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Potential to capture 70% of feedstock carbon while >50% of feedstock lower heating value is converted to biofuel and coproducts.
Significance The electrocatalytic conversion of CO 2 to value-added products, especially valuable multicarbon products, is a pathway toward sustainable formation of chemicals and fuels typically derived from fossil fuels, while mitigating CO 2 emissions. Fundamental understanding and development of more efficient catalysts for this reaction require deep investigation into structures with high intrinsic activity, which are limited at present. This work comprehensively investigates a dynamic copper nanoparticle ensemble catalyst that significantly improves intrinsic activity of copper for multicarbon formation. Through concerted ex situ and in situ characterization techniques, it illustrates an electrochemically induced fusion of copper nanoparticles that result in a catalytically active disordered structure, motivating closer study of disordered metal nanostructures for C–C coupling electrocatalysis.
Using renewable electricity to produce hydrogen fuel reduces reliance on fossil fuels. Proton exchange membrane water electrolyzers (PEMWEs) are the highest-performing commercialized technology. These devices split water into oxygen gas and hydrogen ions (protons) at the anode. The protons then migrate through an ion-conducting polymer membrane (ionomer) to be reduced to hydrogen gas at the cathode. Further, the anode reaction’s harsh environment requires the use of precious-metal catalysts, such as iridium oxide (IrO x ). Given the expense and scarcity, the design of electrodes that minimize the use of precious metals without compromising the requisite stability and activity is desired for large-scale hydrogen production. On page 791 of this issue, Shi et al. report that anchoring IrO x catalysts onto porous cerium-oxide (CeO x ) supports maintains performance even with much reduced precious metal use.
This study examines the system-level costs and benefits of increased renewable energy deployment in the Railbelt grid, in the context of a proposed 80% renewable portfolio standard (RPS). This work studies the period from 2024 to 2040 and uses a model that simulates the planning, evolution, and operation of the power system to identify the mix of resources that maintains system reliability at the lowest electricity system cost over the period of analysis. The model tracks several reliability metrics, including the ability to serve demand during all hours of the year, even when normal power system failures occur. The model includes several measures (and associated costs) to address the variable output of renewable resources, including additional operating reserves, fuel storage, cycling of fossil plants, and additional equipment needed to maintain system stability. The Reference (least-cost) scenario results in substantial deployment of renewable energy and cost savings, reaching about 76% of Railbelt generation derived from renewables in 2040. Annual savings average about $105 M/year from 2030 to 2040. About 50% of this generation is from wind by 2040. Enforcing an 80% RPS results in about a 2% cumulative reduction in net savings. Demand is met in all scenarios, relying heavily on use of existing hydropower and fossil-fueled generators during periods of low renewable output. Meeting the increase in variability will require substantial changes in how the system is operated, with inverter-based resources providing nearly 100% of electricity during some periods.
The search for a sustainable, alternative fuel source to replace fossil fuels has led to an increased interest in hydrogen fuel. This combustible gas is not only clean-burning but can readily be produced via the hydrolysis of sodium borohydride. The main drawback of this reaction is that the reaction occurs relatively slowly and requires a catalyst to improve efficiency. This study explored a novel composite material made by combining gold nanoparticles and fused graphene-like materials (AuFGLM) as a catalyst for generating hydrogen via sodium borohydride. The novel fused graphene-like material (FGLM) was made with a sustainable dextrose solution and by using a pressure-processing method. Imaging techniques showed that FGLM appears to be an effective support template for nanoparticles. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and Raman spectroscopy were used to characterize and determine the size, shape, and structure of nanoparticles and composites. The TEM study characterized the fused carbon backbone as it began to take on a rounder shape. The TEM images also revealed that the average diameter of the gold nanoparticle was roughly 23 nm. The FTIR study confirmed O-H, C-C, and C=O as functional groups in the materials. The EDS analysis showed that the composite contained approximately 6.3% gold by weight. The crystal structures of FGLM and AuFGLM were identified via P-XRD analysis. Various reaction conditions were used to test the catalytic ability of AuFGLM, including various solution pHs, temperatures, and doses of NaBH 4 . It was observed that optimal reaction conditions included high temperature, an acidic solution pH, and a higher dose of NaBH 4 . The activation energy of the reaction was determined to be 45.5 kJ mol -1 , and it was found that the catalyst could be used multiple times in a row with an increased volume of hydrogen produced in ensuing trials. The activation energy of this novel catalyst is competitive compared to similar catalysts and its ability to produce hydrogen over multiple uses makes the material an exciting choice for catalyzing the hydrolysis of NaBH 4 for use as a hydrogen fuel source.
