A team of engineers and material scientists in the Paul M. Rady Department of Mechanical Engineering at ���Ҵ�ý�ƽ������ has developed a new technology to turn thermal radiation into electricity in a way that literally teases the basic law of thermal physics.

The breakthrough was discovered by the , led by Assistant Professor Longji Cui. Their work, in collaboration with researchers from the National Renewable Energy Laboratory (NREL) and the University of Wisconsin-Madison, was recently .

The group says their research has the potential to revolutionize manufacturing industries by increasing power generation without the need for high temperature heat sources or expensive materials. They can store clean energy, lower carbon emissions and harvest heat from geothermal, nuclear and solar radiation plants across the globe.

In other words, Cui and his team have solved an age-old puzzle: how to do more with less.

“Heat is a renewable energy source that is often overlooked,” Cui said. “Two-thirds of all energy that we use is turned into heat. Think of energy storage and electricity generation that doesn’t involve fossil fuels. We can recover some of this wasted thermal energy and use it to make clean electricity.”

Breaking the physical limit in vacuum

High-temperature industrial processes and renewable energy harvesting techniques often utilize a thermal energy conversion method called thermophotovoltaics (TPV). This method harnesses thermal energy from high temperature heat sources to generate electricity.

But existing TPV devices have one constraint: Planck’s thermal radiation law.

PhD student Mohammad Habibi showcasing one of the group's TPV cells used for power generation. Habibi was the leader of both the theory and experimentation of this groundbreaking research.

“Planck’s law, one of most fundamental laws in thermal physics, puts a limit on the available thermal energy that can be harnessed from a high temperature source at any given temperature,” said Cui, also a faculty member affiliated with the Materials Science and Engineering Program and the Center for Experiments on Quantum Materials. “Researchers have tried to work closer or overcome this limit using many ideas, but current methods are overly complicated to manufacture the device, costly and unscalable.”

That’s where Cui’s group comes in. By designing a unique and compact TPV device that can fit in a human hand, the team was able to overcome the vacuum limit defined by Planck’s law and double the yielded power density previously achieved by conventional TPV designs.

“When we were exploring this technology, we had theoretically predicted a high level of enhancement. But we weren’t sure what it would look like in a real world experiment,” said Mohammad Habibi, a PhD student in Cui’s lab and leader of both the theory and experiment of this research. “After performing the experiment and processing the data, we saw the enhancement ourselves and knew it was something great.”

The zero-vacuum gap solution using glass

The research emerged, in part, from the group’s desire to challenge the limits. But in order to succeed, they had to modify existing TPV designs and take a different approach.

“There are two major performance metrics when it comes to TPV devices: efficiency and power density,” said Cui. “Most people have focused on efficiency. However, our goal was to increase power.”

The zero-vacuum gap TPV device, designed by the Cui Research Group.

To do so, the team implemented what’s called a “zero-vacuum gap” solution into the design of their TPV device. Unlike other TPV models that feature a vacuum or gas-filled gap between the thermal source and the solar cell, their design features an insulated, high index and infrared-transparent spacer made out of just glass.

This creates a high power density channel that allows thermal heat waves to travel through the device without losing strength, drastically improving power generation. The material is also very cheap, one of the device’s central calling cards.

“Previously, when people wanted to enhance the power density, they would have to increase temperature. Let’s say an increase from 1,500 C to 2,000 C. Sometimes even higher, which eventually becomes not tolerable and unsafe for the whole energy system,” Cui explained. “Now we can work in lower temperatures that are compatible with most industrial processes, all while still generating similar electrical power than before. Our device operates at 1,000 C and yields power equivalent to 1,400 C in existing gap-integrated TPV devices.”

The group also says their glass design is just the tip of the iceberg. Other materials could help the device produce even more power.

“This is the first demonstration of this new TPV concept,” explained Habibi. “But if we used another cheap material with the same properties, like amorphous silicon, there is a potential for an even higher, nearly 20 times more increase in power density. That’s what we are looking to explore next.”

The broader commercial impact

Assistant Professor Longji Cui (middle) and the Cui Research Group.

