Views: 0 Author: Site Editor Publish Time: 2025-07-17 Origin: Site
The photovoltaic system converts light energy (solar energy) into direct current (DC) electricity via PV panels, then converts it into alternating current (AC) electricity via an inverter, finally delivering it to the grid or for local load use. The mounting structure and accessories (junction boxes, connectors, cables, etc.) are essential structural support and electrical connection components enabling this energy conversion and transmission process.
PV Panels (Modules):
Role: The system's starting point, the core power generation unit. Uses the photovoltaic effect to convert sunlight directly into direct current (DC).
Electrical Characteristics: A single panel produces limited voltage (e.g., 30-50V DC), current (e.g., 8-12A), and power (e.g., 300W-600W+).
Junction Box:
Current Collection & Output: Collects the current from the series-connected cells inside the PV panel and outputs it via positive (+) and negative (-) leads.
Bypass Diode: Critical electrical component! If a panel is shaded or damaged, reducing its output, it can become a "bottleneck" in the series string, not only failing to generate power but also heating up (hot spot effect). The bypass diode allows current to flow around the underperforming panel through the diode itself, ensuring current from the other healthy panels can pass through. This protects the module and enhances overall system efficiency.
Connection Point: Provides standardized interfaces (usually MC4 sockets) for easy connection to other panels or cables using cables and connectors.
Location: Typically mounted on the back of each PV panel.
Role:
Accessories - Cables & Connectors:
Inter-panel Connection: Uses pre-made short cables with MC4 plugs ("jumpers") to connect the positive (+) terminal of one panel's junction box to the negative (-) terminal of the next panel, achieving series connection (increases voltage). Can also be used for parallel connection (increases current), but requires appropriate combining methods.
String Output: Routes the positive (+) and negative (-) outputs of a series-connected string of PV panels (called a "string") via longer PV DC cables towards a DC Combiner Box or directly to the inverter (for small systems or string inverters). These longer cables are "string cables".
PV DC Cables: Specially designed for outdoor PV environments: resistant to high temperatures (90°C), UV radiation, weathering, and flame retardant (typically certified PV-specific cable like TUV PV1-F). Includes positive (+) cable and negative (-) cable.
PV Connectors: Most commonly MC4 or compatible types. Designed as weatherproof, touch-safe, locking connectors.
Types:
Role:
Accessories - DC Combiner Box:
String Combining: Combines the DC outputs of multiple PV strings (e.g., 4, 6, 8, 10, 12, 16 strings) by connecting them in parallel.
Protection: A key protection point on the DC side.
Output: The combined DC positive (+) and negative (-) outputs are routed via heavier gauge DC cables to the inverter.
Fuses/DC Circuit Breakers: Provide overcurrent protection for each input string. Prevents fault current from other strings "backfeeding" and damaging the PV panels in a faulted string if it shorts.
Surge Protection Devices (SPDs): Protects against lightning-induced surges on DC lines damaging downstream equipment like the inverter.
Disconnect Switch/Isolator: Allows safe disconnection of the DC side for maintenance or emergencies.
Location: In string inverter systems, typically installed near the PV array and inverter (e.g., on the roof, next to ground mounts, or in a switch room).
Role:
Inverter:
DC to AC Conversion: Converts the DC electricity generated by the PV panels into AC electricity compatible with the grid or local loads (e.g., 220V/380V, 50Hz).
Maximum Power Point Tracking (MPPT): Continuously monitors and adjusts the DC input operating point to keep the PV array operating at its maximum output power, maximizing energy harvest.
Grid Interaction (for Grid-Tied): Monitors grid voltage and frequency for grid-tied systems, ensuring output current is synchronized with the grid to meet interconnection requirements. Automatically disconnects from the grid if a grid fault is detected (anti-islanding protection).
Monitoring & Communication: Usually has a built-in data logger, recording generation, status, etc., and transmits data via wired (RS485, Ethernet) or wireless (WiFi, 4G) means to a monitoring platform.
