Browsing by Subject "Hydrogen"

Now showing 1 - 18 of 18

A systematic study of basis set superposition error in the interaction energy of two hydrogen molecules
(Texas Tech University, 1998-12) Chang, Daniel Ta-Jen
Not available
Alignment effects of hydrogen reflection by Si(100)
(2015-08) Stevens, Robert Gardiner; Sitz, Greg Orman; Fink, Manfred; Downer, Michael; Keto, John; Henkelman, Graeme
Previous scattering experiments have shown a dependence of reflectivity on the alignment of the angular momentum vector of molecular hydrogen incident on a surface of Pd(111), Isakson 2001. In these past experiments orthohydrogen was preferentially aligned relative to the surface by preparing the J=3 state. This J=3 state has multiple values for its magnetic quantum number and therefore there is a distribution in J=3 alignment. Within I will discuss the design of a new laser that can efficiently pump parahydrogen from the J=0 state, which has no distribution in magnetic quantum numbers and therefore the resulting J=2 state can be aligned with much better precision. Evidence suggests (Isakson, 2001) that the perpendicular alignment of the angular momentum vector with respect to the surface (helicopter-type motion) was less reflective than the parallel alignment (cartwheeler-type motion) for orthohydrogen when interacting with Pd(111). Within a study of the preservation of these alignments, both helicopter and cartwheeler, for aligned J=3 initial states will be attempted as they reflect off of the unreactive Si(100) surface. This study will strongly influence future studies, ones off of reactive surfaces such as Pd(111), and dictate if loss of alignment can explain the perceived decreased reflectivity.
Analysis of Enzyme Dynamics in Kynureninase Through Hydrogendeuterium Exchange Mass Spectrometry
(2020-04-14) Murray, Kyle William
Roughly 38.5% of people will be diagnosed with cancer in their lifetime1. Elevated levels of the small molecule, kynurenine, is a feature of the microtumor environment in 58% of all cancers2. Kynurenine promotes immunosuppression and is compounded via an inflammation-directed positive feedback loop. Kynureninase is an enzyme capable of breaking down kynurenine to ultimately restore immune response and dismantle the positive feedback loop. Unfortunately, the human version of this enzyme has low preference for kynurenine, with high selectivity toward the similar 3’-hydroxylated kynurenine. In this dissertation, human kynureninase was compared with a kynurenine-selective bacterial kynureninase homolog. Bacterial kynureninase was compared against the human ortholog using kinetic assays, Molecular Dynamics, and hydrogen-deuterium exchange mass spectrometry. With the knowledge that both enzymes can break down either substrate, we discovered that substrate preference directs ratelimiting steps using pre-steady-state kinetics. Molecular Dynamics complemented experimental data from hydrogen-deuterium exchange mass spectrometry to describe key regions and even residues critical for enzyme catalysis. We identified two critical features required for efficient catalysis. The first is human motif containing residues 305-338. This region contains rigid secondary structure in the human enzyme yet appears flexible in the bacterial homolog which lacks secondary structure. Secondly, kynureninases have a PLP cofactor that coordinates several residues in the active site. One region, an -helix cap, associated with human residues 136-137 contains key helix-helix contacts with residues adjacent to F165. These two regions are what bottlenecks the efficiency of the human enzyme towards kynurenine. Mutated KYNase, which show improved efficiency toward kynurenine demonstrate increased flexibility of the helix-helix contact. Protein engineering efforts led to two varieties of mutated human kynureninase. The first variety (B-Factor kynureninases) was a result of distal mutations resulting in up to an 11-fold increase in kynurenine efficiency. The second variety (bacterialized kynureninases) resulted from directed evolution, generating two versions of human kynureninase that were either 114- or 275-fold more efficient towards kynurenine than the human wildtype. Efficiency was measured in terms of kcat/KM. We discovered that flexibility in the 305-338 was maintained throughout the improved variants. As efficiency towards kynurenine increased, stabilization occurred across all other loops that transversed the active site. Ultimately, we have described wildtype and engineered kynureninases in detail to best understand how catalytic events within enzymes, specifically kynureninase, are sensitive to a wide variety of perturbations which lead to a dramatic increase in efficiency.
