The core task of a
solar power plant is to convert the inexhaustible energy of solar radiation into usable electricity. This process may seem simple, but it actually involves sophisticated photoelectric effects and power conversion technologies. The following is a detailed analysis of its main operating principles:
1. Core Link: Photoelectric Effect Drives Energy Conversion (Photovoltaic Effect)
Core Support: Solar Panels
They consist of a large number of photovoltaic cells (primarily made of silicon) connected in series or parallel.
Physical Process:
Photon Absorption: Solar energy penetrates the panel glass and strikes the silicon semiconductor layer.
Electron Stimulation: The energy of photons is absorbed by electrons within silicon atoms. If the energy is high enough (above the silicon "gap"), the electrons break free from their atoms and become free electrons.
Electric Field Drive: The PN junction (the interface between P-type and N-type silicon) within the cell generates a built-in electric field (direction: N- > P).
Electrons are generated by the directional movement of free electrons under the influence of the electric field (electrons toward the N region, holes toward the P region), thus generating direct current (DC). Key Points: A single solar cell only generates approximately 0.5 volts. By connecting cells in series to increase voltage and in parallel to increase current, they are combined to create a solar panel that meets demand.
II. DC System Integration: Energy Integration and Regulation:
Solar Array: Hundreds of solar panels are assembled according to electrical design to form a large power generation matrix.
Combiner Box:
Collects the DC output of multiple solar panels in parallel.
Integrates DC circuit breakers and lightning protection devices to ensure system safety.
DC Distribution Cabinet: Further combines the total array output and distributes it to the inverter.
III. Inverter Conversion: DC to AC Bridge
Core Equipment: Grid-Connected Inverter
Function: Converts the collected unstable DC power into AC power with the same frequency, phase, and amplitude as the grid.
Technical Process:
DC/DC Conversion: First, the fluctuating DC voltage is adjusted to a stable DC voltage suitable for the inverter. MPPT technology is also used to optimize power point tracking.
DC/AC Inverter: Utilizes power semiconductor devices (such as IGBTs) for high-speed switching, changing the current direction according to the law of the sine wave, thereby generating AC power. Filtering and Synchronization: Removes high-frequency harmonics to ensure a pure output waveform and precisely locks to the grid's frequency and phase for seamless synchronization.
IV. Grid Connection and Transmission: Connecting to the Public Power Grid
AC Distribution Cabinet: Distributes the AC power output from the inverter to the step-up transformer.
Step-up Transformer: Boosts the low-voltage AC power output from the inverter (e.g., 270V or 315V) to medium or high voltage (e.g., 10kV or 35kV), effectively reducing losses during long-distance transmission.
High-voltage Switchyard: Includes circuit breakers, disconnectors, and protective devices, controlling the connection and disconnection between the power station and the grid to ensure safety.
Grid Connection: The boosted power is transmitted to the public grid via overhead lines or cables for user use.
V. Core Support Systems: Intelligent Operation Assurance
Supervisory Control and Data Acquisition (SCADA) System:
Collects real-time information on power generation, voltage, current, equipment status, and radiation.
Providing remote monitoring, fault alarms, and performance analysis, it is the "brain" of the power station. Tracking System (Optional):
Single-axis/dual-axis trackers drive solar panels to follow the sun's movement, significantly increasing power generation (approximately 15%-30%).
Mounting System:
Secures solar panels, ensuring optimal tilt and orientation (typically south in the Northern Hemisphere), and withstands wind and snow loads.
VI. Factors Affecting Efficiency
The actual output power of a solar power plant is limited by several factors:
Solar irradiance: This is the core energy source, strongest on sunny days.
Spectral composition: Different wavelengths have different light conversion efficiencies.
Panel temperature: As temperature rises, efficiency decreases significantly (approximately -0.3% to 0.5%/°C).
Shading: Partial shadows (from leaves, bird droppings, and clouds) cause a "bucket effect," severely impacting overall string output.
Dust and dirt: Dust on the panels blocks light transmission.
Losses: This includes line losses, inverter conversion losses (typically >98% efficiency), and transformer losses.
Orientation and tilt: These affect sunlight reception efficiency.
Summary: A Panoramic View of Energy Flow
Sunlight shines → Photovoltaic cells generate DC power → Combiner box/distribution cabinet integration → Inverter converts to AC power → Transformer boosts voltage → Connection to the grid → Transmission reaches every household
Through advanced technologies, solar power plants transform free solar photons into the clean electricity that powers modern society. Understanding their operating principles is fundamental to optimizing plant design, improving operational efficiency, and promoting the development of photovoltaic technology.
