China produces more clean energy than any other country. Now it's rolling out an ultra-high-voltage grid to match – will its strategy of going big pay off?

In a sleepy village on the fringes of Shanghai, China's megacity of 25 million people, a hulking green building surrounded by a labyrinth of electric wires and poles stands in contrast with the landscape around it. Surrounding this beast, not far from the coastline of Hangzhou Bay, the vast funnel-shaped inlet of the East China Sea, are an array of vegetable plots, winding country paths and a tranquil canal.

This oddly out-of-place building is the Fengxian Converter Station, a hub for receiving electricity that has travelled some 1,900km (1,200 miles) before it is routed to power Shanghai's homes, offices and factories. At the other end of the transmission line lies the Xiangjiaba Hydropower Station in south-west China, which harnesses the energy of the mighty Jinsha River, the upper stretches of the Yangtze River.

The Xiangjiaba-Shanghai transmission link, which went into service in 2010, is one of China's first ultra-high-voltage (UHV) projects – a technology designed to deliver electricity over long distances. It spearheaded an era that would see the country build a vast network of UHV infrastructure, dubbed the "bullet trains for power", to send electricity generated from hydro and coal in remote regions to populous cities. 

China now considers these huge power cables key to its rapid buildout of wind and solar power bases, which are concentrated in several far-flung regions. Countries such as the UK, India and Brazil have adopted similar strategies.

Although using UHV isn't the only way to transmit renewable energy, its application in China – home to the world's largest national power system – can provide valuable lessons in a global quest for solutions to fast-track the energy transition.