Discussion on the application direction and design

2022-09-21
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Talking about the application direction and design requirements of BIPV

in the more than ten years of the 21st century, energy shortage and environmental degradation have become increasingly prominent. Developing renewable energy to replace traditional energy is the only way to solve the above problems. Solar energy has become the most attractive renewable energy in recent years because of its huge reserves, clean use, wide distribution and other advantages. Major countries in the world have taken the photovoltaic industry as one of the research priorities, and have launched their own plans. For example, California in the United States has comprehensively promoted the million roof plan, the EU renewable energy white paper plan, and Germany's solar energy subsidy plan

in China, thanks to the support of national policies, the industrial application of solar photovoltaic industry has also developed rapidly. The golden sun demonstration project and solar photovoltaic building application project led by the Energy Bureau of the national development and Reform Commission and the Ministry of housing and urban rural development, as well as the distributed power generation plan launched at the end of 2012, and the quota target of new energy development have been written into the 12th Five Year plan

China will focus on developing BIPV in the future

at present, the scale of China's solar energy industry has ranked first in the world. It should be noted that for the eastern coastal economic belt in economically active areas, after urbanization, energy shortage, building accumulation and less land are not conducive to the development of large-scale ground photovoltaic energy, which can protect sensor power stations to a certain extent, but it is very suitable for the development of BIPV. Although the scale of a single BIPV project is small, the dripping water converges into the sea, and the local supplement to the power shortage solves the problem of long-distance transmission on the loss of photovoltaic power stations

after years of development, domestic photovoltaic applications, whether industrial development orientation or actual policy effect, have gradually transitioned from large-scale ground power station applications to distributed generation mode since this year, and Building-based distributed generation has entered the golden decade development cycle

bipv power generation mode will be highly praised by the majority of customers. Its advantages of "low space cost, low power transmission and transformation cost, low comprehensive installation cost" and the following characteristics will become the key development direction of solar energy application in China

after years of industrial progress, building materials photovoltaic products have matured and can meet the current market demand

in terms of price, building material photovoltaic products (such as film modules and photovoltaic tiles for photovoltaic curtain walls) have obvious comparability and feasibility compared with other similar high-end materials, and can also meet the special requirements of building applications in terms of size, color, intensity, power safety, architectural aesthetics, etc. the light transmittance, color and structure of products can be customized according to the building requirements

bapv applications in industrial plants will be phased out due to their low integration with buildings

the roofs of a large number of industrial plants are made of colored steel structures rather than concrete structures, which makes the load-bearing and service life of the roofs very risky. As we all know, the service life of the roof of color steel structure is only 15 years at most (less than 15 years since the construction of photovoltaic projects), while the agreement signed for photovoltaic power generation is 25 years, which is completely mismatched

the roof of folk houses is a concrete structure, which can effectively avoid this problem. The application principle of roof photovoltaic in industrial enterprises is high energy consumption and spontaneous self use of surplus electricity. After entering the "12th Five Year Plan", the transformation of industrial structure in developed coastal areas determines that there will be fewer and fewer such enterprises, and high-energy consumption industrial enterprises are not the direction of development encouraged by the state. In addition, due to the restrictions of industrial roofs on the stability of owners, load-bearing requirements and other aspects, the problem of shortage of industrial roof resources has emerged, which also leads to the increasingly reduced space for large-scale promotion and application of photovoltaic on the roofs of industrial enterprises in the future

the application of residential roof can effectively avoid many key constraints in the application of industrial roof, which is more feasible from the analysis of project feasibility and business model. The power purchase agreement signed between the enterprise and the roof owner takes up to 25 years, while the property rights of the residential buildings are clear and stable, and there are no uncertain risks in the owner's operation, change, reconstruction and other aspects of the photovoltaic plant application project. Therefore, its business model has small risks and stable electricity revenue. It is a good project type to actively explore and promote the photovoltaic application demonstration in China

commercial buildings will be the key demonstration direction of provinces and cities because of their high power generation efficiency, large installed capacity, low use loss, long retention time, good demonstration effect and other advantages

because different orientations have a great impact on power generation, the roof project is the most efficient BIPV. We have many common positions of high preparation for entering China's automotive lightweight market, while commercial buildings with poor sensor contact are famous for large roofs, and most of them are idle roofs. For example, Yiwu Commodity Market and other commercial buildings have a roof area of more than 10000 square meters and an installed capacity of more than 1mwp. They are the Big Mac in the BIPV project

in addition, large and large businesses generally rely on power supply for lighting, and the business hours are mostly daytime and uninterrupted. There is no need for power storage equipment, which reduces investment, and there is no need for long-distance transmission, with small local use loss

moreover, commercial buildings are generally permanent buildings, with a design service life of 50 years. The development time is short. The duration of the actual power station can be equal to or exceed the service life of the equipment of the photovoltaic power station, and the flow of people is concentrated, which is more suitable for the promotion of new products and technologies

the government will also take certain mandatory and incentive measures to vigorously promote the demonstration of commercial buildings. The mandatory measures for developers include that large-scale commercial buildings need to meet the requirements of two or three stars for building green certification design and operation. The incentive measures for developers include that while obtaining national green construction subsidies, local governments can also support incentive funds, and in land transfer, project approval Give certain incentives in terms of taxation. Functional departments can set development goals, encourage functional departments to actively coordinate the relationship between developers and power station investment operators, and promote the development of commercial BIPV

