Solar energy and solar panels are increasingly becoming an imminent part of your lives. Almost everyone is familiar with the concept of solar panels and their working. However, apart from solar panels, terms like solar cell fingers and solar busbar are also important for the functioning of solar-powered systems. In this blog, let’s unravel what are solar busbar, what are solar cell fingers, what is the purpose of busbars in solar cells, etc.
What are Solar Busbar? What is the Purpose of Busbars in Solar Cells?
A solar busbar is a thin strip of aluminum or copper found between cells in a solar panel. Its job is to separate solar cells and conduct the direct current the solar cells collect from solar photons to the solar inverter. The solar inverter then converts the direct current into a feasible alternating current.
The size of a busbar ascertains the maximum amount of current that can be safely carried. Typically, in solar panels, the busbars are typically flat. This flat surface provides them with a high surface area to cross-sectional area ratio and thus they are able to dissipate heat more efficiently. Insulation may completely surround busbars or insulators can support busbars.
In the solar industry, busbars are linked to the solar panels by welded connections. Typically, they are contained inside busways, panelboards, or switchgear. On the other hand, in solar panels, the solar busbars are usually contained in busways, with long busbars accommodated in protective coverings. This type of arrangement permits the new circuits to branch off anywhere along the route of the busways. This further creates multiple points of transmission along the solar array. With this, you are now aware of what are solar busbar and what is the purpose of busbars in solar cells.
What are Solar Cell Fingers?
After learning what are solar busbar and what is the purpose of busbars in solar cells, let’s also explore what are solar cell fingers. Silicon solar cells are metalized with thin strips printed on their rear and front ends. These contact strips are called solar busbars. In solar cells, when photons hit the cells, the busbars have the purpose to conduct the electric DC power generated by the cell. Solar cell fingers are super-thin metallic grid fingers placed perpendicular to busbars. The cell fingers are responsible for collecting the generated DC current and delivering it to the busbars.
What is Multi Busbar Technology? What is Multi Busbar Solar Module?
In the solar industry, there is an immense demand for high-performance solar panels, and that too at a reasonable cost. This increased demand is making solar experiments with the structure of solar cells and modules. One of the major modifications or innovations done to solar panels is incorporating multiple busbars on a panel.
Generally, the solar bus bars are made of copper plated with silver paste to enhance. The current conductivity in the front side. This also minimizes oxidation at the backside. Multiple busbars are also employed to wire solar cells together. This helps generate high-voltage electricity.
A panel embodied with multiple busbars makes sure that you have high cost-saving potential. This happens because the metallization process will need less amount of silver coating on the front side. In the fabrication of PV solar cells, the process of metallization plays a very important role. It is because the silver coating for the deposition of buses and fingers is one of the most expensive steps in cell fabrication. Multi-busbar assists in decreasing the total series resistance of the interconnected solar cells. With this, you should have understood what is multi busbar technology and what is multi busbar solar module. After this, let’s see what is 9 bus bar in solar panels.
What is 9 Bus Bar in Solar Panel?
9 busbars in solar panels mean that the module in the solar panels contains several cells with nine busbars. The more busbars the solar panels have, the more electricity they can conduct. Before this, there are also some other busbar-type solar panels in the market like 3BB, 4BB, and 5BB. A grid of busbars and fingers characterizes the surface of a standard solar cell. With this, you should have understood what is 9 bus bar in solar panels. Now, let’s also learn how do I choose a busbar size.
Also Read: What is a Busbar?
How Do I Choose a Busbar Size?
Busbar size calculation is a very important step to prevent any overheating in an electrical system. Most electrical engineers, consultants, and electricians use a common rule to choose a busbar size and this is called Thumb Rule Method. Earlier the calculation of busbar size was done manually and this is where the thumb rule helped them.
The Thumb Rule states the amount of current a 1 square mm (Sq.mm) busbar can withstand. Copper and aluminum are the two common materials used for producing busbars. Both of them have their own ability to withstand currents.
- A 1 Sq.mm of copper busbar can without about 1.2 Amperes.
- A 1 Sq.mm of aluminum busbar can withstand nearly 0.7 Amperes.
