It is the wire which joins all the components and transfers the output of one to the next in line, making the current reach to the electrical appliances. You cannot connect the components with any wire size. As under-sized wire may get heat up soon and will eventually burn out while an over-sized wire will cost you more, reducing the financial feasibility of the system. Therefore, the right sizing is very important for the system to work efficiently. In this post, we will learn to size the wire in accordance with the current provided by the panels.
The concept of resistance
Everything which has mass or exists in this universe, offers some kind of resistance.
Resistance is the measure of the opposition offered by the wire to the flow of the current and it is measured in ohms.
While experimenting, our engineers found that:
Finally, the engineers encapsulated their findings in the form of an equation which is shown below:
Where, "p" (rho) is the resistivity of the wire whose value depends on the type of material like whether it is silver wire, copper wire or any other wire.
The copper wires are used for making connections as they are cheap and offer less resistance than other materials. Resistivity is an important term used in sizing the wire. (*The process treating copper at right temperature to make it soft and flexible is called annealing) Resistivity is the resistance offered by the wire of 1 meter length
(*The process treating copper at right temperature to make it soft and flexible is called annealing)
Ohm's law: An important concept
It states that for certain materials at particular range of temperature, the voltage drop across the wire is proportional to the amount of current flowing in it.
We can substitute this value of resistance in the very first formula.
My final formula becomes:
Before moving forward, it is important to know the above terms more clearly.
Let me make you understand with the help of the following picture:
A basic roof-top solar power system is made of solar panels, inverter, solar charge controller, batteries and obviously wires.
I haven't shown charge controller and batteries in the picture as the things can be explained without them. You are going to mount the panels on the roof and keep the remaining components in your home. You will be needing wires to connect the panels to the inverter. The length of the wires is decided by the distance between the panels and the inverter.
Know your energy consumption
The wire sizing depends on your energy consumption. The more you consume, the thicker is the wire used to connect the components.
Let us understand all this with one simple example: The energy consumption table is shown below:
My solar feasibility spreadsheet recommends 400 watts of solar panels for fulfilling this energy demand.
Configuring the solar panels
Now, we have all the values to know the cross-section area of the wire.
Calculating the cross-section area of wire
Putting all the values in the formula:
Know the diameter of the wire
When you look the wire closely, you can that it is cylindrical in shape with both ends forming the circle.
Know the gauge of the wire
In the market the wires are differentiated by the gauge, therefore we have to find the relation between the wire diameter and the wire gauge.
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The nearest gauge comes out to be 13. Therefore, I need to purchase wire of gauge 13 to connect my components of the solar power system.
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1 Comment
Charu
16/9/2020 09:56:35 pm
Excellent explanation..
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