Lecture 5 – Solar PV System Components

Vocabulary flashcards covering key terms and definitions from Lecture 5 on solar PV system components, designed to aid exam preparation.

Solar PV Module

A packaged assembly of interconnected solar cells that converts sunlight into DC electricity.

Battery

Electro-chemical energy-storage device used to store excess PV electricity for later use.

Charge Controller

Electronic unit that regulates battery charging and discharging to prevent over-charge and over-discharge.

Inverter

Power-electronics device that converts DC from PV or batteries into AC at required voltage and frequency.

Balance of System (BOS)

All PV system components other than the modules, including wiring, mounting, protection, grounding, etc.

String (PV)

Series connection of PV modules that raises voltage to desired level.

Array (PV)

Parallel connection of module strings that increases current to desired level.

Junction Box

Enclosure on rear of a PV module where busbars terminate and bypass diodes are housed.

Bypass Diode

Diode placed across subsets of cells to route current around shaded cells and reduce power loss.

Shading Effect

Reduction of current, voltage and power when part of a PV module or string is shaded.

MC4 Connector

Standardized male/female plug set used for quick, weather-tight PV module interconnections.

MC4 Y-Connector

MC4 accessory that splits or combines conductors to create parallel PV connections.

Series Connection (PV)

Wiring modules end-to-end to increase voltage while current remains constant.

Parallel Connection (PV)

Wiring module strings side-by-side to increase current while voltage remains constant.

Monocrystalline Silicon Module

PV module made from single-crystal Si wafers; high efficiency, black appearance, higher cost.

Polycrystalline Silicon Module

PV module made from multi-crystal Si wafers; slightly lower efficiency, bluish color, lower cost.

Half-Cell Module

Module built with laser-cut half-sized cells to reduce resistive losses, improve shade tolerance.

Bifacial Module

PV module that captures light on both front and rear sides for additional energy production.

Albedo

Fraction of sunlight reflected by ground surfaces that can illuminate rear of bifacial modules.

Multi-Busbar (MBB) Cell

Solar cell design using many (e.g., 12) thin busbars instead of 4–5 to cut series resistance.

Mismatch Problem

Performance loss when modules or strings with dissimilar electrical characteristics are combined.

Depth of Discharge (DoD)

Percentage of a battery’s rated capacity that has been withdrawn during use.

State of Charge (SoC)

Percentage of remaining capacity in a battery; SoC = 100 % – DoD.

C-Rate

Rate at which a battery is charged or discharged relative to its nominal capacity (e.g., 1 C = full charge in 1 h).

Self-Discharge Rate

Monthly percentage of capacity a rested battery loses due to internal chemical reactions.

Cycle Life

Number of full charge–discharge cycles a battery can complete before capacity falls to 80 % of initial.

Lead-Acid Battery

Low-cost rechargeable battery using lead dioxide cathode, sponge lead anode and sulfuric acid electrolyte.

Valve-Regulated Lead-Acid (VRLA)

Sealed lead-acid design with pressure valves; maintenance-free, includes AGM and Gel types.

Absorbent Glass Mat (AGM) Battery

VRLA battery that employs fiberglass separators soaked with electrolyte for high-current use.

Gel Battery

VRLA battery whose electrolyte is immobilized in silica gel; better heat dissipation than AGM.

Advanced Lead-Acid Battery

VRLA battery enhanced with carbon additives to improve life and partial-state-of-charge performance.

Nickel-Cadmium Battery (Ni-Cd)

Rechargeable alkaline battery with nickel oxyhydroxide cathode and cadmium anode; high cycle life, toxic Cd.

Nickel-Metal Hydride Battery (Ni-MH)

Nickel-based battery using metal-hydride anode; less memory effect than Ni-Cd, sensitive to overcharge.

Lithium-Ion Battery

High-energy-density rechargeable battery using intercalated lithium in carbon anode and metal-oxide cathode.

Lithium-Metal Battery

Battery employing metallic lithium anode, often in solid-state designs for higher energy density.

Solid-Electrolyte Lithium Battery

All-solid-state Li battery replacing liquid electrolyte with solid ceramic or polymer for safety.

Battery Capacity (Ah)

Total charge a fully charged battery can deliver at rated current and temperature until cutoff voltage.

Days of Autonomy

Number of days a battery bank must supply load energy without PV generation.

Float Voltage

Voltage at which a fully charged battery is held to offset self-discharge without overcharging.

Float Charger

Charger that supplies current equal to self-discharge rate to keep battery at float voltage.

Charge Controller (Generic)

Device that manages PV-battery energy flow using defined charge and discharge set-points.

Voltage Regulation (VR)

Upper battery voltage limit at which a controller disconnects or throttles PV charging.

Voltage Regulation Hysteresis (VRH)

Voltage difference between VR and the point where charging resumes; prevents rapid cycling.

Low Voltage Disconnect (LVD)

Battery voltage at which controller disconnects load to avoid excessive discharge.

Low Voltage Disconnect Hysteresis (LVDH)

Voltage rise needed before controller reconnects load after LVD event.

Temperature Compensation (Charging)

Adjustment of battery charge voltage according to temperature (e.g., –0.005 V/°C per 2 V cell).

