A record thermoelectric efficiency in tellurium-free modules for low-grade waste heat recovery

Low-grade heat accounts for >50% of the total dissipated heat sources in industries. An efficient recovery of low-grade heat into useful electricity not only reduces the consumption of fossil-fuels but also releases the subsequential environmental-crisis. Thermoelectricity offers an ideal solution, yet low-temperature efficient materials have continuously been limited to Bi2Te3-alloys since the discovery in 1950s. Scarcity of tellurium and the strong property anisotropy cause high-cost in both raw-materials and synthesis/processing. Here we demonstrate cheap polycrystalline antimonides for even more efficient thermoelectric waste-heat recovery within 600 K than conventional tellurides. This is enabled by a design of Ni/Fe/Mg3SbBi and Ni/Sb/CdSb contacts for both a prevention of chemical diffusion and a low interfacial resistivity, realizing a record and stable module efficiency at a temperature difference of 270 K. In addition, the raw-material cost to the output power ratio in this work is reduced to be only 1/15 of that of conventional Bi2Te3-modules.

Zinc ion thermal charging cell for low-grade heat conversion and energy storage

Converting low-grade heat from environment into electricity shows great sustainability for mitigating the energy crisis and adjusting energy configurations. However, thermally rechargeable devices typically suffer from poor conversion efficiency when a semiconductor is employed. Breaking the convention of thermoelectric systems, we propose and demonstrate a new zinc ion thermal charging cell to generate electricity from low-grade heat via the thermo-extraction/insertion and thermodiffusion processes of insertion-type cathode (VO2-PC) and stripping/plating behaviour of Zn anode. Based on this strategy, an impressively high thermopower of ~12.5 mV K−1 and an excellent output power of 1.2 mW can be obtained. In addition, a high heat-to-current conversion efficiency of 0.95% (7.25% of Carnot efficiency) is achieved with a temperature difference of 45 K. This work, which demonstrates extraordinary energy conversion efficiency and adequate energy storage, will pave the way towards the construction of thermoelectric setups with attractive properties for high value-added utilization of low-grade heat.

The vortex layer apparatus as a source of low-grade heat in the process of pretreatment of the substrate before anaerobic digestion

The limiting stage of anaerobic digestion (AD) of organic waste is the hydrolysis of particulate organic matter. One of the most promising and energy-efficient methods of waste pretreatment before AD is its processing in a vortex layer apparatus (VLA). The work was aimed at experimentally determining the energy characteristics of VLA. The description of the experimental plant and its energy balance were given. The ranges of electricity consumption and heat generation were shown. According to experimental data, the coefficient of conversion of electricity into heat was in the range of 0.367-0.515 at a cooling water temperature of 10.6-11.7 oC. Based on the experimental data obtained, it can be argued that VLA is a stable source of low-grade heat that can be utilized using heat pumps.