Cui says their novel TPV devices would make its largest impact by enabling portable power generators and decarbonizing heavy emissions industries. Once optimized, they have the power to transform high-temperature industrial processes, such as the production of glass, steel and cement with cheaper and cleaner electricity.

“Our device uses commercial technology that already exists. It can scale up naturally to be implemented in these industries,” said Cui. “We can recover wasted heat and can provide the energy storage they need with this device at a low working temperature.

“We have a patent pending based on this technology and it is very exciting to push this renewable innovation forward within the field of power generation and heat recovery.” 

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���Ҵ�ý�ƽ������ today announced seven winners of the 2023-2024 translational quantum research seed grants incentivizing quantum science and technology innovations launched from the lab to accelerate them along the development path to new programs and businesses.

In April 2023, the Colorado Economic Development Commission approved nearly $1.5 million to help connect discoveries from basic and applied research to Colorado’s startup ecosystem and provide effective pathways for Colorado students to enter the quantum workforce. These translational quantum research seed grants, which are being administered by ���Ҵ�ý�ƽ������, are one of the first results of that funding.

“Colorado’s wealth of academic and national laboratory researchers, along with a thriving ecosystem of established and startup quantum science and technology companies, provides one-of-a-kind opportunities for students, researchers and our workforce,” said Vice Chancellor for Research and Innovation and Dean of the Institutes Massimo Ruzzene. “The goal of these seed grants is to help researchers accelerate their discoveries towards commercialization. The success of quantum translation, of which these grants are a part, also has important implications for our national economy and national security.”

The awarded projects—rooted in research advances with demonstrable commercial potential—include three led by university researchers, all from ���Ҵ�ý�ƽ������, and four led by commercial enterprises that are pioneering the translation of quantum discoveries into products and services driving economic and everyday impact for Colorado and society. Each award provides $50,000 to advance each project and will be deployed over a period of 18 months. Additional seed grants will be made available through a similar process in each of the next two years.

“Colorado leads the world in quantum innovation, quantum companies and quantum jobs,” said Colorado Office of Economic Development and International Trade (OEDIT) Executive Director Eve Lieberman. “The seed grants announced today are an important step to connect quantum discoveries in the lab to the commercial sector, continuing our state’s leadership in this important new technology and supporting the creation of new businesses and new jobs.”

The seed grants—which were made available to any Colorado research institution or industry partner—are part of an increasing investment to expand on Colorado’s longstanding reputation as a hub of quantum science and technology discovery. The region’s legacy in the global quantum community is largely a result of decades of leadership and breakthroughs emanating from the triad of ���Ҵ�ý�ƽ������, NIST and JILA, including four Nobel Prizes in physics awarded to affiliated quantum researchers.

In the context of an accelerating global competition to realize the vast potential promised by quantum science and technology, the push for quantum advances has been the focus of considerable public- and private-sector investment across industries in recent years. In Colorado, quantum-related activity is extending beyond the traditional Boulder triad to include a growing web of interconnected ventures that are inventing and innovating to translate research advances into commercially viable products that advance frontiers of quantum to benefit society broadly.

The CUbit Quantum Initiative at ���Ҵ�ý�ƽ������—a leading player in both administering the grant program and facilitating the success of the university’s quantum research productivity—is an interdisciplinary hub for quantum research intended to advance the quantum ecosystem broadly. Crafted to focus the nexus of ���Ҵ�ý�ƽ������, the National Institute of Standards and Technology’s physics division (as a core component of JILA) and quantum-focused companies, CUbit aims to advance fundamental science and build a strong foundation for novel quantum technologies and their rapid dissemination, application and commercialization.

“Colorado already has the highest number of quantum-related companies in the nation,” said Scott Sternberg, executive director of CUbit. “These grants, and those in upcoming years, will help keep the translation pipeline healthy and thereby grow our economy.”

