The most obvious benefit of generating your own power from sunlight is the reduction in greenhouse gases and other pollutants that conventional power plants relentlessly spew into our air.
Not just burning, but even mining fossil fuels is an inherently destructive process that releases carbon dioxide, nitrous oxide, and methane into the earth’s atmosphere. Besides contributing to climate change, when we disrupt and poison the balance of gases nature intended us to breathe, we pay the price by suffering more respiratory illnesses, like asthma and even cancer.
Generating solar energy, on the other hand, is purely productive. It emits no harmful gases to disrupt the atmosphere’s natural equilibrium or harm our children’s still developing lungs.
Saving The Water We Drink
One of the Power Plant Industry’s best kept, dirty, not so little, secrets is that, besides the toxins and greenhouses gases emitted into our air, they’re also the biggest polluters of our water supply as well.
A 2013 study by the EPA found that power plants dump more toxins like mercury, arsenic, and lead into our waterways than all of the next nine industries combined! These heavy metals act like neurotoxins. They can disrupt normal development in children, harm babies in the womb, damage everyone’s internal organs, and even cause cancer.
The worst part is that, instead of degrading, heavy metals accumulate. So, we can’t keep using power sources that dump them into the earth’s water supply indefinitely without eventually dumping them into our own. Even for the limited time we can keep them out of our drinking water, they still wind up impacting us by traveling up the food chain and accumulating in our bodies.
Solar panels, on the other hand, generate electricity without using water at all. You don’t have to pollute the earth’s water with dangerous toxins whenever you make a smoothie or turn on a light.
Saving Our Land
But industrial power plants don’t just pollute our air and water. They’re a triple threat – emphasis on threat. Coal-fired plants produce millions of tons of solid toxic waste every year as well. It gets quietly dumped into abandoned mines, landfills, and other places where it destroys fragile ecosystems and can be hazardous to nearby residents.
There’s only a finite amount of space on the planet. If we don’t switch to renewable energy sources like solar, eventually the toxic sludge produced by power plants is going to wind up in all our backyards.
Saving The Planet’s Natural Resources
Because industrial power plants produce energy through essentially destructive processes, they aren’t renewable sources of energy. Elements gradually formed in the earth’s crust over the course of its four and a half billion-year life are, in an instant, irrevocably destroyed.
The productive nature of solar power, on the other hand, makes it not just a clean energy source, but a 100% renewable one as well.
Saving Our Climate
The U.S. Energy Information Administration estimates that in 2018 electrical power plants produced 1,763 million metric tons of the greenhouse gas carbon dioxide. That accounts for a staggering 33% of total U.S. emissions!
That’s why a recent study from scientists at the University of California published in Nature concluded that keeping global warming out of catastrophic range will require, not just building no new power plants, but also shutting down old ones.
If we want to preserve the planet for future generations and keep present ones healthy, weaning ourselves from toxic and destructive non-renewable energy sources will be crucial.
The electricity powering your home is a flow of electrical charge created by the movement of tiny negatively charged subatomic particles called electrons. Though it’s often claimed that electrical current is composed of the electrons themselves, this isn’t really true.
Your appliances run on AC or alternating current, meaning the flow of electrical charge is constantly switching directions. AC current in the U.S. switches back and forth a remarkable 60 times every second. That’s so fast that the electrons in your wiring never even get a chance to flow in either direction and wind up simply vibrating back and forth instead. But their back-and-forth vibrations do, nonetheless, cause an alternating current of electrical charge to flow through your outlets.
One factor complicating solar power systems is that the panels themselves don’t produce the AC current you need. Instead, they generate DC or direct current, which flows continuously in just one direction. So, in addition to panels, devices called inverters are necessary to convert the panels’ DC output into the alternating current required to run your appliances.
Because the flow of electrical charge in DC current never changes direction, the electrons aren’t stuck in place vibrating like they are in AC. Instead, they flow in the same direction as the electrical charge they carry – albeit at a much slower rate.
Turning sunshine into cost-free electrical power became possible when scientists and engineers developed efficient two-sided solar cells. When exposed to sunlight, these miraculous wafers generate a continuous flow of electrons through a wire running out of the top side, to your inverters which convert the DC current to AC for you to use or sell, and back to the bottom side.
