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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Solar light systems, and related components and methods

A solar light system may include two stages of optical concentration with intermediate removal of infrared radiation between the optical concentration stages. A second stage of optical concentration may prepare multiple concentrating beams of processed solar radiation with visible light with each such concentrating beam directed to a different corresponding light conduit for transmission to an interior space for interior lighting. System modularization may provide flexibility to accommodate a variety of interior lighting applications.

14 SOLAR ENERGY↗
DOE OSTI2024

Solar Street Lighting: Highland Park Pathways to Power [Slides]

Through the Communities LEAP (Local Energy Action Program) Pilot, the National Renewable Energy Laboratory (NREL) engaged the Highland Park Stakeholder Coalition to scope four technical assistance work areas to address their energy needs and goals. This slide deck addresses the highlighted tasks under work area "A" related to the city's streetlights. Due to economic collapse, the City of Highland Park negotiated repossession of it's neighborhood streetlights to help pay its debt to its power provider, DTE. Without street lighting on residential streets, public safety was at risk. Local community-based-organization, Soulardarity, began installing off-grid solar street lights to improve visibility for vehicles and pedestrians in Highland Parks neighborhoods. Residents and leaders of the community who served on the Communities LEAP Coalition requested NREL review a financial model Soulardarity proposed to operate a city-wide solar streetlighting program on the City's behalf. The coalition also requested NREL identify examples of similar implemented city-wide solar street lighting programs.

14 SOLAR ENERGY↗
DOE OSTI2026

Prototype Development, Testing, and Modeling for a Solar Light-Trapping Planar-Cavity Particle Receiver

Many applications for concentrating solar thermal power (CSP) technologies of high efficiency power cycles or thermochemical processes require higher operating temperatures and alternative heat transfer media. Inert solid particles for next-generation CSP and reactive gas and/or solid media for solar thermochemical processes are common options; however, these have significantly lower heat transfer capabilities than thermal oil, molten salt, or molten metal media. Conventional solar receivers operating temperatures >700 degrees Celsius face challenges including thermal performance and thermal-mechanical issues. To overcome these limitations, we have developed a novel light-trapping, planar-cavity receiver (LTPCR) that can heat solid-phase media within an enclosed receiver while maintaining a high aperture solar flux concentration for high efficiency. This paper presents progress on design, fabrication, and testing of a 100 kWt prototype receiver to demonstrate the LTPCR operability and its commercial feasibility.

14 SOLAR ENERGY↗
DOE OSTI2026

Prototype Development, Testing, and Modeling for a Solar Light-Trapping Planar-Cavity Particle Receiver (LTPCR)

Many applications for concentrating solar thermal power (CSP) technologies of high efficiency power cycles or thermochemical processes require higher operating temperatures and alternative heat transfer media. Inert solid particles for next-generation CSP and reactive gas and/or solid media for solar thermochemical processes are common options; however, these have significantly lower heat transfer capabilities than thermal oil, molten salt, or molten metal media. Conventional solar receivers operating temperatures >700 degrees Celsius face challenges including thermal performance and thermal-mechanical issues. To overcome these limitations, we have developed a novel light-trapping, planar-cavity receiver (LTPCR) that can heat solid-phase media within an enclosed receiver while maintaining a high aperture solar flux concentration for high efficiency. This paper presents progress on design, fabrication, and testing of a 100 kWt prototype receiver to demonstrate the LTPCR operability and its commercial feasibility.

14 SOLAR ENERGY↗
DOE OSTI2025

Toward solar light-driven photochemical carbon dioxide separation

The feasibility of energy-efficient photochemically driven CO 2 release has been demonstrated in several recent reports, but the regeneration step remains much slower. Recently in Chem, Ahmad et al. reported a fully visible-light-driven CO 2 separation system capable of operating with concentrated sunlight. Here, we discuss this advance and the potential route toward large-scale fully photochemical CO 2 capture.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Vivianite oxidation is not photocatalyzed

