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  • Journal article
    Stoerzinger KA, Hong WT, Wang XR, Rao RR, Subramanyam SB, Li C, Ariando, Venkatesan T, Liu Q, Crumlin EJ, Varanasi KK, Shao-Horn Yet al., 2017,

    Decreasing the Hydroxylation Affinity of La<sub>1-<i>x</i></sub>Sr<i><sub>x</sub></i>MnO<sub>3</sub> Perovskites To Promote Oxygen Reduction Electrocatalysis

    , CHEMISTRY OF MATERIALS, Vol: 29, Pages: 9990-9997, ISSN: 0897-4756
    • Cite
    • Citations: 38
  • Journal article
    Rao RM, Kolb MJ, Halck NB, Pedersen AF, Mehta A, You H, Stoerzinger KA, Feng Z, Hansen HA, Zhou H, Giordano L, Rossmeisl J, Vegge T, Chorkendorff I, Stephens IEL, Shao-Horn Yet al., 2017,

    Towards identifying the active sites on RuO2 (110) in catalyzing oxygen evolution

    , Energy and Environmental Science, Vol: 10, Pages: 2626-2637, ISSN: 1754-5692

    While the surface atomic structure of RuO2 has been well studied in ultra high vacuum, much less is known about theinteraction between water and RuO2 in aqueous solution. In this work, in situ surface X-ray scattering measurementscombined with density functional theory (DFT) was used to determine the surface structural changes on single-crystalRuO2 (110) as a function of potential in acidic electrolyte. The redox peaks at 0.7, 1.1 and 1.4 V vs. reversible hydrogenelectrode (RHE) could be attributed to surface transitions associated with the successive deprotonation of -H2O on thecoordinatively unsaturated Ru sites (CUS) and hydrogen adsorbed to the bridging oxygen sites. At potentials relevant tothe oxygen evolution reaction (OER), an –OO species on the Ru CUS sites was detected, which was stabilized by aneighboring -OH group on the Ru CUS or bridge site. Combining potential-dependent surface structures with theirenergetics from DFT led to a new OER pathway, where the deprotonation of the -OH group used to stabilize –OO wasfound to be rate-limiting.
  • Journal article
    Hwang J, Rao RR, Giordano L, Katayama Y, Yu Y, Shao-Horn Yet al., 2017,

    Perovskites in catalysis and electrocatalysis

    , SCIENCE, Vol: 358, Pages: 751-756, ISSN: 0036-8075
  • Journal article
    Riesen M, Konstantinoudis G, Lang P, Low N, Hatz C, Maeusezahl M, Spaar A, Bühlmann M, Spycher BD, Althaus CLet al., 2017,

    Exploring variation in human papillomavirus vaccination uptake: multi-level spatial analysis

    <jats:title>Abstract</jats:title> <jats:sec> <jats:title>Background</jats:title> <jats:p>Understanding the factors that influence human papillomavirus (HPV) vaccination uptake is critically important to design effective vaccination programmes. In Switzerland, completed HPV vaccination by age 16 years among women ranges from 30 to 79% across 26 cantons (states). Our objective was to identify factors that are associated with the spatial variation in HPV vaccination uptake.</jats:p> </jats:sec> <jats:sec> <jats:title>Methods and findings</jats:title> <jats:p>We used data from the Swiss National Vaccination Coverage Survey 2009-2016 on HPV vaccination status (≥1 dose) of 14-17 year old girls, their municipality of residence and their nationality for 21 of 26 cantons (N=8,965). We examined covariates at municipality level: language, degree of urbanisation, socio-economic position, religious denomination, results of a vote about vaccination laws; and, at cantonal level, availability of school-based vaccination and survey period. We used a series of conditional auto regressive (CAR) models to assess the effects of covariates while accounting for variability between cantons and municipal-level spatial autocorrelation. In the best-fit model, school-based vaccination (adjusted odds ratio, OR: 2.51, 95% credible interval, CI: 1.77-3.56) was associated with increased uptake, while lower acceptance of vaccination laws was associated with lower HPV vaccination uptake (OR 0.61, 95% CI: 0.50-0.73). Overall, the covariates explained 88% of the municipal-level variation in uptake.</jats:p> </jats:sec> <jats:sec> <jats:title>Conclusions</jats:title> <jats:p>In Switzerland, cantons play a prominent role
  • Report
    Rhodes A, Gazis E, Gross RJK, 2017,

    Is the UK facing an electricity security crisis? An Energy Futures Lab briefing paper.

