Aerial photo taken on May 13, 2019 shows workers inspecting a photovoltaic power plant built on barren mountains at Tumu Town of Huailai County in Zhangjiakou City, north China's Hebei Province. In recent years, Zhangjiakou city has vigorously developed and utilized new energy, with installed new-energy capacity surpassing 12 million kilowatts. (Xinhua/Yang Shiyao)