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At least 577 records · Page 32
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Performance Evaluation of Drain Water Heat Recovery Exchangers for Heat Pump Water Heaters

Water heating constitutes approximately 18% of energy consumption and is the second largest energy expenses in United States homes. Heat pump water heaters (HPWHs) are energy efficient technologies with lower carbon footprints as compared to conventional water heating technologies, such as gas and electrical resistance heaters. The performance of water-source HPWHs can be improved by recovering heat from blackwater using drain heat recovery heat exchangers. Depending on water draw patterns of single family and multifamily residences, the operation and heat transfer performance of these heat exchangers are highly transient. This paper examines the thermo-hydraulic performance of a drain heat recovery heat exchanger during its transient and steady-state operations. The heat recovery performance of the exchanger was evaluated at different inlet temperatures and flow rates ranging from 9°C to 36°C and 0.03 kg/s to 0.28 kg/s, respectively. The obtained effectiveness varies from 45%–85% depending on the operating conditions. The test facility, steady-state and transient experimental procedures are reported in detail. Further, the effect of operating conditions on the effectiveness is discussed. The experimental approach and results of the study will provide insights into the transient operation of drain recovery heat exchangers as well as, guide sizing for various steady state conditions.

Krishnan, Easwaran↗
NASA NTRS1982

The evolution of an impact-generated atmosphere

The minimum impact velocities and pressures required to form a primary H2O atmosphere during planetary accretion from chondritelike planetessimals are determined by means of shock wave and thermodynamic data for rock-forming and volatile-bearing minerals. Attenuation of impact-induced shock pressure is modelled to the extent that the amount of released water can be estimated as a function of projectile radius, impact velocity, weight fraction of target water, target porosity, and dehydration efficiency. The two primary processes considered are the impact release of water bound in such hydrous minerals as serpentine, and the subsequent reincorporation of free water by hydration of forsterite and enstatite. These processes are described in terms of model calculations for the accretion of the earth. It is concluded that the concept of dehydration efficiency is of dominant importance in determining the degree to which an accreting planet acquires an atmosphere during its formation.

Lange, M. A.↗
DOE OSTI2020

What Factors Drive the Changes in Water Withdrawals in the U.S. Agriculture and Food Manufacturing Industries between 1995 and 2010?

Climate change and increasing world population will directly impact the global food supply chain linkages. In the United States, agricultural production requires less irrigated water than before but it still accounts for a third of total water withdrawals. To better understand the evolution of its water use, we perform a structural decomposition analysis of water withdrawals across eight different crops and six livestock categories and differentiate the trends over 1995–2005 vs 2005–2010 to account for the role of the economic crisis in the second period. Based on USGS data, the results show that both periods experienced an overall decline in water withdrawals in the production of all crops except oilseeds. This trend is driven by a decrease in water intensity, reflecting greater efficiency of irrigation systems, and by reduced local per capita income in the second period. However, increased foreign demand for water-intensive sectors like oilseeds from NAFTA and Asian partners mitigated the decline. Results indicate also a decreasing water use in livestock production partially due to a shift from red to white meat consumption in the country. Arguably, recent tariff wars and border closures have greatly reduced the virtual water embodied in American exports.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
DOE OSTI2020

Efficient Intermolecular Energy Exchange and Soft-ionization of Water at Nanoplatelet Interfaces

X-ray, energetic photon and electron irradiation can ionize and electronically excite target atoms and molecules. These excitations undergo complicated relaxation and energy transfer processes that ultimately determine the manifold of system responses to the deposited excess energy. In weakly bound gas- and solution-phase samples, intermolecular Coulomb decay (ICD) and electron-transfer mediated decay (ETMD) can occur with neighboring atoms or molecules leading to efficient transfer of the excess energy to the surroundings. In ionic solids such as metal-oxides, intra- and inter-atomic Auger decay produces localized final states that lead to lattice damage and typically removal of cations from the substrate. The relative importance of Auger stimulated damage (ASD) versus ICD and ETMD in micro-solvated nanoparticle interfaces is not known. Though ASD is generally expected, essentially no lattice damage and very efficient ICD and ETMD resulting from ionization and electronic excitation of micro-solvated boehmite (AlOOH) nanoplatelets has been observed. Efficient energy transfer and soft ionization of interfacial molecules is likely a general phenomenon at gas-oxyhydroxide nanoparticle interfaces where the density of states of the ionized chemisorbed species significantly overlap the core hole states of the solid.