    , Publisher: Imperial College Energy Futures Lab

    Britain’s media outlets have carried manystories about an ‘energy gap’, claimed to havearisen because the UK has failed to buildenough power stations to meet demand. Talkof upcoming ‘blackouts’, with the UK unable toproduce enough electricity to keep the lights on,is commonplace, with several hundred articlespublished in mainstream UK newspapers onthis topic over the last decade. These claimshave always been contested by the governmentand electricity system operator, National Grid,but the debate continues. This Briefing Paper,produced by Energy Futures Lab, reviews theevidence to determine whether the UK will facean electricity security crisis in the coming years.
  • Journal article
    Konstantinoudis G, Kreis C, Ammann RA, Niggli F, Kuehni CE, Spycher BDet al., 2017,

    Spatial clustering of childhood leukaemia in Switzerland: A nationwide study

    , INTERNATIONAL JOURNAL OF CANCER, Vol: 141, Pages: 1324-1332, ISSN: 0020-7136
  • Conference paper
    Sechi S, Giarola S, Lanzini A, Gandiglio M, Oluleye O, Santarelli M, Hawkes Aet al., 2017,

    Techno-economic assessment of the effects of biogas rate fluctuations on industrial applications of solid-oxide fuel cells

    , ESCAPE-27, Publisher: Elsevier, ISSN: 1570-7946

    Wastewater treatment is an energy and greenhouse gas intensive process. An important opportunity to reduce both of these quantities is via the use of biogas in co-generation systems. Solid-oxide fuel cells (SOFCs) are the generator types studied in this work.The feasibility of the retrofitting of a wastewater treatment facility fitted with a SOFC combined heat and power energy provision system is assessed including effects of uncertainties in biogas availability on cost and energy performance. A two-stage stochastic optimization framework is proposed to provide feedback on the energy co-generation system design.Results quantify standard deviations in the biogas rate beyond which the SOFC capacity factor might drop below 80 % and change the optimal size of the modules to install.Keywords: solid-oxide fuel cells, stochastic optimization, wastewater treatment, biogas.
  • Journal article
    bruneau N, zika J, Toumi R, 2017,

    Can the ocean’s heat engine control horizontal circulation? Insights from the Caspian Sea.

    , Geophysical Research Letters, Vol: 44, Pages: 9893-9900, ISSN: 0094-8276

    We investigate the role of the ocean's heat engine in setting horizontal circulation using a numerical model of the Caspian Sea. The Caspian Sea can be seen as a virtual laboratory - a compromise between realistic global models which are hampered by long equilibration times and idealized basin geometry models which are not constrained by observations. We find that increases in vertical mixing drive stronger thermally direct overturning and consequent conversion of available potential to kinetic energy. Numerical solutions with water mass structures closest to observations overturn 0.02 − 0.04 x 106m3/s(Sv) representing the first estimate of Caspian Sea overturning. Our results also suggest that the overturning is thermally-forced increasing in intensity with increasing vertical diffusivity. Finally, stronger thermally direct overturning is associated with a stronger horizontal circulation in the Caspian Sea. This suggests the ocean's heat engine can strongly impact broader horizontal circulations in the ocean.
  • Conference paper
    Kuznetsov D, Han B, Rao R, Shao-Horn Yet al., 2017,

    Linking the effect of the metal ion doping to metal oxides redox transitions and OER activity

