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Do Solar Panels Need Direct Sunlight​

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A solar panel without sun is a bit like a snowboard without snow, it seems absurd. And yet, extreme athletes enjoy hurtling down the dunes of the world’s deserts with their snowboards and solar panels can produce electricity, even under overcast skies. Together, let’s discover the possibilities and limits of do solar panels need direct sunlight​.

In short

A photovoltaic panel works thanks to sunlight, and not the sun directly. There are several reasons that can explain a partial or total absence of the sun and a decrease in the efficiency of the solar panel:

  • Cloudy skies
  • Shade
  • The beginning and end of the day
  • At night
  • Rain

To be able to benefit from electricity thanks to solar panels without sunlight, you must:

A solar panel seeks light, not the sun

First of all, it is important to remember schematically how a photovoltaic solar panel works, because it captures light and converts it into electricity. It is therefore light that transfers its energy to the free electrons present in silicon, a semiconductor material used to create this physical phenomenon.

Thanks to this energy, the electrons move, causing a direct electric current that the solar inverter transforms into alternating current. This alternating current can power the electrical appliances in our homes.

No sun, and why is that?

When we say that the weather is overcast, it is not pitch black. If the sun is not visible, light continues to flood the Earth’s surface, even if it is more diffuse. There are therefore cases where the panels will continue to produce electricity, even without an apparent sun.

Cloudy skies

When light passes through a cloud, it is called light diffraction. To put it simply, the cloud acts as an obstacle or filter that does not let all the light through and divides its beam. The yield is therefore not optimal since the amount of light is less than a sky where the sun is shining brightly.

Fog also diffracts light, making it more subdued, reducing the efficiency of solar panels in this way.

Contrary to what one might think, a few scattered clouds under a blue sky are not obstacles to the efficiency of solar panels. Indeed, by propagating through white clouds, the light is often brighter and, therefore, more “concentrated” for the solar panels. In this case, a slight increase in production may occur.

In the middle of summer, a few clouds can even relieve the solar installation by lowering the outside temperature. A panel that is too hot loses efficiency. Clouds are therefore not the sworn enemies of solar panels as one might think.

Does a solar panel work in the shade?

The principle of a solar panel in the shade is the same, with indirect and lower light, the efficiency of the solar panels will be lower.

In the morning

The sun emits less light at dawn and dusk. However, it is enough to activate the photovoltaic cells of a solar panel and produce electricity. Again, the yield will be lower than under full sun at its zenith, which is natural. It is estimated that an installation’s actual power is between 75 and 80% of its peak power. With clouds, fog, or at dawn, the solar system’s actual power decreases further.

At night

The solar panels don’t work at night because the light is extremely dim.

The moon that shines? This is the result of the sun shining so brightly on it that it reflects its light and this is how we can admire the nocturnal star from our earth. However, this is not enough light to activate the photovoltaic cells (the lighting is not enough to wake up the electrons in the silicon in the panel).

A solar panel that produces during the night? It’s a project in development! By using the difference in heat between a panel during the day (which heats up) and at night (it cools) and this transition from one to the other, thermo-radiative cells will capture this heat transfer and transform it into electricity! Like all panels under development, its still very low yield does not allow it to be put on the market.

Rain

When it rains, the clouds still get in the way, not the rain. However, an earthy rain can partially or totally cover the solar panel and thus reduce its ability to capture light.

Rainwater panels are part of the solar panels of the future. By bringing rainwater into contact with a transparent polymer material, a phenomenon of triboelectricity is created, causing an electrostatic current. Because this material is transparent, it is quite possible to put silicon underneath so that the panel reacts to rain (provided it is strong, a small drizzle is not enough)! Let’s not jump for joy though, the yield of these panels is still low.

Solar without the sun is yes with batteries!

Batteries make it possible to take advantage of the solar energy produced during the day at any time of the day or night.

The solar battery

Like any other battery, the solar battery stores electricity so that it can be used at any time.

Virtual storage

To put it simply, this virtual storage system allows a solar installation to “entrust” the surplus electricity produced to a third party (an electricity supplier), who can use it.

In exchange, this supplier undertakes to provide the same amount of energy to the household free of charge when needed. In short, the electricity produced (which would otherwise be lost) is “loaned” to a third party, who can return it at any time.

The solar thermal panel, the exception

The solar thermal panel provides heat and therefore needs heat and not light to operate. This type of panel is therefore insensitive to light. Rather, it reacts to the outside temperature and the thermal energy released by the sun. A solar thermal panel will produce more heat in a tropical rain at 30°C than in the full Norwegian sun with sub-zero outdoor temperatures.

Better performance without sunlight, our advice

There are a few countermeasures to ensure that the installation does not suffer too much from a lack of light.

Opt for quality equipment.

While it may seem obvious, quality solar equipment can be a game-changer. There are indeed panels with solid-state cells that make it possible to produce electricity in very low light. More so, the choice of the peak power of a panel will be important. The more powerful it is, the more it will produce, even without optimal sunlight. Finally, modern solar panels have a higher efficiency than older ones, and that’s why equipping yourself with equipment that is not obsolete can make a big difference.

The bifacial solar panel, for example, captures albedo (the reflection of light on a surface) to produce energy with its back! Even with less light, this panel makes more use of the light, which gives it a higher performance than normal panels.

Location and inclination are key

The orientation and tilt of a solar panel can change everything. Indeed, the longer the panel is exposed to direct light, the more electricity it will produce. A problem that does not exist for nomadic solar panels that can be placed and moved anywhere, from balconies to isolated places. This is not the case for a solar installation on a roof or in a garden.

Maintaining the solar installation

Cleaning your solar panels is an important thing to ensure optimal performance. With a layer of dust or dirt covering part or all of the panel, that’s as much solar surface that doesn’t produce.

A tailor-made solar installation

Because sunshine is not the same everywhere, each home is unique, and families’ energy needs are unique, SolarLab offers support for your solar project from its design to its commissioning!

This collaboration is illustrated in three main stages:

The lack of sunlight and light is a factor that can be expected in a solar installation. So this is no excuse to refuse to jump into the energy transition with both feet. Thanks to ever-improving yields and new technologies on the horizon, there is no doubt that a lack of sunlight will soon no longer be a problem at all for the productivity of solar panels!

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