Environmental evaluation of power transmission in Norway

Electrical grid systems are required as a consequence of energy not being produced in the same place as it is consumed, and they are a key element of our energy systems. Transmission and distribution assets comprised of power lines, cables, transformers, substations and other electrical equipment generate a wide range of environmental impacts. Throughout the lifetime of the equipment, the impacts originate mainly from power losses during the use phase, but other life cycle stages such as installation, maintenance and dismantling also contribute significantly to some impact categories. In this paper, the environmental impacts of the Norwegian transmission grid are assessed. The methodology used here is Life Cycle Assessment (LCA) with ReCiPe as impact assessment method. In total, 11,097 km of lines and cables, 345 transformers and 121 substations were installed in the Norwegian transmission grid by the end of 2009; the network also included some hundreds of kilometers of sea cables between Norway and abroad. The results show that for each kW h of electricity transmitted in Norway, climate change impacts are of 1.3–1.5 g CO2 eq., assuming a Norwegian electricity mix. Half of these emissions are associated with power losses, and the other half with infrastructure processes such as materials production, installation, maintenance, and end-of-life. The results also show that after the losses, the infrastructure processes for overhead lines and transformers, and the emissions of SF6 from Gas Insulated equipment are the most relevant contributors for total climate impacts. A sensitivity analysis is done with respect to the electricity mix used to model power losses in the system. The results show that the contribution of power losses to the total climate change scores increases to 84% and 94%, by replacing the Norwegian mix by the Nordic mix and the European mix, respectively.