Trillions of yuan in Building-Integrated Photovoltaics (BIPV)! A comprehensive overview of project plans, application design, and investment returns

01

Practical BIPV Project Plans

1. BIPV Project Installation Plan

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2. BIPV Project Design Plan

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3. BIPV Project Technical Plan

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4. BIPV Project Return Calculation

5. BIPV Project Case Introduction

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02

Four Major Application Forms of BIPV

With the rapid development of the construction industry and the ingenious ideas of architectural designers, the forms of building envelopes are becoming increasingly diversified. As a deeper manifestation of building envelope structures, building-integrated photovoltaics have also emerged in various application forms on buildings. Below are several application forms of BIPV in buildings for your reference.

Skylights: Ideal for daylighting, high power generation efficiency;

Curtain walls: Good demonstration effect, diverse forms, beautiful;

Sunscreens: Blocks sunlight while generating electricity to supplement energy;

Railings and floors: Make full use of space, easy and convenient installation.

Application of BIPV in Buildings

 

1. Photovoltaic Glass Curtain Wall

Install photovoltaic curtain walls in areas with sufficient daylighting between glass curtain wall layers and facade areas requiring sunshade design, integrating building decoration, building sunshade, and power generation. Its structural principle is exactly the same as that of glass curtain walls, and the curtain wall form can be made into various forms such as full hidden frame, full bright frame, and semi-hidden frame.

Photovoltaic glass curtain wall systems can be custom-made for projects or structurally modified for existing curtain wall systems; the back of the photovoltaic panels can be lined with different colors to suit different architectural styles. Photovoltaic curtain walls integrate power generation, sound insulation, heat insulation, and decoration functions, combining photoelectric technology with curtain wall technology, representing a new direction in the development of curtain wall technology.

It collects, converts, stores, and transforms natural light through solar cells and semiconductor materials, and finally connects to the building's power supply network to provide reliable power support for the building.

Photovoltaic Curtain Wall Node Diagram

 

2. Photovoltaic Glass Skylight

Glass skylights are a component of buildings. As the span of buildings becomes larger, indoor lighting cannot be met through building curtain walls and windows. Glass skylights need to be set up on large-span roofs for indoor lighting. The innovative design combining photovoltaic glass components with skylights allows green building design to be integrated into the entire construction process.

Structurally, a horizontal hidden, vertical bright, semi-hidden frame design is adopted. For those with fire protection requirements, the fire protection requirements of building roofs must be met. For photovoltaic skylights without fire protection requirements, point-supported glass skylights and aluminum alloy frame glass skylights can be used.

Photovoltaic Skylight Node Diagram

 

3. Photovoltaic Railings

Railings are important protective components of building safety protection facilities. In locations with good orientation and sunlight, using photovoltaic glass instead of commonly used glass, metal, etc., can not only meet safety protection needs but also utilize solar power generation, achieving two goals with one action; innovative design combining photovoltaic glass with railings, structurally safe and reliable, perfectly hides lines and junction boxes for better aesthetics, and is simple and convenient for construction.

Photovoltaic Railing Node Diagram

 

4. Photovoltaic Awning

Photovoltaic awnings are one of the most promising future applications of building photovoltaics, with the following three points:

At a reasonable installation angle, it is conducive to the photovoltaic components receiving maximum solar radiation, improving the photoelectric conversion efficiency; it can block sunlight from entering the room, helping to control and adjust the indoor temperature, reducing the building's air conditioning load, and playing a role in energy saving and emission reduction; photovoltaic components, as a new type of building sunshade component, can save sunshade materials and enrich the building.

Photovoltaic Awning Node Diagram

 

03

BIPV Project Design Principles

The design of a building-integrated photovoltaic system mainly consists of the design of the photovoltaic system and the design of the building system.

The design of the photovoltaic system is based on the specific on-site conditions to match the electricity consumption requirements of the power consumption side. Based on the solar energy resources and temperature of the project location, calculate the appropriate solar panel array, match the corresponding equipment capacity, and achieve the overall economic rationality of the system.

