Building-Integrated Photovoltaics (BIPV): Exploring the Charm of Green Energy

According to the GlobalABC 2022 Status Report, globally, buildings account for 37% of carbon emissions and 34% of energy demand. In China, the carbon emissions of buildings throughout their lifecycle have reached 51.3% of the national total, with building operation alone accounting for 22%. Therefore, developing low-energy green buildings and changing the current high-input, high-consumption, high-pollution, and low-efficiency model has become an inevitable trend.

 

 

 

Building-Integrated Photovoltaics (BIPV) is a technology that integrates solar power generation (photovoltaic) products into buildings. It combines or integrates photovoltaic arrays with buildings by using photovoltaic components as part of the building's envelope, such as roofs, facades, and canopies, providing both electricity and serving as a functional part of the building structure.
 

BIPV Classification

Depending on how the photovoltaic array is combined with the building, BIPV can be divided into two categories: one is the combination of the photovoltaic array and the building, where the photovoltaic components are directly installed on the outer surface of the building's envelope, such as the roof and walls, providing electricity while serving as part of the building. The other is the integration of the photovoltaic array and the building. This method has higher requirements for photovoltaic components; the photovoltaic components must not only meet the functional requirements of photovoltaic power generation but also the basic functional requirements of the building, such as light transmission, wind and rain protection, and heat insulation. Common integrated forms include photovoltaic tile roofs, photovoltaic curtain walls, and photovoltaic skylights.

 

Advantages of BIPV

 

• Green Energy: BIPV utilizes solar power generation without causing environmental pollution; it is a new concept in solar power generation.
• No Land Occupation: Photovoltaic arrays are generally installed on idle roofs or exterior walls without requiring additional land, which is particularly important for urban buildings where land is expensive.
• Grid-Connected Photovoltaic System: BIPV systems typically use grid-connected photovoltaic systems, eliminating the need for batteries, saving investment and eliminating limitations imposed by battery charge status, allowing full utilization of the electricity generated by the photovoltaic system.
• Building Energy Saving: Photovoltaic arrays absorb solar energy and convert it into electricity, significantly reducing the overall outdoor temperature, reducing wall heat gain and indoor air conditioning cooling load, and achieving building energy savings.

 

 

Requirements for BIPV Systems

A complete BIPV system includes photovoltaic components, a charge controller (in stand-alone systems), a power storage system (usually consisting of the utility grid or multiple batteries in stand-alone systems), power conversion equipment (such as inverters, used to convert the DC output of the photovoltaic components into AC power compatible with the utility grid), backup power (such as a diesel generator, usually used in stand-alone systems), and appropriate support and mounting hardware, wiring, and safety disconnect devices.

 

Battery

For grid-connected photovoltaic systems, since they are not limited by battery capacity and have the public power grid as backup, when determining the photovoltaic array capacity, it is not necessary to undergo rigorous optimization design like stand-alone photovoltaic systems. It can be determined based on load requirements and investment conditions after appropriate calculations. For general household use, the typical range of solar cell array capacity is 1-5 kilowatts.

 

Photovoltaic Components

Unlike ordinary flat-plate photovoltaic components, since (BIPV) components have both power generation and building material functions, they must meet the performance requirements of building materials, such as heat insulation, insulation, wind resistance, rain protection, light transmission, aesthetics, and sufficient strength and rigidity, resistance to damage, ease of construction, installation, and transportation. To meet the needs of building projects, solar cell components of various colors have been developed for architects to choose from, making the building colors more harmonious with the surrounding environment. According to the needs of building projects, various solar cell components that meet the performance requirements of roof tiles, exterior walls, and windows have been produced. Their shapes are not only standard rectangles but also triangles, rhombuses, trapezoids, and even irregular shapes.

 

 

Installation Method

In stand-alone photovoltaic systems, the photovoltaic array should be installed as close to an equatorial tilt as possible, and the angle between the array and the horizontal plane should be carefully calculated to achieve maximum and balanced output from the photovoltaic array. In grid-connected photovoltaic systems, only the maximum output of the photovoltaic array needs to be considered. However, in practical applications, due to the need to conform to the shape of the building, the array may have various orientations, and the angle may range from 0 to 90 degrees.

 

Inverter

The solar cell array outputs low-voltage DC electricity. To connect to the grid, it must be converted into 220V, 380V, or even higher voltage AC electricity. There are also strict requirements for power quality parameters such as voltage, fluctuation, frequency, harmonics, and power factor. To ensure grid, equipment, and personal safety, grid-connected detection and protection devices must be equipped. There are clear regulations for handling over/under voltage, over/under frequency, grid power failure (anti-islanding effect), grid reconnection, DC isolation, lightning protection and grounding, short-circuit protection, circuit breakers, and power direction protection. Therefore, the inverter and controller are key equipment in grid-connected photovoltaic systems.

 

 

Meter

In household grid-connected photovoltaic systems, the electricity generated by photovoltaics is mainly used to supply user loads, with excess power fed into the grid. The electricity consumed by the user load is also jointly supplied by the photovoltaic array and the public power grid. In principle, one meter can be used for metering; the meter rotates forward when the grid supplies power, and rotates backward when the photovoltaic array feeds power to the grid. In practice, because most governments implement preferential policies for the development and utilization of new energy sources, the grid-connected electricity price of solar power generation is currently much higher than the user's electricity price, and two meters are often used for separate metering, hence the distinction between "buy-in" and "sell-out" meters.

 

Summary: According to statistics, China's newly installed BIPV capacity reached 11.9 GW in 2022 and approximately 24.5 GW in 2023. Zhongtou Industry Research Institute predicts that China's newly installed BIPV capacity will reach 34.2 GW in 2024, with a compound annual growth rate of approximately 23.09% over the next five years (2024-2028), reaching 78.5 GW in 2028. This shows that the global BIPV market will reach new heights and is expected to continue expanding and experiencing explosive growth in the coming years.