Sitting in the shadow of a 10th-century Saxon castle and surrounded by emerald fields flecked with herds of grazing sheep and cattle, the English Midlands town of Stafford feels far removed from the hustle and bustle of Manchester, a cradle of the Industrial Revolution just an hour to the north.
But first impressions can be deceptive. While Manchester has largely left its industrial past behind and morphed into a major sports, business, media, and culture hub, Stafford is quietly transforming into a key player in the new renewable energy revolution. Engineers from more than 40 countries are working here to slow down climate change and increase the share of energy from clean and plentiful sources, like the wind and sunlight, in our sockets.
But it’s not wind turbines or solar panels they’re making in Stafford. Instead it’s the other core components needed to keep renewables a growing part of the energy mix: equipment that transmits renewable energy to homes and businesses. “Today you often end up in a situation, like in the case of offshore wind farms, where the energy is generated far away from where the demand is,” says Thomas Bjork, Grid Systems Integration R&D leader for GE Renewable Energy’s Grid Solutions business. “The question is, how do you actually ship the energy? In a way, it’s analogous to using a train or a truck to ship fuel. You can picture the grid as an electricity highway. Our job is to find the most efficient way to get it to your town.”
That way often begins on a whiteboard in Stafford, where GE owns several factories and engineering facilities developing smart and sturdy technology for high-voltage direct current (HVDC) systems. This mode of transmission enables utilities to efficiently transfer huge amounts of electricity over long distances.
When grid operators send electricity from a power plant to a point in the network, they will lose some along the way, just like water leaks out of a firehose. But HVDC losses are smaller than losses taking place in systems using alternating current, a more traditional transmission mode. That’s in part because alternating current typically moves one-way along a wire in a sine wave, switching 120 times per second between plus and minus in the U.S. (100 times in Europe). Direct current is much simpler: It can flow in either direction and at a constant plus or minus voltage.
“With HVDC, you can send more power over the same transmission line corridor — as much as three times more, in fact,” says Neil Beardsmore, HVDC segment leader at GE Renewable Energy. “This is huge considering that the cable itself could represent up to 70% of the total cost of the project. Another big benefit is that you can run HVDC through underground and underwater cables. This is difficult with AC, for various technical reasons.”
To be sure, DC grids have been around since Thomas Edison built the first one in downtown Manhattan in 1882. In 1932, GE built the first experimental 23-mile HVDC line in the U.S., connecting Mechanicville and Schenectady in upstate New York. But just like telephone companies have moved from switchboard operators to 5G networks, a similar evolution has taken place in the power transmission business.
The first HVDC line in the U.S. used the grandmother of the modern valve — a device called a glass mercury arc tube — to chop up sinuous AC current and “rectify” it into DC. Just as TV set manufacturers replaced plump vacuum tubes with tiny transistors, HVDC engineers have progressed to building valves from much smaller power electronics — voltage-source converters (VSC) — that can be controlled by a computer and break down and assemble whatever type of electrical waveform grid operators need.
The VSC technology requires a smaller footprint, allowing GE to deploy it at the DolWin3 station in the North Sea, where it collects electricity from a 900-megawatt (MW) offshore wind farm. The valves feed direct current into an HVDC cable that starts inside a yellow 18,000-ton converter station standing in the gray, choppy water and runs for 80 kilometers underwater. Once it reaches the shore, it extends another 80 kilometers underground before terminating at a similar inland facility, converting it back to AC.
GE is also making gear based on earlier technology, called line-commutated converters (LCC), that still have many onshore applications — like when utilities need to move jumbo-size amounts of power across huge distances. The technology made possible the world’s longest transmission link, connecting a pair of hydropower plants in the Amazon basin to São Paulo, some 1,460 miles away. GE’s LCC converters also operate in India, powering an 850-mile, 3,000-MW HVDC link running north from the eastern state of Chhattisgarh. GE is currently completing an HVDC energy superhighway in Sweden, building a link to a massive solar farm in Japan, and developing several projects in Korea.
HVDC will not completely replace traditional AC transmission, but it is becoming the AC grid’s increasingly important partner. HVDC technology can link AC grids operating at different frequencies and allow them to watch each other’s back. For example, the AC grid in Saudi Arabia is running at a frequency of 60 hertz, just like in the U.S., but United Arab Emirates, Kuwait, and other countries next door operate their grids at 50 hertz, similar to Europe. As a result, when Dubai needs extra power, it cannot ask its big neighbor for help. But the latest HVDC systems made in Stafford can turn straight direct current into waves of various shapes and frequencies and allow different grids to link up.
