Research on the Application of BIPV Technology in Super-high-rise Public Buildings in Hot-summer and Cold-winter Regions under the Guidance of Near-Zero Energy Consumption Targets

This paper takes a super-high-rise office building in Guangzhou as an example to explore the technical path for the application of BIPV technology in super-high-rise public buildings in hot-summer and cold-winter regions.

1 Overview of Near-Zero Energy Consumption Buildings

Since the 1980s, China's building energy efficiency design standards have experienced a "three-step" goal of 30%, 50%, and 65% energy saving. With the release of the "Technical Standard for Near-Zero Energy Consumption Buildings" in 2019, a near-zero energy consumption building technology system suitable for Chinese conditions has been gradually established, providing important support for China's exploration of a "new three-step" approach to low-energy consumption, zero-energy consumption, and even energy-producing buildings. Near-zero energy consumption buildings are defined as buildings that adapt to climate characteristics and natural conditions, reduce building heating and cooling needs to the maximum extent through passive technical means, maximize the efficiency of energy equipment and systems, utilize renewable energy, optimize energy system operation, and provide a comfortable indoor environment with minimal energy consumption. Under the guidance of national policies, many places have formulated promotion goals and encouraging policies for ultra-low and near-zero energy consumption buildings. During the "13th Five-Year Plan" period, China has cumulatively built nearly 0.1 billion m of ultra-low and near-zero energy consumption buildings²After more than ten years of exploration and practice, near-zero energy consumption buildings in China have the conditions for large-scale development, and it is expected that they will usher in a period of full-scale outbreak in 2030.

2Overview of Building-Integrated Photovoltaics (BIPV) Technology
2.1 Concept of Building-Integrated Photovoltaics (BIPV) Technology Photovoltaic power generation technology is a clean, stable, and efficient green energy form that converts solar radiation into electricity. Combining photovoltaics with buildings is an important means for China to solve building energy consumption and achieve zero-energy consumption operation of buildings.   Building-distributed photovoltaic systems can be divided into building-applied photovoltaics (BAPV) and building-integrated photovoltaics (BIPV). The former is a traditional building photovoltaic application method, which adds photovoltaic products to the building roof, mainly for later additions. The system shape is not coordinated with the building's appearance, and the installation method poses a great hidden danger to building safety. Building-integrated photovoltaics (BIPV) requires that the photovoltaic system be designed and constructed simultaneously with the building, and the photovoltaics and buildings are perfectly integrated. While fully utilizing the structural and functional characteristics of the building, it achieves green energy production, for building use or connection to the municipal power grid, thereby improving the utilization rate of solar energy in buildings.

Since the 1990s, developed countries and regions such as Germany, the United States, and Japan have begun to use photovoltaic power generation systems in buildings, such as the US Million Solar Roof Plan and the Japan New Sunshine Plan, laying the foundation for the development of photovoltaic building applications. In this aspect, China started late but developed rapidly. In recent years, China has been in a leading position in the world in the fields of photovoltaic products, technology, and engineering, and a large number of excellent examples of BIPV technology applications have emerged, such as the China Pavilion at the World Horticultural Exposition, the Xiong'an Convention and Exhibition Center, and the China Academy of Building Research's photoelectric demonstration building. Photovoltaics are widely used in building roofs, curtain walls, and sunshades.

3 Case Study Analysis
3.1 Project Overview
   The case building is located in the east district of the International Finance City, Tianhe District, Guangzhou, on the north bank of the Pearl River, and belongs to a hot-summer and cold-winter climate zone. The building is a Class A super-high-rise office building (see Figure 1), with the main entrance facing south. The total construction area is 104402.14m²The above-ground construction area is 86919.45m²The underground construction area is 17482.69m²The building height is 176m. The building aims to build the first super-high-rise near-zero energy consumption building in China in a hot-summer and cold-winter region and carries out relevant designs.

Figure 1 Building renderings3.2 Analysis of PV System Application Strategies in Hot-Summer and Cold-Winter Regions

The climatic characteristics of hot-summer and cold-winter regions are long summers without winter, high temperature and humidity, and easy occurrence of catastrophic weather such as typhoons and rainstorms.

The solar altitude in Guangzhou is relatively large, and the radiation is strong. According to Meteonorm software data, the annual irradiance of horizontal plane solar total radiation is 1218 kWh/m²which belongs to Class Ⅲ area. It is advisable to fully tap the building skin space resources to apply solar photovoltaic systems (see Figure 2).

