Solar energy has become very popular in recent years, its use has spread worldwide but solar energy how it works .
The sun provides enormous resources to generate clean and sustainable electricity without toxic pollutants or emissions that cause global warming.
Solar energy , the power of the sun, is a huge, inexhaustible and clean natural resource.
Solar energy production is a clean alternative to electricity from fossil fuels.
- no air and water pollution,
- no general global pollution,
- no risk of jumps in electricity prices,
- without risks to public health.
Solar energy how it works
Electricity from the sun sounds intriguing, right? In today’s article, we’ll take a closer look at how photovoltaics works and what path the sun’s rays have to travel so that we can use clean energy in our homes.
Photovoltaic energy is the process of generating electricity from free solar radiation. Currently, the development of photovoltaic energy is very dynamic and the sun is the third largest source of renewable energy in the world. Solar energy can be used to power small portable devices, such as calculators or clocks, lamps and traffic lights, and parking meters, as well as to heat rooms and heat water in residential buildings. Each of us can benefit from a natural source of energy, also to power our household appliances, facing constant degradation of the natural environment and constantly increasing electricity prices.
Where is solar electricity produced?
Solar energy how it works. Obtaining electricity from the sun is a process that takes place in stages. How does photovoltaics work? The basic element of the installation are the photovoltaic cells, which are combined into photovoltaic modules to be able to generate more energy (2) . A photovoltaic phenomenon occurs in cells, thanks to which the sun’s energy is transformed into direct current. Cells are systems built with semiconductor material that conducts an electrical charge as a result of external factors, including in the form of temperature or solar radiation. In cell production, the most widely used semiconductor is silicon. The group of modules that feed an inverter forms a photovoltaic panel (3) , while the element that allows the mounting of the panels on the ground or building is a support structure (1) , which at the same time must guarantee the stability of the entire system.
How does solar electricity get to our outlets?
The current generated in the modules is transferred to the inverter (4) , whose task is to convert it into alternating current with parameters compatible with those of our domestic sockets (7) . In addition, the investor controls the operation of our micro-plant. This means that it continuously adjusts the parameters of the electricity generated to the parameters of the home network, and also turns off when a fault is detected. It also monitors all the parameters that can be useful to analyze the operation of the photovoltaic.
What happens to the unused energy?
The bidirectional meter (5) measures the bidirectional current flow, that is, it counts the electricity produced by our installation and extracted from the electrical network (6) . It can happen that the energy generated by our micro-plant is too much or too little in relation to our needs. In the first case, the excess energy is transferred to the electrical grid and we can collect 80% of the energy we produce. It is related to the discount system for prosumers, that is, people who generate energy for their own use. For a photovoltaic installation, whose power does not exceed 10kWp, the ratio 1: 0.8 is applied under the discount system, which means that for 1kWh put into the grid, the owner of a micro-plant can collect 0.8 kWh. In the case of installations with a capacity between 10 and 50 kWp, we pay in the ratio of 1: 0.7 – the 1 kWh that we give allows us to receive 0.7 kWh. In situation,
We already know how photovoltaics works. It is time to take a closer look at the structure and operation of the largest star in our micro-plant: photovoltaic cells. It is there where the photovoltaic phenomenon takes place, thanks to which the energy of solar radiation is converted into electricity.
What are photovoltaic cells made of?
As we wrote earlier, photovoltaic cells are made of a semiconductor material, most often silicon, that changes from an insulator (a body that does not conduct electricity) to a conductor under the influence of the power supply. Due to the degree of ordering of the silicon crystal structure, there are three types of cells:
Monocrystalline silicon cells with a very orderly structure and devoid of many defects. Photovoltaic cells made of this type of silicon are characterized by the highest efficiency of converting solar energy into electricity (the so-called efficiency). The efficiency of the monocrystalline module is at the level of 15-19%. In practice, this means that 15% of the energy from solar radiation that falls on 1 m 2 of cells is converted into electricity.
