SEARCH · Search NASA

Results for “Power Efficiency”

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.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 271 records · Page 15

All sources NASA NTRS DOE OSTI

DOE OSTI2021

Efficient Contingency Analysis in Power Systems via Network Trigger Nodes

Modeling failure dynamics within a power system is a complex and challenging process due to multiple inter-dependencies and convoluted inter-domain relationships. Subject matter experts (SMEs) are interested in understanding these failure dynamics for reducing the impact from future disasters (i.e., losses or failures of power system components, such as transmission lines). Contingency analysis (CA) tools enable such ’what-if’ scenario analyses to evaluate the impacts on the power system. Analyzing all possible contingencies among N system components can be computationally expensive. An important step for performing CA is identifying a set of k ‘trigger’ components, which when failed initially can significantly impact the overall system by causing multiple failures. Currently SMEs focus on identifying these trigger components by running expensive simulations on all possible subsets, which quickly becomes infeasible. Hence finding a relevant set of trigger components (contingencies) rapidly to enable efficient and useful CA is crucial.In a collaboration between computer scientists and power system experts, we propose an efficient method for performing CA by exploiting network inter-dependencies in power system components. First, we construct a network with multiple electric grid infrastructure components and dependencies as connections among them. We reformulate the problem of finding a set of trigger components as a problem of identifying critical nodes in the network, which can cascade power failures through connected nodes and cause significant damage to the network. To guide the practical CA tools, we develop a network-based model with a probabilistic edge-weights setup using intricate domain rules. Then we conduct an empirical study on real power system data in the US for both regional and national levels. Firstly, we use power system datasets for the US to create a national-scale domain-driven model. Secondly, we demonstrate that network-based model outperforms the outputs from a real CA tool and show on average 25 × improved selection of contingencies, thereby showcasing practical benefits to the power experts.

Tabassum, Anika↗

DOE OSTI2021

Optimization of Mitigating System Performance Index to Improve Nuclear Power Plant Safety and Efficiency

MSPI (Mitigation System Performance Index) is one of the risk-informed, plant-specific performance indicators of NRC’s Reactor Oversight Process. MSPI is used by the regulator and nuclear industry to monitor and assess the performance of plant mitigating systems. In this project, a calculation tool has been developed by incorporating the plant operation data, Probabilistic Risk Assessment (PRA) data, and industry baseline values to automate the calculation process of MSPI and the generation of the report. This is the first stage in an effort to optimize the MSPI through advanced artificial intelligence (AI) and machine learning (ML) techniques to improve nuclear power plant safety and efficiency.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗

DOE OSTI2024

Photo-accelerated oxidation of spiro-OMeTAD for efficient carbon-based perovskite solar cells

Metal halide perovskite thin film solar cell (PSC) technology demonstrates promising power conversion efficiency and paves the way to commercialization. So far, the best device performance originates from the n-i-p structure with FTO/SnO 2 /perovskite/Spiro-OMeTAD/Au device architecture. Traditionally, to achieve high efficiency, several hours of oxidization of a Li-doped Spiro-OMeTAD hole transport layer (HTL) is necessary, which hinders the application of Spiro-OMeTAD for rapid large-scale manufacturing. In particular, the oxidization process significantly relies on ambient conditions, including oxygen and moisture levels. In this work, we report a fast technique to accomplish rapid oxidation in several mins of Spiro-OMeTAD HTL in perovskite solar cells by illuminating in visible light with one Sunlight intensity (100 mW cm −2 ). Compared to the traditional approach, our photo-accelerated oxidization of Spiro-OMeTAD approach can deliver a high-power conversion efficiency. We employ this photo-accelerated oxidization for the planar carbon-based perovskite solar cell and achieve a champion device efficiency of 17.47%. This strategy overcomes the barriers for a simple and rapid means toward mass manufacturing and industrial applications by utilizing Spiro-OMeTAD as the HTL for the perovskite solar module.

