The 3 main types of photovoltaic panels are monocrystalline, polycrystalline and thin film. Discover features and differences
The types of photovoltaic panels currently present and marketed on the market are:
- monocrystalline panels;
- polycrystalline panels;
- thin film panels.
They differ from each other in characteristics and performance according to the type of photovoltaic cell that make them up. But what are the differences between the two? Let’s discover together all the features to choose the best model for your system.
To avoid making any mistakes that could compromise the photovoltaic panel performance and production rates, I really suggest getting hold of the libraries and design wizards of a professional photovoltaic calculation software that can guide you in the sizing of the PV panels anc omponents providing powerful drawing and electrical connection diagram generation tools too.
What are photovoltaic panels?
A photovoltaic panel is a set of multiple photovoltaic cells connected in series or in parallel and positioned on the same support structure.
Photovoltaic systems are characterized by their modularity, which offers a large scale of use. Each element therefore consists of many smaller elements:
- the elementary electrical components that transform solar radiation into electrical energy are the photovoltaic cells;
- photovolataic solar cells join together to give life to the PV panels;
- multiple panels connected in series form a string;
- multiple strings connected in parallel, in order to generate the desired amout of power form the photovoltaic generator.
The modules for forming the panels can be connected through different configurations; depending on how they are connected to each other, they can increase in intensity or voltage.
Once the power to be installed has been determined, the the number of panels and their arrangement is also variable within the strings. Calculation and sizing is a delicate process, just as the other many factors such as the solar radiation value of the installation site and location and the degree of solar exposure which also needs to be considered. That’s why I’d really suggest using a photovoltaic calculation software capable of calculating and quickly sizing all the elements of the PV installation.
How many types of photovoltaic panels are there?
The different types of photovoltaic panels are classified according to the type of photovoltaic cells that form the modules and that vary in turn depending on the crystal characterized in:
- monocrystalline cells;
- polycrystalline cells;
- amorphous cells.
With reference to these cells, these 3 main types of solar PV panels are produced:
- monocrystalline panels;
- polycrystalline panels;
- thin film panels (amorphous).
Monocrystalline photovoltaic panels
Monocrystalline photovoltaic panels are thin slabs generally consisting of 30-70 photovoltaic cells welded together and covered by a protective glass and an external aluminum frame.
They are composed from are homogeneous – monocrystalline cells – and obtained by slicing silicon ingots through the Czochralski system. This is a process in which a crystal seed is immersed in a silicon melt and from which a single macro crystal is generated forming a silicon ingot.
These have a dark blue, almost black colour.
Monocrystalline panels are finally quite sensitive to shading, even partial, but they work very well if the sun’s rays are perfectly perpendicular to their surface. These are the most expensive type of panels but, being seeing as they are formed by cells of a single crystal oriented in the same direction, they have higher efficiency in terms of converting the solar energy and also have greater production levels compared to the same surfaces.
Polycrystalline photovoltaic panels
Polycrystalline photovoltaic panels are also very common because they have characteristics that are completely similar, but not coincident, to single-crystalline panels.
They consist of the cutting scraps of monocrystalline ingots and are formed by polycrystalline silicon cells formed by more randomly oriented crystals with a chaotic structure.
This disorderly structure makes performance a little lower especially if hit perpendicularly by the sun’s rays. However, this imperfection also represents their peculiarity: they are able to make better use of sunlightduring the day. This type of panel, just like the previous type mentioned earlier, is particularly sensitive to shading, even if partial, which could cause sudden or temporary drops in performance to the entire system.
They have an iridescent blue colour.
Thin-film photovoltaic panels
Photovoltaic panels with thin-film cells are made of amorphous silicon or cadmium telluride and do not have a crystalline structure.
They are formed by a layer of glass or plastic surfaces on which a layer of silicon with a very small thickness is uniformly applied. Visually, they do not present themselves as square cells that draw the surface, but appear as a plate of a uniform dark color.
A characteristic for which they are known by is their versatility: they are used in various contexts of architectural integration, urban furniture or structural elements of buildings.
Among the advantages of thin film, they are known for working well with diffused light or with high temperatures. In addition, thin-film panels are the cheapest on the market, although their energy efficiency is lower.
What are the differences between polycrystalline and thin-film monocrystalline photovoltaic panels?
The main difference between photovoltaic panels is the efficiency or photovoltaic solar panel efficiency , being the ratio between the energy produced and occupied surface .
More specifically, the most efficient photovoltaic panels are those that need a lower surface to generate the same amount of energy with the same radiation, temperature and other external operating conditions.
Among these we have:
- monocrystalline panels have a greater efficiency, ranging between 15 and 20% and to produce 1 kWp of power they need about 6 m² of installation space;
- polycrystalline photovoltaic panels have a lower efficiency and require a larger surface area: for the production of 1 kWp of power they need approximately 8 m²;
- thin film panels have a production efficiency of about 6% and need roughly 11 to 13 m² to produce 1 kWp of power.
Considering the efficiency under various temperature conditions we have that:
- monocrystalline silicon panels perform better at low temperatures and are more efficient than polycrystalline modules in the presence lower solar intensity;
- polycrystalline panels produce more energy at higher temperatures, as they manage heat better;
- thin-film photovoltaic panels have lower efficiencies but have the advantage of working better in conditions of high temperatures or diffused light.
Another substantial difference regards their cost:
- Solar photovoltaic panels are produced using monocrystalline silicon which also cost more to produce;
- polycrystalline silicon photovoltaic panels generally have a lower cost compared to monocrystalline silicon panels;
- thin film panels are the cheapest on the market.
From an extrinsic characteristics point of view:
- monocrystalline panels are black and have an orderly structure;
- polycrystalline panels are iridescent blue and have a much more chaotic structure;
- the thin film panels do not have a particular cell structure but, compared to most traditional technologies, they have a better versatility of use.
Solar photovoltaic panels can also be compared with each other based on some typical electrical characteristics:
- voltage at maximum power;
- current at maximum power;
- short-circuit current;
- open-circuit voltage;
- maximum system voltage, the maximum voltage to which that module can be subjected;
- temperaturecoefficients, losses that can occur in the panel depending on the temperature variation.
These values should be taken into account when choosing the inverter to connect to the photovoltaic solar panels. In order for the system to function correctly, electrical coupling checks must be carried out between the inverter and the panels connected to its inputs. I recommend you get hold of this photovoltaic software available to try for free and that can provide you with all the necessary tools to address the electrical checks necessary for a correct PV system sizing.