The design of the building system is that, as part of the building structure, it needs to meet the requirements of use performance, and secondly, it needs to meet the requirements of structural stability, economy, and aesthetics.

 

1. Photovoltaic System Design Principles

The design process of a solar grid-connected power generation system mainly includes electrical, thermal, electrostatic shielding, and mechanical engineering, etc. The key process is to analyze the on-site environmental resource conditions, match the power demand, and balance the system.

The overall design principle of the system is to determine the most economical system combination on the premise of maximizing power generation.

Analyze electricity consumption demand, environmental resources, and main equipment selection; use professional simulation software for simulation and comparison and verification. The input data mainly includes:

Insolation at the installation location

Insolation of the inclined surface of the array

Ambient temperature parameters

System voltage

Load energy demand

Controller adjustment characteristics and parameters

Characteristic parameters of solar photovoltaic cells

System power supply reliability and power supply availability

Calculate the results parameters using computer simulation methods, mainly:

Tilt angle and azimuth of the solar cell array

Number of solar photovoltaic cells

 

2. Solar Power Generation System Design Steps

Step 1: List basic data

Geographic data mainly includes address, latitude and longitude, and altitude.

Local meteorological data: mainly includes the monthly average total solar radiation, direct and scattered radiation, annual average temperature and the highest and lowest temperatures, continuous rainy days, maximum wind speed and special climate conditions such as ice and snow. Generally, the accumulated meteorological data from the past 20 years is selected.

Step 2: Calculate daily radiation and array tilt angle

Meteorological stations generally only provide the total horizontal radiation, direct radiation, and scattered radiation. It is necessary to combine the project's tilt angle to convert it into solar radiation on the inclined surface.

Step 3: Estimate the solar cell array

Using the annual monthly average horizontal solar direct and scattered radiation, the monthly total radiation is calculated, and then the annual average daily total solar radiation and the power generation of the solar cell array are calculated.

Step 4: Determine the power capacity of the solar cell array

According to the current, voltage, and power data of the solar photovoltaic array, and referring to the performance parameters of the host equipment, select the appropriate equipment model and quantity.

 

3. Solar power generation system design steps - Design of building structure system

Building-integrated photovoltaic systems can be installed on the roofs of industrial plants to replace the original enclosure structure, adding power generation function to the factory roof. According to the different product structures, the mainstream products are divided into: building solar photovoltaic laminated glass, component type, water guide rack, and metal backplane type.

(1) Building solar photovoltaic laminated glass

 

 

Building solar photovoltaic laminated glass products integrate solar cells and one or more layers of glass. The structure consists of upper and lower glass layers encapsulating the solar cells, and a thermally fusible adhesive film connects the glass and solar cells. It is the smallest power generation unit that can independently provide DC output.

Specifically, it can be divided into two forms according to the combination method of solar cells and glass: laminated to a glass plate with interlayers and directly installed in the cavity of a multilayer glass unit.

The panel material uses double-layer glass. The glass model, size, and related parameters can be customized according to building requirements. It can be a composite of common tempered glass, ultra-white tempered glass, low-emissivity glass, colored glass, etc., and can also be combined into better-performing single-layer vacuum glass with interlayers.

The interlayer encapsulation material should use polyvinyl butyral (PVB), which is mainly composed of resin, plasticizer, and other materials. It has the characteristics of transparency, heat resistance, cold resistance, moisture resistance, and high mechanical strength, and has a service life of 50 years with the building.

 

(2) Integrated component type of crystalline silicon photovoltaic and pressed steel plate

 

The integrated component of crystalline silicon photovoltaic modules and roof pressed steel plates mainly includes crystalline silicon solar power generation components, pressed steel plates, and their connecting parts, referred to as component-type building-integrated photovoltaic systems. Structurally, it can be a complete whole and maintain structural connection characteristics when subjected to external loads, and can be used as the smallest independent power unit.