Computer simulations of a hydrogen fueled internal combustion engine
(Texas Tech University, 2005-05) Halmari, Jaakko J.; Maxwell, Timothy T.; Parten, Michael E.; Ertas, Atila
Ricardo WAVE was used to simulate the hydrogen internal combustion engine used in Texas Tech University’s FutureTruck Ford Explorer. Initially, a naturally aspirated gasoline engine was simulated, followed by the supercharged hydrogen engine. The objective of these simulations was to maximize power of the hydrogen engine, while minimizing the emissions and fuel consumption. Among the variables which were changed, were the equivalence ratio, compression ratio, throttle opening, camshaft timing, and exhaust size. The simulation results studied included the volumetric efficiency, fuel consumption, as well as NO emissions. Several results were compared to the gasoline baseline model.
Computer simulations of a hydrogen fueled internal combustion engine
(2005-05) Halmari, Jaakko Jalmari; Maxwell, Timothy T.; Parten, Michael E.; Ertas, Atila
Ricardo WAVE was used to simulate the hydrogen internal combustion engine used in Texas Tech University’s FutureTruck Ford Explorer. Initially, a naturally aspirated gasoline engine was simulated, followed by the supercharged hydrogen engine. The objective of these simulations was to maximize power of the hydrogen engine, while minimizing the emissions and fuel consumption. Among the variables which were changed, were the equivalence ratio, compression ratio, throttle opening, camshaft timing, and exhaust size. The simulation results studied included the volumetric efficiency, fuel consumption, as well as NO emissions. Several results were compared to the gasoline baseline model.
Design of an underground compressed hydrogen gas storage
(2010-12) Powell, Tobin Micah; Jablonowski, Christopher J.; Groat, Charles G.
Hydrogen has received significant attention throughout the past decade as the United States focuses on diversifying its energy portfolio to include sources of energy beyond fossil fuels. In a hydrogen economy, the most common use for hydrogen is in fuel cell vehicles. Advancements in on-board storage devices, investment in hydrogen production facilities nation-wide, development of a hydrogen transmission infrastructure, and construction of hydrogen fueling stations are essential to a hydrogen economy. This research proposes a novel underground storage technique to be implemented at a hydrogen fueling station. Three boreholes are drilled into the subsurface, with each borehole consisting of an outer pipe and an inner pipe. Hydrogen gas (H2) is stored in the inner tube, while the outer pipe serves to protect the inner pipe and contain any leaked gas. Three boreholes of varying pressures are necessary to maintain adequate inventory and sufficient pressure while filling vehicles to full tank capacity. The estimated cost for this storage system is $2.58 million. This dollar amount includes drilling and completion costs, steel pipe costs, the cost of a heavy-duty hydrogen compressor, and miscellaneous equipment expenses. Although the proposed design makes use of decades’ worth of experience and technical expertise from the oil and gas industry, there are several challenges—technical, economic, and social—to implementing this storage system. The impact of hydrogen embrittlement and the lack of a hydrogen transmission infrastructure represent the main technical impediments. Borehole H2 storage, as part of a larger hydrogen economy, reveals significant expenses beyond those calculated in the amount above. Costs related to delivering H2 to the filling station, electricity, miscellaneous equipment, and maintenance associated with hydrogen systems must also be considered. Public demand for hydrogen is low for several reasons, and significant misperceptions exist concerning the safety of hydrogen storage. Although the overall life-cycle emissions assessment of hydrogen fuel reveals mediocre results, a hydrogen economy impacts air quality less than current fossil-fuel systems. If and when the U.S. transitions to a hydrogen economy, the borehole storage system described herein is a feasible solution for on-site compressed H2 storage.
