NCCER Solar PV key terms

The process in which certain semiconductor materials convert absorbed light energy directly into electrical current, producing a voltage difference across the material's junction when exposed to sunlight.

The smallest electricity-producing unit of a solar module, typically a thin wafer of silicon that generates roughly half a volt of direct current under standard sunlight.

A factory-assembled, weather-sealed package of interconnected PV cells laminated under glass and framed for structural support, rated by its DC power output under standard test conditions.

The complete assembly of one or more PV modules wired together electrically and mounted as a single power-generating unit within a solar energy system.

A series electrical connection of multiple PV modules in which the same current flows through each module and the voltages add together to feed the inverter or charge controller.

A wiring method that links components end to end so current follows one path, adding voltages while keeping current constant throughout the circuit.

A wiring method that connects components across common positive and negative nodes, adding currents while holding voltage constant across each branch.

The laboratory reference values of 1,000 watts per square meter irradiance, 25 degrees Celsius cell temperature, and a specified air mass used to rate module nameplate power.

The instantaneous power of sunlight striking a surface per unit area, commonly expressed in watts per square meter, which directly drives a module's current output.

The accumulated solar energy received on a surface over a period of time, usually reported in kilowatt-hours per square meter per day and used to estimate production.

The compass direction a PV array faces, measured in degrees from true north, which strongly influences how much sunlight the modules receive each day.

The angle of a module's face measured up from horizontal, adjusted during design to balance seasonal production, snow shedding, and array spacing.

The moment each day when the sun crosses the local meridian and reaches its highest point, producing the shortest shadows and typically the peak irradiance.

The site evaluation process of identifying obstructions, measuring their shadow paths, and predicting production losses before finalizing array locations and string layouts.

The designed distance between adjacent module rows, set so that winter shadows from one row do not fall on the next during a chosen no-shade window.

A diode built into a module's junction box that provides an alternate current path around shaded or failed cell groups, limiting hot spots and reducing lost output.

A diode placed in series with a string or module to prevent reverse current from flowing back into it from other parallel sources, such as at night or under heavy shade.

A localized overheated area on a module caused by a failing cell or cell group that restricts current while the rest of the module forces current through it.

The operating point on a module or array's current-voltage curve where the product of current and voltage is greatest, yielding the highest power output for given conditions.

An inverter or charge controller function that continuously adjusts its operating voltage to keep the array at its maximum power point as irradiance and temperature change.

A graph plotting a module's output current against voltage across the full range from short circuit to open circuit, used to evaluate performance and diagnose faults.

The maximum voltage a module or string produces when no load is connected, measured with a meter and used to verify string voltage and inverter compatibility.

The current that flows when a module's output terminals are connected together with zero resistance, representing the highest current the device can deliver under those conditions.

A rated value describing how much a module's voltage or power changes per degree Celsius of cell temperature, typically reducing power as cells heat up.

The actual operating temperature of the PV cells inside a module, which rises above ambient air temperature due to sunlight and restricted airflow behind the array.

The design calculation that selects how many modules to connect in series so array voltage stays within the inverter's window across expected high and low temperature extremes.

A device that converts the direct current produced by a PV array into alternating current suitable for loads or the utility grid, often also providing monitoring and safety functions.

A protective function that stops an inverter from energizing a grid circuit after utility power is lost, preventing hazards to line workers and equipment.

A required safety feature that reduces conductor voltage within an array to a safe level quickly after activation, protecting firefighters and service personnel.

A PV installation electrically connected to the utility grid, exporting surplus power through a net meter and relying on the grid for backup when production is low.

A utility billing arrangement that credits a customer for exported solar electricity, typically offsetting kilowatt-hours consumed at other times on the same meter.

An enclosure where multiple PV source circuits are paralleled onto common busbars, often housing fuses, breakers, and surge protection before conductors run to the inverter.

A manual switching device that opens a circuit so equipment can be safely serviced, required at defined locations such as between the array and inverter and at the service panel.

A safety procedure in which energy sources are switched off, locked, and tagged so they cannot be re-energized while workers install or service equipment.

A dangerous release of energy caused by an electrical fault through air, producing intense heat, light, and pressure that can severely burn or injure workers.

Worn gear such as insulated gloves, safety glasses, hard hats, and arc-rated clothing that reduces injury risk during electrical work and rooftop installation tasks.

Systems such as harnesses, lanyards, anchors, and guardrails used to prevent or arrest a fall when working on roofs or elevated mounting structures.

A hole made through roofing material to attach mounting hardware, which must be flashed and sealed properly to prevent water intrusion and maintain the roof warranty.

A weatherproofing layer or fitting installed around roof penetrations and mount bases to direct water away and keep the building envelope watertight.

A mounting approach that attaches modules directly to roof attachments or clamps without long support rails, reducing material use and installation time on some roofs.

The gap maintained between modules and the mounting surface, which allows airflow for cooling and drainage and provides space for wiring and service access.

The structured process of inspecting, testing, and documenting a completed PV system to confirm it is installed correctly and performs as designed before handover.

An inspection technique using an infrared camera to reveal temperature differences that indicate hot spots, loose connections, or failing modules during commissioning or maintenance.

A safety circuit that detects current leaking from the PV conductors to ground and interrupts the fault to prevent shock and fire hazards.

A conductor that bonds non-current-carrying metal parts such as frames, racks, and enclosures together and to earth, providing a low-impedance fault return path.

A conductor or listed device that electrically connects metal parts of the array and mounting structure so they remain at the same potential and clear faults safely.