14 SOLAR ENERGY↗

DOE OSTI2024

Directly Fused Porphyrin‐Tetracyanopentacenequinone Conjugates: Role of the Cross‐Conjugated, Powerful Electron Acceptor in Promoting Highly Efficient Charge Separation

Tetracyanopentacenequinone, a powerful electron acceptor, is fused directly to the porphyrin π-system to create a new class of donor-acceptor conjugates. Owing to the direct fusion and electron-deficient property of tetracyanopentacenequinone, strong intramolecular charge transfer both in the ground and excited states was witnessed. As a control, porphyrin fused with pentacenequinone was also investigated. Upon complete spectral and electrochemical characterization, the excited state properties were initially probed by time-dependent DFT studies, and the occurrence of electron transfer from different excited states was established. Free-energy calculations revealed higher exothermic electron transfer (>600 mV) than the control pentacenequinone-porphyrin systems. Pump-probe studies covering broad spatial and temporal regions revealed efficient excited state charge separation. This was unlike the control pentacenequinone-porphyrin system, where slow charge separation was witnessed only in the case of the zinc derivatives but not the free-base ones, followed by the populating of the triplet excited state. The lifetimes of the charge-separated states ranged between 30–500 ps depending on the solvent and metal ion in the porphyrin cavity. Nanosecond transient absorption studies established the charge recombination path to populate the triplet state of porphyrin or directly to the ground state as a function of solvent polarity and the nature of the conjugate. Furthermore, the significance of cross-conjugated tetracyanopentacenequinone fused directly to the porphyrin π system in promoting highly exothermic and efficient charge separation, irrespective of its cross conjugation, is borne out from this study.

Cross conjugation↗

DOE OSTI2020

Beyond Limber: efficient computation of angular power spectra for galaxy clustering and weak lensing

Angular two-point statistics of large-scale structure observables are important cosmological probes. To reach the high accuracy required by the statistical precision of future surveys, some of these statistics may need to be computed without the commonly employed Limber approximation; the exact computation however requires integration over Bessel functions, and a brute-force evaluation is slow to converge. Here, we present a new method based on our generalized FFTLog algorithm for the efficient computation of angular power spectra beyond the Limber approximation. The new method significantly simplifies the calculation and improves the numerical speed and stability. It is easily extended to handle integrals involving derivatives of Bessel functions, making it equally applicable to numerically more challenging cases such as contributions from redshift-space distortions and Doppler effects. We implement our method for galaxy clustering and galaxy-galaxy lensing power spectra. We find that using the Limber approximation for galaxy clustering in future analyses like LSST Year 1 and DES Year 6 may cause significant biases in cosmological parameters, indicating that going beyond the Limber approximation is necessary for these analyses.

weak gravitational lensing↗

DOE OSTI2023

Triply-resonant sum frequency conversion with gallium phosphide ring resonators

We demonstrate quasi-phase matched, triply-resonant sum frequency conversion in 10.6-µm-diameter integrated gallium phosphide ring resonators. A small-signal, waveguide-to-waveguide power conversion efficiency of 8 ± 1.1%/mW; is measured for conversion from telecom (1536 nm) and near infrared (1117 nm) to visible (647 nm) wavelengths with an absolute power conversion efficiency of 6.3 ± 0.6%; measured at saturation pump power. For the complementary difference frequency generation process, a single photon conversion efficiency of 7.2%/mW from visible to telecom is projected for resonators with optimized coupling. Efficient conversion from visible to telecom will facilitate long-distance transmission of spin-entangled photons from solid-state emitters such as the diamond NV center, allowing long-distance entanglement for quantum networks.

42 ENGINEERING↗

DOE OSTI2022

Intermediate-phase engineering via dimethylammonium cation additive for stable perovskite solar cells

Achieving the long-term stability of perovskite solar cells is arguably the most important challenge required to enable widespread commercialization. Understanding the perovskite crystallization process and its direct impact on device stability is critical to achieving this goal. The commonly employed dimethyl-formamide/dimethyl-sulfoxide solvent preparation method results in a poor crystal quality and microstructure of the polycrystalline perovskite films. In this work, we introduce a high-temperature dimethyl-sulfoxide-free processing method that utilizes dimethylammonium chloride as an additive to control the perovskite intermediate precursor phases. By controlling the crystallization sequence, we tune the grain size, texturing, orientation (corner-up versus face-up) and crystallinity of the formamidinium (FA)/caesium (FA) y Cs 1-y Pb(I x Br 1-x )3 perovskite system. A population of encapsulated devices showed improved operational stability, with a median T80 lifetime (the time over which the device power conversion efficiency decreases to 80% of its initial value) for the steady-state power conversion efficiency of 1,190 hours, and a champion device showed a T80 of 1,410 hours, under simulated sunlight at 65 degrees C in air, under open-circuit conditions. In conclusion, this work highlights the importance of material quality in achieving the long-term operational stability of perovskite optoelectronic devices.

