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  • Journal article
    Bertei A, Ruiz-Trejo E, Tariq F, Yufit V, Atkinson A, Brandon NPet al., 2016,

    Validation of a physically-based solid oxide fuel cell anode model combining 3D tomography and impedance spectroscopy

    , International Journal of Hydrogen Energy, Vol: 41, Pages: 22381-22393, ISSN: 1879-3487

    This study presents a physically-based model for the simulation of impedance spectra in solid oxide fuel cell (SOFC) composite anodes. The model takes into account the charge transport and the charge-transfer reaction at the three-phase boundary distributed along the anode thickness, as well as the phenomena at the electrode/electrolyte interface and the multicomponent gas diffusion in the test rig. The model is calibrated with experimental impedance spectra of cermet anodes made of nickel and scandia-stabilized zirconia and satisfactorily validated in electrodes with different microstructural properties, quantified through focused ion beam SEM tomography. Besides providing the material-specific kinetic parameters of the electrochemical hydrogen oxidation, this study shows that the correlation between electrode microstructure and electrochemical performance can be successfully addressed by combining physically-based modelling, impedance spectroscopy and 3D tomography. This approach overcomes the limits of phenomenological equivalent circuits and is suitable for the interpretation of experimental data and for the optimisation of the electrode microstructure.

  • Journal article
    Zheng L, Hills TP, Fennell P, 2016,

    Phase evolution, characterisation, and performance of cement prepared in an oxy-fuel atmosphere

    , Faraday Discussions, Vol: 192, Pages: 113-124, ISSN: 1364-5498

    Cement manufacture is one of the major contributors (7-10%) to global anthropogenic CO2 emissions. Carbon capture and storage (CCS) has been identified as a vital technology for decarbonising the sector. Oxy-fuel combustion, involving burning fuel in a mixture of recycled CO2 and pure O2 instead of air, makes CO2 capture much easier. Since it combines a theoretically lower energy penalty with an increase in production, it is attractive as a CCS technology in cement plants. However, it is necessary to demonstrate that changes in the clinkering atmosphere do not reduce the quality of the clinker produced. Clinkers were successfully produced in an oxy-fuel atmosphere using only pure oxides as raw materials as well as a mixture of oxides and clay. Then, CEM I cements were prepared by the addition of 5 wt% gypsum to the clinkers. Quantitative XRD and XRF were used to obtain the phase and elemental compositions of the clinkers. The particle size distribution and compressive strength of the cements at 3, 7, 14, and 28 days' ages were tested, and the effect of the particle size distribution on the compressive strength was investigated. Additionally, the compressive strength of the cements produced in oxy-fuel atmospheres was compared with those of the cement produced in air and commercially available CEMEX CEM I. The results show that good-quality cement can be successfully produced in an oxy-fuel atmosphere and it has similar phase and chemical compositions to CEM I. Additionally, it has a comparable compressive strength to the cement produced in air and to commercially available CEMEX CEM I.

  • Journal article
    Smit B, Styring P, Wilson G, Rochelle G, Donat F, Yao J, Trusler M, Adjiman C, Lyth S, Lee J-SM, Hills T, Brandl P, Gazzani M, Cuellar-Franca R, Fennell P, Sutter D, Bui M, Scholes C, Dowson G, Gibbins J, Joss L, Maitland G, Brandani S, Garcia-Gutierrez P, Zhang Y, Muller C, Jackson G, Ocone R, Joos L, Bell R, Graham Ret al., 2016,

    Modelling - from molecules to megascale: general discussion

    , Faraday Discussions, Vol: 192, Pages: 493-509, ISSN: 1359-6640
  • Journal article
    Mac Dowell N, Fajardy M, 2016,

    On the potential for BECCS efficiency improvement through heat recovery from both post-combustion and oxy-combustion facilities