Biomass feedstocks can be used to produce low carbon-intensity chemicals and liquid fuels by displacing fossil-fuel sources. Pyrolysis is the thermal decomposition of biomass in the absence of oxygen and can be used to produce crude biofuels. A typical feeding mechanism for pyrolysis reactors is by lock hopper followed by a horizontal auger feeder. Particle agglomeration and plugging of the auger screw are regularly occurring phenomena that is detrimental to the process since it results in the need for periodic inspection and cleaning. The underlying mechanisms leading to agglomeration and plugging are unclear, but a working hypothesis is that heat from the reactor raises the temperature of the biomass in the feeder to the point at which preliminary decomposition reactions occur and produce "sticky" products. Using principles of heat and mass transfer, we derived one-dimensional differential equations for heat flow from the pyrolysis reactor through the auger feeder. Temperature profiles were solved from the system of one-dimensional differential equations using the shooting method. Subsequently, we used the temperature profiles as a one-way coupling to a reaction model for the biomass in the feeder. Kinetic models were adopted from the literature and used to predict the formation of intermediates, products, char, extractives, and metaplastics as well as phase changes along the auger feeder. Species were identified that correlated with softening of the biomass, causing it to become sticky and plug the feeder. We will discuss the details of this work, our findings, and the direction of future work that includes fully coupled transport and reaction-kinetics simulations.
This project develops tools to evaluate fossil energy within the hydrogen economy. In particular, the project seeks to explore the Carbon-Water-Energy Nexus and develop adaptive evaluation tools. The primary goal of this project was to evaluate fossil-based hydrogen production methods with an emphasis on their sustainability, particularly with respect to carbon emissions and water use. The overall technical objectives that guided this evaluation consisted of 1) technology assessment, which sought to establish a comprehensive baseline of existing and emerging technologies for the generation, transportation, storage, and end use of hydrogen derived from fossil fuels, 2) carbon footprint analysis through quantification and analysis of carbon emissions associated with these hydrogen technologies, and identification of novel strategies and technologies that can effectively mitigate the carbon footprint, 3) water intensity assessment by evaluating the water needs (water-energy nexus) associated with different fossil fuel-based hydrogen technologies and proposing strategies to reduce water use, thus ensuring sustainable resource management, and 4) review of regulatory, policy and economic trends were examined to provide an overview of the factors influencing the adoption and integration of fossil fuel-derived hydrogen technologies into current energy markets. Beyond the technical outcomes, this project contributed to 5) education and workforce development through targeted training and educational opportunities for engineering students, preparing the next generation of professionals with technical, economic, and regulatory expertise in the hydrogen economy. Ultimately, this effort was intended to train the future workforce to provide useful insights to policymakers, industry stakeholders, and the broader energy community to facilitate informed decisions and responsible development within the hydrogen economy.
Oxy-combustion can enable efficient CO2 capture from fossil fuel power plants in combined cycle systems; however, air separation is expensive. In order to directly utilize the high gas temperatures associated with oxy-combustion and offset any oxygen separation penalties, a magnetohydrodynamic (MHD) generator has been proposed as a plant topping cycle. Accurately predicting the electrical conductivity of combustion products with the addition of potassium “seed” compound is necessary to evaluate the performance of this modern approach to MHD. In order to make these predictions, improved species collisional cross-section data (momentum transfer cross-section, MTCS) are needed at relevant conditions. A gas electrical conductivity model for use in open-cycle MHD power generation applications is presented, which makes use of updated MTCS data not represented in previous legacy publications. Based on the results of a detailed review and analysis of currently available MTCS data relevant to open-cycle MHD combustion systems, recommendations have been provided for relevant species and a gas temperature range of 1500-3500 K (~0.13-0.3 eV electron energy). Model predictions utilizing updated MTCS data are validated against limited experimental data found in literature for oxy-combustion with potassium seed compound. Model results are presented from a parametric study, which show the effect of combustion conditions and seeding on ionization processes and gas electrical conductivity, highlighting differences between modern oxy-combustion MHD systems and legacy approaches implementing air-fired combustion and high levels of preheat.
