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可再生能源转让Renewable Energy assignment

论文价格: 免费 时间:2019-09-02 10:45:07 来源:www.ukassignment.org 作者:留学作业网
a) A solar thermal system.太阳能热系统。
 
太阳能技术一般包括光热和光电应用。太阳能光伏技术利用太阳能电池的光电效应将太阳辐射直接转化为电能并以电的形式加以利用,而光热技术则利用各种形式的集热技术将太阳辐射收集和储存为热能。太阳能热技术直接利用的太阳辐射的能量形式是热能,可用于太阳能热技术、蓄热技术的技术实施和工程应用中的供热、制冷、空调、热电等。技术学不仅是太阳能热利用的必要组成部分,而且是一种独立存在和发展的特殊技术,在工程技术领域占有重要地位,应用广泛。太阳能蓄热器的节能应用得到了广泛的采用和发展,是一种高效、环保的节能技术措施。太阳能蓄热技术潜力巨大,许多工程技术作为节能环保措施逐步开发利用。
Solar energy technology generally includes photothermal and photoelectric applications. Solar photovoltaic technology uses the photoelectric effect of solar cells to directly convert solar radiation into electricity and apply it in the form of electricity, while photothermal technology uses various forms of collector technology to collect and store solar radiation as heat energy. The energy form of solar radiation directly applied by solar thermal technology is thermal energy, which can be used for heating, cooling, air conditioning and thermal power generation, etc. In the technical implementation and engineering application of solar thermal technology, thermal storage technology is not only a necessary part of the utilization of solar thermal, but also a kind of independent existence and development of special technology, which occupies an important position and is applied in a wide range of engineering technology fields. The energy saving application of solar thermal storage is widely adopted and developed, which is a kind of efficient and environment-friendly energy-saving technology measure. Solar thermal storage technology has great potential, and many engineering technologies are gradually developed and utilized as energy saving and environmental protection measures.
所谓太阳能蓄热技术,是指储存太阳能热的储能技术,该储能技术是指在太阳辐射弱时或者在夜间无太阳辐射的情况下,由一定的技术装置转换、收集,并能以非随时可用的形式使用。离子,或经过长时间的转换,如通过季节性转换,可重复使用。蓄热技术的蓄热,其使用时间相对于转换收集时间,可延迟保存,长期待机。太阳能蓄热技术可以克服太阳能利用中太阳辐射间歇性和区域性差异等应用局限性,提高太阳能技术利用的可能性和应用效率,实现多种工程应用。技术可以更节能环保。太阳能蓄热技术可广泛应用于建筑节能、绿色建筑、热泵、制冷、空调等领域,大大提高了这些领域工程设备系统的节能环保效果。
The so-called solar thermal storage technology refers to the energy storage technology that stores the solar heat that has been converted and collected by certain technical devices, and can be used in the form of non-ready-to-use, at the time of weak solar radiation or at night without solar radiation, or after a long period of time, such as through seasonal conversion, and can be re-used. The heat storage of thermal storage technology, its use time relative to conversion collection time, can delay preservation, long-term standby. Solar thermal storage technology can overcome the application limitations such as solar radiation intermittency and regional differences in solar energy utilization, improve the possibility and application efficiency of solar energy technology utilization, and the implementation of many engineering technologies can be more energy saving and environmental protection. Solar thermal storage technology can be applied in a wide range of fields such as building energy saving and green building, heat pump, refrigeration and air conditioning, which greatly improves the energy-saving and environmental protection effect of engineering equipment system in these fields.
 
