Important Facts About Solar String Inverter
What is a solar string inverter? How do string inverters work? When is it advantageous to use a solar power inverter for every module string?
According to temperature, solar radiation and shadowing solar panels provide a different performance, what can lead to so-called mismatch losses. Solar string inverters are used to keep this down as much as possible.
Performance optimization with solar string inverters
In small solar PV systems, solar panels are connected in parallel to the solar power inverter. Smaller performance losses can be accepted.
In larger solar PV systems, the mismatch losses would be too great to ignore. Therefore, here solar string inverters are used.
Solar modules are connected in a series to form a PV string. Then, you connect
- every string to one solar string inverter or
- several strings to one solar multi-string inverter.
Due to these uses, mismatch losses can also be, for large solar PV systems reduced, but you can never completely prevent these losses.
The Differences to other solar power inverter concepts
The difference between a solar central inverter and a solar string or a multi-string inverter is the connection of individual solar modules.
In general, one can say that in solar string inverter systems, the individual solar modules are connected in a series to the inverter. However, in central inverter systems, the connections of modules are in parallel and central to the inverter summarized.
While solar central inverter is profitable in larger solar PV systems with similar orientation, solar radiation, and shading situation, The great advantage of solar string inverters is that you can bring together modules, which have similar conditions. This contributes to:
- reduction of cable losses
- allows to use smaller cable diameters and
- reduces die installation and operating costs.
However, up to a certain size of solar PV system, the additional yield of string concept, the higher acquisition and maintenance costs can not be compensated.
Advantages and disadvantages of solar string inverters
Performance losses
As already mentioned, the decisive advantages of solar string inverters are the reduction of mismatch losses.
Although there are solar panels with their own MPP-tracker, which adapts the performance of the individual solar panels to the offered solar radiation, these are very expensive.
Therefore, anyone who uses solar panels without integrated MPP-tracker should try with the aid of string circuit to minimize the losses. A complete elimination of losses is not possible with solar string inverter.
Plant size
In general, everyone should ask themselves, which efficiency they want to get out of a solar PV system. The answer to this will decide, how strong you want to act against mismatch losses or other energy losses.
One can say that in solar PV systems, which cover a surface of over 30 square meters, measures should be taken to minimize these losses.
Costs and price
It is also essential to choose a string inverter model, which has very high efficiency.
The higher the efficiency, the more expensive the solar string inverter is.
The additional expenditure should be recouped. Therefore, it is of particular importance, to establish with the aid of exact measurements and calculations if the additional investment in solar string inverter is profitable.
Additional functions, equipment, and types of installation
The solar string inverter reduces not only the mismatch losses. Modern string inverters also assume a variety of reasonable additional functions. Depending on the model, solar string inverters differ in their:
- output range,
- the input voltage ranges,
- input currents,
- efficiency levels,
- MPP inputs and
- in field of application (Indoor or Outdoor).
Depending on the model, cooling systems and ventilation facilities can be integrated into solar string inverter.
In particular, when the solar string inverter also serves as monitoring station of solar PV system with a connection to display or monitor, it will make sense to choose an indoor device. The cellar is an ideal location, there, it is cool, dry and usually dust-free.
If the solar string inverter is installed outside, then one should set up under certain circumstances a small garden shed for this.
Even outdoor models should be easily accessible and must be protected from rain and sunlight.
To know more about the different types of solar inverter see this article.