    , Faraday Discussions, Vol: 192, Pages: 241-250, ISSN: 1359-6640

    In order to mitigate climate change to no more than 2 °C, it is well understood that it will be necessary to directly remove significant quantities of CO2, with bioenergy CCS (BECCS) regarded as a promising technology. However, BECCS will likely be more costly and less efficient at power generation than conventional CCS. Thus, approaches to improve BECCS performance and reduce costs are of importance to facilitate the deployment of this key technology. In this study, the impact of biomass co-firing rate and biomass moisture content on BECCS efficiency with both post- and oxy-combustion CO2 capture technologies was evaluated. It was found that post-combustion capture BECCS (PCC-BECCS) facilities will be appreciably less efficient than oxy-combustion capture BECCS (OCC-BECCS) facilities. Consequently, PCC-BECCS have the potential to be more carbon negative than OCC-BECCS per unit electricity generated. It was further observed that the biomass moisture content plays an important role in determining the BECCS facilities’ efficiency. This will in turn affect the enthalpic content of the BECCS plant exhaust and implies that exhaust gas heat recovery may be an attractive option at higher rates of co-firing. It was found that there is the potential for the recovery of approximately 2.5 GJheat per tCO2 at a temperature of 100 °C from both PCC-BECCS and OCC-BECCS. On- and off-site applications for this recovered heat are discussed, considering boiler feedwater pre-heating, solvent regeneration and district heating cases.

  • Journal article
    De Kauwe MG, Keenan TF, Medlyn BE, Prentice IC, Terrer Cet al., 2016,

    CORRESPONDENCE: Satellite based estimates underestimate the effect of CO<sub>2</sub> fertilization on net primary productivity

    , NATURE CLIMATE CHANGE, Vol: 6, Pages: 892-893, ISSN: 1758-678X
  • Journal article
    Bridgestock L, van de Flierdt T, Rehkamper M, Paul M, Middag R, Milne A, Lohan MC, Baker AR, Chance R, Khondoker R, Strekopytov S, Humphreys-Williams E, Achterberg EP, Rijkenberg MJA, Gerringa LJA, de Baar HJWet al., 2016,

    Return of naturally sourced Pb to Atlantic surface waters

    , Nature Communications, Vol: 7, ISSN: 2041-1723

    Anthropogenic emissions completely overwhelmed natural marine Pb sources during the past century, predominantly due to leaded petrol usage. Here, based on Pb isotope measurements, we reassess the importance of natural and anthropogenic Pb sources to the tropical North Atlantic following the nearly complete global cessation of leaded petrol use. For the first time, significant proportions of up to 30 – 50% of natural Pb, derived from mineral dust, are observed in Atlantic surface waters, reflecting the success of the global effort to reduce anthropogenic Pb emissions. The observation of mineral dust derived Pb in surface waters is governed by the elevated atmospheric mineral dust concentration of the North African dust plume and the dominance of dry deposition for the atmospheric aerosol flux to surface waters. Given these specific regional conditions, emissions from anthropogenic activities will remain the dominant global marine Pb source, even in the absence of leaded petrol combustion.

  • Journal article
    Roberts J, Curran M, Poynter S, Moy A, van Ommen T, Vance T, Tozer C, Graham F, Young D, Plummer C, Pedro J, Blankenship D, Siegert Met al., 2016,

    Correlation confidence limits for unevenly sampled data

    , Computers & Geosciences, Vol: 104, Pages: 120-124, ISSN: 0098-3004

    Estimation of correlation with appropriate uncertainty limits for scientific data that are potentially serially correlated is a common problem made seriously challenging especially when data are sampled unevenly in space and/or time. Here we present a new, robust method for estimating correlation with uncertainty limits between autocorrelated series that does not require either resampling or interpolation. The technique employs the Gaussian kernel method with a bootstrapping resampling approach to derive the probability density function and resulting uncertainties. The method is validated using an example from radar geophysics. Autocorrelation and error bounds are estimated for an airborne radio-echo profile of ice sheet thickness. The computed limits are robust when withholding 10%, 20%, and 50% of data. As a further example, the method is applied to two time-series of methanesulphonic acid in Antarctic ice cores from different sites. We show how the method allows evaluation of the significance of correlation where the signal-to-noise ratio is low and reveals that the two ice cores exhibit a significant common signal.

