Research on the application of photovoltaic glass in building energy conservation

The global energy crisis and climate change are becoming increasingly serious. Reducing energy consumption and improving energy efficiency have become a global consensus. In the field of construction, energy consumption accounts for about 30% of the world's total energy consumption, of which heating, cooling and lighting are the main sources of energy consumption. Traditional building energy relies on non-renewable fossil fuels, which not only aggravates environmental pollution, but also leads to an increase in greenhouse gas emissions. Therefore, how to achieve energy optimization in buildings and reduce dependence on traditional energy has become an important direction for energy conservation and emission reduction. At the same time, the rapid development of renewable energy has brought new opportunities for building energy conservation, especially solar photovoltaic technology. Photovoltaic technology uses solar energy as an energy source, which is not only clean and pollution-free, but also inexhaustible. With the advancement of technology, the cost of photovoltaic technology has decreased year by year, and the power generation efficiency has steadily increased, becoming an important means to achieve building energy self-sufficiency and reduce energy consumption.1 Basic principles and composition of photovoltaic glass1.1 Working principle of photovoltaic glassThe working principle of photovoltaic glass is based on the photovoltaic effect, which is a physical phenomenon that directly converts solar energy into electrical energy. When sunlight shines on the surface of photovoltaic glass, the semiconductor material inside the glass absorbs photons and excites the electrons in the material to transition. In this process, electrons jump from low energy levels to high energy levels, and form free electron and hole pairs inside the semiconductor material. Through a specific electric field design, electrons and holes are separated, electrons are guided to the negative electrode, and holes are guided to the positive electrode to form a current. This process converts solar energy into electrical energy and realizes photovoltaic power generation. The photovoltaic effect is the core principle of photovoltaic glass power generation and is also its fundamental characteristic that distinguishes it from traditional glass. Traditional glass only has the function of optical transmission and cannot realize the conversion of light energy into electrical energy. Photovoltaic glass can not only transmit light like ordinary glass, but also convert part of light energy into electrical energy, realizing the dual functions of energy-saving power generation. The main difference between photovoltaic glass and traditional glass is that it has the function of solar power generation, which is due to the photovoltaic components integrated in photovoltaic glass. Traditional glass is mainly used for lighting, heat insulation and protection of buildings, while photovoltaic glass has the dual functions of power generation and building materials. Compared with traditional photovoltaic components, photovoltaic glass can be fully integrated with the building surface, reducing the additional equipment occupation and installation costs. Photovoltaic glass has different light transmittances and can be customized according to the functional requirements of the building to achieve a combination of aesthetics and functionality. This feature makes photovoltaic glass gradually gain attention in modern green building design and become an important material to promote the combination of renewable energy and architecture.1.2 Basic structure of photovoltaic glassThe basic structure of photovoltaic glass includes substrate materials, photovoltaic modules and surface treatment layers. The selection of substrate materials is crucial to the performance of photovoltaic glass. Generally, glass substrates with high mechanical strength, weather resistance and light transmittance, such as ultra-white glass, are used. Ultra-white glass can effectively improve the absorption efficiency of solar energy due to its low iron content and high light transmittance. The substrate material needs to have strong heat resistance and UV radiation resistance to ensure stable performance during long-term use. The surface treatment of the substrate is also an important part of improving the performance of photovoltaic glass. Through surface coating or nano-coating technology, photovoltaic glass can improve light transmittance, enhance anti-reflection performance, and thus improve photoelectric conversion efficiency. The integration method of photovoltaic modules is an important part of photovoltaic glass. Usually, the photovoltaic modules of photovoltaic glass are realized by embedding high-quality silicon cells or thin-film cells into the glass layer. High-quality silicon cells are widely used in high-performance photovoltaic glass due to their high photoelectric conversion efficiency, while thin-film cells are suitable for architectural scenes that require high light transmittance because of their lightness and flexibility. Photovoltaic modules can achieve efficient conversion of electric energy while maintaining the basic performance of glass through close integration with glass. The design of integrated mode should not only ensure the power generation efficiency of photovoltaic modules, but also take into account the beauty and durability of the building. Therefore, photovoltaic glass usually adopts lamination technology to embed photovoltaic modules into multi-layer structures, and makes photovoltaic cells and glass fit closely through high temperature and high pressure processes, thereby improving the overall mechanical strength and weather resistance.2 Application of photovoltaic glass in building energy conservation2.1 Application status of building photovoltaic integration technologyPhotovoltaic glass, as the core element of building integrated photovoltaic (BIPV) technology, has received extensive attention in architectural design in recent years. BIPV technology combines photovoltaic glass with building components, so that it not only has the function of power generation, but also takes into account the beauty and functionality of the building. Photovoltaic glass, as a transparent or translucent building material, can replace traditional curtain walls, roofs and windows to achieve the perfect integration of photovoltaic power generation and architectural design. Unlike traditional photovoltaic modules that need to