Know your solar module: Are clouds and shades still a threat to your energy generation?

Solar photovoltaic (PV) panels use sunlight to generate green energy. So what do solar panels do at night? They sleep, just like us. No sun, no energy generation – that’s a straightforward equation. But what happens to the solar panels when the sky is cloudy or they are covered in shade? Do they stop generating power like at night? Nope, they sure don’t!

Although clouds and shade do impact solar energy generation, they still allow significant energy generation. Let us look at cloudy skies first, and then we will come back and see how solar PV modules handle shading issues.

40 MW Ilfs solar power plant at Kachaliya Madhya Pradesh
40 MW Ilfs solar power plant at Kachaliya Madhya Pradesh

Clearing the clouds

Even on the cloudiest of days, 10% to 25% of the maximum energy can still be generated by solar panels. Just look at countries like Germany, USA, and the United Kingdom, that lack ideal year-round sun exposure (in many areas), yet have become global leaders in installed solar capacity per capita.

Within 2015, Germany was able to generate more than 7.5% of its national net electricity consumption requirements with 1.5 million solar installations. America’s cloudiest cities are currently producing considerable solar power, and even the United Kingdom has managed to cross a milestone when its solar installation produced more electricity than the nation’s thermal plants. These countries are proof that solar is not just ideal for the sun-kissed areas, but for ‘not so sunny’ areas as well.

But how?

To get answers to that question, you need to understand the overall economics of a solar power system. If you start looking at the day-by-day energy generation of PV modules in cloudy environments, you might not see the bigger picture of annual energy generation. So how does annual energy output fill the gaps of low energy generation on cloudy days? Well, sunlight exposure ratios change several times a year, and in summer months when sun exposure increases, your PV system will generate more energy than the winter months, ultimately, making up for the shortfall.

Another interesting quirk of solar PV modules is that they perform better at lower temperatures. So on cooler days, they run at a higher efficiency, partially offsetting the reduced sunlight. Too much heat actually reduces power output in and is sometimes the reason behind energy loss in a solar array. So cloudy weather will ensure there is no energy loss due to overheating. And finally, if you still have issues with varying power outputs across different days and times of day, you can simply add a storage system to your solar plant to flatten out the generation profile, and get electricity regardless of the weather.

Changes are on the way

Solar panels are already being manufactured with PERC, n-type, bifacial cells to maximise energy generation (with up to 17% module efficiency). By using these more efficient PV modules, consumers can easily generate more energy than previously possible, even in the cloudiest of environments. Solar trackers are also available, which turn the module to face the sun over the course of the day. This ensures maximum energy yield over the course of the day even in cloudy environments by tracking the sun constantly.

Now that we are clear on module efficiency in cloudy environments, let us look at the issue of shading.

750 kW rooftop solar plant at Calicut international airport, Calicut, Kerala, India
750 kW rooftop solar plant at Calicut international airport, Calicut, Kerala, India

Mitigating the shading issue

Shading used to be quite a challenge for solar plant developers to handle. Even after installing PV modules at the best angle to capture the most sunrays, even partial shading could reduce power generation. How?

Well, each solar panel is made up of multiple solar cells, each connected in a series. They catch the sun’s rays and transfer the energy through the interconnected cells to either be consumed on-site, or sent to the storage system or grid. So if one of the cell falls under shade, it results in considerable energy loss or even panel shut down because the voltage across the whole module drops. A similar issue occurs with modules connected in series across a string – if one of the modules is shaded, the voltage across the entire string drops.

However, microinverters and power optimizers are available now to help PV modules work, even when one of them is under shade. Furthermore, newer PV modules have bypass diodes, which allow electricity to ‘flow around’ the shaded cell or cells. So, shading is not nearly the issue it once was, and with further technologies being developed, we are sure to see an even brighter future with solar panels on your roof.

Embrace the future today!

Psssst…Do you feel ahead of your time? Solar plant users sure do. Solar development is on the rise, so learn about your PV modules and how they can transform your life and your relationship to energy. You too can utilise renewable energy and become a greener and more responsible citizen. Join us in the energy transformation by getting in touch via our contact form.

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