The core photovoltaic roof of this system is mainly composed of purlins, insulation cotton, waterproof breathable membrane, sliding support, pressed steel plate, and photovoltaic components from top to bottom, compatible with the hidden purlin type and exposed purlin type insulation systems and installation methods of conventional industrial plants.

The photovoltaic component uses 2mm tempered glass, front EVA film, high-efficiency monocrystalline Perc cell, polyolefin elastomer encapsulating insulating film (POE), and tempered glass.

At the same time, the component supporting structure changes from the traditional four-point support to a strip support with a span of 30cm, making the component stress more balanced, greatly reducing component hidden cracks caused by external forces during use, and achieving a reliable guarantee of system power generation.

The metal roof system uses 0.6mm thick galvanized aluminum-zinc steel plate with a full-length type, that is, the entire steel plate is used from the ridge to the eaves without overlapping, which effectively reduces the risk of leakage caused by overlapping seams. The longitudinal overlapping of the pressed steel plate adopts 360-degree vertical locking technology, ensuring reliable and leak-proof connection between steel plates; in addition, the locking gap is also filled with butyl rubber, which can effectively prevent seepage caused by capillary phenomenon.

 

(3) Water guide bracket type

The water guide bracket building-integrated photovoltaic system mainly includes horizontal and vertical water channels, conventional solar modules, fixed pressure blocks, rubber strips, and edges, meeting the basic requirements of building water seepage prevention, subsidence resistance, and expansion and contraction resistance. At the same time, it can resist high wind loads, snow loads, has good lighting performance, good ventilation performance, insulation, heat insulation, and waterproof, and is relatively easy to maintain in the later operation and maintenance stage.

The roof drainage function mainly relies on the natural drainage of the component surface. A small amount of water flows to the drain under the pressure difference, and then is discharged through the vertically intersecting drain channels of the horizontal U-shaped waterproof channel and the vertical W-shaped drain channel. The short side where the component is in contact horizontally is fixed with a pressure block, and the long side where the component is in contact longitudinally is fixed with a T-shaped rubber strip. The drain channel can also serve as a function of fixing the solar module.

 

(4) Metal backplane type

The metal backplane building-integrated photovoltaic system uses a galvanized aluminum alloy backplane as the solar module backplane to form a latch structure, replacing or covering the roof installation method.

Among them, the front of the solar module uses tempered glass with a 3600Pa front static load, and the middle composite photovoltaic power generation layer constitutes a non-combustible composite material structure with external dimensions of 2100*1400mm.

As shown above, the current building-integrated photovoltaic systems applicable to industrial plant roofs are mainly divided into four categories: building solar photovoltaic laminated glass, integrated component type, water guide bracket, and metal backplane type. With technological progress, there are completed cases of various products for research.

 

04

BIPV Investment Return Analysis

1. Investment payback period and rate of return

A simple model is constructed and calculated for the investment economics of typical industrial and commercial BAPV/BIPV photovoltaic roofs. It is assumed that the investor and electricity user of the photovoltaic roof are the same entity, and all photovoltaic power generation is for self-use.

Due to the gaps between photovoltaic components in the actual installation of BAPV, the actual effective power generation area will be lower than that of BIPV under the same conditions. We assume that the actual effective power generation area ratio of BIPV is 95%, and that of BAPV is 85%.

The project construction period is 0.25 years, and the operation period is 25 years; the power generation efficiency of photovoltaic components decreases by 5% in the first five years, and then linearly decreases at a rate of 0.5%/year, with a total decrease of 14% in 25 years; in terms of subsequent maintenance costs, BAPV is 0.06 yuan/watt·year, and BIPV is 0.04 yuan/watt·year. In addition, the BAPV project needs to replace the color-coated steel roof once after 15 years of operation, with the cost calculated at 300 yuan/㎡; in terms of electricity Price, the average industrial electricity Price of 0.73 yuan/kWh is used.

