Solar Photovoltaic systems generate electricity by converting sunlight directly into electricity. The Photovoltaic cell consists of one or two layers of a semi conducting material, usually silicon which – when light shines on it – creates an electric field across the layers causing electricity to flow.
For a comprehensive visual on how solar panels work, watch this short Ted-Ed video by Richard Komp (2016).
Classification of rooftop PV systems
The most common way to differentiate a solar rooftop installation is via the connection to the electrical load/grid.
Grid tied / connected with reverse power blocking
The property is connected to the national grid in order to receive electricity, but any surplus electricity generated by the system is prevented from being directed back into the grid.
Grid tied / connected
Electricity generated can be used at the property and any surplus can be directed back into the grid. In some cases, this feed-back is compensated for.
Off-grid / standalone
The PV system generates electricity for use on-site, and operates completely independent of the national grid. In this case, it necessary to have additional components such as a charge controller and battery storage.