Are there always problems with photovoltaic building construction? These tips will teach you how to control quality!

Against the backdrop of the "dual carbon" goals, photovoltaic buildings are becoming increasingly common in our lives. Take Copper Indium Gallium Selenide Photovoltaic Building Integrated (CIGS-BIPV) as an example; it's a hot topic right now. This technology uses CIGS photovoltaic modules as building facade enclosure materials, perfectly integrating photovoltaic cell modules with the building, as if dressing the building in a power-generating "coat."

However, domestic photovoltaic building integration projects are currently in their early stages of development, with imperfect related specifications and a lack of construction experience. But with strong national support and advocacy, this industry has seen rapid development, with more and more projects commencing construction. Problems have arisen alongside this growth, making quality control during engineering construction increasingly important. If quality is not up to par, it will not only affect the normal use of the building but also pose potential safety hazards. Today, combining with actual projects, let's have a good talk about quality control in CIGS-BIPV engineering construction.

The "Unique Character" of Copper Indium Gallium Selenide Photovoltaic Building Integrated Projects

The photovoltaic curtain wall system of CIGS-BIPV projects is somewhat like a double-skin ventilated facade system, mainly composed of the building's enclosure walls, photovoltaic electrical system, insulation layer, air ventilation layer, and the CIGS photovoltaic exterior wall layer. Its biggest highlight is using CIGS photovoltaic modules as curtain wall material, integrating the photovoltaic power generation system tightly with the building, as if they were born as one.

However, the construction of such projects is not simple. It involves cross-disciplinary work across multiple specialties such as curtain wall construction, photovoltaic power system installation, and waterproofing. For example, it's like a large symphony orchestra performance, where each instrument section must cooperate seamlessly, and a slight error can disrupt the rhythm. The interlocking of different professional processes and the continuous application of new materials place higher demands on the professional quality of construction personnel. Moreover, current related technical solutions are not mature enough, and standard specifications are not very clear, which makes engineering quality control more complex, like finding a way in the fog, requiring extreme caution.

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The "Quality Troubles" of a Certain Building Demonstration Project

To better understand the construction quality issues of CIGS-BIPV projects, let's take a certain building demonstration project as an example. Researchers carefully reviewed the construction records and completion archives of this project and, in comparison with the "Technical Specification for Application of Building Copper Indium Gallium Selenide Thin-Film Photovoltaic Systems," classified and organized the engineering quality problems. After organizing, it was found that there were indeed many construction quality problems, mainly concentrated in two aspects: the building enclosure system and the photovoltaic power generation system. Among the key control items of the building enclosure system, problems were particularly prominent. For example, unqualified connection or support strength of photovoltaic components to the main building structure occurred 26 times; fire prevention and firefighting requirements not met, 12 times; incomplete fire blocking, 8 times; insufficient airtightness, watertightness, and wind pressure resistance of the photovoltaic curtain wall, 4 times; lightning down conductor and lightning arrester installation not meeting design requirements, 3 times; installation deviation of columns and beams, 2 times; building material performance of photovoltaic modules not conforming to corresponding building material standards, 2 times.

 

In general projects, there were also many issues. For example, photovoltaic systems not matching the building, resulting in poor aesthetic appearance, occurred 10 times; installation deviation between photovoltaic arrays and the building's surface layer, 7 times; substandard aluminum profile surface treatment, 5 times; unreasonable setting of ventilation openings for heat dissipation cavities, 4 times; spontaneous glass breakage, 2 times.

The photovoltaic power generation system also had quality issues. In the main control items, unreasonable stringing and confluence of photovoltaic components occurred 8 times; hot spot effect caused by component shading, 5 times; lightning protection grounding device not reliably installed, 2 times; incorrect material and equipment selection, 1 time. In general projects, longitudinal and transverse installation deviation of photovoltaic components occurred 7 times; unreasonable cable laying, 3 times; loose electrical connection of the photovoltaic system, 1 time. Other issues included damage to photovoltaic modules during transportation, hoisting, and handling, 3 times; hidden cracks in photovoltaic modules, with specific frequency not yet mentioned, but also a problem that cannot be ignored.

To identify the main quality problems, researchers used Pareto chart analysis. Simply put, this involves ranking these problems from highest to lowest frequency of occurrence, then calculating the cumulative frequency. Generally, problems with a cumulative frequency of 0-80% are defined as major problems and managed with priority; those in the 80-90% range are secondary problems, managed as a secondary priority; and those in the 90-100% range are general problems, managed conventionally.