Jones, Brant M.↗
NASA NTRS2021

Simultaneous Ice Water Content Measurements at Multiple Locations on the NASA DC-8 Aircraft during the 2018 HIWC RADAR Flight Campaign

Ice water content measurements were made simultaneously at three locations on the NASA DC-8 in natural, glaciated conditions during the 2018 High Ice Water Content RADAR flight campaign. The purpose of these measurements was to further evaluate efficiency factors of hot-wire total water content probes in glaciated conditions and investigate the enhancement of ice crystal concentrations near fuselage surfaces due to flow field inertial effects, and ice crystals impacting the nose, breaking up, and flowing downstream. The total water content measurements were made using either Science Engineering Associates Ice Crystal Detectors or Robust Probes. Three common sensors were mounted on an underwing canister considered to be in near free-flow conditions, a standoff from a fuselage window, and the nose of the fuselage near the pitot probes. The Ice Crystal Detector concave total water content sensor and Robust Probe sensor collection and retention efficiencies were evaluated through comparisons with the underwing Ice Crystal Detector and Robust Probe measurements to the Isokinetic Probe version 2 (IKP2), which provided the reference ice water content measurement. Local ice water content at the nose position was evaluated by comparing ratios of the nose and underwing ice crystal detectors to the IKP2. Local ice water content at the window-standoff location was also evaluated by comparing total water content sensor measurements from the window probes to the measurements made with the underwing and nose probes. The key findings were: (1) the Ice Crystal Detector concave water content sensor efficiency factor to glaciated conditions was similar to previous estimates, but reduced with increased ice crystal median mass diameter; (2) the ice water content at the fuselage nose location near the DC-8 pitot probes was approximately 2.5 times the freestream values—although this estimate is affected by a higher probe efficiency factor due to smaller particles in the debris cloud from impacts upstream of the probe; and (3) the ice water content at the 17 in. standoff from the port window varied from about 50 percent to nearly three times freestream values in a complicated manner. Similar measurement locations are not uncommon on cloud research aircraft, where ice particle measurements may be subject to similar uncertainties.

Aircraft Icing↗
DOE OSTI2021

A perspective on ordered vacancy compound and parent chalcopyrite thin film absorbers for photoelectrochemical water splitting

Chalcopyrites could fill the gap between the low-cost, poor-efficiency single junction metal oxide photoelectrochemical (PEC) water splitting cells and the high efficiency, yet costly III–V tandems. In this Perspective, we first review the key barriers that must be addressed by the community to enable economical chalcopyrite-based PEC water splitting. Then, we highlight how theoretical modeling can be used to identify promising ordered vacancy compound absorbers with improved energetics compared to their chalcopyrite parents. Finally, we describe how advanced spectroscopic analysis performed on chalcopyrite photocathodes after PEC testing uncovered a new passivation layer candidate for prolonged durability.

08 HYDROGEN↗
DOE OSTI2022

A combined theoretical and experimental study of small anthracene–water clusters

Water-cluster interactions with polycyclic aromatic hydrocarbons (PAHs) are of paramount interest in many chemical and biological processes. Here we report a study of anthracene monomers and dimers with water (up to four)-cluster systems utilizing molecular beam vacuum-UV photoionization mass spectrometry and density functional calculations. Structural loss in photoionization efficiency curves when adding water indicates that various isomers are generated, while theory indicates only a slight shift in energy in photoionization states of different isomers. Calculations reveal that the energetic tendency of water is to remain clustered and not to disperse around the PAH. Theoretically, we observe water confinement exclusively in the case of four water clusters and only when the anthracenes are in a cross configuration due to optimal OH∙∙∙π interactions, indicating dependence on the size and structure of the PAH. Furthermore theory sheds light on the structural changes that occur in water upon ionization of anthracene, due to the optimal interactions of the resulting hole and water hydrogen atoms.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS2005

Condensing Heat Exchanger Concept Developed for Space Systems

The current system for moisture removal and humidity control for the space shuttles and the International Space Station uses a two-stage process. Water first condenses onto fins and is pulled through "slurper bars." These bars take in a two-phase mixture of air and water that is then separated by the rotary separator. A more efficient design would remove the water directly from the air without the need of an additional water separator downstream. For the Condensing Heat Exchanger for Space Systems (CHESS) project, researchers at the NASA Glenn Research Center in collaboration with NASA Johnson Space Center are designing a condensing heat exchanger that utilizes capillary forces to collect and remove water and that can operate in varying gravitational conditions including microgravity, lunar gravity, and Martian gravity.

