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At least 1,315 records · Page 73

Data from: "Warming of alpine tundra enhances belowground production and shifts community towards resource acquisition traits"

This archive contains data used to draw conclusions in “Warming of alpine tundra enhances belowground production and shifts community towards resource acquisition traits”, by Yang et al. 2020. Data were collected on Niwot Ridge, in an alpine meadow within the Alpine Treeline Warming Experiment (ATWE) field sites in Colorado, USA. Samples were also processed in the U.S. Geological Survey Forest and Rangeland Ecosystem Science Center, in Boise, Idaho. File formats in this archive include comma-separated values (.csv), portable document format (.pdf), Microsoft Excel (.xlsx), and two types of geospatial files: keyhole markup language (.kml), and ESRI shapefiles (.shp). Leaf scans are .jpg images, and root scans are .tiff/.tif images.The .csv files can be opened using R, Microsoft Excel, or any simple text-editing software such as TextEdit and Notepad. Microsoft Excel files can be opened using Microsoft Excel, and .pdf files can be opened with Adobe Acrobat Reader, Preview, or other compatible programs. Scanned images can be opened using any photo and/or picture viewing software.The .kml file can be opened using Google Earth and Google Maps, and the shapefiles can be opened by any programs compatible with shapefiles, such as the ArcGIS Desktop suite, and QGIS.------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------Measures of belowground net primary productivity (BNPP) are required to understand whether aboveground net primary production (ANPP) changes reflect changes in allocation or are indicative of a whole plant NPP response. Plant functional traits provide a key way to scale from the individual plant to the community level, and provide insight into drivers of NPP responses to environmental change. We used infrared heaters to warm an alpine plant community at Niwot Ridge, Colorado, and applied supplemental water to compensate for soil water loss induced by warming. We measured ANPP, BNPP, and leaf and root functional traits across treatments after 5 years of continuous warming. Community-level ANPP and total NPP (ANPP + BNPP) did not respond to heating or watering, but BNPP increased in response to heating. Heating decreased community-level leaf dry matter content and increased total root length, indicating a shift in strategy from resource conservation to acquisition in response to warming.

13C/12C isotope ratio↗

Tierra del Fuego Case Study Capacity Expansion Analysis

This case study, developed by Net Zero World Initiative and the Government of Argentina, examines least-cost decarbonization pathways for Tierra del Fuego, Argentina, utilizing renewable energy, energy storage, hydrogen, and other decarbonization technologies. Being the second largest natural gas producing province in Argentina, Tierra del Fuego has historically relied on natural gas for their energy sector needs. As they look at possible decarbonization pathways, they face challenges due to extreme weather conditions, isolation from the mainland, and low population density. The study utilizes the Engage web application for capacity expansion modeling, addressing both business-as-usual (BAU) and accelerated decarbonization scenarios, with varying degrees of electrification and carbon emission constraints. Key findings reveal that an interconnection with the mainland, high contribution of wind energy development on Tierra del Fuego, energy storage, and hydrogen, coupled with energy-efficient electrification technologies (such as heat pumps and electric vehicles), emerge as the most cost-effective solutions to decarbonize, significantly reducing carbon emissions and total system energy costs. The study explores self-generation and interconnection alternatives, demonstrating the economic advantage of an interconnection of Tierra del Fuego with the mainland, as an alternative to 100% local generation. Sensitivity analyses on wind data sources and temporal resolutions, as well as projected natural gas prices, highlight the influence of external factors on the feasibility of decarbonization pathways. Challenges identified include the practicality of phasing out natural gas, economic uncertainty, cost implications of long-term storage technologies as wind energy increases, and geographical limitations for wind generation. The case study concludes that while substantial emissions reductions can be achieved by 2050, and be competitive with conventional pathways, achieving a full 100% decarbonization by 2050 would entail higher costs, particularly due to the significant reliance on storage solutions with higher contribution of wind energy. The analysis offers valuable insights for policymakers and stakeholders in Argentina's energy sector, emphasizing the importance of strategic planning, investment in renewable energy and storage technologies, and careful consideration of local conditions in the transition towards Net Zero targets.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗

