World largest impulse turbine with 500 MW Capacity
The largest impulse turbine in the world, with a capacity of 500 MW, was recently developed by Harbin Electric Machinary Company for the Datang Zala Hydropower station in China. This turbine, which has a runner diameter of 20 feet 5 inches (6.23 meters) and weighs 80 tons, is a significant advancement in High head hydropower technology. The turbine is designed to operate at a high head (328 feet or 100 meters) and is expected to achieve a high efficiency of 92.6%.
Impulse turbines (in Datang Zala's case, it's a Pelton wheel impulse design) are a type of turbine where high-pressure water jets are aimed at the turbine's buckets to turn it. The turbine itself operates in the air, rather than being submerged in water. Impulse turbines work best with high heads. Given the sheer force the turbines have to endure 24/7, martensitic steel was chosen as it's generally stronger and more corrosion-resistant compared to other types of steel.
The most common turbine, however, is the reaction turbine – like the Francis turbine (which is what you'll find in the Three Gorges Dam). Those are fully submerged and generate torque from both pressure and moving water.
Technical Specifications of the 500 MW Impulse Runner
Rated Output - 500 Mw
Turbine Type - Impulse turbine
Design Head - 671 meters
Runner Diameter - 6.23 meters
Runner Height -1.34 meters
Total Weight - 80 tons
Buckets - 21 stainless steel buckets
Hub Material - Forged martensitic stainless steel
Manufacturing and Testing
Fabrication involved advanced computer-aided design, multi-axis CNC machining, TIG/MAG welding, and high-fidelity flow diagnostics. The hub forging is the largest of its kind glob-ally, ensuring both structural integrity and pressure resistance under extreme conditions. The entire assembly was tested over a period of 107 days, with 1,700+ welding hours
Shipment and Logistics
The runner has departed Harbin Electric's facility and is now en route to Zhala hy-dropower station, crossing rugged terrain and high altitude regions via custom-engineered transport systems (Figure 2-Figure 3). Given the runner's dimensions and weight, the logistical operation represents one of the most complex hydro-component deliveries in China's infrastructure history.
Significance and Outlook
As a pinnacle of global hydropower technology, the development of this turbine run-ner stands as a model of system engineering innovation. Harbin Electric approachedthe design from the perspectives of unit safety and performance, conducting a compre-hensive analysis that considered the precise alignment
Currently, China leads the globe in new hydropower construction with 14.4 gigawatts of the 24.6 GW that came online in 2024, according to SCMP. Over half of that was from pumped storage hydropower, where reservoirs can be filled and then released into turbines on demand. China has just under 436 GW of installed capacity of hydropower. By contrast, the United States had a 103.1-GW capacity at the end of 2024.
Each year, the Datang Zala Hydropower plant is expected to slosh out almost 4 billion kWh of energy. That's the equivalent of burning 1.3 million tons of coal, except with 3.4 million tons less CO2 in the air. The hydropower station will have a total installed capacity of 1,000 MW. China's goal is to be carbon neutral by 2060.
The project is being built by China Datang Corporation, and construction of the main section began in 2023. The Datang Corp expects it to go online by 2028. The record-breaking turbines themselves were built over four years by Harbin Electric using in-house technology.