    , 254th National Meeting and Exposition of the American-Chemical-Society (ACS) on Chemistry's Impact on the Global Economy, Publisher: AMER CHEMICAL SOC, ISSN: 0065-7727
  • Conference paper
    Rao R, Shao-Horn Y, 2017,

    Understanding the active sites and reaction mechanism for oxygen electrocatalysis on ruthenium dioxide surfaces

    , 254th National Meeting and Exposition of the American-Chemical-Society (ACS) on Chemistry's Impact on the Global Economy, Publisher: AMER CHEMICAL SOC, ISSN: 0065-7727
  • Journal article
    Li Y, Toumi R, 2017,

    A balanced Kalman filter ocean data assimilation system with application to the South Australian Sea

    , Ocean Modelling, Vol: 116, Pages: 159-172, ISSN: 1463-5003

    n this paper, an Ensemble Kalman Filter (EnKF) based regional ocean data assimilation system has been developed and applied to the South Australian Sea. This system consists of the data assimilation algorithm provided by the NCAR Data Assimilation Research Testbed (DART) and the Regional Ocean Modelling System (ROMS). We describe the first implementation of the physical balance operator (temperature-salinity, hydrostatic and geostrophic balance) to DART, to reduce the spurious waves which may be introduced during the data assimilation process. The effect of the balance operator is validated in both an idealised shallow water model and the ROMS model real case study. In the shallow water model, the geostrophic balance operator eliminates spurious ageostrophic waves and produces a better sea surface height (SSH) and velocity analysis and forecast. Its impact increases as the sea surface height and wind stress increase. In the real case, satellite-observed sea surface temperature (SST) and SSH are assimilated in the South Australian Sea with 50 ensembles using the Ensemble Adjustment Kalman Filter (EAKF). Assimilating SSH and SST enhances the estimation of SSH and SST in the entire domain, respectively. Assimilation with the balance operator produces a more realistic simulation of surface currents and subsurface temperature profile. The best improvement is obtained when only SSH is assimilated with the balance operator. A case study with a storm suggests that the benefit of the balance operator is of particular importance under high wind stress conditions. Implementing the balance operator could be a general benefit to ocean data assimilation systems.
  • Conference paper
    Arcucci R, Celestino S, Toumi R, Laccetti Get al., 2017,

    Toward the S3DVAR data assimilation software for the Caspian Sea

    , International Conference on Numerical Analysis and Applied Mathematics (ICNAAM), Publisher: AIP Publishing, ISSN: 1551-7616

    Data Assimilation (DA) is an uncertainty quantification technique used to incorporate observed data into a prediction model in order to improve numerical forecasted results. The forecasting model used for producing oceanographic prediction into the Caspian Sea is the Regional Ocean Modeling System (ROMS). Here we propose the computational issues we are facing in a DA software we are developing (we named S3DVAR) which implements a Scalable Three Dimensional Variational Data Assimilation model for assimilating sea surface temperature (SST) values collected into the Caspian Sea with observations provided by the Group of High resolution sea surface temperature (GHRSST). We present the algorithmic strategies we employ and the numerical issues on data collected in two of the months which present the most significant variability in water temperature: August and March.
  • Journal article
    Sparks NJ, Hardwick SR, Schmid M, Toumi Ret al., 2017,

    IMAGE: a multivariate multi-site stochastic weather generator for European weather and climate

    , Stochastic Environmental Research and Risk Assessment, Vol: 32, Pages: 771-784, ISSN: 1436-3240

    Capturing the spatial and temporal correlation of multiple variables in a weather generator is challenging. A new massively multi-site, multivariate daily stochastic weather generator called IMAGE is presented here. It models temperature and precipitation variables as latent Gaussian variables with temporal behaviour governed by an auto-regressive model whose residuals and parameters are correlated through resampling of principle component time series of empirical orthogonal function modes. A case study using European climate data demonstrates the model’s ability to reproduce extreme events of temperature and precipitation. The ability to capture the spatial and temporal extent of extremes using a modified Climate Extremes Index is demonstrated. Importantly, the model generates events covering not observed temporal and spatial scales giving new insights for risk management purposes.
  • Journal article
    Corsaro CM, Toumi R, 2017,