Determination of Optimal Process Flowrates and Reactor Design for Autothermal Hydrogen Production in a Heat-Integrated Ceramic Microchannel Network
(2012-07-16) Damodharan, Shalini
The present work aimed at designing a thermally efficient microreactor system coupling methanol steam reforming with methanol combustion for autothermal hydrogen production. A preliminary study was performed by analyzing three prototype reactor configurations to identify the optimal radial distribution pattern upon enhancing the reactor self-insulation. The annular heat integration pattern of Architecture C showed superior performance in providing efficient heat retention to the system with a 50 - 150 degrees C decrease in maximum external-surface temperature. Detailed work was performed using Architecture C configuration to optimize the catalyst placement in the microreactor network, and optimize reforming and combustion flows, using no third coolant line. The optimized combustion and reforming catalyst configuration prevented the hot-spot migration from the reactor midpoint and enabled stable reactor operation at all process flowrates studied. Best results were obtained at high reforming flowrates (1800 sccm) with an increase in combustion flowrate (300 sccm) with the net H2 yield of 53% and thermal efficiency of >80% from methanol with minimal insulation to the heatintegrated microchannel network. The use of the third bank of channels for recuperative heat exchange by four different reactor configurations was explored to further enhance the reactor performance; the maximum overall hydrogen yield was increased to 58% by preheating the reforming stream in the outer 16 heat retention channels. An initial 3-D COMSOL model of the 25-channeled heat-exchanger microreactor was developed to predict the reactor hotspot shape, location, optimum process flowrates and substrate thermal conductivity. This study indicated that low thermal conductivity materials (e.g. ceramics, glass) provides enhanced efficiencies than high conductivity materials (e.g. silicon, stainless steel), by maintaining substantial thermal gradients in the system through minimization of axial heat conduction. Final summary of the study included the determination of system energy density; a gravimetric energy density of 169.34 Wh/kg and a volumetric energy density of 506.02 Wh/l were achieved from brass architectures for 10 hrs operation, which is higher than the energy density of Li-Ion batteries (120 Wh/kg and 350 Wh/l). Overall, this research successfully established the optimal process flowrates and reactor design to enhance the potential of a thermally-efficient heat-exchanger microchannel network for autothermal hydrogen production in portable applications.
Development of hydrogen-mediated carbon-carbon bond formations
(2005) Jang, Hye-Young; Krische, Michael J.
Enhanced Hydrogen Production in Escherichia coli Through Chemical Mutagenesis, Gene Deletion, and Transposon Mutagenesis
(2011-08-08) Garzon Sanabria, Andrea Juliana
We demonstrate that hydrogen production can be increased by random mutagenesis using N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and that hydrogen production can be further increased in the chemically-mutagenized strain by targeted gene deletion and overexpression of genes related to formate metabolism. Chemical mutagenesis of Escherichia coli BW25113 hyaB hybC hycE::kan/pBS(Kan)-HycE to form strain 3/86 resulted in 109 +/- 0.5- fold more hydrogen; 3/86 lacks functional hydrogen uptake hydrogenases 1 and 2, has hydrogenproducing hydrogenase 3 inactivated from the chromosome, and has constitutively active hydrogenase 3 based on expression of the large subunit of hydrogenase 3 from a high copy number plasmid. Deleting fdoG, which encodes formate dehydrogenase O, (that diverts formate from hydrogen), from chemical mutagen 3/86 increased hydrogen production 188 +/- 0.50-fold (relative to the unmutagenized strain), and deletion of hycA, which encodes the repressor of formate hydrogen lyase (FHL), increased hydrogen production 232 +/- 0.50-fold. Deleting both fdoG and hycA increased hydrogen production 257 +/- 0.50-fold, and overexpressing fhlA along with the fdoG hycA mutations increased hydrogen 308 +/- 0.52-fold. Whole-transcriptome analysis of chemical mutagen 3/86 revealed 89 genes were induced and 31 genes were repressed. In an effort to identify chromosomal mutations in chemical mutagen 3/86, we performed comparative genome sequencing and identified two chromosomal loci with mutations in coding regions of ftnA and yebJ; however, neither gene was related to the increased hydrogen production as determined by the close vial (short) hydrogen assay. In addition, transposon mutagenesis, which is one of the most efficient strategies for creating random mutations in the genomic DNA, was performed in two different strains: E. coli BW25113 hyaB hybC hycA fdoG::kan/pCA24N-FhlA and E. coli MG1655 to identify beneficial mutations for hydrogen production. As a result of screening 461 E. coli BW25113 hyaB hybC hycA fdoG::kan/pCA24N-FhlA transformants and 1000 E. coli MG1655 transformants, three interesting mutations have been discovered in E. coli BW25113 hyaB hybC hycA fdoG::kan/pCA24N-FhlA transformants (gpsA, dipZ, glgP) and 1 beneficial mutation in E. coli MG1655 transformants (malT). When any of these genes gpsA, dipZ, or glgP is disrupted by Tn5 insertion, hydrogen production decreases 17, 3 and 8-fold, respectively. Additionally, when malT gene is disrupted by Tn5 insertion, hydrogen increases 3.4-fold.
