Concentrating solar power (CSP) is a reliable and wellknown form of solar power. Nine solar trough plants producing more than 400 megawatts (MW) of electricity have been operating reliably in the California Mojave Desert since the 1980s. With a renewed sense of urgency to commercialize renewable energy sources, the U.S. Department of Energy (DOE) is ramping up its CSP research, development, and deployment efforts. These efforts, which are leveraging both industry partners and the national laboratories, are directed toward the development of parabolic trough, dish/engine, and power tower CSP systems.

Recent progress in passive radiative cooling technologies has substantially improved cooling performance under direct sunlight. Yet, experimental demonstrations of daytime radiative cooling still severely underperform in comparison with the theoretical potential due to considerable solar absorption and poor thermal insulation at the emitter. In this work, we developed polyethylene aerogel (PEA)—a solar-reflecting (92.2% solar weighted reflectance at 6 mm thick), infrared-transparent (79.9% transmittance between 8 and 13 μm at 6 mm thick), and low-thermal-conductivity (kPEA = 28 mW/mK) material that can be integrated with existing emitters to address these challenges. Using an experimental setup that includes the custom-fabricated PEA, we demonstrate a daytime ambient temperature cooling power of 96 W/m2 and passive cooling up to 13°C below ambient temperature around solar noon. This work could greatly improve the performance of existing passive radiative coolers for air conditioning and portable refrigeration applications.

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Solar desalination holds significant promise for the water-energy nexus. Recent advances in passive solar desalination using thermal localization show great potential for high-efficiency freshwater production, which is particularly beneficial for...

Demonstrations of passive daytime radiative cooling have primarily relied on complex and costly spectrally selective nanophotonic structures with high emissivity in the transparent atmospheric spectral window and high reflectivity in the solar spectrum. Here, we show a directional approach to passive radiative cooling that exploits the angular confinement of solar irradiation in the sky to achieve sub-ambient cooling during the day regardless of the emitter properties in the solar spectrum. We experimentally demonstrate this approach using a setup comprising a polished aluminum disk that reflects direct solar irradiation and a white infrared-transparent polyethylene convection cover that minimizes diffuse solar irradiation. Measurements performed around solar noon show a minimum temperature of 6 °C below ambient temperature and maximum cooling power of 45 W m–2. Our passive cooling approach, realized using commonly available low-cost materials, could improve the performance of existing cooling systems and enable next-generation thermal management and refrigeration solutions.

Heat at intermediate temperatures (120−220 °C) is in significant demand in both industrial and domestic sectors for applications such as water and space heating, steam generation, sterilization, and other industrial processes. Harnessing heat from solar energy at these temperatures, however, requires costly optical and mechanical components to concentrate the dilute solar flux and suppress heat losses. Thus, achieving high temperatures under unconcentrated sunlight remains a technological challenge as well as an opportunity for utilizing solar thermal energy. In this work, we demonstrate a solar receiver capable of reaching over 265 °C under ambient conditions without optical concentration. The high temperatures are achieved by leveraging an artificial greenhouse effect within an optimized monolithic silica aerogel to reduce heat losses while maintaining high solar transparency. This study demonstrates a viable path to promote cost-effective solar thermal energy at intermediate temperatures.

Atomically thin two-dimensional (2D) materials have shown great potential for applications in nanoscale electronic and optical devices. A fundamental property of these 2D flakes that needs to be well characterized is the thermal expansion coefficient (TEC), which is instrumental to the dry transfer process and thermal management of 2D material-based devices. Yet, most of current studies of 2D materials' TEC extensively rely on simulations due to the difficulty of performing experimental measurements on an atomically thin, micron-sized, and optically transparent 2D flake. In this work, we present a three-substrate approach to characterize the TEC of monolayer molybdenum disulfide (MoS 2 ) using micro-Raman spectroscopy. The temperature dependence of the Raman peak shift was characterized with three different substrate conditions, from which the in-plane TEC of monolayer MoS 2 was extracted based on lattice symmetries. Independently from two different phonon modes of MoS 2 , we measured the in-plane TECs as (7.6±0.9)×10 -6 1/K and (7.4±0.5)×10 -6 1/K, respectively, which are in good agreement with previously reported values based on first principle calculations. Our work is not only useful for thermal mismatch reduction during material transfer or device operation, but provides a general experimental method that does not rely on simulations to study key properties of 2D materials.

Understanding of polarization-heat interactions in pyroelectric and electrocaloric thin-film materials requires that the electrothermal response is reliably characterized. While most work, particularly in electrocalorics, has relied on indirect measurement protocols, here we report a direct technique for measuring both pyroelectric and electrocaloric effects in epitaxial ferroelectric thin films. We demonstrate an electrothermal test platform where localized high-frequency (∼ 1 kHz) periodic heating and highly-sensitive thin-film resistance thermometry allow direct measurement of pyrocurrents (< 10 pA) and electrocaloric temperature changes (< 2 mK) using the "2-omega" and an adapted "3-omega" technique, respectively. Frequency-domain, phase-sensitive detection permits extraction of pyrocurrent from the total current, which is often convoluted by thermally-stimulated currents. The wide frequency range measurements employed in this study further show the effect of secondary contributions to pyroelectricity due to the mechanical constraints of the substrate. Similarly, measurement of the electrocaloric effect on the same device in the frequency-domain (∼ 100 kHz) allows decoupling of Joule heating from the electrocaloric effect. Using one-dimensional, analytical heattransport models, the transient temperature profile of the heterostructure is characterized to extract pyroelectric and electrocaloric coefficients.