Can You Charge a Solar Cell with Artificial Light?

Because solar cells are designed to be charged off of sunlight, many people wonder whether artificial light will do the trick as well. The answer may surprise you.

So can you charge a solar cell with artificial light? The answer is yes, artificial lights such as incandescent bulbs can be used to charge solar cells, provided the light is strong enough. But it will not be nearly as efficient as charging the cell in direct sunlight. 

What light can be converted to electrical energy is dictated by a certain range of wavelengths of light, which are present in both direct sunlight and artificial light. Therefore, the battery can be charged from either source of light. 

How is a solar cell charged with artificial light? Read on to find out more about how this form of energy generation works and why someone would potentially do it. 

Solar Cells and the Light Spectrum

Solar cells are used in technology to capture photons of light and convert this light into electrical energy that can be funneled into circuits for domestic and commercial use. These flat, dark-colored, shimmering cells are a technology that is rapidly expanding in the modern world.  

Solar cells work by collecting wavelengths of light to electricity using semiconductor technology layered behind a sheath of glass coated with anti-reflective materials. This allows sunlight to reach the semiconductors in the solar cells more efficiently. 

Two layers of semiconductors exist within the solar cell, and these consist of two types of materials:

  • N-type (negative type) material: This material forms the first layer of a solar cell semiconductor and is typically composed of silicon mixed with trace amounts of phosphorus. This causes the silicon to carry a negative charge.
  • P-type (positive type) material: The second layer of semi-conductive material in the solar
    cell is positively charged, and typically consists of silicon mixed with trace amounts of the element boron.

On the backside of the solar panel, the solar cell contains an electrode beneath the p-type semiconductor that functions parallel to the metallic grid in the solar cell to create an
electric current. Then another reflective coating is layered behind it. 

While solar panels can vary slightly in material composition and design layout, this fundamental configuration is used by all solar panels to conduct sunlight and generate electricity.  

How a Solar Cell Conducts Artificial Light

Provided that the artificial light in question emits the same kinds of wavelengths of light present in sunlight, the solar cell will be capable of collecting electricity from that light in exactly the same way it would in direct sunlight. 

When artificial light shines down on solar cells, this light has the potential to be reflected, absorbed into the cell, or pass directly through it. 

For full potential energy generation, solar cells aim to reduce the amount of light that passes through the solar cells or bounces off of them. Due to this reason, solar cells are designed with a few particular features:

  • Solar cells are dark in color and opaque to increase the amount of light absorbed by the cell and decrease the amount of light that passes through it.
  • Solar cells feature an anti-reflective covering that helps to keep light from bouncing back off the solar cell and aids absorption of the light into it. 

While so far it is technologically impossible to recreate a solar power grid that absorbs 100% of the light that is shone onto it, energy scientists are getting closer and closer to this level of efficiency all the time with the creation of new-age construction materials and new engineering designs.

The more light is absorbed by these solar cells and the less light that is wasted in the effort, the more electricity can potentially be generated from each solar panel, bringing the costs of energy consumption closer and closer to zero minus the initial investment in equipment. 

Function of Semiconductors

When light is absorbed into the solar cell and enters the interior of the cell, the semiconductors found within absorb this light as well. Photons excite the atoms contained in the semiconductors and make them more energetic. 

The two layers of semiconductors, positive and negative, interact by swapping electrons from the negative semiconductor layer to the positive semiconductor layer. 

Once these electron migrations are put into motion, the metallic grid of the solar panels pulls free electrons towards itself in a single direction, creating an electrical current. This current is pushed through an exterior circuit and eventually captured and banked in a solar battery for further use.

Artificial Light Reduces the Efficacy of Solar Power

While artificial lights are capable of powering solar cells, these kinds of light can never charge a solar cell as efficiently as direct sunlight can. There are a variety of reasons for this phenomenon:

  • Loss conversion: To use an artificial light, you must first convert electricity to light for the solar cells to absorb and convert back into electricity. During this conversion process, a percentage of the energy is lost. This means that using an artificial light to charge solar cells is less efficient than not running the artificial lights at all.
  • Barriers to light: Artificial lights often contain barriers such as bulbs and ballasts that temper their intensity and cause some of the light they emit to be either absorbed by glass or diffused into the room. This makes them less efficient light sources overall.
  • Artificial light design: Artificial lights were not designed with the efficiency of solar cells in mind, which makes them poor substitutes for real sunlight. Most artificial lights are designed to put out very low levels of ultraviolet light and for the same reason they are mostly designed to be low temperature fixtures. These design decisions were made based on human safety, not energy efficiency. 