Antarctic Cloud Macrophysical, Thermodynamic Phase, and Atmospheric Inversion Coupling Properties at McMurdo Station—Part II: Radiative Impact During Different Synoptic Regimes

Different cloud types are generated over Antarctica as a result of various synoptic conditions. The cloud characteristics affect their impact on the surface energy budget. In this study, the dominating synoptic regimes over Antarctica (centered on the Ross Ice Shelf) are classified using self-organizing map (SOM) analysis, applied over long-term ERA-Interim 700 hPa geopotential height data. The corresponding cloud properties over McMurdo Station (measured as part of the AWARE campaign) are described and discussed with respect to the synoptic settings and sea-ice extent conditions. Cloud radiative forcing calculations are performed as well, and a particular focus is given to the net longwave “radiatively cloudy/opaque” (RO) regime. These results are compared with measurements performed at the West Antarctic Ice Sheet (WAIS) Divide to examine their variability and applicability to other Antarctic locations. It is found that the McMurdo cloud properties are strongly affected by the regional mesoscale cyclonic activity, which counterweights the larger-scale synoptic regime influence, while the WAIS clouds are more susceptible to the varying synoptic settings. In addition, it is suggested that the positive trend in the (frequent) cyclonic activity near the Antarctic coastal regions makes ice-clouds an increasing prominent contributor for the RO cases, especially during freeze-up and maximum sea-ice conditions.

antarctic clouds↗

Beyond Price-Taker: Multiscale Optimization of Wind and Battery Integrated Energy Systems

Integrating renewable energy into the electric grid is challenging due to the intermittency and variability of wind and other non-dispatchable resources. Integrated energy systems (IESs) combine multiple energy technologies (e.g., fossil, nuclear, renewables, storage) to reduce costs and improve flexibility and reliability. However, standard techno-economic analysis (TEA) methods often overestimate the benefits of IESs because they fail to account for energy market adjustments. This paper systematically studies the limitations of the prevailing price-taker assumption for TEA and optimization of hybrid energy systems. As an illustrative case study, we retrofit an existing wind farm in the RTS-GMLC test system (which loosely mimics the Southwest U.S.) with battery energy storage to form an IES. We show that the standard price-taker model overestimates the electricity revenue and the net present value (NPV) of the IES up to 178% and 30.4%, respectively, compared to our more rigorous multiscale optimization. These differences arise because introducing storage creates a more flexible resource that impacts the larger wholesale electricity market. Moreover, this work highlights the impact of the IES has on the market via various strategic bidding, and underscores the importance of moving beyond price-taker for optimal storage sizing and TEA of IESs. We conclude by discussing opportunities to generalize the proposed framework to other IESs, and highlight emerging research questions regarding the complex interactions between IESs and markets.

25 ENERGY STORAGE↗

Next Generation of Renewable Electricity Policy: How Rapid Change is Breaking Down Conventional Policy Categories

A number of policies have been used historically in order to stimulate the growth of the renewable electricity sector. This paper examines four of these policy instruments: competitive tendering, sometimes called renewable electricity auctions, feed-in tariffs, net metering and net billing, and tradable renewable energy certificates. In recent years, however, a number of changes to both market circumstances and to policy priorities have resulted in numerous policy innovations, including the emergence of policy hybrids. With no common language for these evolving policy mechanisms, policymakers have generally continued to use the same traditional policy labels, occasionally generating confusion as many of these new policies no longer look, or act, like their traditional predecessors. In reviewing these changes, this paper makes two separate but related claims: first, policy labels themselves are breaking down and evolving. As a result, policy comparisons that rely on the conventional labels may no longer be appropriate, or advisable. Second, as policymakers continue to adapt, we are in effect witnessing the emergence of the next generation of renewable electricity policies, a change that could have significant impacts on investment, as well as on market growth in both developed and developing countries.

