Panels convert sunlight into electricity. The electricity is direct current (DC).
Panels are connected in strings of 9 to 25 that bring the DC voltage up to 300-500 VDC.
The central inverter converts the DC to AC and conditions it for grid interconnection. The AC connection is 240 AC single phase or 480 AC three phase into breakers in the service panel. A three-phase system provides a slight boost in efficiency.
Panel Optimizers / Micro Inverters
A microinverter or panel optimizer manages a single panel. These units are useful when an array has periods of shading or when you only need a few panels. By contrast, a central inverter manages the entire string of 10-12 panels in an array. When a single panel is shaded, the entire string is compromised. A microinverters or optimizer system will constantly optimize the entire array.
The National Electric Code (NEC) 2014 requires rapid shutdown of all high voltage sources on a rooftop. Only Solar Edge and microinverter systems can meet this requirement.
The Solar Edge panel optimizer system has dominated the solar industry for the past few years, especially on rooftops. The cost for the inverter and optimizers is less than any microinverter or central inverter system.
The utility company replaces your standard meter with a bi-directional meter. This measures energy delivered (DE) and energy returned (RE). These two numbers determine the netmetering balance at the end of your billing period.
All inverters have a display that indicates operation of the system. It will show system power (watts), grid conditions, energy produced, and voltage.
There are optional remote monitoring systems that will send a wired or wireless signal to a remote location that will allow you to monitor system performance.
There are both AC and DC disconnects required to safely shut down and restart the system.
All panels and racking systems are electrically bonded together and connected to a single earth ground point. The WEEB (Washer, Electrical Equipment Bonding) system insures that all components have adequate electrical bonding.
Panel Angle and Direction for a Fixed Array
The ideal direction is true south with a tilt angle between 30 and 35 degrees. This will provide the highest energy production for the year.
Modern solar panels produce significant energy off-axis. Tilt angles 20 degrees from ideal (50 or 15 deg), will produce 95% of maximum. Panels pointed 30 deg east or west of true south will produce 90-95% of maximum.