Understanding Building-Integrated Photovoltaics (BIPV): Current Status, Prospects, and Challenges

I. The Era's Mission of Building-Integrated Photovoltaics

The global energy situation is currently severe, and our country is no exception. In our country's energy consumption structure, fossil fuels still account for the majority, but they bring many problems, such as environmental pollution and exceeding carbon emissions, which have a significant impact on the global climate. To achieve sustainable development, it is particularly important to vigorously develop renewable energy. The construction industry is a "major consumer" of energy. Expanding the use of renewable energy in the construction field and reducing reliance on fossil fuels is a key link in the country's sustainable development strategy.

Solar energy is very good; it is inexhaustible and inexhaustible, and it does not pollute the environment during use. It is simply a "treasure" in the energy industry. In recent years, various solar thermal and photovoltaic technologies have emerged, and building-integrated photovoltaic (BIPV) technology has received much attention. BIPV cleverly combines photovoltaic components with buildings, making full use of the surface space of buildings to generate electricity. It is both environmentally friendly and practical, and its development prospects are very broad. Next, let's take a good look at the application status, advantages and disadvantages, and future development trends of BIPV.

II. Application Status of Building-Integrated Photovoltaics

(I) BAPV and BIPV: Differences between the Two Models

In photovoltaic systems, according to the different ways of combining with buildings, they can be divided into two major categories: BAPV and BIPV.

BAPV, which is the combination of photovoltaic arrays and buildings, simply means installing photovoltaic power generation equipment on the surface of an already built building. This is like putting a photovoltaic power generation "coat" on the building. The building acts as a support for this "coat", providing support. The advantage of BAPV is that it is relatively easy to transform, the investment cost is low, and the construction requirements are not high. However, it also has disadvantages, such as it may not be aesthetically pleasing after installation, affecting the overall visual effect of the building. If it is not installed properly, it may also have a negative impact on the indoor environment. Moreover, many buildings did not consider installing photovoltaic systems during the initial design. Later installation will face the problem of repeated construction, wasting building materials and possibly adding extra loads to the building structure.

BIPV is more advanced. It directly installs solar photovoltaic arrays on the outer surface of the building's enclosure structure, making the photovoltaic components an integral part of the building, like the building's "organic cells." At this time, photovoltaic components can not only generate electricity but also act as building materials, undertaking the functions of the building structure and meeting the requirements of building aesthetics, making the building look more fashionable. However, BIPV has higher requirements for photovoltaic components, and the design and construction are more difficult, with many challenges in technological research and development. However, in the long run, the development potential of BIPV is huge.

(II) Various Installation Forms of BIPV

BIPV has various installation forms and can partially or completely replace a component of a building according to customer needs. The specific form to be adopted depends on the comprehensive consideration of regional climate conditions, the structural characteristics of the building itself, and the performance of the photovoltaic components. Moreover, the BIPV system is also flexible. When power generation is high, excess electricity can be stored using an energy storage system or transmitted to the power grid; when power generation is insufficient, electricity is obtained from the power grid to meet the electricity needs of the building.

 

Photovoltaic curtain wall: the building's "power-generating coat": Using photovoltaic components as building glass curtain walls has many advantages. It not only allows the building to maintain its original functions, safety, and aesthetics but also generates electricity throughout the year. In the heating season, the hot air it generates can reduce the building's thermal load, making the interior warmer; in the non-heating season, it can also generate hot water to meet the daily water needs of the household. Moreover, the water circulation in the photovoltaic components can also cool the photovoltaic curtain wall, allowing the entire system to maintain efficient operation. The photovoltaic curtain walls of the China Pavilion at the Beijing World Horticultural Exposition and Jiaxing Railway Station are good examples, both practical and beautiful.

Photovoltaic roof: the "power plant" on the roof: Laying photovoltaic components on the roof forms a photovoltaic roof, mainly in two forms. One is a conventional distributed photovoltaic roof, which is to lay solar panels on an already built roof; the other is a tile-type photovoltaic roof, which replaces traditional tiles with solar tiles, so that the photovoltaic power generation system directly becomes part of the roof, which can generate electricity and play the structural support role of ordinary tiles, killing two birds with one stone.

Other forms: flexible and changeable power generation "assistant": In addition to photovoltaic curtain walls and photovoltaic roofs, BIPV also has many other application forms, such as louver-type, window-type, and sunshade-type photovoltaic power generation systems. These forms are very flexible and can be selected according to different climate conditions, building characteristics, and owner requirements. The purpose is to comprehensively consider factors such as power generation efficiency and carbon emissions to find the scheme with the highest comprehensive benefits.