Electrons & Photons
Electrical wiring conducts electricity because it’s composed of metals like copper containing relatively free electrons that aren’t bound too tightly to any particular molecule. So, when a force that pushes electrons is applied to one end of a copper wire, even if it’s relatively weak, it can break some electrons in the copper completely free and cause them to flow through the wire like a pump pushing water through a pipe. Plastic and other poor conductors are like permanently frozen pipes – all their electrons are bound tightly and, hence, “frozen” in place. So, it takes massive amounts of electrical force, or voltage, to get the electrons in plastic to move at all.
Generating solar power is possible because light is composed of incredibly small particles called photons that can interact with electrons. If the photons in a beam of light striking a metal surface have enough energy, any electrons they impact not bound too tightly to their molecules will be “knocked” free. Some will even be “knocked” off and emitted from the metal’s surface. Albert Einstein was awarded his Nobel prize for explaining this scientific phenomenon, known as the Photoelectric Effect.
But it’s also possible to channel the Photoelectric Effect into another scientific process called the Photovoltaic Effect. That’s when electrons impacted by sufficiently energized photons of light, instead of being randomly knocked around, get channeled into wires by an electric force, creating DC electrical current.
Generating Solar Power
That’s how solar power is generated. A solar panel is constructed out of several dozen wafer-like solar cells each composed of two different types of material:
A negatively charged top layer that contains extra electrons.
And a positively charged bottom layer that is missing electrons and, hence, attracts the extra electrons in the top layer.
The attraction between the top and bottom layers of a solar cell creates an electric field between them. The electric field in turn exerts an electrical force. So, when an electron in a solar cell is knocked free by a photon of light, it’s channeled toward a wire running from the top layer of the solar panel, to your inverters, and back to the bottom layer. When enough electrons are knocked free by sunlight, voilà! A flow of electrons producing DC current is created.
Next time, we’ll talk more about how the two kinds of materials composing solar cells create the force that channels electrons freed from their molecular bonds by the sun into free and clean electrical power.
Creating free electrical power from the sun’s rays requires more than just solar panels. Devices called inverters are necessary to convert the DC current produced by your panels into the AC current your home runs on. But a very small quantity of energy is lost in the process. So, when shopping for a solar system, make sure the energy production estimates you’re getting from different providers are all based on the same kind of current.
For comparison purposes it doesn’t matter which. But it makes sense to look at estimates based on the AC power the inverters are sending into your home rather than the DC power initially generated by your solar panels. That way, you get a more accurate idea of your electric bill offset.
But why don’t solar panels themselves automatically produce the kind of power you need?
Electricity Isn’t Really Electrons
AC stands for Alternating Current. DC stands for Direct Current.
Strictly speaking, mentioning AC or DC “current” is redundant since it’s already meant by the “C”.But like “SAT test” and “PIN number,” acronyms sometimes become so common that we stop thinking of them as such. It then seems funny not to redundantly throw in that already included last word when it helps to explain the concept being abbreviated.
Just like a current of water, an electrical current is something that flows in a certain direction.But the kind of current that flows through wires is composed of an electrical charge carried by electrons in motion. You’ve probably heard people say that electricity is composed of the electrons themselves. That common explanation does make it easy to visualize electric current. But, in reality, alternating current actually prevents the electrons themselves from flowing.
Alternating Current gets its name because the direction in which it flows is constantly alternating back and forth. The AC powering your appliances changes directions an amazing 60 times every second. That rapid oscillation never even gives the electrons a chance to start flowing and they wind up vibrating instead. But the vibrations do, nonetheless, cause current or electrical charge to flow in alternating directions.
Direct Current, by contrast, continually flows in one direction. Its name can be a little misleading since DC isn’t really any more direct than AC. But, in direct current, the electrons themselves do flow with the electrical charge.
Why AC Became Standard
Around 200 years ago, scientists discovered an efficient way to generate electricity using a spinning magnet. But, instead of direct current, it produced current that alternated direction with the magnet’s rotation. Since there wasn’t any practical use for alternating current, early alternators usually had devices which converted their output to DC. Automobiles today still use an alternator to efficiently generate AC power, which is then converted to DC for battery storage.
When the invention of the electric light bulb created a demand for electric lines running into our homes, however, alternating current turned out to have one very big safety advantage. Transmitting electricity over distances much more than a mile requires dangerously high voltage to minimize the amount lost from electrical resistance. But lowering the voltage of direct current so it was safe to run into people’s homes was technologically unfeasible. As a result, DC power plants had to be very close to their customers. Besides all the inconvenience and inefficiency, generating DC power at a reasonable cost for sparsely populated regions was impossible since each plant could only serve a few homes at most.
