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At least 1,477 records · Page 82
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Global Simulations Suggest Biomass Burning Aerosol Emissions From Grassland Fires Could Be Important Ice Nucleating Particles

Ice nucleating particles (INP) capable of nucleating ice crystals via immersion freezing at temperatures above approximately −35°C may strongly influence cloud glaciation, with implications for global precipitation and climate feedback. In addition to mineral dust, soil dust, and marine organics, laboratory and field measurements suggest biomass burning aerosols (BBA) can act as immersion-mode INP between around −30°C and −15°C. However, the contribution of BBA to the global INP budget remains poorly understood due to poor knowledge of which fuels yield INPs, uncertainties in global coverage of those fuels, and unknown size distributions of the INPs in the BBA. Nonetheless, with some understanding of these uncertainties from sensitivity studies, the relative importance of ice nucleation activity of BBA compared to other INP sources can be quantified. In this work, we investigate the potential global importance of BBA as INP using a global aerosol-climate model, specifically the UK Met Office Unified Model (UM). We evaluate the model using field campaign data sets. We examine potential uncertainties in fuel types and particle sizes on BBA-based INP concentrations. Averaged over June–September between 15°S and 50°S, BBA is a more important INP than dust and marine INP about 30% of the time at altitudes with temperatures between −30°C and −20°C. Our simulations therefore suggest BBA INPs may be at least as important as mineral dust and marine INP over the atmospheric regions and seasons where grassland fires are frequent.

Gohil, Kanishk [Carnegie Mellon University, Pittsb↗
DOE OSTI2024

Impedance sources (Z sources) with inherent fault protection for resilient and fire-free electricity grids

Modern societies would not survive without electricity and at the same time electrical faults could cause and have caused many catastrophes—mainly deadly fires—to our societies. There are two types of electricity sources: the voltage source such as generators, charged batteries and capacitors, and the current source such as charged inductors, current-regulated rectifiers, and superconducting magnetic energy storage. An “ideal” voltage source—that is often-sought-or-intentionally engineered—generates a constant voltage irrespective of its load current, and an “ideal” current source injects a constant current irrespective of its load voltage. However, two problems exist: (1) voltage or current sources do not represent many emerging natural/renewable energy sources such as wind turbine generators, photovoltaic cells, and fuel cells, whose output voltage and current are strongly dependent on each other, and (2) a short-circuit fault to an artificially-made and controlled “ideal” voltage source or an open-circuit fault to an “ideal” current source can cause catastrophic failures of the source itself and its surrounding circuits due to large (theoretically infinite) short-circuit current or open-circuit voltage. Here we introduce an impedance source concept to represent, characterize, and model those electricity sources whose output voltage and current are strongly dependent on each other. First, we found that many electric sources with no feedback (or active) control of their output voltage and/or current are a natural impedance source with inherent fault protection at short-circuit or open-circuit faults. Second, any electrical source can be artificially controlled to mimic a natural impedance source. Finally, we show how to apply natural impedance sources and nature-mimicking artificially-controlled sources to the electricity grid—the most complex machine ever made by human beings—to realize electricity grids that are naturally stable, self-protected against electrical faults, and resilient to natural and human-made events.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2014

Lowering of the firing voltage and reducing of the discharge delay time in alternating current plasma display panels by a discontinuous spin-coated LaB{sub 6} film on the MgO protective layer

A spin coated LaB{sub 6} discontinuous film is covered on MgO protective layer to improve the discharge performance of alternating current plasma display panels. Under the premise of high transmittance of more than 90%, a very small amount of polycrystal LaB{sub 6} powders added in an organic solvent are chosen as the coating solution. The discharge characteristics results show that with 250 torr 5% Xe-Ne pressure, the firing voltage and discharge delay time of the test panel with LaB{sub 6}/MgO double protective layer are decreased by 13.4% and 36.5%, respectively, compared with that of conventional MgO protective layer, likely owing to the low work function of LaB{sub 6.} Furthermore, the aging time of the proposed structure is comparable to that of pure MgO protective layer. Therefore, it will not increase the production costs and is highly suitable to be applied for alternating current plasma display panels with low electrical power consumption.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Passivation layer breakdown during laser-fired contact formation for photovoltaic devices