    A self-weakening mechanism for tropical cyclones

    , Quaterly Journal of the Royal Meteological Society, Vol: 143, Pages: 2585-2599, ISSN: 1477-870X

    A mechanism leading to the self-weakening of tropical cyclones is proposed using the Weather and Research and Forecasting model. A comparison between an experiment with variable Coriolis parameter f and one on an f-plane shows that after the initial intensification the former is characterized by a smaller intensity. As opposed to the tropical cyclone on the f-plane, the one with variable f weakens significantly after reaching maturity. Analyses of the 3-D circulation show that the main reason for the weakening is dry intrusion in the mid-upper troposphere from the west. Once the dry intrusion reaches the inner vortex, strong downdrafts reduce the high equivalent potential temperature in the boundary layer inflow. The subsequent updrafts in the eyewall, characterized by lower equivalent potential temperature, are considerably reduced and, consequently, the secondary circulation weakens.Back-trajectories are used to determine the origin of the dry intrusion. It is found that the air parcels expelled from the storm deep convection into the outflow layer recirculate anticyclonically back into the vortex, causing a self-weakening of the tropical cyclone. A time span for the recirculation of at least 48 h allows the air parcels to sink substantially before reaching the vortex circulation. Some implications of the intrinsic nature of this process are briefly discussed.
  • Conference paper
    Arcucci R, D'Amore L, Toumi R, 2017,

    Preconditioning of the background error covariance matrix in data assimilation for the Caspian Sea

    , 1st International Conference on Applied Mathematics and Computer Science (ICAMCS), Publisher: AIP Publishing, ISSN: 1551-7616

    Data Assimilation (DA) is an uncertainty quantification technique used for improving numerical forecasted results by incorporating observed data into prediction models. As a crucial point into DA models is the ill conditioning of the covariance matrices involved, it is mandatory to introduce, in a DA software, preconditioning methods. Here we present first studies concerning the introduction of two different preconditioning methods in a DA software we are developing (we named S3DVAR) which implements a Scalable Three Dimensional Variational Data Assimilation model for assimilating sea surface temperature (SST) values collected into the Caspian Sea by using the Regional Ocean Modeling System (ROMS) with observations provided by the Group of High resolution sea surface temperature (GHRSST). We also present the algorithmic strategies we employ.
  • Journal article
    Stoerzinger KA, Rao RR, Wang XR, Hong WT, Rouleau CM, Shao-Horn Yet al., 2017,

    The Role of Ru Redox in pH-Dependent Oxygen Evolution on Rutile Ruthenium Dioxide Surfaces

    , CHEM, Vol: 2, Pages: 668-675, ISSN: 2451-9294
  • Journal article
    Phillipson L, Toumi R, 2017,

    Impact of data assimilation on ocean current forecasts in the Angola Basin

    , OCEAN MODELLING, Vol: 114, Pages: 45-58, ISSN: 1463-5003

    The ocean current predictability in the data limited Angola Basin was investigated using the Regional Ocean Modelling System (ROMS) with four-dimensional variational data assimilation. Six experiments were undertaken comprising a baseline case of the assimilation of salinity/temperature profiles and satellite sea surface temperature, with the subsequent addition of altimetry, OSCAR (satellite-derived sea surface currents), drifters, altimetry and drifters combined, and OSCAR and drifters combined. The addition of drifters significantly improves Lagrangian predictability in comparison to the baseline case as well as the addition of either altimetry or OSCAR. OSCAR assimilation only improves Lagrangian predictability as much as altimetry assimilation. On average the assimilation of either altimetry or OSCAR with drifter velocities does not significantly improve Lagrangian predictability compared to the drifter assimilation alone, even degrading predictability in some cases. When the forecast current speed is large, it is more likely that the combination improves trajectory forecasts. Conversely, when the currents are weaker, it is more likely that the combination degrades the trajectory forecast.
  • Journal article
    Stoerzinger KA, Diaz-Morales O, Kolb M, Rao RR, Frydendal R, Qiao L, Wang XR, Halck NB, Rossmeisl J, Hansen HA, Vegge T, Stephens IEL, Koper MTM, Shao-Horn Yet al., 2017,

