SQCD Vacua and Geometrical Engineering

We consider the geometrical engineering constructions for the N = 1 SQCD vacua recently proposed by Giveon and Kutasov. After one T-duality, the geometries with wrapped D5 branes become N = 1 brane configurations with NS branes and D4 branes. The field theories encoded by the geometries contain extra massive adjoint fields for the flavor group. After performing a flop, the geometries contain branes, antibranes and branes wrapped on non-holomorphic cycles. The various tachyon condensations between pairs of wrapped D5 branes and anti D5 branes together with deformations of the cycles give rise to a variety of supersymmetric and metastable non-supersymmetric vacua.Comment: 21 Pages, Latex, 8 Figure

Analytical and computational indoor shelter models for infiltration of carbon dioxide into buildings : comparison with experimental data

This paper describes two indoor shelter models – an analytical model and a Computational Fluid Dynamics (CFD) model - that can be used to predict the level of infiltration of carbon dioxide (CO2) into a building following a release from an onshore CO2 pipeline. The motivation behind the development of these models was to demonstrate that the effects of shelter should be considered as part of a Quantitative Risk Assessment (QRA) for CO2 pipeline infrastructure and to provide a methodology for considering the impact of a CO2 release on building occupants.A key component in the consequence modelling of a release from a CO2 pipeline is an infiltration model for CO2 into buildings which can describe the impact on people inside buildings during a release event. This paper describes the development of an analytical shelter model and a CFD model which are capable of predicting the change in internal concentration, temperature and toxic load within a single roomed building that is totally engulfed by a transient cloud of gaseous CO2. Application of the models is demonstrated by comparison with experimental measurements of CO2 accumulation in a building placed in the path of a drifting cloud of CO2. The analytical and CFD models are shown to make good predictions of the average change in internal concentration. Furthermore, it is demonstrated that the effects of shelter should be taken into account when conducting QRA assessments on CO2 pipelines. Document type: Articl

Considerations in the Development of Flexible CCS Networks

This paper discusses considerations for the design of flexibly operated Carbon Capture and Storage (CCS) pipeline networks and is based on the findings of the Flexible CCS Network Development project (FleCCSnet), funded by the UK CCS Research Centre. The project considered the impact of flexibility across the whole CCS chain, as well as studying the interfaces between each element of the system; e.g. at the entry to the pipeline system from the capture plant and at the exit from the pipeline to the storage site. The factors identified are intended to allow CCS network designers to determine the degree of flexibility in the system, allowing them to react effectively to short, medium and long term variations in the availability and flow of CO2 from capture plants and the constraints imposed on the system by CO2 storage sites. The work of the project is reviewed in this paper which explores the flexibility of power plants operating with post combustion capture systems; quantifies the available time to store (line pack) liquid CO2 in the pipeline as a function of pipeline size, the inlet mass flow rate and operating pressure; and explores the influence that uncertainty in storage parameters have on the design of the pipeline. In addition, parameters influencing short and longer term network designs are discussed in terms of varying flow rates. Two workshops contributed to the direction of the project. The first workshop identified and confirmed key questions to be considered in order to understand the most likely impacts of variability in the CO2 sources and variability in CO2 sinks on CO2 transport system design and operation. The second workshop focused on transient issues in the pipeline and storage site. Although the case studies in the work are UK based, this work is applicable to other situations where large and small sources of CO2 feed into a transportation system. The work is expected to inform a broad range of stakeholders and allow network designers to anticipate potential problems associated with the operation of a CCS network. For an effective design of CCS infrastructure, all of the factors that will have a substantial impact on CO2 flow will have to be analysed at an early stage to prevent possible bottle necks in the whole chain

Impacts of geological store uncertainties on the design and operation of flexible CCS offshore pipeline infrastructure

Planning for Carbon Capture and Storage (CCS) infrastructure needs to address the impact of store uncertainties and store flow variability on infrastructure costs and availability. Key geological storage properties (pressure, temperature, depth and permeability) can affect injectivity and lead to variations in CO2 flow, which feed back into the pipeline transportation system. In previous storage models, the interface between the reservoir performance and the transportation infrastructure is unclear and the models are unable to provide details for flow and pressure management within a transportation network in response to changes in the operation of storage sites. Variation in storage demand due to daily and seasonal variations of fossil fuels uses and by extension CO2 flow is also likely to influence transportation infrastructure availability and the capacity to deliver. This work examines, at the level of infrastructure planning, the impact of store properties on CCS transportation and injection infrastructure in the context of flow variability. Different off-shore transportation scenarios, relevant to CCS in the UK, are evaluated using rigorous process modelling tools. Considering flow variations of ±50% of a given baseline flow, the results of the analysis indicate that enabling store flexibility is simpler in reservoirs with an initial pressure above 20 MPa. Wellhead conditions are influenced significantly by subsurface conditions. The operational envelope of the storage site is limited by the proximity of wellhead conditions to the CO2 phase equilibrium line and the maximum fluid velocities inside the well. Given reductions in reservoir permeability, the requirements for pressure delivery are strongly dependent on the reservoir temperature. This work provides detailed insight on the expected impacts of store properties on transportation infrastructure design and operation

Metastable Vacua and Geometrical Engineering

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

A general review on rock stability due to CO2 injection

A review paper is presented on the stability analysis of rock formations for carbon sequestration by summarizing the potential loadings that caprock can be exposed to. An overview of the existing coupled analytical models of rock, Thermo-Hydro-Mechanical (THM) models, describing mechanical changes, flow effects and thermal distributions due to different loading conditions on porous rock is given. Additionally, experimental work based on the theoretical differential equations of THM models is outlined, as well as different numerical studies based on constitutive models. Generally, numerical modeling techniques used in the literature were mainly set up for the update and validation of the undertaken experimental work, which was compared to the modeling results