Solar power system structure and working principle
Solar power is the use of solar energy battery components directly into electrical energy. Solar Module (Solar cells) is the use of electronic characteristic of semiconductor materials to achieve solid PV conversion device, in the vast off-grid areas, the device can be easily implemented as user-powered lighting and living, and some developed countries also regional power grid to achieve complementarity. Current from the civilian point of view, mature technology in foreign countries, and begun to take industry is "PV - Building (lighting) integration" technology, while the domestic production of major research areas without electricity for a small solar home lighting power generation systems.
1 Principles of solar power
Solar power generation system include: solar module (array), controller, batteries, inverters, lighting load that is composed of the user. Among them, the solar battery components and batteries for the power system, controller and inverter for the control and protection system, the load for the system terminals.
1.1 Solar power system
Solar cell and battery components of the system power supply unit, so a direct impact on battery performance characteristics of the system work.
(1) Battery Unit:
As technology and material reasons, a single cell generating capacity is very limited, practical solar cells in a single cell by series and parallel to form a battery system, called the battery components (arrays). Single cell is a silicon diode, according to the electronic characteristic of semiconductor materials, when the sun light shines from the P-type and N-type conductivity of two different types of homogenous composition of semiconductor materials when the PN junction, under certain conditions , solar radiation absorbed by the semiconductor material in the conduction band and valence band of non-equilibrium carrier generation is electron and hole. Barrier at the PN junction with the existence of strong built-in area electrostatic field, which can be formed in the light of the current density J, short-circuit current Isc, open circuit voltage Uoc. If the sides of the built-in electric field leads to the electrode and connected to the load, by the PN junction theory, the connection circuit and the load form the loop, there is "photo-current" flows through the solar modules to achieve the power of the load P output.
Theoretical studies have shown that the peak power of solar modules Pk, by the local solar radiation intensity and the end of the average electricity load (electricity demand) decisions.
(2) electrical energy storage unit:
Solar cells produce direct current into the battery before storage, the battery characteristics of the system's efficiency and features. Battery technology is very mature, but its capacity to take power by the end of the sunshine time (generation time) effects. Watt-hour battery capacity and therefore the amount of the intended consecutive An Shirong no sunshine decision.
Controller's main function is to make solar power system is always in the vicinity of the maximum power generation in order to obtain maximum efficiency. The charge control usually the PWM pulse width modulation control, so that the whole system is always running at maximum power point Pm near the area. Discharge control mainly refers to when the battery power shortage, system failures, such as open or reversed when the battery cut off switch. Currently both Hitachi developed a tracking control point Pm, and can track the sun moving parameter of the "sunflower" type of controller, the battery components will be fixed about 50% efficiency.
1.3 DC-AC inverter
Inverter by incentives can be divided into self-excited oscillation inverter and his excited oscillation inverter. Main function is to the DC battery
The inverse into alternating current. Through the full bridge circuit, generally modulated SPWM processor, filter, boost, etc., are with the photos
Ming load frequency f, the rated voltage matches the sinusoidal alternating current UN and other end users for the system.
2 the efficiency of solar power generation system
In the solar power system, the system's total efficiency of the battery components ηese PV conversion rate, controller efficiency, battery efficiency, inverter efficiency and the efficiency of load composition. But compared to the solar cell technology is concerned, than the controller, inverter, and the lighting load, and other units of the technology and production level is much more mature, and the current system, the conversion rate is only about 17%. Thereby increasing the conversion rate of battery components, reducing unit power cost solar power industry is the key and difficult. Since the advent of solar cells, crystalline silicon material as a protagonist to maintain dominance. Current conversion rate of silicon cells, mainly around the greater energy-absorbing surface, such as two-sided cells, reducing the reflection; gettering technology reduces the use of compound semiconductor materials; ultra-thin battery technology; improved theory, the new model; poly light batteries. Several conversion efficiency of solar cells in Table 1.
Table 1 Several conversion efficiency of solar cells
A typical thin film batteries battery products laboratory
Various solar cell ηmax (%) of various solar cell η (%)
16.6 24.4 polycrystalline silicon
Polycrystalline copper indium gallium selenide 18.8 18.6
GaAs (single knot) 25.7 16.0 cadmium telluride
a-si (single node) 13 14.1 copper indium selenide
Full use of solar energy is an important part of the green lighting. The true sense of the green lighting at least include: high efficiency lighting systems, high stability, energy efficient green light and so on.
3.1 generation - Integration of Architectural Lighting
Now succeeded in solar modules and building components to be integrated, such as solar roof (top), walls, windows and doors, etc., to achieve a "PV - architectural lighting integrated (BIPV)". June 1997, the United States named after the President announced the "Million Solar Roofs Plan", in 2010 the implementation of the one million residential solar power systems. Japanese "Sunshine" in 2000 before the building components will be installed PV costs to 170 ~ 210 yen / W, the annual output of solar cells, 10MW, the battery cost down to 25 to 30 yen / W. May 14, 1999, Germany, built in just one year two months, the world's first zero-emission solar module factory, complete with renewable energy to provide electricity, the production does not emit CO2. Plant south wall for about 10m high glass curtain wall PV array, including the roof PV components, the entire factory building with 575m2 of solar cell modules, only this can provide more than one third of the building's electricity, and its wall PV component surface and roof shape, color, architectural style and building integrated with the surrounding natural environment to achieve the integration of a very perfect coordination. The building and about 45kW capacity, from the natural state of rapeseed oil as fuel to provide heat and power plant, the design of combustion of rapeseed oil and rapeseed CO2 generated when the CO2 needed for growth, the basic balance, which is a truly zero-emission plant. BIPV also focus on the art of decoration, in the Czech Republic and the Czech Republic by the German co-WIP company, built the world's first PV curtain wall surface color. West Bengal, India for the island of 117 villagers without electricity installed 12.5kW of BIPV. China Changzhou Trina aluminum curtain wall Manufacturing Co., Ltd. successfully developed a "solar house", the power generation, energy saving, environmental protection, value and into a room, succeeded in photovoltaic technology and construction techniques combine the building known as the solar system (SPBS ), SPBS was September 20, 2000 by experts. Recently built in Pudong, Shanghai country's first solar energy - the integration of public toilets, lighting, all the electricity provided by the rooftop solar cells. This will greatly promote the construction of solar energy industry and the market process.
Green light source of 3.2
Optimization of green lighting systems require low power consumption obtained high light output, and extend lamp life. Therefore, DC-AC inverter design, should be given a reasonable warm-up time and incentive filament lamp voltage and current waveforms. Currently in research and development of solar lighting in four typical circuit incentives: ① self-excited push-pull oscillator circuit, through the filament preheating starter series started. The main parameters of the light source system are: input voltage DC = 12V, the output light efficiency> 495Lm / sticks, lamp rated efficiency 9W, the effective life of 3200h, the number of consecutive open> 1000 times. ② Push-pull self-excited oscillation (simple type) circuit, the source system's main parameters are: input voltage DC = 12V, lamp power 9W, output light efficiency 315Lm / branch, the number of consecutive starts> 1500 times. ③ self-excited single-tube oscillator circuit, the filament preheating relay series started way. ④ self-excited single-tube oscillation (simple type) circuits and other forms of energy-efficient green light.
Green energy and sustainable development issues facing humanity this century is a major issue, the development of new energy, full of rational use of existing energy has been great attention of Governments. Solar power as an inexhaustible supply of clean green energy will be an unprecedented development. With the solar energy industry and technology development process of the deepening of its efficiency, cost will be increased, which includes all areas, including BIPV will be widely used, it will greatly promote China's "Green Lights" fast development.