Flammability Characteristics of Hydrogen and Its Mixtures with Light Hydrocarbons at Atmospheric and Sub-atmospheric Pressures
(2013-07-13) Le, Thuy Minh Hai
Knowledge of flammability limits is essential in the prevention of fire and explosion. There are two limits of flammability, upper flammability limit (UFL) and lower flammability limit (LFL), which define the flammable region of a combustible gas/vapor. This research focuses on the flammability limits of hydrogen and its binary mixtures with light hydrocarbons (methane, ethane, n-butane, and ethylene) at sub-atmospheric pressures. The flammability limits of hydrogen, light hydrocarbons, and binary mixtures of hydrogen and each hydrocarbon were determined experimentally at room temperature (20?C) and initial pressures ranging from 1.0 atm to 0.1 atm. The experiments were conducted in a closed cylindrical stainless steel vessel with upward flame propagation. It was found that the flammable region of hydrogen initially widens when the pressure decreases from 1.0 atm to 0.3 atm, then narrows with the further decrease of pressure. In contrast, the flammable regions of the hydrocarbons narrow when the pressure decreases. For hydrogen and the hydrocarbons, pressure has a much greater impact on the UFLs than on the LFLs. For binary mixtures of hydrogen and the hydrocarbons, the flammable regions of all mixtures widen when the fraction of hydrogen in the mixture increases. When the pressure decreases, the flammable regions of all mixtures narrow. The applications of Le Chatelier?s rule and the Calculated Adiabatic Flame Temperature (CAFT) model to the flammability limits of the mixtures were verified. It was found that Le Chatelier?s rule could predict the flammability limits much better than the CAFT model. The adiabatic flame temperatures (AFTs), an important parameter in the risk assessment of fire and explosion, of hydrogen and the hydrocarbons were also calculated. The influence of sub-atmospheric pressures on the AFTs was investigated. A linear relationship between the AFT and the corresponding flammability limit is derived. Furthermore, the consequence of fire relating to hydrogen and the hydrocarbons is discussed based on the AFTs of the chemicals.
Glow Discharge Enhanced Chemical Reaction: Application in Ammonia Synthesis and Hydrocarbon Gas Cleanup
(2014-06-05) Ming, Pingjia
Two different plasma enhanced processing technologies were investigated in this study: ammonia synthesis from steam and nitrogen, and hydrocarbon gas clean up. Ammonia is a common sanitizer in swimming pool and fish tank, changing the pH of the water, which does not benefit bacteria. Also ammonia is used in various NOx reduction technologies, for example, selective catalytic reduction (SCR) methods have been studied for the cleaning of diesel engine exhaust. A small compact glow discharge was applied to investigate ammonia synthesis from steam and nitrogen. Ammonia was successfully detected via UV-VIS absorbance and through increasing pH value of treated water by product gas. Heavier hydrocarbon C3 to C5 are produced with natural gas, but cannot be used in sensitive energy conversion systems, like solid oxide fuel cell (SOFC). Utilizing small amount of energy to clean up and reform heavier hydrocarbon into synthesis gas is necessary when using hydrocarbon sources which contain heavier hydrocarbons mixture such as EPE (74.8% methane, 8% ethane, 8% ethylene, 2.1% propane and 1.1% Propene). Non-thermal plasmas, due to their unique non-equilibrium characteristics, offer advantages as method of reforming at lower temperature (100-150 ?C) and atmospheric pressure. For an EPE gas mixture, a high conversion and low specific energy cost is desirable. Variation in discharge power density, air and, water addition were tested, in order to find conditions which were energetically feasibility, efficiency and sufficiently reduced the higher hydrocarbon. High conversion efficiency was achieved, in propane and propene, which was more than 90%, without carbon deposition through air addition. For a 1 J/ml power density and 1.08 O2/C ratio condition, a process efficiency of 74% and 54% available output energy was achieved. At the same time, the concentration of ethane, ethylene, propane, propylene, and acetylene were cleaned-up to value of 1.01%, 1.67%, 0.08%, 0.00%, and 0.50%, respectively, less than 20% of their original input amount. Higher power density produced cleaner (less high hydrocarbons) in the products, and were still energetically feasible, but less efficient.
Hydrogen-defect interactions in silicon
(Texas Tech University, 1999-08) Hastings, Jeffrey Lawrence
The vacancy is one of the strongest traps for H is Si, and it was even suggested that Frenkel pairs (vacancy-self-interstitial) can be created by hydrogen.^* Thus, H, V's, and I's interact with the same impurities and with each other, which is bound to have profound implications in situations where they coexist. This is the main motivation for the present work, which presents the results of molecular dynamics (MD) simulations and approximate-ab-initio HF calculations involving V and H. In this paper, I discuss our investigations of the reactions involving (neutral) V's and/or I's with interstitial H, H2 molecules, and with each other. The calculations were performed at various levels of theory, not just because different methods have different strengths and weaknesses, but also because we want to check that our results are independent of the way the host crystal is approximated (periodic supercells or molecular clusters) and the electronic energy calculated (density-functional [DF] or Hartree-Fock [HF]).
