中国三大国粹,强心脏101026中字,好笑的动态图片
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b) A solar photovoltaic system
The reality is that radiant energy is changing, and solar cells are energy conversion components with no storage function, so their output is changing all the time. The calculation of photovoltaic power generation capacity is based on the conversion efficiency of different types of panels (17% for monocrystalline silicon, 15% for polycrystalline silicon and 8% for thin film cells), which can only give an average value. Where defined: AM -- atmospheric mass, or volume ratio, pressure ratio, or distance ratio under the same horizontal section. The length of the path of direct sunlight through earth's atmosphere is expressed as a multiple of the length of the path of the sun through the atmosphere to sea level at the zenith.
1) off-grid system
(1) off-grid system without battery, the selection of solar cell module should consider the start-up and overload performance of electrical equipment, and the output current of the solar module must ensure the need of starting current. Since the solar modules have limited overload capacity and the short circuit current is usually no more than 1.2 times the rated current, the panel's capacity needs to be large.
(2) off-grid system with battery, the solar cell component can only be considered under normal working condition to meet the power and service time requirements of the electrical equipment. That is, the power generation capacity of solar panels should be able to meet the requirement of energy consumption of electrical equipment throughout the day. The battery should not only consider the discharge current to meet the starting requirements of the electrical equipment, but also the capacity of the battery should meet the requirement of all-day sunless time to ensure the power consumption of the electrical equipment. Basic principle: the capacity of solar modules should be enough to collect enough energy for the whole day when there is sunlight during the day. The sun appears in a cycle of 24 hours, so we can calculate the solar module capacity in a day. During the effective time of solar irradiation, the power of the equipment shall be ensured, and the battery shall be charged to the rated capacity within the effective time. The energy of the battery should be used for the rest of the time. The capacity of the solar cell module is selected according to the standard test condition and the average daily sunshine time is 5h. For example, the power equipment is 10kW, the power consumption is 240kWh, and the solar cell capacity is 240/5=48kW. The storage capacity of the battery shall meet the requirement of 190kWh of electrical equipment within 24-5=19h without lighting time. If the battery terminal voltage is 220V, the battery capacity is about 900Ah. The above is the result calculated under ideal conditions with a period of 1 day. If you consider the maintenance factor, cloudy conditions of rain, but also consider the appropriate margin.
2) grid-connected system
(1) grid-connected battery free system, the solar energy module can only consider the sunlight in the daytime, and meet the power and use time requirements of the electrical equipment. The equipment's starting current and other electricity without sunlight can be supplied by the power network. (2) grid-connected system with battery, the solar panel can only consider the sunlight condition in the daytime to meet the power and use time requirements of the electrical equipment. The storage capacity of the battery can only be considered for emergency power consumption within a specified period of time, and electricity consumption at other times can be provided by the power network.
3) grid-connection: according to whether the photovoltaic system is allowed to send power to the high-voltage power grid through the transformer in the power supply area, grid-connection mode can be divided into reverse-flow mode and non-reverse-flow mode. The grid-connection shall guarantee the power quality, including voltage deviation, frequency, harmonic and waveform distortion, power factor, voltage unbalance, dc component, etc. Grid connection shall be provided with safety protection, including: over/under voltage, over/under frequency, anti-island effect, restoration of grid connection, lightning protection and grounding, short circuit protection, isolation and switching, reverse power protection.
4) safety and protection
Under standard test conditions, the short circuit current of a solar cell is usually only about 1.2 times its maximum rated current, so the diode can be connected in the first-level junction box to prevent reverse flow. Short circuit and overload protection shall be provided for each circuit of the indoor junction cabinet. The main purpose is to prevent the current of other circuits from passing through the fault point of short circuit and causing fault of other circuits. Pv system grid-connection should be protected as follows:
4.1 over/under voltage
When the voltage at the junction of the grid exceeds the allowable deviation of the three-phase voltage, the allowable deviation of the single-phase voltage is the range of +7% and -10% of the rated voltage, the photovoltaic system should stop sending power to the grid. This requirement applies to any phase in a multiphase system.
4.2 over/under frequency
When the power grid connection frequency exceeds the rated frequency, + / - under-frequency protection should operate within 0.2s to disconnect the photovoltaic system from the power grid.
4.3 anti-island effect
When the pv system is absorbed into the grid, the pv system must be disconnected from the grid within the specified time limit to prevent island effect. At least one active and passive island effect protection should be provided. Active island effect protection mainly includes frequency shift, active power variation, reactive power variation and impedance variation caused by current pulse injection. Passive island effect protection mainly includes voltage phase jitter, three-time harmonic variation and frequency variation. When the grid loses voltage, the island effect protection should be operated within 2s to disconnect the pv system from the grid.
4.4 restore grid-connection
Pv system FIG. 2 solar panel distribution system FIG. 2 after the power supply to the grid is stopped, pv system shall not send power to the grid within 20 ~ 5min after the voltage and frequency of the grid are restored to the normal range.
c) A wind energy system.
With the development of new energy industry, the small horizontal shaft wind turbine which is used as a household is accepted by more and more people. However, the biggest disadvantage of this kind of wind turbine is its large size and inconvenient installation. Because there is no large wind field in the residential area, and the starting wind speed required by horizontal axis wind turbine is high, it is difficult to start power generation at ordinary times. In addition, in order to ensure that the blade of the wind turbine is always at the position of the maximum receiving wind surface, the windward device should be added, which increases the difficulty of design as a simple type of wind turbine. The vertical axis wind turbine mainly has the lifting type which is the derrish type and the resistance type which is the savonius type, can overcome these shortcomings of the horizontal axis. Among them, the darrish type has small starting torque and poor starting performance, and it often needs other power to start at a specific speed to operate normally. The technology and equipment are complex, and it is not suitable to be used as a simple wind turbine. On the contrary, it is considered that the utilization coefficient of wind energy is lower than horizontal axis wind turbine and other high-speed vertical axis wind turbines, which is not competitive in large-scale commercial power generation. However, the small Savonius fan is easy to make, can operate normally in all kinds of wind speeds, the motor can be installed on the building surface, and the maintenance is simple and easy, which is more suitable for the small household wind turbine. Fan when wind speed is low but still can't generate enough electricity. Blade adopts the material performance of wind power generation device has great effect on the performance and efficiency. High strength light quality of carbon fiber reinforced plastics, although the price is higher but used in the small fan is the most appropriate, because it according to the mechanical characteristics of wind turbine blade design strength and stiffness and easy to processing molding. Calculation shows that using this material, as long as 2 ~ 2. The thickness of 5 mm blade can meet the design requirements of strength, because the quality is small, very beneficial to the start of the wind turbine in the breeze.
Micro wind power generation system is powered by natural wind. At work, the wind wheel rotates under the action of natural wind and drives the generator to run and generate electricity. The three-phase alternating current generated by the generator is rectified through the rectifier device to charge the battery. Electrical appliances are powered by batteries, and there are two common ways to use electricity. One is that the battery supplies the electrical appliances directly to the dc 12V or 24V. The other is to inverter the battery output direct current to alternating current. |