 

(III) Research Status of BIPV: Exploring Forward

Currently, research on BIPV mainly focuses on several aspects.

One aspect is to focus on the impact of cracks on the power generation system when BIPV components are used as building structural components. Imagine that if the photovoltaic components are cracked, the power generation will definitely be affected, so we need to study how to avoid cracks or how to deal with them after cracks appear.

On the other hand, in cities, there are many high-rise buildings, and clouds, haze, and the obstruction of surrounding buildings will all affect the light, causing the actual output efficiency of BIPV to differ from the theoretical calculated value. Therefore, researchers need to find ways to solve this problem and improve the accuracy of power generation efficiency.

In addition, the temperature of BIPV components is also important. Temperatures that are too high or too low will affect the efficiency and service life of the components. Therefore, it is necessary to find ways to keep the components within a suitable temperature range, extend their service life, and increase power generation.

There is also a lot of research on surplus electricity storage. Now there are many different materials that can be used to store surplus electricity, such as batteries and phase-change materials. However, these materials will have some problems during use, such as batteries may have electrolyte leakage and toxicity release risks, and phase-change materials may have corrosiveness and fire hazards, so better solutions need to be found.

In addition, the situation in different cities is different, the height of buildings and the density of surrounding buildings are also different, and the suitable BIPV types are also different. Studies have found that in open areas with low buildings, photovoltaic tiles and photovoltaic roofs have great potential for power generation; in areas with dense high-rise buildings, photovoltaic curtain walls have more advantages.

Moreover, although BIPV is good for the environment, economic feasibility must also be considered. For example, how to reduce the electricity consumption cost of the entire hybrid system over its life cycle, how to extend the life of BIPV components, and how to achieve green recycling, etc.

Finally, in order to promote the development of BIPV, policies suitable for different stakeholders must be formulated. Policy support, in-depth investigation, and active promotion are all important for the development of BIPV.

 

III. Analysis of the Advantages and Disadvantages of BIPV

(1) Significant Advantages of BIPV

1. Green Energy: Environmental Pioneer: BIPV utilizes solar power generation. Solar energy is the cleanest renewable energy source. The entire power generation process does not cause any pollution to the ecological environment. After a life cycle assessment of BIPV components, it was found that its annual carbon emissions are much lower than traditional energy generation throughout the entire process, from raw material acquisition, production, use to disposal. Moreover, as photovoltaic energy storage technology becomes more mature, the carbon emissions of BIPV can be further reduced; it is truly an environmental "small expert".

 

2. Self-Sufficiency: Reduced Losses: With BIPV, the energy efficiency of buildings can be greatly improved. It can generate electricity on-site, thus minimizing losses during power transmission and distribution, improving power output efficiency, and reducing the cost of solar power generation. It's like generating your own electricity at home, eliminating the need for complicated long-distance power transmission; it's both cost-effective and efficient.

3. Space Utilization: Ingenious Energy Saving: Unlike traditional solar panels (BAPV), BIPV does not require additional land area. It directly utilizes the exterior surface space of buildings, transforming the originally idle building surface into a power generation "site," allowing more types of buildings to use solar power generation, greatly improving space utilization.

(2) Challenges Faced by BIPV

1. Supply-Demand Mismatch: The Problem of Electricity "Time Difference": One of the most troublesome problems with BIPV is the mismatch between supply and demand. Consider this: solar radiation is strongest at noon, when BIPV produces the most solar energy, but at this time, people's electricity demand is not high; after sunset in the evening, the peak electricity demand arrives, but solar energy is gone, relying on grid power. This leads to an imbalance between supply and demand, forming the so-called "duck curve." Moreover, grid power supply is difficult to flexibly respond to the rapid changes in solar energy supply. Frequent switching on and off of generators is not only uneconomical but also increases carbon emissions.

2. Daily Maintenance: Cleaning and Repair Difficulties: In areas with severe air pollution, dust will seriously affect the performance of photovoltaic components. However, cleaning BIPV is not easy because factors such as its size, array distribution, and building height make cleaning very complex. Currently available dust removal robots can hardly meet the cleaning needs of BIPV components, and the design of specialized cleaning tools needs to consider many factors. In addition, BIPV is part of the building; once a problem occurs and requires repair, it will affect the normal use of the building, so its stability requirements are very high, but the current manufacturing level still needs improvement.

