Researchers at Rice University have discovered an innovative method to enhance a crucial component of thermophotovoltaic (TPV) systems, which transform heat into electricity using light. The engineering team, led by Gururaj Naik, applied a unique strategy inspired by quantum physics to develop a thermal emitter that achieves high efficiency while staying within practical design limits.
Researchers at Rice University have discovered an innovative way to enhance a vital part of thermophotovoltaic (TPV) systems, which convert heat into electricity using light. With a unique approach rooted in quantum physics, engineer Gururaj Naik and his team have created a thermal emitter capable of delivering high efficiencies within realistic design parameters.
This research may pave the way for the creation of thermal-energy electrical storage systems, which could serve as a cost-effective, large-scale alternative to traditional batteries. More broadly, efficient TPV technologies could support the growth of renewable energy – a crucial aspect of moving toward a net-zero future. Additionally, improved TPV systems can help recover waste heat from industrial operations, promoting sustainability. To contextualize this issue, approximately 20-50% of the heat used in transforming raw materials into consumer products is wasted, resulting in an economic loss exceeding $200 billion annually for the United States.
TPV systems consist of two key components: photovoltaic (PV) cells that convert light into electricity and thermal emitters that turn heat into light. For these systems to perform efficiently, both components must function optimally; however, most optimization efforts have concentrated on the PV cell.
“Traditional design methods limit the options for thermal emitter designs, leading to one of two outcomes: you either get practical but low-performing devices or high-performance emitters that are difficult to apply in real-world scenarios,” stated Naik, an associate professor of electrical and computer engineering.
In a recent study published in npj Nanophotonics, Naik and his former Ph.D. student, Ciril Samuel Prasad, who has recently earned a doctorate and is now a postdoctoral research associate at Oak Ridge National Laboratory, presented a new thermal emitter that achieves over 60% efficiency while being ready for application.
“We essentially demonstrated how to attain optimal performance for the emitter while adhering to realistic design constraints,” said Prasad, the study’s lead author.
This new emitter is made up of a tungsten metal sheet, a thin spacer layer, and a network of silicon nanocylinders. When heated, the base layers gather thermal radiation, which can be envisioned as a pool of photons. The tiny resonators positioned on top communicate in a way that enables them to “pluck” individual photons from this pool, regulating the brightness and spectrum of the light directed to the PV cell.
“Rather than concentrating on the performance of individual resonators, we considered how these resonators interact with one another, which opened up new possibilities,” Naik elaborated. “This allowed us to manage how the photons are stored and emitted.”
This selective emission, inspired by quantum physics principles, optimizes energy conversion and achieves higher efficiencies than previously achieved by operating at the materials’ limits. To surpass the newly attained 60% efficiency, it would require the development or discovery of new materials with superior properties.
Such advancements could make TPV a competitive contender against other energy storage and conversion technologies, such as lithium-ion batteries, especially in situations requiring long-term energy storage. Naik emphasized that this innovation could significantly impact industries that produce substantial amounts of waste heat, including nuclear power plants and manufacturing facilities.
“I am confident that what we have demonstrated here, combined with a highly efficient low bandgap PV cell, holds incredible potential,” Naik stated. “Drawing from my experience with NASA and launching a tech startup in renewable energy, I believe that energy conversion technologies are crucially needed today.”
The technology developed by the team might also find applications in space missions, such as powering rovers on Mars.
“If our technique can enhance efficiency from 2% to 5% in these systems, it would provide a significant improvement for missions dependent on effective power generation in extreme conditions,” Naik expressed.
The research received funding from the National Science Foundation (1935446) and the U.S. Army Research Office.
