Building Integrated Photovoltaics (BIPV): How to Solve Two Major Challenges in the Construction Industry?

In today's era where "environmental protection" and "low carbon" slogans are prevalent, all industries are striving for energy conservation and emission reduction. The construction industry is no exception, with a "green storm" quietly sweeping through. The "trendsetter" is the subject of our discussion today—Building Integrated Photovoltaics (BIPV)! Sounds impressive, right? Don't worry, we'll take you into this amazing field to see how it transforms buildings and the challenges and opportunities it faces.

What is BIPV? A "Super Evolution" in the Construction Industry

Let's explain BIPV, which stands for "Building Integrated Photovoltaic." Simply put, it means that buildings are no longer just "concrete boxes" that shelter us and provide a place to live and work, but instead become "energy giants" that can generate their own electricity!

Previously, to utilize solar energy, we usually installed solar panels on the roofs or exteriors of buildings, like putting an ill-fitting "hat" on the house. This not only affects aesthetics but also occupies space. BIPV is much more advanced; it directly integrates solar photovoltaic materials with building materials, enabling buildings to generate electricity. Imagine future skyscrapers and residential areas where walls and roofs become "magical panels" that absorb sunlight and convert it into electricity. During the day, when sunlight shines, these panels start "working diligently," converting solar energy into electricity for various appliances in the building; at night, the stored electricity continues to "shine," allowing the building to be "self-sufficient." Isn't that cool? This is a "super evolution" in the construction industry!

 

BIPV "Family Members": Material Type and Component Type

The BIPV family has two main "branches." Based on the degree of integration with building materials, they are divided into "material type" and "component type" photovoltaic systems, each with its own "unique skills."

Material Type Photovoltaic System: A "Gorgeous Upgrade" of Building Materials

Simply put, a material type photovoltaic system completely "integrates" solar cells and building materials into new photovoltaic building materials. It's like mixing chocolate and milk to create delicious chocolate milk.

For example, photovoltaic tiles cleverly embed photovoltaic power generation devices into the support structure. Each photovoltaic tile is an independent "small power generation unit" containing solar cells. With these tiles, there's no need to use ordinary tiles on the roof; simply install photovoltaic tiles, which provide shelter and generate electricity—a win-win! Photovoltaic bricks and photovoltaic waterproof membranes also work similarly. They retain the functions of traditional building materials while adding "superpowers" such as energy saving, lightness, and durability. Furthermore, material type photovoltaic systems hide the connecting wires within the tile structure, like giving the wires an "invisibility cloak." This protects them from direct sunlight and rainwater, perfectly solving the problems of aging and poor aesthetics of traditional photovoltaic components. It's a perfect match for buildings and a "powerful assistant" for promoting green buildings in the future!

 

Component Type Photovoltaic System: "Energy Enhancement" of Building Components

A component type photovoltaic system integrates photovoltaic components and building components to create new building components. The most common are photovoltaic roofs, photovoltaic curtain walls, and photovoltaic canopies.

Let's talk about photovoltaic roofs. Everyone knows that building roofs usually have excellent lighting and no obstructions, like a natural "sunlight collection station." The BIPV system utilizes this by encapsulating photovoltaic materials and roof building materials together to create a photovoltaic roof. This allows photovoltaic materials to replace traditional roof insulation materials and generate electricity, saving both energy and money—a "multi-win" situation!

Photovoltaic curtain walls are "star members" of the BIPV family and a "new favorite" in international building-integrated photovoltaics. Traditional photovoltaic panels installed directly on building walls increase the building's load, so they are usually installed on the roof. However, component type photovoltaic systems truly integrate photovoltaics and buildings, reducing the weight of the building's exterior and enhancing its aesthetics. Moreover, photovoltaic curtain walls have high "aesthetic value." Photovoltaic components of various colors can be installed between the glass, creating a colorful artwork from afar. They also absorb solar radiation, with better heat insulation performance than ordinary glass curtain walls. They keep interiors cooler in summer and warmer in winter, making them a versatile "all-arounder."

 

BIPV's "Growing Pains": Heat Dissipation and Shading Issues

Although BIPV sounds "amazing," it has its own "troubles" in practical applications. The most significant are heat dissipation and shading issues, which are two major "obstacles" on BIPV's growth path.

