Using only pressure control, a Chinese research team has created a novel concept to extract thermal energy from low-temperature waste heat sources and reusing it as needed.
Barocaloric thermal batteries, based on the distinctive inverse barocaloric effect, have been developed by Chinese scientists. By simply adjusting the pressure, they can use this to extract thermal energy from low-temperature waste heat sources and reuse it as needed.
Using only pressure control, a Chinese research team has created a novel concept to extract thermal energy from low-temperature waste heat sources and reusing it as needed.
More than 50% of the total energy used in the world is used to produce heat, and an analysis of waste heat potential reveals that 72% of the primary energy used in the world is lost after conversion, primarily in the form of heat. Additionally, it is the cause of more than 30% of the world’s greenhouse gas emissions.
In light of this, scientists at the Institute of Metal Research of the Chinese Academy of Sciences, under the direction of Prof. LI Bing, have developed and proposed a novel idea: barocaloric thermal batteries, which are based on the distinctive inverse barocaloric effect.
In sharp contrast to a typical barocaloric effect, where pressurisation results in an exothermic response, the inverse barocaloric effect is characterised by a pressure-induced endothermic response.
According to Prof. LI, the study’s corresponding author, “a barocaloric thermal battery cycle consists of three steps, including thermal charging upon pressurisation, storage with pressure, and thermal discharging upon depressurization.”
Ammonium thiocyanate served as the material for the barocaloric thermal battery (NH4SCN). The heat of the discharge, or a rise in temperature of about 15 K, was 43 J g1. The mechanical energy input was outweighed by the heat produced by 11 times.
Utilizing synchrotron X-ray and neutron scattering techniques, the working material NH4SCN has been thoroughly characterised in order to comprehend the physical basis of the distinctive inverse barocaloric effect.
At 363 K, it transitions from a monoclinic to an orthorhombic phase in terms of its crystal structure, with entropy changes of about 128 J kg1 K1 and volumetric negative thermal expansion of about 5%.
It is the first inverse barocaloric system with entropy changes greater than 100 J kg-1K-1 and is easily driven by pressures as low as 40 MPa.
Pressure increases the transverse vibrations of SCN anions, which weakens the hydrogen bonds that make up the long-range order, as demonstrated by pressure-dependent neutron scattering and molecular dynamics simulations.
In response to external pressure, the system becomes disorganized, which causes the material to absorb heat from the environment.
Barocaloric thermal batteries are anticipated to play a significant role in a number of applications including low-temperature industrial waste heat harvesting and reuse, solid-state refrigeration heat transfer systems, smart grids, and residential heat management as an emerging solution for manipulating heat.
The National Natural Science Foundation of China, the Ministry of Science and Technology of China, and CAS all provided funding for this study.