Discover why they are essential in photovoltaic systems
An electrical cable’s conductor can be made of copper or aluminium. Copper has 60% more electrical conductivity than aluminium, which is essential to consider when choosing a solar cable. The tinned copper coating allows compliance with European standards for solar installation. In general terms, the type of photovoltaic installation and the certification standards required by the project will determine the suitability of one conductor or another.
WHAT IS TINNED COPPER WIRE?
One of the main threats to copper sheathing in a cable is corrosion. This causes a decrease in the wire’s efficiency in humid or rainy climates, very hot environments, and certain land surfaces. Solar cables must withstand these conditions, so additional protection allows for better preservation and more efficient cable performance. The tin layer that coats the copper protects it from external factors affecting its performance. In addition, tinned copper wire is easier to solder.
SOLAR STANDARD EN 50618 REQUIRES TINNED COPPER CONDUCTORS
Standard EN 50618 specifies that in the design of a solar photovoltaic installation, the conductor must be made of flexible copper (class 5) tinned coated by EN 60228 Standard.
Therefore, for the solar installation to comply with EN 50618, the use of a cable with a flexible aluminium conductor for connecting solar panels is ruled out.
This material preference is based on the ease of installation offered by copper.
WHY IS THE TINNED COPPER CONDUCTOR INDISPENSABLE IN A SOLAR INSTALLATION?
The main advantages of the tinned electrolytic copper conductor:
The copper conductor offers higher tensile strength and does not require large conduit systems.
Using a solar cable with a copper conductor ensures greater resistance to corrosion.
With a copper conductor we obtain a more robust installation. With an aluminium conductor, extra precautions have to be taken, such as sanding the ends of the conductors (to remove the oxide layer) with the risk of damage and wire breakage if the wires are thin.
TINNED COPPER AVOIDS GALVANIC COUPLE
Compared to aluminium, the flexible copper conductor has specific characteristics that make it a much more technically suitable material for electrical conductors of photovoltaic cables.
The main strengths of copper compared to aluminium are:
Higher conductivity. For the same current, copper conductors can have a smaller cross-section than aluminium conductors.
Greater ductility. Copper is more flexible, so wires will not break as easily due to fatigue when subjected to bending and other mechanical demands.
Reduced sensitivity to compression. After the conductor has been crimped and installed, the wire will not suffer any deformation. In the case of the aluminium conductor, being more malleable, it will continue to deform, potentially causing a weak connection and increasing the electrical resistance at the point of contact.
Higher thermal resistance. Compared to aluminium, the copper conductor is more resistant to temperature changes, an indispensable characteristic in outdoor installations such as photovoltaic installations.
Tinned copper wires avoid galvanic couples when connecting metals of different potentials. Galvanic couples can severely damage metals with more negative potential (anode), causing oxidation by giving up electrons to metals with less negative potential. No galvanic corrosion optimises the lifetime of the photovoltaic system.