be installed on the surface of the building, photovoltaic glass can be directly integrated into the building structure, avoiding the construction complexity and additional costs brought by secondary installation. Since photovoltaic glass has a variety of appearance forms, it has greater flexibility in architectural design and can be customized according to the aesthetic needs of different buildings, giving buildings a higher degree of design freedom. In the field of building energy conservation, the advantage of BIPV technology is that it can maximize the surface area of the building's facade into a renewable energy production area, greatly improving the overall energy self-sufficiency rate of the building. At present, the global application of photovoltaic glass has gradually extended from the single-function photovoltaic power generation to the comprehensive design concept of green buildings and intelligent buildings, becoming one of the key elements of sustainable building design. Whether in the "positive energy building" promoted in Europe or in the curtain wall design of some super high-rise buildings, the integrated application of photovoltaic glass has shown significant energy-saving effects. Through reasonable design and application, photovoltaic glass can not only help buildings achieve energy self-sufficiency, but also greatly improve the energy-saving level of buildings while maintaining the integrity of the building design. This is also an important direction for the development of green buildings in the future.2.2 The mechanism of photovoltaic glass in building energy conservationPhotovoltaic glass converts solar energy into electrical energy through the photovoltaic effect, reducing the building's dependence on external energy, and has the dual effect of improving the building's lighting and thermal insulation performance. Its mechanism of action can be analyzed from two aspects: power generation function and improvement of building thermal environment. First, the power generation function of photovoltaic glass effectively reduces the energy consumption of buildings. For example, in a commercial office building with photovoltaic glass curtain wall, if the total area of the building's exterior wall is 2000m', 1000m' of it is applied with photovoltaic glass. Assuming that the photoelectric conversion efficiency of photovoltaic glass is 15%, the annual average solar irradiance in the area where the building is located is 1000kWh/m'. In this case, photovoltaic glass can generate electricity annually: 1000m'x1000kWh/m'x15%-150000kWh, which is equivalent to providing 150,000 kWh of electricity to the building every year. If the total annual electricity demand of the building is 500000kWh, photovoltaic glass provides about 30% of the electricity demand, significantly reducing the external energy purchase of the building. Secondly, photovoltaic glass also has significant thermal insulation performance, which can reduce the air conditioning load of the building. Photovoltaic glass can reduce the penetration of solar radiation heat by using special low-e coatings and optimized materials. Taking the same office building as an example, if the photovoltaic glass used can reduce solar radiation heat by 30%, and the total air conditioning load of the building is 200,000 kWh/year, then the air conditioning load that can be reduced each year is: 200,000x30%-60,000 kWh. Therefore, photovoltaic glass not only reduces electricity demand by generating electricity, but also further reduces energy consumption by improving the thermal environment.2.3 Application potential of photovoltaic glass in different building typesThe application potential of photovoltaic glass in different building types is particularly prominent in commercial buildings. Modern commercial buildings, especially high-rise buildings and large shopping malls, have large areas of glass curtain walls, which provide an ideal carrier for the application of photovoltaic glass. By integrating photovoltaic glass into the facade of the building, not only can the surface of the building be fully utilized for power generation, but also the comprehensive needs of commercial buildings for lighting, beauty and environmental protection can be met. Especially for large commercial buildings located in the core area of the city, the application of photovoltaic glass can effectively improve its green building certification level and enhance the competitiveness of commercial buildings in the market with high environmental awareness. In residential buildings, the application of photovoltaic glass also has broad prospects. With the increasing awareness of energy conservation and environmental protection among residents and the maturity of distributed energy technology, more and more residential buildings have begun to adopt photovoltaic systems. Photovoltaic glass, as a beautiful and practical solution, can be used in areas such as windows and balcony guardrails. Through photovoltaic glass, residential buildings can achieve energy self-sufficiency without sacrificing aesthetics. Especially for single-family villas and high-end residential projects, the energy-saving and environmental protection functions of photovoltaic glass have gradually become an important factor in enhancing the value of residential buildings. In public buildings, the application potential of photovoltaic glass is mainly reflected in its sustainability and symbolic significance. Public buildings such as government buildings, educational buildings, and museums usually have a high degree of social attention. The application of photovoltaic glass can not only demonstrate the green and environmental protection concept of the building, but also set a benchmark for sustainable development for the public. In these buildings, photovoltaic glass can not only meet the daily energy needs of the building, but also show the modern sense of the building through its transparent or translucent design, thereby enhancing the public image of the building. Whether it is commercial buildings, residential buildings, or public buildings, the application potential of photovoltaic glass in the field of future building energy conservation cannot be ignored.3 Future application cases of photovoltaic glass in building energy conservation3.1 Photovoltaic curtain wallThe photovoltaic curtain wall is to integrate photovoltaic glass components directly into the building exterior wall to achieve large-area solar power generation on the building surface. In future high-rise buildings, photovoltaic curtain walls will become an important energy-saving