In this article, you will learn how solar power is generated in solar panels and all the technical things you need to know.
There are a few sources of renewable energy that we use today, but solar energy is taking over for a number of reasons.
Solar power is abundant and free, available around the world, and the cleanest source of energy that we have on our planet.
When we say that solar power is a clean form of energy, we imply that it is environmentally friendly; unlike fossil fuels, it doesn’t emit greenhouse gasses and doesn’t contribute to climate change.
Let’s see how solar power is generated and how solar panels convert sunlight into electrical energy.
How Do Solar Panels Convert (Solar Power) Sunlight into Energy?
The light of the Sun travels as photons that hit solar panels which collect solar energy.
Sunlight starts its journey on the Sun and travels a distance of 9.3 million miles in about 8.5 minutes until it finally reaches our planet.
The magnitude of these photons reaching our planet in one hour can generate enough energy to fulfill the energy needs of our entire planet for a year.
When sunlight (or photons) reaches the earth and collides with the solar panels, each photon loses an electron.
There are two reasons why this happens:
- the electromagnetic nature of light and
- the design of the photovoltaic solar panel
The Electromagnetic Nature of Light
Let’s first discuss the phenomenon of the electromagnetic spectrum of light.
The light that we see is only a part of the electromagnetic spectrum.
There are other energies/radiations that we can’t see.
They have their wavelengths and their energy levels.
It’s these variations in wavelengths that create different colors of light, which we can notice in a rainbow.
While a part of the light falling on a solar panel is playing a useful role, the other part of it isn’t because either they have less energy than required to knock off an electron-hole pair or they have too high energy.
The ones with too low energy would pass through the cell as if it were transparent, whereas those with extra energy will use the required energy to knock off an electron, and the excess energy will be lost.
These losses account for about 70% of the energy lost.
Only the energy defined by our cell material is required to knock an electron loss and that for silicon semiconductors is approximately 1.1 eV.
This is called bandgap energy.
One might suggest that we choose a material that has a very low bandgap so that we could utilize the maximum number of photons.
The problem with choosing a very low bandgap is the electrical energy generated would be insufficient.
Therefore, a very low bandgap creates a small voltage, and since voltage times current is power, the electricity generated wouldn’t be enough for any use.
An ideal bandgap that balances these two factors is around 1.4 eV for a cell made of a single material.
How Do Solar Panels Work?
Let’s turn to solar power conversion into electrical energy via photovoltaic cells in solar panels.
So, how do solar panels work?
Solar panels collect solar energy via solar cells (photovoltaic cells).
As the name suggests, “photo” means light and “voltic” means electrical energy, thus photovoltaic means electricity made of light energy.
A photovoltaic cell comprises a semiconductor or combination of semiconductors, in such a way that one side of the material has a positive charge (electron-deficient) and the other hand has a negative charge (electron abundance).
Therefore, this creates a space of high potential to a low potential, which causes a flow of electrons or current.
So, when photons of light strike a semiconductor, the semiconductor absorbs these photons and sets electrons free.
Solar panels generate electricity when these electrons move along the direction of the electric field.
This is how solar power turns into electric current.
Besides, this is how one solar cell functions but, in one solar panel, there can be hundreds of such solar cells.
The more solar cells (photovoltaic cells) on solar panels, the more energy solar panels will generate.
Also, the number of solar panels in a solar system influences the amount of energy the whole solar power system generates.
Semiconductors are at the heart of solar panels, i.e. solar energy systems.
They come in a variety of combinations, depending on the material they are made of and their efficiency.
Before we go into specific properties of semiconductors made of different materials, let’s look into the electrical properties of a semiconductor and their different types based on their design.
Usually, in conductors, like copper, electrons are the charge carriers, but in semiconductors, it’s the combination of electrons and electron-holes that cause the flow of current.
Therefore, mixing two or over two types of elements creates an electron abundance at one end and electron scarcity at the other end causes a flow of current.
To accomplish this, we need to add impurities in the semiconductors, which is a process called doping.
Different proportions of impurities give unique properties to the semiconductor.
The type of doping where electrons are in abundance is called N-type doping, whereas P-type doping is when electrons are in scarcity.
Silicon is one of the most widely used semiconductors, probably due to its durability and overall efficiency.
But how much is this efficiency, one might ask?
Well, not much.
It’s around 12 to 18 % for residential units, and the best ones are approximately 23 %, but these are improving every year.
And even a slight improvement of 1% is enough to make a big difference.
To know more about the improvements in efficiency over the past century, click here.
Now back to our semiconductor design.
The problem with silicon is that it has a gleaming surface, on which light bounces back without doing its job.
Thus, an antireflective coating is applied to minimize the reflection.
Another protection is added to a solar panel, between solar cells and the elements, usually a glass cover plate.
Once the semiconductor starts separating the electrons and then making them flow in a direction, this generates electricity.
Still, what we’re getting is direct current (DC), while we need to convert it into Alternative Current (AC) to power our home appliances or any commercial or industrial machines for that matter.
