Solar panels perform best in direct sunlight, but in practice things are rarely that simple. Trees, roof structures, chimneys, neighbouring buildings: on virtually every commercial roof, there are obstacles that cast shadows at certain times of the day. The question that project developers and installers then ask is understandable: will it work? solar panels in the shade still, and if so, how efficient are they now? The answer is nuanced and depends on several factors, ranging from the nature of the shade to the technology within the panel itself.
For large-scale rooftop installations on commercial premises, logistics centres and industrial buildings, this is not merely a theoretical issue. Shading can have a direct impact on a system’s energy yield and, consequently, on the financial viability of a project. Understanding how solar panels perform in the shade enables better decisions to be made regarding system design, component selection and project planning.
Shade reduces the amount of light reaching a solar panel, meaning fewer photons are converted into electrical energy. Even diffuse light, such as on a cloudy day, contains sufficient radiation for a panel to generate electricity, but the output is then considerably lower than in direct sunlight. In the case of direct shade cast by an obstacle, the effect is even stronger and more complex.
What makes traditional PV modules unique is that the cells are connected in series. This means that a single shaded cell can limit the current flowing through the entire string, much like a burnt-out bulb in a series circuit of Christmas lights. The shaded cell acts as a resistor and can even generate heat, a phenomenon known as the hotspot effect. This can cause damage to the panel over time and is one of the reasons why shading management is so important when designing a system.
Not all shade is the same. The distinction between partial and full shade is crucial to understanding the efficiency of solar panels in the shade. Full shading, where a panel is completely covered, results in that specific panel producing virtually no output. Partial shading, where only part of the panel or part of the installation is affected, has a more complex effect.
In the event of partial shading on a traditional system without optimisers or micro-inverters, the loss of a single panel can drastically reduce the output of an entire string. In practice, this means that a small obstacle, such as a chimney casting a shadow over two panels early in the morning, can have a disproportionately large effect on the total system output. Modern systems are designed to limit this cascade effect, but the basic principle remains relevant in any project planning.
The sector has made significant progress in recent years in minimising shading losses. Three technologies play a key role in this.
Most modern PV modules are fitted with bypass diodes, which electrically bypass shaded cells so that the rest of the panel continues to generate power. This prevents the worst effects of the hotspot effect and limits the loss to the shaded area. It is a basic solution found in virtually every high-quality panel.
Micro-inverters and DC optimisers take this a step further. Whereas a traditional string inverter uses the weakest panel as a reference, these technologies enable each panel to operate at its own maximum power point. At partial shading on PV modules This can significantly increase the yield, as the performance of a single panel no longer limits the entire installation. These are valuable solutions for complex roof geometries or roofs with multiple orientations.
Newer panel designs, such as half-cell and shingled modules, divide the cell into smaller units that are less susceptible to partial shading. By spreading the electrical impact of shading across a larger number of smaller cells, the total output remains more stable when only part of the panel is affected.
A thorough shadow analysis is not an optional step, but an essential part of any serious PV project. Using specialised software, installers and project developers can simulate the shadow patterns on a roof for every hour of the year, taking into account the position of the sun, the height of obstacles and the orientation of the roof.
Based on this analysis, well-informed decisions can be made regarding the positioning of panels, the layout of strings and the choice of inverter technology. An obstacle that casts hardly any shade in summer may, due to the low angle of the sun in winter, cast a shadow over a much larger part of the roof. Anyone who fails to take this into account in their planning risks ending up with a system that consistently underperforms relative to its expected capacity.
For its commercial panels, Solarge provides an estimate based on the specific conditions at a site, including orientation and shading, so that project partners can gain a realistic picture of the expected energy yield. This makes the shading analysis an integral part of the consultancy process, rather than an afterthought.
Shade loss has a direct financial impact. A system that consistently produces less than expected generates lower energy yields and therefore has a longer payback period. For large-scale commercial projects, where the financial business case has been carefully calculated, this can make a significant difference.
It is therefore advisable, when calculating the payback period, not to base the calculation on the theoretical peak output, but on a realistic production estimate that takes into account local shading patterns, seasonal variations and system losses. A conservative but accurate estimate provides greater certainty than an optimistic projection that cannot be achieved in practice.
At the same time, a thorough shading analysis also presents opportunities. By positioning panels strategically and selecting the right technology, shading losses can be significantly reduced, enabling a system to perform closer to its theoretical maximum. Combined with lightweight panels that can be installed over a larger proportion of the roof surface – including sections that would be unable to support the weight of conventional glass modules – this results in a system that maximises both the yield and the durability of the available roof space.
This content was generated with the help of AI and it may contain mistakes
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