High-temperature heat pumps (HTHPs) are emerging as pivotal technologies for decarbonizing industrial heat supply by upgrading low-grade waste heat to meet diverse thermal demands. This review summarizes and analyzes the current state, applications and future trends of HTHPs from a carbon–neutral perspective. Core technological aspects—including cycle configurations, refrigerants, compressors, and integration strategies—are systematically analyzed. Thermodynamic comparisons reveal that cascade and coupled cycles can achieve temperature lifts above 100 °C under optimized conditions. The transition from high global warming potential (GWP) hydrofluorocarbons toward low-GWP hydrofluoroolefins, hydrochlorofluoroolefins, and natural refrigerants is accelerating. Large-capacity screw and centrifugal compressors are identified as key enablers for industrial-scale deployment. Typical industrial deployments of HTHPs across various fields are introduced, mainly structured around their application potential, integration characteristics, and implementation methods within energy-intensive sectors (e.g., paper manufacturing, textile dyeing). Future development will focus on high-power systems, advanced working fluid design, and digital control integration with renewable power and thermal storage. Collectively, HTHPs constitute an essential electrification pathway for achieving deep industrial decarbonization and carbon–neutral energy systems.

This study presents the development and evaluation of a novel partially open-loop heat pump dryer with a unit-room (HPDU). The unit-room was designed to enable the ambient air to be mixed with the return air, thereby reducing the influence of the ambient air on the system performance, while maintaining a high system thermal efficiency. A modelling system for the HPDU was developed and validated based on a real-scale experimental study. By using the modelling system, the system characteristics under different ambient conditions and bypass factors were analyzed. The energy benefit of the proposed HPDU was quantified through a comparative study with a closed-loop heat pump dryer (CHPD). It is evident that a maximal specific moisture extraction rate (SMER) and a minimal total energy consumption (TEC) existed when changing the bypass factor of the HPDU under certain ambient temperatures. Compared to the CHPD, the coefficient of performance (COP) of the HPDU increased by up to 39.56%, presenting a significant energy benefit for the application of HPDU.

This paper presents the development and utilisation of a heat regeneration approach to enhancing the performance and reducing the life-cycle cost of supercooled water ice slurry generation systems. Two supercooled water systems with direct and indirect ice slurry generation were enhanced by the heat regeneration approach to avoid excessive cold loss and increase the supercooling degree, thereby improving system efficiency while reducing operational costs. Their respective performance and life-cycle costs were experimentally evaluated and compared to the ones without heat regeneration enhancement under different working conditions, as well as to a conventional scraped surface ice slurry generator used as a benchmark. It was found from the comparative investigation that the heat regeneration approach can effectively reduce the water temperature at the inlet of the supercooler, allowing a significant amount of cold loss to be saved for ice slurry generation. The effective utilisation rate of cold can be effectively improved by over 15% when using the heat regeneration approach, and the unit ice mass power consumption can be reduced by 12–20%. Due to the attractive energy-saving potential, the operational cost-effectiveness of the enhanced systems contributed to cut-down of life-cycle cost. It was found that the life-cycle costs of the enhanced direct and indirect ice slurry generation systems were 62.0% and 74.7% lower than that of the conventional scraped surface ice slurry generator, respectively.

Materials for the efficient use of green, renewable and clean solar energy have aroused general interest for quite a long time. In this work, simple and inexpensive double-layered structural photothermal conversion materials were prepared for the photothermal evaporation process. Partially reduced graphene oxide (prGO) was prepared by a controlled hydrothermal reduction of graphene oxide and was employed in the construction of double-layered photothermal conversion materials. The chemical features of prGO, the light absorbance and the properties of the double-layered materials were characterized, and the hydrophilicity, photothermal properties and water evaporation performance of the double-layered materials were analyzed. The results showed that prGO was easily obtained from GO through the hydrothermal partial reduction process. After the hydrothermal treatment, the surface topography of prGO was found to be rough with openings and facilitated light scattering and absorption. The C/O atomic ratio in the obtained prGO increased compared with that of GO, but the highly hydrophilic functional groups were still present in the prGO. The hydrophilicity of the prGO layer enhanced the wettability of the interface and facilitated the escape of vapor from the thin water film. The fabricated prGO had strong light absorption in the spectral range from 280 nm to 2500 nm, and the absorbance could be as high as 95%. Under a simulated solar illumination of 1 kW · m^–2, the evaporation efficiency values of EPE-prGO, Sponge-prGO and Wood-prGO were as high as 81%, 83% and 91%, respectively, and the temperature on the surfaces of the prGO-coated materials rose rapidly and reached the maximum value after approximately 6 minutes. The water evaporation of these materials was found to respond immediately to light irradiation. The energy efficiency and the rate of evaporation were greatly improved by using the materials produced in this work.

In view of the problems of high energy consumption and heavy pollution in the drying process of large-scale multi-stage tower coal-fired corn in Northeast China, combined with the high cold characteristics of the regions, a multi-stage series dehumidification heat pump tower corn drying system was proposed, and a demonstration application project was established. The performance and life-cycle costs of the system were experimentally evaluated and compared to a traditional coal-fired corn drying tower. The results show that the system can achieve a supply air temperature above 68 °C under the ambient temperature of −20 °C. The total energy consumption of the system per hour is 595.5 kWh, and the specific moisture extraction rate reaches 3.39 kg/kWh. Moreover, the coefficient of performance of heat pump units reaches 3.0 − 6.3. Due to the attractive energy-saving potential, the operational cost-effectiveness of the multi-stage series dehumidification heat pump tower corn drying system can contribute to cut-down of life-cycle cost. It has been found that the life-cycle cost of the multi-stage series dehumidification heat pump tower corn drying system is 40.5% lower than that of the traditional coal-fired corn drying tower.