Solar array under the nighttime sky and full moon.

Summary

  • Solar energy derives from the radiation given off by the sun or sunlight. The sun works like a natural nuclear reactor, emitting tiny packets of energy called photons. Solar panels convert solar radiation into energy that can be used for electricity and other applications.
  • Two leading types of solar panels are used today – photovoltaics (PV) and concentrating solar power (CSP). Both types of solar panels produce energy as long as there is sunlight. However, at night, PV cells have nothing to absorb, and CSP panels have nothing to reflect and so cannot generate energy.
  • The Department of Electrical and Computer Engineering at the University of California (UC), Davis, published a paper stating that a specially designed photovoltaic cell could generate power at night. This is referred to as the “anti-solar” panel.
  • To create an anti-solar panel, PV cells need to operate in the opposite way to a standard solar panel during the day. A regular solar cell collects energy as it is transferred from the sun to the Earth. An anti-solar panel would absorb the energy that escapes from Earth to outer space at night.

Introduction

There has been a massive uptake in the use of renewable energy sources, with solar panels becoming a familiar sight on the roofs of homes and businesses. Farmers are even welcoming solar to their land to establish an additional income stream and power their equipment more sustainably. However, some are still unsure whether investing in solar energy is worth it, given that power can be generated only when the sun is out.

Anti-solar cells are a potentially giant leap forward for the solar industry as a photovoltaic cell that works at night would address the regular solar panel’s main limitation. At the University of California (UC), Davis, the Department of Electrical and Computer Engineering believes a specially designed photovoltaic cell could produce up to 50 watts of power per square meter under ideal conditions at night. The estimated output is about a quarter of what a conventional solar panel can generate during the day.

As promising as new solar technology may be, it is not yet readily available, so in the meantime, it is worth getting clued up on conventional solar power. This article looks at solar energy fundamentals and existing solar technology before exploring the exciting possibility of generating solar power at night.

What Is Solar Energy?

Solar energy derives from the radiation given off by the sun – known as light.

The sun is a powerful energy source. People have been harnessing the sun’s power since time immemorial. We use the sun’s energy to stay warm, heat water and cook our food. In fact, life on Earth would be unsustainable without the sun, and nothing would exist on it.

Around 44% of solar radiation is in the visible light wavelengths. However, the sun also releases ultraviolet, infrared, and other wavelengths. When the wavelengths are viewed together, a visible white light appears. Amazingly, it only takes an hour and a half of sunlight striking the Earth’s surface to power the world for an entire year.

Solar energy derives from the radiation given off by the sun – known as light. The light seen in the mornings and during daylight hours is actually energy. Different locations around the world receive various amounts of solar radiation during the year. The level of sunlight fluctuates subject to the time of day, location, season, geography and local weather patterns.

The sun works like a natural nuclear reactor. It emits tiny packets of energy called photons – which travel 149.6 million kilometres from the sun to the Earth in roughly 8.5 minutes. Solar panels can convert solar radiation into energy that can be used for electricity and other applications. In the following section, we consider how solar panels work.

How Do Solar Panels Work?

Solar panels are made up of multiple cells, and various panels, or modules, that are wired together to create a solar array.

Infographic showing how a photovoltaic solar panel generates electricity.

When the sun’s photons strike a PV cell, they knock the electrons in the cell loose from their atoms. Conductors attached to the positive and negative parts of the cell can form an electrical circuit. As electrons flow through the circuit, they produce electricity. Solar panels are made up of multiple cells and various panels – or modules – wired together to create a solar array. The more panels deployed the more energy that can be generated.

Two leading types of solar panels are used today – photovoltaics (PV) and concentrating solar power (CSP). The following is a brief outline of each:

  • Photovoltaics (PV) – The typical solar panels likely to be spotted on rooftops and fields are called photovoltaic. When sunlight shines directly onto the solar PV panel, the photovoltaic cells absorb the energy. This energy generates an electric current which can be used to power electronics and other home devices.
    One PV cell can generate between one to two watts of power, so multiple PV cells are put together in modules or chains to create a solar panel. The conversion efficiency can be affected due to various factors, such as reflection, wavelength and temperature.
  • Concentrated Solar Power (CSP) – Unlike PV panels which use cells to absorb sunlight, CSP panels use mirrors that reflect the sun’s rays. The mirrors focus the sunlight onto receivers, which convert the energy into heat. The generated heat, or thermal energy, can be stored for later use or converted into electricity. This type of solar technology is typically reserved for industrial applications.

As long as sunlight is hitting the panels, both types should produce energy. However, PV cells can’t absorb any energy without sunlight. Similarly, CSP panels can’t reflect any light for heat generation. This leads to the uncertainty of whether solar panels are worth the investment if they only work during daylight hours.