Figure 2 Annual irradiance of horizontal plane solar total radiation and scattering in Guangzhou

   Considering the spatial relationship between the building and the surrounding building groups, Revit software is used to model the building and the surrounding building groups, and the annual irradiance of the building skin's total solar radiation is simulated and calculated, and the results are shown in Figure 3.

Figure 3 Cloud map of annual irradiance of total solar radiation on building skinAs shown in Figure 3, the annual irradiance of the tower roof and the podium roof is better than that of the building facade. The tower roof is not affected by the surrounding buildings, and it is most suitable for applying photovoltaic power generation systems. Due to the influence of surrounding buildings and its own tower, the podium roof shows that the annual irradiance of the south side roof is better than that of the west side roof. The comprehensive annual irradiance of total solar radiation is second only to the tower roof.3.2.1 Roof Photovoltaics and Photovoltaic SkylightsThe tower roof and the podium roof are the best positions for receiving solar irradiation. Standard monocrystalline silicon photovoltaic modules with mature technology and high photoelectric conversion efficiency should be used to maximize photovoltaic power generation under limited paving space (see Figure 4). In addition, the case building has roof gardens on the podium and tower. For spaces with lighting and display needs, translucent monocrystalline silicon photovoltaic modules can be used to create photovoltaic skylights, which combine lighting and power generation functions.
 

Figure 4 On-site image of monocrystalline silicon photovoltaic skylight
3.2.2Photovoltaic shading
   For super-high-rise near-zero energy consumption buildings, applying photovoltaic power generation systems only in the roof space is far from enough to meet their needs for renewable energy power generation. According to the design requirements of buildings in hot-summer and cold-winter regions, multi-layer shading facilities are set up on the west, south, and east sides of the building, projecting 700mm. While effectively reducing the impact of solar radiation on the building's cooling load, it also increases the photovoltaic installation space for the building (see Figure 5).
 

Figure 5 Building facade shading and pointsThere is mutual shading between the multi-layer shading panels. Comprehensive analysis should be carried out in combination with irradiance analysis and application forms to determine the spacing of the shading panels and the type of photovoltaic modules to meet the requirements of safety, economy, and aesthetics.
Using Revit software, a refined building simulation of the sunshade facilities on the standard floor of the building tower was conducted to calculate the annual solar irradiance received under the conditions of 700mm, 800mm, 900mm, 1000mm, and 1100mm longitudinal spacing of the shading components. The results are shown in Figures 6 and 7.

Figure 6 Annual Solar Irradiance Cloud Map of the Sunshade

Figure 7 Comprehensive Annual Solar Irradiance of Sunshades with Different Longitudinal SpacingsAccording to the above results, the annual solar irradiance received by the building sunshade increases with the increase of the longitudinal spacing of the sunshade, but the effect gradually weakens. Considering the factors of building daylighting, spatial vision, and irradiance level, the longitudinal spacing of the sunshade is set to 1100mm.
Considering the mutual shading between the sunshades, it is advisable to choose cadmium telluride thin-film photovoltaic products with less shading influence and better weak-light power generation performance. In particular, the case building uses a unit curtain wall system with integrated shading, requiring the photovoltaic modules to be consistent with the curtain wall separation modulus during integrated application. According to the differences in the production processes of different photovoltaic modules, in the customized application process of photovoltaic module modules, the photoelectric conversion efficiency of cadmium telluride thin-film photovoltaic modules is less affected by the module modulus. Therefore, for building facade multi-layer shading structure integrated photovoltaic applications, cadmium telluride thin-film photovoltaic products are preferred. 3.3 Photovoltaic Building Integrated Photovoltaic (BIPV) Technology Implementation Path Combining the characteristics of the building shape, photovoltaic power generation systems are applied to the sunshades on the east, west, and south sides of the building's podium and tower, as well as the roofs of the podium and tower. As shown in Figures 8 and 9, a steel structure frame is built on the roof of the building tower, and 193 standard monocrystalline silicon photovoltaic modules are installed horizontally, with an installed capacity of 106.15kWp. On the south side of the tower roof, 110 light-transmitting monocrystalline silicon double-glass photovoltaic modules are installed in the form of a skylight, with an installed capacity of 39.82kWp. On the south side of the podium roof, 78 standard monocrystalline silicon modules are installed in a whole-piece manner at a southward inclination of 3°, with an installed capacity of 42.90 kWp. The parameters of the monocrystalline silicon photovoltaic modules are shown in Table 1. As shown in Figure 10, cadmium telluride thin-film photovoltaic modules are applied to the horizontal decorative wings on the east, west, and south sides of the building, totaling 6021 modules, with an installed capacity of 1012.06kWp.
 

