Copper has long been the metal of electricity generators and wiring. But presenter Justin Rowlatt asks whether new technologies herald the death of the old-fashioned electricity grid. Prof Andrea Sella of University College London explains the special properties of element 29 of the periodic table that mean that half of the world's mined copper is used to conduct electricity. Justin travels to the rapidly growing Indian city of Gurgaon to ask Jasmeet Khurana of solar consultancy Bridge to India what his government's plans to increase solar power a hundredfold mean for the best way to build the country's electricity grid. Electricity entrepreneur Simon Daniel of Moixa Technology argues that solar power and battery technology could transform the century-old debate between Tesla and Edison over AC vs DC power. And Zolaikha Strong of the Copper Development Association says the transition to renewable energy means the world will still need plenty more of the metal. (Photo: Copper cable, Credit: Yukosourov/Thinkstock)