Low resistance laser-fired ohmic contacts (LFCs) can be formed on the backside of Si-based solar cells using microsecond pulses. However, the impact of these longer pulse durations on the dielectric passivation layer is not clear. Retention of the passivation layer during processing is critical to ensure low recombination rates of electron-hole pairs at the rear surface of the device. In this work, advanced characterization tools are used to demonstrate that although the SiO{sub 2} passivation layer melts directly below the laser, it is well preserved outside the immediate LFC region over a wide range of processing parameters. As a result, low recombination rates at the passivation layer/wafer interface can be expected despite higher energy densities associated with these pulse durations.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Keynote address: Reinventing fire: Physics + markets = energy solutions

Rocky Mountain Institute's multi-year, 61-author, peer-reviewed Reinventing Fire synthesis showed how the U.S. can realistically run a 2.6× bigger U.S. economy in 2050 with no oil, coal, or nuclear energy, one-third less natural gas, tripled efficiency, and 74% renewable supplies (80% for electricity). This transition, at historically reasonable rates, could be led by business for profit, applying normal rates of return, with some innovative subnational and administrative policies but no Acts of Congress. Excluding carbon emissions and all other externalities, the net present value would be $5 trillion more favorable than business-as-usual, averaging a 14% Internal Rate of Return.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
DOE OSTI2021

Superconducting neural networks with disordered Josephson junction array synaptic networks and leaky integrate-and-fire loop neurons

Fully coupled randomly disordered recurrent superconducting networks with additional open-ended channels for inputs and outputs are considered the basis to introduce a new architecture to neuromorphic computing in this work. Various building blocks of such a network are designed around disordered array synaptic networks using superconducting devices and circuits as an example, while emphasizing that a similar architectural approach may be compatible with several other materials and devices. A multiply coupled (interconnected) disordered array of superconducting loops containing Josephson junctions [equivalent to superconducting quantum interference devices (SQUIDs)] forms the aforementioned collective synaptic network that forms a fully recurrent network together with compatible neuron-like elements and feedback loops, enabling unsupervised learning. This approach aims to take advantage of superior power efficiency, propagation speed, and synchronizability of a small world or a random network over an ordered/regular network. Additionally, it offers a significant factor of increase in scalability. Here, a compatible leaky integrate-and-fire neuron made of superconducting loops with Josephson junctions is presented, along with circuit components for feedback loops as needed to complete the recurrent network. Several of these individual disordered array neural networks can further be coupled together in a similarly disordered way to form a hierarchical architecture of recurrent neural networks that is often suggested as similar to a biological brain.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2025

Behavioral resilience via dynamic circuit firing homeostasis

Homeostatic regulation ensures stable neural circuit output under changing conditions. We find that in Drosophila larvae, either presynaptic weakening due to perturbation of transmitter release or postsynaptic weakening due to perturbation of glutamate receptors at synapses between motor neuron (MN) and muscle has little impact on locomotion, suggesting a nonsynaptic compensatory mechanism. In vivo imaging shows that five different forms of synaptic weakening increase the duration of activity bouts in type I MNs. Strikingly, this compensation is input selective: occurring only in the tonic type Ib MN, not the phasic type Is MN that innervates the same muscle. Moreover, an inhibitory class of central pre-MNs that innervates the tonic—but not phasic—input decreases in activity. The adjustment in activity occurs remarkably quickly: within minutes of synapse perturbation. We propose that MN firing is dynamically regulated by two coordinated mechanisms: a cell-autonomous adjustment of MN excitability and a circuit adjustment of inhibitory central drive. The input selectivity of this process suggests homeostatic adjustment to maintain tonic drive but hold constant the phasic drive that organizes locomotory wave patterns.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2017

Economic Losses From a Fire in a Dense-Packed U.S. Spent Fuel Pool

In 2013, the staff of the U.S. Nuclear Regulatory Commission estimated the reduction of the off-site economic losses from a fire in a drained U.S. spent fuel pool if fuel that had cooled for more than five years were transferred to dry cask storage—an option it called “expedited transfer.” In this article, it is shown that the savings would be much higher than the NRC estimated. Savings increase to about $2 trillion if: losses beyond 50 miles are included; the land-contamination threshold for long-term population relocation is changed to that used for the Chernobyl and Fukushima accidents and recommended by the U.S. Environmental Protection Agency; and, based on the experience of Japan, decontamination of land areas to levels acceptable for population return is assumed to take at least four years. If expedited transfer were implemented, the off-site economic losses would be reduced by about 98%.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2022

Realistic operation of two residential cordwood-fired outdoor hydronic heater appliances—Part 3: Optical properties of black and brown carbon emissions