Heat Dissipation Issues: The "High-Temperature Crisis" of Photovoltaic Components

After absorbing solar radiation, the ideal state for solar panels is to convert all light energy into electricity. However, reality is "harsh." Only about 20% of solar radiation is converted into electricity, and most of the rest is converted into heat. It's like eating a bowl of rice, but only a small portion is absorbed and converted into energy by the body, while the rest becomes "heat." This excess heat causes the battery temperature to rise rapidly. If not handled promptly, it can even "damage" the photovoltaic panels. Moreover, for every 1℃ increase in temperature, the photoelectric conversion efficiency decreases by about 0.5%, meaning less and less electricity is generated. To solve this problem, the Building Integrated Photovoltaics/Thermal (BIPV/T) system has "emerged," acting as BIPV's "exclusive air conditioner."

The BIPV/T system adds cooling and heat utilization technology to the BIPV system. It has two main "schools of thought": air cooling and water cooling.

The air-cooled BIPV/T system works like using a fan to cool things down. In its cooling channels, air circulates through natural convection or forced convection with the help of a fan, "blowing away" the heat generated by the photovoltaic system, thereby reducing the temperature of the photovoltaic components and improving power generation efficiency. This system is easy to install and has low costs. Studies have found that increasing airflow speed can significantly improve the electrical and thermal efficiency of photovoltaic panels!

Water-cooled BIPV/T systems are even more "powerful" because water has a higher specific heat and thermal conductivity than air, so it has a stronger ability to absorb heat, allowing the overall performance of the BIPV/T system to be "enhanced". New cooling technologies based on phase change materials are also attracting attention. Phase change materials act like a "super energy storage device", absorbing or releasing a large amount of latent heat during phase change, keeping the temperature of the photovoltaic cells stable.

 

Shading Issues: The "Dark Times" for Photovoltaic Components

In BIPV systems, photovoltaic panels become part of the building. While this offers many advantages, it also brings new challenges. In cities, buildings are densely packed, and trees, other buildings, or even other solar panels on the same building can cast shadows on the photovoltaic panels. This is like someone suddenly using an umbrella to block the sun while you're sunbathing—you wouldn't be happy, and neither are the photovoltaic panels.

A small shadow can significantly reduce the performance of the entire photovoltaic panel. Because the current of individual cells in a series battery group is the same, and the voltage of the cells in a parallel battery group is the same, a shaded cell acts like a "laggard", limiting the output of the entire battery group.

To assess the impact of shading, scientists have devised several methods, such as classifying shadows and using angles to analyze shading conditions, and designing special algorithms to identify shadows. Currently, solutions to shading problems mainly focus on two approaches: one is to improve the structure and control methods of the photovoltaic system, similar to adjusting the division of labor and cooperation among team members, allowing the entire system to operate efficiently even in the presence of shadows; the other is to adjust the angle of the photovoltaic panels, similar to adjusting the angle of a sunshade, to minimize the shaded area and allow the photovoltaic panels to receive more sunlight.

 

The Future of BIPV: Opportunities and Challenges Coexist

In general, BIPV technology has a very broad prospect. It can meet the aesthetic needs of buildings while achieving energy saving and emission reduction, providing new ideas for solving energy and environmental problems. However, current research still has some limitations. For example, in wind cooling technology, the impact of convection on system efficiency needs further research; methods for solving shading problems are not yet perfect, lacking a "one-size-fits-all" optimization solution; technologies to avoid thermal hotspots caused by shading also require further exploration.

However, with continuous technological advancements, these challenges will be overcome one by one. In the future, BIPV may become a "standard" in the construction industry, and we will see more and more green buildings that are both power-generating and aesthetically pleasing. Imagine walking down the streets of the city, with every building "silently generating electricity", providing clean energy for our lives—what a wonderful scene that would be!

Whether you are a professional in the construction industry or an "enthusiastic citizen" concerned about environmental protection, you may want to learn more about BIPV technology. One day, it may bring unexpected surprises to our lives! Let's look forward to the future of BIPV and witness this "green revolution" in the construction industry!