By reducing the amount of UV and infrared light they emit, artificial light also reduces the amount of useable light that is able to be absorbed by the solar cells.

Spectral Irradiance of Artificial vs. Sunlight Matters

The type of wavelengths emitted by both artificial light and sunlight are a big factor in how efficiently they can be used to generate power with a solar cell, but it isn’t the only important factor to consider. Another factor is spectral irradiance, also known as spectral intensity. 

This phenomenon is the intensity with which a light source emits light. The sun’s spectral radiance is extremely strong and constant, covering a wide variety of light wavelengths, which allows for maximum efficiency of light absorption in solar cells. 

However, artificial lights not only have a weaker spectral irradiance than solar light, they can experience sharp fluctuations in spectral irradiance that reduce their overall energy absorption.

Because the energy solar cells collect under these conditions does not equal the energy given off from an artificial light to begin with, the entire amount of energy generated by the solar cells is a net loss, due to the theory of conversion loss. 

Conversion Loss

Conversion loss is the main energy concept that causes the amount of electricity generated by a solar cell powered with artificial light to be less than the energy used by the artificial light to begin with. 

Conversion loss refers to the amount of energy lost when it is converted from one form to another (in this case, from direct current to alternating current). While solar cells generate direct current, this type of electricity cannot be used to power most household devices.

Instead, an inverter is used to invert the current and turn it to AC current, allowing it to be safely used to power appliances, lights, and other electrical items in the home. 

When electricity is converted to artificial light, absorbed into solar cells, and made into electricity again, it loses a percentage of its inherent energy value. This means the amount of energy generated by this method will always be less than the original amount of energy used. 

Solar Panels Can Create Energy with Any Visible Light Source

If light is strong enough to be visible, that means it is strong enough to power a solar cell. Any artificial light, from fluorescent ballasts to incandescent bulbs, can give off some kind of light that is able to be absorbed and used by solar cells. 

However, there are two caveats to this fact:

  • Any energy created via artificial light is only going to be a fraction of the energy that would have otherwise been generated with solar power.
  • Using artificial light to charge solar cells is not efficient, as the artificial lighting will generate less electricity than was used to power the artificial light to begin with, thanks to conversion loss. 

Some of the types of artificial light that can be used to charge solar cells are as follows:

  • Ultraviolet lights: Traditional PV panels do not operate on ultraviolet light, though they are capable of absorbing small amounts of it. Therefore, artificial ultraviolet light is a poor choice for charging solar cells.
  • Incandescent lights: Incandescent lights feature a wire filament (typically tungsten) housed in a bulb. Not only are incandescent lights poor choices for charging solar cells, they are generally the least efficient energy option out of all modern-day electrical lights.
  • LED lights: LED lights (or light-emitting diodes) can be used to charge solar cells, but they are less efficient at emitting light even than incandescent lights, because they function within a smaller range of spectral light. 

While each of these light sources can charge a solar cell to one degree or another, none of them can mimic the strength and radiance of true sun rays, which is why solar cells were designed to absorb. 

Just because a technology can do something doesn’t mean that it is capable of doing it at the level needed to perform efficiently. Bikes and cars are both propelled by human acceleration, but a manually pedaled bike is never going to beat a car in a head-to-head race. 

Likewise, while solar cells can glean some energy from artificial lighting, this form of energy collection will never be able to compete efficiently with the power gleaned from direct sunlight, even though the solar cells draw energy from both sources in the same way. 

Natural Light is Most Efficient

The main reason that direct sunlight is a more efficient energy source for solar cells than artificial light, besides conversion loss, is the fact that sunlight contains not only the visible spectrum of light, but significant amounts of infrared and ultraviolent light as well.