Microstructural and Mechanical Property Changes in Ion Irradiated Tunsgten
(2013-04-08) General, Michael
Sustainable fusion power is within reach; however, more research is needed in the field of material science and engineering. One critical component of a fusion reactor is the plasma facing material. Very little literature exists on the sustainability of tungsten as a plasma facing material (PFM). During operation, PFM must withstand harsh conditions with combined effects from high temperature, mechanical stress, irradiation, transmutation, and the production of hydrogen (H) and helium (He) from nuclear reactions. Therefore, this thesis will focus on co-implantation of H and He into tungsten to investigate the mechanical and microstructural material response. For the first part of this study, Molecular Dynamics (MD) was used to qualitatively understand defect migration and mechanical property changes in tungsten. A Brinell hardness test was simulated using MD in tungsten to study the dependence on void size and void density hardness. It was found that hardness changes vary as the square root of the void size and void density. Also the movement of dislocations and its interaction with voids were investigated. For the second part of the study, H and He were co-implanted into tungsten to look at the mechanical and microstructural changes. Hardness changes were measured using a nano-indenter ex-situ on post-irradiated specimen. Results show that the hardness of tungsten after co-implantation is proportional to the square root of the fluence. Additionally, the microstructure of irradiated tungsten samples was investigated by using a Transmission Electron Microscope (TEM). It was observed that the defect microstructure in tungsten, after co-implantation, is quite complex, with a number of intriguing features, such as the presence of the nano-bubbles and dislocation loops. Also it was observed that there was an effect that H has on the nucleation of He nano-bubbles. The results from this work suggest that the effect of co-implanting H and He into tungsten is crucial to fully understand its viability as a PFM.
Molecular-dynamics study of the Staebler-Wronski Effect in hydrogenated amorphous silicon using large supercells
(Texas Tech University, 1997-05) Ha, Byeonqchul
Hydrogenated amorphous silicon is a semiconductor which has many practical device applications. However, it is known that in this material, there is a "Staebler-Wronski (SW) Effect," which is a light-induced degradation. The effort to understand the source of the SW Effect has continued for two decades. Numerous theories and experiments have been published about the SW Effect, but its exact cause is not known. A fundamental problem is to understand the role hydrogen plays in the SW Effect. In this thesis, the molecular dynamics technique is used to study the bond breaking model of the SW Effect and to explore the role hydrogen plays in this effect. Large (224 and 231 atom) supercells, prepared by an ab-initio technique, are used. The molecular dynamics calculations are performed using a semi-empirical total energy functional. This work is an extension of the work of Park and Myles to large supercells.
Muonium defect centers in aluminum nitride and silicon carbide
(Texas Tech University, 2007-05) Bani-Salameh, Hisham Nahar; Lichti, Roger L.; Lamp, Carl D.; Myles, Charles W.; Estreicher, Stefan K.
We report the results of ƒÝSR measurements on Aluminum Nitride (AlN) and Silicon Carbide (SiC). The importance of studying muonium states comes from its analogy to atomic hydrogen making it an excellent source of information on isolated hydrogen impurities in various materials. Neutral muonium exists in AlN to high temperatures, a large hyperfine constant of ~4450 MHz with a small temperature-dependent dipolar contribution indicating weak anisotropy is obtained from decoupling curves. Tentative site assignments and results on the diffusion of these Mu0 centers along with the associated conversion rates are presented. The low-energy location of neutral muonium in AlN lies off-axis in the unblocked c-axis channels at sites anti-bonding to Aluminum. Motion of Mu0 at low temperatures is due to tunneling and is dominated by thermally activated processes at high temperatures. Diffusion-limited conversion out of the mobile Mu0 state is observed in both low and high temperature regimes. All electrical types, high-resistivity, n-type and p-type, of the hexagonal 4H and 6H polytypes of SiC were studied. Two isotropic Mu0 states were found in 4H-SiC and a total of four Mu0 states were seen in the 6H-SiC samples. Temperature dependence of the hyperfine constant (AHF) for each state is discussed. Data on the hyperfine interactions imply isotropic atomic-like states with no hint of any bond-centered Mu0 species in SiC. Temperature and field dependences of signal amplitudes and relaxation rates were studied. Tentative assignments for locations and some of the dynamical characteristics of the muonium centers have been reached; however, more work is needed to fully understand the nature of these centers in SiC.