    Orientation-Dependent Oxygen Evolution on RuO2 without Lattice Exchange

    , ACS ENERGY LETTERS, Vol: 2, Pages: 876-881, ISSN: 2380-8195
  • Journal article
    Oluleye G, Jiang N, Smith R, Jobson Met al., 2017,

    A novel screening framework for waste heat utilization technologies

    , Energy, Vol: 125, Pages: 367-381, ISSN: 0360-5442

    © 2017 Elsevier Ltd Waste heat exploitation improves the energy efficiency of process sites, ensuring lower costs and lower CO2emissions. Technologies such as organic Rankine cycles, absorption chillers, mechanical heat pumps, absorption heat transformers and absorption heat pumps exist to utilize waste heat. Though these technologies make waste heat re-use technically feasible, selection of technologies based on different heat source temperatures still needs to be addressed. In this work, a novel screening approach is proposed to compare technologies considering the waste heat source quality. A methodology is also presented to select technologies for a process site based on the screening results. Since multiple energy form interactions occur, the screening criterion considers the deviation of the actual performance from the ideal performance of technology options, taking into account irreversibilities as a result of finite temperature heat transfer. The tool is applied to screen and select technologies for waste heat sources below 265 °C. Results identify the temperature ranges where technologies have minimum exergy degradation. The framework systematically matches heat source temperatures with technology options compared to a trial and error approach. The framework was applied to an industrial case study to recover 45,660 kW of useful energy from the available waste heat.
  • Conference paper
    Allison J, Bell K, Clarke J, Cowie A, Elsayed A, Flett G, Oluleye O, Hawkes A, Hawker G, Kelly N, Manuela Marinho de Castro M, Sharpe T, Shea A, Strachan Pet al., 2017,

    Domestic thermal storage requirements for heat demand flexibility

    , Sustainable Thermal Energy Management International Conference
  • Journal article
    Cahill B, Toumi R, Stenchikov G, Osipov S, Brindley Het al., 2017,

    Evaluation of thermal and dynamic impacts of summer dust aerosols on the Red Sea

    , Journal of Geophysical Research: Oceans, Vol: 122, Pages: 1325-1346, ISSN: 2169-9275

    The seasonal response of upper ocean processes in the Red Sea to summer-time dust aerosol perturbations is investigated using an uncoupled regional ocean model. We find that the upper limit response is highly sensitive to dust-induced reductions in radiative fluxes. Sea surface cooling of −1°C and −2°C is predicted in the northern and southern regions, respectively. This cooling is associated with a net radiation reduction of −40 W m−2 and −90 W m−2 over the northern and southern regions, respectively. Larger cooling occurs below the mixed layer at 75 m in autumn, −1.2°C (north) and −1.9°C (south). SSTs adjust more rapidly (ca. 30 days) than the subsurface temperatures (seasonal time scales), due to stronger stratification and increased mixed layer stability inhibiting the extent of vertical mixing. The basin average annual heat flux reverses sign and becomes positive, +4.2 W m−2 (as compared to observed estimates −17.3 W m−2) indicating a small gain of heat from the atmosphere. When we consider missing feedbacks from atmospheric processes in our uncoupled experiment, we postulate that the magnitude of cooling and the time scales for adjustment will be much less, and that the annual heat flux will not reverse sign but nevertheless be reduced as a result of dust perturbations. While our study highlights the importance of considering coupled ocean-atmosphere processes on the net surface energy flux in dust perturbation studies, the results of our uncoupled dust experiment still provide an upper limit estimate of the response of the upper ocean to dust-induced radiative forcing perturbations.
  • Journal article
    Arcucci R, D'Amore L, Pistoia J, Toumi R, Murli Aet al., 2017,