24 POWER TRANSMISSION AND DISTRIBUTION↗

County-level Estimates for Carbon Distribution in U.S. Croplands, 1990-2005

Net Primary Productivity (NPP) for croplands can be estimated using a statistical method that includes factors for dry weight, harvest indices, and root:shoot ratios multiplied by yield data from the National Agricultural Statistics Service (NASS). This method has been documented and published by Prince et al. (2001), Hicke and Lobell (2004), and Hicke et al. (2004). We expanded this method by including factors for more crops and by using an estimated carbon content of 0.45 for agricultural crops to estimate (a) total net carbon uptake, (b) carbon in aboveground biomass, (c) carbon in belowground biomass, (d) carbon harvested and transported off site, and (e) the amount of carbon remaining on the surface following harvest. These five variables are included with their respective Federal Information Processing Standards (FIPS) codes for all counties in the contiguous U.S. from 1990-2005. A mean harvest efficiency of 0.95 was assumed across all crops. Total cropland NPP for the U.S. ranges from 378-527 Tg C yr-1 within years 1990-2005, and total carbon harvested and removed ranges from 161-228 Tg C yr-1 within years 1990-2005.For access to the data files, click this link to the CDIAC data transition website: http://cdiac.ess-dive.lbl.gov/carbonmanagement/cropcarbon/

54 ENVIRONMENTAL SCIENCES↗

NexusHaus: Solar Decathlon House

The University of Texas at Austin and The Technical University of Munich 2015 Solar Decathlon house is called Nexushaus because it combines UT Austin and TUM students in an affordable modular residential green building in the context of Austin, Texas, based on shape forming principles found in nature that demonstrates transformative technologies in Zero Net Energy, Zero Net Water and Carbon Neutrality. To meet the needs of the competition, a portable modular design has been developed with an assembly that enables ease of installation and both quantitative and qualitative performance in the design. The prefabricated house sits lightly on the land and forms the superstructure for photovoltaic technologies, rainwater collection, aquaculture and permaculture gardening and indoor/outdoor living. The ultimate goal of Nexushaus is to serve as a potential prototype for a next-generation modular home that could be reproduced in mass in an assembly plant in Austin.

solar decathlon, zero net energy, zero net water, ↗

“Top-Down” Li Deposition Pathway Enabled by an Asymmetric Design for Li Composite Electrode

Designing Li composite electrodes with host frameworks for accommodating Li metal has been considered to be an effective approach to suppress Li dendrites. Herein, an asymmetric design of a Mo net/Li metal film (MLF) composite electrode is developed by an inverted thermal infusion method. The asymmetric MLF electrode has a dense oxide passivated layer on the top side, a porous Mo net matrix on the back side, and active Li layer in between. The back side has a larger specific area and higher electric field than the top side, which contacts with the separator upon cycling, triggering the preferred Li deposition and stripping of the porous back side of the electrode far from the separator. The surface passivation layer on the top side of the electrode as an artificial solid electrolyte interphase ensures the stable contact with the electrolyte and separator. Meanwhile, the porous structure of the supporting Mo net provides enough space for accommodating the volume change during Li deposition and stripping. This asymmetry design enables a unique “top down” growth pathway for Li deposition in the MLF electrode, suppressing the dendrite growth effectively. In conclusion, the design strategy provides a new direction for high-energy dendrite-free Li metal anodes.

25 ENERGY STORAGE↗

Carbon‐negative hydrogen from ethanol via catalytic oxidative reforming

Abstract This study evaluated a commercial technology for producing low‐ or negative‐carbon hydrogen through ethanol catalytic oxidative reforming, focusing on the life cycle greenhouse gas emissions, or carbon intensity (CI). Various scenarios were analyzed: (a) comparing corn ethanol (first‐generation or Gen1 ethanol) and cellulosic ethanol (second‐generation or Gen2 ethanol) as feedstocks; (b) assessing carbon capture and sequestration (CCS) for CO 2 from upstream fermentation; and (c) evaluating oxygen sourcing via air separation units vs. on‐site or off‐site water electrolysis using a proton exchange membrane. Findings indicate that the CI for hydrogen production using Gen2 ethanol from corn stover is lower than that of Gen1 corn ethanol. Additionally, using proton exchange membrane‐generated oxygen results in a lower CI than air separation unit‐generated oxygen, regardless of the sourcing method. Implementing CCS for the hydrogen production plant's evolved CO 2 is essential for achieving a net‐negative CI for hydrogen from Gen1 ethanol. All examined scenarios, including both ethanol generations, oxygen sources, and CCS applications, demonstrated a net‐negative carbon intensity, surpassing the life cycle greenhouse gas emissions threshold of 0.45 kg CO 2 e/kg to enable policy credits as outlined in the Inflation Reduction Act §45V. In comparison, the CI for hydrogen from steam methane reforming stands at 3.4 kg CO 2 e/kg with CCS and 9.4 kg CO 2 e/kg without CCS.