  • Journal article
    De Kauwe MG, Keenan TF, Medlyn BE, Prentice IC, Terrer Cet al., 2016,

    Satellite based estimates underestimate the effect of CO2 fertilization on net primary productivity

    , Nature Climate Change, Vol: 6, Pages: 892-893, ISSN: 1758-678X
  • Journal article
    Jackson M, Weyl O, Altermatt F, Durance I, Friberg N, Dumbrell A, Piggott J, Tiegs S, Tockner K, Krug C, Leadley P, Woodward Get al., 2016,

    Chapter twelve - recommendations for the next generation of global freshwater biological monitoring tools

    , Advances in Ecological Research, Vol: 55, Pages: 615-636, ISSN: 0065-2504

    Biological monitoring has a long history in freshwaters, where much of the pioneering work in this field was developed over a hundred years ago – but few of the traditional monitoring tools provide the global perspective on biodiversity loss and its consequences for ecosystem functioning that are now needed. Rather than forcing existing monitoring paradigms to respond to questions they were never originally designed to address, we need to take a step back and assess the prospects for novel approaches that could be developed and adopted in the future. To resolve some of the issues with indicators currently used to inform policymakers, we highlight new biological monitoring tools that are being used, or could be developed in the near future, which (1) consider less-studied taxonomic groups; (2) are standardised across regions to allow global comparisons, and (3) measure change over multiple time points. The new tools we suggest make use of some of the key technological and logistical advances seen in recent years – including remote sensing, molecular tools, and local-to-global citizen science networks. We recommend that these new indicators should be considered in future assessments of freshwater ecosystem health and contribute to the evidence base for global to regional (and national) assessments of biodiversity and ecosystem services: for example, within the emerging framework of the Intergovernmental Platform on Biodiversity and Ecosystem Services.

  • Journal article
    Valerio L, North A, Collins CM, Mumford JD, Facchinelli L, Spaccapelo R, Benedict MQet al., 2016,

    Comparison of Model Predictions and Laboratory Observations of Transgene Frequencies in Continuously-Breeding Mosquito Populations.

    , Insects, Vol: 7, ISSN: 2075-4450

    The persistence of transgenes in the environment is a consideration in risk assessments of transgenic organisms. Combining mathematical models that predict the frequency of transgenes and experimental demonstrations can validate the model predictions, or can detect significant biological deviations that were neither apparent nor included as model parameters. In order to assess the correlation between predictions and observations, models were constructed to estimate the frequency of a transgene causing male sexual sterility in simulated populations of a malaria mosquito Anopheles gambiae that were seeded with transgenic females at various proportions. Concurrently, overlapping-generation laboratory populations similar to those being modeled were initialized with various starting transgene proportions, and the subsequent proportions of transgenic individuals in populations were determined weekly until the transgene disappeared. The specific transgene being tested contained a homing endonuclease gene expressed in testes, I-PpoI, that cleaves the ribosomal DNA and results in complete male sexual sterility with no effect on female fertility. The transgene was observed to disappear more rapidly than the model predicted in all cases. The period before ovipositions that contained no transgenic progeny ranged from as little as three weeks after cage initiation to as long as 11 weeks.

  • Journal article
    Rezaei F, Safavi HR, Mirchi A, Madani Ket al., 2016,

    f-MOPSO: an alternative multi-objective PSO algorithm for conjunctive water use management

