Who would not love the idea of having their own energy and not being reliable in a national system? Just think about not having to pay the electricity bill every month and you will definitely get the idea. The world of advanced technology designed a device that makes all this possible: the solar panel! Energy independence and keeping the environment free from pollution are not just a distant dream in today’s reality. We can produce our own electricity in a simple and efficient way using state-of-the-art solar panels.
Being able to understand the operating principles of these devices may one day be one of the most valuable skills you have. Imagine a global natural disaster that devastates the world and changes everything. There is no industry, there is no fuel, the world economy is in total chaos and there are only few survivors left.
After the initial impact, you will want to rebuild the world, but without energy, things can be exponentially more difficult. If you know how to build a solar panel and how to store and use the resulting energy, you can have electricity and use the technology in your favor.
Today we are going to draw your attention to the mechanisms that operate within said device. We are going to cut the solar panel and discover what makes it work. But first, let’s see what is the real definition of this incredible device.
Solar panels: definition and fundamentals.
The scientific name of these devices is photovoltaic And basically it means light for electricity. Actually, this is the simplest definition anyone can offer: solar panels are devices that convert light into electricity. In general, they are called solar because our main and most powerful source of light is the Sun, but it is not the only source of light to which these panels can react.
The basic principle is simple: these solar modules use the energy of sunlight (or photons) to create energy through the photovoltaic effect, which is a phenomenon involving physical and chemical reactions.
To demonstrate how efficient and advanced today’s solar technology is, you should know that NASA uses photovoltaic energy in its ships to ensure that it will always have the necessary power to deploy the missions for which it is sent into space. The only problem with these devices is that they should always point towards the Sun to receive the maximum possible light.
This is one of the absolute requirements of a solar panel: exposure to light. If the device does not receive direct light, its efficiency is lower, so when it comes to home systems, positioning is extremely important. In addition, when it comes to homes, solar devices are classified into three main categories:
- solar hot water panels – these systems use solar energy to heat the water required in the home;
- thermal solar collectors – This is a device used to capture solar radiation of infrared or ultraviolet wavelengths that is converted into electricity;
- photovoltaic – These are the panels that are electrically connected and mounted on a support structure.
Now that we know what a photovoltaic device is, it’s time to see how it really works.
The science behind solar devices.
The science is quite simple: when light particles or photons hit a solar cell, they separate the electrons from their atoms, thus creating a flow of electricity. And now, we have introduced a new element in the discussions: the solar cell or the photovoltaic cell. These are small units that come together in a special arrangement, make a solar panel. So, in conclusion, a solar panel is a solar cell collected or organized.
Since we have just discovered that all solar devices are based on small units, we consider it right to start with the small particles first and then move on to the science of the entire device. Therefore, we are going to discuss the solar cell below.
How solar cells work: fundamentals and structure
In short, a solar cell is made of two pieces of a semiconductor material placed one above the other, as in a sandwich. The most commonly used semiconductor material in this care is silicon due to its property of having electrical and metallic insulating properties. Silicon is combined with other materials to create the necessary charges so that the electric current can be created. This is basically the reason why a solar cell is a sandwich, because it needs to create an electric field.
For this to happen, each piece of the cell must have separate opposite charges, so the silicon is mixed with other materials. Producers use phosphorus for the upper layers to add additional electrons and create a negative charge (type n), and boron for the lower layer to reduce the number of electrons and create a positive charge (type p). When placed on a sandwich, the two pieces of silicon, charged differently, create a union through which the electrons can move.
All this creates an electric field between the layers of silicon and when a photon hits one of these cells, a small portion of its energy is trapped in the cell, releasing electrons while the electric field pushes it through the junction, towards the plates conductive metal. Placed on the side of the solar cells. All these electrons are collected and sent through cables to power their devices.
The best analogy of this whole explanation is a game of pool: the white ball is a photon and all the other balls are atoms waiting to be hit. When the white ball hits another ball, the electrons are set in motion and transferred through wires (the tubes under the table) until they reach their target.
As you can see, the theoretical process is simple and governed by simple laws, but in reality things are a little more complicated.
Special properties of silicon used for solar cells.