Polycrystalline cells that are characterized by a less ordered silicon structure and a greater number of defects. For this reason, the efficiency of polycrystalline silicon photovoltaic modules reaches 14-16%.
Amorphous cells , in which the silicon does not have the shape of a crystal and therefore has a very chaotic structure with a large number of defects. This has a direct impact on the low efficiency of the modules, which is only 9-14%.
Due to their high efficiency, monocrystalline and polycrystalline panels can be used successfully in installations built on the roof of houses or in gardens. However, we must remember that monocrystalline cells are much more difficult and therefore more expensive to manufacture than cells made from polycrystals. For this reason, it is the latter that are most used in our domestic photovoltaic installations.
Solar panels: what is their structure and basic parameters?
Individual photovoltaic cells have a power ranging from tens of milliwatts to several watts. Therefore, we cannot power devices larger than small electronic devices from a cell. Therefore, to generate more energy, cells are assembled into modules. The cells that make up the module are laminated with EVA (3) and PET (5) sheets , placed under the tempered glass (2) and mounted on an aluminum frame (1, 6) . This ensures the durability of the structure and protection against damage. Another element that makes up the module is a junction box (7) with cables that allow us to connect several modules to each other. The modules connected in this way form a photovoltaic panel .
All photovoltaic panels have a set of mechanical and electrical parameters that define the conditions of their operation and assembly. We can find them in the catalog sheet and on the characteristics plate located on the back of each photovoltaic panel. Let’s take a look at some of the most important parameters based on which decisions are most frequently made regarding the choice of panels for a photovoltaic installation.
Mechanical parameters of photovoltaic panels.
The mechanical parameters mainly include: dimensions, resistance and weight of the modules that make up the photovoltaic panel. When comparing modules of the same power, we must strive to choose the smallest and lightest solutions. Thanks to this, we will not only be able to more easily place the solar panels on our roof, but it will not overload its structure either.
The mechanical resistance, in turn, tells us what is the maximum load value of the module with snow and wind that will not damage it. Snow cover pressure is simulated by loading the panel from the front, while loading the panel from the rear allows wind pressure to be tested. The optimal resistance of solar panels is estimated to be 5400 Pa at the front and 2400 Pa at the rear. In practice, this means that neither the 130 km / h wind speed nor the one meter layer of fresh snow should damage our panels. When comparing offers from individual manufacturers, avoid PV panels that have worse parameters than the stated 5400/2400 Pa.
Electrical parameters of photovoltaic panels.
The electrical parameters, in addition to the semiconductor material from which the photovoltaic panels are made, largely depend on atmospheric factors, such as: intensity of solar radiation, temperature, wind speed, air humidity, air pollution, etc. will be the parameters of each panel tested under strictly defined laboratory conditions:
- solar radiation with intensity – 1000 W / m 2 ,
- solar panel temperature – 25 ° C,
These conditions are called Standardized Test Conditions (STC) and the power of the panels obtained with these parameters is called Maximum Power Point ( MPP ). This parameter tells us how much electricity a given panel will produce under given conditions and for a given specific area in m 2 .
Being at maximum power, it is also worth mentioning another parameter, which is the power tolerance of the photovoltaic panel . Determines how much the result can differ from the maximum power of a given panel under laboratory conditions. If the tolerance values are positive, we have nothing to fear. It just means that our solar panels can reach more power than indicated by the manufacturer. On the other hand, PV panels with a negative power tolerance value should be avoided because manufacturers have probably overestimated their performance.
In fact, it is rare that atmospheric conditions are exactly the same as the test parameters in laboratories. For this reason, in addition to maximum power, manufacturers also provide power in NOCT (normal operating cell temperature) on their catalog cards . This value corresponds to the power that photovoltaic panels reach in conditions similar to those that occur after installing them on the roofs of our houses, that is:
- solar radiation with intensity – 800 W / m 2 ,
- solar panel temperature – 45 ° C,
- wind speed – 1 m / s.
