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Know when to use a series or parallel solar PV array

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Know when to use a series or parallel solar PV array

2024-11-26

 

Series or parallel configuration
Similar to placing batteries in series, there is a composite voltage after each connection. If one battery is connected to the negative terminal of the other, then two 1.5 volt batteries will produce a total of 3 (1.5 + 1.5) volts if the positive terminal is connected one after the other. The more series in series, the moving voltage will be transmitted behind the link. The amperage, however, will be the same and limited to the cells with the highest resistance in the chain.

In a solar photovoltaic panel, all solar photovoltaic cells are connected in series to generate enough voltage for charging the battery system. Keep in mind that under standard test conditions, each solar cell typically generates about 0.5 volts.

In a solar PV array, many people want to connect their panels in series to generate the highest voltage acceptable to a solar charging controller or inverter. In the MPPT controller it will be up to 150 volts DC. In a solar PV setup, it's called a "string," like a series of Christmas lights strung together.

Advantages of series connected panels:

Allow smaller wires: If you increase the voltage, be sure to know that the wires will carry more power on smaller wires. Ever wondered if small wires hanging from the electricity utility grid (National Grid) could provide enough electricity to power a city? These techniques use very high voltages, typically 33 kV (33,000 volts), which can be as high as 765 kV (in the transmission lines of power stations). Since the voltage is high, the amperage on the wire will be small, with the power (power) equal to the potential difference (volts) multiplied by the current (amperage). Smaller size wires are usually cheaper than having larger wires.
Reduce loss during transmission: At high voltages and low current amperes, the heat loss during wire transmission will be smaller. It will enable solar photovoltaic systems to work more efficiently.
Allow longer wiring, from solar photovoltaic panels to other equipment: If the voltage is higher, the amperage is lower, and the heat loss during transmission is lower, then longer wires can be allowed to connect the equipment. Panels can be very hot in sunlight, and this heat is not conducive to the long-term use of other devices, such as inverters, charge controllers, and batteries. Longer wiring will allow this heat-sensitive device to be placed in the shade or in a cool room.
For MPPT controllers: MPPT - Maximum Power Point Tracking is an excellent device for efficiently utilizing the maximum power output by digitally tracking the output of a solar photovoltaic panel and providing the correct voltage to the rest of the system (battery and load). MPPT can generally accept higher DC voltages (typically up to 150 volts DC, depending on the manufacturer), thus allowing the use of larger solar PV arrays.
Disadvantages of series connected panels:

A weak link can reduce the continuity of the entire system: like a string of Christmas lights, a broken bulb can cause part of the Christmas light to go out. Similarly, if one of the panels in series has a higher resistance due to panel failure or due to partial shading of the individual PV panel, the entire string will be affected and the overall performance will be dragged down, according to the limitations of the weakest unit. One solution is to apply a bypass diode to allow the current to bypass the worst-performing panel, which is due to the local coloring of that individual panel. More panel partial shading also results in an effective reduction in overall efficiency. Due to the semiconductor nature of diodes, there is some voltage drop when passing through each diode.
Higher voltages are dangerous: Since voltages add up with each subsequent panel, professionally installed high-voltage systems are often required for greater safety.
Advantages of parallel connected panels
However, some people prefer parallel configuration. Similar to a parallel battery pack, all the positive electrodes are connected together and the negative electrodes are connected together. This will effectively increase the amperage and transmit more power, even if the voltage is the same.

Five 12 volt 5 amp solar photovoltaic panels will produce 12 volts 25 amps if connected in parallel, or 60 volts 5 amps if connected in series.

Advantages of parallel connected panels:

Allows handling of safer voltages: Most electronic devices have a voltage range of 5 volts, 12 volts, or 24 volts. In most automotive electrical systems, the standard voltage is 12 volts, and we can find everything from lights to stereo sound, as well as motors that run at 12 volts. Even if the car battery voltage is 12 volts. All these voltages can be handled "safely" by a non-professional. When the shock is known, the body's resistance will come into play. At low voltages below 25 volts (or less than 20 volts), there will be a higher body impedance shock (most people (close to 50% of the population) will have a body impedance of 3,250Ω when subjected to a 25 volt shock, and the impedance decreases to 1350Ω volts when subjected to a 220 volt shock). While currently the main culprit in causing tissue damage, higher voltages increase the chance of a shock.
Better match with PWM controller: If the panel voltage output and battery voltage are nearly the same, the charge controller will be more efficient than those systems where there is a severe mismatch between the panel and battery voltage, because there is no DC-to-DC converter like the MPPT controller. PWM controllers are cheaper, so they can be affordable for common DIY solar applications. The PWM controller will reduce the voltage from the panel voltage output and allow the undervoltage battery to charge and load operation.
Total solar PV output is not affected by weak links: since each solar PV panel has a common connection, each panel will operate at its own pace. Unshaded panels will operate at high efficiency, while shaded affected panels will perform independently with reduced efficiency. However, it is still recommended to use a blocking diode to ensure that all the current in the panel goes in one direction.
Disadvantages of parallel connection panel:

Need to use bulky wires: Since the amperage output of solar panels is added up, the final amperage output will be higher, which requires a larger size of wire, which is more expensive and larger. This also indirectly increases the upfront cost of installation.
Less efficient when running with longer cables: heat loss during transmission is higher due to excessive current. If you intend to run longer wires, which also indirectly increases the upfront cost, you will need to further increase the size of the wires.
Mixed series and parallel configurations
To eliminate the advantages and disadvantages of both configurations, it is recommended to mix the two to get all the advantages. You can string together multiple solar photovoltaic panels for parallel configuration. In this case, you get better energy output, lower wiring costs, and you can achieve better results with the panel partially shaded.

Mix solar photovoltaic panels with different power ratings
When multiple panels need to be connected together, it is recommended that similar solar PV modules (with the same voltage wattage rating of the same brand) be connected together to prevent a decrease in overall efficiency due to weaker panel restrictions. Again, we do not mix old and new batteries together when in use.

In the series series, low performance panels will have a significant impact on the entire series. Panels with lower wattage typically have lower amperage ratings and smaller cell sizes. For example, when 10 amp panel, 5 amp panel and 1 amp panel photovoltaic cells form a series series, the entire system will have voltage accumulation, but the net current is only close to 1 amp or minimum short circuit current operation (1 amp panel becomes the limit).

In a parallel configuration, different power control panels may also influence each other, as each panel in a parallel configuration will have a different resistance and potential difference. If one panel produces a much higher voltage than the other (for example, a 24 volt panel mixed with a 12 volt panel), the lower voltage panel will exhibit significantly reduced performance because the lower voltage panel cannot produce a competing potential difference to effectively inject current into the system.

When you have different rated panels on hand, the recommended approach is to connect each similar panel to a separate inverter (such as a micro inverter) to get the maximum panel efficiency of each PV.