Have you ever seen energy storage suspended mid-air? Above Zhangjiakou's wind farms, rows of ‘gravity weights’ resemble giant dumbbells. When turbines generate excess power, motors hoist these weights to 120-metre heights; when electricity is needed, hooks release them to plummet down, driving generators for secondary power generation. The entire system responds in 0.1 seconds—faster than you could scan a QR code. Engineers quip: This turns wind into “muscle”—one lift of iron generates one kilowatt-hour."