The Power Generation is actually 15% less, If the solar energy system is installed in this way.

Foreword

If a house has a concrete roof, it faces east to west or west to east. Are the solar panels arranged facing south, or according to the house orientation?

The arrangement according to the orientation of the house is definitely more beautiful, but there is a certain difference in the power generation from the south-facing arrangement. How much is the specific power generation difference? We analyze and answer this question.

Project Overview

Taking Jinan City, Shandong Province as a reference, the annual radiation amount is 1338.5kWh/m²

Take a household cement roof as an example, the roof sits west to east, a total of 48pcs of 450Wp photovoltaic modules can be installed, with a total capacity of 21.6kWp, using a GoodWe GW20KT-DT inverter, the pv modules are installed south, and the inclination angle is 30°, as shown in the figure below. The difference in power generation at 30°/45°/60°/90° south by east and 30°/45°/60°/90° south by west is simulated respectively.

Azimuth and Irradiance

The azimuth angle refers to the angle between the orientation of the photovoltaic array and the due south direction (regardless of the magnetic declination). Different azimuth angles correspond to different total amounts of radiation received. Usually, the solar panel array is oriented towards the orientation with the longest exposure time. angle as the best azimuth.

With a fixed inclination angle and different azimuth angles, the annual cumulative solar radiation of the power station.

Conclusion：

With the increase of azimuth angle, the irradiance decreases linearly, and the irradiance in due south is the largest.

In the case of the same azimuth angle between south-west and south-east, there is little difference in the irradiance value.

Azimuth and inter-array shadows

（1）Due south spacing design

The general principle for determining the spacing of the array is that the photovoltaic array should not be blocked during the time period from 9:00 am to 15:00 pm on the winter solstice. Calculated according to the following formula, the vertical distance between the distance between the photovoltaic array or the possible shelter and the bottom edge of the array should not be less than D.

Calculated D≥5 m

（2）Array shading loss at different azimuths (taking south by east as an example)

At 30° east by south, it is calculated that the shadow occlusion loss of the front and rear rows of the system on the winter solstice is 1.8%.

At 45° east by south, it is calculated that the shadow occlusion loss of the front and rear rows of the system on the winter solstice is 2.4%.

At 60° east by south, it is calculated that the shadow occlusion loss of the front and rear rows of the system on the winter solstice is 2.5%.

At 90° east by south, it is calculated that the shadow occlusion loss of the front and rear rows of the system on the winter solstice is 1.2%.

Simultaneously simulating four angles from south to west obtains the following graph：

Conclusion：

The shading loss of the front and rear arrays does not show a linear relationship with the azimuth angle. When the azimuth angle reaches an angle of 60°, the shading loss of the front and rear arrays decreases.

Power generation simulation comparison

Calculated according to the installed capacity of 21.6kW, using 48 pieces of 450W modules, string 16pcsx3, using 20kW inverter

The simulation is calculated using PVsyst, the variable is only the azimuth angle, the rest remain unchanged：

Conclusion：

As the azimuth angle increases, the power generation decreases, and the power generation at 0 degrees (due south) is the largest.
In the case of the same azimuth angle between south-west and south-east, there is little difference in the value of power generation.
Consistent with the trend of irradiance value

Conclusion

In reality, assuming that the azimuth of the house does not meet the south orientation, how to balance the power generation and the aesthetics of the combination of the power station and the house needs to be designed according to its own needs.