PWM Charge Controller

Series controller using transistor switching at fixed battery voltage; simple, lower cost, some loss.

MPPT Charge Controller

Controller with DC-DC converter that tracks PV maximum power point to harvest extra energy.

Shunt Charge Controller

Small-system controller that diverts excess PV current through a parallel switch to prevent overcharge.

Series Charge Controller

Controller that opens series switch to halt charging; suited for larger currents than shunt type.

Hybrid PV System

Grid-tied PV installation that incorporates battery storage for backup and self-consumption.

Critical Load

Essential electrical load requiring uninterrupted power during outages.

Non-Critical Load

Load that can be shed during outages to conserve battery power.

Off-Grid Inverter

Battery-based inverter operating independently from utility grid.

Grid-Tied Inverter

Inverter that synchronizes AC output with utility grid for energy export or self-use.

Hybrid Inverter

Inverter/charger that can interact with grid, PV and batteries in one unit.

Square Wave Inverter

Basic off-grid inverter producing square AC waveform; low cost, poor power quality.

Modified Sine Wave Inverter

Inverter output approximates sine wave with stepped waveform; moderate quality.

Pure Sine Wave Inverter

Inverter producing sinusoidal AC identical to grid quality; preferred for sensitive loads.

String Inverter

Grid-tied inverter connected to one or more PV strings; common in residential/commercial plants.

Central Inverter

High-power inverter that aggregates many strings for utility-scale PV plants.

Micro-Inverter

Module-level inverter converting each panel’s DC to AC for improved energy harvest and monitoring.

Ampacity

Maximum continuous current a conductor can carry without exceeding its temperature rating.

Voltage Drop

Reduction in voltage along a conductor due to resistance; kept under 3 % between PV and inverter.

Overcurrent Protection Device (OCPD)

Fuse or breaker that opens a circuit when current exceeds safe limit (≥ 156 % of PV Isc on DC side).

DC Disconnect

Switch that isolates PV source from inverter for servicing and safety.

AC Disconnect

Switch installed after inverter to isolate AC circuits from load or grid.

Grounding

Connecting system conductors or frames to earth to provide low-resistance fault path.

System Grounding

Bonding of negative (DC) or neutral (AC) conductors to ground reference.

Equipment Grounding

Bonding of non-current-carrying metal parts to ground to protect against shock.

Step Potential

Voltage difference between a person’s two feet when standing near energized ground area.

Touch Potential

Voltage difference between hand and feet when touching energized equipment while standing on ground.

Grounding Electrode Conductor (GEC)

Wire connecting system or equipment ground to the grounding electrode (ground rod).

Equipment Grounding Conductor (EGC)

Conductor that bonds enclosures and frames to grounding system.

Ground Fault Circuit Interrupter (GFCI)

Device that quickly disconnects circuit when it detects small line-to-ground current imbalance.

Lightning Rod

Elevated conductor providing preferred low-resistance path for lightning to ground.

Surge Arrestor

Protective device that diverts transient over-voltages (e.g., lightning) to ground.

Net Metering

Billing mechanism that credits PV owners for surplus energy exported to the grid via bidirectional meter.

Mounting System

Structural framework that secures PV modules to roof, pole or ground foundation.

Ground-Mounted System

Modules installed on racks anchored to the earth; easy maintenance, requires land.

Pole-Mounted System

PV array elevated on a single pole; small footprint, higher cost.

Roof-Mounted System

Modules attached to building roofs; space-saving, requires roof integrity checks.

Single-Axis Tracker

Mount that rotates modules about one axis to follow sun, increasing energy yield.

Dual-Axis Tracker

Mount that moves modules in two axes for maximal sun exposure throughout year.

Horizontal Single-Axis Tracker (HSAT)

Single-axis tracker with horizontal east-west pivot; suits low-latitude sites, high power density.

Vertical Single-Axis Tracker (VSAT)

Tracker with vertical north-south pivot; advantageous at high latitudes, needs more spacing.

PV Module Cooling

Methods to lower module temperature and mitigate efficiency loss of ~0.5 %/°C.

Passive Cooling

Cooling that relies on natural convection or radiation, no external power needed.

Active Cooling

Cooling employing powered devices like fans or pumps to remove heat.

Water-Based Cooling

Active/passive system spraying or flowing water over modules for superior heat removal.

Air-Based Cooling

Cooling system using ambient or forced air flow to dissipate heat from modules.

Rapid Shutdown Device (RSD)

Safety unit that reduces PV string voltage to ≤30 V quickly during emergency (e.g., rooftop fire).

PV Optimizer

Module-level DC-DC converter that maximizes individual module power, adds RSD and monitoring.

Skin Effect

Tendency of AC current to concentrate near conductor surface, increasing AC resistance vs. DC.

Copper vs Aluminum Conductor

Copper offers ~160 % higher conductivity and strength; aluminum is lighter and cheaper.

Multi-Core Cable

Cable containing multiple insulated conductors (cores) within one outer jacket.

Temperature Derating (Switches)

Reduction of switch current rating as ambient temperature rises to prevent overheating.