Is It Possible for Standard Solar Panels to Work at Night?

The short answer is no – standard solar panels are unable to generate electricity at night.

The short answer is no – standard solar panels are unable to generate electricity at night. However, this does not mean that panels do not generate enough energy during the day to support your power needs at night.

Fortunately, solar panel technology is now at a level that can generate power whenever sunlight is available. During the day, the panels absorb enough energy that can last several hours. The excess energy can also be stored through net metering or solar batteries to ensure enough power to last through the night.

When solar panels are installed, you can choose to connect the system to the primary grid, which offers net metering. This method sends the electricity produced by the panels directly back to the central grid. Depending on where you are located, the electric company will provide some sort of compensation. For example, certain electric companies will award credits for the power received – which can be used at night when the solar panels are not producing electricity. An alternative to net metering is to install solar batteries. They allow surplus energy to be stored throughout the day and used whenever needed.

Both power backup options ensure solar energy is available outside of daylight hours. This makes solar panels a potentially good investment, and the need for solar technology that works at night into question.

The Theory of Anti-Solar Panels

To create such a solar panel, PV cells need to operate exactly opposite to a standard solar panel during the day.

Even though modern solar panels are pretty efficient at power generation, new renewable energy technologies are being developed. After all, if there is the possibility of a type of solar panel that works at night, why not explore the science? The planet needs all the support it can get in combating climate change, and a nighttime PV cell may facilitate constant power generation.

In November 2019, a team of researchers from UC Davis published a paper in the journal ACS Photonics, claiming to have found a way to potentially generate power at night with an alternative photovoltaic system. To create such a solar panel, PV cells need to operate exactly opposite to a standard solar panel during the day. The solar industry refers to it as the “anti-solar panel”.

Solar panels are cold, so they can absorb the sun’s light more readily and convert it into energy. Space is incredibly cold, so when a panel on Earth is comparatively warm pointed towards it, the panel will radiate heat as invisible infrared light. This process would allow the anti-solar panel to generate electricity by capturing that energy. The UC Davis paper claims such a device could produce around a quarter of the electricity at night that a regular solar panel generates during daylight hours.

UC Davis describes solar panels as essentially “heat engines”. There is heat energy coming from the sun towards the Earth. A regular solar cell collects this energy as it is transferred from the sun to the Earth. The theory is an anti-solar panel would do the opposite, but only taking a hot body and a cold body into account. The warm  Earth would radiate heat into cold space. As the heat flows from the Earth to outer space, the anti-solar panel captures the heat and converts it into power.

The Takeaway

While conventional solar panels do not work at night, there is no reason that you can’t rely on solar power during the night. Modern solar panels can now spend all day absorbing sunlight and store surplus energy in solar batteries or send it directly to the central grid for future use – or a combination of both.

In the future, anti-solar technology solar panels that work at night may be as readily available as existing solar technology. While this new solar science is being developed, existing solar power plays an essential role in tackling climate change and providing a reliable source of renewable energy.

Frequently Asked Questions (FAQs)

Do solar panels work with moonlight?

No, solar panels cannot generate electricity from moonlight. Solar panel technology requires direct sunlight to produce electricity as sunlight comprises several particles, including energy particles known as photons. Unfortunately, the moon doesn’t create photons or produce its own light, so it cannot charge solar panels.

 

Can solar panels work without direct sunlight?

Solar panels can still generate power during a cloudy day or in indirect sunlight – however, generation will be less efficient. For solar systems to function at optimum levels, they need direct sunlight on a clear, sunny day. Either way, solar panels will work without direct sunlight, albeit less efficiently.

 

Do solar panels radiate heat at night?

Conventional solar panels become hotter the more exposed they are to sunlight and in warm climates. A solar panel absorbs sunlight and converts the sunlight into electricity. Some of the absorbed sunlight is converted into heat which results in the solar panel heating up. Space is very cold, so if a warm object such as a solar panel is pointed to the sky, it will radiate heat toward it.

 

Why can’t traditional solar panels work at night?

The majority of solar panels are made up of photovoltaic (PV) cells – which convert sunlight into electricity. For these cells to function, the panels require at least a low level of sunlight. Unfortunately, this means traditional solar panels cannot generate energy at night.

 

What is a thermoradiative cell?

A thermoradiative cell generates an electrical current as it radiates infrared light, or heat, towards the extreme cold of space. UC Davis engineers have proposed that such cells could produce a considerable amount of power and help balance the power grid when standard solar panels cannot generate electricity.

 

Westbridge Energy Corporation

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