precautions in BIPV design

the forms and specifications of battery modules need to be diversified

module forms include traditional monocrystalline silicon cells, polycrystalline silicon cells, microcrystalline thin film cells, amorphous thin film cells and soft film cells, as well as derivative products such as solar photovoltaic tiles. Crystalline silicon battery modules can be typeset in various specifications and sizes according to architectural forms, and different light transmission plates can also be made according to architectural lighting and aesthetic requirements. At present, many manufacturers of thin-film battery modules can adjust their sizes, and manufacturers can cut semi-finished products in any size, all of which are to meet the requirements of architectural design. In addition, photovoltaic tiles and soft film batteries that are directly made into traditional building materials have also been developed

how to choose so many kinds of batteries is very important in the design

first of all, it is to meet the building requirements. As long as the photovoltaic modules used in ground photovoltaic power stations pass the detection of IEC61215 and meet the requirements of resisting 130km/h (2400pa) wind pressure and 23m/s hail with a diameter of 25mm. The BIPV PV module not only needs to meet the performance requirements of the PV module itself, but also needs to meet the four property experimental requirements of the curtain wall (wind pressure resistance, in-plane deformation, air tightness and water tightness) and the safety performance requirements of the building. Therefore, it needs to have higher mechanical properties and adopt different structural methods

secondly, when selecting crystalline silicon batteries, if there is shelter in some positions, the hot spot problem of crystalline silicon components should be considered. At this time, the bypass diode does not work. Although the degree of shadow does not reach the reverse on voltage of the diode, the hot spot effect produced at this time is not enough to cause damage to the components, but the battery components in this state for a long time will be significantly damaged, Therefore, thin-film battery components should be considered as much as possible in locations with poor sunlight incidence angle and shadows on the facade. The voltage difference between crystalline silicon battery module and thin film battery module is large, and the component voltage produced by different manufacturers is also different, so the electrical part needs to be configured according to the actual situation

junction box needs miniaturization and diversification

junction box is a necessary equipment for connecting battery and other equipment. When it is combined with curtain wall, the building's requirement for it is stealth, so the design of junction box is gradually miniaturized and hidden in the plate gap or inside the outer decorative strip

traditional junction box curtain

small junction box for wall

small cable short connector and multi-component plate combination

the improvement of photovoltaic power generation efficiency, even 0.1 percentage point, is achieved by researchers who spend a lot of energy, time and money, but the loss in the process of cable transmission is nearly 1 percentage point, so how to reduce the loss of cables and other equipment is the key point of attention in BIPV design

indoor and outdoor aesthetics must be considered for the application on curtain walls, so the lines must not be exposed indoors and outdoors. In addition, the combination of series and parallel plates can increase the grouping of battery plates and reduce the impact of individual plate damage on the efficiency of the whole system

micro cable connector

the controller and inverter need to be combined, and the inverter needs to be miniaturized and modularized

at present, many controllers and inverters are designed together, which is convenient for equipment maintenance and reduces the probability of failure. In addition, the damage of individual plates will affect the power of the whole string, lose more installed capacity, and sometimes restrict the improvement of the efficiency of large inverters due to factors such as excessive inverter load participation in the work caused by changes in sunshine conditions, so now it is necessary to consider the modular design of inverters. Now some manufacturers have adopted intelligent sleep technology to improve the maximum efficiency of inverters to 98.6%, The efficiency in Europe has been increased to 97.6%, and the low-voltage 50-500kw capacity is freely combined, and hot plug is supported, which can be installed and maintained without shutdown. In addition, the perfect network communication function is easy to monitor the operation of the whole system, which is a better direction for BIPV in the future

in addition, the micro inverter works separately for each component, which is more conducive to improving the efficiency of the whole system, especially when there are many types of plates and complex use positions. However, at present, this scheme has a high cost and needs to be comprehensively considered

reduce the use of batteries. Photovoltaic modules themselves only generate electricity and do not have the function of power storage. And the electricity generated by the components is directly connected to the national electricity, which does not need energy storage. It can be used safely and seamlessly through the anti countercurrent device. Li is used alone. When the light is not strong or there is no sunshine at night, if you still need electric energy, you need to rely on the battery to provide electric energy. The electricity generated by photovoltaic modules during the day charges the battery and can be used at night, so it is necessary to invest a higher cost to configure energy storage equipment

at present, the mainstream of photovoltaic batteries is maintenance free lead-acid batteries, which have the advantages of low price, low cost, simple maintenance, and the disadvantages of low capacity and short service life. The other is lithium battery, which has the advantages of simple maintenance and high capacity. The disadvantage is that it has just been used in the photovoltaic industry, so the cost is very high, and it can't replace lead-acid battery for the time being. There is also an energy storage device, super capacitor. The advantage is that the capacity can be very high, but the disadvantage is that it is still in the research and development stage and is immature. Therefore, the high investment and high maintenance of the energy storage link are not the future development direction of the system, so we try to reduce it in design

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