    On the variational data assimilation problem solving and sensitivity analysis

    , JOURNAL OF COMPUTATIONAL PHYSICS, Vol: 335, Pages: 311-326, ISSN: 0021-9991

    We consider the Variational Data Assimilation (VarDA) problem in an operational framework, namely, as it results when it is employed for the analysis of temperature and salinity variations of data collected in closed and semi closed seas. We present a computing approach to solve the main computational kernel at the heart of the VarDA problem, which outperforms the technique nowadays employed by the oceanographic operative software. The new approach is obtained by means of Tikhonov regularization. We provide the sensitivity analysis of this approach and we also study its performance in terms of the accuracy gain on the computed solution. We provide validations on two realistic oceanographic data sets.
  • Journal article
    Nissan H, Toumi R, 2016,

    Regional modelling of rainfall erosivity: Sensitivity of soil erosion to aerosol emissions

    , Quarterly Journal of the Royal Meteorological Society, Vol: 143, Pages: 265-277, ISSN: 1477-870X

    A rainfall erosivity scheme is implemented into the widely-used regional atmosphere-landmodel, WRF. Rainfall erosivity is parameterised from hourly precipitation and surface runoff in a high resolution (4 km) convection-permitting model. The scheme is used to examine thepotential effects of changes in atmospheric aerosol concentrations on soil erosion in a case study of northern India and the surrounding countries for the 2010 monsoon season, using a model which isolates the indirect effect on cloud microphysics only. This study offers a preliminary investigation into this emerging topic, but longer simulations would be needed to establish a robust signal.Summer precipitation is reduced in most areas and the monsoon circulation weakens for increases in cloud condensation nuclei concentrations. This can be attributed to localised cloud microphysical changes in the northeast of India, which induce a dynamic response opposing the monsoon circulation. The two regions of greatest decrease in erosion with increasing aerosolare in the Western Ghats and the Ganges Delta, both significant cropland areas. However, the effect is not uniform, with isolated local increases in soil erosion. These results suggest that, while efforts to reduce anthropogenic aerosol emissions may improve water availability for crops through enhanced rainfall, these benefits are likely to be tempered by an increase in soil erosion, though robust local changes were difficult to predict.
  • Journal article
    Trivedi A, Toumi R, 2016,

    Mechanisms of bottom boundary fluxes in a numerical model of the Shetland shelf

    , Ocean Dynamics, Vol: 67, Pages: 1-21, ISSN: 1616-7341

    Across-slope bottom boundary layer (BBL) fluxes on the shelf-edge connectthis region to deeper waters. Two proposed ways in which across-slope BBLfluxes can occur, in regions that have a slope current aligned to the bathymetry, are:the frictional veering of bottom currents termed the ‘Ekman drain’; and through localwind-forced downwelling (wind-driven surface Ekman flow with an associated bottomflow). We investigate the variability, magnitude and spatial scale of BBL fluxeson the Shetland shelf, which has a prominent slope current, using a high-resolution(∼ 2 km) configuration of the MITgcm model. Fluxes are analysed in the BBL atthe shelf break near the 200 m isobath and are found to have a seasonal variabilitywith high/low volume transport in winter/summer respectively. By using a multivariateregression approach, we find that the locally wind-driven Ekman transport playsno explicit role in explaining daily bottom fluxes. We can better explain the variabilityof the across-slope BBL flux as a linear function of the speed and across-slopecomponent of the interior flow, corresponding to an Ekman plus mean-flow flux. Weestimate that the mean-flow is a greater contributor than the Ekman flux to the BBLflux. The spatial heterogeneity of the BBL fluxes can be attributed to the mean-flow,which has a much shorter decorrelation length compared to the Ekman flux. We concludethat both the speed and direction of the interior current determines the dailyBBL flux. The wind does not explicitly contribute through local downwelling, butmay influence the interior current and therefore implicitly the BBL fluxes on longertimescales.
  • Journal article
    Bruneau N, Toumi R, 2016,

