Aluminium-calcium composite used for transmission conductor prototype

Ames National Laboratory, a US DoE Office of Science national laboratory operated by Iowa State University, has developed a new type of high voltage overhead power conductor made of an aluminium-calcium composite for increased efficiency.

Material scientists from the laboratory are moving into the field-testing stage of the new type of cable, which is similar to today’s long distance power transmission lines, but with the composite is lighter and stronger than those currently in use.

The composite, which was previously developed and patented by Ames Lab, has at least 10% lower line losses than existing materials and is hoped to improve the nation’s grid reliability and performance.

According to the lab in a release, the high voltage overhead conductors used today have been the industry standard for more than half a century.

The most common type is made of aluminium with a steel core. Using these two dissimilar metals poses a variety of challenges, including how they respond to weather events such as ice, wind and storms.

Many of these challenges can be eliminated by using a conductor made from a uniform material, such as one made from strands of the aluminium-calcium composite.

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An aluminium-calcium composite

According to Iver Anderson, lead researcher for the project, the composite is made of microscopic calcium filaments that act as a lightweight reinforcement for the aluminium. Aluminium is an excellent conductor, but it is too weak to use alone in a conductor strung between power poles. The calcium in this new composite eliminates the need for a heavy steel core.

Said Anderson in a release:

“While most metal composite experts would not think of using another weak metal to add strength to aluminium…when calcium is co-deformed with aluminium (like striped toothpaste) they form very thin, long threads of calcium metal that make the aluminium stronger without making it more brittle.”

The composite is made from fine aluminium powder blended with a small amount of calcium powder (less than 10% total).

Anderson’s team used their expertise in powder processing to overcome the manufacturing challenges associated with converting highly reactive calcium into the fine powder needed for the composite.

Ames Lab partnered with a complete supply chain of seven US companies to manufacture the first prototype sample conductor.

After co-deforming the compacted powders into a bar, the conductor can be processed with the same manufacturing steps that are typically used for conventional overhead transmission conductors.

Recently, Ames Lab joined in a partnership with Mid-American Energy, a regional power company based in Des Moines, Iowa, which will field test conductor.

They will string the conductor between existing transmission towers to determine how well it performs in the real world. They will also test variable electrical loads and all the heat, cold, wind and severe weather that the plains of Iowa can dish out.

“Although the strength, conductivity and other properties of individual strands of the new composite conductor have been measured in the lab, measurements on the full conductor form in the natural environment are critical to industry acceptance of this new conductor choice,” said Anderson.

This research is supported by the Advanced Materials and Manufacturing Technologies Office (AMMTO), part of the Energy Efficiency and Renewable Energy Office, US Department of Energy.

The AMMTO supports a globally competitive US manufacturing sector that accelerates the adoption of innovative materials and manufacturing technologies in support of a clean, decarbonised economy.