The advantages of solar photovoltaic power generation are that it is less restricted by geographical location because the sun shines on the earth everywhere; photovoltaic systems also have the advantages of being safe and reliable, noiseless, low-pollution, generating electricity locally without consuming fuel or erecting transmission lines, and having a short construction period.
I. Classification of Solar Photovoltaic Power Generation Systems
Solar photovoltaic systems are classified into off-grid photovoltaic power generation systems, grid-connected photovoltaic power generation systems, and distributed photovoltaic power generation systems:
1. Off-grid photovoltaic power generation system. It mainly consists of solar cell modules, controller, and battery. If it is to supply power to AC loads, an AC inverter is also required.
2. Grid-connected photovoltaic (PV) power generation systems convert the direct current (DC) generated by solar panels into alternating current (AC) that meets the requirements of the municipal power grid via a grid-connected inverter, and then directly connect to the public power grid. Grid-connected power generation systems include centralized large-scale grid-connected power plants, typically national-level power plants. Their main characteristic is that the generated energy is directly transmitted to the grid, which then distributes it to users. However, these power plants require large investments, have long construction periods, and occupy large areas, thus their development has not been significant. Distributed small-scale grid-connected power generation systems, especially building-integrated photovoltaic (BIPV) systems, are the mainstream of grid-connected power generation due to their advantages such as lower investment, faster construction, smaller footprint, and stronger policy support.
3. Distributed photovoltaic power generation system, also known as decentralized power generation or distributed energy supply, refers to a small photovoltaic power generation system configured at or near the user's site to meet the needs of specific users, support the economic operation of the existing power distribution network, or meet both of these requirements at the same time.
II. Composition of a Solar Photovoltaic System
1. Solar Panels: Solar panels are the core component of a solar photovoltaic system. Their function is to convert sunlight into electrical energy, outputting direct current (DC) which is then stored in batteries. Solar panels are one of the most important components of a solar photovoltaic system; their conversion efficiency and lifespan are crucial factors determining the usability of a solar cell.
2. Controller: The solar controller consists of a dedicated CPU, electronic components, a display, and switching power transistors.
3. Storage battery: The function of the storage battery is to store the electrical energy generated by the solar panel when there is sunlight, and release it when needed.
4. Inverter: The direct output of solar energy is generally 12VDC, 24VDC, or 48VDC. In order to provide power to 220VAC appliances, the DC power generated by the solar photovoltaic system needs to be converted into AC power, so a DC-AC inverter is required.
III. Working Principle of Solar Photovoltaic Systems
During the day, under sunlight, the solar cell modules generate a certain electromotive force. These modules are connected in series and parallel to form a solar cell array, ensuring the array voltage meets the system input voltage requirements. The battery is then charged via a charge/discharge controller, storing the electrical energy converted from sunlight.
At night, the battery bank provides input power to the inverter, which converts DC power into AC power and sends it to the distribution cabinet, where it switches to supply power. The discharge of the battery bank is controlled by the controller to ensure its normal operation. The photovoltaic power station system should also have overload protection and lightning protection devices to protect the system equipment from overload operation and lightning strikes, ensuring the safe use of the system equipment.
