High in the mountains of Sichuan, China is building a dam so tall that it could become the world's highest completed dam. But one of the most unusual tools being used to finish it is not a massive crane or a new type of concrete. It is sunlight.
Engineers working on the Shuangjiangkou Hydropower Station have installed 27 heliostats — large mirrors that track the sun and direct its rays toward the dam's construction area. The idea is surprisingly simple: use concentrated sunlight to keep part of the dam warm enough for construction to continue during the freezing winter months.
