Studies of Heat Transport and its Underlying Stochastic Dynamics in Smallest Thermal Engines: An Approach to Novel Form of Energy-Harvesting

United States Army is currently operating on the battlefields of several areas worldwide. To complete their battlefield missions successfully, powering individual soldiers is critical, which enables them to exploit both energy and data for their own missions, based on the concept of ÒSmart Battlefield Energy on-DemandÓ. An urgent requirement in the military energy technology is that combatants have a demand for small and lightweight (portable) devices functioning for a sufficiently long period without additional energy resupply, so as to come to be Òenergy-readyÓ, especially in isolated and adverse battlefield environments. Therefore, there is a considerable need to improve our understanding of the fundamental limits and efficiencies of small-scale energy systems, as well as the associated nano science and technology, and then to examine possibilities for a scaling-up of the nanoscopic energy- harvesting/transport mechanisms toward larger systems. This will finally enable to enlarge our knowledge about the optimized management of thermal, chemical and mechanical energy at macro level as well. However, the difficulties confronted by this research task arise typically from the deficiency in a fundamental and systematic understanding of the underlying thermodynamics for the energy-harvesting mechanism occurring in such systems. In the project, we take into consideration the fundamental issues challenged in nano/quantum thermodynamics, such as Òhow does a scaling down into the nano-scale regime affect oneÕs capability of defining thermodynamic variables as well as building and controlling the thermodynamic engines?Ó We will study some specific representative architecture models of the quantum-mechanical engines in the small scale. Quantum-thermodynamics has attracted considerable attention, due to the need for enhancing our understanding of various propulsion systems in high performance in the context of DoD interest, e.g., during the continued miniaturization of unmanned aerial vehicles for high-level battlefield missions in future. In fact, there have recently been remarkable theoretical breakthroughs in the multi-scale (i.e., from nano to macro) thermodynamics community, which can critically deepen our understanding of the optimized performance of multi-scale devices in the thermal environments. This is actually a fundamentally game-changing conceptual achievement, in particular as compared with an old view widespread for a long time such as the remark in the mid 1970s, ``We may be reasonably sure that a treatise on, say, thermodynamics, published in the year 2000 will not be fundamentally different from one available today, .'' [Phys. Today, March p57 (1974)]. One of the breakthroughs is the celebrated Jarzynski equality, which systematically connects to the Second Law of thermodynamics formulated in the well- known inequality, W = ÀF, in which the symbol W denotes an amount of work done irreversibly onto the system-of-interest while ÀF the free energy change, being tantamount to the minimum work, obtainable only through the corresponding reversible process. The Jarzynski equality is very useful, especially for small-scale systems with the large fluctuations caused by their non- negligible interactions with the environments...