Lyu Zhou

The transition to a flexible and reliable energy infrastructure, using electro-thermal energy generation technologies such as geothermal, concentrated solar power, and nuclear, usually demands simultaneous advancement of thermal energy storage (TES) to support on-demand electricity generation and industrial applications while mitigating the inherent intermittency of renewable energy sources and power outages from direct energy generation. Among TES technologies, thermochemical energy storage (TCES) based on calcium looping emerges as a compelling high-power energy storage candidate due to its high reaction enthalpy, compatibility with elevated operating temperatures, and abundance of low-cost materials. However, the long-term durability of calcium-based sorbents for TCES is hindered by surface sintering and particle aggregation, leading to performance degradation over repeated thermal cycles. This study explores a moisture hydration-based strategy to regenerate a degraded calcium sorbent and mitigate performance degradation for long duration TCES. The addition of moisture transforms calcium oxide into calcium hydroxide and produces intercalation water layers, associated with a regenerated surface area and reduced calcium oxide crystallite size. Both these effects are beneficial in restoring the sorbents’ reactivity for carbonization. Additionally, an optimized hydration-assisted reactivation protocol balances the recovered energy storage capacity with heating penalty required for moisture removal from hydrated samples, resulting in an enhanced energy storage capacity up to 176% compared to benchmark sorbents that undergo cycling without reactivation after 60 cycles. These results highlight the potential of hydration-assisted reactivation to enhance the long-term performance of TCES, providing an effective pathway to advancing electro-thermal storage technologies.

Improving the thermal performance of building envelopes, especially transparent envelopes, is critical to reducing the significant energy consumption associated with thermal comfort regulation as transparent envelopes are responsible for 25%-30% of residential heating and cooling energy use. Thermal energy storage (TES) utilizing the latent heat of phase change materials (PCMs) has proven effective in reducing and shifting the peak loads when integrated into building envelopes, especially opaque ones. However, the practical application of TES is often constrained by factors such as materials’ cost, shape stability, and energy density. In this work, we fabricated a transparent phase change hydrogel (PCH) with exceptional shape stability and high energy density for energy-efficient window applications by incorporating salt hydrates into poly (acrylamide-co-acrylic acid) hydrogel matrices. The excellent shape stability prevents the leakage of salt hydrates upon melting owing to the retention of salt solution by the hydrogel network. By optimizing PCH composition and salt hydrates loading, a high melting enthalpy of 133.3 J/g is demonstrated with a melting temperature of 32.8 ℃, while maintaining excellent shape stability without degradations in energy density and shifting in melting temperature after 500 thermal cycles. Furthermore, the PCH exhibits over 90% transmittance in the visible range at both melt and crystalized states, making it a promising solution for TES for practical window applications. The proposed PCH/glass window with a PCH dimension of 100 mm ×100 mm ×5 mm can shift the load to off-peak hours by 30 minutes, enhancing the power grid's resilience.

The management of the abundant eggshell biowaste produced worldwide has become a problematic issue due to the generated odor and microorganisms after direct disposal of the eggshell biowaste in landfills. Herein, we propose a new method to convert the hazardous eggshell biowaste to valuable resources for energy management applications. Eggshell-based films are fabricated by embedding eggshell powders into a polymer matrix to achieve highly efficient subambient daytime radiative cooling. Benefiting from the Mie scattering of the eggshell particles/air pores in the solar spectrum and the strong emission of the eggshell in the mid-infrared (mid-IR) range, the eggshell-based films present a high reflection of 0.96 in the solar spectrum and a high emission of 0.95 in the mid-IR range, with notable average temperature reductions of 4.1 and 11 °C below the ambient temperature during daytime and nighttime, respectively. Moreover, the eggshell-based films exhibit excellent flexibility and self-cleaning properties, which are beneficial for practical long-term outdoor applications. Our proposed design provides a new means for environmentally friendly and sustainable management of eggshell biowaste.

Nanocomposites containing nanoscale materials offer exciting opportunities to encode nanoscale features into macroscale dimensions, which produces unprecedented impact in material design and application. However, conventional methods cannot process nanocomposites with a high particle loading, as well as nanocomposites with the ability to be tailored at multiple scales. A composite architected mesoscale process strategy that brings particle loading nanoscale materials combined with multiscale features including nanoscale manipulation, mesoscale architecture, and macroscale formation to create spatially programmed nanocomposites with high particle loading and multiscale tailorability is reported. The process features a low‐shrinking (<10%) “green‐to‐brown” transformation, making a near‐geometric replica of the 3D design to produce a “brown” part with full nanomaterials to allow further matrix infill. This demonstration includes additively manufactured carbon nanocomposites containing carbon nanotubes (CNTs) and thermoset epoxy, leading to multiscale CNTs tailorability, performance improvement, and 3D complex geometry feasibility. The process can produce nanomaterial‐assembled architectures with 3D geometry and multiscale features and can incorporate a wide range of matrix materials, such as polymers, metals, and ceramics, to fabricate nanocomposites for new device structures and applications.

As a sustainable technology, radiative cooling has received considerable attention due to its potential in energy sustainability. Unlike conventional cooling techniques, radiative cooling does not consume electricity during its operation and is therefore particularly attractive in reducing the energy demand for cooling and addressing global warming by reducing carbon emissions. The general principle requires a radiative cooler to be thermally emissive to dissipate heat via thermal radiation. During the daytime, the cooler needs to minimize the solar heating effect to ensure subambient temperatures. Guided by these criteria, researchers have developed various materials with engineered optical, thermal, and mechanical features. In this review, we will first explore the fundamentals of heat transfer in radiative cooling processes. Subsequently, we will summarize the state-of-the-art progress on material synthesis and system designs. Building upon those recently developed features, we will review how this technology has been implemented in practical applications, ranging from thermal management of buildings, semiconductor cooling, personal comfort design, and atmospheric water harvesting. Finally, we will conclude this review by identifying and discussing some of the remaining challenges requiring future research and development.

Radiative cooling is an emerging cooling technology that can passively release heat to the environment. To obtain a subambient cooling effect during the daytime, chemically engineered structural materials are widely explored to simultaneously reject sunlight and preserve strong thermal emission. However, many previously reported fabrication processes involve hazardous chemicals, which can hinder a material's ability to be mass produced. In order to eliminate the hazardous chemicals used in the fabrication of previous works, this article reports a white polydimethylsiloxane (PDMS) sponge fabricated by a sustainable process using microsugar templates. By substituting the chemicals for sugar, the manufacturing procedure produces zero toxic waste and can also be endlessly recycled via methods widely used in the sugar industry. The obtained porous PDMS exhibits strong visible scattering and thermal emission, resulting in an efficient temperature reduction of 4.6 °C and cooling power of 43 W m⁻² under direct solar irradiation. In addition, due to the air‐filled voids within the PDMS sponge, its thermal conductivity remains low at 0.06 W (m K)⁻¹. This unique combination of radiative cooling and thermal insulation properties can efficiently suppress the heat exchange with the solar‐heated rooftop or the environment, representing a promising future for new energy‐efficient building envelope material.

We report a double-sided radiative cooling system with a record high local cooling power density of ~270 W/m². The configuration of the system was investigated theoretically and a superior cooling performance was demonstrated experimentally.