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    Cloudy with a Chance of Power: How do Photovoltaics also work without the sun

    • 7 min read

    Harnessing the power of the sun, solar panels stand as beacons of renewable energy innovation. But what happens when the sun takes a brief hiatus behind the clouds? Contrary to common belief, photovoltaics also work without the sun's direct embrace, capturing solar energy even on the cloudiest of days. In this article, we'll delve into the fascinating mechanics of solar panels, exploring their ability to collect solar energy amidst varying weather conditions. We'll also unravel the process of calculating photovoltaic power generation during overcast weather, shedding light on the enduring value of PV systems regardless of the skies above.

    How Does a Solar Panel Collect Solar Energy from Sunlight?

    Solar panels, those gleaming symbols of renewable energy, have a fascinating way of capturing sunlight and turning it into electricity. At the heart of each panel is a collection of solar cells, typically made from silicon, a material known for its semiconductor properties. When sunlight hits these cells, it sets electrons in motion, creating a flow of electric current.

    This process, known as the photovoltaic effect, is the magic behind solar energy conversion. The solar cells contain a positive and a negative layer, which together create an electric field, much like in a battery. As sunlight energizes the electrons, they are pushed from the silicon and move towards the electric field, creating a flow of electricity.

    Interestingly, the efficiency of this process isn't just about the amount of sunlight; it's also about the quality of the solar cells and the technology behind them. Advances in technology have made these cells more efficient, allowing them to convert more sunlight into electricity, even on cloudy days.

    So, in a nutshell, solar panels work by employing a smart mix of physics and technology to harness the sun's power. It's a clean, green way to generate electricity, reducing our reliance on fossil fuels and making a positive impact on our planet.

    Will Solar Panels Still Work in Cloudy Days?

    Absolutely! The idea that solar panels only function under the blazing sun is a common misconception. In reality, a PV system in cloudy conditions can still harness the power of the sun, albeit at reduced efficiency. Clouds do not block sunlight entirely; they diffuse it. This scattered light still contains photons that your solar panels can convert into electricity.

    Moreover, it's crucial to debunk the myth that solar works even without the sun. On overcast days, solar panels can generate about 10% to 25% of their rated capacity. The exact amount varies depending on the thickness of the clouds and the type of solar panel. Interestingly, certain types of panels, like those that utilize thin-film technology, can perform relatively better in diffused light conditions.

    This resilience of solar panels to cloudy weather underscores the viability of solar energy in various climates, not just those that are sunny year-round. So, even during those gloomy days, your solar panels are quietly at work, contributing to a greener planet. This adaptability makes solar energy an increasingly appealing option for sustainable power generation across the globe.

    Calculating Photovoltaic Power Generation in Cloudy Weather

    Photovoltaic (PV) panels stand as a primary method for converting sunlight directly into electricity. However, the efficiency of this conversion can be significantly affected by weather conditions, especially cloud cover. Understanding how cloudy weather influences PV power generation is crucial for both optimizing energy yield and managing expectations. Let's delve into the nuances of calculating PV power generation on those overcast days, armed with a bit of math and a dash of optimism.

    1. The Impact of Clouds on Solar Irradiance

    First and foremost, it's essential to understand that clouds don't completely block solar radiation; they merely diffuse and reduce it. Solar irradiance, the power per unit area received from the Sun, is the lifeblood of PV panels. On a clear day, the Earth's surface can receive about 1000 watts per square meter (W/m²) of solar energy, known as the Standard Test Condition (STC). However, cloudy weather can reduce this figure to as little as 100 W/m² or even lower, depending on the thickness and density of the cloud cover.

    1. The Calculus of Cloudy Skies

    To estimate PV power generation under cloudy conditions, we can use a simplified formula:


    η is the efficiency of the PV panel (expressed as a decimal).

    This formula adjusts the rated power output of the panel based on the ratio of actual solar irradiance under cloudy conditions to the ideal STC irradiance, taking into account the panel's efficiency.

    1. A Real-World Example

    Imagine a 300-watt panel with an efficiency of 20% on a day where the solar irradiance is about 200 W/m² due to cloud cover. The power output can be estimated as:

    By crunching the numbers, we find that the panel's output drops to around 12 watts. While this is a significant decrease from its peak potential, it highlights the importance of accounting for environmental factors in energy planning and the resilience of PV systems to still produce power under less-than-ideal conditions.