Quantum state resolved studies of copper-H₂ system and electronic spectroscopy of Cu(100)
(2009-08) Uka, Arban; Sitz, Greg Orman
Hydrogen quantum state resolved energy losses upon scattering from copper are studied using molecular beam techniques and quantum state-specific detection methods. Also clean copper and hydrogen and oxygen covered copper surfaces were studied using electron spectroscopy. There are many questions about the nature of molecule-surface dynamics and the processes. The relative role of the different degrees of freedom in the reaction and the importance of non-adiabatic effects have been two of these questions. These two questions motivated this work. Energy loss in the elastic scattering of H₂(v=1. J=1) and H₂(v=0, J=1) molecular quantum states is measured as a function of incident translational energy at two surface temperatures. The energy loss process is shown to agree to the Baule classical model for energy ranges 74-150 meV for the excited vibrationally state and 74-125 for the ground vibrational state. Results suggest that translational energy is more effective that vibrational energy in the observed process. Theoretical models have been able to explain several processes using nonadiabatic models where friction coefficient tensor is included. Results in this thesis suggest that the energy loss in the elastic scattering is a nonadiabatic one. Electron spectroscopy studies showed that the surface plasmon intensity is very sensitive to surface contamination. Using this property, surface-only sensitive virtual temperature programmed desorption (VTPD) is developed. A better understanding of unique behavior of hydrogen covered Cu(100) was gained.
Simulating the magnetic implosion of an atomic hydrogen cloud for the measurement of three-body association
(2015-08) Blinova, Alina Arkadievna; Raizen, Mark G.; Sitz, Greg O.
Three-body association (TBA) of hydrogen is the process by which three hydrogen atoms combine to form a hydrogen molecule and a free atom. The TBA reaction rate is not known precisely, yet its value plays a crucial role in the formation of the first stars. We propose an experiment to measure the TBA of hydrogen using a magnetic field to implode a cloud of atomic hydrogen to achieve high densities. In this work I present the results of a numerical simulation for the idealized case of non-interacting, point-like hydrogen atoms in a hexapole magnetic field. The results show that in this approximation, high atomic densities can be reached. Using existing TBA rate estimates, I show that observation of TBA on short time-scales is feasible with the range of atomic densities available in the proposed experiment. For a more accurate simulation, a closer look at atom-atom interactions and the thermal evolution of the cloud is needed.
The technical potential of renewable natural gas (RNG) in the United States, and the economic potential of methanation-derived RNG in Texas
(2014-12) Ólafsson, Brynjólfur Víðir; Webber, Michael E., 1971-
Renewable Natural Gas (RNG) is a low-carbon fuel source that is derived from the anaerobic digestion (AD) or thermal gasification (TG) of biomass, or produced using renewable electricity through the methanation of carbon dioxide. This thesis uses a thermodynamic balance to determine the total technical potential of RNG in the United States, as well as the future technical potential of methanation-derived RNG based on growth curves for renewable electricity. Furthermore, this work establishes an analytic decision-making framework for determining on a rolling basis, from an economic standpoint, whether to sell electricity directly to the grid, or produce and sell methanation-derived RNG. This framework is used to establish the economic potential of RNG, based on Texas wind resources. This work details the formulation of a model that determines which production option generates more marginal profit, based on fluctuating electricity and gas prices. The model also aggregates the total amount of electricity and RNG sold, assuming that the main objective is to maximize the marginal profit of integrated wind- and methanation facilities. This work concludes that the annual technical potential of methanation-derived RNG nationally was 1.03 Quads in 2011. The technical potential of biomass-derived RNG was 9.5 Quads. Thus, the total 2011 technical potential of RNG in the United States was 10.5 Quads, or equal to roughly 43% of the total US consumption of natural gas that year. Assuming a constant, 80% electrolyser efficiency, the technical potential of methanation-derived RNG is expected to rise at an average rate of 1.4% per year, following growth curves for renewable power, until the year 2040, when it will be 1.54 Quads. The 2011 economic potential of methanation-derived RNG in Texas was between 2.06×10⁷ MMBTU and 3.19×10⁷ MMBTU, or between 19.4% and 30.1% of the corresponding annual technical potential. Furthermore, the total marginal profit increase from introducing the option of producing and selling methanation-derived RNG was around $366 million, given a ‘best case scenario’ for the state of Texas.