Solid-state cooling by elastocaloric polymer with uniform chain-lengths

Although the elastocaloric effect was found in natural rubber as early as 160 years ago, commercial elastocaloric refrigeration based on polymer elastomers has stagnated owing to their deficient elastocaloric effects and large extension ratios. Herein, we demonstrate that polymer elastomers with uniform molecular chain-lengths exhibit enormous elastocaloric effects through reversible conformational changes. An adiabatic temperature change of −15.3 K and an isothermal entropy change of 145 J kg−1 K−1, obtained from poly(styrene-b-ethylene-co-butylene-b-styrene) near room temperature, exceed those of previously reported elastocaloric polymers. A rotary-motion cooling device is tailored to high-strains characteristics of rubbers, which effectively discharges the cooling energy of polymer elastomers. Our work provides a strategy for the enhancement of elastocaloric effects and could promote the commercialization of solid-state cooling devices based on polymer elastomers.

Colossal Barocaloric Effects with Ultralow Hysteresis in Two-Dimensional Metal–Halide Perovskites

Nearly 4,400 TWh of electricity—20% of the total consumed in the world—is used each year by refrigerators, air conditioners, and heat pumps for cooling. In addition to the 2.3 Gt of carbon dioxide emitted during the generation of this electricity, the vapor-compression-based devices that provided the bulk of this cooling emitted fluorocarbon refrigerants with a global warming potential equivalent to 1.5 Gt of carbon dioxide into the atmosphere. With population and economic growth expected to dramatically increase over the next several decades, the development of alternative cooling technologies with improved efficiency and reduced emissions will be critical to meeting global cooling needs in a more sustainable fashion. Barocaloric materials, which undergo thermal changes in response to applied hydrostatic pressure, offer the potential for solid-state cooling with high energy efficiency and zero direct emissions, as well as faster start-up times, quieter operation, greater amenability to miniaturization, and better recyclability than conventional vapor-compression systems. Efficient barocaloric cooling requires materials that undergo reversible phase transitions with large entropy changes, high sensitivity to hydrostatic pressure, and minimal hysteresis, the combination of which has been challenging to achieve in existing barocaloric materials. Here, we report a new mechanism for achieving colossal barocaloric effects near ambient temperature that exploits the large volume and conformational entropy changes of hydrocarbon chain-melting transitions within two-dimensional metal–halide perovskites. Significantly, we show how the confined nature of these order–disorder phase transitions and the synthetic tunability of layered perovskites can be leveraged to reduce phase transition hysteresis through careful control over the inorganic–organic interface. The combination of ultralow hysteresis (< 1.5 K) and high barocaloric coefficients (> 20 K/kbar) leads to large reversible isothermal entropy changes (> 200 J/kg•K) at record-low pressures (< 300 bar). We anticipate that these results will help facilitate the development of barocaloric cooling technologies and further inspire new materials and mechanisms for efficient solid-state cooling.

Colossal barocaloric effects in the complex hydride Li$$_{2}$$B$$_{12}$$H$$_{12}$$

Traditional refrigeration technologies based on compression cycles of greenhouse gases pose serious threats to the environment and cannot be downscaled to electronic device dimensions. Solid-state cooling exploits the thermal response of caloric materials to changes in the applied external fields (i.e., magnetic, electric and/or mechanical stress) and represents a promising alternative to current refrigeration methods. However, most of the caloric materials known to date present relatively small adiabatic temperature changes ($$|\Delta T| \sim 1$$ | Δ T | ∼ 1 to 10 K) and/or limiting irreversibility issues resulting from significant phase-transition hysteresis. Here, we predict by using molecular dynamics simulations the existence of colossal barocaloric effects induced by pressure (isothermal entropy changes of $$|\Delta S| \sim 100$$ | Δ S | ∼ 100 J K$$^{-1}$$ - 1 kg$$^{-1}$$ - 1 ) in the energy material Li$$_{2}$$ 2 B$$_{12}$$ 12 H$$_{12}$$ 12 . Specifically, we estimate $$|\Delta S| = 367$$ | Δ S | = 367 J K$$^{-1}$$ - 1 kg$$^{-1}$$ - 1 and $$|\Delta T| = 43$$ | Δ T | = 43 K for a small pressure shift of P = 0.1 GPa at $$T = 480$$ T = 480 K. The disclosed colossal barocaloric effects are originated by a fairly reversible order–disorder phase transformation involving coexistence of Li$$^{+}$$ + diffusion and (BH)$$_{12}^{-2}$$ 12 - 2 reorientational motion at high temperatures.

Colossal Barocaloric Effects in The Complex Hydride Li2B12H12

Traditional refrigeration technologies based on compression cycles of greenhouse gases pose serious threats to the environment and cannot be downscaled to electronic device dimensions. Solid-state cooling exploits the thermal response of caloric materials to external fields and represents a promising alternative to current refrigeration methods. However, most of the caloric materials known to date present relatively small adiabatic temperature changes (|ΔT| ~ 1 K) and/or limiting irreversibility issues resulting from significant phase-transition hysteresis. Here, we predict the existence of colossal barocaloric effects (isothermal entropy changes of |ΔS| ~ 100 JK-1 kg-1) in the energy material Li2B12H12 by means of molecular dynamics simulations. Specifically, we estimate |ΔS| = 367 JK-1 kg-1 and |ΔT| = 23 K for an applied pressure of P = 0.1 GPa at T = 480 K. The disclosed colossal barocaloric effects are originated by an fairly reversible order-disorder phase transformation involving coexistence of Li+ diffusion and (BH)12-2 reorientational motion at high temperatures.

Printed flexible thermoelectric materials and devices

The innate capability of direct heat-electricity conversion endows thermoelectric (TE) materials great application potential in the fields of low-grade heat harvesting, solid-state cooling, and sensing. Recently, the rapid development of...