Solar photovoltaic power system refers to a power system that directly converts light energy into electricity without thermal process. Its main components are solar cells, batteries, controllers and photovoltaic inverters. It is characterized by high reliability, long service life, no environmental pollution, independent power generation and grid operation.
The photovoltaic power system is usually composed of a photovoltaic array, battery pack, battery controller, inverter, AC power distribution cabinet and solar tracking control system and other equipment. High concentrated photovoltaic system (HCPV) also includes the concentrating part (usually concentrating lens or mirror).
1. Photovoltaic Array
Photovoltaic Array (PV Array) is a DC power generation unit composed of several photovoltaic modules or photovoltaic panels assembled together in a certain way and with the same supporting structure.
In the presence of light (whether sunlight or light from other luminescent objects), the solar cells absorb light energy, and a buildup of abnormal charges at both ends of the cell creates a "photogenic voltage". This is called the photogenic volt effect. Under the action of photogenerating volt effect, the two ends of the solar cells produce electromotive force, which converts light energy into electrical energy and completes energy conversion.
2. Battery pack
The function of the battery bank is to store the electrical energy emitted by the solar cell array when it is illuminated and can supply power to the load at any time. The basic requirements of the battery pack used for solar cell power generation are as follows.
(1) Low self-discharge rate.
(2) Long service life.
(3) Strong deep discharge capacity
(4) High charging efficiency.
(5) Less maintenance or maintenance-free of solar cells.
(6) Wide operating temperature range
(7) Low price.
3. Battery controller
The battery controller is a device that can automatically prevent the battery from overcharging and overdischarging. Because the cycle charge and discharge times and discharge depth of the battery are important factors to determine the service life of the battery, the battery controller that can control the overcharge or overdischarge of the battery is essential equipment.
4. Photovoltaic inverter
An inverter is a device that converts direct current into alternating current. When solar cells and batteries are DC power sources and loads are AC loads, inverters are essential.
According to the operation mode, the inverter can be divided into off-grid inverter and grid-connected inverter. Off-grid inverters are used in independently operating solar cell power systems to supply power to loads. Grid-connected inverters are used in types of grid connected pv system.
The inverter can be divided into square-wave inverter and sine-wave inverter according to the output waveform. Square-wave inverter has simple circuit and low cost, but large harmonic component. It is generally used in systems with several hundred watts or less and low harmonic requirements. Sine-wave inverters are expensive but can be used for various loads.
5. Tracking system
For a solar photovoltaic power system at the same location, the angle of the sun's light changes all the time throughout the year, and the sun rises and sets every day. The solar panel can be directly facing the sun at all times only and the power generation efficiency can reach the optimal state.