Hasan, Mohammad M.↗
DOE OSTI2025

Stable Metal–Organic Electrocatalysts for Anion-Exchange Membrane Water Electrolyzers by Defect Engineering

Developing efficient and durable catalysts for the alkaline oxygen evolution reaction (OER) is vital to achieving practical anion-exchange membrane water electrolyzers (AEMWE) for green hydrogen production. In this work, we break the activity-stability trade-off of electrocatalysis by defect engineering of Ni-based metal-organic electrocatalysts (Ni-benzene dicarboxylate; Ni-BDC) through coordinating ferrocenecarboxylates (Fc) to the metal sites. Experimental results collectively reveal that the defect MOF (Ni-BDC:Fc_5:1) exhibits a high OER turnover frequency of 0.75 O 2 s -1 at 300 mV overpotential. Operando Raman spectroscopy and isotope-labelling electrochemical mass spectrometry measurements indicate the structure of Ni-BDC:Fc_5:1 is also more stable in service than that of pure Ni-BDC. The high activity and stability could be attributed to the moderate defects (i.e., unsaturated Ni sites) in the structure that not only increase the intrinsic activity and stability of the local active environment by inhibiting lattice oxygen exchange, but also electrochemically activates the bulk of the catalysts by creating a porous network that facilitates internal H 2 O/OH - conduction with enhanced electronic conduction. Accordingly, an AEMWE employing Ni-BDC:Fc_5:1 as the OER catalyst delivers an industrial-level current density of 1 A cm -2 at 1.73 V cell and can be steadily operated for more than 120 hours.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS2001

The Runaway Greenhouse Effect on Earth and other Planets

Water vapor is an efficient absorber of outgoing longwave infrared radiation on Earth and is the primary greenhouse gas. Since evaporation increases with increasing sea surface temperature, and the increase in water vapor further increases greenhouse warming, there is a positive feedback. The runaway greenhouse effect occurs if this feedback continues unchecked until all the water has left the surface and enters the atmosphere. For Mars and the Earth the runaway greenhouse was halted when water vapor became saturated with respect to ice or liquid water respectively. However, Venus is considered to be an example of a planet where the runaway greenhouse effect did occur, and it has been speculated that if the solar luminosity were to increase above a certain limit, it would also occur on the Earth. Satellite data acquired during the Earth Radiation Budget Experiment (ERBE) under clear sky conditions shows that as the sea surface temperature (SST) increases, the rate of outgoing infrared radiation at the top of the atmosphere also increases, as expected. Over the pacific warm pool where the SST exceeds 300 K the outgoing radiation emitted to space actually decreases with increasing SST, leading to a potentially unstable system. This behavior is a signature of the runaway greenhouse effect on Earth. However, the SST never exceeds 303K, thus the system has a natural cap which stops the runaway. According to Stefan-Boltzmann's law the amount of heat energy radiated by the Earth's surface is proportional to (T(sup 4)). However, if the planet has a substantial atmosphere, it can absorb all infrared radiation from the lower surface before the radiation penetrates into outer space. Thus, an instrument in space looking at the planet does not detect radiation from the surface. The radiation it sees comes from some level higher up. For the earth#s atmosphere the effective temperature (T(sub e)) has a value of 255 K corresponding to the middle troposphere, above most of the water vapor and clouds. "Additional information is contained in the original extended abstract."

Rabbette, Maura↗
DOE OSTI2024

Electrothermal mineralization of per- and polyfluoroalkyl substances for soil remediation

Abstract Per- and polyfluoroalkyl substances (PFAS) are persistent and bioaccumulative pollutants that can easily accumulate in soil, posing a threat to environment and human health. Current PFAS degradation processes often suffer from low efficiency, high energy and water consumption, or lack of generality. Here, we develop a rapid electrothermal mineralization (REM) process to remediate PFAS-contaminated soil. With environmentally compatible biochar as the conductive additive, the soil temperature increases to >1000 °C within seconds by current pulse input, converting PFAS to calcium fluoride with inherent calcium compounds in soil. This process is applicable for remediating various PFAS contaminants in soil, with high removal efficiencies ( >99%) and mineralization ratios ( >90%). While retaining soil particle size, composition, water infiltration rate, and cation exchange capacity, REM facilitates an increase of exchangeable nutrient supply and arthropod survival in soil, rendering it superior to the time-consuming calcination approach that severely degrades soil properties. REM is scaled up to remediate soil at two kilograms per batch and promising for large-scale, on-site soil remediation. Life-cycle assessment and techno-economic analysis demonstrate REM as an environmentally friendly and economic process, with a significant reduction of energy consumption, greenhouse gas emission, water consumption, and operation cost, when compared to existing soil remediation practices.