Solar thermal systems are usually hot water and hot air systems. The difference of two systems: the collector heating medium is different, hot water system set up hot water collector, use of solar heat to heat water for users to use hot water, air air collector system setting, collect solar thermal heating air, two types of systems can get hot water and hot air, can be directly or indirectly to hot water heating, heating, drying, life form and so on a wide range of applications. Solar thermal storage technology can be applied in a wide range of user areas of solar thermal hot water and air systems to save energy and protect the environment, improve system efficiency and enhance system functions. For example, in the solar hot water system, the simplest solar hot water latent heat storage is to set the PCM material at the bottom of the hot water tank. When there is solar heat irradiation, the water heats up and the PCM material absorbs heat and stores heat. When there is no solar radiation, the PCM material flows into the water tank and heats up with cold water, thus achieving energy saving of heat storage and release. Various measures are adopted to improve the heat transfer efficiency of the heat storage tank. Various forms of open and closed loop complex systems are continuously developed and applied. The independent thermal memory of PCM material is used to store heat and release heat. For solar thermal air systems, both sensible heat and latent heat storage can be used in solar thermal systems. The heat storage capacity of PCM material can be reduced by using the sensible heat storage mode of rock, water and other heat storage materials. The corresponding drying device is set and the solar air heat collecting system with phase-change latent heat storage is adopted. The solar heat can be used to dry tobacco, vanilla and crops without sun exposure. The solar air heat collecting principle of phase-change latent heat storage can be used in the design of solar house technology measures for building energy saving. For example, the application of finalized phase-change thermal storage materials in the ceilings and walls can directly benefit air heat collection and regulate indoor temperature environment with solar heat storage and release, which can reduce building energy consumption.
 
Solar thermal storage for building energy conservation is an important technical measure for building energy conservation at present. For example, the application of phase-change thermal storage technology will generate huge energy saving effect and great potential for application. Phase-change thermal storage materials can be widely used in building energy conservation. The principle is to improve the heat storage and release of building envelope to solar heat, geothermal and other renewable energy sources, increase the solar heat available for utilization, so as to reduce the load of building heating and air conditioning and achieve building energy conservation. For example, tromb wall is an effective solar energy building technology that absorbs and stores solar heat for building energy conservation. By setting up thermal interlayer of building envelope to collect and circulate solar heat for heating heat collection and distribution. The use of phase-change thermal storage materials in the wall materials of trombe wall can enhance the heat storage and release capacity of the wall, so as to absorb and utilize more solar heat, realize the reduction of heating heating and cooling and heating load of air conditioning, and improve the building energy efficiency. Phase-change thermal storage materials can be applied to wall and window structures. For example, a shutter that is opened at night during the day, a phase-change thermal storage material absorbs solar heat, and the shutter is closed at night, which is insulated from external heat, and the heat is one-way to indoor heating. The shaped phase-change thermal storage materials can be applied to the heating function floor for the use of electric load regulation or solar heat storage to reduce building energy consumption and operation cost. The ceiling structure on the top of the building USES phase-change thermal storage materials to store and release solar heat, which can reduce the heating load of the building.
 
 
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.#p#分页标题#e#
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.
 
After the host specification is selected, the capacity of energy storage battery is matched. The capacity matching principle is: "in the case of ensuring normal power supply to the electrical appliances, as economical as possible". The second is to ensure that in a certain continuous no wind day to use the electrical normal power supply. The number of consecutive days without wind (n) is determined according to local wind conditions (usually 5 to 7 days). If only starting from the requirements of ensuring the normal power supply to the electrical appliances, according to the principle of "daily charging and daily consumption", the storage capacity of the battery can be as long as it can store the daily effective power generation of the generator. As a matter of fact, the storage capacity of the battery should be guaranteed to provide normal power to the electrical appliances in continuous no wind days. As a result, the battery capacity should be able to store up to n times the effective daily output of the generator. This capacity is the maximum capacity of the matched battery, expressed as Qmax. In practical application, the daily electricity consumption of electric appliances is less than the daily effective power generation of generators. Therefore, for economic consideration, the storage capacity of the battery should be determined according to the actual power consumption of the electric appliance, that is, the daily power consumption of the electric appliance is n times. This capacity is the economic value of the capacity of the matched battery, expressed as Q. When matching the storage capacity of the battery, choose Q close to (or slightly above) the economic value within the standard series value, but not exceeding the maximum Qmax.
 
Correct battery charge and discharge. In the battery charge, discharge, the concept of quantity, charge and discharge should be appropriate, to eliminate discharge (electricity) uncontrolled, unlimited charging phenomenon. When the battery is full, stop it in time to reduce unnecessary wear of the main engine; In case of high wind, the machine should be stopped in time (20m/s is usually defined as the wind speed of stop) to avoid damage to the main engine. To add or replace electrical appliances, check their electrical suppression to avoid voltage mismatch and damage electrical appliances.
 
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