14 SOLAR ENERGY↗

DOE OSTI2023

Conversion efficiency improvement of ELO GaAs solar cell, deposited on water soluble sacrificial buffer

Here, we demonstrate the improvement of power conversion efficiency of an epitaxially-lifted-off single junction GaAs solar cell deposited on a water-soluble sacrificial buffer architecture by introducing an additional germanium (Ge) interlayer between GaAs and the fluoride buffer. The epitaxial lift-off (ELO) technique has been extensively used to separate III-V device layers from their single crystal GaAs substrates. However, conventional ELO requires the use of concentrated hydrofluoric acid (HF) for extended times to etch out the sacrificial layer, subsequently degrading the surface roughness of the parent wafer. As a result, the wafer has to undergo expensive and intensive chemical mechanical polishing (CMP) processes, costing about 25% of a pristine 6-inch GaAs substrate. In our previous work, we demonstrated a method to eliminating the need for CMP post-processing by using water-assisted ELO (H 2 O-ELO). A water-soluble, 3-layer buffer architecture was developed using alkaline earth compounds. However, devices suffered low performance due to a high defect density in the GaAs active layers. A Ge interlayer was introduced to provide a more favorable surface energy for GaAs growth, which leads to an improvement of GaAs crystal quality. The Ge deposition conditions were optimized to achieve a high-quality Ge layer on triple-layer fluoride buffer. Single junction GaAs devices fabricated on Ge/(Ca,Sr)F 2 /BaF 2 /(Ca,Sr)F 2 showed improvement of solar cell performance parameters featuring increases in V oc by 23.7%, and fill factor (F.F.) by 4.9%, which results in an overall improvement of power conversion efficiency from 10.3% to 12.69%.

14 SOLAR ENERGY↗

DOE OSTI2022

Benzimidazole Based Hole‐Transporting Materials for High‐performance Inverted Perovskite Solar Cells

Abstract Interfaces play a decisive role in perovskite solar cells’ power conversion efficiency and their long‐term durability. Small‐molecule hole‐transporting materials (HTMs) have grabbed enormous attention due to their structural flexibility, material properties, and stabilities, allowing for improved operational durability in perovskite photovoltaics. This study synthesizes and investigates a new class of benzimidazole‐based small molecules, named YJS001 and YJS003 , serving as the HTMs to enable high‐efficiency mixed‐cation mixed‐halide perovskite solar cells. The benzimidazole‐based materials are dopant‐free HTMs composed of donor and acceptor building blocks that are designed to engineer the energy level alignment near the HTM/perovskite interface. Mixed‐cation mixed‐halide perovskites can be grown uniformly on both HTMs with large crystalline grains. It is discovered that the donor‐rich YJS003 ‐based solar cell exhibits a high open‐circuit voltage of 1.09 V with a champion power conversion efficiency of over 20%. Power‐dependent current–voltage characteristics of the solar cells are analyzed, from which the high performance of YJS003's excellent hole mobility and well‐aligned energy level is attributed. This work introduces a new class of benzimidazole‐based small molecules as HTMs, that paves the path for dopant free interface material development for commercialization of perovskite solar cells.

14 SOLAR ENERGY↗

DOE OSTI2020

Unraveling the influence of non-fullerene acceptor molecular packing on photovoltaic performance of organic solar cells

In non-fullerene organic solar cells, the long-range structure ordering induced by end-group π–π stacking of fused-ring non-fullerene acceptors is considered as the critical factor in realizing efficient charge transport and high power conversion efficiency. Here, we demonstrate that side-chain engineering of non-fullerene acceptors could drive the fused-ring backbone assembly from a π–π stacking mode to an intermixed packing mode, and to a non-stacking mode to refine its solid-state properties. Different from the above-mentioned understanding, we find that close atom contacts in a non-stacking mode can form efficient charge transport pathway through close side atom interactions. The intermixed solid-state packing motif in active layers could enable organic solar cells with superior efficiency and reduced non-radiative recombination loss compared with devices based on molecules with the classic end-group π–π stacking mode. Our observations open a new avenue in material design that endows better photovoltaic performance.

