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In this article for solar panels we are going to exemplify the calculation of the solar panels. necessary for an isolated/Grid connected solar panel system
If what you are looking for is the calculation of panels for a self-consumption installation in Africa , then better read our article on how many solar panels you need for a home with a self-consumption installation.
The structure of the article will present
It serves as an introduction that installing high quality solar panels is of vital importance for a power generation installation of this type. It pays to do a simple internet search looking for reviews and references before making a purchase.
We assume that you already know how solar panels work, and the fundamentals of photovoltaic solar energy. Otherwise, you can find plenty of information on our blog. Thus, to calculate the energy generated by a solar panel during one day (Epanel), we must use the following equation:
Ep = Ip × Vp × PSH× 0.9 [Wh/d]
That would be the energy generated by a single solar module, but if, for example, we want to know how much energy a photovoltaic self-consumption installation with several solar panels is going to generate, we would simply have to apply the following formula:
Power Generated = Iphotovoltaic × Vphotovoltaic × PSH × 0.9
The current, in this case, would be the maximum resulting from the association of the photovoltaic modules connected in parallel of each branch (string), and the voltage would be the result of the sum of the voltages of each branch (string) connected in series.
The electrical symbol that is usually used to graphically represent a photovoltaic panel is as follows:
In most photovoltaic projects, especially isolated solar installations and depending on the power of the installation, it will be necessary to associate several plates in series or parallel to obtain the desired voltage and current levels.
For the connection of photovoltaic solar modules, there are three possible options:
If there were no losses of any kind (hypothetical case), the diagram for connecting solar panels in parallel could be represented as follows:
Let’s consider that we want to have solar panels for a motorhome, made up of a branch with 3 panels in series with 37.45V voltage and 8.98A maximum current. If there were no losses of any kind (hypothetical case), the connection scheme of the plates in series could be represented as follows:
As we can see indicated in orange, at the output of branch (c), we will have the voltage resulting from the sum of each of the voltages of each panel that make up the branch in series (112.35V) and the current will be the same as that of one of the panels (8.98A).
Surely you are thinking, what happens if a panel breaks down and I have to change it for a different one? Well, let’s imagine that, since we can’t find the same panel on the market, you want to buy photovoltaic panels with the following specifications: 31.40V maximum voltage and 9.33A current.
What will happen when connecting this module in series with the other panels already installed, is that the entire branch (string) will start working at the current of lesser magnitude, in our case as the Solar World SW 290 module has a current ( 9.33A) greater than the modules already installed (8.98A), the installation will not be modified.
In the event that our module has a lower current than those already installed, it will affect the entire string and a drop in production will occur, therefore it is not recommended to use replacement modules with currents lower than those of the installed modules.
it would be the last configuration option that we can find, in this case it would be a configuration where we find branches with panels connected in series and, in turn, these branches, connected in parallel. This configuration is used when we must achieve very specific output currents and voltages, and then we “play” with the options that the different types of connection give us. Let’s see an example about it
As we can see in the electrical diagram, at the point (node) (c) of the first branch (string).we have the sum of the panel voltages and the unit current, at the point (node) (d).
which is the output of the system, we will have the same output voltage of each of the branches, but as output current it is the sum of the output current of each of the branches, since the two branches connected in parallel.
As a practical summary, let’s say that in series connections the total current (output) is equal to that of one of the panels that make up the branch (string) and the total voltage (output) is the sum of the voltage of each panel connected in series. In parallel connections, the total (output) voltage is equal to the output of each branch and the total (output) current is the sum of the currents in each branch.
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