The large-scale use of fossil energy has made mankind transition from the agricultural era to the industrial era, and today's information age also needs a steady stream of energy for support. However, the high carbon emissions and high pollution caused by fossil energy have caused major changes in the global climate in less than 200 years. Have friends in the north realized that in the past two years, the precipitation in northern my country has been significantly higher, and there have been more severe floods in cities. In April this year, the highest temperature in India reached an astonishing 55°C. Environmental and climate issues pose increasing risks to society, businesses and individuals. Under the initiative of the Paris Agreement, global carbon dioxide emissions need to be curbed immediately and achieve a 80% reduction in carbon emissions in 2050 compared to 1990- 95% of the target. According to a research report by Tsinghua University in my country, by 2050, non-fossil energy should account for more than 70% of primary energy consumption, and non-fossil energy will account for about 90% of total power generation. It can be seen that under the premise that my country's energy strategic goals remain unchanged, solar photovoltaic power generation will usher in a trillion-level market scale in the next 30 years. In the past 10 years, the compound growth rate of China's photovoltaic installed capacity from 2010 to 2021 was 63.7%. In 2021, China's newly installed photovoltaic capacity was 54.9GW. China has also become the country with the largest installed renewable power generation capacity in the world.
1. centralized photovoltaic and distributed photovoltaic
The centralized photovoltaic power station is the initial application form of photovoltaic power generation in China. The centralized photovoltaic power station refers to the large-scale photovoltaic power station constructed in a centralized manner by utilizing the vast space and relatively stable solar energy resources in desert areas. Make full use of the positive peak shaving characteristics of solar radiation and electricity load to play the role of peak shaving. However, there are shortcomings in the practical application of concentrated photovoltaic. my country's economic center of gravity is in the southeast coastal areas, and its electricity demand is much higher than that in the sparsely populated northwest areas. Since the power transmission and distribution capacity of the power grid is far less than the power generation capacity of centralized photovoltaic, it has led to a serious phenomenon of "light abandonment". Although my country's UHV technology has alleviated the problem of west-to-east power transmission in recent years, the overall situation is still not optimistic.
Therefore, in order to ease the construction pressure of centralized power plants, the state vigorously advocates solutions for distributed photovoltaic power plants. Distributed photovoltaic power plants generally refer to power generation systems with small installed capacity and arranged near users. It is generally connected to a power grid with a voltage level of 10 kV or lower, and has the characteristics of relatively small output power, easy promotion, low pollution, and can relieve power shortage in local areas. In recent years, with the vigorous promotion of distributed photovoltaic, the proportion of centralized photovoltaic installed capacity has continued to decline. In terms of total volume, the installed capacity of centralized photovoltaic in China will still be 199.1GW in 2021, accounting for 65.0% of the total installed photovoltaic capacity in China. However, in terms of increments, in 2021, the newly installed capacity of distributed photovoltaic in China will be 29GW, accounting for 55% of the total installed capacity of photovoltaic in the whole year.
2. BAPV and BIPV
With the gradual development of distributed photovoltaic power stations in cities, in order to save the land for photovoltaic facilities, buildings and distributed photovoltaic are a perfect combination, so urban buildings have become the main carrier of solar photovoltaic. The "Notice on the Pilot Program of Roof Distributed Photovoltaic Development in the County" issued by the China Energy Administration pointed out that the proportion of photovoltaic power generation installed on the total roof area of party and government buildings shall not be less than 50%; the total roof area of public buildings can be installed with photovoltaic power generation. Less than 40%; the total roof area of industrial and commercial plants can be installed with photovoltaic power generation ratio of not less than 30%; the total roof area of rural residents can be installed with photovoltaic power generation ratio of not less than 20%. This policy further accelerates the application of distributed photovoltaic in buildings. At present, there are two main forms of photovoltaic buildings: BAPV (Building Attached Photovoltaic), also known as "installed" solar photovoltaic buildings and BIPV (Building Integrated Photovoltaic), also known as building integrated photovoltaic.
The main form of BAPV is to attach the photovoltaic system to the surface of the building, which is mainly used on the roof, and the ordinary photovoltaic modules are fixed on the color steel tile or cement roof through the bracket. BIPV is the integration of photovoltaic power generation devices into buildings, which can be applied to scenes such as curtain walls/shading/greenhouses in addition to roofs. The table below shows the differences between BAPV and BIPV in various aspects.
BIPV is superior to BAPV in terms of design, material, performance, construction, maintenance and cost. It stands to reason that BAPV should be completely replaced by BIPV. However, actual data shows that in 2019 and 2020, the newly installed capacity of BIPV in the world was 1.15GW and 2.3GW respectively, accounting for only 0.95% and 1.73% of the newly installed PV capacity in that year; among them, the installed capacity of BIPV in China in 2020 was 709MW, accounting for only 709MW. The domestic distributed photovoltaic installed capacity accounted for 4.5%, accounting for 1.5% of the total newly installed photovoltaic capacity. Why does BIPV only account for such a small market share after winning BAPV? In fact, this is mainly due to the application scenarios of building photovoltaic. Building photovoltaic are divided into incremental market and stock market, and BAPV and BIPV have different focuses.
BAPV is mainly used in stock transformation:
(1) It is easy to approve and approve, and the building renovation needs to be approved by the relevant departments, and the difficulty of approval can be reduced without changing the original building structure;
(2) Cost-effective, if the roof is well maintained, photovoltaic brackets can be added after simple treatment;
(3) The construction period is short, the original roof does not need to be removed, and the construction time is reduced; (4) The damage to the original building is reduced, and the reconstruction of the roof is easy to damage part of the old building structure, and the erection of brackets can reduce the degree of structural change.
BIPV is more suitable for new buildings, mainly in the following points:
(1) It is convenient for acceptance, new buildings must meet mandatory building standards, and the integrated building structure is convenient for acceptance;
(2) The investment is low, BIPV is formed at one time, and no later transformation is required;
(3) The construction precision is high, and the new large-scale buildings are designed by the design institute in a unified manner, and the requirements for the building structure are clear, which can reduce the hidden dangers of accidents in the later stage;
(4) Increase the installed capacity of photovoltaics, and BIPV can be designed for roofs and facades to increase the energy-saving effect of buildings;
(5) The design consistency is strong, and the aesthetics of the building is improved.
