Micron-gap spacers with ultrahigh thermal resistance and mechanical robustness for direct energy conversion

Solar thermionic energy converters with micro-gap spacers

We present a solar thermionic energy converter (STEC) incorporating interelectrode spacer structures for solar energy harvesting. We demonstrate the impact of spacer loss on the optimal performance and gap size of STECs with and without interelectrode spacers. Under a solar concentration factor of 100, we show that the maximum efficiency of STECs with a spacer (5.3%) is significantly lower than that of STECs without a spacer (8.7%) at different optimal gaps due to the interelectrode spacer that conducts heat parasitically. The optimal gap ranges from a few tenths of a micron to a few microns for STECs without spacers, while the optimal gap is around 8μm for STECs with spacers. Furthermore, the device operation with an internal support structure offers new, to the best of our knowledge, insights into the resulting behavior of different energy exchange mechanisms in STECs, which distinguishes them from devices without spacers.

Information self-destruction module design based on micro thermoelectric power generation and energetic materials

Information self-destruction modules (ISDMs) play a vital role in the information security area. In this paper, an ISDM based on the integration of a micro-thermoelectric generation mechanism (M-TEGM) with energetic materials (EMs) is proposed. On the basis of energy conversion relationship, an open-loop electromotive force is induced, and this energy will drive the EMs to release the detonation wave and realize information storage module self-destruction. During the tests, under the temperature difference (100 K), the open-loop electromotive force (3.86 V) is induced by the M-TEGM and can drive the EMs (0.37 mg copper azide) to generate a detonation wave (GPa) in 3.4 μs, which can physically destroy the information storage modules. This ISDM has advantages that include rapid response times, low drive energy compared with traditional information security technology.

Progress Toward High Power Output in Thermionic Energy Converters

Thermionic energy converters are solid-state heat engines that have the potential to produce electricity with efficiencies of over 30% and area-specific power densities of 100 Wcm-2. Despite this prospect, no prototypes reported in the literature have achieved true efficiencies close to this target, and many of the most recent investigations report power densities on the order of mWcm-2 or less. These discrepancies stem in part from the low-temperature (<1300 K) test conditions used to evaluate these devices, the large vacuum gap distances (25-100 µm) employed by these devices, and material challenges related to these devices' electrodes. This review will argue that, for feasible electrode work functions available today, efficient performance requires generating output power densities of >1 Wcm-2 and employing emitter temperatures of 1300 K or higher. With this result in mind, this review provides an overview of historical and current design architectures and comments on their capacity to realize the efficiency and power potential of thermionic energy converters. Also emphasized is the importance of using standardized efficiency metrics to report thermionic energy converter performance data.

Novel concepts and nanostructured materials for thermionic-based solar and thermal energy converters

Thermal and concentrated solar solid-state converters are devices with no moving parts, corresponding to long lifetimes, limited necessity of maintenance, and scalability. Among the solid-state converters, the thermionic-based devices are attracting an increasing interest in the specific growing sector of energy conversion performed at high-temperature. During the last 10 years, hybrid thermionic-based concepts, conceived to cover operating temperatures up to 2000 °C, have been intensively developed. In this review, the thermionic-thermoelectric, photon-enhanced thermionic emission, thermionic-photovoltaic energy converters are extensively discussed. The design and development processes as well as the tailoring of the properties of nanostructured materials performed by the authors are comprehensively described and compared with the advances achieved by the international scientific community.

Wearable multi-sensing double-chain thermoelectric generator

Wearable electronics play a crucial role in advancing the rapid development of artificial intelligence, and as an attractive future vision, all-in-one wearable microsystems integrating powering, sensing, actuating and other functional components on a single chip have become an appealing tendency. Herein, we propose a wearable thermoelectric generator (ThEG) with a novel double-chain configuration to simultaneously realize sustainable energy harvesting and multi-functional sensing. In contrast to traditional single-chain ThEGs with the sole function of thermal energy harvesting, each individual chain of the developed double-chain thermoelectric generator (DC-ThEG) can be utilized to scavenge heat energy, and moreover, the combination of the two chains can be employed as functional sensing electrodes at the same time. The mature mass-fabrication technology of screen printing was successfully introduced to print n-type and p-type thermoelectric inks atop a polymeric substrate to form thermocouples to construct two independent chains, which makes this DC-ThEG flexible, high-performance and cost-efficient. The emerging material of silk fibroin was employed to cover the gap of the fabricated two chains to serve as a functional layer for sensing the existence of liquid water molecules in the air and the temperature. The powering and sensing functions of the developed DC-ThEG and their interactions were systematically studied via experimental measurements, which proved the DC-ThEG to be a robust multi-functional power source with a 151 mV open-circuit voltage. In addition, it was successfully demonstrated that this DC-ThEG can convert heat energy to achieve a 3.3 V output, matching common power demands of wearable electronics, and harvest biothermal energy to drive commercial electronics (i.e., a calculator). The integration approach of powering and multi-functional sensing based on this new double-chain configuration might open a new chapter in advanced thermoelectric generators, especially in the applications of all-in-one self-powered microsystems.