Mission: Reduce CO₂ Emissions to Fight Global Warming

Since the Industrial Revolution, people have been fostering economic growth by burning oil, coal and other fossil fuels. As a consequence, the concentration of atmospheric carbon dioxide (CO₂) has increased by about 40% or more since the Industrial Revolution. The increase of CO₂ and other greenhouse gases has brought about a serious environmental issue, namely global warming. The impact of global warming has already been embodied in various aspects: unusual weather events, sea level rise, disruption of ecosystem processes and decrease in food resources caused by adverse effects on agriculture and fishery. It is not a stretch to say that global warming is an issue of prime importance for human beings to address.

To deal with these situations, countries around the world have taken action: the conclusion of the Kyoto Protocol, an international treaty adopted in 1997 at the Third Session of the Conference of the Parties to the United Nations Framework Convention on Climate Change (COP3), comprising legally binding commitments to reduce the emissions of greenhouse gases by developed countries to fight global warming. This international agreement has forced various industries to make significant changes. In particular, for automobile and parts manufacturers associated with vehicles that use fossil fuels as their power source, the reduction in CO₂ emissions has become an urgent matter.

What the auto industry has pursued to reduce CO₂ emissions is improvement in energy efficiency to cut back on energy consumption. To achieve this objective, it has become a common consensus in the auto industry that vehicle weight reduction is indispensable, in addition to improvement in engine combustion efficiency. Under these circumstances, the Sumitomo Electric Group began to take on the challenge of converting conventional copper automotive wiring harnesses to those made of a lightweight material, or aluminum. This effort to reduce vehicle weight is also a challenge for the reduction in CO₂ emissions, which is considered a social and global issue, and by extension, for the prevention of global warming.

A wiring harness is an organized set of wires used to transmit electric power and information. Many wiring harnesses are installed in vehicles, relaying electric power and information by connecting various components, including the spark plug for engine activation and gasoline combustion, heater, air-conditioner, power windows, interior lights, audio system and navigation system. Automotive wiring harness can be compared to the nerves and blood vessels of the human body. The Sumitomo Electric Group launched the development and production of wiring harnesses shortly after World War II. During the 1960s, riding the wave of high economic growth and resultant motorization, the Group rapidly increased the production of wiring harnesses.

Meanwhile, the major challenge to be tackled by automobile manufacturers was improvement in fuel efficiency. To achieve this objective, vehicle weight reduction was essential. Thus, the use of aluminum for automotive components had already been under study. Aluminum is very light, having a specific gravity of one-third of that of iron or copper. In addition, with a higher strength per unit weight than iron and excellent workability, aluminum has been considered one of the most favorable materials to reduce the weight of transportation equipment. In fact, aluminum has been gradually applied to heat-exchange equipment, including radiators and air-conditioners, and the doors and bodies of some prestige cars. As the next candidate for aluminum application, automobile manufacturers focused their attention on electrical components. Along with engines and alternators, wiring harnesses, clusters of copper wires, were one of the major factors in increasing vehicle weight. Therefore, the realization of aluminum wires was expected to make a significant contribution to vehicle weight reduction and improvement of fuel efficiency. However, the conversion to aluminum wires was not an easy project.

The realization of aluminum wiring harnesses, which had been at an impasse, was pushed significantly forward by the conclusion of the Kyoto Protocol. In line with the treaty, European countries began taking measures to reduce CO₂ emissions in unison, and the EU established controls over CO₂ emissions. For the United States, although the country did not sign the Kyoto Protocol, efforts to reduce CO₂ emissions began to be made in California and other states. Under these circumstances, the auto industry expedited the study for the realization of aluminum wiring harnesses.

Meanwhile, a steep rise in copper prices was a noteworthy change in the market environment. The rapid increase in demand for copper in China resulted in soaring copper prices. For automobile manufactures, therefore, the realization of aluminum wiring harnesses became an inevitable mission. In this way, the realization of aluminum wiring harnesses with a view to a reduction in vehicle weight and production cost came under the responsibility of the Sumitomo Electric Group and other wiring harness manufacturers. In fact, aluminum wires were already used for aerial transmission lines and automotive battery cables. These wires, however, are for high current, having a large conductor cross-sectional area. On the other hand, standard aluminum wires used for wiring harnesses are for low voltage, having a small conductor cross-sectional area. As other companies had gained a head start in terms of development, auto manufacturers claimed that the Sumitomo Electric Group had fallen behind in the race. “The Sumitomo Electric Group could not lose in the field of wire production—this pride of ours ignited our motivation” (Nagano). All the employees joined together to act as one.

To respond to requests from car manufacturers, the Group launched the development of aluminum wiring harnesses in autumn 2006, and the project took off in earnest at the beginning of 2007. From the outset of the development process, the Group made a concerted effort as “all Sumitomo Electric Group,” namely Sumitomo Electric, Sumitomo Wiring Systems and AutoNetworks Technologies. The challenge for the realization of aluminum wiring harnesses was clear: ensuring reliability equivalent to that of copper wiring harnesses. More specifically, it was necessary to meet the following requirements: the high strength (tensile strength) of aluminum wires; high conductivity (conductivity is an index of the ease of electric flow); reliable electrical connection between the wires and the terminals; and the prevention of long-discussed galvanic corrosion.

For the development of aluminum wires, Sumitomo Electric Toyama, one of the Sumitomo Electric Group members, made a significant contribution. Serving as a center of the production of various types of aluminum wires, the company possesses a wide range of aluminum-specific expertise. The person in charge, who conjointly developed aluminum wires with Sumitomo Electric Toyama, was Yasuyuki Otsuka, an employee of AutoNetworks Technologies. “I started the development of aluminum wires with clear development targets. The most important task was to achieve compatibility between strength and conductivity. The two features trade off against each other. I was required to develop a new aluminum alloy with both high strength and good conductivity.”