By Kennedy Maize
Roll over, Tom Edison; tell Nikola the news: DC current is cruisin’ down the wires. You lose.
Sometime this spring, the 339-mile, 400kV Champlain Hudson Power Express (HPE), a high voltage-direct current underground and underwater transmission line is set to begin delivering 1,250-MW of hydro and wind power from Quebec to New York City. Transmission Developers (TDI), a Blackstone Inc. com, says work was completed on the $6 billion project in January. Construction began in 2022.
TDI has another HV-DC project on the shelf, designed to move 1,000-MW of Canadian power 154 miles underground and under water, to Vermont, the New England Clean Power Link, a 2023 revival of a failed project dating back to 2014.
The CHPE project (colloquially referred to as “Chippy”) will deliver power to a facility in Queens, where it will be converted to the city’s alternating current distribution system.
AC power transmission and distribution has dominated the U.S. electric system since the end of the 19th Century, the result of a business war between two early industry titans, Thomas Edison and George Westinghouse. They were in a struggle to determine who would determine how the magic of electricity would be developed beyond the immediate neighborhoods where the generating plants were located.
High voltage arc lighting, developed in Britain in the early 1800s, using alternating current to light streets and large buildings, dominated electric illumination into the 1880s. Along came Edison, who demonstrated commercially viable low-voltage direct current incandescent electric lighting in 1882 at his Pearl Street Station in New York City’s financial district.
The business opportunity was enormous: how to supplant gas lighting for business and residential indoor lighting. The task was how best to move electric power many miles from the generator to the new markets.
Edison advocated direct current transmission to push power across long distances. Rival Westinghouse, a Pittsburgh-based entrepreneur and inventor who developed the compressed air technology for railroad engine brakes, was pushing alternating current. In 1886, he founded Westinghouse Electric Corp. to compete directly with Edison for the national market.
Edison had the early lead, but his DC power system had a major problem. It only worked at 110 volts, meaning it could only be delivered over short distances. Westinghouse smartly took advantage of this crucial DC problem, developing and licensing technology, including transformers that could step high voltage AC down to currents needed for indoor lighting. He was bolstered by former Edison employee Nikola Tesla, a prolific inventor and AC advocate, who developed induction motors that could use the stepped-down AC voltages.
By 1893, Westinghouse and alternating current had largely won the war. The company was selected to supply electrical power for the World’s Columbian Exposition that year and a major part of the contract to build the Niagara Falls hydroelectric project (splitting the contract with Edison’s General Electric).
The last DC power system in the U.S. died on Nov. 14, 2007. The New York Times reported, “Today, Con Edison will end 125 years of direct current electricity service that began when Thomas Edison opened his Pearl Street power station on Sept. 4, 1882. Con Ed will now only provide alternating current, in a final, vestigial triumph by Nikola Tesla and George Westinghouse, Mr. Edison’s rivals who were the main proponents of alternating current in the AC/DC debates of the turn of the 20th century.” Tesla
Now, driven by power technology largely developed in Sweden and Germany in the 1930s and widely used in Europe, and the seemingly inexorable growth of data center driven demand in the U.S. — requiring new transmission and transmission upgrades — DC transmission up to 800 kV is making a strong comeback.
Writing in Utility Dive recently, Shaun Walsh of Peak Nano, an Ohio advanced materials company, describes a “shift from alternating current (AC) to direct current (DC) in data centers and electrified transportation.” Walsh observes that in the 19th Century “War of the Currents,” AC won not because it was more efficient than DC, but because it was easier to change voltage for long‑distance transmission and a rapidly expanding grid. DC couldn’t deliver then, but today, DC–DC power converter technologies enable efficient, reliable DC voltage changes.”
Walsh notes that telecom systems “have run on DC for most of the last century to provide stable service. Data centers are now walking a similar path, with much larger loads and more concentrated power density. The same principles keeping phone networks reliable now apply to AI training clusters and cloud campuses: simplify conversions, tighten power quality, and design distribution around DC.”
HVDC developer TDI lauds some of the advantages of the technology: “Buried HVDC cables have been used worldwide for nearly 80 years. Some of the first commercial uses for HVDC lines date back to the early 1950s, and many are still in service today.
Among the benefits the company advances:
- Minimizing impacts on the environment including protecting scenic landscapes.
- Resilient technology that will not fail in the face of extreme weather events.
- Avoids visual impacts of overhead transmission projects with out of sight installation—either underwater or underground.
- Minimal electrical energy losses in comparison to traditional overhead HVAC transmission lines, making it well suited for a project covering this distance.
Also, HVDC transmission could fit well with modern renewable wind and solar generation and battery storage, avoiding the need for inverters to convert their DC output for transmission on the AC grid. In addition, data centers need DC power for their computers. The conversion from high voltage AC to low voltage DC produces a lot of heat in the computer-centric centers, complicating their design and operation.
