There are several different types of off grid solar power systems. The first type of solar energy system is one that would typically be used in a caravan or boat and would typically be a ELV system running either 12 or 24 volts of Dc power to specific appliances. The second type of system which is more common in a residential applications is a solar system that uses a charge controller and inverter and creates a standard 240 volt AC grid output. This means houses can use standard off the shelf electrical appliances. Modern inverters such as the Sunny Island from SMA incorporate functions of both and inverter and a charge controller and regulate the relationship between the various components in the system.
On the generator side, any number of renewable or conventional energy sources can be incorporated including solar, wind, diesel or batteries. Alternating current grids can be expanded without specialised technical knowledge and using standard components that are available everywhere. Compared to components for direct current grids, these components are considerably cheaper because they normally have to carry higher voltages but also much lower currents. There is also much more planning flexibility involved since even large distances between the generators, batteries and consumers can be implemented. Moreover, the connection of generators and consumers in alternating current grids is possible practically at any random point in the network - thus providing optimum conditions for subsequent expansion.
The Grid and Battery Management
The central component of the stand-alone grid is the battery inverter. In its role as grid former and manger, it maintains the stability of the AC grid and ensures that voltage and frequency.