What do you see when you imagine a zero-carbon future? Electric buses zipping by? Rolling hills covered with solar panels? Offshore wind farms towering over the sea? If batteries are part of your vision, good thinking. But there's a promising, if whimsical, piece of the renewable energy puzzle that might be missing from your mental picture: the world of gravity energy storage.

The Chinese economy has suffered as a result of the pandemic, but one sector that's forging full-steam ahead is energy. Last week saw the opening of a massive new solar farm -the second-largest in the world-in the northwest province of Qinghai.