Solar power generation is a device that uses a battery pack to convert solar energy directly into electrical energy. The solar cell module is a solid device that utilizes the electronic properties of the semiconductor material to realize the PV conversion. In a large area without a power network, the device can be conveniently provided for user lighting and living, and some developed countries can also complement the regional grid and implement the grid. . At present, from a civilian point of view, research in foreign technologies tends to be mature and has begun to industrialize. It is the “photovoltaic-architecture (lighting) integration” technology, and domestic research and production are mainly applied to the small-scale solar power generation for household lighting in areas without electricity. system.
First, the principle of solar power
The solar power generation system mainly includes: solar battery components (arrays), controllers, batteries, inverters, and users, ie, lighting loads. Among them, the solar battery module and the battery are the power supply system, the controller and the inverter are the control protection systems, and the load is the system terminal.
1, solar power system
The solar battery and the battery constitute the power supply unit of the system, so the battery performance directly affects the system operating characteristics.
(1) Battery unit:
Due to technical and material reasons, the amount of electricity generated by a single battery is very limited. In practice, a solar battery is a battery system in which a single battery is composed of strings and parallels, and is called a battery module (array). The single cell is a silicon crystal diode. According to the electronic characteristics of the semiconductor material, when the sun shines on the pn junction made of p-type and n-type homogenous semiconductor materials of different conductivity types, under certain conditions Solar radiation is absorbed by the semiconductor material, resulting in non-equilibrium carriers, electrons and holes, in the conduction band and valence band. Similar to the P-N junction barrier region, there is a strong built-in electrostatic field, so that the current density J, the short-circuit current Isc, and the open-circuit voltage Uoc can be formed under illumination. If the electrodes are drawn on both sides of the built-in electric field and connected to the load, theoretically, the circuit formed by the PN junction, the connecting circuit, and the load will have a "photocurrent" flowing therethrough, and the solar cell module will realize a power P to the load. Output.
Theoretical research shows that the peak power Pk of a solar cell module is determined by the local average solar radiation intensity and the end-use electrical load (electricity demand).
(2) Electrical energy storage unit:
The direct current generated by solar cells enters the battery first, and the characteristics of the battery affect the efficiency and characteristics of the system. Battery technology is very mature, but its capacity is affected by the amount of power required at the end of the day and the duration of the sun (power generation time). Therefore, the battery watt-hour capacity and ampere-hour capacity are determined by the predetermined continuous no-sunlight time.
The main function of the controller is to make the solar power system always in the vicinity of the maximum power point of power generation in order to obtain the highest efficiency. The charge control usually adopts pulse width modulation technology, ie, PWM control mode, so that the entire system always runs in the area near the maximum power point Pm. Discharge control mainly refers to the lack of electricity in the battery, system failure, such as the battery open or reversed switch off.
3, DC-AC inverter
The inverter can be divided into self-excited oscillation inverter and he-excited oscillation inverter according to the excitation method. The main function is to reverse the direct current of the battery into alternating current. Through a full-bridge circuit, SPWM processors are generally used to modulate, filter, boost, etc., to obtain sinusoidal alternating-current power supply system end users that match the lighting load frequency f and rated voltage UN.
Second, the efficiency of solar power systems
In a solar power system, the total system efficiency ηesee consists of the PV module conversion rate, controller efficiency, battery efficiency, inverter efficiency, and load efficiency. However, compared with solar cell technology, it is much more mature than the technologies and production levels of other units such as controllers, inverters, and lighting loads, and the current system conversion rate is only about 17%. Therefore, improving the conversion rate of battery modules and reducing the unit power cost is the key and difficult point in the industrialization of solar power generation. Since the advent of solar cells, crystalline silicon has maintained its dominance as the leading material. The current research on the conversion rate of silicon cells mainly revolves around enlarging the energy-absorbing surface, such as double-sided batteries, and reducing reflections; using gettering technology to reduce the compounding of semiconductor materials; ultrathin battery; improving theory and establishing a new model; Spotlight batteries.
Third, making full use of solar energy is one of the important contents of green lighting
The true sense of green lighting includes at least: the lighting system's high efficiency, high stability, and energy-efficient green light sources.
1. Power Generation - Building Lighting Integration
Currently successfully integrating solar modules and building components, such as solar roofs (tops), walls, doors, windows, etc., to achieve "PV-Building Lighting Integration (BIPV)"
2, green light source research
The optimal design of the green lighting system requires high light output with low energy consumption and extended lamp life. Therefore, DC-AC inverter design should obtain reasonable filament warm-up time and excitation lamp voltage and current waveforms. There are four typical types of solar energy light source excitation methods currently in research and development:
1 self-excited push-pull oscillation circuit, through the filament series starter warm-up start. The main parameters of the light source system are: input voltage DC = 12V, output light efficiency> 495Lm / support, lamp rated efficiency 9W, effective life 3200h, continuous opening times> 1000 times.
2 Self-excited push-pull oscillation (simple type) circuit, the main parameters of the light source system are: input voltage DC=12V, lamp power 9W, output light efficiency 315Lm/support, continuous start times >1500 times.
3 self-excited single-tube oscillation circuit, filament series relay warm-up start mode.
4 Efficient and energy-saving green light sources such as self-excited single-tube oscillation (simple type) circuits.
Fourth, the conclusion
The issue of green energy and sustainable development is a major issue that is now facing. The development of new energy sources and the full and reasonable use of existing energy resources have received great attention from governments of all countries. As an inexhaustible source of solar energy, the inexhaustible clean and environmentally friendly energy source will have unprecedented development. With the deepening of solar energy industrialization process and technology development, its efficiency and cost performance will be improved. It will be widely used in various fields including photovoltaic building integration, and will also greatly promote China's green lighting project. "The rapid development.
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