Vivianite is a hydrous Fe2+ phosphate mineral found in anoxic environments that plays an integral role in P cycling and environmental biogeochemistry. Imbued in the vivianite literature dating as far back as 1918 is the notion that vivianite is light-sensitive and susceptible to rapid photooxidation induced entirely by solar light. However, despite an exhaustive search, to our knowledge this conventionally accepted assumption has never been directly tested, nor has the band gap ever been measured. Resolving this question of photochemical control of vivianite redox chemistry is important for performing and interpreting experiments involving vivianite reactivity with contaminants, and potentially iron and phosphate cycling in the photic zone of aquatic systems. The present study was specifically designed to add¬ress this question. Pure synthetic vivianite samples were irradiated in aqueous suspensions with a Xe lamp at conditions mimicking the solar spectrum and compared to dark controls. Particles stirred in anoxic suspensions for up to 66 days showed no detectable oxidation irrespective of light exposure, according to colorimetric Fe2+/Fe3+ assays, micro X-ray diffraction, and Raman spectroscopy. In contrast, the same experiment performed using air-equilibrated suspensions showed systematic oxidation of up to ~80% mol% Fe(II) at 66 days, but again with no detectable light exposure effect. To test for UV reactivity, further experiments on vivianite powders under air versus N2 atmosphere were performed using a Hg lamp with a longpass filter. In contrast to oxidation in air where no effect of light was detected, after 24 hrs irradiation anoxically, 0.78% Fe was oxidized compared to dark controls, and after 13 days only an additional 0.3% Fe was oxidized. The band gap of pure vivianite was measured by the Tauc method to be 3.5 eV. Contrary to previous reports, solar light has minimal impact on the oxidation of pure vivianite, insignificant in particular when compared to its relatively fast oxidation by oxygen exposure. As such, light does not need to be excluded when running typical vivianite laboratory experiments. Long-term storage of natural vivianite in museums or private collections should continue protective measures given that a possible photocatalytic role of impurities cannot yet be ruled out. Nonetheless, at all depths in natural aquatic systems it appears that the primary abiotic control on the reactivity and half-life of vivianite particles should be the dissolved oxygen concentration, not light exposure.

Vivianite, photochemistry, oxidation↗
DOE OSTI2022

Nanoporous Titanium (Oxy)nitride Films as Broadband Solar Absorbers

Broadband absorption of solar light is a key aspect in many applications that involve an efficient conversion of solar energy to heat. Titanium nitride (TiN)-based materials, in the form of periodic arrays of nanostructures or multilayers, can promote significant heat generation upon illumination thanks to their efficient light absorption and refractory character. In this work, pulsed laser deposition was chosen as a synthesis technique to shift metallic bulk-like TiN to nanoparticle-assembled hierarchical oxynitride (TiO x N y ) films by increasing the background gas deposition pressure. The nanoporous hierarchical films exhibit a tree-like morphology, a strong broadband solar absorption (~90% from the UV to the near-infrared range), and could generate temperatures of ~475 °C under moderate light concentration (17 Suns). The high heat generation achieved by treelike films is ascribed to their porous morphology, nanocrystalline structure, and oxynitride composition, which overall contribute to a superior light trapping and dissipation to heat. These properties pave the way for the implementation of such films as solar absorber structures.

14 SOLAR ENERGY↗
DOE OSTI2022

Tailored Persistent Radical‐containing Heterotrimetal‐Organic Framework for Boosting Efficiency of Visible/NIR Light‐driven Photocatalytic CO 2 Reduction

Abstract Promoting light absorption range of photocatalysts is of great significance to improve solar light‐driven photocatalytic CO 2 reduction efficiency. Herein, a new viologen‐based multicomponent heterotrimetallic metal–organic framework (MOF) [Cu 3 Th 6 ( µ 3 ‐O) 4 ( µ 3 ‐OH) 4 (cpb) 12 ][Fe III (CN) 6 ] 6 (IHEP‐14) with an unprecedented (6, 18)‐connected she ‐ d topology is presented. Upon UV irradiation, this MOF undergoes ligand and iron photoreduction, and a single‐crystal‐to‐single‐crystal transformation to generate persistent radical‐containing MOF [Cu 3 Th 6 ( µ 3 ‐O) 4 ( µ 3 ‐OH) 4 (cpb • ) 12 ][Fe II (CN) 6 ] 6 (IHEP‐15). This radical‐containing MOF shows excellent stability without fading after at least 2 months in air. Besides extending the photoabsorption to a wider wavelength range covering from 200 to 2,500 nm, the generation of persistent radical in IHEP‐15 also largely enhances its CO 2 adsorption capacity by a factor of three due to the strong affinity between π orbital of the radical and the π system of CO 2 . These attributes endow IHEP‐15 with excellent visible/NIR light‐driven CO 2 photoreduction activity, with CO production rates under visible and NIR irradiation of 570.3 and 209.3 µmol h −1 g −1 , respectively. Notably, the latter is a record high for NIR‐induced CO production among all MOFs reported so far.

