Electrical conductivity is defined as a material’s ability to allow the flow of electric charge. Aluminum is an excellent electrical conductor, which is why it is the second most commonly used conductive metal globally, surpassed only by copper. Aluminum’s high conductivity allows it to efficiently transmit power across vast distances and within electrical systems. Its widespread use is a testament to its performance and its place as a staple in modern electrical infrastructure.
How Aluminum Conducts Electricity
Aluminum’s ability to conduct electricity is rooted in its atomic structure and metallic bonding. Like all metals, aluminum atoms are held together by a unique chemical bond where valence electrons are not bound to a single atom. Each aluminum atom contributes its three outer-shell valence electrons to a shared space.
This arrangement creates a “sea of electrons” that moves freely throughout the metal’s crystalline lattice structure. The positive aluminum ions remain fixed, while the mobile electrons act as charge carriers. When a voltage is applied, these delocalized electrons are compelled to move in a directional flow, resulting in an electric current.
Comparing Aluminum and Copper Performance
The selection of aluminum over other conductors, particularly copper, involves a careful trade-off between several physical and economic factors. By volume, aluminum has approximately 61% of the electrical conductivity of copper, which is the standard benchmark for conductors. This difference means that an aluminum wire must have a larger cross-sectional area than a copper wire to carry the exact same amount of current with equal resistance.
Aluminum possesses a significant advantage in weight and density. It is roughly one-third the density of copper, making it lighter for a given volume of material. When comparing the ability to conduct electricity by weight, aluminum is the superior material, offering better conductivity per pound. This weight advantage is often a deciding factor in large-scale applications where structural support is a major concern.
Another primary consideration is the cost difference. Aluminum is far more abundant in the Earth’s crust than copper, resulting in aluminum being cheaper per unit of mass. This lower material cost makes aluminum an economical choice for large projects that require extensive amounts of conductor material. Therefore, the choice often balances copper’s superior volumetric conductivity against aluminum’s lower weight and reduced cost.
Primary Uses in Electrical Systems
Aluminum’s distinct advantages in cost and weight make it the preferred material for high-voltage transmission lines. The lighter weight of the aluminum conductor allows for longer spans between transmission towers. This ability to increase the distance between support structures significantly reduces the total number of towers and the associated construction costs for long-distance power grids.
Aluminum is also widely used in large feeder cables and bus bars within industrial and commercial power distribution systems. In these applications, the large cross-section necessary to compensate for aluminum’s lower volumetric conductivity is acceptable. Using aluminum in these massive conductors provides a cost saving over copper, and the increased surface area of the larger conductors aids in heat dissipation.
Aluminum oxide rapidly forms on its surface when exposed to air. This oxide layer is non-conductive and can increase resistance at connection points, which can lead to overheating and connection failure. Specialized connectors and anti-oxidant compounds are required to break through this layer and maintain a low-resistance electrical pathway.