Imagine a technology that can convert, amplify, limit, filter, control, and transform electricity in countless ways to supply power to the electrical 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.
“In multiple ways, the fate of energy systems is linked with progress in power electronics," said Sreekant Narumanchi, a senior power electronics and electric machines 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.
Once made of vacuum 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 performance and durability — but not so strong that electrons can’t flow freely. We also need to be able to control how those electrons flow,” said Brooks Tellekamp, a materials physics researcher at NREL. “Balancing these factors can lead to difficult physics.”
Tellekamp works with semiconductor materials that are so small that a slight atomic difference can result in distinctly better or worse performance. To study the materials at such detail, he 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.
“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.”
Combining power electronic components at multiple scales is necessary to create 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.
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 conditions 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.
NREL is exploring the newfound possibilities for control of the electrical grid 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.
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.
To meet decarbonization goals across the transportation sector, NREL researchers are pioneering improved power electronics and electric motor packaging, semiconductor electro-thermal designs, and thermal management systems. Narumanchi’s team specializes in cutting-edge system designs for electrified mobility to decrease costs, reduce component footprints, and improve overall performance, reliability, and efficiency in advanced power electronics and electric machines for various vehicle applications.
Alongside extensive expertise in light-, medium- and heavy-duty electric vehicle designs, recent partnerships focus on designing and developing power electronics and electric motors to optimize energy use in next-generation sustainable aircraft.