Solar fundamentals
Before you touch a panel on a job site, you need to understand why the system works, not just how to wire it.
How photovoltaic cells convert sunlight
A solar cell is a semiconductor junction. When photons strike the silicon, they knock electrons loose and push them through the circuit. That flow of electrons is direct current. The inverter on every residential and commercial install converts it to alternating current so it can feed the grid or the building's load.
Understanding this matters because it tells you what goes wrong. A shaded cell, a cracked panel, or a loose connection all interrupt that electron flow in ways you can trace if you know the physics behind it.
DC versus AC on a real system
Everything from the panels to the inverter is DC. Everything after is AC. The disconnect between those two sides is where most commissioning mistakes happen and where most safety protocols focus.
As a pre-apprentice, you will work on both sides under supervision before you touch either independently. Your IREC credential requires you to demonstrate safe working procedures on both. Know which side you are on before you pick up a meter.
System components you will encounter
A standard residential install includes modules, a racking system, a combiner box, an inverter, a production meter, and an AC disconnect. Utility-scale sites add string inverters or central inverters, monitoring equipment, and often battery storage.
Your first week on a crew will be spent recognizing components and understanding their function before you help with installation. Ask questions during that week. It is the fastest way to build the mental model that makes everything else easier.