Residential biomass combustion is a source of carbonaceous aerosol. Inefficient combustion, particularly of solid fuels produces large quantities of black and brown carbon (BC and BrC). These particle types are important as they have noted effects on climate forcing and human health. One method of measuring these quantities is by measurement of aerosol light-absorption and scattering, which can be performed using an aethalometer and nephelometer, respectively. These instruments are widely deployed in the study of ambient air and are frequently used in air quality modeling and source apportionment studies. In this study, we will describe (1) a method for measuring primary BC and BrC emissions from two residential log-fired wood hydronic heaters and (2) the BC and BrC emission from these devices over a wide range of operating conditions, such as cold-starts, warm-starts, four different levels of output ranging from 15% to 100% maximum rated output, and periods of repeated cycling. The range in flue-gas BC concentrations, measured using an aethalometer at the 880 nanometer (nm) wavelength, were between 5.09 × 10 2 and 2.24 × 10 4 micrograms per cubic meter (µg/m 3 ) while the scattering coefficient of the flue-gas, measured by a nephelometer at 880 nm, ranged between 2.20 × 10 3 and 8.56 × 10 5 inverse megameters (Mm –1 ). The BrC concentrations, measured using the 370 nm wavelength of an aethalometer, were between 9.10 × 10 1 and 3.56 × 10 4 µg/m 3 . The calculated Angstrom Absorption Exponent (AAE) of the flue-gas aerosol ranged between 1.54 and 3.63. Performing a comparison between the measured BC concentration and an external particulate matter (PM) concentration showed that overall BC makes up roughly a quarter of the PM emitted by either of the two appliances. Further for both appliances, the cold-start and the test phase immediately following it had the highest BC and BrC concentrations, the highest measured scattering coefficient, as well as a low AAE.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2017

Gas kinematics, morphology and angular momentum in the FIRE simulations

We report on the z = 0 gas kinematics, morphology and angular momentum content of isolated galaxies in a suite of cosmological zoom-in simulations from the FIRE project spanning Mstar = 10 6–11 M ⊙ . Gas becomes increasingly rotationally supported with increasing galaxy mass. In the lowest mass galaxies (M star < 10 8 M ⊙ ), gas fails to form a morphological disc and is primarily dispersion and pressure supported. At intermediate masses (Mstar = 10 8–10 M ⊙ ), galaxies display a wide range of gas kinematics and morphologies, from thin, rotating discs to irregular spheroids with negligible net rotation. All the high-mass (M star = 10 10–11 M ⊙ ) galaxies form rotationally supported gas discs. Many of the haloes whose galaxies fail to form discs harbour high angular momentum gas in their circumgalactic medium. The ratio of the specific angular momentum of gas in the central galaxy to that of the dark matter halo increases significantly with galaxy mass, from $\langle$jgas$\rangle$$\langle$jDM$\rangle$ ~ 0.1 at M star =10 6--7 M⊙ to$\langle$gas$\rangle$/$\langle$jDM$\rangle$ ~ 2 at M star = 1010–11 M ⊙ . The reduced rotational support in the lowest mass galaxies owes to (a) stellar feedback and the UV background suppressing the accretion of high angular momentum gas at late times, and (b) stellar feedback driving large non-circular gas motions. We broadly repeat the observed scaling relations between galaxy mass, gas rotation velocity, size and angular momentum, but may somewhat underpredict the incidence of disky, high angular momentum galaxies at the lowest observed masses (Mstar = (10 6 -2× 10 7 ) M ⊙ ). Stars form preferentially from low angular momentum gas near the galactic centre and are less rotationally supported than gas. The common assumption that stars follow the same rotation curve as gas thus substantially overestimates the simulated galaxies’ stellar angular momentum, particularly at low masses.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

Formation of globular cluster candidates in merging proto-galaxies at high redshift: a view from the FIRE cosmological simulations

Using a state-of-the-art cosmological simulation of merging proto-galaxies at high redshift from the FIRE project, with explicit treatments of star formation and stellar feedback in the interstellar medium, we investigate the formation of star clusters and examine one of the formation hypotheses of present-day metal-poor globular clusters. Here, we find that frequent mergers in high-redshift proto-galaxies could provide a fertile environment to produce long-lasting bound star clusters. The violent merger event disturbs the gravitational potential and pushes a large gas mass of ≳ 10 5–6 M ⊙ collectively to high density, at which point it rapidly turns into stars before stellar feedback can stop star formation. The high dynamic range of the reported simulation is critical in realizing such dense star-forming clouds with a small dynamical time-scale, tff ≲ 3 Myr, shorter than most stellar feedback time-scales. Our simulation then allows us to trace how clusters could become virialized and tightly bound to survive for up to ~420 Myr till the end of the simulation. Finally, because the cluster's tightly bound core was formed in one short burst, and the nearby older stars originally grouped with the cluster tend to be preferentially removed, at the end of the simulation the cluster has a small age spread.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2026