08 HYDROGEN↗

Variability in large-scale wind power generation: Variability in large-scale wind power generation

The paper demonstrates the characteristics of wind power variability and net load variability in multiple power systems based on real data from multiple years. Demonstrated characteristics include probability distribution for different ramp durations, seasonal and diurnal variability and low net load events. The comparison shows regions with low variability (Sweden, Spain and Germany), medium variability (Portugal, Ireland, Finland and Denmark) and regions with higher variability (Quebec, Bonneville Power Administration and Electric Reliability Council of Texas in North America; Gansu, Jilin and Liaoning in China; and Norway and offshore wind power in Denmark). For regions with low variability, the maximum 1 h wind ramps are below 10% of nominal capacity, and for regions with high variability, they may be close to 30%. Wind power variability is mainly explained by the extent of geographical spread, but also higher capacity factor causes higher variability. It was also shown how wind power ramps are autocorrelated and dependent on the operating output level. When wind power was concentrated in smaller area, there were outliers with high changes in wind output, which were not present in large areas with well-dispersed wind power.

17 WIND ENERGY↗

Reticular exploration of uranium-based metal—organic frameworks with hexacarboxylate building units

We report that the rational reticular design of metal–organic frameworks (MOFs) from building units of known geometries is essential for enriching the diversity of MOF structures. Unexpected and intriguing structures, however, can also arise from subtle changes in the rigidity/length of organic linkers and/or synthetic conditions. Herein, we report three uranium-based MOF structures—i.e., NU-135X (X = 0, 1, 2)—synthesized from trigonal planar uranyl nodes and triptycene-based hexacarboxylate ligands with variable arm lengths. A new chiral 3,6-connected nuc net was observed in NU-1350, while the extended versions of the ligand led to 3-fold catenated MOFs (NU-1351 and NU-1352) with rare 3,6-connected cml-c3 nets. Lastly, the differences in the topology of NU-1350 and NU-1351/NU-1352 could be attributed to the slight distortions of the shorter linker in the former from the ideal trigonal prism geometry to an octahedral geometry when coordinated to the trigonal planar uranyl nodes.

3,6-connected net↗

Optimal Gas-Electric Energy System Decarbonization Planning

As energy utilities implement climate change mitigation policies, system planners require strategies for achieving affordable emissions reductions. Coordinated planning of electric power and natural gas systems will allow synergistic investments to address cross-sector operational constraints, competing uses for net-zero emissions fuels, and shifts in energy demands across energy carriers. In this study, we develop a novel optimization program that finds the cost-minimizing mix of infrastructure expansion or reduction across gas and electric systems to satisfy sector-specific emissions constraints. Alongside energy supply resources, our framework allows for central-planning of end-use equipment stocks to allow switching between gas and electric appliances upon failure or premature replacement. The proposed model is used to simulate case study scenarios for a benchmark 24-pipe gas network coupled to a 24-node power system test network. We find that electrification of greater than 80% of core gas demands is a component of the least-cost solution for modeled energy systems. Despite this substitution, the gas system is maintained to service difficult-to-electrify customers and to deliver net-zero emissions gas to electricity generators in times of peak electricity demand. Restricting electrification of gas appliances increases reliance on power- to-gas technologies and increases annual costs by 15% in 2040. Neglecting constraints on pipeline blending of hydrogen can produce a misleading result that relies on hydrogen blend fractions of greater than 50%. In all cases, we find the average costs of delivered gas increase nearly 5-fold across the decarbonization transition, highlighting the importance of future work investigating cost-allocation strategies for ensuring an equitable energy transition.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗

Comparing ecosystem and soil respiration: Review and key challenges of tower-based and soil measurements