Science & Technology - Other Topics↗
DOE OSTI2026

Water as a gas separation membrane

Efficient gas separation membranes are essential for carbon capture, biogas upgrading, and hydrogen purification. Inspired by how plants absorb CO 2 through water, we present a membrane platform that uses liquid water as the selective layer. Hydrophilic sub-100-nm pores stabilize water through strong capillary forces, enabling operation at feed pressures above 72 bar under dry and humid conditions. Selectivity is governed by gas solubility in water, while permeance is tuned by adjusting the water layer thickness. Reducing this thickness below 200 nm yields CO 2 permeances up to 11,600 gas permeation units with CO 2 :N 2 , CO 2 :CH 4 , and CO 2 :H 2 selectivities of 40, 26, and 31, respectively, surpassing the performance of state-of-the-art membranes. Operation is sustained for over a week without water loss, and performance scales using commercially available porous polymer supports under mixed-gas crossflow conditions. Water’s dissolution-based transport avoids saturation and reaction-rate limits, enabling a robust, high-performance, and environmentally benign gas separation platform.

08 HYDROGEN↗
DOE OSTI2021

Modeling State Transition and Head-Dependent Efficiency Curve for Pumped Storage Hydro in Look-Ahead Dispatch

As one of the most widely installed utility-scale storage facilities, pumped storage hydro (PSH) plays an essential role in providing flexibility for power systems worldwide. Thus, to accurately quantify the flexibility of PSH units in operational optimization problems is important. The conventional PSH models in the literature rarely consider detailed state transitions due to their hourly-based settings. However, it becomes imperative for operational optimization on short-term intervals, especially with increasing shares of renewable energy in power systems. To this end, this paper presents a novel deterministic PSH model that considers the transition time and trajectory between three states of PSH units in look-ahead dispatch. Moreover, to better characterize the varying efficiency of PSH units with water head and flow rate, this paper proposes to model detailed headdependent efficiency curves (hereafter called input-output curves) in look-ahead dispatch, which encounters heavy computational burdens when short time intervals are applied. In this work, a zig-zag piece-wise linear approximation method is used for input-output curve modeling. This can enable an accurate quantification for variable efficiency and head dependence in a computationally effective manner. Here, numerical results are presented to show performances of the proposed PSH model in both flexibility quantification and computation time.

13 HYDRO ENERGY↗
DOE OSTI2022

Highly supercooled riming and unusual triple-frequency radar signatures over McMurdo Station, Antarctica

Abstract. Riming of ice crystals by supercooled water droplets is an efficient ice growth process, but its basic properties are still poorly known. While it has been shown to contribute significantly to surface precipitation at mid-latitudes, little is known about its occurrence at high latitudes. In Antarctica, two competing effects can influence the occurrence of riming: (i) the scarcity of supercooled liquid water clouds due to the extremely low tropospheric temperatures and (ii) the low aerosol concentration, which may lead to the formation of fewer and larger supercooled drops potentially resulting in an enhanced riming efficiency. In this work, by exploiting the deployment of an unprecedented number of multiwavelength remote sensing systems (including triple-frequency radar measurements) in West Antarctica, during the Atmospheric Radiation Measurements West Antarctic Radiation Experiment (AWARE) field campaign, we evaluate the riming incidence at McMurdo Station and find that riming occurs at much lower temperatures when compared to previous results in the mid-latitudes. This suggests the possible occurrence of a common atmospheric state over Antarctica that includes a rather stable atmosphere inhibiting turbulent mixing, and a high riming efficiency driven by large cloud droplets. We then focus on a peculiar case study featuring a persistent layer with a particularly pronounced riming signature in triple-frequency radar data but only a relatively modest amount of supercooled liquid water. In-depth analysis of the radar observations suggests that such signatures can only be explained by the combined effects of moderately rimed aggregates or similarly shaped florid polycrystals and a narrow particle size distribution (PSD). Simulations of this case study performed with a one-dimensional bin model indicate that similar triple-frequency radar observations can be reproduced when narrow PSDs are simulated. Such narrow PSDs can in turn be explained by two key factors: (i) the presence of a shallow homogeneous droplet or humidified aerosol freezing layer aloft seeding an underlying supercooled liquid layer, and (ii) the absence of turbulent mixing throughout a stable polar atmosphere that sustains narrow PSDs, as hydrometeors grow from the nucleation region aloft to ice particles of several millimeters in size, by vapor deposition and then riming.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS2022

Highly Supercooled Riming and Unusual Triple-Frequency Radar Signatures Over McMurdo Station, Antarctica