    , Journal of Hydro-Environment Research, Vol: 14, Pages: 1-18, ISSN: 1876-4444

    In recent years, evolutionary techniques have been widely used to search for the global optimum of combinatorial non-linear non-convex problems. In this paper, we present a new algorithm, named fuzzy Multi-Objective Particle Swarm Optimization (f-MOPSO) to improve conjunctive surface water and groundwater management. The f-MOPSO algorithm is simple in concept, easy to implement, and computationally efficient. It is based on the role of weighting method to define partial performance of each point (solution) in the objective space. The proposed algorithm employs a fuzzy inference system to consider all the partial performances for each point when optimizing the objective function values. The f-MOPSO algorithm was compared with two other well-known MOPSOs through a case study of conjunctive use of surface and groundwater in Najafabad Plain in Iran considering two management models, including a typical 12-month operation period and a 10-year planning horizon. Overall, the f-MOPSO outperformed the other MOPSO algorithms with reference to performance criteria and Pareto-front analysis while nearly fully satisfying water demands with least monthly and cumulative groundwater level (GWL) variation. The proposed algorithm is capable of finding the unique optimal solution on the Pareto-front to facilitate decisions to address large-scale optimization problems.

  • Journal article
    Mellor AV, Hylton N, Maier S, Ekins-Daukes Net al., 2016,

    Interstitial light-trapping design for multi-junction solar cells

    , Solar Energy Materials and Solar Cells, Vol: 159, Pages: 212-218, ISSN: 0927-0248

    We present a light-trapping design capable of significantly enhancing the photon absorption inany subcell of a multi-junction solar cell. The design works by coupling incident light intowaveguide modes in one of the subcells via a diffraction grating, and preventing these modesfrom leaking into lower subcells via a low-index layer and a distributed Bragg reflector, whichtogether form an omnidirectional mirror. This allows the thickness of the target subcell to bereduced without compromising photon absorption, which improves carrier collection, andtherefore photocurrent. The paper focuses on using the composite structure to improve theradiation hardness of a InGaP/Ga(In)As/Ge space solar cell. In this context, it is shown viasimulation that the Ga(In)As middle-cell thickness can be reduced from 3500 to 700 nm,whilst maintaining strong photon absorption, and that this leads to a significantly improvedend-of-life photocurrent in the Ga(In)As middle cell. However, the design can in general beapplied to a wide range of multi-junction solar cell types. We discuss the principles ofoperation of the design, as well as possible methods of its fabrication and integration intomulti-junction solar cells.

  • Journal article
    Parfitt R, Russell JE, Bantges RJ, Clerbaux N, Brindley HEet al., 2016,

    A study of the time evolution of GERB shortwave calibration by comparison with CERES Edition-3A data

    , Remote Sensing of Environment, Vol: 186, Pages: 416-427, ISSN: 0034-4257

    This study examines the evolution of the GERB-2 and GERB-1 Edition 1 shortwave radiance calibration between 2004-2007 and 2007-2012 respectively, through comparison with CERES instrument FM1 Edition 3A SSF instantaneous radiances. Two periods when simultaneous observations from both GERB-2 and GERB-1 were available, January 13th to February 11th 2007 and May 1st to May 10th 2007, are also compared. For these two overlap periods respectively, averaged over all CERES ‘unfiltered-to-filtered radiance ratio’ subsets, the GERB-1/CERES unfiltered radiance ratio is on average found to be 1.6% and 1.9% lower than the associated GERB-2/CERES unfiltered radiance ratio. Over the two longer time series the GERB/CERES unfiltered radiance ratio shows a general decrease with time for both GERB-2 and GERB-1. The rate of decrease varies through time but no significant seasonal dependence is seen. Averaged over all subsets the GERB-2/CERES unfiltered radiance ratio showed a decrease of 1.9% between June 2004 and June 2006. Between June 2007 and June 2012, the corresponding decrease in the GERB-1/CERES unfiltered radiance ratio was 6.5%. The evolution of the GERB/CERES unfiltered radiance ratio for both GERB-2 and GERB-1 shows a strong dependence on the CERES unfiltered-to-filtered radiance ratio, indicating that it is spectrally dependent. Further time-series analysis and theoretical work using simulated spectral radiance curves suggests that for GERB-1 the evolution is consistent with a darkening in the GERB shortwave spectral response function which is most pronounced at the shortest wavelengths. For GERB-2, no single spectral cause can be identified, suggesting that the evolution is likely due to a combination of several different effects.

