When it comes to the conditions of use of solar energy systems, we often focus on the efficiency of their power generation at different mounting angles. The orientation and tilt angle of the solar panels have a significant impact on the energy yield. Let’s take 35°~40° north latitude as an example:
South Facade Installation: If solar panels are installed on the south facade of a building, there may be a loss of up to 30% of power production compared to an optimal tilt angle installation.
Installation facing east or west: If the solar panels are installed facing east or west, there may be a loss of up to 20% of power generation compared to the optimal tilt angle.
Installation facing east or west: If the solar panels are installed inside the east or west façade of a building, there may be up to a 50% loss of power generation relative to the optimal tilt angle.
So does the actual usage match the description above? Sungold Solar installed 2 solar systems in January 2023 for balcony and rooftop solar system data analysis with the following basic conditions.
Location Information
Project Location: Shenzhen, China
Location: Latitude 22.55 °N
Longitude: 114.10 °E
Altitude: 18 m
Time zone: UTC+8
Photovoltaic modules and connections
Photovoltaic modules: 8 SUNPOWER solar panels of 135 W are used
Series connection: 4 series, 2 parallel
Installation
System 1 (wall system): Solar panels are mounted vertically, facing south.
System 2 (Roof system): Solar panels are mounted horizontally.
Solar Inverter and Controller
Inverter & Controller: 3KW Grid-Tie Inverter
Battery: 800AH lithium iron phosphate battery. Specification is 12.8V, each battery capacity is 200AH, there are 4 batteries.
According to the meteorological industry standard of the People’s Republic of China, QX/T89-2008, “Solar Resource Assessment Method”, taking the total annual solar radiation as an indicator, the solar resource richness level is relatively rich.
Sungold Solar observed the two systems for a period of 10 months.
After 10 months of observation, we obtained the following data to compare the performance of two solar systems with identical configurations but different orientations:
Monthly power generation from two solar systems
Month | Level（kwH） | Vertical（kwH） |
January | 48.5856 | 34.00992 |
February | 52.8 | 35.904 |
March | 48.3588 | 31.43322 |
April | 40.5174 | 24.31044 |
May | 57.8754 | 33.567732 |
June | 37.9236 | 20.099508 |
July | 69.5992 | 34.7996 |
August | 53.5394 | 29.982064 |
September | 46.8874 | 28.13244 |
October | 75.64 | 47.6532 |
Total | 531.7268 | 319.892124 |
Weather conditions
Month | January | February | March | April | May | June | July | August | September | October |
Rainy | 3 | 1 | 8 | 12 | 15 | 20 | 15 | 17 | 18 | 8 |
Cloudy | 20 | 19 | 19 | 18 | 14 | 9 | 13 | 9 | 8 | 13 |
Sunny | 3 | 8 | 4 | 0 | 3 | 0 | 3 | 1 | 4 | 7 |
Cloudy | 4 |
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| 3 |
Fog | 1 |
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After analyzing the data from the different installation angles of the solar systems, there is a significant difference in the amount of power generated by the solar panels laid horizontally compared to vertically in this area of Shenzhen, China.
Power Generation Comparison
The power generation of the horizontally mounted solar system reached 531.72 kWh in 10 months of a year, compared to 319.89 kWh for the vertically mounted system, which is 39.8% higher than the power generation of the horizontally mounted system. This shows that horizontal installation is more efficient in Shenzhen.
Monthly Power Generation Change
Through the graph, we can learn that in Shenzhen, the annual average of solar panel power generation is relatively balanced, with only a few months having large variations.
The maximum value of the monthly average power generation of both installation types is in October, and the minimum value is in June.
The poor performance in June may be related to the weather in the region during that month, where the prolonged rainy season resulted in insufficient power generation.
In the other months, especially October, the power generation of both installation types exceeded the yearly average, accounting for more than 65% of the total, making it a prime period for solar panels to generate power.
Optimal Operation Period
In order to ensure the normal operation of solar panels, you need to focus on the operation during the golden period, and do a good job of repairing and maintaining solar panels in April and June.
Effect of azimuth on power generation
At the same location, changes in facing east and west have the same effect on power generation. As the azimuth angle gradually increases from 0°, the loss of power generation accelerates, showing a parabolic trend.
Influence of region on power generation
Differences in latitude and longitude in different regions lead to significantly different changes in power generation. At high latitudes, installations facing east and west may result in more than 20% loss of power generation, while at low latitudes, the loss is only 4%.
Relationship between latitude and power generation
Latitude has a greater effect on power generation losses, while longitude has a lesser effect.
It is also evident from the data that the lower the latitude, the lower the loss of power generation when laid flat;
Whereas, the higher the latitude, the lesser the power generation loss when vertical.
Radiation difference: parabolic distribution
The difference between the radiation on the inclined plane at different angles and the maximum value has a parabolic shape.
That is, the difference is not uniformly distributed, but near the maximum value, the difference is very small;
The farther away from the maximum value, the difference increases rapidly.
Thus, near the maximum value, the difference in radiation is very small.
Conclusion
1. The power generation capacity of vertically mounted solar panels is much higher than one would expect, and is sufficient to support the normal operation of a system.
From this point of view, the existence of balcony systems, roof systems and other scenarios is very meaningful.
2. The market for BIPV applications is vast: BIPV systems do not require additional land area because they replace traditional building materials, fully utilize the space on the outside surface of the building, and allow more building types to use solar power.