Half-ice, half-fire-driven ultranarrow phase crossover in one-dimensional decorated 𝑞-state Potts ferrimagnets: An AI-co-led exploration

OpenAI’s reasoning model o3-mini-high was used to carry out an exact analytic study of one-dimensional ferrimagnetic site- and bond-decorated 𝑞-state Potts models. We demonstrate that the finite-temperature ultranarrow phase crossover (UNPC), driven by a hidden “half-ice, half-fire” state recently discovered in the 𝑞=2 case (Ising model), persists for 𝑞>2. Moreover, we identify unique features for 𝑞>2, including the dome structure in the field-temperature phase diagram, and for large 𝑞 a secondary high-temperature UNPC to the fully disordered paramagnetic state. As the UNPC quickly approaches a genuine transition by enhancing 𝐽, the interaction between the backbone spins, two distinct behaviors emerge: In the site-decorated Potts model, 𝑇 0 is independent of 𝐽 and thus remains unchanged (Type-I UNPC), and in the bond-decorated Potts model with 𝑞>2, 𝑇 0 depends on 𝐽 and quickly shifts toward a finite temperature as 𝐽 increases (Type-II UNPC). These results establish a versatile framework for engineering controlled fast state-flipping switches in low-dimensional systems. Our nine-dan artificial intelligence (AI)-contribution framework assigns AI the meritorious status of AI-co-led discovery in this work.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Numerical Model of Thermoelectric Topping Cycle of Coal-Fired Power Plant

Traditional fossil fuel power generation process typically has low efficiency. Large amount of the energy loss in Rankine cycle steam turbines (ST) is due to the temperature difference between the combustion flame temperature ~2250 K (adiabatic) and the high pressure steam temperature up to 900 K. However, some of this energy can be harvested using solid-state thermoelectric (TE) power generators which are placed into the gap between the flame temperature and the steam temperature that produce additional electrical power. This study investigates the potential placement of TE on water tube wall inside a boiler at a coal-fired power plant. Three-dimensional (3D) numerical model of a simplified TE module is developed, and hot gas temperature and steam temperature from the boiler are used as boundary conditions at the hot side and cold side of the TE. The numerical results are compared with analytical calculations. The 3D effects of the thermal spreading in the TE module are investigated. Parameters such as TE leg cross section area and TE fill factor are examined in order to maximize the electrical power production of the TE without sacrificing the boiler efficiency (i.e., reducing the steam temperature). The study also looks into the various locations inside the boiler that have good potential for TE installation.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2021

A High-Fidelity Modeling Tool to Support the Design of Oxy-Combustors for Direct-Fired Supercritical CO2 Cycles

The challenge in the design of oxy-combustors for direct-fired supercritical CO 2 (sCO 2 ) cycles is in addressing disparate performance metrics and objectives. Key design parameters to consider include, among others, injector design for mixing and flame stability, split of recycled CO 2 diluent between injectors and cooling films, target flame temperatures to control noncondensable products, and strategies to inject the diluent CO 2 for film cooling and thermal control. In order to support novel oxy-combustor designs, a high-fidelity yet numerically efficient modeling framework based on the CRUNCH CFD® flow solver is presented, featuring key physics-based submodels relevant in this regime. For computational efficiency in modeling large kinetic sets, a flamelet/progress variable (FPV) based tabulated-chemistry approach is utilized featuring a three-stream extension to allow for the simulation of the CO 2 film cooling stream in addition to the fuel and oxidizer streams. Finite rate chemistry effects are modeled in terms of multiple progress variables for the primary flame as well as for slower-evolving chemical species such as NO x and SO x contaminants. Real fluid effects are modeled using advanced equations of states. The predictive capabilities of this computationally tractable design support tool are demonstrated on a conceptual injector design for an oxy-combustor operating near 30 MPa. Simulations results provide quantitative feedback on the effectiveness of the film cooling as well as the level of contaminants (CO, NO, and N) in the exhaust due to impurities entering from the injectors. These results indicate that this framework would be a useful tool for refining and optimizing the oxy-combustor designs as well as risk mitigation analyses.

