An Overview of Photovoltaics

Common Photovoltaic System Components

➔Cell <Module < Panel < Array

➔Mounting Hardware: Mounts panels to roof with fixed-tilt; racking system is needed for
ground units and where there is a structural need; adjustable-tilt type; pole

Inverter: converts DC energy to AC energy; Inverters lose some power in the process of
converting DC to AC, so more DC energy is required to produce a certain amount
of AC energy.
Charge Controller: controls batteries from overcharging or undercharging
Batteries: Power Storage
Monitoring/Metering: Smart metering with digital readout of system performance.
Service Panel/Power Panel for Critical Loads (creates quality frequency for high-end
Wiring: conductors
Fuses/Breakers/Disconnect Switch: over current protection and safety features.

➔ AC: Alternating Current Alternating current is what the utility grid supplies and is found in
most homes. Alternating Current is a ‘kind’ of electricity in which the direction of flow oscillates
at frequent, regular intervals. Usually an inverter is needed to convert a solar array’s energy
from DC current to AC current.

➔DC: Direct Current PV modules or panels produce this “kind” of electricity, this is also the type
of current stored in batteries. Direct Current is electric current that flows in one direction only,
no alternating back and forth of electrons.

➔ Off-Grid Systems

1. Stand alone with DC loads only (no inverter), (direct drive pump and/or direct drive
2. DC loads only + Batteries
3. Hybrid with DC and AC loads + inverter + batteries and supplemental power system
(wind turbine or generator)
Definition of Off-grid: Also called Stand alone systems, are systems that operate
autonomously and supply power to the electrical loads independent of the electric utility
grid. Typically off-grid systems store energy in batteries. Off-grid systems are used when
connecting to a utility grid is too expensive due to remoteness of site.

➔On-Grid Systems

1. AC loads only + inverter (no batteries) + net metering back to grid.
2. Grid-Connected with AC loads only + inverter+ batteries+ separate distribution panel for
critical loads + net metering back to grid.
3. Grid-Connected with DC & AC loads + inverter + batteries + separate distribution panel
for critical loads + net metering back to grid.
Definition of On-grid: Also called utility interactive systems, do not use batteries, and feed
energy back into the grid. “An electrical power generating system that uses a photovoltaic
(PV) array as the primary source of electricity generation, and is intended to operate
synchronously and in parallel with the electric utility network. Such systems may also
include battery storage, other generating sources, and may operate on site loads
independent of the utility network during outages.

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