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Recently, the Beijing Municipal Development and Reform Commission, the Bureau of Finance, and the Housing and Urban-Rural Development Commission jointly issued a notice that six major sunshine projects will be implemented throughout the city to promote the application of photovoltaic power generation. For this purpose, strong subsidy support will be provided, of which the subsidy per kilowatt-hour can be up to 0.4 yuan for five years , In order to achieve the goal of Beijing’s renewable energy accounted for more than 10% by 2022.
It is foreseeable that such strong policy incentives will surely promote the formation of a new wave of application of photovoltaic power generation in Beijing.From the perspective of the application scenarios of the six major sunshine projects, almost all of them are inseparable from the combination with buildings or other facilities. Although the combination of photovoltaics and buildings is not a new topic, there are still many issues worth considering and studying. Especially in the context that the promotion of photovoltaic applications in Beijing is more to serve the Winter Olympics and involves an international image, how to conduct project development and design in an orderly and "artistic" manner is more worthy of consideration for developers.
This article is based on the speech made by Mr. Zhang Fang, deputy director of the Optoelectronic Building Committee of China Construction Metal Structure Association, at a recent conference, in order to bring some reference and thinking to the industry.
A few small things: Before BIPV, there was a gap between buildings and photovoltaics
[First little thing] During the Shanghai Photovoltaic Exhibition one year, we invited several curtain wall companies in Shanghai to have a discussion with a photovoltaic module company. The person from the module company asked, what do you think of our modules being installed on the curtain wall?
People from the curtain wall company said, I dare not use your 3.2mm thick glass.
Later, this meal turned into a silly article.
[Second small matter] One year, the Standards and Rating Department of the Ministry of Housing and Urban-Rural Development commissioned us to find several photovoltaic companies to discuss photovoltaic buildings with the Institute of Building Electricity, China Building Standard Design and Research Institute.
People from the Standards Institute asked that the photovoltaic system installed on the building has become a power source for the building, so how exactly does it meet the electrical requirements of the building?
The two sides never came to a point, and the results broke up.
[The third minor matter] We were once commissioned by the Standards and Ratings Department of the Ministry of Housing and Urban-Rural Development to compile "Technical Guidelines for Building Photovoltaic Systems." At the meeting, the leaders of the Ministry of Housing and Urban-Rural Development said that building photovoltaics is a new thing and its application is not yet mature. I hope you will compile the guidelines into an informative technical document.
As a result, we compiled it into a technical specification.
When submitting for approval, the leader in charge said that you are still bound by traditional standard concepts.
Suddenly understand: by compiling BIPV standards, that gap can be effectively bridged
In 2018, a curtain wall company in Fujian proposed to formulate standards for photovoltaic curtain walls. We told them that in 2012, an enterprise applied to the Ministry of Housing and Urban-Rural Development for the preparation of standards for photovoltaic curtain walls, but the result was not compiled. The reason may be that the standards management department believed that the photovoltaic curtain wall has not changed. The structure and performance of the curtain wall only increase the power generation function. Now that the design specifications for photovoltaic power plants have been released, it can be used in conjunction with the curtain wall technical specifications. There is no need to write repetitive content.
In 2019, the company continued to propose to compile photovoltaic curtain wall standards. They believe that the existing technical specifications for glass curtain walls and photovoltaic power station design specifications cannot be effectively applied in practice. We respected their opinions and agreed to this standard.
When seeking expert opinions on the project, some experts asked, how do you plan to compile this standard? What's the content?
At that time, we really did not form a relatively clear line of thought. I was also in a dilemma for the questions raised by experts. One morning, a sentence suddenly popped out of my mind. It struck me like a bolt of lightning: "The standards are not written, they are researched."
Therefore, I discussed with the editor-in-chief that we should not rush to establish a standard structure, and first clarify the problems with photovoltaic applications on the curtain wall.
The editor-in-chief agreed with my idea, so I set out to design a set of questionnaires and sent it to all the editors. The feedback is still relatively high, especially curtain wall companies, showing great interest. After the comments were collected, I conducted a statistical analysis and ranked the problems of photovoltaic adaptation or inadaptability to the curtain wall, and basically saw which problems needed to be solved.
In response to these problems, we formed a "standard preparation outline." According to the preparation outline, we set up 3 research groups to study corresponding issues.
