Non-Equilibrium Electron Thermodynamics for Solid-state Power Generation and Deep Cryocooling of Electronic Devices 21-000000065
Abstract
We propose a novel research project that can significantly enhance energy conversion efficiency between heat and electricity using non-equilibrium electrons (NEs) in solids. This research addresses a critical need because it will help to create new highly efficient generators or cryocoolers. We refer to this thermodynamic cycle as two-dimensional non-equilibrium electron gas (2D NEG) cycle. The NEs behave as Fermi gas over short time scale, where a thermodynamic cycle can be engineered in analogy to existing thermodynamic cycles of mechanical heat engines implemented for solid-state power generation. NE has unique hydrodynamic properties before electronlattice scattering dominates the transport. Research indicates this is the first investigation of non-equilibrium electron gas in solids for thermodynamic cycles or even as a working fluid. A very preliminary investigation was published in Applied Physics Letters [1], and this is our first proposal to do more in-depth studies that can lay the foundation for experimental demonstration. We formulate an analogy to a thermodynamic cycle with an ideal heat engine wherein we use: (1) non-equilibrium high energy state electrons in short time or length scales to avoid scattering with lattice, (2) a geometric concentration of NEs with applied electricalfield (gating) to pressurize NE gas as an effective compression part of the thermodynamic cycle along with localized heating at highly concentrated interface, and (3) releasing the pressure and allowing the electrons to expand into the closed circuit to complete the cycle and convert the heat into electricity. Since irreversibility of state-of-the-art thermodynamic cycles comes from the parasitic heat conduction, this feature suggests a significantly higher efficiency. Solid-state thermodynamic conversion has a big potential to realize a multiarray of ultra-small devices for high power per weight or per volume and low cost with a large volume production. The proposed structure is compatible with well-established semiconductor technologies. The reverse thermodynamic process (cooling) also fits to Complementary Metal-Oxide Semiconductor (CMOS) technology and has the potential to be adopted as a part of integrated circuits to selectively cool high-power transistors or low-noise cryogenic sensors. High-temperature (>600 oC) and high-power density power generation is the main focus of this project, demonstrating the potential of mobile and compact direct energy conversiondevices. However, higher efficiency by preventing lattice heat loss may also be applicable to relatively lower grade heat recovery applications with heat source temperature of 500 oC 600 oC range. The reverse 2D NEG cycle, i.e., the cooling cycle of NEs is potentially applicable to removing the excess heat energy (due to the power loss) from the electronic devices including logic and power transistors. This reverse thermodynamic process will also be investigated.Monte Carlo simulations of NEs will be conducted for some key 2D electron gas devices of different dimensions at various operating temperatures and cycle frequencies. The thermodynamic parameters can be controlled by carrier concentration and electron density of states in the material. Simulations will allow us to determine and optimize achievable power density and efficiency for the proof-of-concept devices which can be fabricated in the next phase.Approved for Public Release1 K. Yazawa and A. Shakouri, Appl. Phys. Lett. 109(4) 043904, (2016).
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Aug 05, 2021
- Source ID
- N000142112697
Entities
People
- Kazuaki Yazawa
Organizations
- Office of Naval Research
- Purdue University
- United States Navy