Taking the main control items of the building enclosure system as an example, analysis revealed that unqualified connection or support strength of photovoltaic components to the main building structure and fire prevention/firefighting requirements not met fell within the [0,80%] frequency range. These two issues were thus identified as the main quality problems among the key control items of the building enclosure system. Using this method, after analyzing all projects, a total of 8 main construction quality problems were identified: unqualified connection or support strength of photovoltaic components to the main building structure, fire prevention and firefighting requirements not met, photovoltaic system not matching the building resulting in poor aesthetic appearance, installation deviation between photovoltaic arrays and the building's surface layer, unreasonable setting of ventilation openings for heat dissipation cavities, unreasonable stringing and confluence of photovoltaic components, longitudinal and transverse installation deviation of photovoltaic components, and damage to photovoltaic modules during transportation, hoisting, and handling.

 

The "Mysterious Drivers" Behind Quality Problems

Having identified the main quality problems, the next step is to investigate the reasons behind them. Researchers first identified potential influencing factors for the main quality problems through expert interviews and literature analysis. Then, based on the grey relational analysis method, these influencing factors were quantitatively analyzed to obtain critical influencing factors for engineering quality. Finally, the KJ method was used to summarize and categorize the critical influencing factors, leading to the causes of the quality problems.

"5M1E" Analysis Method for Identifying Influencing Factors

Taking the quality problem of "unqualified connection or support strength of photovoltaic components to the main building structure" as an example, researchers identified its influencing factors based on the "5M1E" method through expert interviews and literature analysis. Regarding personnel, subsequent construction might damage embedded parts and supporting structures, and operators might not follow specifications, have low technical skills, or lack a sense of responsibility. Regarding materials, relevant quality parameters for embedded parts might not be strictly controlled. Regarding construction machinery, construction tools might lack daily maintenance. Regarding construction methods, the arrangement of construction procedures might be unreasonable, quality acceptance for procedures might be inadequate, strength tests for embedded parts and supporting structures might not be thoroughly performed, and schedules might be accelerated to meet deadlines while neglecting quality. Regarding the environment, adverse weather conditions like typhoons might cause damage to finished products.

 

For the other 7 major construction quality problems, the same analysis method was used to derive their respective influencing factors.

Identifying Key Factors Using Grey Relational Analysis

After initially identifying a list of influencing factors for major construction quality issues, researchers used grey relational analysis for quantitative analysis. Grey relational analysis theory is suitable for relational analysis of systems with "small samples, poor information, and uncertainty," making it ideal for weighting these influencing factors.

Specifically, 5 experts were invited to score the influencing factors. The highest score was selected as the reference series, and then the formula was used to calculate the weight correlation. A higher correlation indicates a more important factor. Through a series of calculations, the weight coefficient of each influencing factor for quality issues was determined. Influencing factors with a weight coefficient greater than 0.120 were selected as key influencing factors. Analysis identified a total of 20 key influencing factors for major construction quality issues in the project.

 

For example, for the issue of unqualified connection or support strength between photovoltaic components and the main building structure, the calculation showed that factors such as unreasonable construction process arrangement, inadequate process quality acceptance, operators not following specifications, low technical level, and lack of responsibility had larger weight coefficients and were identified as key influencing factors.

Summarizing Causes Using KJ Method

Researchers used the KJ method to summarize the 20 key influencing factors, ultimately determining the specific causes of the project's construction quality issues. There were 8 causes in total: unclear photovoltaic building integrated management, erroneous subcontractor selection, insufficient management personnel capabilities, poor organizational division of labor, imperfect relevant standards and specifications, unclear technical handover, poor process quality control, and improper procurement management. Among them, "unclear photovoltaic building integrated management" is the primary cause of construction quality problems at this stage.

This is like a football game; without a clear tactical arrangement and command, players fighting individually will naturally find it difficult to achieve good results. In photovoltaic building integrated projects, unclear management can easily lead to chaos in various aspects, resulting in frequent quality problems.

Practical Strategies for Stage-by-Stage Quality Control

After finding the causes of quality problems, the next step is to address them and propose corresponding quality control measures. Researchers proposed measures for the pre-construction, in-process, and post-construction stages to improve the project's quality control level.