Around 1886, however, William Stanley* invented a commercially viable device for transforming high voltage alternating current into a safer lower voltage. That meant that large scale power plants could provide high voltage AC power to customers many miles away and Stanley’s transformers could then be used to lower the voltage to a safe level before bringing it into their homes.AC power pretty quickly became the norm and manufacturers stopped producing DC appliances.
The way solar panels generate energy from sunshine produces DC power. Nowadays, we actually have the technology to easily transform DC power to low voltage too. If it had existed 200 years ago, all the appliances in your home would run on direct current and we wouldn’t need to use inverters or accept the very small lose in energy production.
Thankfully, since solar power is a completely clean and 100% renewable resource, there’s always more sun to make up the small difference. And we don’t have to worry about damaging the environment by doing so.
*Though Nikola Tesla invented the AC motor and helped refine other technology important to making alternating current the dominant technology, he did not invent the transformer as is commonly claimed.
Albert Einstein is famous for revolutionizing physics with his Theory of Relativity. But did you know Einstein also discovered the science behind the solar technology now revolutionizing the way we produce energy?
In fact, Einstein was awarded his Nobel Prize, not for his famous equation E=MC2, but for the groundbreaking theory of light he developed to explain something called the Photoelectric Effect.
And the Photoelectric Effectjust so happens to be the scientific process that makes it possible to turn sunshine into a cost-free, clean, and renewable source of energy.
A Mysterious Novelty
Though it literally took an Einstein to explain the science of solar power, the sun’s capacity to generate electricity was discovered by a mere teenager forty years before Albert was even born! In 1839, a 19-year-old French researcher named Edmond Becquerel exposed a conducting solution containing metal electrodes to sunlight. For some strange reason, a small electric current was produced.
Fascinating as it was, no one could explain how Becquerel’s apparatus worked and it produced too little energy to be anything more than an interesting novelty.
Scientists didn’t get a glimmer into the underlying process until almost 50 years later when, in 1887, a physicist named Heinrich Hertz discovered the Photoelectric Effect.
But Hertz’s findings turned out to be as disturbing as they were enlightening.
The Photoelectric Effect Hertz discovered that when a metal surface is exposed to light of a high enough frequency, it emits electrons that are “knocked” free from the atoms they orbit by the light’s energy. Until Einstein came along, however, no one could make any sense of what sometimes happened when Hertz altered the experimental conditions.
The theory then accepted as settled science was that light travelled as a continuous electromagnetic wave. So, because the light’s energy was transmitted in an uninterrupted flow, even if its frequency was just a little too low to immediately break any electrons free, increasing the light’s intensity or the amount of time it struck the metal ought to yield the slight energy boost required to do the job without upping its frequency.
The problem was that neither the intensity of the light nor the length of time the metal was exposed mattered. If the light was above a certain frequency, electrons were emitted as soon as it struck the metal. But, if the frequency was even the smallest fraction too low, no matter how long you exposed the metal or how much more intense you made the light, for some reason you could never accumulate the little bit of extra energy needed to break even a single electron free.
Einstein Discovers Photons
In 1905, Einstein shattered scientific consensus by showing that Hertz’s data meant light isn’t simply a continuous wave. Instead, though it resembles a wave in certain respects, light is composed of a series of separate moving particles called photons.
When light strikesa metal surface, the energy carried by the first photon impacting an electron is either sufficient to knock it free or not. If it is, the electron is emitted from the metal surface immediately. But only one photon can impact an electron at a time. So, if the energy in that first photon is even slightly below the amount required to free the electron, hitting it with another photon won’t help unless you give it enough energy to free the electron all by itself by upping light’s frequency.
Increasing the light’s intensity just meant that more photons each with too little energy to knock the electron free would be hitting it in a given period of time. Letting the light strike the metal for a longer period of time would likewise only increase the number of insufficiently energized photons uselessly striking the electron.
Einstein showed that light was both a wave and a particle and, importantly, the complex mathematical relation between its frequency(as a wave) and the amount of energy carried by its photons (as a particle).
The precise scientific understanding Einstein gave us eventually helped engineers design the solar panels that more and more people are using every day. They maximize and efficiently channel the energy produced by the Photoelectric Effect, creating a clean, renewable, and cost-free source of energy for your home.