Redefine EV Charging with Micro Substations

On the northwestern edge of Lisbon, just off the A36 highway, a small gravel-covered site hums with electricity. To a passerby it looks unremarkable: a fenced yard, a few transformers, pylons overhead. Yet this modest installation, initially built for supervising infrastructure, could redefine how electric vehicles are charged—plugging them straight into the backbone of the grid.

At this pilot station, Tiago Santos Guimarães and Jorge Martins demonstrate the concept as an electric car charges: no distribution upgrades, no years of waiting for permits—just a steady flow of power. "With the micro substation," says Martins, REN’s Director of Asset Management, "we can step down very high voltage to low voltage, bringing energy to remote EV chargers, rural communities, or even construction sites."

For all its revolutionary promise, the act itself feels almost ordinary: "You select the type of plug you want, plug in the car, and press a button," says Santos Guimarães, Siemens Energy’s Micro Substation Solutions Manager. "There you have it: from a 220,000 volts grid to your car."

The idea was born in crisis. In 2017, Portugal suffered devastating wildfires that cut auxiliary power to remote substations by knocking out their supply from the distribution network. Whole areas were left without supervision, and engineers at REN, the national transmission system operator, began searching for a way to keep substations monitored even when the local grid failed.

The answer was an inconspicuous but revolutionary approach: Because high-voltage lines run far above the ground and the corridors beneath them are kept clear of vegetation, they were rarely affected by fire. So REN began installing power voltage transformers in switching stations, tapping the lines and converting power to low voltage to ensure continuous auxiliary power.

Not long after the wildfires, on his usual commute from Porto to Lisbon, Martins remembers looking up at the high-voltage lines that run parallel to the highway: "Could that also be an option for EV charging?" Within a year, REN built the first demonstration project to test the idea.

Across Europe, the EV boom has outpaced the rollout of charging stations. According to the T&E January 2020 "Recharge EU" report, the continent will need more than 2.5 million chargers—six times today’s number. Outside cities, distribution grids often lack the strength to host high-power stations without costly reinforcements. That gap fuels what consumers call "battery anxiety": the fear of not finding a charger in range, or of waiting hours to refill.

"There's no time to lose," says Martins. "EV sales are moving faster than the expansion of substations. Right now, EVs account for only 4 percent of Portugal’s vehicle fleet, but imagine in 2030 or 2040 if we have 30 or 40 percent—the current distribution grid can’t deliver this future demand. This is where our technology comes in. The transmission grid is there—powerful, reliable, and practically limitless."

Tiago Santos Guimarães (Siemens Energy) and Jorge Martins (REN)

Turning that potential into a practical solution required new engineering. Together with Siemens Energy, REN developed a modular micro substation that could convert transmission voltage directly to the level EV chargers need. To make the step down possible, the transformer at the heart of the micro substation uses two separate coils of wire: the primary winding receives the high voltage from the transmission line, and the secondary winding releases it at a much lower voltage.

"By using thousands of turns in the primary winding in proportion to the turns in the secondary winding," says Santos Guimarães, "we can directly convert high voltage of 220,000 volts into low voltage of 230 volts."

To make the solution sustainable, Siemens Energy also replaced sulfur hexafluoride (SF₆)—a potent greenhouse gas long used in grid equipment—with clean air insulation. "To make air as good an insulator as SF₆, we use purified air and remove all moisture," says Santos Guimarães. "Technically, it’s a hybrid of a voltage transformer and a power transformer."

A look at the remote EV charging station in Pontinha, Portugal

Jorge Martins and Tiago Santos Guimarães standing next to the EV charging station, in the process of putting the charger in their car

One of the biggest challenges was not technical but regulatory. The European Patent Office initially questioned whether using the transmission grid for EV charging was safe. Transmission operators feared disruptions. But the Lisbon pilot proved otherwise. "Even if we charge 80 cars or 25 trucks at the same time we just use 1 percent of the available power of the line," Martins explains.

REN and Siemens Energy established an International Licensing Agreement for the electric mobility grid connection solution. "In 2022, the pilot project received the "Good Practice of the Year" award for Technical Innovation and Systems Integration, presented at a European Commission event," Martins notes. Recognition, however, has not yet translated into regulation. E-mobility is still not considered part of the transmission grid, meaning operators must find investors willing to take the commercial risk. "We need the courage of the first operator—and political frameworks that encourage such investments. Then this idea could change all of Europe," says Martins.

The Lisbon pilot currently powers a single fast charger for demonstration, but the potential is far larger. Each module can support multiple high-power chargers, and additional modules can be added as demand grows, reducing investment risk. With the same connection, the number of modules can be increased to power up hundreds of cars at the same location.

That virtually unlimited power availability makes the concept ideal for rural highways, logistics hubs, or heavy-duty truck stops—places where demand can surge but distribution grids fall short. The pilot fits neatly into Portugal's own overall energy transition: with 70 percent of power already renewable, every kilometer driven electrically reduces emissions.

Interest is coming from all over the world. Spain and the Netherlands are discussing concrete projects. In Brazil, communities in the Amazon see the potential to electrify remote villages. And in Europe, ports, forestry operations, and logistics hubs are being discussed as applications.

Next year, trials will already begin in forest regions, where 65 percent of overhead power lines run. Together with Siemens Energy, a compact solution is being tested to charge forestry machines during logging. Electric trucks would then transport the timber to factories, charging again during unloading, thus creating a circular system that could decarbonize the forestry industry.

The micro substation on the northwestern outskirts of Lisbon next to the A36 highway shows how crises can spark ideas that change the world. What began as an emergency solution during a natural disaster could become a global blueprint for the transport energy transition. "The system is definitely a gamechanger," says Santos Guimarães.