Zhimin Yang

Using a multi-layer graphene-based emitter to improve the performance of a concentrated solar thermionic converter

A new model of the concentrated solar thermionic converter (CSTIC) with a multi-layer graphene (MLG)-based emitter is established. Based on the formulas of the thermionic emission from the MLG with ABA and ABC stacking orders, the power output and the efficiency of the CSTIC are derived. The performance characteristics of the CSTIC are discussed. It is revealed that the maximum efficiency of the CSTIC with the MLG-based emitter is higher than that with the single layer graphene (SLG)-based emitter, and the operating temperature of the MLG-based cathode is lower than that of the SLG-based cathode. It is important to find that the performances of the CSTIC with the ABA stacked graphene are better than those with the ABC stacked graphene. The optimum surface work function of the MLG-based cathode at the maximum efficiency is larger than the work function of the SLG-based cathode so that the CSTIC with the MLG-based emitter can be experimentally implemented more easily than the CSTIC with the SLG-based emitter.A new model of the concentrated solar thermionic converter (CSTIC) with a multi-layer graphene (MLG)-based emitter is established. Based on the formulas of the thermionic emission from the MLG with ABA and ABC stacking orders, the power output and the efficiency of the CSTIC are derived. The performance characteristics of the CSTIC are discussed. It is revealed that the maximum efficiency of the CSTIC with the MLG-based emitter is higher than that with the single layer graphene (SLG)-based emitter, and the operating temperature of the MLG-based cathode is lower than that of the SLG-based cathode. It is important to find that the performances of the CSTIC with the ABA stacked graphene are better than those with the ABC stacked graphene. The optimum surface work function of the MLG-based cathode at the maximum efficiency is larger than the work function of the SLG-based cathode so that the CSTIC with the MLG-based emitter can be experimentally implemented more easily than the CSTIC with the SLG-based emitter.

Coulomb-coupled quantum-dot thermal transistors

A quantum-dot thermal transistor consisting of three Coulomb-coupled quantum dots coupled to respective electronic reservoirs by tunnel contacts is established. The heat flows through the collector and emitter can be controlled by the temperature of the base. It is found that a small change in the base heat flow can induce a large heat flow change in the collector and emitter. The huge amplification factor can be obtained by optimizing the Coulomb interaction between the collector and the emitter or by decreasing the energy-dependent tunneling rate at the base. The proposed quantum-dot thermal transistor may open up potential applications in low-temperature solid-state thermal circuits at the nanoscale.

Performance Evaluation and Parametric Optimum Choice Criteria of a Near-Field Thermophotovoltaic Cell

Based on the near-field (NF) model of a thermophotovoltaic cell (TPVC) consisting of an emitter and a photovoltaic (PV) cell separated by a vacuum gap, two important formulas for the power output and efficiency are analytically derived by using fluctuation electrodynamics theory. The general performance characteristics of the NF-TPVC are evaluated. The optimum choice criteria of several key parameters, such as the power output density, efficiency, and distance of the vacuum gap of the TPVC, the current density and voltage output of the PV cell, and the band-gap of semiconductor materials in the PV cell, are supplied. Moreover, the maximum power output densities and efficiencies of three NF-TPVCs made of InSb, InAs, and InGaAsSb are calculated and the corresponding optimum values of other parameters are determined. The results obtained may provide some theoretical guidance for engineers to optimally design NF-TPVCs.