It’s obvious that these examples aren’t synonymous with international standards because you can’t find the tolerance values. Some people may use a copper busbar to deliver 1.5 Amps whereas others can use an aluminum busbar to deliver 1 Amp.
Over time, this primitive rule became unreliable for high currents in thousand amps. Now you need to do a proper calculation with a proper standard. With this, you should have understood how do I choose a busbar size.
What Factors to Consider While Calculating Electrical Busbar Size?
While analyzing and calculating electrical busbar size, these are some factors you should consider-
- Electrodynamic forces and mechanical resonances under normal as well as extreme (faulty) conditions.
- Minimum clearance for phase-to-ground and phase-to-phase.
- Selecting proper busbar insulator deadlock.
- Adequate and safe bolt installation for multiple busbar connections.
- Thermal effects produced by insulator and busbar for both normal as well as extreme (faulty) conditions.
Also See: 11 Major Factors Affecting Solar Panel Efficiency
How to Size Busbar?
Current isn’t the sole factor determining the size of the busbar. The temperature rise in the busbar needs to be in accordance with the specification of national or international standards. The standards are-
1. American Standard, ANSI C37.20
This standard states that the maximum temperature is about 65℃ higher than the ambient temperature in 24 hours. The ambient temperature is 40℃. Here silver-plated termination bolts are used. The allowable temperature rise is 30℃ if there is no bolt installed.
2. British Standard, BS 159
This standard states that the maximum temperature rise is about 50℃ higher than the ambient temperature in 24 hours. At its peak, the ambient temperature is 35℃ to 40℃.
The very basic idea on how to size a copper busbar is 1250 Amps/1 Sq.in (in2) or 2 Amps/1 Sq.mm (mm2). However, these can be different in some counties. This is just a first-aid decision and for the final decision you should count on more factors. Make sure you check the manufacturer’s catalog before making the final decision.
What Does Busbar Size Depends On?
Apart from the factors we learned about earlier, there are also some application areas that you should take into account while doing busbar calculation.
1. Main Switchboard: For each riser, there is only one output. This reduced the cost and size of the main panel.
2. Voltage Drop: In busbars, the voltage drop is lower than electrical wires. This is because the busbars have lower impedance.
3. Number of Circuits: For all the floors, only one circuit is needed.
4. Shaft Size: Usually, the size for a busbar with a 1600 A current rating is 185 x 180 mm. In comparison to electrical wires that carry the same amount of current, a busbar is significantly cheaper to build a riser shaft size.
5. Fire and Safety: The insulator materials that are used for busbars don’t produce corrosive effects and toxic gasses to cause a fire.
6. Installation Time: The installation time for the busbar is quite less.
7. Fault Withstand Level: Busbars have much higher maximum current ratings. Usually, a 1600 A riser can withstand about 60 – 70 kA.
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What are the Types of Bus Bar?
The busbars are available in various sizes. Their sizes are 100x10mm, 80x8mm, 50x6mm, 60x8mm, 40x5mm, and 40x4mm. Their use in the distribution of power depends on factors like flexibility, cost, reliability, etc. While selecting their arrangement, you must consider that the arrangement should be simple, easy, and cheap. Additionally, the maintenance process should not affect the process of distribution of power.
The different types of busbars are explained below-
1. Single Bus-Bar Arrangement
The single bus-bar arrangement is quite easy and simple. In this type of arrangement, there is a single bus with a switchboard. The transformers, generators, and feeders are linked to the bus bar.
The circuit breaker controls the generators, feeders, and transformer. During maintenance, the isolators are used to isolate the feeders, generators, and transformers from the bus bar.
Advantages of Single Bus Bar Arrangement
- Operation is easy and simple
- Less maintenance
- Lower cost
Disadvantages of Single Bus Bar Arrangement
- In case of any fault in this type of arrangement, the feeders will be disconnected and the whole distribution of power will be interrupted.
- It isn’t quite flexible and used in only switchboards, small substations, and small power stations where there is no need for a continuous distribution of power.
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2. Single Bus-Bar Arrangement with Bus Sectionalized
It is a type mostly used in large stations. In this arrangement, several units are installed using a bus sectionalized. Here, isolators and circuit breakers are used.
In the arrangement, the isolators are used to separate the faulty section to protect the system from the shutdown. Even when an additional circuit breaker is used, there is no increase in cost.
