Transmission and substation equipment manufacturing contributes substantial embodied carbon to power system expansion, yet utilities lack standardized frameworks to account for these emissions before construction begins. Researchers have now developed a comprehensive pre-construction carbon accounting methodology and tested it on a 220 kV transmission project in China, revealing where emissions concentrate and how to reduce them.
The study quantified carbon across raw material extraction and manufacturing for nine key equipment categories, totaling 23,154 metric tons of CO2 equivalent. Notably, compact substation equipment accounted for 35% of emissions despite representing only 30 km of a much longer transmission corridor—a finding that challenges assumptions about where embodied carbon concentrates in grid projects.
Aluminum and steel dominate the emission profile. Aluminum conductor steel-reinforced cables, gas-insulated switchgear, and steel transmission towers collectively represent nearly 90% of project emissions, with aluminum's high energy intensity (28.5 tCO2 per ton) driving much of the burden. The analysis identified these materials as critical leverage points for intervention.
Applying a low-carbon scenario—substituting hydropower-sourced aluminum, direct-reduced iron electric arc furnace steel, and more compact switchgear designs—reduced projected emissions by 8,024 metric tons, a 34.7% reduction. Sensitivity analyses confirmed that material-level decarbonization remains the most impactful strategy across varying assumptions.
The methodology's value lies in enabling utilities to identify high-impact reduction opportunities before procurement decisions lock in emissions for decades. As global grid expansion accelerates to integrate renewable generation and electrify transport and heating, pre-construction carbon accounting will become essential for utilities tracking scope 3 emissions and complying with climate commitments. The framework demonstrates that strategic material choices—shifting to low-carbon aluminum and steel suppliers, optimizing equipment design for compactness, and leveraging hydropower-based manufacturing—can materially reduce the carbon intensity of critical grid infrastructure without compromising performance or reliability.
