Connecting Solar Panels in Parallel
Welcome to this information page Mppt Solar. In this page we will teach how to connect in parallel multiple solar photovoltaic panels so as to obtain an output increase of the current available, while maintaining the rated voltage. We also explain the difference between a parallel connection of two or more photovoltaic panels equal and parallel connection of two or more solar panels with different technical characteristics. Finally we will provide valuable and practical tips for getting a really efficient system, free from damage due to faults or short circuits that can occur on individual photovoltaic panels.
Well, Here we go! The connecting several panels in parallel arises from the need to reach certain values of output current, without changing the voltage. In fact, by connecting more solar panels in series we increase the voltage (keeping the same current), while connecting them in parallel we increase the current (while maintaining the same voltage).
Parallel connection of two identical solar panels
If we have two solar panels of the same voltage and power, the connection is very easy. As is clearly visible in the figure below, it will be sufficient to connect the positive terminal of one panel to the positive pole of the other, and connect the negative terminal of one panel to the negative terminal of the other. In series to each panel we inserted a blocking diode. Later we discover the reason for these diodes.
This type of connection is very efficient if the following conditions are met:
1) put the panels next to each other and oriented in the sun at the same angle
2) check that the panels do not shade each other and are far from possible causes of shading
3) choose an appropriate section of the electric connection cable according to the distance of the panels
4) uses of junction boxes to connect neatly between the terminals of the panels
What happens in case of shading?
First, it is good to know that the tension that we find across a photovoltaic panel shaded condition does not depend on the irradiation of the same, but the load conditions in which 'subject. In fact, a panel shaded and 'still perfectly capable of receiving the portion diffuse solar energy and therefore can still offer a working voltage and positive value of almost identical to when and' fully irradiated (and 'the current can produce that decreases proportionally to solar radiation). It is understandable, therefore, that in a solar photovoltaic system on-grid it's important the choice of the inverter, that will have the task of finding the MPPT maximum power point of the string is in a position of full radiation, which provided shading.
In a system stand alone (off-grid) instead of this function is performed by the mppt solar charge controller. Then, what is the blocking diode? The blocking diode is good insert to protect the entire string from possible faults or short circuits that can occur on the individual panels of the string. It 'also a good thing during the design, choose solar panels that are already present in them at least three bypass diodes to prevent the most of the energy losses due to shading. In this regard, the reverse currents in the solar panels, you should know that recent studies of the prestigious research center Fraunhofer Institute for Solar Energy Systems ISE, have shown that the solar panels are able to withstand reverse currents up to seven times larger than the rated current of short circuit without suffering any damage.
Which diode to choose?
In the market there are many different types of diodes. The best kind of diode for photovoltaic applications, is the Schottky diode. This type of diode has the characteristic of having a very low threshold voltage (of the order of 0.35 V 0.6 V against the common diodes), which ensures a very low power dissipation. I recommend, pay attention also to the choice of the length and the section of the electrical cable increases because of connected panels, also increases the current and therefore the dissipation of energy in it. For high currents requires a cable of suitable section. For more information about choosing cables visit the page on the electrical wire sizing.
Parallel connection of two solar panels of different power
If we have two solar panels of the same voltage but with different power, no problem, you can easily connect in parallel. If instead the two photovoltaic panels are with different both power and voltage, then it is not possible to connect in parallel, because the panel with lower voltage would act as a load, and would begin to absorb current, instead of producing with the related consequences . If, however, we have a panel of 12 and two 6V, then you can connect the two panels from 6V in series and then connect the series obtained in parallel to the panel 12V. This latter type of connection, however, is to the detriment of efficiency. E 'therefore essential, before making a parallel connection, double check the voltage of the photovoltaic panels. Here is a very clear picture of how to connect two different panels in parallel.
Pay attention to the current!
You can connect multiple solar panels with this method, but you have to pay attention to current values. If your output value is greater than 70A, your panels and your system may be damaged and issues related to power management. To avoid this, it is used to connect the panels in series-parallel, so as to increase both voltage and current simultaneously. For example, if we were to connect in parallel by six panels 10A, we will output a current high enough, ie 60A. To solve this problem and to optimize the energy efficiency of the entire system, it is advisable to connect two panels in series (resulting in a doubling of voltage) and then connected in parallel to the three pairs previously connected in series (so as to have doubled and tripled voltage current). In the figure below you can see the outline of this connection. This type of connection is frequently used for installations of considerable power.
In an off grid photovoltaic system, the choice of the total power of the system and the tension of the battery bank must be carefully considered in the design phase.
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Photovoltaic Solar Energy
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