How much energy & greenhouse gas emissions are saved when upsizing a cable?

Every conductor in an electrical system has a built-in resistivity. This means that part of the electrical energy that it carries is dissipated as heat and is lost as useful energy. Although the electricity system is rapidly decarbonizing, generating this wasted electrical energy still produces carbon emissions and consequently contributes to global warming.

The answer to the question depends on many factors: the baseline cable to compare to, the high-efficiency solution choosen, the load profile and lifetime, and the greenhouse gas intensity of the electricity mix.

Therefore an example: we compare a 70 mm2 base case with an economically sized cable of 150 mm2:

Emissions for the production of the additional copper

• 150 mm2 – 70 mm2 = 80 mm2 = 0.00008 m3/m difference in cable section
• Additional copper material: 0.00008 m3/m X 8890 kg/m3 = 0.71 kg/m
• Emissions to produce 1 kg of copper: 4.10 kgCO2eq/kgCu
• Emissions for producing additional conductor material in the cable:
• 0.71 kg x 4.10 kgCO2eq/kgCu = 2.9 kg CO2eq/m

Emission savings through energy savings

• Reduced power losses: (1.7241/ 10e8) Ω*m x (200 A)^2 / (80 m2/10e6) = 8.62 W/m
• Reduced energy losses: 8.62 W/m x 3700 hrs/y x 0.65 loading = 20.7 kWh/y*m
• Average carbon intensity EU power generation (2017): 0.230 kg CO2eq/kWh [1]
• 20.7 kWh/y*m x 0.230 kg CO2eq/kWh = 4.8 kg CO2eq
• 4.8 kg CO2eq saved per year per meter of cable

Environmental payback time

2.9 kg CO2eq / 4.8 kg CO2eq = 0.6 y or 7 months

Producing new copper by investing in copper:

• Copper invested: 0.71 kg / m
• Energy saved: 20.7 kWh/m per year
• Over 20 years cable lifetime: 20.7 kWh/m x 20 = 414 kWh/m saved

Energy required to produce 1 kg of Cu: 47 MJ or 13 kWh [2]

-> With the energy saved by investing in 0.71 kg Cu per meter of cable, 31.85 kg of new Cu can be produced (or 45 kg new Cu for 1 kg of Cu)

Moreover, copper cable scrap, which uses copper in its unalloyed form, can be easily recycled into new applications. When used as cooling scrap in a primary smelter, it can be refined using just 0.4 kWh of electricity and 0.1 kg of CO2e emissions per kg of copper.

References

[1] European Environmental Agency, Greenhouse gas emission intensity of electricity generation in Europe, https://www.eea.europa.eu/ims/greenhouse-gas-emission-intensity-of-1, accessed April 6, 2022

[2] International Copper Association, Copper Environmental Profile, March 2018, available from https://copperalliance.org/wp-content/uploads/2021/07/ICA-EnvironmentalProfileHESD-201803-FINAL-LOWRES-1.pdf (accessed April 6, 2022)

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Last update: May 3, 2022