Quantum-inspired design improves heat-to-electricity conversion efficiency

Reactor used to test new heat emitters (left). Gururaj Naik (right). Credit: Gustavo Raskosky / Rice University
Researchers at Rice University have discovered a new way to improve a key element of thermophotovoltaic (TPV) systems, which convert heat to electricity through light. Using an unconventional approach inspired by quantum physics, Rice engineer Gururaj Naik and his team designed a thermal emitter that can achieve high efficiency within practical design parameters. .
This research could aid in the development of thermal energy storage, which holds promise as an affordable grid-scale alternative to batteries. More broadly, efficient TPV technology has the potential to accelerate the growth of renewable energy, an essential element of the transition to a net-zero world. Another big advantage of better TPV systems is that they recover waste heat from industrial processes, making them more sustainable. To put this into context, up to 20-50% of the heat used to turn raw materials into consumer goods ends up being wasted, costing the U.S. economy more than $200 billion annually.
TPV systems include two main components: photovoltaic (PV) cells, which convert light to electricity, and thermal emitters, which convert heat to light. Both of these components must function properly for the system to be efficient, but efforts to optimize them have focused on solar cells.
“Using traditional design approaches limits the design space for thermal emitters, ultimately resulting in one of two scenarios: a practical low-performance device, or a device that is difficult to integrate into real-world applications. It’s a high-performance emitter,” said Naik. Associate Professor of Electrical and Computer Engineering.
In a new study published in npj Nanophotonics, Naik and his former Ph.D. student Cyril Samuel Prasad, who went on to earn a Ph.D. (who has assumed a postdoctoral role at the University of California) demonstrated a new heat emitter that promises an efficiency of more than 60%, even though it is an applied product. -Ready.
“We essentially showed how to achieve the best possible performance of an emitter, given practical and practical design constraints,” said Prasad, lead author of the study. Ta.
The emitter consists of a tungsten metal sheet, a thin layer of spacer material, and a network of silicon nanocylinders. When heated, the base layer accumulates thermal radiation. You can think of this as a bath of photons. Small resonators at the top “talk” to each other in a way that allows them to extract “photon by photon” from this bath, controlling the brightness and bandwidth of the light sent to the solar cells.


A new heat emitter developed by Rice University engineers is composed of a tungsten metal sheet, a thin layer of spacer material, and a network of silicon nanocylinders, and promises to be more than 60% efficient. Credit: Gustavo Raskosky / Rice University
“Rather than focusing on the performance of a single resonator system, we instead took into account the way these resonators interact. This opens up new possibilities,” says Naik. explained. “This allows us to control how the photons are stored and released.”
This selective emission is achieved through insights from quantum physics to maximize energy conversion, enable higher efficiencies than previously possible, and operate at the limits of material properties. To improve on the newly achieved 60% efficiency, new materials with better properties must be developed or discovered.
These advantages could make TPVs a competitive alternative to other energy storage and conversion technologies such as lithium-ion batteries, especially in scenarios where long-term energy storage is required. Naik noted that this innovation has important implications for industries that generate large amounts of waste heat, such as nuclear power plants and manufacturing facilities.
“We believe that what we have demonstrated here has very promising potential when combined with highly efficient low bandgap solar cells,” Naik said. “Based on my own experience working with NASA and launching startups in the renewable energy space, I think energy conversion technologies are very needed today.”
The team’s technology could also be used in space applications, such as powering Mars rovers.
“If our approach can improve the efficiency of such systems from 2% to 5%, it would be a significant improvement for missions that rely on efficient power generation in extreme environments,” Naik said. said.
Further information: Ciril Samuel Prasad et al., Non-Hermitian selective thermal emitters for thermophotovoltaics, npj nanophotonics (2024). DOI: 10.1038/s44310-024-00044-3
Provided by Rice University
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