  • Journal article
    Zhang JJ, Lee KB, He L, Seiffert J, Subramaniam P, Yang L, Chen S, Maguire P, Mainelis G, Schwander S, Tetley T, Porter A, Ryan M, Shaffer M, Hu S, Gong J, Chung KFet al., 2016,

    Effects of a nanoceria fuel additive on the physicochemical properties of diesel exhaust particles.

    , Environmental Science: Processes & Impacts, Vol: 18, Pages: 1333-1342, ISSN: 2050-7887

    Nanoceria (i.e., CeO2 nanoparticles) fuel additives have been used in Europe and elsewhere to improve fuel efficiency. Previously we have shown that the use of a commercial fuel additive Envirox™ in a diesel-powered electricity generator reduced emissions of diesel exhaust particle (DEP) mass and other pollutants. However, such additives are currently not permitted for use in on-road vehicles in North America, largely due to limited data on the potential health impact. In this study, we characterized a variety of physicochemical properties of DEPs emitted from the same engine. Our methods include novel techniques such as Raman spectrometry for analyzing particle surface structure and an assay for DEP oxidative potential. Results show that with increasing Envirox™ concentrations in the fuel (0×, 0.1×, 1×, and 10× of manufacturer recommended 0.5 mL Envirox™ per liter fuel), DEP sizes decreased from 194.6 ± 20.1 to 116.3 ± 14.8 nm; the zeta potential changed from -28.4 mV to -22.65 mV; DEP carbon content decreased from 91.8% to 79.4%; cerium and nitrogen contents increased from 0.3% to 6.5% and 0.2% to 0.6%, respectively; the ratio of organic carbon (OC) to elemental carbon (EC) increased from 22.9% to 38.7%; and the ratio of the disordered carbon structure to the ordered carbon structure (graphitized carbon) in DEPs decreased. Compared to DEPs emitted from 0×, 0.1×, and 1× fuels, DEPs from the 10× fuel had a lower oxidative potential likely due to the increased ceria content because pure ceria nanoparticles exhibited the lowest oxidative potential compared to all the DEPs. Since the physicochemical parameters tested here are among the determinants of particle toxicity, our findings imply that adding ceria nanoparticles into diesel may alter the toxicity of DEPs. The findings from the present study, hence, can help future studies that will examine the impact of nanoceria additives on DEP to

  • Journal article
    Grainger S, Mao F, Buytaert W, 2016,

    Environmental data visualisation for non-scientific contexts: Literature review and design framework

    , Environmental Modelling & Software, Vol: 85, Pages: 299-318, ISSN: 1364-8152

    Environmental science is an applied discipline, which therefore requires interacting with actors outside of the scientific community. Visualisations are increasingly seen as powerful tools to engage users with unfamiliar and complex subject matter. Despite recent research advances, scientists are yet to fully harness the potential of visualisation when interacting with non-scientists. To address this issue, we review the main principles of visualisation, discuss specific graphical challenges for environmental science and highlight some best practice from non-professional contexts. We provide a design framework to enhance the communication and application of scientific information within professional contexts. These guidelines can help scientists incorporate effective visualisations within improved dissemination and knowledge exchange platforms. We conclude that the uptake of science within environmental decision-making requires a highly iterative and collaborative design approach towards the development of tailored visualisations. This enables users to not only generate actionable understanding but also explore information on their own terms.

  • Book chapter
    Murray KA, Loh E, Nava A, Aguirre A, Daszak Pet al., 2016,


    , Tropical Conservation: Perspectives on Local and Global Priorities, Editors: Aguirre, Sukumar
  • Journal article
    Kroupa M, Offer GJ, Kosek J, 2016,

    Modelling of Supercapacitors: Factors Influencing Performance

    , Journal of the Electrochemical Society, Vol: 163, Pages: A2475-A2487, ISSN: 0013-4651

