Life cycle assessment of submarine power cables for distribution of offshore wind power to land

To handle the rapid growth in renewable energy, it is expected that more than 80 million kilometres of power lines will need to be laid or replaced by 2040. Offshore wind power is increasingly important as a renewable energy source, requiring power cables with stringent requirements for both mechanical and electrical performance.

The analysis compares two types of three-phase high-voltage 245 kV cables with XLPE insulation. The main difference between the two cable types lies in the conductor material, where one uses an aluminium conductor and the other a copper conductor. The study uses a functional unit of 1 km of power cable and covers the life cycle phases raw material extraction production, transportation of materials to cable manufacturing site, cable manufacturing, distribution and installation. The evaluated 33.5 km route consists of 97.6% aluminium cable and 2.4% copper cable.

The results are presented at the endpoint level for the protection areas of human health, ecosystems, and natural resources, and at the midpoint level for climate impact. Material production followed by distribution and installation contributes most significantly to the total impact for the analysed protection areas and for climate change. The total climate change impact for the analysed cable length is estimated at approximately 27,500 tonnes of CO2-eq.

The cable consists of 97.6% aluminium cable and 2.4% copper cable, with climate impacts per km of cable estimated at 229 and 526 tonnes of CO2-eq. respectively, excluding distribution and installation and production of prototype and spare cables. Including these increases the climate impact to 386 and 1,107 tons of CO2-eq per km for the aluminium and copper cable respectively.

The study provides valuable insights into the environmental impacts of power cables. The installation of the cable stretch, including the distribution of cables from the manufacturing site to the installation site, represents a significant lifecycle phase for the total impact. It has, however, not been possible to differentiate between the contribution from the distribution and the installation phase itself. Therefore, future work should focus on separating the data for these two phases to understand how the distance between manufacturing and installation sites affects the results. Further research is also recommended on how the installed cable stretch will impact ecosystems on the seabed. This could provide valuable information for assessing whether cables should be reinstalled (removed) for material recycling at the end of their lifespan. Such knowledge will also be relevant for authorities in determining requirements for the installation and potential reinstallation of submarine cables in the future.