It is assumed that the closer the power value in NOCT is to the power value in MPP, the better.
The power of photovoltaic panels is not the only parameter that we must pay attention to when choosing them. Another important piece of information is efficiency . It tells us how much energy from solar radiation that falls on 1 m 2 of a cell is converted into electricity. Solar panels with higher efficiency and lower surface area will produce the same amount of energy as panels with lower efficiency, but with a larger surface area. For this reason, it is worth choosing products with greater efficiency. This will allow to place fewer modules on the roof of our house.
The next two important parameters are related to the temperature that the photovoltaic panels reach during their operation. It is the temperature power factor and the module temperature under NCOT conditions . The first indicator determines by what percentage the power of the panel decreases with its temperature increase in each 1 ° C in relation to the temperature of the test conditions, that is, 25 ° C. On the other hand, the second parameter tells us what temperature will reach the photovoltaic panel when it operates in conditions more similar to the real ones. When comparing offers on the market, choose those solar panels for which the temperature power factor is close to zero, and the module temperature under NCOT conditions is less than or equal to 45 ° C.
Is there anything else I need to pay attention to? Photovoltaic panels lose their efficiency over the years. In the first years of its operation, these losses are at the level of 2-3%, while in the following years they amount to around 0.6% per year. When deciding on photovoltaic panels from a specific manufacturer, check their linear power guarantee . Determine the minimum efficiency of the panel that you will achieve in a given period of time. The market standard is guarantees with an efficiency of 80% after 25 years of use of photovoltaic panels. This means that if the efficiency of your panels falls below 80% at the end of 25 years, you have the full right to claim compensation. At the same time, remember that the linear power warranty is not the same as the product warranty. . If your solar panels stop working, only the last type of warranty gives you the right to claim your rights.
How do solar panels work? The photovoltaic phenomenon in a nutshell.
The following describes the Solar energy how it works process. We already know that depending on the type of semiconductor they are made of, photovoltaic panels can more or less effectively convert solar energy into electricity. We also know the parameters from which we can verify what type of panels will be most effective. But how does the photovoltaic phenomenon occur in them and what is it about?
To better understand the photovoltaic effect, let’s first discuss the construction of a photovoltaic cell. The cell consists of two semiconductor layers. One of them is made up of atoms with a higher number of electrons in the last shell, so it has a negative charge ( n-type shell ). The second is made up of atoms with empty places after the electrons, the so-called holes ( p shell ). This layer has a positive electrical charge. At the boundary of these two shells, the n-type atoms “give up” their additional electrons to the p-type atoms, filling their gaps. This creates a pn junction consisting of atoms with a neutral electrical charge.
The production of electricity in a photovoltaic cell takes place only when sunlight falls on it. The rays must be perceived as a stream of particles (so-called photons) with a portion of energy. This energy, which reaches the cell, is absorbed by the electrons in the last electron shell of the silicon atoms at the pn junction. As a result of the energy supplied, the electrons are “stripped” from the layers and circulate freely through the semiconductor material in the n-type layer.
At the same time, in the p-type layer, the number of atoms with holes increases. This leads to the difference in charges in both layers, the so-called Voltage. The free electrons in the n shell tend to refill the holes in the atoms in the P-type shell. However, the pn junction, which acts as an “insulator,” effectively prevents them from doing so. Connecting the receiver to the photovoltaic cell and thus closing the electrical circuit will cause the flow of free electrons towards positively charged atoms. This orderly movement of electrons is electricity! Its intensity is proportional to the intensity of solar radiation as well as to the surface of the photovoltaic cell.
What happens next? The resulting direct current goes to the inverter, which converts it to alternating current. Thanks to this, it is possible to supply electricity to our appliances.
Ugh … We’ve come a long way. We learned how photovoltaic energy works, so we have nothing else to do but enjoy the solar energy that powers the equipment in our house!
We have reached the end of the article Solar energy how it works, I hope the concepts have been understood.