NREL: NREL Power Electronics Capabilities Primed for Innovation

Imagine a technology that can convert, amplify, limit, filter, control, and transform electricity in countless ways to supply power to the grid. These are power electronics, and the National Renewable Energy Laboratory (NREL) is helping bring in a wave of developments for the ubiquitous technology with a suite of expanded capabilities.

With the modern transition to renewable energy and electrified transportation, power electronics have the potential to enable seamless integration of renewable energy resources with the electric grid. And as further developments are made to power electronics, generally, they are expected to grow, both in number and in application.

Brian Johnson working on a digital controller
NREL is researching power electronics and control systems that enable seamless integration of renewable energy resources and microgrids with the grid while meeting stringent operational requirements. Dennis Schroeder, NREL
“In multiple ways, the fate of energy systems is linked with progress in power electronics,” said Sreekant Narumanchi, a senior researcher at NREL.

From atomic-scale analysis to grid integration, NREL has built out a pipeline of power electronics capabilities that can accelerate innovation for this critical renewable energy technology. These include state-of-the-art chambers to synthesize materials, ultraviolet lasers to etch into semiconductors, and ovens to simultaneously test and bake electronics until they break. Capabilities extend across several lab facilities that feature the latest instruments to help users build, characterize, and validate power electronic devices in every aspect.

Read on to learn about some of NREL’s latest efforts to introduce more versatile materials, higher-performance components, and new concepts and controls that could forever change how the grid operates.

Customized Semiconductors
Once made of airtight tubes with electricity visibly jumping between electrodes, power electronics are now manufactured with semiconductor materials—same principle, just millions of times smaller. Because of their more adaptable size, power electronics are now used in earbuds and airplanes, in lightbulbs and light-rail trains. NREL’s power electronics facilities include tools to customize semiconductors from the very start, check their performance, build devices, and iterate designs.

“Fundamentally, a power electronics device must use a material with a very strong chemical bond for durability—but not so strong that electrons can’t flow freely. We also need to be able to control how those electrons flow,” explained Brooks Tellekamp, a materials physics researcher at NREL. “Balancing these three factors can lead to difficult physics.”

Tellekamp is part of an NREL team with the scientific breadth and technical knowledge to take on the materials challenges of power electronics. Tellekamp works with semiconductor materials, which are so small that a slight atomic difference can result in distinctly better or worse performance. To study the materials at such detail, Tellekamp operates a suite of machines that evaporate metals and ceramics and crystalize them as semiconductors. These machines can also precisely alter semiconductors’ chemical compositions, shape, stacking, bandgap size, and other parameters.

A power electronic component
On a virtual 360-degree tour, you can visit NREL’s Lab 189 in Building 16 to get a glimpse of technologies like the latest Prius inverter, a power electronics component. Photo by Dennis Schroeder, NREL
“As a lab, we have taken a holistic approach to not just looking at the materials or the devices but also the systems of devices—and every step in between,” Tellekamp said. “We have equipment to test how electrons in materials respond to electric and magnetic fields. We can then stack and control these materials and wire them up into components to test their durability. We can also design those components into something useful, like an inverter, and research whether it can stand up to intense operating conditions.”

The stack of technologies involved in power electronics spans many scales and combines numerous components to result in a final product, like a laptop or electric vehicle (EV) battery. With so many details in the design, everything—especially hardware that supplies heavy-duty power—has to be tested to identify its limits when stressed.

Ruggedness and Reliability
Power electronics often serve high-current or high-voltage applications on the grid and are therefore engineered to withstand extreme power flow. To test the temperature limits of power electronics, NREL’s machines can bake, shake, abrase, age, and shock components, like those in industrial environments or EVs in ways they might experience during continuous use—or even in ways beyond what they might experience on this planet, as spacecrafts might. Several thermal testers allow NREL to run currents at thousands of amperes—or as electrically charged as a lightning bolt—and test multiple devices simultaneously. Special chambers test how devices stand up to weather, such as heat and humidity. By combining these physical tests with computational modeling, NREL researchers can predict a device’s lifetime under extreme operating environments, like those experienced by space shuttles and wind turbines. These capabilities have been used to validate stronger oxide electronic materials for EVs and industrial energy applications.

These comprehensive component tests are important, because working backward from an integrated system is more difficult than getting all components on solid ground from the start. Just like the customized semiconductors stack into components, the tested components stack into a system or device. To package the components into devices, NREL’s facilities can prototype with 3D printers, connect components with a wire bonder, and analyze and characterize electrical performance. The systems are then screened as a whole for operational ruggedness and then hooked up to a virtual grid.

Parts of a Whole Power System
Power electronics consist of transistors, the same technology that exists in computers. The computer analogy extends to the grid, where power electronics are controllable and can orchestrate power in both critical and creative ways. NREL is even exploring the newfound possibilities for grid control to optimize power flow while also improving grid stability. As renewable energy propels growth in power electronics, their pervasiveness could inspire new architectures for the grid.

Researcher wears a mask to operate thermal test equipment
NREL’s facilities include advanced power electronics and electric machines (like the one pictured), which focus on systems for electric-drive vehicles that control the flow of electricity between the vehicle’s battery, the motor, and other powertrain components. Photo by Dennis Schroeder, NREL
To prepare for these possibilities, NREL’s grid simulators transport power electronics to real operational scenarios. For instance, the Power Electronics Grid Interface platform at NREL can link devices and prototypes to megawatts of power and a wide variety of energy technologies, including commercial wind turbines and solar arrays. With connections to supercomputer simulations, NREL’s cyber-physical environment can place devices at the center of a blackout or on an island microgrid and study their performance in recovering power or supporting a community.

“Most power is in some way flowing through power electronics, and in the future, that percentage is going to increase, so anything and everything that can make these devices more efficient, more flexible, and more application friendly will help save energy,” said Akanksha Singh, a power electronics researcher at NREL. “Power electronics are the building blocks to clean energy goals for the grid. Flexibility means that we can integrate more renewable energy sources, so we want to build on top of these systems as we design the future grid.”

Singh researches how to integrate power electronic converters onto the grid by developing controls for devices and evaluating those controls in grid scenarios. In one example, Singh is working with industry and university partners to design future power electronic converters that offer lighter, smaller, and more robust designs to mainstay grid technologies. In this project, NREL is actively designing and de-risking medium-voltage converter controls, which could be the key to a networked microgrid that features heightened flexibility and configurability.

Another example of power electronic controls involves the inverter, which interfaces all solar panels, battery devices, and electric vehicles and is commonly controlled to guard grid stability despite variable power coming from renewable energy sources. Inverter controls can already maintain 100%-renewable-energy-powered microgrids, and more advanced controls are on the way to enable continental-size grids to operate reliably and resiliently with 100% renewable energy sources. These grid-control efforts are drawing stakeholders from around the world to collaborate with NREL and contribute to the wholescale change effected by power electronics.

The Power of Partnerships
“All levels of partnerships are really essential to develop [power electronics] from scratch and take them to the market,” Singh said. “Everyone is doing research at different technology readiness levels; universities can get the small-level concept development, the national labs can build on top or even develop more advanced versions, and then industries can pick it up from there and commercialize it.”

As collaboration behind power electronics picks up momentum, NREL offers a particularly well-equipped environment to mobilize research and development. From the atomic to the systemic scales, NREL’s power electronics research is making progress for an evolving industry.