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Chemistry, materials, & energy publications

SRI Research Presented at the National Energy Technology Laboratory (NETL) 2015 Carbon Capture Technology Meeting

Three SRI researchers presented information at the National Energy Technology Laboratory (NETL) 2015 Carbon Capture Technology Meeting :

Development of Mixed-Salt Technology for CO 2 Capture from Coal Power Plants
Indira Jayaweera
Pilot-Scale Evaluation of an Advanced Carbon Sorbent-Based Process for Post-Combustion Carbon Capture
Marc Hornbostel
CO 2 Capture from IGCC Gas Streams Using the AC-ABC Process
Anoop Nagar
Development of a Pre-Combustion CO 2 Capture Process Using High-Temperature PBI Hollow-Fiber Membranes
Indira S. Jayaweera

Energy & green tech publications

Evidence for Generation of Unstable Suprathermal Electron Population in the Auroral F Region

Anomalous incoherent scatter radar (ISR) spectra confined to narrow altitude ranges near the Fregion peak and correlated with dynamic auroral precipitation have previously been identified and explained in terms of the cavitating beam-driven Langmuir turbulence. In this work we used a one-dimensional Zakharov simulation to constrain the range of physical mechanisms underlying these observational features. We find that although Langmuir wave collapse and caviton formation generated by electron beams with energies of 1 keV can give rise to similar radar echoes, the predicted spectral features and intensities of such echoes are inconsistent with experimental data acquired by various ISRs. Our results suggest that the free energy for the turbulence must be provided by unstable low-energy (5 − 20 eV) electron populations and that such populations must be produced locally in the F region ionosphere.

Energy & green tech publications

A Top to Bottom Evaluation of IRI 2007 within the Polar Cap

Monthly median values of ionospheric peak height (hmF2) and density (NmF2), derived from ionosonde measurements at four Canadian High Arctic Ionospheric Network (CHAIN) stations situated within the polar cap and Auroral Oval, are used to evaluate the performance of the International Reference Ionosphere (IRI) 2007 empirical ionospheric model during the recent solar minimum between 2008 and 2010. This analysis demonstrates notable differences between IRI and ionosonde NmF2 diurnal and seasonal behavior over the entire period studied, where good agreement is found during summer periods but otherwise errors in excess of 50% were prevalent, particularly during equinox periods. hmF2 is found to be marginally overestimated during winter and equinox nighttime, while also being underestimated during summer and equinox daytime by in excess of 25%. These errors are shown to be related to significant mismodeling of the M(3000)F2 propagation factor. The ionospheric bottomside thickness parameter (B0) is also evaluated using ionosonde measurements. It is found that both of the IRI’s internal B0 models significantly misrepresent both seasonal and diurnal variations in bottomside thickness when compared to ionosonde observations, where errors at times exceed 40%. A comparison is also presented between IRI and Resolute (74.75N, 265.00E) Advanced Modular Incoherent Scatter Radar (AMISR)-derived topside thickness. It is found in this comparison that the IRI is capable of modeling ionospheric topside thickness exceptionally well during winter and summer periods but fails to represent significant diurnal variability during the equinoxes and seasonal variations.

Chemistry, materials, & energy publications

Self-ignition of Hydrogen Releases through Electrostatic Discharge Induced by Entrained Particulates

The potential for particulates entrained in hydrogen releases to generate electrostatic charge and induce electrostatic discharge ignitions was investigated. A series of tests were performed in which hydrogen was released through a 3.175-mm diameter orifice from an initial pressure of 140 bar. Electrostatic field sensors were used to characterize the electrification of known quantities of iron oxide particulates deliberately entrained in the release. The ignition experiments focused on using charged particulates to induce spark discharges from isolated conductors and corona discharges. A total of 12 ignition events were observed. The results show that electrification of entrained particulates is a viable self-ignition mechanism of hydrogen releases.

Highlights

Measured accumulation of charge on iron oxide particulates entrained in hydrogen jets.
Investigated particulate induced spark discharge ignition.
Investigated particulate induced corona discharge ignition.
Results showed that entrained particulates can be a source of spontaneous ignition.
All ignition events observed occurred in close proximity to ungrounded metal.

