Energy storage technology can balance the mismatch between energy supply and demand, which is an important link between the use of renewable energy and waste heat. Absorption thermal energy storage has attracted considerable attention in recent years owing to its high energy-storage density, high energy-storage efficiency, low charging temperature, low heat loss, and flexible output. A state-of-the-art review of advanced cycles, working pairs, and experimental prototypes was conducted. The development of advanced cycles has further improved the energy storage density and efficiency and lowered the charging temperature. The screening of novel working pairs solved the crystallization problem of conventional salt solutions, increased the options of working fluids for different scenarios, and reduced costs. The successful development and operation of experimental prototypes have confirmed the excellent performance of absorption thermal energy storage and paved the way for its promotion and application. In conclusion, the challenges and opportunities of absorption thermal energy storage for the future are summarized, and the development direction is discussed.

The increasing demand for computing power in data centers has led to a surge in energy consumption. Almost all the electricity consumed is converted into waste heat, which promotes the development of waste heat recovery technologies in data centers. Sorption-based technologies, driven by thermal energy, can reduce electricity consumption while enabling the multifunctional utilization of waste heat. However, most studies on sorption-based technologies have focused on building and industrial waste heat scenarios. This study reviews and summarizes a novel sorption-based technology framework tailored for data centers, covering five key areas: device-level thermal management, cooling driven by waste heat, energy storage, power generation from waste heat, and atmospheric water harvesting. A key quantitative finding of the study is a temperature drop of up to 21 ℃ (25 kW/m²) using sorption-based salt-water heat sinks. Furthermore, the study compares the performance differences among single-effect, double-effect, and pressurized sorption cooling systems driven by 40-60 ℃ heat sources, with a coefficient of performance (COP) above 0.7. The role of sorption-based thermal energy storage in peak shaving, valley filling, and renewable energy integration is reviewed. The power generation efficiency of sorption-based power systems under low-grade heat sources is examined, and the potential of atmospheric water harvesting from waste heat and cooling tower exhaust air recovery in relation to water conservation is analyzed, which can reduce the water usage effectiveness (WUE) by approximately 75%. In addition, key technical challenges, including material stability, heat and mass transfer enhancement, system control strategies, and engineering integration, are summarized. Overall, this study provides a new technical pathway for the diversified utilization of sorption-based technologies in data centers with significant implications for achieving energy and water conservation.

Domestic hot water (DHW) systems contribute significantly to the building sector’s energy consumption and carbon emissions, making innovative optimization methods crucial for enhancing DHW energy efficiency. Existing DHW system optimizations focus on design parameters and operation modes, but their applicability is limited to specific systems and configurations, overlooking more efficient alternatives. To overcome this problem, combining visualized graphic and algebraic techniques, this study introduces a novel bi-level expanded Process Graph optimization method (BEPGOM) to optimize a DHW system with diverse component-candidates. BEPGOM effectively identifies nontrivial configurations, substantially improving economic and environmental benefits, and enhances solvability with a 98% reduction in solution space. The optimal configuration, consisting of solar heating, PCM tank, and natural gas water heater, reduces the expenditures by 18% and equivalent CO₂ emission by 34% compared to the existing base case, greatly exceeding the traditional optimization method. Its adaptability, efficiency, and accessibility make BEPGOM a valuable tool in advancing energy system design and promoting carbon neutrality in the building sector.