The carbon payback for additional copper ‘invested’ into improving energy efficiency is earned back 20 to 300 times over the lifetime of an energy system says a new European report.
And for renewables, the carbon emissions for producing copper is earned back in a matter of 1 to 2 weeks.
Increasing the cross section of wires and cables, overhead railway lines and motor and transformer windings can significantly increase electrical energy efficiency. Incorporating one extra kilogram of copper contributes to saving between 100 and 3,750 kilograms of greenhouse gas emissions (CO2e).
At the same time, the energy savings achieved will, in a majority of cases, lead to lower life-cycle costs.
An important initial decision, in seeking to reduce these losses, is to use copper as the conductor. Differences in resistivity—part of the electrical energy dissipated as heat and lost as useful energy—mean that a copper conductor has only 60% of the losses of the same diameter in aluminium.
Once the decision for copper has been made, energy losses can be reduced further by increasing the diameter of the conductor. The following examples describe how increasing the copper conductor diameter can reduce carbon emissions:
15 kW induction motor
A 15 kW low voltage induction motor pumps water, drives an air compressor or operates a ventilation system. Upgrading the motor, from 89.4% to 91.8% efficiency, requires an increase in the copper conductor content from 8.3 to 10.3 kg, leading to a lifetime emission reduction of 7,500 kg of CO2e, using an average EU electricity mix.
1.6 MVA transformer
A 1.6 MVA oil-cooled transformer is used to connect industrial plants to the high or medium voltage public grid. Upgrading the transformer from an AA’ to a CC’ class, or to an amorphous iron core, results in increases in copper content of 220, and 720, kg respectively, leading to a lifetime emission reduction (at current EU electricity mix) of 500 kg CO2e/kg copper for the CC’ transformer and 280 kg of CO2e/kg copper for the amorphous core transformer.
Renewables
Moving to more complex systems such as renewables or electric vehicles, it is no longer possible to attribute greenhouse gas savings in these applications to copper. It remains however meaningful to compare the emissions of copper in production with the emission savings in use to identify the most suitable hotspots for improvement.
It takes much more than copper to construct a renewable energy plant. Copper however consumes only 1-2 weeks of a plant’s 1000-week lifetime, leaving plenty of carbon budget for other materials and still earning a net positive carbon return.
Electric vehicles
Electric vehicles emit about 3 times less greenhouse gasses compared to combustion vehicles, 45 g instead of 125 g/km. And electric vehicles use 2-3 times more copper, i.e. 62.5 – 75 kg of copper compared to 25-30 kg per vehicle.
Over a distance of 100,000 km, an electric vehicle will save 8 tonnes of emissions, for an additional copper use of 45 kg. To ‘earn’ back the additional copper use in the electric vehicle requires driving it for about 2,300 km.
Multi-fold environmental pay-back
As the above examples demonstrate, greenhouse emission savings are the highest for devices with a high utilisation rate and in countries with a high share of fossil fuels in the electricity generation mix. However, even in systems lower carbon emissions, savings remain substantial.
On the production side, approximately 4.1 kg of CO2e are emitted during the production of a kg of copper. This means the carbon emission savings of additional copper usage are to be divided by 4 to calculate a carbon payback factor.
