The supporting river-crossing project for the Inner Mongolia Kubuqi Desert base-to-Shanghai power transmission line, known as the Inner Mongolia-to-Shanghai power link, has officially begun construction on July 30 in Shanghai's Chongming district. This nearly 1,800-kilometer-long "electricity artery," spanning six provinces, is expected to deliver up to 40 billion kilowatt-hours of electricity to Shanghai annually once fully operational, with over half being green energy. It will serve as a crucial pillar for Shanghai's medium- to long-term power supply security and green, low-carbon transition.

The project sets five global records. According to plans, clean electricity from wind and solar sources at the Inner Mongolia Kubuqi Desert base will be transmitted via a ±800 kV ultra-high voltage direct current line to Chongming Island in Shanghai. After conversion to 500 kV alternating current at a converter station, the power will cross the Yangtze River through a river-crossing project, landing on the Taicang side in Jiangsu Province before being integrated into Shanghai's main grid.

Why does the power, upon reaching Chongming, not go directly to downtown Shanghai but instead "detour" to Taicang? In fact, the entry point of the UHV DC line is set at the western end of Chongming Island, directly across from Jiangsu's Taicang. The river width at this point is much narrower than the distance from eastern Chongming to Pudong. Digging a tunnel toward Taicang, though crossing provincial borders, is the shortest route across the river. However, selecting this shortest route involved extensive debate. Sources from the East China branch of State Grid revealed that initial plans considered crossing the Yangtze River's "bell mouth" estuary directly from Chongming, but the river there is 19 kilometers wide, posing high technical risks for tunnel construction and requiring massive investment. Another idea involved a large-span crossing in Jiangsu, but it was limited by navigation and other constraints. After repeated comparisons, the final choice was to use a power corridor at Taicang's Qiyakou to cross the river.

Upon completion, the Inner Mongolia-to-Shanghai river-crossing project will set five global records simultaneously, according to Zhou Xiaosheng, director of the third management center at State Grid Shanghai Electric Power Engineering Construction Consulting Branch. These include the world's largest design transmission capacity, largest GIL installation scale, longest shield tunneling distance, largest tunnel diameter, and deepest buried power-specific tunnel. The shield tunnel diameter is 14.6 meters, equivalent to the width of a standard four-lane highway. The tunnel's deepest point is about 95 meters, comparable to a 32-story underground building, housing four 500 kV gas-insulated line corridors, double the scale of similar projects previously in the State Grid system.

The challenges extend beyond size and depth. The tunnel must pass beneath the Yangtze River's main navigation channel and a national germplasm resources protection zone, demanding extremely high construction precision and ecological protection standards. Fei Fei, deputy director of the UHV office at State Grid Shanghai Electric Power, noted that although the river-crossing tunnel is a supporting project, it is the controlling element of the entire Inner Mongolia-to-Shanghai power link. The tunnel's construction timeline is 2 to 3 years longer than the UHV DC main project, requiring it to start first. Shield tunneling is expected to begin in 2027, with tunnel completion by 2029, and full operation by the end of 2030.

Green energy becomes a global competitive edge. Shanghai's power grid is a typical receiving-end grid. From 2005 to 2024, Shanghai's electricity generation grew by about 51%, while electricity consumption surged by 115%, with local power supply growth far trailing demand. How can Shanghai meet its electricity balance? The answer is electricity from afar. In 2025, Shanghai's total electricity consumption reached 208.9 billion kWh, a year-on-year increase of 5.28%, with external power accounting for nearly half. Zhao Pandian, head of the construction management division at State Grid Shanghai Electric Power's UHV office, stated that with the rapid agglomeration of emerging industries like artificial intelligence and integrated circuits, Shanghai's electricity demand continues to rise sharply.