Engineering↗
DOE OSTI2021

Theoretical Analysis of a Single-Stage Gas-fired Ejector Heat Pump Water Heater

Ejector-driven systems have the ability to operate at high efficiencies, utilizing recycled thermal energy as a power source. For a typical ejector heat pump (EHP) system, the increase of the condenser temperature reduces the coefficient of performance (COP). In addition, if the condenser temperature is higher than the critical temperature, the ejector may not function. In this situation, the condenser temperature must be reduced, and an additional heater will be utilized to heat the production water from the condenser temperature to the desired temperature. In this study, a single-stage gas-fired EHP is investigated and thermodynamically modeled to optimize the system COP for the purpose of heating water by utilizing the thermal energy from the ambient air. The effects of the high-temperature evaporator (HTE) and low-temperature evaporator (LTE) on the ejector critical back pressure and the EHP system performance are examined for a HTE temperature range of 120–180 °C and LTE temperatures of 15.5, 17.5, and 19.5 °C. Our results show that an optimized COP for the EHP system exists and is dependent on HTE and LTE temperatures and the primary nozzle throat diameter. In addition, it is found that the peak EHP COP does not necessarily coincide with a large ejector COP. From this study, a maximum EHP COP of 1.31 is achieved at a HTE temperature of 170 °C and LTE temperature of 19.5 °C with a total heating capacity of 15.98 kW.

42 ENGINEERING↗
DOE OSTI2021

Impact on Cycle Efficiency of Small Combined Heat and Power Plants from Increasing Firing Temperature Enabled by Additive Manufacturing of Turbine Blades and Vanes

The results of this study show that a 180°F (100°C) increase in firing temperature can increase the gas turbine efficiency by 1 percentage point without improving cooling effectiveness and add 2 additional percentage points in efficiency by using advanced turbine blades with higher internal cooling efficiency. The engine upgrades evaluated in this study show potential for increasing the CHP cycle efficiency by 3 percentage points while increasing the steam generation rate by 8%.

Uysal, Selcuk Can↗
DOE OSTI2021

Theoretical Analysis of a Single-Stage Gas-Fired Ejector Heat Pump Water Heater

Ejector driven systems have the ability to operate at high efficiencies, utilizing recycled thermal energy as a power source. For a typical ejector heat pump system, the increase of the condenser temperature reduces the coefficient of performance (COP). In addition, if the condenser temperature is higher than the critical temperature, the ejector may not function. In this situation, the condenser temperature must be reduced, and an additional heater will be utilized to heat the production water from the condenser temperature to the desired temperature. In this investigation, a single-stage gas-fired ejector heat pump (EHP) is investigated and thermodynamically modeled in order to optimize the system COP for the purpose of heating water by utilizing the thermal energy from the ambient air. The effects of the high-temperature evaporator (HTE) and low-temperature evaporator (LTE) temperatures on the ejector critical back pressure and the EHP system performance are examined for a HTE temperature range of 120–180 °C and LTE temperatures of 15.5, 17.5, and 19.5 °C. Results show that an optimized COP of the EHP system exists which depends on HTE and LTE temperatures, primary nozzle throat diameters. In addition, it is found that the EHP COP is independent of the ejector COP. From this investigation a maximum EHP COP of 1.31 is able to be achieved for a HTE temperature of 160 °C and a LTE temperature of 19.5 °C with a total heat capacity of 15.98 kW.

Spitzenberger, Jeremy↗
DOE OSTI2020

Data Analytics Applied to Coal Fired Boilers for Detecting Leaks

Data analytics were used to detect boiler leaks from five different coal-fired boilers including both subcritical and supercritical systems. Discriminant functions were developed that detected leaks up to two weeks prior to forced plant shutdowns for repairs. The leaks were identified to occur at different sections of the boiler for each plant, including waterwalls, economizer and superheater using conventional process measurement data. Leaking conditions were detected with a high degree of confidence (&NestedLessLess; 1% misclassified observations) and were able to distinguish normal operations from those time periods with steam leaks even while operating the power plants in power cycling mode.Multivariable statistical analyses, including Principal Component (PCA), cluster, and Fischer Discriminant Analysis (FDA) were used to characterize the leak occurrence. Normal and operational states with steam leaks were provided in the original process datasets. These datasets were split into two different groups for training and validation purposes. The data were sorted chronologically, and every third observation was assigned to training the Discriminant Function Model (DFM) while the rest were reserved for validation. PCA was used to reduce dimensionality of the original datasets. Canonical and FDA analyses were used to investigate the relationship between process variables. The outcome of the analyses revealed that nearly 35,000 observations were classified correctly; less than 0.05% of total observations were misclassified to be leaking, i.e. both false positives and false negatives.

Indrawan, Natarianto↗