BIPV Power Generation and Comprehensive Benefits

What factors affect the power generation of BIPV systems? The power generation of BIPV systems is affected by many factors, among which solar radiation and shadow shielding are the main factors.

Solar irradiance: The core factor that directly affects the power generation of BIPV systems. Its influence is mainly reflected in two aspects: (1) Installation orientation: Taking the northern hemisphere as an example, the south is the best installation orientation, which can maximize the reception of direct sunlight. Southeast and southwest have moderate efficiency and are suitable for capturing sunlight in the morning or afternoon to optimize time-sharing power generation. The power generation in the east and west is slightly lower. (2) Tilt angle: The optimal tilt angle is usually related to the local latitude, so that the product surface is as perpendicular to the sunlight as possible at noon. Generally speaking, the higher the latitude, the larger the optimal tilt angle. When deviating from the optimal tilt angle, the power generation will gradually decrease.

Shadow shielding: When the BIPV product is blocked by shadows, the blocked cells will not only fail to generate electricity, but their resistance will increase sharply, consuming the energy generated by other normal power generation cells and converting it into heat energy, forming a "hot spot effect". Hot spots can permanently damage solar cells. Shading has a nonlinear and significant impact on the energy yield of a BIPV system.

What are the differences in energy yield between BIPV facades and rooftops?

The energy yield of different building installation surfaces varies. Rooftops, as the location receiving the most solar radiation, are ideally positioned for optimal installation angles to maximize energy yield. Vertical facades, on the other hand, primarily receive diffuse radiation and direct radiation at wide angles, resulting in significantly lower solar radiation per unit area than rooftops. Given the same area and technical configuration, the annual energy yield of a BIPV facade system is roughly 50%-70% of that of a rooftop system. In crowded urban spaces, BIPV facade systems are becoming an effective energy supplement and are becoming an increasingly popular choice.

How to estimate the annual energy yield of a BIPV system?

To estimate the annual energy yield of a BIPV system, you need to consider the installed capacity, the local average annual sunshine hours, and the overall system efficiency. This can be estimated using the following formula: Annual energy yield = installed capacity x average annual sunshine hours x overall system efficiency. For example, suppose a region has an average annual sunshine duration of 1,179 hours. A BIPV project is installed on a building roof with a capacity of 100 kW. The overall system efficiency is generally assumed to be 80%. Therefore, the annual power generation = 100 kW * 1,179 hours * 80% = 94,320 kWh.

When estimating actual power generation, factors such as shading and temperature must also be considered.

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