3. Fire Hazard: A Small "Vulnerability" in Safety: After fire resistance tests and glass breakage tests on BIPV systems, it was found that when BIPV is used as a roof and curtain wall, there is a high fire risk. This is because arcs in junction boxes and connectors are easily ignited, and if they encounter external fire sources of the building, the consequences are unimaginable. Therefore, fire safety issues must be taken seriously when using BIPV.

4. Lack of Standards: The "Gray Area" of the Industry: Although there are some international standards related to BIPV, such as IEC63092, which covers electrical technology, structure, and safety requirements, these standards lack specific guidance in actual design, and information on BIPV/T and heating, ventilation, and air conditioning integration is insufficient, resulting in some "gray areas" that may hide safety hazards. Moreover, some important tests, such as impact, thrust, temperature cycle, and fire hazard tests, are not included in the commonly used IEC61215 standard; ultraviolet and low irradiance tests are also not included in the UL1703 standard, which has hindered the development of BIPV to some extent.

5. High Cost: A "Roadblock" to Development: Compared with ordinary buildings, the construction cost of photovoltaic buildings is much higher, which is one of the main reasons for the difficulty of BIPV development in China. The cost of photovoltaic power generation, in addition to being affected by government subsidies, is also related to installation costs, light conditions, investment payback period, operation and maintenance costs, etc. Moreover, most BIPV systems are custom-designed according to the unique characteristics of buildings, and existing systems cannot be directly referenced or applied, which further increases design costs.

 

IV. Future Outlook for BIPV

(1) Standardization: The "Compass" for Industry Development

Currently, BIPV in China is in a stage of rapid development, but it still lacks a complete system, regulations, and standards. In the actual design and construction process, photovoltaic components involve multiple technical links, and each link requires corresponding standards for regulation. In the future, based on existing standards such as EN50583 and IEC61730, we can develop more comprehensive industry standards in combination with actual construction conditions. At the same time, by cultivating professional designers and on-site construction personnel, the construction of BIPV systems can be made safer and more standardized.

(2) Informatization: The "Booster" for Precise Design

In the design of photovoltaic buildings, shadows and shading are issues that must be considered. Because even if only a small part of the photovoltaic cells is shaded, it will cause significant energy loss. Now that buildings in cities are very dense, this problem is even more prominent. Although there is currently some photovoltaic design software that can calculate the optimal tilt angle of components in combination with weather and sunlight information, BIPV calculations also need to consider the influence of more surrounding environments. In the future, with the continuous optimization of information platforms, BIPV can combine BIM and GIS technologies to design more precise models, determine the optimal location, angle, and orientation on the building facade, and evaluate economic feasibility.

(3) Popularization: New Hope for Cost Reduction

Currently, the biggest obstacle to the development of BIPV is its high cost. The initial cost of the BIPV system includes the costs of inverters, energy storage systems, grid metering connection equipment, fault protection, wiring, as well as design and installation fees. However, with the continuous maturity of technology, the design and products of BIPV will become more and more standardized, and the cost will gradually decrease. Moreover, if there is a stable fixed price for photovoltaic power generation grid connection, it can also reduce costs, so the application of BIPV in actual projects will become more and more widespread.

(4) Improved Supporting Facilities: A "Protective Umbrella" of Thoughtful Service

To enable widespread application of BIPV in the market, it is necessary to establish complete supporting maintenance facilities and plans. For example, developing specialized cleaning robots to facilitate the cleaning of BIPV components; preparing repair equipment to promptly identify and resolve problems; formulating emergency plans for failures to quickly respond when failures occur. Manufacturers can develop relevant products according to different target markets. At the same time, the living comfort of residents should also be considered, such as ensuring normal water and electricity use for residents through backup power supply schemes in the event of component failures.

 

V. Summary: The Development Path of BIPV

Building-integrated photovoltaics (BIPV) technology, as an innovative application of renewable energy in the building sector, offers new hope in addressing energy and environmental challenges. It has many significant advantages, such as utilizing green energy, achieving self-sufficiency, and improving space utilization. These advantages give it unlimited potential on the path to sustainable development. However, it currently faces several problems, such as supply and demand mismatch, maintenance difficulties, and high costs.

However, looking to the future, with technological advancements, improved regulations, reduced costs, and improved supporting facilities, BIPV is expected to overcome these obstacles and usher in broader development prospects. We can expect that in the near future, BIPV will become a common application in the building industry, allowing more buildings to both provide shelter and generate their own electricity, providing clean and sustainable energy for our lives and making our cities greener and more environmentally friendly.