    A fully-coupled atmosphere-ocean-wave model of the Caspian Sea

    , Ocean Modelling, Vol: 107, Pages: 97-111, ISSN: 1463-5011

    Located in the mid-latitudes, the Caspian Sea is the largest enclosed basin in the world. A fully-coupled atmosphere-ocean-wave model of the Caspian Sea at high resolution (8 km) for a period of three years is presented. After validating each component of the modelling platform, the wave state of the Caspian Sea is studied. Results show very different wave regimes between the three different basins, a strong seasonality and an almost swell-free state. It is shown here that waves modify the horizontal eddy viscosity and vertical heat diffusion. However, due to a reasonably weak annual wave state, these effects are restricted to the upper-ocean layer (< 30 m) except during the most severe events (100 m).Three main experiments are conducted: 1) the ROMS ocean model forced by atmospheric reanalysis (CFSR), 2) ROMS coupled with the atmospheric model WRF and 3) the impact of wave-induced processes. The seasonality of the Caspian Sea is accurately captured in each experiment which highlights a rapid warming of the sea surface temperature (SST) in spring while the mixed layer depths (MLD) become very rapidly shallow (shifting from over 100 m to 15 m in two months). Contrarily, a gentle cooling of the SST accompanied with a deepening of the MLD is modelled during autumn and winter. The results also show a significant improvement of the model skill in the representation of the dynamics when ROMS is coupled to WRF.Finally, as ocean surface waves imply feedback at the interface atmosphere-ocean through the transfer of momentum, mass and heat, we investigate their potential effects on the Caspian Sea dynamics. Results are mixed and show a reasonably weak impact of wave-induced processes. While waves have a negligible effect during the winter as wave-induced mixing is confined to the MLD, the summer global SST are less accurately modelled due to the enhancement of mixing in shallow MLDs. However the SST bias, temperature at a subsurface location are improved.
  • Journal article
    Wang S, Toumi R, 2016,

    On the relationship between hurricane cost and the integrated wind profile

    , Environmental Research Letters, Vol: 11, ISSN: 1748-9326

    It is challenging to identify metrics that best capture hurricane destructive potential and costs. Although it has been found that the sea surface temperature and vertical wind shear can both make considerable changes to the hurricane destructive potential metrics, it is still unknown which plays a more important role. Here we present a new method to reconstruct the historical wind structure of hurricanes that allows us, for the first time, to calculate the correlation of damage with integrated power dissipation and integrated kinetic energy of all hurricanes at landfall since 1988. We find that those metrics, which include the horizontal wind structure, rather than just maximum intensity, are much better correlated with the hurricane cost. The vertical wind shear over the main development region of hurricanes plays a more dominant role than the sea surface temperature in controlling these metrics and therefore also ultimately the cost of hurricanes.
  • Journal article
    Wang S, Toumi R, 2016,

    On the relationship between hurricane cost and the integrated wind profile

    , Environmental Research Letters, Vol: 11, ISSN: 1748-9326

    It is challenging to identify metrics that best capture hurricane destructive potential and costs. Although it has been found that the sea surface temperature and vertical wind shear can both make considerable changes to the hurricane destructive potential metrics, it is still unknown which plays a more important role. Here we present a new method to reconstruct the historical wind structure of hurricanes that allows us, for the first time, to calculate the correlation of damage with integrated power dissipation and integrated kinetic energy of all hurricanes at landfall since 1988. We find that those metrics, which include the horizontal wind structure, rather than just maximum intensity, are much better correlated with the hurricane cost. The vertical wind shear over the main development region of hurricanes plays a more dominant role than the sea surface temperature in controlling these metrics and therefore also ultimately the cost of hurricanes.
  • Journal article
    Chang S, Cao X, Zou Z, Isac M, Guthrie RILet al., 2016,