You may wonder what makes silicon such a special material that most producers like to use it. Well, we are here to explain things thoroughly, so read on if you want to know more about solar cells and the materials they are made from.
In crystalline form, silicon has some special properties that are due to its special structure of 14 electrons. These electrons are arranged in three layers, two of which are complete. It is because its outer layer is incomplete, a silicon atom will always try to join with the 4 closest atoms. This is the property that really forms the crystalline form that is so important for photovoltaic devices.
Because silicon in its pure crystalline form is not a good electrical conductor, producers add other materials to the mixture (as explained above). We already specified that phosphorus is one of the other aggregated elements and here we explain why: phosphorus has 5 electrons in the outer layer and, as it still joins with 4 of its neighboring silicon atoms, there is still one left. This means adding a negative charge to the silicon that is used for solar cells: having extra electrons to play with.
When energy (such as light or heat) is added to the material, some electrons will be released because there is no strong bond to hold them in place. When they leave their places, a hole remains in the structure and they ask around, looking for a new hole. This is what really forms an electric current.
Boron is another element added to the mixture and it has only 3 electrons, which leaves holes in the structure. This helps to charge the silicon positively. The process of nailing pure crystalline silicon with other elements is called doping and is used to create much better conductors.
Studying the anatomy of a solar cell.
We already specified that the two pieces of silicon should be joined and organized in a sandwich type structure, so that an electric field can be formed. Let’s see what this means and why we need it.
When the two pieces of silicon (type n and type p) come into contact, all free electrons on the n-type side will want to enter the free holes in the p-type part. I could think that there is no way to form an electric field if the electrons on one side are transferred to the hole on the other side, and it would be right. Even so, at the junction between the two pieces of silicon, a barrier is formed and it is difficult for the electrons to travel to the other side.
When an equilibrium is reached, there is an electric field between the two silicon pieces of the solar cell. This field also has an address: from the P side to the N side and never reversed. This allows the free electrons on the P side to move on the N side, which means that we will have electrons on one side and holes on the other.
A photon with enough energy must interrupt exactly one electron and this means another hole in the P side. This leads to the creation of a path, and we can use it by adding external elements to the cell to direct this flow of electrons to the P side, where they will join with their holes. This is actually what the electric current provides and the field causes voltage. This is what we need to have power for our devices: current and voltage.
Other necessary elements for the solar cell.
So far we only discuss the most important parts of a solar cell: the silicon-based parts and their actions. Even so, to receive energy from a photovoltaic cell and make sure it works at maximum capacity, we will need some more elements:
- Metal plates – these are attached to the side of each cell to create the route of the stream;
- Anti-reflective coating – Silicon is sometimes so bright that it causes photons to bounce to the right, without having the opportunity to release an electron. This means a lower efficiency for the cell so a coating is applied.
These are the main things that one should know about solar cells. With the information included here, you could produce your own solar cells in case the situation requires it. This is also a fun DIY project that can help you reduce your electricity bills.
How do solar panels work: efficiency and process?
Solar panels or PV modules are no more than a series of individual solar cells connected together to achieve a certain level of current and voltage. Since a single cell can not produce enough energy to power a demanding consumer, photovoltaic modules are the perfect solution.
The solar cells must be protected from the elements to produce energy effectively and since the photovoltaic modules are installed outdoors, a protective glass cover must be added. So, to summarize, a solar panel is a gathering of solar cells, organized and connected to each other and placed in a sturdy frame, covered with a glass plate. Pretty simple, right?
Efficiency of photovoltaic modules
Now that we have learned about what makes them work, let’s see how these photovoltaic modules can help us save the money we pay in electricity. Would not it be fun to be able to consume everything you need without thinking about how much you will have to pay?
The first thing we are going to discuss is efficiency, that is, the actual amount of solar energy absorbed by its panels. You will be surprised to know that the efficiency is not 100%, in fact it is not even close. For example, in 2012, the efficiency of photovoltaic modules, intended for domestic use, was between 12% and 18%. However, the numbers have changed since then and thanks to the innovative materials, the efficiency managed to surpass 50% in 2015 for commercial photovoltaic modules. However, most of the photovoltaic modules that are on the market today do not have an efficiency higher than 20%.