Solar cells are able to convert roughly half of the infrared light they absorb into energy, and a portion of the ultraviolet light (but not much of it, making UV lights some the least efficient lights to charge a solar light with).  

In sunlight, these additional wavelengths of light bolster the efficacy of a solar cell with more photons, allowing them to convert more electrons into more electric current. In this way, direct sunlight generates more energy than artificial light. 

Artificial lights also give off UV and infrared light, but in very trace amounts in comparison to the blaring intensity of the sun. In fact, none of these artificial sources of light hold a candle to the sun when it comes to charging solar cells. 

Ways to Test Efficacy of Artificial Light in Solar Cells

While you can read wavelength comparisons all day long in an attempt to wrap your head around the concept of energy efficiency with regards to solar versus artificial light, the easiest way to really grasp this scientific premise is to put it to the test. 

By using the energy output specification charts that should have been included with your solar cells/panel, you should be able to figure out how much energy your solar cells are collecting at any given time and under different circumstances. 

One easy way to measure how effective solar lights are with artificial light compared to solar light is to gauge the output of a solar cell under the following light conditions:

  • Fluorescent lighting
  • Flame (candlelight)
  • Incandescent light
  • Moon exposure
  • Solar exposure (direct sunlight)
  • Solar exposure (indirect sunlight) 

Using a specification sheet that is specific to your solar cell, you can take data of the energy generated under each of these light sources and compare the results. 

When you’re done, you should be able to see that solar cells are able to convert sunlight to energy better than any other light source. Solar cells are very specialized technology, and for them to work properly, they need to be used in direct sunlight. 

Technology is beginning to change though. Read on to find out more about new solar cells and how they will be able to convert different kinds of light more efficiently than ever before. 

New Dye-Sensitized Solar Cells Are Changing the Technology

While your average solar cells in a photovoltaic panel are not strong or efficient enough to convert forms of light other than sunlight into feasible amounts of energy, this fact is changing rapidly thanks to advances in materials technology and energy science. 

According to an article in ScienceMag in April 2018, scientists have managed to create state-of-the-art solar cells that are more efficient than ever before. 

These super solar cells are not only able to convert electricity from direct light, they’re also able to utilize diffuse light found on the interior of office buildings on overcast days, which means they can effectively be used to generate electricity from indoors. 

These new solar cells are called dye-sensitized solar cells (DSSC) and while they have been around since the early nineties when they were first engineered by Dr. Michael Graetzel, they have just begun to receive engineering improvements that transform their entire efficacy.

Other New Kinds of Solar Cells

Other than DSSC cells, new solar cells have also been invented that are completely transparent. The significance of these solar cells is that they may (in the future) have the ability to make every window and device screen a potential power source.

These solar cells are known as solar concentrators and may soon be used in everything from skyscrapers to phone screens. 

Unfortunately, these solar cells currently only have an efficiency of 1%, but scientists hope that with more engineering advances, they will be able to bring this efficiency up to 10% once full production begins. 

All these new kinds of solar cells have only started to be really developed and refined in the last few years, so there’s no telling what new advancements we’ll see in the field of energy science in the
next decade. 

Charging Solar Cells in Artificial Light is a Waste of Energy

Except to prove the concept of conversion loss in energy generation, there’s no real efficient or intelligent reason to try and power solar cells with artificial light, at least with the current generation of solar power technology that exists. 

While sometime in the near future we may be able to charge solar cells under indoor lighting or even insert solar cells into our glass screens and windows, the future is not here quite yet, so current solar cells cannot efficiently convert artificial light into any useful amount of electricity.  If you’re trying to charge solar cells, the best thing to do is put them out in the sunlight. Even indirect sunlight will charge a traditional PV solar cell faster than any source of artificial light ever could, and you’d be expending more energy to power the artificial light than you’d collect.

spgenie

Hi I'm Harris the spgenie! As an engineer, I found myself doing tons of research about solar power, the types of panels, how to store the energy and the best way to finance the project. I thought I'd start this blog to share my findings. I hope you find this useful.

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