GTI Energy partnered with Praxair Inc., a subsidiary of Linde PLC (Praxair), the Center for Electromechanics at the University of Texas at Austin (CEM), Entergy Corporation (Entergy), Quanta Services (Quanta) and Mitsubishi Heavy Industries (MHI) to perform a feasibility study that determines the economic and technical feasibility of low-carbon hydrogen energy storage integrated with a site-specific fossil fuel asset to decarbonize electricity production using the Integrated Hydrogen Energy Storage System (IHESS). The proposed IHESS concept is novel, as it sought to leverage the existing natural gas infrastructure, hydrogen production and pipelines, existing underground hydrogen storage system and power plants in the Gulf Coast region to reduce carbon emissions and generate lowcarbon electricity. This study has shown that IHESS has a promising commercial outlook as the concept leverages existing natural gas infrastructure assets and hydrogen production and storage that are unique to the Texas gulf coast region. A key hurdle with hydrogen supply and transportation has been capital investment. By storing hydrogen in underground storage and delivering it as a fuel source during peak demand using the existing infrastructure minimizes the capital investment. Regional petrochemical producers who are actively seeking opportunities to reduce costs and lower emissions should find the IHESS concept very appealing.
Fossil fuel combustion processes generate CO2, a greenhouse gas of considerable concern. To reduce this emission, the National Energy Technology Laboratory (NETL) is evaluating alternative combustion approaches, including chemical looping combustion (CLC). This technique generates relatively pure CO2, suitable for subsequent capture and storage. CLC uses oxygen-carrier particles (OCPs) such as iron oxides, copper oxides, calcium sulfates, etc. to provide oxygen for the combustion process. Optimization of the overall combustion process requires knowledge of the oxidation state (e.g., content of Fe2O3 vs. Fe3O4) of the OCPs during the different stages of the CLC process. Unfortunately, the ability to make on-line measurements of the oxidation state of OCPs in harsh environments is lacking and new sensors need to be developed. We are evaluating non-contact, stand-off Raman spectroscopy to determine the relative concentrations of the oxidized and reduced forms of OCPs at temperatures between 800 °C and 1000 °C, and pressures of about 10 atm. Using cw and pulsed Raman spectroscopy, in combination with a pressurized high-temperature sample chamber, we have optimized the operating parameters such as laser wavelength, laser intensity, collection optic design, focal spot size, etc. and measured Raman spectra of various OCP materials at high temperatures. To extract from the Raman spectra relevant information such as the concentration ratio of a material in different oxidation states, the measured data needs to be processed, and statistical modeling and multivariate calibration need to be performed.
Larger vehicles, such as sports utility vehicles, consume more energy than cars. Their increasing popularity runs contrary to the goal of fuel economy regulations to reduce fossil fuel consumption and greenhouse gas emissions and can be explained by consumer preference and lower regulation stringency, which is due to footprint, truck classification, and the omission of heterogenous lifetime vehicle distance traveled among vehicle classes. This study shows that, for both the US and China, large vehicles travel more, last longer, and are owned by higher income consumers. This means large vehicles and their high-income owners use more fuel and emit more pollutants than represented by current policy and thus raises both policy effectiveness and energy equity concerns. We propose and estimate Sales Adjustment Factors that weigh fuel economy standards based on vehicle lifetime usage and demonstrate the resultant significant improvements in the effectiveness and equity of fuel economy regulations.
Currently, hydrogen fuel is derived mainly from fossil fuels, but there is an increasing interest in clean and sustainable technologies for hydrogen production. In this context, the ability of some photosynthetic microorganisms, particularly cyanobacteria and microalgae, to produce hydrogen is a promising alternative for renewable, clean-energy production. Among a diverse array of photosynthetic microorganisms able to produce hydrogen, the green algae Chlamydomonas reinhardtii is the model organism widely used to study hydrogen production. Furthermore, the well-known fact that acetate-containing medium enhances hydrogen production in this algae, little is known about the precise role of acetate during this process.
The debate continues on the magnitude and validity of climate change caused by human activities. However, there is no debate about the need to make buildings, modes of transportation, factories, and homes as energy efficient as possible. Given that climate change could occur with the wasteful use of fossil fuel and the fact that fossil energy costs could and will swing wildly, it is imperative that every effort be made to utilize energy sources to their fullest. Hybrid energy systems (HES) are two or more separate energy producers used together to produce energy commodities. The HES this report focuses on is the use of nuclear reactor waste heat as a source of further energy utilization. Nuclear reactors use a fluid to cool the core and produce the steam needed for the production of electricity. Traditionally this steam, or coolant, is used to convert the energy then cooled elsewhere. The heat is released into the environment without being used further. By adding technologies to nuclear reactors to use the wasted heat, a system can be developed to make more than just electricity and allow for loading following capabilities.