    Despite the panel's output dipping to 12W, we can bolster this by enhancing the efficiency of PV panels. While the average efficiency of PV panels on the market hovers around 20%, the Anker SOLIX balcony power plant boasts a PV efficiency of up to 25%. This leap in efficiency not only promises higher output but also underscores the potential for significant savings and sustained performance over the long term.

    Embracing Variability with a Grain of Optimism

    While the decrease in power output on cloudy days can be substantial, it's essential to remember that PV systems are designed with such variability in mind. Balcony power plants with storage options exemplify this adaptability, capturing and storing energy for use during less sunny periods, ensuring a consistent power supply despite weather fluctuations. 

    The Anker SOLIX balcony power plant with storage, equipped with a robust 890W PV system and a substantial 1600Wh storage capacity, shines even under the often-overlooked cloudy weather conditions. Designed to optimize energy capture with flexible angle and location options, this system ensures that even on overcast days, your power generation doesn't come to a standstill. Its Plug&Play setup, manageable within a mere 2 hours, along with real-time data monitoring through the Anker App, makes it a user-friendly yet powerful ally in your energy-saving endeavors. Moreover, with a battery that boasts 6,000 charging cycles, the Anker SOLIX promises long-term savings, potentially cutting down electricity costs by up to €9612 over 30 years, making it a prudent choice for eco-conscious urban dwellers.

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    What’s the Point of a PV System When It’s Cloudy?

    When the skies turn grey and the sun plays hide-and-seek behind the clouds, is it all gloom for solar energy on such days? What's the point of a PV system when it's cloudy? It is important to recognize that the utility of PV systems extends far beyond the brightest days, offering numerous advantages for home use even when overcast skies prevail.

    First and foremost, a key benefit of PV system in cloudy conditions is their ability to contribute to significant energy savings. Even on cloudy days, solar panels continue to collect and convert available light into electricity. While it’s true that solar panels are most efficient under direct sunlight, they don’t cease to function in overcast conditions.

    They can still harness diffused sunlight, transforming it into usable energy. This means that every kilowatt-hour of electricity generated by your solar panels is one less kilowatt-hour that needs to be purchased from your local energy provider. Over time, these savings can add up, offsetting the initial cost of the PV system and contributing to household or business finances.

    Moreover, the ability of PV systems which charges a solar panel even without the sun plays a crucial role in reducing reliance on the electrical grid. This is particularly beneficial during peak energy usage times when electricity prices can soar.

    By providing a steady, albeit reduced, supply of electricity from your rooftop, solar panels can help mitigate the impact of peak pricing and reduce your overall electricity bills. Continuing to generate power during cloudy conditions also ensures a more consistent contribution to your home’s energy needs.

    While the energy produced may be less than on sunny days, it remains a valuable supplement that can power various household appliances and systems. This steady generation helps maintain a level of energy independence and security, safeguarding against power outages and fluctuations in grid-supplied energy.


    In conclusion, while the efficiency of solar panels might decrease on cloudy days, it's crucial to remember that photovoltaics also work without the sun shining brightly. Even under overcast skies, your balcony power plant can harness significant energy, contributing to sustainable power generation. Understanding the dynamics of photovoltaic power generation in varied weather conditions underscores the resilience and adaptability of solar technology. Embrace the potential of your balcony power plant, and let it surprise you with its cloudy-day capabilities.

    Frequently Asked Questions about Photovoltaics also work without the sun

    What happens if a module is in the shadow?

    When a solar panel or module falls into shadow, its energy production decreases since less sunlight reaches the photovoltaic cells. However, the rest of the panels not in shadow will continue to produce electricity. The impact on overall system performance depends on the extent of the shading and the system's design.

    When does a PV system not produce electricity?

    A PV system does not produce electricity at night or when completely covered with something like snow or debris. During these times, the system is inactive due to the lack of light required for the photovoltaic effect.

    Does storage make sense for balcony power plants when it is cloudy?

    Yes, implementing storage solutions like batteries for balcony power plants can be beneficial, especially in cloudy conditions. Batteries can store energy generated during sunny periods, which can then be used when the solar output is reduced, ensuring a consistent energy supply and enhancing the system's overall efficiency.