• Quantum Science & Technology

Translational Quantum Research Seed Grant Awards

*All awards are $50,000 and for a duration of 18 months

• Longji Cui: “Quantum electronics driven photocatalysis for efficient clean fuel generation and decarbonization”
  ���Ҵ�ý�ƽ������; Paul M. Rady Department of Mechanical Engineering
• Charlie Danaher: “Adaptive cooling technology”
  Danaher Cryogenics, Ltd.
• Rozhin Eskandarpour: “Translating quantum contingency analysis from lab to the field”
  Resilient Entanglement Inc.
• Murray Holland: “Developing a strontium optical lattice atom interferometer”
  ���Ҵ�ý�ƽ������; Department of Physics
• Poolad Imany: “Scalable optical cavity nonfabrication for efficient entanglement generation with artificial atoms”
  Icarus Quantum, Inc.
• Philip Makotyn: “Enabling technology for quantum applications: narrow linewidth innovative lasers”
  Vexlum US
• Greg Rieker: “Carcinogenic air pollutant monitoring with dual-comb spectroscopy”
  ���Ҵ�ý�ƽ������; Paul M. Rady Department of Mechanical Engineering

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Assistant Professor Longji Cui has received a prestigious  for research he hopes will improve the next generation of nanoelectronics and renewable energy technology.

As nanotechnology continues to miniaturize to near atomic scale, while simultaneously becoming more powerful, the need to understand heat transfer at the fundamental single molecule level becomes crucial. And yet the behavior of heat at the microscopic scale, and the ways in which it can be leveraged to make devices more efficient and less wasteful, is little understood.

With the help of this funding, Cui is looking to fill that knowledge gap. NSF CAREER Awards provide over $500,000 over a period of five years for early career faculty who are dedicated to research and education.

“One of the major challenges for the next generation of nanoelectronic devices is heat transport and dissipation,” Cui said. “When you’re at that smallest physical scale possible, heat is dissipating over a much smaller area, which makes the density of it even higher.”

Cui has remained focused on this problem throughout his academic career. In 2019, he published a groundbreaking paper in  called “,” which carried out the first study that measured thermal conductance through a single molecule.

Not only was Cui the first to make these measurements, but the tools and techniques with which he made them were of his own creation, too.

Cui developed a heat-detecting microscope that operates with sub-nanometer spatial resolution and picowatt (one trillionth of a watt) energy resolution. Called ultra-high resolution scanning thermal probe microscopy, or SThM, the microscope allowed Cui to carry out the measurements.

With the funding from the NSF CAREER Award, Cui will continue to push his research to the bleeding edge. In his experiments, Cui has begun to pioneer a new field called molecular phononics, which studies how certain quantum phononic effects could influence thermal transfer.

“Phonons are major carriers for thermal transport at the quantum level,” said Cui, “like electrons for electrical transport.”

Cui thinks a better understanding of different quantum electronic and phononic thermal effects could be crucial to improving heat dissipation and thermoelectric energy conversion at the microscopic level. 

This bottom-up approach to energy conversion could not only have outsized effects on the next generation of nanotechnology but on the field of renewable energy, too. Cui’s research will investigate how the conversion of heat to electricity at the molecular level could lead to a more efficient waste heat harvesting technology in the future.

“puts you in direct contact with some of the leading new fields in thermodynamics and quantum mechanics,” PhD student said. “He’s very ambitious.”

Cui wants the next generation of nanoengineers and thermal scientists to be at the vanguard of this research. He also wants to make sure that women and other groups underrepresented in engineering are a major part of this new generation.

“The cutting-edge fields of nano and quantum thermal engineering are something a mechanical engineer are perfectly suited for,” Cui said. “But first we need to update the curriculum.”

Cui is already teaching a class on quantum engineering for graduate students, but he wants to offer the class at the undergraduate level as well. Cui also plans on developing project-based, hands-on teaching modules for K-12 students that incorporate his expertise in ultra-high resolution scanning thermal probe microscopy.

 “Students know about the worlds of nano and quantum technology,” said Cui, “but we need to get it at their fingertips.”

Cui is a faculty member in the Paul M. Rady Department of Mechanical Engineering and the Materials Science and Engineering Program. Six faculty members from the College of Engineering and Applied Science received CAREER Awards in 2023.

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