technology. It can not only meet the basic needs of building exterior wall materials, such as windproof, rainproof, heat insulation and other functions, but also effectively utilize solar energy resources for power generation. In modern high-rise buildings, photovoltaic curtain wall systems are being widely used in exterior wall design to achieve the combination of building energy conservation and power generation functions. In a practical application case, a commercial office building in Shanghai with a construction area of about 5000m2 was installed on the south facade of the building with a total area of 1000m2 of photovoltaic glass curtain wall system. Each square meter of photovoltaic glass can generate about 150W of electricity, and the total power generation power of the entire curtain wall can reach 150kW. This photovoltaic curtain wall system provides renewable energy for the building by integrating into the building's power network, reducing dependence on the municipal power grid. The system not only has good light transmittance, but also can effectively reduce the indoor daytime lighting demand. Combined with the intelligent control system to adjust the light intensity, it can further reduce the energy consumption of the building.3.2 Photovoltaic skylights and skylightsPhotovoltaic skylights and skylights have broad application prospects in large public buildings such as shopping malls, stations and airports. This photovoltaic glass can not only meet the building's demand for lighting, but also realize the function of solar power generation to combine natural lighting with energy utilization. In a newly built museum in Munich, Germany, the photovoltaic skylight and skylight system was successfully applied to the central hall area of the building, with a skylight area of 600m. The power of each square meter of photovoltaic glass is 120W, and the total power is 72kW. This photovoltaic skylight can not only effectively provide natural light for the museum, reduce the demand for indoor lighting, but also provide green energy for the building's air conditioning and lighting systems through power generation. By using special translucent photovoltaic glass, light is softly introduced into the room without causing excessive direct sunlight and temperature rise, which improves the comfort of visitors. The practical application of this system not only achieves significant energy-saving effects, but also becomes a successful example of the combination of photovoltaic technology and architectural aesthetics.3.3 Photovoltaic sunshades and blinds Photovoltaic glass will be widely used as sunshades and blinds in future buildings, especially for residential and office buildings. They not only have the functions of traditional sunshade equipment, can effectively adjust indoor light and block excessive sunlight, but also use photovoltaic glass to convert light energy into electrical energy to achieve the dual functions of power generation and sunshade. In a smart house in California, the designer adopted the innovative solution of photovoltaic sunshades and blinds. A 200m' adjustable photovoltaic blinds system was installed on the outside of the south-facing windows of the building. These blinds not only have the function of sunshade, but also can generate electricity when there is sufficient sunlight. The power generation capacity of each square meter of blinds is 100W, and the total power generation capacity is 20kW. Through the intelligent control system, the photovoltaic blinds can automatically adjust the angle to reduce solar radiation entering the room in summer and reduce air conditioning energy consumption. In winter, the angle of the blinds will be adjusted to maximize the use of solar energy for power generation, while allowing natural light to enter the room to improve the lighting effect. This dual-function photovoltaic self-leaf window system significantly improves the energy efficiency of the house and becomes an example of future green housing.3.4 Photovoltaic roofIn future green buildings, photovoltaic glass will be widely used in roof design. Compared with traditional photovoltaic panels, photovoltaic glass is more transparent and beautiful, and is suitable for roof renovation of residential, school, stadium and other buildings. In this way, the building can not only achieve its own energy self-sufficiency, but also output excess electricity to the power grid, further promoting the use of renewable energy. In an ecological school in southern France, the photovoltaic roof system is widely used in the architectural design of the entire school building. The total area of the roof is 2000m’. High-efficiency photovoltaic glass panels are used. The power generation power of each square meter of photovoltaic glass panels is 180W, and the total power generation power of the whole system is 360kW. This photovoltaic roof not only provides sufficient energy for the school's daily electricity use, but also transmits excess electricity to the power grid to generate economic benefits. The design of the photovoltaic roof takes into account the beauty and functionality of the building. Through the precise design of the tilt angle, the roof can receive solar radiation to the maximum extent in all seasons throughout the year. The installation of the photovoltaic roof saves a lot of energy costs for the school and achieves the goals of energy saving and sustainable development.4 ConclusionIn the future, material innovation of photovoltaic glass will be the key to improving its performance. New photovoltaic materials such as quantum dot photovoltaic materials and perovskite materials have higher photoelectric conversion efficiency and better optical properties, which are expected to greatly improve the power generation capacity of photovoltaic glass. The application of transparent conductive films and nanotechnology will also enable photovoltaic glass to achieve a better balance between light transmittance, power generation performance and aesthetics, further promoting its application in building energy conservation. With the popularization of the Internet of Things and smart building technology, photovoltaic glass in the future will not only be a power generation device, but also integrate an intelligent adjustment system to achieve linkage with the building energy management system. Smart photovoltaic glass can automatically adjust its photoelectric conversion and light transmittance performance according to external light, temperature and other environmental factors, achieving more efficient energy management and a comfortable indoor environment.