 

Pre-Construction Control: Providing Quality "Preventive Measures"

Pre-construction quality problems are mainly due to five reasons: unclear photovoltaic building integrated management, erroneous subcontractor selection, insufficient management personnel capabilities, poor organizational division of labor, and unclear technical handover. The following control measures address these issues.

First, establish a photovoltaic building integrated management system. Clarify the requirements of integrated projects, including "three simultaneous" requirements (unified planning, simultaneous design, simultaneous construction, and simultaneous commissioning); aesthetic requirements (making photovoltaic buildings both practical and aesthetically pleasing); and technical requirements (ensuring the technical feasibility of the project). Enterprises should integrate photovoltaic building project management into the existing building project control process to achieve the "three simultaneous" goals and incorporate copper indium gallium selenide photovoltaic building projects into the main building project management.

Second, use a combination of qualitative and quantitative methods based on the analytic hierarchy process to evaluate subcontractor capabilities and establish a decision-making model for selecting professional engineering subcontractors. Similar to selecting excellent partners, comprehensive consideration should be given to aspects such as construction experience, quotation, construction capabilities, reputation, management personnel quality, and worker quality to select satisfactory subcontracting teams and avoid affecting project quality due to erroneous subcontractor selection.

Third, establish an employee training and assessment system to improve the quality awareness of management personnel. Conduct regular weekly training for management and operational personnel, followed by assessments and public announcements of results to encourage employees to improve construction quality control levels. Only by improving employees' professional skills can project quality be better guaranteed.

 

Fourth, optimize the establishment of the quality management organizational structure. Form a quality management team by assigning specialized personnel from the construction unit. This team is fully responsible for the quality management of various professional sub-projects, ensuring that each link has strict oversight and improving the quality management level of integrated projects.

 

Finally, strictly implement the technical handover system. Optimize the existing technical handover process by adding on-site handover and on-site supervision. This allows installation workers to better understand construction requirements, promptly identify construction deviations, reduce construction errors, and ensure quality from the outset.

In-Process Control: Real-time Monitoring of the Quality "Lifeline"

In-process quality problems are mainly caused by poor process quality control and inadequate quality assurance measures. The following control measures address these issues.

On the one hand, establish and improve construction quality assurance measures. This includes a construction drawing review system to ensure that construction drawings are error-free; equipment and material management specifications to guarantee the quality of materials and equipment; construction specifications to provide standards for the construction process; a dynamic inspection system to promptly identify problems; procurement guarantees to ensure that purchased materials meet requirements; and a quality assessment reward and punishment system to incentivize construction personnel to ensure quality.

 

On the other hand, strengthen project process quality control using dynamic control principles. Just as driving requires constantly observing road conditions and adjusting speed and direction based on the actual situation, during construction, it is necessary to continuously collect actual data, compare it with planned values, and take control measures promptly if deviations are found to ensure that project quality remains within a controllable range.

Post-Construction Control: Conducting Quality "Review and Summary"

Post-construction quality problems are mainly due to imperfect relevant standards and specifications and improper procurement management. The following control measures address these issues.

First, establish an engineering evaluation system. This includes project planning and design quality evaluation, construction quality evaluation, and post-project quality evaluation. By reviewing the quality management of the entire project process, summarizing lessons learned, and promptly optimizing existing quality control measures, this provides references for future projects and effectively safeguards construction quality.

 

Second, optimize the project procurement process and establish a quality assurance system. From the preparation of material and equipment procurement plans, through approval, determination, preparation of bidding documents, review by the owner and supervisor, determination of qualified suppliers, qualification review, bidding announcement, bidding evaluation, determination of the winning bidder and contract signing, to strengthening inspection and testing, intermediate inspections, organization of entry, organization of four-party acceptance, disposal of non-conforming products, warehousing, and distribution of materials and equipment, strict control is necessary to ensure the quality of purchased materials and equipment and avoid affecting project quality due to procurement issues.

Conclusion

Copper indium gallium selenide photovoltaic building integrated projects are a promising technology, but quality control is crucial during construction. Through research on a building demonstration project, we summarized the construction characteristics of such projects, identified major construction quality problems, analyzed the causes of the problems, and proposed quality control measures for the pre-construction, in-process, and post-construction stages. We hope that these research findings will provide guidance for the quality control of photovoltaic building integrated project construction, making future photovoltaic buildings both energy-efficient and safe, and contributing to the achievement of "dual carbon" goals.