Changes in the electricity consumption structure further illustrate the trend. In 2025, electricity use in information transmission, software, and IT services grew by 19.2% year-on-year, while the manufacturing sectors for communication equipment, aerospace equipment, and photovoltaic equipment all saw growth rates exceeding 20%. The momentum intensified in 2026, with integrated circuit and computing power industry electricity consumption in the first half of the year rising by 20.1% and 23.2%, respectively, compared to the same period last year. Looking ahead to the "15th Five-Year Plan" period, Shanghai's three leading industries—integrated circuits, AI, and biomedicine—are set to reach trillion-yuan levels, with sustained industrial expansion driving continuous electricity demand. Without new cross-regional transmission channels, Shanghai's power supply security will face severe challenges given similarly tight electricity demand in neighboring provinces.

Once operational, the Inner Mongolia-to-Shanghai project will deliver about 40 billion kWh annually, equivalent to nearly 20% of Shanghai's total electricity consumption in 2025, significantly alleviating this pressure. Beyond ensuring power supply, the green electricity from the project is crucial. Over 50% of the delivered electricity will be green energy, replacing about 2.46 million tons of standard coal annually and reducing carbon dioxide emissions by over 970 million tons. For Shanghai, green electricity is not just a low-carbon development metric but also a competitive edge in global industries. As the "dual carbon" targets approach, more global supply chains are mandating green electricity usage, and many export-oriented manufacturers are purchasing green power to reduce product carbon footprints and enhance international competitiveness. However, constrained by local resource endowments, Shanghai's local green electricity supply is limited. While renewable energy consumption accounts for 31.3% of total electricity use, local new energy generation only makes up about 9.5%, making external clean electricity the primary source of green power. By 2030, Shanghai aims to reduce carbon emissions per unit of GDP by 70% from 2005 levels and increase the share of non-fossil energy consumption to 25%. Green electricity imports have become an inevitable choice for Shanghai's energy transition and industrial supply security.

Reserving more "arteries" for the future. Ultra-high voltage is the "main artery" of power transmission, typically referring to voltage levels of AC 1000 kV or DC ±800 kV and above. Shanghai already has three such arteries. In July 2010, the ±800 kV Xiangjiaba-Shanghai UHV DC demonstration project began operation, ushering Shanghai's grid into the UHV era. Two 1000 kV UHV AC projects were completed in 2013 and 2019, establishing a "two AC, one DC" UHV power supply pattern. The Inner Mongolia-to-Shanghai project is Shanghai's fourth power artery.

According to Shanghai's "15th Five-Year Plan," the city is deepening the construction of a new-type power system, aiming to build four 10-million-kilowatt-level green energy bases. These include promoting onshore and offshore solar photovoltaic development, targeting a total PV installed capacity exceeding 10 million kilowatts; advancing deep-sea offshore wind projects, aiming for total wind power capacity beyond 10 million kilowatts; actively seeking incremental hydropower resources to ensure total external hydropower supply capacity exceeds 10 million kilowatts; and accelerating the implementation of the Inner Mongolia-to-Shanghai project, establishing a new 10-million-kilowatt-level external wind and solar base. Thus, the Inner Mongolia-to-Shanghai project is not the end point. Power must come from afar and also from the sea.

Sources indicate that Shanghai is advancing the first batch of deep-sea offshore wind pilot projects. If completed and operational, these could provide tens of billions of kWh of green electricity annually to Shanghai, further solidifying its position as a technology source and industrial hub for offshore wind, driving upgrades across the entire supply chain from wind turbine equipment and submarine cable manufacturing to construction, installation, operation, and maintenance. Meanwhile, the East China Zhejiang UHV AC ring network is also accelerating. Though located within Zhejiang, this ring network will also handle the transmission of electricity from Anhui to the east and surplus power from Fujian to the north. Once completed, the ring network will ensure efficient delivery of clean energy from the southeast coast, creating conditions for Shanghai's power reception. "The river-crossing project has a current phase construction capacity of 8,000 megawatts, with a long-term design transmission capacity of 20,000 megawatts, reserving 12,000 megawatts of capacity for future green energy consumption and grid interconnection in the Yangtze River Delta region," Zhao Pandian stated. The coordinated efforts of the Inner Mongolia-to-Shanghai project and the new-type power system in the Yangtze River Delta will not only alleviate Shanghai's power supply-demand imbalance but also provide robust energy infrastructure support for the integrated development strategy of the Yangtze River Delta.