The first group of research topics is "Photovoltaic curtain wall component development and test research", which mainly studies component size, mechanical properties, optical performance, thermal performance, acoustic performance, and installation requirements;
The second group of research topics is "Photovoltaic Curtain Wall Wiring Development Test Research", which mainly studies wiring types, basic structures, metal trunking components, and frame support components;
The third group of research topics is "Research on the Electrical Adaptability of Photovoltaic Curtain Walls", which focuses on ensuring safety (including extra-low voltage, relay protection, and electric shock protection) and reliable power supply (including photovoltaic modules, inverters, power generation efficiency, etc.).
Although the research group has been established and the research topics have been clarified, the companies undertaking the research and development of the research projects still feel unable to start and the work efficiency is not significant. Why?
After understanding and discovering, one is that they know exactly what the subject is, but they don't know why; the other is that they have a lot of work in the unit and it is impossible to spend all of their time doing this.
How to do it? At this time during the epidemic, we can’t hold meetings together. We held online meetings at the “Tencent Meeting”. We held 6 meetings in total to allow people from curtain wall companies and component companies to have discussions. We also included the standards in the curtain wall standards. Relevant regulations are sorted out for component companies to understand and let them develop samples as required.
In order to save the time of enterprise R&D personnel, we also designed a form for each group, and guided them to obtain test data by filling in the form.
For example, the size of components. Architects must express their ideas when designing. The ideas are expressed through modeling. The curtain wall is the outer skin of the building. Not only must the aesthetic effect be pursued, but also the functional requirements of the building or interior must be met. There are many changes.
As for photovoltaic modules, ground-based power stations have always been the mainstay. The production process mainly considers the pursuit of economic maximization while meeting the strength required by the ground load. As a result, the sizes of modules are also diverse. So, how to unify the size difference between the two?
We have proposed that a certain building modulus is selected as a technical measure to solve the problem, and component companies can give a certain size adjustment range according to their own characteristics to minimize the difference in size.
Another example is to ensure safety. The curtain wall is a building envelope composed of panels and a supporting system. The cables of the photovoltaic system are laid through beams and columns. If the cables are leaking, the supporting system must not become a conductor. In accordance with the requirements of building electrical, we guide enterprises to provide technical measures and solutions.
For example, you can choose extra-low voltage (DC not greater than 120V), even if the beam and column are conductive, the voltage is controlled within a safe range; if the extra-low voltage is not adopted, relay protection can also be used. Once the line leaks, it will be shut down. The device can move quickly; of course, you can also choose to strengthen the insulation in the wiring cavity to make the supporting system form a double protection.
After the draft standard is formed, we attach great importance to the opinions of participating companies. In order to facilitate the discussion, we held three working meetings with the subject group as a unit.
We all know that the current solar cell technology is becoming more and more diversified, and only when different technologies are used in the most suitable places can their greatest advantages be brought into play.
For example, monocrystalline silicon components are more suitable for non-transparent parts of curtain walls. The same is true for inverters. With the development of intelligence, it has more and more functions. As functions increase, costs will increase. If you blindly emphasize the full range of functions, some functions are bound to be idle.
For the photovoltaic curtain wall, the protection of electric shock safety and the improvement of power generation efficiency may be more important. Therefore, we guide the company to focus on the main technical parameters of the company's products in response to the requirements of curtain walls and building electrical.
Tribute: BIPV is now a blue ocean, it will eventually become a red ocean
Compared with ground-based power stations, photovoltaic buildings have more abundant application forms. The initial application of BAPV may be more, and the application of BIPV may increase in the future. The current BIPV is not yet mature, but there is huge room for development, and more innovative companies need to emerge. "Photovoltaic Curtain Wall Application Guide" hopes to arouse more BIPV innovators.
This standard is planned to be completed in one year, but it took more than 7 months for the development and test research. For the development of a new product or new technology, 7 months is obviously rushed, not to mention that there are only more than 30 companies participating in the development and research. Therefore, this standard is just the beginning and provides a direction for the development of BIPV. In fact, greater development is yet to come.
Please believe that BIPV can't finish it. Chinese houses have been built for at least five thousand years, and they are still being built because there are always new types of buildings appearing.