59 BASIC BIOLOGICAL SCIENCES↗

DOE OSTI2022

Improving the Thermomechanical Stability of High Efficiency Perovskite Solar Cells via Polymeric Nanofiber Reinforcement

We show that the mechanical stability of perovskite thin films can be increased by an order of magnitude by nanocompositing with polymeric nanofibers using a scalable method. We discuss the increase in fracture resistance energy, Gc, in the nanocomposite samples with respect to nanofiber orientation. We demonstrate this platform with commodity polymeric nanofibers including nylon-6,6 and polyvinyl alcohol. The fiber network reduces the mechanical fragility of the PSCs by increasing their fracture energy several-fold, while maintaining comparable morphology, chemical composition, and device efficiencies to pristine perovskite. Improved power conversion efficiency stability of the nanocomposites under accelerated aging conditions is demonstrated. This platform is a promising advance toward the commercial viability of PSCs.

Samoylov, Anton↗

DOE OSTI2026

McGrath Community Energy Planning

The City of McGrath, a remote Alaskan community reliant on diesel fuel, developed a Community Energy Plan through the Energy Technologies Innovation Partnership Project (ETIPP) to address high energy costs, infrastructure vulnerabilities, and long-term sustainability. Guided by community-led priorities and technical assistance from partners including NREL, REAP, and ANTHC, the plan identifies eight focus areas: distribution system upgrades, solar and battery integration, river energy potential, emergency backup power, housing efficiency, water system losses, independent power producer models, and targeted funding strategies. The plan combines local knowledge with technical analysis to chart a path toward a more resilient, affordable, and sustainable energy future for McGrath.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

DOE OSTI2025

Large eddy simulation of wind farm performance in horizontally and vertically staggered layouts

This numerical investigation employs Large Eddy Simulation (LES) coupled with Actuator Disk Model (ADM) to evaluate wind farm layout optimization strategies. The study presents a systematic analysis of aligned, horizontal staggering, vertical staggering, and mixed (combination of horizontal and vertical) staggering configurations, aiming to establish optimal design parameters for enhanced power production. The investigation examines key performance metrics including mean velocity distributions, turbulence intensity characteristics, and power generation efficiency. Results demonstrate better performance of both horizontal and vertical staggering patterns compared to conventional aligned configurations, with horizontal staggering exhibiting notably higher power output than vertical arrangements. Our findings also suggest that mixed configurations, incorporating both horizontal and vertical staggering, can offer optimal performance characteristics. As a result, this research advances the understanding of wake interactions in complex wind farm layouts and provides design guidelines for maximizing wind farm power generation efficiency through strategic turbine positioning.

17 WIND ENERGY↗

DOE OSTI2025

Novel artificial neural network model for instantaneous power losses and operational efficiency mapping of MW-scale vanadium redox flow battery for improved technoeconomic analysis

A novel data-driven, machine-learning-based method for modeling the instantaneous power losses of a distribution-sited 2 MW/8MWh vanadium redox flow battery (VRFB), a grid-scale electrochemical storage technology, is introduced and compared against benchmark empirical modeling approaches, including symmetric and asymmetric models, as well as a recent convex hull modeling approach. The novel loss modeling method introduces several advantages over the benchmark models and over simplistic efficiency estimates, the most significant of which is that the model can accurately reflect the stepwise and non-linear parasitic losses associated with the duty cycles of mechanical auxiliary systems like pump motor drives and blower fans. Residuals of the models are compared; the proposed data driven model features significantly improved accuracy over the benchmark models. The model's coefficient of determination is also improved relative to that of the benchmark models. Furthermore, a novel method for visualization of operational efficiency of the grid-scale storage technology is introduced. To demonstrate the benefits of the novel data-driven method for modeling the VRFB, the benchmark models and the proposed models are embedded into an Open DSS distribution network model to study two applications of the grid-scale electrical storage system: load leveling for grid support and energy arbitrage. This article demonstrates that the accuracy of the instantaneous power loss model significantly impacts the understanding of the state of charge of the VRFB. In turn, the accuracy of the efficiency modeling of the VRFB impacts the understanding of the potential economic value and technical benefits to the distribution network operators. In conclusion, the presented power loss modeling approach is, therefore, highly relevant for utility-stakeholders, battery asset owners, system engineers, system designers, and financial planners interested in evaluating or optimizing the operation of grid-scale VRFBs.