Chemistry, materials, & energy publications

Experimental Investigation of Hydrogen Release and Ignition from Fuel Cell Powered Forklifts in Enclosed Spaces

Due to rapid growth in the use of hydrogen powered fuel cell forklifts within warehouse enclosures, Sandia National Laboratories has worked to develop scientific methods that support the creation of new hydrogen safety codes and standards for indoor refueling operations. Based on industry stakeholder input, conducted experiments were devised to assess the utility of modeling approaches used to analyze potential consequences from ignited hydrogen leaks in facilities certified according to existing code language. Release dispersion and combustion characteristics were measured within a scaled test facility located at SRI International’s Corral Hollow Test Site. Moreover, the impact of mitigation measures such as active/passive ventilation and pressure relief panels was investigated. Since it is impractical to experimentally evaluate all possible facility configurations and accident scenarios, careful characterization of the experimental boundary conditions has been performed so that collected datasets can be used to validate computational modeling approaches.
Highlights
Benchmark library for accident scenarios during H2 indoor refueling was created.
For tank blowdown warehouse H2 rapidly leans out once release finishes.
Large plume ignition overpressures were observed in well-sealed warehouse scenarios.
Passive venting reduced plume ignition overpressure; forced venting had no impact.
Blowout panels are effective overpressure mitigation devices.

Chemistry, materials, & energy publications

Releases from Hydrogen Fuel-Cell Vehicles in Tunnels

An important issue concerning the safe use of hydrogen-powered fuel-cell vehicles is the possibility of accidents inside tunnels resulting in the release of hydrogen. To investigate the potential consequences, a combined experimental and modeling study has been performed to characterize releases from a hydrogen fuel-cell vehicle inside a tunnel. In the scenario studied, all three of the fuel-cell vehicle’s onboard hydrogen tanks were simultaneously released through three thermal pressure relief devices (TPRDs) toward the road surface. Computation fluid dynamics (CFD) simulations were used to model the release of hydrogen from the fuel-cell vehicle and to study the behavior of the ignitable hydrogen cloud inside the tunnel. Deflagration overpressure simulations of the hydrogen cloud within the tunnel were also performed for different ignition delay times and ignition locations. To provide model validation data for these simulations, experiments were performed in a scaled tunnel test facility at the SRI Corral Hollow Experiment Site (CHES). The scaled tunnel tests were designed to resemble the full-scale tunnel simulations using Froude scaling. The scale factor, based on the square route of the ratio of the SRI tunnel area to the full-scale tunnel area was 1/2.53. The same computational models used in the full-scale tunnel simulations were applied to these scaled tunnel tests to validate the modeling approach.
Highlights
The release scenario was thermal activation of the pressure release devices on the vehicle’s tanks.
Simulations were used to model the release of hydrogen from the fuel-cell vehicle.
The simulations were validated by performing tests in a scaled tunnel experiment.
Risk analysis indicates that the level of potential risk from such accidents is small.

Energy & green tech publications

Applying Learning Curves to Modeling Future Coal and Gas Power Generation Technologies

Coal and natural gas have and will likely continue to be key components of the world energy supply for years to come. Currently, the most efficient commercial technologies for power production are supercritical pulverized coal combustion (SCPC) and natural gas combustion with combined cycle (NGCC). Emerging technologies for more efficient power generation from coal include ultra-super-critical pulverized coal (USCPC), advanced ultra-super-critical PC, integrated gasification combined cycle (IGCC), integrated gasification fuel cell combined cycle (IGFC), and direct carbon fuel cell. They each have different capital and operating costs leading to different levelized cost of electricity (LCOE). To forecast each of these competing technologies under various scenarios of electricity demand, fuel cost, and research investment, we created a Power Technology Futures Model (PTFM) based on “learning curves” methodology. Technology learning curves are a powerful tool for forecasting anticipated performance improvements due to a broad range of technical improvements without specifying the parameters of every possible improvement. The model can help planners and policy makers explore, visualize, and communicate how research and development (R&D) investments in certain technologies affect the mix of technologies deployed in the future. We utilized the Analytica modeling package and included detailed economic calculations to estimate the levelized costs for several types of coal and natural gas power plants with and without carbon capture technologies. Future improvements in plant efficiency and reductions in capital and operating and mantainence (O&M) costs were modeled using technology learning curves that were established by a detailed analysis of historic performance data. We used published estimates of future demand and fuel costs where available, but the model allows the user to easily input other numbers as tables or equations. Adoption of carbon capture was modeled in a variety of ways including being driven by a carbon cap or a carbon tax. The results of the model depict the difficulty of meeting a 50% reduction in annual CO 2 production by 2050, even with significant R&D investments, ambitious CO 2 pricing, and decreased demand for energy from coal and natural gas.