Reviewed by Lexie CornerNov 22 2024
Researchers at Rice University have discovered a novel method to enhance a crucial component of thermophotovoltaic (TPV) systems, which use light to convert heat into power. This research was published in npj Nanophotonics.
A new thermal emitter (right) developed by Rice University engineers, composed of a tungsten metal sheet, a thin layer of spacer material, and a network of silicon nanocylinders, promises efficiencies of over 60 %. Image Credit: Gustavo Raskosky/Rice University
Rice engineer Gururaj Naik and his colleagues developed a thermal emitter that can achieve high efficiency within practical design parameters by using an approach inspired by quantum physics.
The study could contribute to the advancement of thermal-energy electrical storage, which has potential as a cost-effective, grid-scale battery alternative. More broadly, effective TPV technologies could support the growth of renewable energy, which is important for transitioning to a net-zero future.
Recovering waste heat from industrial processes enhances the sustainability of TPV systems, which is another notable benefit. To put this into perspective, the United States economy loses over $200 billion annually due to the waste of 20–50 % of the heat used in converting raw materials into consumer goods.
Photovoltaic (PV) cells, which convert light into electricity, and thermal emitters, which convert heat into light, are the two main components of TPV systems. For the system to be effective, both parts must function properly, but the PV cell has received more attention in efforts to optimize these systems.
Using conventional design approaches limits thermal emitters’ design space, and what you end up with is one of two scenarios: practical, low-performance devices or high-performance emitters that are hard to integrate in real-world applications.
Gururaj Naik, Associate Professor, Rice University
In a new study, Naik and his former Ph.D. student, Ciril Samuel Prasad, displayed a new thermal emitter that offers efficiencies of over 60 % while being application-ready.
We essentially showed how to achieve the best possible performance for the emitter given realistic, practical design constraints.
Ciril Samuel Prasad, Study First Author and Postdoctoral Research Associate, Oak Ridge National Laboratory
The emitter consists of a tungsten metal sheet, a thin layer of spacer material, and a network of silicon nanocylinders. When heated, the base layers gather thermal radiation, forming a photon bath. The tiny resonators on top “talk” to each other in such a way that they can “pluck photon by photon” from this bath, adjusting the brightness and bandwidth of the light transmitted to the PV cell.
“Instead of focusing on the performance of single-resonator systems, we instead took into account the way these resonators interact, which opened up new possibilities. This gave us control over how the photons are stored and released,” Naik added.
This selective emission, accomplished through quantum physics insights, maximizes energy conversion and enables higher efficiencies than previously conceivable while operating at the limits of the materials’ characteristics. To improve on the recently obtained 60 % efficiency, new materials with superior qualities must be developed or discovered.
These advancements could make TPV a viable option for other energy storage and conversion technologies, such as lithium-ion batteries, especially in circumstances requiring long-term energy storage. Naik stated that this breakthrough has significant ramifications for companies that create a lot of waste heat, such as nuclear power stations and manufacturing facilities.
Naik stated, “I feel confident that what we have demonstrated here, coupled with a very efficient low bandgap PV cell, has very promising potential. Based on my own experience working with NASA and launching a startup in the renewable energy space, I think that energy conversion technologies are very much in need today.”
The team’s innovation might also be employed in space, such as to power rovers on Mars.
Naik concluded, “If our approach could lead to an increase in efficiency from 2 % to 5 % in such systems, that would represent a significant boost for missions that rely on efficient power generation in extreme environments.”
National Science Foundation (1935446) and the US Army Research Office supported the study.
Journal Reference:
Prasad, C. S. and Naik, G. V (2024) Non-Hermitian selective thermal emitter for thermophotovoltaics. npj Nanophotonics. doi.org/10.1038/s44310-024-00044-3