Photovoltaic power generation is based on the photovoltaic effect, using solar cells to directly convert sunlight into electrical energy. Whether used independently or connected to the grid, a photovoltaic power generation system mainly consists of three parts: solar panels (modules), controllers, and inverters. These are primarily composed of electronic components and do not involve mechanical parts.
I. Working Principle of Solar Photovoltaic Power Generation
Solar photovoltaic power generation relies on solar cell modules and utilizes the electronic properties of semiconductor materials. When sunlight shines on a semiconductor PN junction, a strong built-in electrostatic field is generated in the PN junction barrier region. As a result, non-equilibrium electrons and holes generated in the barrier region or generated outside the barrier region but diffuse into the barrier region move in opposite directions under the influence of the built-in electrostatic field, leaving the barrier region. This causes the potential of the P region to rise and the potential of the N region to fall, thereby generating voltage and current in the external circuit and converting light energy into electrical energy.
II. Composition of a Solar Photovoltaic Power Generation System
1. Solar cell modules
A single solar cell can only generate about 0.5V, far below the voltage required for practical applications. To meet the needs of real-world applications, solar cells need to be connected into modules. A solar cell module contains a certain number of solar cells connected by wires. For example, a module may have 36 solar cells, meaning that a solar module can generate approximately 17V.
A solar cell module is a sealed physical unit formed by solar cells connected by wires. These modules offer a degree of protection against corrosion, wind, hail, and rain, and are widely used in various fields and systems. When an application requires higher voltage and current than a single module can meet, multiple modules can be assembled into a solar cell array to achieve the necessary voltage and current.
2. DC/AC Inverter
Inverters are devices that convert direct current (DC) to alternating current (AC). Since solar cells generate DC power, while typical loads are AC loads, inverters are indispensable. Inverters can be classified by their operating mode into stand-alone inverters and grid-connected inverters. Stand-alone inverters are used in stand-alone solar power systems to supply power to independent loads. Grid-connected inverters are used in grid-connected solar power systems to feed the generated electricity into the power grid. Inverters can also be classified by their output waveform into square wave inverters and sine wave inverters.
3. Power Distribution Room Design
Since the grid-connected power generation system does not have a battery, solar charge and discharge controller, or AC/DC power distribution system, if conditions permit, the inverter of the grid-connected power generation system can be placed in the low-voltage distribution room at the grid connection point. Otherwise, it is sufficient to build a separate low-voltage distribution room of 4 to 6 m2.
