DC Power's Long Road Back: How Sweden Changed

Thomas Edison's first commercial power station on Pearl Street could only serve customers within half a mile. Half a mile. I ran a bookstore for 30 years, and I know exactly what that radius feels like—it's your regulars, your neighbors, the people who walk past your window every day. It's a real business, but it has a ceiling built right into its foundation. Edison could see the gas lighting industry across the street taking customers he wanted, and he couldn't reach past the next block to get them. Every decision he made—the underground wires, the expensive copper, the dense urban location—was a workaround for that ceiling, not a solution to it.

That's the origin story of the "War of Currents," and the Asianometry video Sweden Made DC Great Again tells it with considerably more patience and clarity than the mythology usually allows. The short version most people know: Edison backed DC, Westinghouse backed AC, AC won. The longer version is where it gets interesting.

The reason AC won wasn't that it was simply better. It was that AC had a specific superpower—the transformer. A Frenchman named Lucien Gaulard and his English partner John Dixon Gibbs demonstrated in 1884 that you could transmit AC electricity at high voltage over long distances, then step it back down at the other end for safe use. As the video explains, "people now can build a huge, more efficient power station outside a city and use AC to transmit it to the people." You didn't need Pearl Street anymore. You didn't need to build your store in the middle of the most expensive real estate in Manhattan just to reach enough customers. You could move the whole operation somewhere sensible.

By 1892, Edison General Electric had merged with the AC-centric Thomson-Houston Electric Company to form General Electric. The half-mile problem was solved. AC had won. Case closed.

Except it wasn't, and this is the part that a straightforward "AC beat DC" narrative quietly glosses over.

Winning a market competition and solving every customer problem are not the same thing. I watched a national chain move into my neighborhood and win—they had better margins, more inventory, lower prices. They also couldn't tell you anything about a book except its ISBN number. The market picked them for the things the market measures, and left some real needs unserved. AC won the transmission market for good reasons, but the victory came with fine print.

The fine print is physics, specifically something called capacitance. When you run AC power through an underground or submarine cable—not overhead wires, but buried cable—the cable itself starts behaving like a battery. The copper conductor inside is wrapped in insulation and then a metal sheath, and that sandwich is essentially a capacitor. AC current flips direction 50 or 60 times per second, which means it's constantly charging and emptying that accidental battery. Heat builds. Energy is wasted. By the time your cable reaches somewhere between 50 and 100 kilometers, most of what you sent is gone—spent on charging a capacitor that does nothing useful for anyone. The video is blunt about it: "most of your AC current is being used to charge a useless battery inside your cable."

Overhead lines sidestep this problem because they're spread out and less insulated. But you can't run overhead lines across the ocean, or under a city, or between two countries that want to keep their grids electrically separate. And that's a real problem, because the places where you want to move large amounts of electricity are often exactly the places where overhead lines don't work. AC won the war and then discovered it couldn't serve half its potential customers.

DC, which doesn't flip, charges the capacitor once and stops. It doesn't care about frequencies. It can connect two grids running at different cycles—Japan's eastern grid famously runs at 50 Hz and its western grid at 60 Hz, a situation whose full history is tangled enough that any single-sentence explanation probably oversimplifies it, but the basic point stands: DC can bridge that divide without destabilizing either side. The problem in the early 20th century was that nobody had a practical way to convert high-voltage AC into high-voltage DC and back again. That's where this story gets genuinely strange.

The device that eventually made high-voltage DC transmission work was called the mercury arc rectifier, and it looked, according to the video, "vaguely reminiscent of a Wobbuffet." Inside a glass tube, a pool of liquid mercury served as a cathode—it emitted electrons, which created an arc that carried current in one direction. The AC current's negative phase was blocked. One-way valve, basically. Peter Cooper Hewitt is often credited with the early invention around 1902, though the full development involved multiple contributors across several years. Engineers quickly realized that a high-voltage version of this device could convert grid-scale AC into DC for long-distance transmission.

The problem was something called an arcback. The one-way valve would occasionally fire backward. Mercury ions would bombard the anode, the anode would start emitting electrons when it wasn't supposed to, and suddenly current was flowing in both directions at once—short circuits, damaged seals, permanent equipment damage. For years, arcbacks kept mercury arc rectifiers limited to a few kilowatts, far too little for any serious transmission work.

Then, sometime around 1929—though some sources place his most significant contributions somewhat later, in the 1930s—a young Swedish engineer named Uno Lamm joined ASEA, one of Sweden's leading electrical companies, to work on exactly this problem. He would stay on it for the next 40 years.

I want to sit with that for a moment, because it's easy to read past it. Forty years on one problem. Not forty years building a career with this as one project among many. Forty years with his name attached to a valve that kept misfiring. Lamm never fully eliminated arcbacks. What he did was figure out that the mercury ion sheath forming near the anode was concentrating negative voltage and causing the bombardments—and then he inserted intermediate electrodes to pull those ions away. It worked well enough. ASEA patented the concept in the late 1930s.

That kind of work doesn't show up in anyone's highlight reel. There's no dramatic demonstration, no rivalry with a famous competitor, no funding round to announce. It's the work of someone who decided that a problem worth solving was worth solving completely, even if completely took longer than anyone wanted to admit.

In 1950, Sweden's state power board ordered an HVDC link to the island of Gotland in the Baltic Sea. The island's thermal plant was expensive to run; the board wanted to pipe in power from the mainland instead. Lamm led the project. The cable—roughly 98 km long, operating at around 100 kV and 20 MW, though specifications vary somewhat across sources—ran from a converter station on the mainland out to Gotland's main town of Visby. High-voltage mercury arc rectifiers converted AC to DC for the crossing; another station on the island converted it back for local distribution.

The Gotland link went live in 1954. It was the first commercial HVDC transmission system in the world, and it worked.

That moment was quiet in the way that most genuinely consequential things are quiet. There was no battle, no famous name attached to the victory, no press campaign. A cable went live under the Baltic Sea and electricity moved along it without the losses that would have destroyed an AC cable of the same length. Other countries noticed. Japan noticed. The United Kingdom commissioned ASEA to build the first cross-channel HVDC link, completed in 1961. Over the following 15 years, ASEA built 11 HVDC projects across the world.

Then came the thyristor—a solid-state semiconductor that did what the mercury arc valve did, minus the mercury, minus the glass, minus the arcbacks, minus the temperamental sensitivity to temperature and cleanliness. Thyristors entered the market in 1957 and eventually replaced mercury arc valves entirely. They in turn gave way to insulated gate bipolar transistors, or IGBTs, which now handle HVDC conversion at scales and efficiencies that would have seemed implausible in 1954.

The grid carrying renewable power from wind farms at sea to cities hundreds of miles away runs on HVDC technology. Every submarine cable connecting national grids, every long-distance link where overhead lines aren't practical—that infrastructure traces back to a Baltic island and a Swedish engineer who spent four decades trying to stop a valve from firing backward.

The market declared a winner in 1892. The actual problem took another 60 years to solve, and it was solved by someone you've probably never heard of, working on something most people couldn't explain, one electrode at a time.

Dorothy "Dot" Williams is Buzzrag's Small Business & Entrepreneurship Correspondent. She covered the Asianometry video "Sweden Made DC Great Again" (published June 2025).