    The utilizable capacitance of Electrochemical Double Layer Capacitors (EDLCs) is a function of the frequency at which they are operated and this is strongly dependent on the construction and physical parameters of the device. We simulate the dynamic behavior of an EDLC using a spatially resolved model based on the porous electrode theory. The model of Verbrugge and Liu (J. Electrochem. Soc. 152, D79 (2005)) was extended with a dimension describing the transport into the carbon particle pores. Our results show a large influence of the electrode thickness (Le), separator thickness (Ls) and electrolyte conductivity (κ) on the performance of EDLCs. In agreement with experimental data, the time constant was an increasing function of Le and Ls and a decreasing function of κ. The main limitation was found to be on the scale of the whole cell, while transport into the particles became a limiting factor only if the particle size was unrealistically large. The results were generalized into a simplified relation allowing for a quick evaluation of performance for the design of new devices. This work provides an insight into the performance limitation of EDLCs and identifies the critical parameters to consider for both systems engineers and material scientists.

  • Journal article
    Hardin E, AghaKouchak A, Qomi MJA, Madani K, Tarroja B, Zhou Y, Yang T, Samuelsen Set al., 2016,

    California drought increases CO2 footprint of energy

    , SUSTAINABLE CITIES AND SOCIETY, Vol: 28, Pages: 450-452, ISSN: 2210-6707
  • Journal article
    Clough PT, Boot-Handford ME, Zhao M, Fennell PSet al., 2016,

    Degradation study of a novel polymorphic sorbent under realistic post-combustion conditions

    , Fuel, Vol: 186, Pages: 708-713, ISSN: 0016-2361

    Calcium looping is a Carbon Capture and Storage (CCS) technology which has the potential to be applied to both power generation plants and some industrial emission sources. The main problem with the use of calcium oxide-based sorbents is their characteristic decay in carrying capacity. This is caused by sintering and is made worse during multiple cycles of CO2 absorption (carbonation) and release (calcination). This paper provides an investigation into the degradation of a novel type of sorbent that is able to regenerate porosity during the temperature cycling of calcium looping. The porosity regeneration of this sorbent is a result of a dicalcium silicate additive undergoing a reliable phase change (α′ ↔ β), which consequently has a useful volume change associated with it. The sorbent here, has been tested for the first time under reasonably realistic conditions within a TGA for multiple cycles. The results demonstrated that the sorbent displays the characteristic decline in carrying capacity when calcined in the presence of CO2, but not when calcined in the absence of CO2 in the fluidising gas. This paper also presents an improved method to conduct TGA carrying capacity measurements of CO2 sorbents which minimises the over carbonation between cycles.

  • Journal article
    Chen C, Kamenkovich I, Berloff P, 2016,

    Eddy trains and striations in quasigeostrophic simulations and the ocean

    , Journal of Physical Oceanography, Vol: 46, Pages: 2807-2825, ISSN: 1520-0485

    This study explores the relationship between coherent eddies and zonally elongated striations. The investigation involves an analysis of two baroclinic quasigeostrophic models of a zonal and double-gyre flow and a set of altimetry sea level anomaly data in the North Pacific. Striations are defined by either spatiotemporal filtering or empirical orthogonal functions (EOFs), with both approaches leading to consistent results. Coherent eddies, identified here by the modified Okubo–Weiss parameter, tend to propagate along well-defined paths, thus forming “eddy trains” that coincide with striations. The striations and eddy trains tend to drift away from the intergyre boundary at the same speed in both the model and observations. The EOF analysis further confirms that these striations in model simulations and altimetry are not an artifact of temporal averaging of random, spatially uncorrelated vortices. This study suggests instead that eddies organize into eddy trains, which manifest themselves as striations in low-pass filtered data and EOF modes.

