Thermoelectric converter: Strategies from materials to device application

Thermal management of thermoelectric generators for waste energy recovery

The energy selective electron device works among electron reservoirs with different temperatures and chemical potentials. Electrons obey the Fermi-Dirac distribution, and with the help of resonant filters, a part of electrons with specific energy levels can tunnel among reservoirs and provide current to an external circuit. Herein, an irreversible three-terminal energy selective electron generator model is proposed. Using statistical mechanics and finite-time-thermodynamics, analytical expressions of power and efficiency are derived, and the optimal performance of the device is investigated. Results show that the central energy level difference of filters, the chemical potential difference of low-temperature reservoirs, the interval of mean-central-energy-level of filters and the mean-chemical-potential of low-temperature reservoirs can be optimized to maximize power and efficiency. On the basis of power and efficiency analyses, performance characteristics under different objective functions, including efficient power and ecological function, are discussed and the corresponding optimal performance regions are obtained. The relationship between the entropy generation rate and the efficiency is investigated, and it is shown that the minimum-entropy-generation-state does not coincide with the maximum-efficiency-state.

Performance optimization of three-terminal energy selective electron generators

Comparison between spectrum-split conversion and thermophotovoltaic for solar energy utilization: Thermodynamic limitation and parametric analysis

Kirchoff's Law, as originally conceived, applies only to samples in thermal equilibrium with their surroundings. Most laboratory measurements of emissivity only approach this condition and it never applies in remote sensing applications. In particular, the background is often much cooler than the radiating sample, and this has led to a long controversy about the applicability of Kirchhoff's Law under such conditions. It has also led to field and laboratory measurement techniques that use some form of the 'emissivity box' approach, which surrounds the sample with a background as close as possible to the sample temperature. In our experiments, we have heated soil samples in air on a hot plate in the laboratory to a much higher temperature than the room temperature background. Spectral emissivity was measured, except the known emissivities of both the primary and secondary Christiansen features were used, instead of assuming an emissivity of unity at these wavelengths. The results from this investigation are discussed in brief.

Thermal infrared remote sensing and Kirchhoff's law: 1. Laboratory measurements

Optimum matching of photovoltaic–thermophotovoltaic cells efficiently utilizing full-spectrum solar energy

Efficiency enhancement of an updated solar-driven intermediate band thermoradiative device

An updated thermionic converter was established through the introduction of a graphene anode and an optical reflector, significantly decreasing the irreversible losses inside the device and enhancing the device performances. At 1940 K, the maximum efficiency and power output density of the converter reached 76.6 % and 95.1 W c m − 2. The optimum performances of the proposed model were obviously better than those achieved using a graphene-anode thermionic converter without a reflector and a traditional thermionic converter with a metal anode. Importantly, the optimal regions of the key parameters were determined for the different temperatures of the heat source and the parametric selection criteria and design strategies for the proposed model are also provided. These are extremely important as they may facilitate the implementation of the device.

Graphene-anode thermionic converter demonstrating total photon reflection

The maximum efficiency enhancement of a solar-driven graphene-anode thermionic converter realizing total photon reflection

Based on nanoelectronic devices that can act as power generators or refrigerators, the relations between the entropy production rate and the thermal efficiency or coefficient of performance are obtained for two types of electron filters. It is found that the decrease of the entropy production rate does not always guarantee the increase of the thermal efficiency or coefficient of performance, indicating that the state of the minimum entropy production rate does not correspond to that of the maximum thermal efficiency or coefficient of performance in these electronic devices. It implies the fact that different from the thermal efficiency or coefficient of performance, the entropy production rate is not a good objective function for optimizing the performance of electronic devices. However, entropy analyses will be helpful to deeply understanding the thermodynamic properties of electronic devices. These results obtained here will provide a feasible scheme to further optimize and improve the performances of electronic devices.

Cong Hu

Papers

Optimum matching of photovoltaic–thermophotovoltaic cells efficiently utilizing full-spectrum solar energy

Efficiency enhancement of an updated solar-driven intermediate band thermoradiative device

Graphene-anode thermionic converter demonstrating total photon reflection

The maximum efficiency enhancement of a solar-driven graphene-anode thermionic converter realizing total photon reflection

Entropy analyses of electronic devices with different energy selective electron tunnels