5.10.2017

foto Petr Bravenec

Petr Bravenec
+420 777 566 384
petr.bravenec@hobrasoft.cz

Summary

This article analyzes the impact of mounting inaccuracies on power plant production and on monitoring system. Mounting inaccuracies can lead to performance drops, to unexplained monitoring alarms and to ignoring real problems. Without a detailed analysis of the power plant, it is not possible to distinguish between the operational characteristics of the power plant and the actual faults.

Introduction

Rotation of panels to the east or west is one of the typical characteristics which the artificial intelligence in the application »Artificial Intelligence Photovoltaic analyzer« can recognize.

The photovoltaic panel rotation cannot be marked as a defect really. It is difficult to imagine that someone on the finished power plant would fix the panels a few degrees just because a computer application advised so. The panels will remain rotated over the entire life of the power plant and the only question is the impact of the rotated panels on the power plant operation.

I thought that the effect of the rotation is only small – the panel produces in one half of the day less power, while in the other half of the day the panel produces more power. Rotation should be compensated and no significant effect on the production should be visible. But I did not have any evidence so I made a small program that numerically calculates the production of the power plant at different days of the year with various panel tilt and azimuth.

Will the panel rotation affect the performance significantly? To understand what effect the azimuth and tilt of the pannels have on the power it is needed to explain the problem in more wide context.

The following simulations are based only on ideal geometric condition (no shading) and the ideal influence of the atmosphere (no clouds). Real situation on the actual power plant can vary greatly. The weather has topic effect on the photovoltaic power plant operation. The weather has a strong statistical character during the year. Due to the expected weather the actual power plant design differs from design derived from ideal geometric contidion (the tilt of panels is usually lower).

How to set photovoltaic panels to make the most of it

To get the most out of the photovoltaic panel throughout the year, it is best to set the panel straight south with a 30° tilt in Central Europe conditions. What will happen if the PV panel is installed with a different slope or azimuth is shown in the following chart. Optimum is around 45° tilt at facing south. In practice, the panels are tilted less to compensate impact of different weather conditions in summer and winter. Both pictures are the same graph, once in flat view and once in 3D view.

How to set photovoltaic panels to make the most of it in winter

The common idea that the sun rises in the east and sets in the west is not right in the winter. The sun rise and set are moved to the south a lot. The chart of optimal photovoltaic panel settings looks different for the shortest day of the year.

How to set photovoltaic panels to make the most of it in summer

The common idea that the sun rises in the east and sets in the west does not even apply in the summer. The sun rise and set are moved to the north a lot. Because panels are usualy facing south, the sun rises behind the panels and it shines to the back side of the panels. In the morning end evening the photovoltaic plant produces power from the diffused light only. While the winter chart looked predictable, the chart for the longest day of the year hides a surprise in the form of two maximums. At the usual tilt is is better to rotate the panel to the east or west in the summer. When facing south, the photovoltaic panel will earn less:

Optimal panel settings throughout the year

If you would want to set the panel optimaly before dawn to make the most of every day, you could follow the following animation. There are 365 charts in the video showing the optimal setting of the photovoltaic panels throughout the year.

Effect of panel rotation on performance

Now you should know the clear answer what is the effect of inaccurate PV panel settings. It is obvious from the simulations that the panel rotated by several degrees has virtualy no impact on the power plan power. There is no need to deal with the fault. In the summer, deviation from the south even lead to a light increase in daily production.

Effect of panel rotation on monitoring system

Huge impact is possible on monitoring system. Panel rotated east will show above-average performace in the morning. In the afternoon, however, performance drops to below average. If the monitoring system is too sensitive, the false alarms is triggered. Panel rotated to east is in the opposite situation – false alarms is triggered in the evening. If the monitoring system should be sensitive to even a low power reduction without false alarms, the entire system must be set carefuly to ignore the impact of panel rotation.

The screenshot of »Artificial Intelligence Photovoltaic analyser« shows the east rotated panel compared to entire power plant. In the morning the performance is below average. The marked area in the picture shows the time, when the false alarms are possible. If the monitoring system operator missed the information about the real cause of the alarm, the unexplained alarm is ignored. In the worst case it may lead to ignoring the actual faults on the photovoltaic power plant.

Conlusion

Some defects of PV power plants are insignificant in theory. Inaccurate rotation of photovoltaic panels is one of such defects. But such defect, however, cat trigger false alarms in monitoring system. If you do not know the exact reason of the fault, such fault remained unexplained and false alarms are ignored. If you do not have an exact explanation for common phenomena at your photovoltaic power plant, you may not be able to recognize between the actual defects and the operational characteristics. As a result, it can lead to ignoring actual failures of the photovoltaic power plant.

 
 
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