Protection Functions: Provides multiple protections: over/under voltage, over/under frequency, overcurrent, overtemperature, reverse polarity, insulation faults, etc.
Role: The "heart" of the system, the core power conversion unit.
Input: Receives DC electricity from the DC Combiner Box (or directly from strings).
Output: Produces AC electricity.
Accessories - AC Cables:
Role: Transmits the AC output from the inverter to the AC Distribution Board (ACDB) or directly to the point of interconnection (POI) with the grid / local loads.
Requirements: Standard AC power cables compliant with local electrical codes (e.g., THHN/THWN, XHHW in conduit, or USE-2/RHW-2 for direct burial).
AC Distribution Board (ACDB) / Load Center:
Protection & Distribution: Contains circuit breakers providing protection (overload and short-circuit) for the inverter AC output.
Metering: Houses an electricity meter (kWh meter) to measure the PV system's energy production (energy fed into the grid or self-consumed).
Grid Interconnection Point: The final connection point between the system and the grid or the user's main electrical panel. The utility meter is typically installed here or nearby.
Surge Protection: AC side SPDs.
Isolation: Provides an isolation switch for maintenance.
Role:
Grid / Loads:
Grid-Tied System: The converted AC electricity is fed into the grid for use by others. System power is first used by local loads; excess is exported to the grid; shortfall is imported from the grid.
Off-Grid System: AC power is supplied directly to local loads (often requiring battery storage).
Role:
Structural Support: This is the primary function. It securely fixes the PV panels to the roof, ground, or other structure, supporting wind, snow, rain, and dead loads, ensuring the panels operate long-term at the optimal angle and position.
Angle Optimization: Mounts can be fixed-tilt or use tracking systems to maximize the solar irradiance received by the panels, directly impacting energy yield (the electrical system's final output).
Ventilation & Cooling: Proper mounting design (e.g., elevated installation) provides airflow behind the panels, aiding cooling. Higher temperatures reduce PV panel efficiency.
Grounding Path: The metal mounting structure is a vital part of the entire PV array grounding system. It provides a low-impedance path to earth ground for panel frames, rails, and other metal components, safely conducting potential fault currents or lightning currents to earth, protecting equipment and personnel. Grounding conductors connect to the mounting rails and array frame.
Light Energy -> DC Electricity: Sunlight hits the PV panels, generating DC electricity.
Intra-Panel Collection & Protection: Current is collected and output via the junction box; the bypass diode provides protection if needed.
String Formation: PV cables and connectors connect multiple panels in series, forming a "string" with higher output voltage.
String Combining & Protection: DC outputs from multiple strings are connected via string cables to the DC Combiner Box. The combiner box connects strings in parallel, increasing output current, and provides protection via internal fuses/breakers and SPDs.
DC Transmission: The combined DC power is transmitted via main DC cables to the inverter.
DC -> AC Conversion & Optimization: The inverter converts DC to AC and maximizes input power via MPPT.
AC Output & Protection: The inverter's AC output is transmitted via AC cables to the AC Distribution Board (ACDB).
Metering & Grid Connection: In the ACDB, after protection by AC breakers, energy is measured by the meter, and finally interconnected with the grid at the Point of Interconnection (POI) or supplied to local loads.
Energy Consumption/Export: AC electricity is consumed by loads or exported to the grid.
The mounting structure provides physical support, angle optimization, cooling environment, and grounding foundation for the PV panels, junction boxes, connectors, and cables (within the array) involved in steps 1-4. It is the infrastructure ensuring the electrical process operates safely, stably, and efficiently.
Accessories Summary: Junction boxes, connectors, cables (DC + AC), combiner boxes, breakers/meters in the ACDB, etc., are all indispensable "parts" that form the complete electrical pathway, enable energy transmission, and provide safety protection.
Understanding this flow and the role of each component clearly shows how solar energy is step-by-step transformed into usable electricity.