Hu, Kong‐Qiu↗
DOE OSTI2020

Experimental demonstration and performance evaluation of a complex fenestration system for daylighting and thermal harvesting

Two significant design strategies for mitigating building energy consumption are daylight redirection and solar energy harvesting. Effective daylighting implementation enhances the amount of useful natural light within a space and offsets the need for electric lighting. Solar energy harvesting systems can mitigate energy costs from mechanical systems by managing incoming thermal loads or capturing solar energy that can be used to supplement thermal systems in the building. While there are many available façade-based technologies that can perform daylighting or solar thermal energy harvesting, there remains a limitation in available systems that can perform both of them simultaneously. This paper, describes the design and experimental demonstration of a Liquid Filled Prismatic Louver (LFPL) system, which combines both energy-saving strategies. The LFPL system was installed in a south-facing room in New York City and evaluated for indoor daylight penetration and potential for thermal energy harvesting. Daylight redirection is achieved through the prismatic louver geometry and proper orientation, whereas thermal energy harvesting is achieved through IR absorption from the liquid (e.g., water) within the prisms. Daylighting performance was evaluated by illuminance measurements at key locations within the space, whereas thermal harvesting performance was evaluated through temperature measurements and thermal imaging analysis. We show that the LFPL system, with all prismatic elements oriented at the same angle, achieve a 2-fold and 8-fold enhancement in daylight redirection to the ceiling, for prism orientations of 10° and 20°, respectively. We also demonstrate the system’s capability to adjust to specific lighting needs, within the space, through the dynamic individual orientation of prismatic elements; thus, achieving a concentrated ceiling illuminance enhancement of ~100 times and ~200 times at 2.5 and 4.3 m away from the window sill, providing workplane illuminance enhancement of 6 and 2 times more than in the case of the control room with regular windows. Furthermore, we illustrate a reduction of potential heating loads at locations close to the window from the combination of infrared absorption in the water volume and the redirection of the incoming solar radiation, leading to a reduction of the workplane temperature by an average of 7–10 °C.

14 SOLAR ENERGY↗
DOE OSTI2020

Mechanisms of mechanochemical synthesis of cesium lead halides: pathways toward stabilization of α-CsPbI 3

Cesium lead iodide with cubic perovskite structure (α-CsPbI 3 ) is gaining significant interest in photovoltaic applications due to its excellent absorbance of the visible solar light and other attractive optoelectronic properties. However, the synthesis of stable α-CsPbI 3 poses a significant challenge. Mechanochemical synthesis is emerging as a suitable method for the preparation of cesium lead halides. This work investigates the ball milling-induced synthesis of cesium lead halides perovskite phase using halide mixing or doping approaches. The synthesis in the CsI + PbI 2 , CsBr + PbBr 2 , CsBr + PbI 2 , and CsI + PbI 2 + NdI 3 mixtures and halide exchange reactions in the CsPbBr 3 + 3KI and CsBr + PbBr 2 + 3KI systems are investigated to elucidate the mechanism of this process. Then, CsPb(I 1–x Br x ) 3 and CsPb( 1–y )Nd y I 3 materials with different x and y ratios are prepared, and their stability is probed in the air using light absorption spectroscopy. These results suggest that Nd doping is more efficient in the stabilization of the perovskite structure than partial replacement of iodine with bromine. Microstructure observations reveal the existence of two different product formation mechanisms depending on the mechanical properties of reactants. The results reveal that the milling temperature has a significant impact on the reaction kinetics. Here, the produced particles nucleate and grow at the reactant interface and retard the synthesis reaction by creating a diffusion barrier. Extended milling reduces the product particle size and creates fresh contact between reactants, thus facilitating reaction completion.

36 MATERIALS SCIENCE↗
DOE OSTI2023

A series of four-coordinate heteroleptic copper(I) complexes with diimine and β-diketiminate ligands

In this paper, a series of heteroleptic bis-chelate copper(I) complexes of the general formula Cu(N^N)(NacNac R ), where N^N is the diimine ligand and NacNac R is the β-diketiminate ligand are introduced. The complexes are easily prepared by reacting NacNac ligands with CuO t Bu in the presence of diimine ligands. The molecular structures of all complexes are characterized by NMR spectroscopy and X-ray crystallography. The studies of cyclic voltammetry and UV–vis absorption spectra show that the HOMO and the LUMO energy level can be tailored by changing the substitution pattern of each ligand. The oxidation potential is dependent on the NacNac ligand, and the reduction potential shows the dependence on the diimine ligand. In conclusion, tunable redox potentials and a wide range of visible absorption can make these copper(I) complexes promising candidates for applications in solar light harvesting.