Assuming the installation of a 2000㎡ photovoltaic roof, the estimated power generation in the first year after completion is 298,000 kWh for BAPV and 380,000 kWh for BIPV.

If the owner initially chooses to invest entirely with its own funds, the estimated payback period for the BAPV project is 5.87 years, and IRR=15.25%; the estimated payback period for the BIPV project is 5.87 years, and IRR=16.36%; if the owner chooses loan investment, with an annual interest rate of 6% and a loan term of 5 years, the estimated payback period for the BAPV project is 7.32 years, and IRR=34.02%; the estimated payback period for the BIPV project is 7.31 years, and IRR=35.33.

 

2. Impact of Excess Power Grid-Connection Ratio on Investment Returns

If the owner cannot consume all the power generation, or if the photovoltaic investor and the building owner are not the same entity, part or all of the project's power generation needs to be grid-connected and sold. Because the current Price for selling excess photovoltaic power to the grid is generally lower than the industrial electricity Price, the higher the proportion of excess power grid-connection, the lower the return rate of the rooftop photovoltaic project.

Assuming that the after-tax Price of excess photovoltaic power grid-connection is 0.42 yuan/kWh, if the excess power grid-connection ratio is 20%, the payback period of photovoltaic projects with self-owned funds will be extended to 6-7 years; the payback period of photovoltaic projects with loan investment will be extended to about 8 years. If the photovoltaic investor is not the building owner, and chooses to sell all the power generation to the grid, the payback period for self-funded investment in BIPV is about 10 years, and the payback period for loan investment in BIPV projects exceeds 13 years.

 

In other words, the higher the proportion of self-use power generation in industrial and commercial building photovoltaic projects, the better the investment returns.

According to the current energy consumption of industrial and commercial buildings in China, the power generation of building photovoltaic projects is not enough to cover the electricity consumption of the building itself. Taking a typical four-story commercial building in China as an example, with a floor area of 34,300㎡, the monthly electricity consumption is about 1.61 million kWh. If the roof is renovated with BIPV photovoltaic, the estimated monthly power generation is only about 480,000 kWh.

Therefore, the power generation of building photovoltaics can basically be consumed by the building itself, and there is no need to sell it to the grid. It is expected that most building photovoltaic projects will be mainly for self-use in the short term.

 

3. Impact of Sunshine Duration on Investment Returns of BIPV Projects

The annual average effective sunshine duration of the photovoltaic project location will directly determine the amount of photovoltaic power generation, which is an important factor affecting the return of photovoltaic roofs. In China, the regions with the longest annual average effective sunshine duration, Xinjiang and Tibet, have an effective duration of more than 1600 hours, while the shortest, Chongqing, has only about 700 hours.

Taking the BIPV project as an example, assuming that the local annual average effective sunshine duration is 800 hours, the payback period for self-funded investment is 7.49 years, and the payback period for loan investment is 9.35 years. If the annual average effective sunshine duration is 1300 hours, the payback period for self-funded investment is 4.42 years, and the payback period for loan investment is 5.51 years.

 

 

4. Impact of Construction Cost on Investment Returns of BIPV Projects

In 2021, the average winning Price of distributed photovoltaic EPC projects in China was around 4 yuan/watt, with the highest winning Price in 2021Q4 being 4.75 yuan/W and the lowest Price being 3.32 yuan/W. From some rooftop distributed photovoltaic projects in February 2022, the unit Price is between 3.42 and 4.95 yuan/W.

If the average Price of building photovoltaics in China further drops to 3 yuan/W in 2025, assuming that the future industrial and commercial electricity Price in China remains unchanged, then by 2025, the payback period for self-funded investment in BIPV photovoltaic roof projects can be reduced to 4.67 years, and the internal rate of return is expected to reach more than 20%; the payback period for loan investment in BIPV photovoltaic roof projects is expected to be 5.82 years, and the internal rate of return exceeds 60%.