Riming of ice crystals by supercooled water droplets is an efficient ice growth process, but its basic properties are still poorly known. While it has been shown to contribute significantly to surface precipitation at mid-latitudes, little is known about its occurrence at high latitudes. In Antarctica, two competing effects can influence the occurrence of riming: (i) the scarcity of supercooled liquid water clouds due to the extremely low tropospheric temperatures and (ii) the low aerosol concentration, which may lead to the formation of fewer and larger supercooled drops potentially resulting in an enhanced riming efficiency. In this work, by exploiting the deployment of an unprecedented number of multiwavelength remote sensing systems (including triple-frequency radar measurements) in West Antarctica, during the Atmospheric Radiation Measurements West Antarctic Radiation Experiment (AWARE) field campaign, we evaluate the riming incidence at McMurdo Station and find that riming occurs at much lower temperatures when compared to previous results in the mid-latitudes. This suggests the possible occurrence of a common atmospheric state over Antarctica that includes a rather stable atmosphere inhibiting turbulent mixing, and a high riming efficiency driven by large cloud droplets. We then focus on a peculiar case study featuring a persistent layer with a particularly pronounced riming signature in triple-frequency radar data but only a relatively modest amount of supercooled liquid water. In-depth analysis of the radar observations suggests that such signatures can only be explained by the combined effects of moderately rimed aggregates or similarly shaped florid polycrystals and a narrow particle size distribution (PSD). Simulations of this case study performed with a one-dimensional bin model indicate that similar triple-frequency radar observations can be reproduced when narrow PSDs are simulated. Such narrow PSDs can in turn be explained by two key factors: (i) the presence of a shallow homogeneous droplet or humidified aerosol freezing layer aloft seeding an underlying supercooled liquid layer, and (ii) the absence of turbulent mixing throughout a stable polar atmosphere that sustains narrow PSDs, as hydrometeors grow from the nucleation region aloft to ice particles of several millimeters in size, by vapor deposition and then riming.

Riming↗
DOE OSTI2023

Catalyzing the Mass Adoption of High Efficiency Technologies in the Multifamily Housing Market

ICAST’s objective was to catalyze the adoption of very-high-efficiency (VHE) heat pump HVAC (mini-splits) and water heaters (HPWH) in multifamily (MF), especially affordable housing (MFAH). Nationally, the market penetration of ENERGY STAR-certified ASHPs is estimated at 43%, and for HPWHs it’s 3% (ENERGY STAR, 2022). Note that mini-splits are a much more practical choice for MF units than ducted systems and their adoption is only a portion of the number provided above, but isolating the market penetration data for mini-split systems is difficult. Both the heat pump-based HVAC and water heater systems can be approx. three times more efficient than their conventional counterparts for space and water heating. While awareness and adoption of VHE heat pumps has been growing nationally, and electric heat pump systems have outsold gas furnaces for two years in a row, the MF segment continues to lag behind single-family. MF constitutes almost a third of the housing in the U.S., so scaling up VHE adoption in this segment can assist in achieving critical climate change goals, while preserving housing affordability for the low-to-moderate income (LMI) population (historically, 85% of residents of MF are LMI).

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2023

Modification of CO 2 /H 2 O selectivity of polymer for carbon capture materials

Today, the atmospheric carbon dioxide (CO 2 ) concentration is 421ppm, over one hundred ppm higher than it was at any point in the last 800,000 years (NASA, 2023). Multiple strategies are necessary to reduce the presence of carbon dioxide in the atmosphere. Besides limiting CO 2 output, carbon capture technology is essential to reduce the overall amount of CO 2 . The Microencapsulated CO 2 Sorbents (MECS) team at Lawrence Livermore National laboratory has developed technologies that can capture CO 2 inside microcapsules, where it can be temporarily stored and later released. In 2017, the commercial potential of these microcapsules was recognized. The brewing industry only requires about one third of the CO 2 it releases for carbonization and packaging, which Congwang Ye and Lionel Keene learned when they met with leaders of small breweries in Colorado to discuss employing carbon capture microcapsules in their processes to reduce their carbon footprint and production costs (Thomas, 2017). The breweries were interested in the technology, but the existing microcapsules require hydration, which is an expensive process for small brewers. In order to develop the microcapsules so they can be commercialized, it is essential to reduce their water loss to improve efficiency and reduce costs for the customers. One method to resolve this issue is to alter the membrane formulation by adding a material that is known to be hydrophobic to decrease the water permeability of the entire membrane. The goal of this project was to study the effect of dispersing a nanomaterial in the polymer membrane shells of microcapsules on the water vapor and carbon dioxide permeability of the membranes.

36 MATERIALS SCIENCE↗