14 SOLAR ENERGY↗
DOE OSTI2024

Electronic Structure of Excitons in Hematite Fe 2 O 3

We present a computational study of the electronic structure of excitons in hematite Fe 2 O 3 using density functional theory (DFT) and time-dependent DFT theory. Excitons resulting from solar light absorption are precursors to photogenerated charge carriers, which are the active species in solar-to-fuel redox conversions. Upon vertical excitation, the lowest energy exciton is found to have a multideterminantal wave function, describing an electron excited from O 2p states to Fe 3d states of the nearest basal plane, possibly supporting a recent XUV-derived exciton structure with a radius of a single Fe–O bond. Subsequently, the exciton self-traps into stable electron–hole pair structures whose wave functions are well-approximated by single excitations conveniently labeled “HOMO–LUMO”. Self-trapping yields electron–hole pair structures whereby the electron state (electron polaron-like) is separated from the hole state (hole polaron-like) by 3, 5, 7, 9, ... basal planes in structures referred to as Exc-3, Exc-5, Exc-7, Exc-9, ... The natural transition orbitals (electron–hole states) exhibit a strong “localized” character. The hole state is best described as a (FeO 6 ) + octahedral moiety carrying ~0.65 h + charge, and overall ~70% of the hole is assigned to O 2p atomic states, mostly on the four (4) equatorial O atoms of the moiety. The electron state is best described as a (FeFe) – moiety carrying ~0.80 e – charge in Fe 3d atomic states. The lattice distortions around the hole site exhibit Fe–O bond shortening due to the removal of electron density from an orbital state with O–Fe–O antibonding character. The electron site shows Fe–Fe distance shortening due to excess electron density added to an orbital state with in-phase Fe–Fe interactions. Furthermore, these excitonic structures with increasing electron–hole separation can be viewed as the onset of exciton separation into isolated electrons and hole polarons.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Electrical edge effect induced photocurrent overestimation in low-light organic photovoltaics

In many literatures, the short-circuit current (J SC ) of indoor organic photovoltaics is overestimated, leading to severely wrong device performance evaluation and analysis. In this work, based on the equivalent circuit model, we demonstrate that electrical edge effect is sensitive to both transverse surface resistance and light intensity. At low light intensity, the electrical edge effect could lead to J SC being significantly overestimated, i.e., by 100% and even more. We show that for a PM6:Y6 device capped with a MoOX layer, when measured under 0.01 sun, the usually overlooked interface doping mechanism would lead to J SC and PCE overestimation by 51% and 15%, respectively. Besides, we show that the magnitude of J SC overestimation drastically increases with high photoactive-layer surface roughness. This work emphasized the significant electrical edge effect on J SC evaluations for low-light solar cells and is conducive to understanding the intrinsic mechanism of edge effect, promoting a healthier development of organic photovoltaics.

14 SOLAR ENERGY↗
DOE OSTI2022

Rapid scalable fabrication of roll-to-roll slot-die coated flexible perovskite solar cells using intense pulse light annealing

Perovskite solar cells have achieved high efficiencies at the lab scale using batch processes that often may not be scalable. Processes that can be integrated into a continuous manufacturing platform, such as roll-to-roll, where several processes can be carried out sequentially are necessary to develop a new cost-competitive solar technology. In this work, intense pulsed light thermal post-processing is coupled with scalable slot-die coating and air knife evaporation in a high-speed roll-to-roll process of up to 2 m min –1 . The optimization of IPL energy parameters, web speeds, solution flow rates, and concentration of precursor inks yielded a champion power conversion efficiency of 11.24% for a 1 cm 2 roll-to-roll coated device. The overall processing time for a single layer in this process is reduced from minutes to seconds and the overall footprint of the manufacturing process is decreased. Furthermore, this demonstrates the promising capabilities for intensed pulsed light to reduce manufacturing costs and paves a roadmap for scalable and efficient PSCs on a roll-to-roll platform.

14 SOLAR ENERGY↗