This does not mean that the panels do not do their job correctly; it only means that only 20% of the total amount of solar energy that reaches your panel will be collected and used to generate electricity. That is why positioning is very important for solar panels. So, why only 20% (or less), why not absorb all the energy? Well, maybe in the future we can use the energy of light 100%, but for now we are limited by the light itself.
We all know the fact that light is not uniform and that it is made of separate wavelengths (the colors we see in the rainbow or when we place a beam of light through a prism). Actually, this means that different wavelengths will have different energy levels. Given the fact that a certain level of energy is needed to free an electron, some photons will pass through the solar cell without having an impact on it. All this led scientists and manufacturers to understand that only certain wavelengths can be really effective in releasing these electrons.
The required amount of energy is expressed in a unit called volts of electrons (eV) and depends on the material used to create the cell. For example, the amount of energy required for crystalline silicon is 1.1 eV. This is called, in scientific terms, the energy of the band gap for the specific material.
Now, if a photon is too powerful, then we lose the extra power, so it is necessary to establish this band interval. Other losses occur with the transport of electrons to the target destination due to the fact that silicon is a semiconductor. To minimize these losses, manufacturers began using metal grids to shorten the distance that electrons must travel.
The process of feeding your house with solar energy.
Now that we have discussed several internal aspects of solar panels, it is time to see how they actually work in a home.
Orientation of photovoltaic modules
As we have mentioned before, the panels must be oriented towards the sun to produce the maximum amount of energy of which they are capable. In addition, the angle of inclination is extremely important, which is why the roof of your house is not always the correct answer. The photovoltaic modules should always be oriented towards the south and the angle of inclination should be equal to the latitude of their area (as much as possible).
The modules can also be used to maximize energy according to the time of day: more energy in the morning or in the afternoon. Make sure there is no shadow around the panels, because even a shaded cell can change the efficiency of the entire module.
Decide on the right size
A larger module will definitely produce more power than a smaller one since it incorporated more solar cells. Even so, a larger module will occupy more space on your roof or in your garden and will be more difficult to maintain. Also, if you are not using all the energy that your module is capable of producing, you will be wasting it and this is not what you want.
So, how do you make sure you have energy throughout the year with all the unpredictable weather and all that? Well, the answer is not very difficult. You just have to do some calculations:
- Design for the worst month: review the weather data published in recent years and see how much sunlight had the worst moth. You must design your system according to this data if you want a constant and efficient energy flow;
- Calculate your needs: collect the electricity bills of recent years and calculate a monthly average. This is the minimum energy you need to get with the solar panels during the worst moth of the year (in climatic terms).
A little trick: To achieve a certain level of voltage, you can wire some modules in series.
Days without sun and living completely from the network.
We all know that there are days when the sun does not shine or shines too little to produce enough energy for the whole house. This is really the main problem when it comes to being completely independent on an energetic level: you never know when a rainy day can ruin everything for you and your family.
However, the situation is not completely hopeless, as there are also ways to solve this problem:
- Batteries to store your energy. – You must use a special type called deep cycle batteries. These are able to discharge a smaller amount of energy and still maintain a long life. They need special maintenance and will not last a lifetime; You must replace them every few years. Also, if you want them to stay longer, you will need a charge controller so you do not overload them.
- Backup generators – for when your energy income is low. This means that you will really have to buy the generator and the necessary fuel and make sure you can support your whole family for at least a few days.
- Connecting to the electrical network – In this way, when you have too much energy, you can sell it to the national system and when yours is too low, you can buy it. For this, you will need special equipment and you must sign a contract with the national provider. Local laws may vary from region to region, so make sure you get the correct information before you start buying equipment.
Feeding your appliances.
Now that you have solved the problem with storage and days without sunlight, you must solve another one. The electric current produced by your PV is direct and your devices are not made to be fed with it. You will need to buy an inverter and all the necessary equipment to install it in order to use solar energy to power your home.
It may seem like a lot of work and it can be a great investment, but over time, you can get it back. Only the idea of living completely outside the network and not being dependent on a national system that charges you every month with overvalued energy should be a very strong motivation.