24 POWER TRANSMISSION AND DISTRIBUTION↗

DOE OSTI2020

Tin–Lead Alloying for Efficient and Stable All-Inorganic Perovskite Solar Cells

Cesium containing all-inorganic perovskites have received considerable interest in photovoltaics research because of their potential for improved stability compared to their organic-inorganic hybrid counterparts. However, the inorganic perovskites studied thus far still suffer from lower power conversion efficiency and long-term instability, due to an unfavorable bandgap and either phase instability or air-sensitivity. Herein, A strategy to mitigate these concerns is investigated by alloying tin and lead on the B site to form tin-lead alloyed low-bandgap (~1.34 eV) inorganic CsSn 0.3 Pb 0.7 I 3 perovskites. Solar cells made using this material in an inverted full-structured architecture with a PEDOT:PSS hole transport materials (HTM) attain power conversion efficiency (PCE) up to 9.41% (stabilized PCE 7.23%). Furthermore, a simple HTM-free device without PEDOT:PSS layer is demonstrated more stable than the full-structured device and exhibits a PCE of 7.60% (stabilized PCE 7.31%) – the highest efficiency to date for an inorganic perovskite with a bandgap below 1.40 eV. This simplified device structure shows good reproducibility and stability. Finally, this work provides a possible route for fabricating low-cost, high stability devices with competitive efficiencies.

14 SOLAR ENERGY↗

DOE OSTI2022

Robust Combined Heat and Hybrid Power (CHHP) for High Electrical Efficiency Cogeneration

According to the U.S. Department of Energy Combined Heat and Power Installation Database, approximately 80 GW of electrical power is produced in the United States using combined heat and power (CHP) systems. Studies have also shown that a potential market for CHP applications is larger than the existing market. Since fuel consumption is the most significant part of the operating cost for a CHP plant, higher efficiency translates to increased power output for the same quantity of fuel.

CHHP, LHV, CHP↗

DOE OSTI2020

Design of 1500V/200kW 99.6% Efficiency Dual Active Bridge Converters Based on 1700V SiC Power MOSFET Module

High efficiency, high density and galvanically isolated power converters are attractive for medium voltage high power applications. This paper presents a 1.5kV/200kW bidirectional Dual Active Bridge (DAB) converter using a newly developed 1.7kV SiC MOSFET module. The intended application is megawatt scale solid state transformer (SST) and 1500V PV inverter application using modular architecture. One novel model to estimate the turn-off loss using snubber capacitors is proposed and experimentally verified. An optimized PCB-based busbar design is introduced to reduce the voltage overshoot across the SiC device, making the design suitable for 1.5kVdc applications. The mechanism of how the optimized PCB-based busbar can reduce the voltage overshoot is quantitatively interpreted and experimentally verified. The DAB converter achieved an efficiency of 98.85% at 200kW and a maximum of 99.53% at 60kW. The maximum efficiency for series-resonant mode is 99.6% at 85kW and 99.3% at 200kW. The power density is 26W/inch3 (1.6MW/m3) which is much higher than traditional industry products.

Xu, Wei↗

DOE OSTI2023

Design of a Geothermal Power Plant With Solar Thermal Topping Cycle: Preprint

Geothermal power plants are a reliable source of low-carbon power generation. However, modern electricity markets comprise relatively large proportions of variable renewable energy generation that may require power plants to dispatch energy flexibly. The power output, efficiency, and dispatch flexibility of a geothermal plant can be enhanced by integrating solar thermal energy into the system, as well as possibly compensating against ambient temperature variations. Concentrating Solar Thermal (CST) can generate temperatures much higher than conventional geothermal systems. Using a solar topping cycle is one way to efficiently convert high-temperature solar heat to electricity while also adding lower-temperature heat to the geothermal power cycle, thereby increasing its power output and possibly its efficiency. A hybrid power cycle design is proposed and is simulated using SimTech IPSEpro process modelling software. The design configuration depends upon the expected temperature of the geothermal resource and the quantity of solar heat added at the design point. These design considerations are described and expected performance is calculated. The solar heat addition varies throughout the day and year, therefore off-design models are necessary to assess the impact of solar availability (and ambient temperature) on the power plant performance. Off-design models are developed and combined with hourly weather data to facilitate an evaluation of annual system performance.

concentrating solar power↗