HVDC can also help improve the quality of the power flowing over AC grids — as an example, when voltage strays too far from standard frequency, HVDC can provide a prescribed frequency and hence prevent power failures. It can also help protect AC transmission networks from swings in production that lead to a problem called low inertia. The grid receives electricity from generators that spin, just like the merry-go-round, and produce electricity at a constant frequency. But when a bunch of wind turbines suddenly disconnect from the grid because the wind stops blowing, just like kids suddenly jumping off to pursue some other activity, the operators have to act quickly to return the frequency to its normal level or risk trouble. HVDC can help here too.
The device that makes all of this possible is a piece of power electronics — no bigger than a box of chocolates — called the valve. Its basic function is to switch AC to DC and back, but life is never so simple. Large arrays of these valves must handle hundreds of thousands of volts, conduct huge electrical currents of thousands of amperes, and turn on and off in about one-millionth of a second. To make sure they can do it day in and day out for years and in the middle of the ocean, “we built a torture chamber for valves,” says John Vodden, lead engineer at GE’s Grid Solutions business. “It’s all set up to re-create what life is really like and also to give that little valve a hard time.”
It takes about 10 minutes to walk from Stafford’s picturesque medieval center — it holds the largest timber-framed house in England — past a rugby field to Vodden’s torture chamber, officially called the Valve Test Facility. The test center, designed by Vodden, his colleague Jeremy Snazell, and their teams to validate technology for HVDC grids, opened earlier this year, and it has no peer in the world. For starters, it sits inside a giant Faraday cage the size of a cathedral that blocks electromagnetic waves and eliminates other disturbances inside the facility. The cage is just one of the many bespoke design features that allow GE engineers to stress-test the latest valve designs and specific configurations developed for customers and run them through extreme conditions they will likely never encounter in the field.
At the heart of the test center are custom-made arrays of valves assembled into special modules that can create any grid condition and disturbance on demand. The modules are bedecked with a myriad of voltage, current, and other sensors and connected by slim fiber-optic cables to the center’s brain. The brain, which is located in a dedicated area resembling a mashup of a gym changing room and a data center, consists of stacks of circuit boards stored away in a row of gray storage lockers; its job is to run software designed by Snazell and his colleagues. The whole setup enables the team to generate any waveform they want. “This is the world’s first system like that,” says Kevin Dyke, HVDC project manager for GE Renewable Energy’s Grid Solutions business. “It’s effectively programmable power supply.”
Programming electricity is a complex task, and GE employs in Stafford some 200 software engineers not only from the U.K. but also India, Korea, and China, who are specializing in writing code for HVDC. “The control system is the most important part, but I might be a little bit biased,” laughs Snazell, who got into coding by programming computer games when he was just 8 years old. “It’s what makes the system essentially intelligent. Because the power is so controllable, you can do things like support the AC grid. You can use it as a frequency control if your AC frequency is a bit lower or a bit higher.”
Snazell and his team started building their “arbitrary wave high-voltage and high-power generator” several years ago. “We realized early on that because this was so elusive, so very new, it was going to be very difficult,” he says. “But we wanted to get something down, something, anything, dirty, messy, an it-doesn’t-do-what-we-want-it-to-but-it-works solution. That was the start, and we just refined it, evolved it, and improved it.” Today, engineers at the test center can input the conditions they desire into their computers, and the brain inside the lockers will generate the wave they want. “It’s where the magic happens,” Snazell says. “The electronics decides how to achieve the voltage and tells the valve.”
The team controls the facility from a NASA-like command center with a bank of computer terminals and a wall of floor-to-ceiling windows overlooking the cavernous test chamber. The staff there can expose the valve arrays to as much as 90,000 volts and 6,000 amperes of current at the same time. Dyke says that in the past, companies would test their valves by exposing them to high voltage, then turn the voltage off and blast them with the current. “You then agree with the customers that you’ve kind of made it do what it’s supposed to do,” he says. “Our new system now gives you true representation [of the real world] by providing the current and the voltage at the same time. Nobody else can do this. This platform will likely change the industry for HVDC valve testing.”
But the test center is the last stop on a customer’s journey when they visit Stafford. They typically start inside a new GE facility across town, where multi-talented groups of hardware and software engineers and other staff design bespoke solutions for their projects, like expert tailors on London’s Savile Row. “We call them project pods,” says Bjork. “We locate the project leadership team, the key engineers, procurement, finance, quality — basically, all of the functions that contribute to delivery of that particular project are represented within the same area. Rather than being spread out in different parts of the building, anyone who’s concerned with a particular project is in the same area.”
Says Armstrong: “They all hear the same things. They all contribute to the same things. And that gives us a kind of sense of purpose of having everyone together.”