China's Shuangjiangkou dam, situated on the Dadu River in Sichuan province, has reached a major milestone with three of its four turbines now generating electricity, giving it an operational capacity of 1.5 gigawatts (GW). The dam is expected to reach a height of 315 meters upon completion, making it taller than the existing Jinping-I dam in China. The first 500 MW turbine was connected to the power grid on June 26, and the third turbine came online on August 31, supplying about 500 million kilowatt-hours (kWh) of electricity in just two months. The fourth and final 500 MW turbine is currently undergoing adjustment and testing, with its full commissioning expected by the end of 2026, at which point the dam will achieve its full capacity of 2 GW. Constructing such a massive structure in a high-altitude, cold environment required innovative engineering. Chinese engineers have used 27 large movable mirrors, each over 60 square meters, known as heliostats, to follow the sun's path. These mirrors concentrate sunlight to heat the dam's core, extending working hours by up to 3.5 hours and increasing the amount of material that can be placed and compacted. The system was first tested in the winter of 2021-2022, starting with 20 mirrors and later expanding to the full set of 27. The dam requires over 46 million cubic meters of materials, and its construction includes covered structures to protect materials from cold and rain, as well as automated machines that ensure the correct thickness and compaction of the materials. The structure must withstand the pressure of nearly 3 billion cubic meters of water, with the earth core built gradually, layer by layer, and continuously monitored for water content, thickness, and compaction. Once completed, Shuangjiangkou is expected to generate an average of about 7.7 billion kWh of electricity annually, slightly less than 2% of all electricity consumed in France in a year. Its reservoir, with a capacity of about 2.9 billion cubic meters, will play a vital role in regulating the upper reaches of the Dadu River, storing water during low demand and releasing it when needed. This makes the dam a key asset for managing frequency and consumption peaks in the Sichuan power grid. In addition to Shuangjiangkou, China is advancing an even larger hydroelectric project on the Yarlung Tsangpo River in Tibet, which will include five cascading power plants. This project is expected to produce about 300 billion kWh annually, nearly forty times the output of Shuangjiangkou, and will require an investment of about 1.2 trillion yuan (around 145 billion euros). However, such large-scale projects can have significant environmental and social impacts, including changes to river flows, water temperatures, sediment transport, and ecosystems, as well as potential displacement of local populations.