    Microbubble Swarms in a Full-Scale Water Model Tundish

    , Metallurgical and Materials Transactions B Process Metallurgy and Materials Processing Science, Vol: 47, Pages: 2732-2743, ISSN: 1073-5615

    Water modeling, using microbubble swarms, was performed in a full-scale, four-strand, delta-shaped tundish, located at the McGill Metals Processing Centre (MMPC). The objective of the study was to investigate the effectiveness of microbubbles in removing inclusions smaller than 50 μm, applying the principles and conditions previously researched using a smaller scale arrangement. Air was injected into a full-scale model of a ladle shroud (the connecting tube through which liquid steel flows into the tundish below). The model ladle shroud was fitted with twelve, laser-drilled orifices, so as to create microbubbles. The bubbles generated using different gas injection protocols were recorded using a high-speed camera, and the bubble images were postprocessed using the commercial software, ImageJ. With this newly designed ladle shroud, bubble sizes could be reduced dramatically, to as small as a 675 µm average diameter. A three-dimensional, CFD model simulation was developed, using parameters obtained from the corresponding water model experiments, in order to predict the behavior of these microbubbles within the tundish and their potential influence on flow patterns and inclusion float-out capability.
  • Journal article
    Oluleye G, Smith R, 2016,

    A mixed integer linear programming model for integrating thermodynamic cycles for waste heat exploitation in process sites

    , Applied Energy, Vol: 178, Pages: 434-453, ISSN: 0306-2619

    © 2016 Elsevier Ltd Thermodynamic cycles such as organic Rankine cycles, absorption chillers, absorption heat pumps, absorption heat transformers, and mechanical heat pumps are able to utilize wasted thermal energy in process sites for the generation of electrical power, chilling and heat at a higher temperature. In this work, a novel systematic framework is presented for optimal integration of these technologies in process sites. The framework is also used to assess the best design approach for integrating waste heat recovery technologies in process sites, i.e. stand-alone integration or a systems-oriented integration. The developed framework allows for: (1) selection of one or more waste heat sources (taking into account the temperatures and thermal energy content), (2) selection of one or more technology options and working fluids, (3) selection of end-uses of recovered energy, (4) exploitation of interactions with the existing site utility system and (5) the potential for heat recovery via heat exchange is also explored. The methodology is applied to an industrial case study. Results indicate a systems-oriented design approach reduces waste heat by 24%; fuel consumption by 54% and CO2 emissions by 53% with a 2 year payback, and stand-alone design approach reduces waste heat by 12%; fuel consumption by 29% and CO2 emissions by 20.5% with a 4 year payback. Therefore, benefits from waste heat utilization increase when interactions between the existing site utility system and the waste heat recovery technologies are explored simultaneously. The case study also shows that the novel methodology can select and design optimal solutions for waste heat exploitation which are technically, economically and environmentally feasible from a range of technology options, heat sources and end-uses of recovered energy.
  • Journal article
    Oluleye G, Johnson M, Smith R, 2016,

    Process integration of waste heat upgrading technologies

    , Process Safety and Environmental Protection, Vol: 103, Pages: 315-333, ISSN: 0957-5820

    © 2016 The Institution of Chemical Engineers Technologies such as mechanical heat pumps, absorption heat pumps and absorption heat transformers allow low-temperature waste heat to be upgraded to higher temperatures. This work develops a comprehensive Mixed Integer Linear Program (MILP) to integrate such technologies into existing process sites. The framework considers interactions with the associated cogeneration system (in order to exploit end-uses of upgraded heat within the system and determine their true value), temperature and quantity of waste heat sources and of sinks for the heat upgraded as well as process economics and the potential to reduce carbon dioxide (CO2) emissions. The methodology is applied to an industrially relevant case study. Integration of heat upgrading technologies has potential to reduce total costs by 23%. Sensitivity analysis is also performed to illustrate the effect of changing capital costs and energy prices on the results, and demonstrate the model functionality.

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