The net ecosystem exchange (NEE) is the difference between ecosystem CO2 assimilation and CO2 losses to the atmosphere. Ecosystem respiration (Reco), the efflux of CO2 from the ecosystem to the atmosphere, includes the soil-to-atmosphere carbon flux (i.e., soil respiration; Rsoil) and aboveground plant respiration. Therefore, Rsoil is a fraction of Reco and by definition has to be smaller than Reco at annual, seasonal and daily scales. However, several studies estimating Reco with the eddy covariance technique and measuring Rsoil within the footprint of the tower have reported higher Rsoil than Reco at different time scales. Here, we compare four different and contrasting ecosystems (from forest to grasslands, and from boreal to semiarid) to study whether, and under what conditions, measurements of Reco are lower than Rsoil. In general, both fluxes showed similar temporal patterns, but Reco was not consistently higher than Rsoil from daily to annual scales across sites. We identified several issues that apply for measuring NEE and measuring/upscaling Rsoil that could result in an underestimation of Reco and/or an overestimation of Rsoil. These issues are discussed based on (a) nighttime measurements of NEE, (b) Rsoil measurements, and (c) the interpretation of the functional relationships of these fluxes with temperature (i.e., Q10). We highlight that there is still a need for better integration of Rsoil with eddy covariance measurements to address challenges related to spatial and temporal variability of Reco and Rsoil.

Barba, Josep↗

The surface-atmosphere exchange of carbon dioxide in tropical rainforests: Sensitivity to environmental drivers and flux measurement methodology

Tropical rainforests play a central role in the Earth system by regulating climate, maintaining biodiversity, and sequestering carbon. They are under threat by direct anthropogenic impacts like deforestation and the indirect anthropogenic impacts of climate change. A synthesis of the factors that determine the net ecosystem exchange of carbon dioxide (NEE) at the site scale across different forests in the tropical rainforest biome has not been undertaken to date. Here, we study NEE and its components, gross ecosystem productivity (GEP) and ecosystem respiration (RE), across thirteen natural and managed forests within the tropical rainforest biome with 63 total site-years of eddy covariance data. Our results reveal that the five ecosystems with the largest annual gross carbon uptake by photosynthesis (i.e. GEP > 3000 g C m -2 y -1 ) have the lowest net carbon uptake – or even carbon losses – versus other study ecosystems because RE is of a similar magnitude. Sites that provided subcanopy CO 2 storage observations had higher average magnitudes of GEP and RE and lower average magnitudes of NEE, highlighting the importance of measurement methodology for understanding carbon dynamics in ecosystems with characteristically tall and dense vegetation. A path analysis revealed that vapor pressure deficit (VPD) played a greater role than soil moisture or air temperature in constraining GEP under light saturated conditions across most study sites, but to differing degrees from -0.31 to -0.87 μmol CO 2 m -2 s -1 hPa -1 . Climate projections from 13 general circulation models (CMIP5) under the representative concentration pathway that generates 8.5 W m -2 of radiative forcing suggest that many current tropical rainforest sites on the lower end of the current temperature range are likely to reach a climate space similar to present-day warmer sites by the year 2050, warmer sites will reach a climate not currently experienced, and all forests are likely to experience higher VPD. Results demonstrate the need to quantify if and how mature tropical trees acclimate to heat and water stress, and to further develop flux-partitioning and gap-filling algorithms for defensible estimates of carbon exchange in tropical rainforests.

54 ENVIRONMENTAL SCIENCES↗

Cold spray technology in nuclear energy applications: A review of recent advances

Cold spray technology is a promising solid-state, powder-based deposition methods for fabrication of coatings, near-net-shape manufacturing, and component repair. In recent years, this technology has been investigated for many applications in the nuclear energy sector. For example, it has been explored for the deposition of coatings of corrosion and oxidation materials on zirconium-alloys fuel claddings in light water reactors (LWR) for achieving more accident-tolerant fuel (ATF) cladding. Other examples of its use for nuclear energy applications include coatings for enhancements in wear resistance and heat transfer, near-net shape manufacturing of next-generation fuel claddings of oxide dispersion-strengthened (ODS) steels, and for mitigation and repair of potential chloride induced stress corrosion cracking in used fuel storage canister systems. This work reviews published literature on the application of cold spray process for nuclear energy applications, while pointing to gaps that have yet to be addressed.

