this clock is available, then the electricity supplied by the solar modules can actually be used as alternating current at the plug.
It is part of the protective function against electric shock that the inverters approved in Germany always need the power grid as a clock generator, since this is the only way to really ensure that you do not get an electric shock when you reach for the plug.
With a classic inverter of a balcony power plant, no 230 volt electrical device can be operated directly. It must always be connected to the power grid so that the electricity generated can actually be used.
Island systems - disconnection from the power grid
So-called off-grid solutions provide the option of supplying a 230V device with power directly. The pond pump could be operated with solar power. This alternative is always used when the electrical device is not able to be operated with direct current. Some devices actually offer this option in the outdoor area, the corresponding connection is then usually called a solar connection. With a solar connection, however, an inverter is no longer required, since the solar modules are connected directly to the device.
Other devices that do not have this option require a voltage converter, which provides the 230V (and alternating current). A memory/battery is mainly used for buffering, since very few devices like it when, for example, there is suddenly less voltage (and power) because a cloud appears in the sky.
The disadvantage of these solutions is that the electrical devices that are supposed to be supplied with electricity only get electricity when either the sun is shining or the battery still has a charge.
In the next Corrently newsletter, there will be an article by Björn, who was able to learn in winter in a remote hut in the forest (without electricity) that snow can also be found above ground.
The small solution is "hybrid"
If you take a power station , you can kill two birds with one stone, because these devices have an input directly for the solar modules, a memory and - if there is snow - you can also charge them from the "normal" power grid if necessary. The downside here is that these devices don't exactly come cheap.