Photovoltaic system – island grid

The solar system shown here implements a so-called self-sufficient island network (“microgrid”) that is not connected to the public power grid. This island system is a demonstration system for the coupling of distributed independent energy producers. The concept is also known as “swarm stream”. This enables independent and spatially limited power supply networks to be implemented, for example to supply groups of buildings or small villages in remote areas. There are sample projects in Uganda and South Sudan.

Fig .: Island system consisting of PV modules, solar inverters (red), battery inverters (yellow)
and a diesel generator (green) as a reserve. Source

We use the system at Rhein-Waal University of Applied Sciences for demonstration and training purposes, especially in the “Environment and Energy” course.

Effects of the alignment of the PV modules to the sun or the partial shading of individual modules on energy generation can be practically investigated using the system. The control of the distributed solar generators as well as the monitoring of the entire system via the control bus must be learned in order to be able to run the system efficiently and in a stable manner.

The core of the stand-alone system is a battery inverter with battery storage. The battery inverter generates 230V alternating voltage from the battery voltage, which conventional 230V devices can feed as consumers.

The energy is supplied by four solar generators. Five photovoltaic modules (PV modules) each together with a solar inverter form a solar generator. The solar inverter converts the direct voltage of the five PV modules (approx. 110V) into 230V alternating voltage. The alternating voltage generated is then fed into the alternating voltage line to which the battery inverter is also attached. This can be used to recharge the battery.

The AC coupling of the generators and storage units enables greater distances to be bridged between the components and considerably simplifies the implementation of the distribution of the self-sufficient island network.

The commercially available polycrystalline silicon PV modules shown here have an efficiency of around 16% and a maximum output of 270 W.

More information

SMA Solar Academy: Inselnetzversorgung