Figure 8 Photovoltaic Module Layout Diagram of Building Tower Roof

Figure 9 Photovoltaic Module Layout Diagram of Building Podium Roof Table 1 Parameters of Monocrystalline Silicon Photovoltaic Modules

Figure 10 Application Effect Diagram of Photovoltaic Modules on Building Horizontal Decorative WingsAt the same time, considering the application of super-high-rise buildings and the characteristics of the regional natural environment, BIPV photovoltaic products (TP6+1.52PVB+CdTe3.2mm+1.52PVB+TP6) with tempered glass surfaces are selected to improve the structural strength of the components and avoid problems such as component breakage caused by natural disasters such as typhoons and hail. In addition, perforated aluminum plates are set below the photovoltaic modules as a photovoltaic module anti-detachment measure to ensure pedestrian safety. The perforated aluminum plates can also provide good ventilation conditions for the photovoltaic modules, avoiding the risk of fire caused by excessive back panel temperature of the modules.
Based on the above measures, the safe and stable operation of the building shading photovoltaic system is ensured, as shown in Figure 11.
 

Figure 11 Node Diagram of Photovoltaic Module Layout on Building Curtain Wall Horizontal Decorative Wings Table 2 Parameters of Cadmium Telluride Thin-Film Photovoltaic Modules

The component parameters are shown in Table 2. 3.4 Carbon Reduction Effect Assessment of Building Photovoltaic System
According to the annual solar irradiance and ambient temperature in Guangzhou, considering factors such as the shading of different orientations of the building facade, mutual shading between the horizontal decorative wings of the curtain wall, power loss of the inverter, and power loss of the cables, the annual power generation of the building photovoltaic system in the first year is calculated to be 653,400 kWh, and the power generation per unit building area is 7.52 kWh/m².²Among them, the power generation of the building curtain wall horizontal decorative wing photovoltaic system accounts for 69.31%, the power generation of the tower roof non-transparent photovoltaic system accounts for 17.22%, the power generation of the podium roof non-transparent photovoltaic system accounts for 7.02%, and the power generation of the tower roof transparent photovoltaic system accounts for 6.46%, as shown in Figure 12.
 

Figure 12 Power Generation Ratio of Building Photovoltaic SystemConsidering that the life cycle of the photovoltaic modules is 25 years, and taking the first-year attenuation rate of 2% and the annual attenuation rate of 0.45% from the 2nd to 25th year as the calculation basis, the total power generation of the building photovoltaic system over its entire life cycle is calculated to be 1,525,170 kWh, and the average annual power generation is 610,100 kWh, as shown in Figure 13.
Combining the building's own energy saving, active energy efficiency improvement, and renewable energy application special designs, the comprehensive energy consumption value of the building has reached 29.36 kWh/m²·a, the building's own energy saving rate is 51.0%, the comprehensive energy saving rate is 61.0%, and the renewable energy utilization rate is 25.4%, meeting the requirements of the national standard "Technical Standard for Near-Zero Energy Consumption Buildings" for near-zero energy consumption buildings.
 

Figure 13 Annual Power Generation of Building Photovoltaic System 4 Conclusion
Large public buildings have large volumes and high energy consumption, and have high energy-saving potential. Vigorously promoting ultra-low, near-zero, and even zero-energy consumption buildings will be an important way to implement China's dual-carbon strategy in the building sector. Among them, building-integrated photovoltaics (BIPV) technology is one of the necessary means to realize building energy production, promote the high-quality application of photovoltaics in buildings, and support buildings to meet near-zero energy consumption targets. This article, combined with a super-high-rise public building in a hot-summer and warm-winter region, deeply explores the application potential of building-integrated photovoltaics (BIPV) technology and summarizes the application paths of BIPV technology in buildings of the same climate zone and type as follows: (1) It is advisable to fully utilize the horizontal surface solar irradiation resources such as the roofs of towers and podiums, and give priority to using more efficient crystalline silicon photovoltaic modules to create photovoltaic skylights combined with rooftop gardens, etc., to improve the power generation of the building photovoltaic system. (2) The facade space of super-high-rise buildings is an important potential resource for improving the energy production of building photovoltaic systems. At the same time, building shading is a necessary measure for passive energy saving in buildings in hot-summer and warm-winter regions, and fixed external shading has become the best scenario for BIPV technology application. (3) For super-high-rise building shading BIPV systems, it is advisable to give priority to using photovoltaic products with tempered glass surfaces to minimize the impact of dynamic loads generated under natural conditions on the components, and at the same time, perforated aluminum plates are set below the components to ensure the safe operation of the building photovoltaic system.

Source: Excerpt from "Construction Technology" 2025 Issue 17