Increasing the production and use of biofuels is a national objective for renewable, cleaner energy. A primary objective of the Department of Energy’s Bioenergy Technologies Office (BETO) Feedstock-Conversion Interface Consortium (FCIC) is to address the operational, safety, throughput, and yield of bio-refineries to revolutionize biomass processing with the goal to make bio-derived fuels cost-competitive with fossil fuels. One of the main hurdles is increasing the operational reliability of the bio-refineries. Bio-refineries convert the biomass, such as corn stover, into ethanol. Corn stover is composed of the non-edible stalks, leaves, cobs, and husks left over from harvesting. This material is known for having poor processing properties for bulk solids handling and transport. These properties, such as moisture content, cause costly system plugging and downtime at bio-refineries which limit biofuel from being cost-competitive with diesel and gasoline fuels.
Renewable fuels are needed to replace fossil fuels in the immediate future. Lignocellulosic bioenergy crops provide a renewable alternative that sequesters atmospheric carbon. To prevent displacement of food crops, it would be advantageous to grow biofuel crops on marginal lands. These lands will likely face more frequent and extreme drought conditions than conventional agricultural land, so it is crucial to see how proposed bioenergy crops fare under these conditions and how that may affect lignocellulosic biomass composition and saccharification properties. We found that while drought impacts the plant cell wall of Sorghum bicolor differently according to tissue and timing of drought induction, drought-induced cell wall compositional modifications are relatively minor and produce no negative effect on biomass conversion. This contrasts with the cell wall-related transcriptome, which had a varied range of highly variable genes (HVGs) within four cell wall-related GO categories, depending on the tissues surveyed and time of drought induction. Further, many HVGs had expression changes in which putative impacts were not seen in the physical cell wall or which were in opposition to their putative impacts. Interestingly, most pre-flowering drought-induced cell wall changes occurred in the leaf, with matrix and lignin compositional changes that did not persist after recovery from drought. Most measurable physical post-flowering cell wall changes occurred in the root, affecting mainly polysaccharide composition and cross-linking. This study couples transcriptomics to cell wall chemical analyses of a C4 grass experiencing progressive and differing drought stresses in the field. As such, we can analyze the cell wall-specific response to agriculturally relevant drought stresses on the transcriptomic level and see whether those changes translate to compositional or biomass conversion differences. Our results bolster the conclusion that drought stress does not substantially affect the cell wall composition of specific aerial and subterranean biomass nor impede enzymatic hydrolysis of leaf biomass, a positive result for biorefinery processes. Coupled with previously reported results on the root microbiome and rhizosphere and whole transcriptome analyses of this study, we can formulate and test hypotheses on individual gene candidates’ function in mediating drought stress in the grass cell wall, as demonstrated in sorghum.
Solid oxide fuel cells (SOFCs) have tremendous commercial potential because of their high efficiency, high energy density, and flexible fuel capability (ability to use fossil fuels). The drive for high-power-utilizing, ultrathin electrolytes (less than 10 microns), has placed an increased demand on the anode to provide structural support, yet allow sufficient fuel entry for sustained power generation. Concentration polarization, a condition where the fuel demand exceeds the supply, is evident in all commercial-based anode-supported cells, and it presents a significant roadblock to SOFC commercialization.
Thermionic (TI) power conversion is a promising technology first investigated for power conversion in the 1960's, and of renewed interest due to modern advances in nanotechnology, MEMS, materials and manufacturing. Benefits include high conversion efficiency (20%), static operation with no moving parts and potential for high reliability, greatly reduced plant complexity, and the potential for reduced development costs. Thermionic emission, credited to Edison in 1880, forms the basis of vacuum tubes and much of 20th century electronics. Heat can be converted into electricity when electrons emitted from a hot surface are collected across a small gap. For example, two "small" (6 kWe) Thermionic Space Reactors were flown by the USSR in 1987-88 for ocean radar reconnaissance. Higher powered Nuclear-Thermionic power systems driving Electric Propulsion (Q-thruster, VASIMR, etc.) may offer the breakthrough necessary for human Mars missions of < 1 yr round trip. Power generation on Earth could benefit from simpler, moe economical nuclear plants, and "topping" of more fuel and emission efficient fossil-fuel plants.
Over the past 20 years, a hydrogen economy has often been proposed by the media, as well as by scientists, as a means to mitigate the environmental problems caused by the use of fossil fuels.