36 MATERIALS SCIENCE↗

Optimal deployment of thermal energy storage under diverse economic and climate conditions

This paper presents an investigation of the economic benefit of thermal energy storage (TES) for cooling, across a range of economic and climate conditions. Chilled water TES systems are simulated for a large office building in four distinct locations, Miami in the U.S.; Lisbon, Portugal; Shanghai, China; and Mumbai, India. Optimal system size and operating schedules are determined using the optimization model DER-CAM, such that total cost, including electricity and amortized capital costs are minimized. The economic impacts of each optimized TES system is then compared to systems sized using a simple heuristic method, which bases system size as fraction (50percent and 100percent) of total on-peak summer cooling loads. Results indicate that TES systems of all sizes can be effective in reducing annual electricity costs (5percent-15percent) and peak electricity consumption (13percent-33percent). The investigation also indentifies a number of criteria which drive TES investment, including low capital costs, electricity tariffs with high power demand charges and prolonged cooling seasons. In locations where these drivers clearly exist, the heuristically sized systems capture much of the value of optimally sized systems; between 60percent and 100percent in terms of net present value. However, in instances where these drivers are less pronounced, the heuristic tends to oversize systems, and optimization becomes crucial to ensure economically beneficial deployment of TES, increasing the net present value of heuristically sized systems by as much as 10 times in some instances.

25 ENERGY STORAGE↗

Evaluation of methods and improvement of predictions for specification properties of petroleum-based and alternative aviation fuels

To support our research and process modeling for liquid fuels, including blends, from petroleum and synthetic sources such as from biomass intermediates, we evaluated composition-based prediction methods and improved predictions for five key specification properties of petroleum-based and alternative aviation fuels, namely distillation temperatures (10 % distilled, t 10 , and final boiling point, t FBP ), density, flash point, net heat of combustion, and freezing point. The types of fuels included were petroleum-based jet fuels, jet-fuel surrogate mixtures, synthetic blending components obtained from different sources, and blends of Jet A with many synthetic blending components. Expanded datasets to update associated parameters allowed significant improvements for one of the prediction methods used in earlier work, namely the Modified Weighted Average method published initially by Shi et al. By considering the importance of lighter compounds for flash points and heavier compounds for freezing points, the revised Modified Weighted Average method was further improved. For liquid density, the revised Modified Weighted Average method gave the best overall results. The revised Modified Weighted Average method, the American Society for Testing and Materials D7215 method, and the D7215 method modified by another group gave comparable results for flash point, while the revised Modified Weighted Average and D3338 methods gave the best results for net heat of combustion. Freezing point was well predicted using the revised Modified Weighted Average method and showed the most significant improvements over current predictions. Distillation temperature t 10 was not well predicted, while t FBP was predicted with a mean absolute error comparable to experimental reproducibility.

09 BIOMASS FUELS↗

Idaho national laboratory to demonstrate collaboration first versus competition to accelerate achieving a secure clean energy future by 2031

Idaho National Laboratory (INL) announced at COP27 it would reach net zero greenhouse gas (GHG) emissions by 2031. As a Nuclear, Energy and Environment, and National Homeland Security laboratory, the predominant solution to closing the clean energy gap will include nuclear as a safe, clean, reliable and affordable electricity source with the additional benefit of producing heat and hydrogen to fuel INL’s large transportation fleet. INL’s collaboration first vs. competition is essential to the program’s success. The focused actions in INL’s Nuclear Roadmap include: Infrastructure, Licensing/Regulatory, Financial, Time to Market, Fuel Cycle and Public Confidence/Communications. The roadmap also includes nuclear technology innovations and creative partnerships with utility providers, regulators, businesses, community members, and Indigenous Peoples to accelerate deployment of advanced reactors. Through development of the Net-Zero Nuclear Roadmap, INL will offer a model to provide safe and secure energy for the nation and the world by: (1) establishing the necessary infrastructure on its 890-square mile site to support demonstration, (2) showing proven pathways through the licensing and regulation process, (3) partnering with utilities to ensure commercial application, and (4) collaborating with industry to site new technologies.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