To convert DC to AC, we use an inverter.
The inverter takes the direct current (DC) from solar panels and converts it into an alternating current (AC).
Along with converting DC into useful AC, inverters also provide ground fault protection and system stats, including voltage and current on AC and DC circuits, energy production, and maximum power point tracking.
What Types of Inverters Are There?
Now inverters in themselves have two different classifications: one classification is based on where the inverter is located, and the other is based on its on-grid or off-grid network.
a. Location-Based Classification
First, we discuss the classification done based on location.
It has two types one is central inverters and micro-inverters.
Central inverters were traditionally used, but their drawback was their interdependence on all solar panels at a time.
That means if one solar panel isn’t performing well because of blockage due to shade or dirt, while others are working fine, the complete performance of the system is brought down if a central inverter is connected.
Micro-inverters are a recent invention and have overcome the barrier that central inverters faced.
Their invention was a significant advancement of solar energy technologies, and now one solar cell would not affect the performance of other solar cells.
b. Network-Based Classification
Now the other classification is based on the off-grid/grid-tied network.
Off-grid inverters or standalone inverters are disconnected from the local area grid.
They store their surplus energies in batteries and use them later on.
However, in case the panel isn’t working or requires maintenance, or if the winter is too long, the homeowner will not have an alternate source of electricity.
Grid-tie inverters connect to local area grids, and that’s where their excess energy goes.
The plus point about grid-tie inverters is that its owner gets compensation for the energy that they sent to the grid, whether it’s a homeowner, investor, or organization.
Net metering is introduced because of grid-tie inverters as a good option for homeowners and offices to reduce their electricity bills.
The problem with this type of inverter is that during power outages, the owner of the panel might not receive the energy that their panel has previously given to the grid.
Hybrid Inverters are a new type of inverters.
However, a third type has been recently introduced, which is a hybrid combining the best of both worlds.
It stores backup energy in the batteries and sends the rest to the grid but becomes a bit costlier than the other two.
From Inverters to Appliances
Now that the inverter has thankfully provided us with the alternating current that we need to run our appliances, we need to look further into its journey until it powers our machines.
It sends the AC to the distribution board (DB), where it’s divided into separate circuits to propagate it into different corners of the building for various appliances such as lights, fans, refrigerators, ACs and heating systems, etc.
Circuit breakers and fuses are fixed at different points to avoid an overload of electricity, which could burn some appliances.
Now we’re free to use this electricity to power our appliances like phones, refrigerators, toasters, and whatnot.
What Are Other Types of Semiconductors?
Until now, we have been discussing semiconductors made of silicon because they’re the most popular and best known, but other materials with their unique properties have also been tested and used.
Such as germanium, gallium arsenide, silicon carbide, and the most recent and interesting one among these are organic photovoltaics (OPV).
Each one of them has its advantages as well as disadvantages, as some cost more than their performance, whereas some cannot withstand extreme temperatures.
Some have low efficiency, while others respond too slowly to signals.
Organic Photovoltaics (OPV)
Let’s focus on organic photovoltaics (OPV) specifically.
They have attracted much attention from the industry due to their promising potential of being much cheaper than silicon.
For large-scale manufacturing, this could be very profitable, and that might ultimately lower the prices of solar panels for the consumers.
The core principle in OPVs is their carbon-based structures that can be manufactured in many compositions and with different techniques that would give them unique properties.
Another one of their great plus points is their flexibility and adaptability.
They can be printed on thin rolls of plastic; they can bend or curve around structures or even incorporate them into clothing.
And they can be modified to respond to different frequency bands of sunlight.
Previously it was their low efficiency, which was half that of silicon-based semiconductors, that was stopping them from becoming the leader in solar panels.
Recent advancement has shown their efficiency has reached 17% and may reach 25% very soon.
This efficiency is astonishing given the estimates that with a 15% and a 20-year lifetime, OPVs will be producing electricity at a cost of fewer than 7 cents per kilowatt-hour.
Whereas data from the US Energy Information Administration show, the average cost of electricity is 10.5 cents per kilowatt-hour.
How Far Have Solar Energy Technologies Advanced?
If we compare the solar panels we have today to the first solar panels, we can see a huge advancement in solar energy technologies.
We started with 1% efficiency in the 19th century, which was not even enough to be considered a useful energy source.
Bell Labs made a significant improvement in the design of solar panels when they invented the first useful silicon solar panel with 6% efficiency.
Over the last decade, the growth of solar technology has been exponential.
The future is very bright for all renewables as they’re expected to increase 50% over the next five years.
Likewise, solar energy is expected to account for 60% of this growth, according to a recent report from International Energy Agency (IEA).
Apart from better efficiency, reduction in the price of solar panels and government tax credit are the major factors for this increase.
In this article, we covered everything about solar energy.
We have explained how solar energy converts to electricity in solar panels, starting from the sunlight until the alternating current powering our appliances.
Along the way, we learned about semiconductors and their different types, as well as inverters and their different types.
We also learned how solar panel technology has improved over time and how it is becoming much more affordable.