Balance Of System

Balance of Systems (BoS)

A Grid Tied Solar Rooftop Photovoltaic (SPV) power plant consists of SPV array, Module Mounting Structure, Power Conditioning Unit (PCU) consisting of Maximum Power Point Tracker (MPPT), Inverter, and Controls & Protections, interconnect cables, Junction boxes, Distribution boxes and switches. PV Array is mounted on a suitable structure. Grid tied SPV system should be designed with necessary features to supplement the grid power during day time. Components and parts used in the SPV power plants including the PV modules, metallic structures, cables, junction box, switches, PCUs etc., should conform to the BIS or IEC or international specifications, wherever such specifications are available and applicable. Solar PV system shall consist of following equipments/components.

Solar PV modules consisting of required number of Crystalline PV cells. Grid interactive Power Conditioning Unit with Remote Monitoring System Mounting structures Junction Boxes. Earthing and lightening protections. IR/UV protected PVC Cables, pipes and accessories. All these accessories are also known as balance of system (BoS)

1. Solar PV Panel
2. Anti-theft Nut Bolt
3. Module mounting Structure 
4. Solar inverter 
5. Array junction Box (AJB) 
6. MC-4 Connectors 
7. Solar (PV) Cable
8. Lightning Arrester
9. Earthing Strip
10. AC & DCDB Box

Solar PV Module:

A PV module consists of many PV cells wired in parallel to increase current and in series to produce a higher voltage. 

The module is encapsulated with tempered glass (or some other transparent material) on the front surface, and with a protective and waterproof material on the back surface. The edges are sealed for weather proofing, and there is often an aluminium frame holding everything together in a mountable unit. In the back of the module, there is a junction box, or wire leads, providing electrical connections.

Anti theft nut bolt:

Anti theft nut bolt:Anti theft nut bolt is nothing but it is used in fixing of solar PV module in Solar PV power plant for prevention of thefting of solar PV module.

Module Mounting Structure:

Photovoltaic mounting systems (also called solar module racking) are used to fix solar panels on surfaces like roofs, building facades, or the ground. The mounting structures are used to support the solar PV modules. Since the solar PV modules are built to last for 25 years, it is very important to choose the solar PV module mounting structure as it has to support the solar PV module for 25 years.

Module mounting structures are made of three types of materials: -

1. Hot Dip Galvanized Iron
2. Aluminium & 
3. Mild Steel (MS). 

Solar PV Inverter:

Solar PV inverter is an electrical equipment which is convert Dc current in to AC current because our home appliances run on 230-240 V,50 Hz. AC current.

Solar Inverters are classified as below as per their application

⦿ Grid Connected Inverters

⦿ Stand Alone Inverters

⦿ Hybrid Inverters

⦿ Grid connected Solar Inverters are further classified as below as per their rated capacity

⦿ Central Inverters

⦿ String Inverters

Array Junction Box:

⦿ The junction box contains the electrical terminals of the PV module, which come from inside of the PV module.
⦿ The junction box also contains bypass diodes, which are connected in parallel to the series of cells inside the PV module.
⦿ These bypass diodes are used to divert current in case a series of cells are not able to conduct current due to any shading or damage.
⦿ The junction box is adhered to the back-side of the PV module, which should last throughout the life (25+ years) of the module.
⦿ The junction box is rated IP 65 or higher, so that there is no ingress of dust or moisture inside it.

MC-4 Connectors:

⦿ Connectors of a PV module are also known as ‘quick-connects’
⦿ PV connectors do not require tools to connect.
⦿ However, it is highly recommended to use a tool to disconnect such connectors to avoid any damage to them.
⦿ Connectors should be at least IP65 rated.
⦿ Typical Makes:
Multi-Contact (MC) 4,
Tyco,
Radox,
⦿ Amphenol, etc.
⦿ It is important to specify the type of connector to ensure its compatibility with other equipment of the PV system.
⦿ More information on electrical and other properties of connector

Solar (PV) Cable:

Solar Cable is the interconnection cable used in solar photovoltaic power generation. A solar cable interconnects solar panel and others electrical component in solar photovoltaic system.

Lightning Arrester:

About the lightning arrester we can understand following ways :ㅡ

⦿ It dose not absorb the lightning.
⦿ It dose not stop the lightning.
⦿ It dose divert the lightning to the ground.

⦿ It dose clamp (Limit) the voltage produced by lightning.

⦿  It only protects equipment electrically in parallel with it. 

Earthing Strip:

⦿ Earthing is an electrical connection between metallic parts, structures or electric circuit to the ground through buried conductor, GI,CI or copper.

⦿ Generally in any earth pit measure area taken to ensure the good connectivity with low resistance 

⦿ This earthing strip is made by a thin iron sheet and this earthing strip is also Hot Dip Galvanized Iron like solar PV structure.

DC & ACDB Box:

DC DISTRIBUTION BOARD :-

⦿  DC Distribution panel to receive the DC output from the array field.

⦿  DC DPBs shall have sheet from enclosure of dust & vermin proof conform to IP 65 protection. The bus bars are made of copper of desired size. Suitable capacity MCBs/MCCB shall be provided for controlling the DC power output to the PCU along with necessary surge arrestors.

AC DISTRIBUTION PANEL BOARD :-

⦿  AC Distribution Panel Board (DPB) shall control the AC power from PCU/ inverter, and should have necessary surge arrestors. Interconnection from ACDB to mains at LT Bus bar while in grid tied mode.

⦿  All the Panel‟s shall be metal clad, totally enclosed, rigid, floor mounted, air - insulated, cubical type suitable for operation on three phase / single phase, 415 or 230 volts, 50 Hz

⦿  The panels shall be designed for minimum expected ambient temperature of 45 degree Celsius, 80 percent humidity and dusty weather.

Conclusion:

In above all paragraph we are discussed various type equipment / accessories which are used in solar PV power plant for photovoltaic power generation. These all equipment / accessories are known as balance of system.

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