Advantages of Single Bus-Bar Arrangement with Bus Sectionalized
- It’s easy to remove the fault section and that too without any loss in the supply continuity.
- In such busbars, the individual sections on the bus can be repaired without disturbing the overall section on the bus bar.
- It has a current limiting reactor that helps reduce the faults in the sections of the bus bar.
Disadvantages of Single Bus-Bar Arrangement with Bus Sectionalized
- The use of additional circuit breakers and isolators in the system hikes the cost.
3. Main and Transfer Bus Arrangement
This type of bus bar is designed by combining the main bus bar and the auxiliary type. It is done so by using a bus coupler to connect the isolated switches and circuit breakers. In an overloading case, by using a bus coupler, the load is transferred from one busbar to another busbar. In this case, to transfer the load, the potentials of the two bus bars should be similar. Additionally, the main bar should be opened as well as kept closer to transfer the load.
Advantages of Main and Transfer Bus Arrangement
If any fault occurs, the primary advantage is shifting the load from one type to another type.
- The maintenance and repair cost is less.
- Using the bus potential, relays can be operated.
- It is quite easy to shift the load on any other bus.
Disadvantages of Main and Transfer Bus Arrangement
- As the whole system uses two busbars, the cost increases.
- If any fault occurs in any of the sections on the bus, the whole system may break down.
Also See: 5 Major Disadvantages of Hybrid Inverter
4. Double Bus Double Breaker Arrangement
In this type of arrangement, two bus bars with two circuit breakers are used. So, it doesn’t require any special types of equipment like a bus couple and switch.
Advantages of Double Bus Double Breaker Arrangement
- As there is no loss of continuity due to faults, it gives the highest reliability and flexibility.
- Although the load is transferred from one bus to another, there will be no change in the supply continuity of the system.
Disadvantages of Double Bus Double Breaker Arrangement
- Due to the two buses and additional circuit breakers, the cost of the system as well as its maintenance is much more. These types of busbars systems are used in substations.
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5. Sectionalized Double Bus Bar Arrangement
In this type of busbar arrangement, an auxiliary type is also used with the sectionalized main busbar system. For maintenance and repair, Any of the sections in the main type can be removed. These sections can further be connected to any of the auxiliary bus bars in the system. Because of its high cost, there is no need to sectionalize the auxiliary type.
6. One-and-a-Half Breaker Arrangement
In such a system arrangement, for 2 circuits 3 circuit breakers are used. Each circuit in this system will use half the circuit breaker. This arrangement is mainly used in large stations.
Advantages of One-and-a-Half Breaker Arrangement
- This type of system protects the system against the loss of power supply.
- It can be used to operate relays.
- In such an arrangement, it’s quite easy to add additional circuits to the system.
Disadvantages of One-and-a-Half Breaker Arrangement
- This type of system has a quite high maintenance cost.
- It has a complex circuit due to the relay system.
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7. Ring Main Arrangement
It is a type of system that is arranged in ring form. It is done by connecting the endpoint of the main bus bar in the system back with the starting point.
Advantages of Ring Main Arrangement
- Due to the ring arrangement, this type of busbar has two paths available for supply. So, the faults will not affect the working of the system.
- Without affecting the entire working of the system, the faults of a particular section in the whole system can be repaired.
- In such an arrangement, it’s easy to maintain the circuit breaker and that too without causing any interruption in the supply.
Disadvantages of Ring Main Arrangement
- If any of the circuit breakers are opened, the system would be overloaded.
- There are chances of complications while adding a new circuit.
Also Read: Why is My Ring Solar Panel Not Charging?
8. Mesh Arrangement
This is a kind of bus bar arrangement that is connected by 4 circuit breakers, which are installed in the mesh. The circuit is tapped in front of the node point. The occurrence of faults in any of the sections can open the mesh formed by the buses.
The mesh arrangement is used in substations where it requires a large number of circuits. It also provides security against faults. Additionally, there is a lack of facility for switching.
Busbars are increasingly becoming parts of solar panels, they are eminent for the functioning of solar systems, and thus learning about such elements is important. After going through this blog, you must have cleared all your questions related to solar busbars.
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