Transformers are a crucial but nearly invisible part of our grid. The devices help efficiently move power across long distances, but they’re complicated and in short supply. And given that their basic design hasn’t changed much for about a century, they could use an upgrade.
As the world races to meet rising electricity demand from EVs, data centers, and more, researchers and companies are looking to modernize transformers. New, solid-state versions could help relieve some of the supply concerns and make sure the grid can handle the growing pressure.
Conventional transformers generally rely on huge amounts of specialized steel alloys and miles of copper wire to do their work of transferring electricity between circuits. Solid-state models, in comparison, combine magnetic components with high-power semiconductors, making them more compact and allowing for more control over the flow of electricity.
These devices are still in development, and can’t replace all traditional transformers today, especially the largest ones that work at the high voltages necessary for long-distance transmission. But a new generation of transformer technology could be a crucial part of our future grid.
The grid’s backbone
Moving electricity through the grid isn’t perfectly efficient: As electricity flows through power lines, some gets lost as heat. How much varies—the higher the voltage, the lower the current, and the less electricity gets lost. So a key function for the grid is stepping voltage up and down.
Consider, for example, your local solar plant. For that electricity to efficiently travel to your home hundreds of miles away, it needs to reach a higher voltage than what’s generated by the solar plant. Enter transformers.
In its path from the power plant to your outlets, electricity might go through one transformer at the solar farm and another at a substation nearby, stepping up the voltage twice to reach a high enough level to travel on high-voltage transmission lines. Solar panels also produce direct current (DC) electricity, which needs to be converted to alternating current (AC) via an inverter before it flows into a transformer. Closer to its destination, the voltage will be stepped down again, probably at least twice: once at another substation and again at a smaller transformer in your neighborhood.
If you’re in the US, electricity from a solar plant might be converted to AC by an inverter at around 480 volts, get stepped up to 115,000 volts for the transmission lines, and finally get stepped back down to 120 volts and 240 volts for your home.
Conventional transformers do this work using what essentially amount to loops of wire. The core of a transformer is typically made of a special type of steel called grain-oriented electrical steel. Coils of copper wire sit on either end of that core.
The number of loops in each coil determines the voltage on either end of the transformer: If there are more loops on the secondary coil than the primary, the voltage steps up, and if there are fewer, it steps down. When incoming electricity passes through loops on the upstream end of the transformer, that forms a magnetic field in the core. That field induces a voltage in the loops on the other side of the device, which is what allows the energy to continue flowing at a new voltage. This process is called magnetic induction.
Transformers form the backbone of electricity transmission and distribution, says Srdjan Lukic, a professor of electrical and computer engineering at North Carolina State University. In addition to doing the job of stepping up and down voltage, transformers also often provide what’s called galvanic isolation, meaning there’s no direct electrical path flowing through them. That can help limit disturbances from moving through the grid, improving safety.
The problem is that today’s transformers are big and bulky, and they’re also difficult and expensive to replace, Lukic says.
A solid option
Solid-state transformers essentially add so-called power electronics—semiconductors that convert and control electricity to the typical blueprint of today’s transformers.
While a conventional transformer operates at the frequency of the part of the grid it’s connected to, a solid-state transformer actually controls the frequency of the current. Typically, a solid-state transformer first converts incoming AC power from the grid to DC power, and then to a higher-frequency AC power using switches made of a semiconductor like silicon carbide.
From there, a magnetic component changes the voltage. Because the advanced semiconductors allow transformers to exert so much control over the frequency and stability of the current, the magnetic core can be much smaller than in a conventional transformer. Some come in at roughly one-tenth the size but have the same capacity, Lukic says.
Finally, additional power electronics convert the electricity from high-frequency AC to its required form—generally back to DC power and finally to lower-frequency AC.
Today, stepping voltage up and down is many transformers’ only job. But solid-state transformers can do much more. They absorb the jobs of devices like rectifiers and inverters (which convert AC to DC power and vice versa), shrinking the total footprint of the electrical equipment and potentially cutting the amount of power lost in the system.
In August, the New York Power Authority and the Electric Power Research Institute (EPRI) tested a one-megawatt solid-state transformer under realistic utility conditions at EPRI’s test site. The device was built in Lukic’s lab, and it was the first such test for a transformer of that capacity, he says.
The prototype was roughly 98% efficient—meaning it lost only 2% of the energy fed in. An equivalent conventional transformer and rectifier, by comparison, would be about 96% efficient together, Lukic says. A difference of 2% might seem small, but it is significant, since it means the solid-state transformer could cut power losses from conventional equipment in half, Lukic says.
One major goal of the project was to help utilities gain more confidence in these new components, Lukic says. That’s crucial, since these devices could be used on the power grid in the future. In the near term, solid-state transformers could be used within data centers to provide electricity for server racks.
The prototype is still a relatively low-voltage system, operating at about 15,000 volts. Industrial facilities like larger data centers often require higher-voltage connections, and transmission lines typically operate at hundreds of thousands of volts. Adapting solid-state transformers to these higher voltages will require further engineering development. But the test was a successful demonstration that solid-state transformers can work under real conditions, Lukic says.
Companies developing solid-state transformers are largely focused on data centers right now, Lukic says. There’s an influx of money to support developing the new technology, and the voltage requirements aren’t as high as they will be for larger transformers that will be needed for long-distance transmission.
In February, Heron Power raised $140 million to commercialize its solid-state transformer, which the company calls the Heron Link. The technology could be used in data centers, solar power arrays, and grid batteries, says Drew Baglino, the founder and CEO. The company is starting to test its technology at larger scales now, Baglino says. Ten megawatt-hours’ worth of batteries at Heron’s headquarters in Scotts Valley, California, will soon undergo testing with Heron transformers. The company is also planning a pilot with a nearby solar farm, Baglino says.
One challenge for solid-state transformers is that their power electronics have more failure modes than conventional transformers. In a traditional device, a failure means that the entire device will typically be taken offline, resulting in power interruptions. But Heron designs with that in mind, Baglino says: The company uses a modular design, with many small devices that work together. If one fails, the rest of the system keeps working until the affected bit can be replaced, which doesn’t require shutting the whole thing down.
Heron Power is currently building a $100 million factory in California to make advanced transformers. The facility should begin production in 2027 and reach its full production rate of 40 gigawatts’ worth of transformers per year in 2029.
The future of the grid
In recent years, companies that make grid equipment have put $1.7 billion into the US supply chain for power transformers, which are used in high-voltage transmission, says Benjamin Boucher, a supply chain analyst at Wood Mackenzie. There’s been an additional $1.3 billion invested for distribution transformers, the smaller devices that help transform power for homes and businesses, he adds.
But even this investment isn’t keeping pace with the rapid growth of the grid. Wait times for large conventional transformers—the kind needed to connect new power plants, long-distance transmission, and high-demand sites like data centers—are stretching as long as five years.
“Transformers have become one of the biggest bottlenecks for utilities, generation developers, and even data centers,” Boucher says. The big challenge is that it’s difficult to get new transformer manufacturing up and running, because it’s a quite technical process that requires a lot of specialized labor. So even facilities announced years ago are still years from opening, Boucher says.
Solid-state transformers could help ease some of that pressure. But high-voltage devices needed for power plant connections and transmission lines are the holy grail for solid-state transformers, Lukic says. Existing solid-state technology can’t be used for those applications yet, so the industry will need to develop new materials and designs to support high voltages and handle electricity safely in a compact device.
“We’re facing a big risk related to grid infrastructure,” Boucher says. “Without the transformers, you don’t really have an electrical grid.”