  • Journal article
    Cheng C, Yan L, Mirchi A, Madani Ket al., 2016,

    China's Booming Hydropower: Systems Modeling Challenges and Opportunities

  • Journal article
    Porter RTJ, Mahgerefteh H, Brown S, Martynov S, Collard A, Woolley RM, Fairweather M, Falle SAEG, Wareing CJ, Nikolaidis IK, Boulougouris GC, Peristeras LD, Tsangaris DM, Economou IG, Salvador C, Zanganeh K, Wigston A, Najafali JN, Shafeen A, Beigzadeh A, Farret R, Gombert P, Hebrard J, Proust C, Ceroni A, Flauw Y, Zhang Y, Chen S, Yu J, Talemi RH, Bensabat J, Wolf JL, Rebscher D, Niemi A, Jung B, Mac Dowell N, Shah N, Kolster C, Mechleri E, Krevor Set al., 2016,

    Techno-economic assessment of CO2 quality effect on its storage and transport: CO(2)QUEST An overview of aims, objectives and main findings

    , International Journal of Greenhouse Gas Control, Vol: 54, Pages: 662-681, ISSN: 1750-5836

    This paper provides an overview of the aims, objectives and the main findings of the CO2QUEST FP7 collaborative project, funded by the European Commission and designed to address the fundamentally important and urgent issues regarding the impact of the typical impurities in CO2 streams captured from fossil fuel power plants and other CO2 intensive industries on their safe and economic pipeline transportation and storage. The main features and results recorded from some of the unique test facilities constructed as part of the project are presented. These include an extensively instrumented realistic-scale test pipeline for conducting pipeline rupture and dispersion tests in China, an injection test facility in France to study the mobility of trace metallic elements contained in a CO2 stream following injection near a shallow-water qualifier and fluid/rock interactions and well integrity experiments conducted using a fully instrumented deep-well CO2/impurities injection test facility in Israel. The above, along with the various unique mathematical models developed, provide the fundamentally important tools needed to define impurity tolerance levels, mixing protocols and control measures for pipeline networks and storage infrastructure, thus contributing to the development of relevant standards for the safe design and economic operation of CCS.

  • Journal article
    Msowoya K, Madani K, Davtalab R, Mirchi A, Lund JRet al., 2016,

    Climate change impacts on maize production in the warm heart of Africa

    , Water Resources Management, Vol: 30, Pages: 5299-5312, ISSN: 1573-1650

    Agriculture is the mainstay of economy in Malawi - the warm heart ofAfrica. It employs 85 % of the labour force, and produces one third of the Gross Domestic Product (GDP) and 90 % of foreign exchange earnings. Maize farming covers over 92 % of Malawi’s agricultural land and contributes over 54 % of national caloric intake. With a subtropical climate and ~99 % rainfed agriculture, Malawi reliesheavily on precipitation for its agricultural production. Given the significance of rainfed maize for the nation’s labour force and GDP, we have investigated climatechange effects on this staple crop. We show that rainfed maize production in the Lilongwe District, the largest maize growing district in Malawi, may decrease up to 14 % by mid-century due to climate change, rising to as much as 33 % loss by the century’s end. These declines can substantially harm Malawi’s food production and socioeconomic status. Supplemental irrigation, crop diversification and natural conservation methods are promising adaptation strategies to improve Malawi’s food security and socioeconomic stability.

  • Journal article
    Ochoa-Tocachi B, Buytaert W, De Bièvre B, 2016,

    Regionalization of land-use impacts on streamflow using a network of paired catchments

    , Water Resources Research, Vol: 52, Pages: 6710-6729, ISSN: 1944-7973

    Quantifying the impact of land use and cover (LUC) change on catchment hydrological response is essential for land-use planning and management. Yet hydrologists are often not able to present consistent and reliable evidence to support such decision-making. The issue tends to be twofold: a scarcity of relevant observations, and the difficulty of regionalizing any existing observations. This study explores the potential of a paired catchment monitoring network to provide statistically robust, regionalized predictions of LUC change impact in an environment of high hydrological variability. We test the importance of LUC variables to explain hydrological responses and to improve regionalized predictions using 24 catchments distributed along the Tropical Andes. For this, we calculate first 50 physical catchment properties, and then select a subset based on correlation analysis. The reduced set is subsequently used to regionalize a selection of hydrological indices using multiple linear regression. Contrary to earlier studies, we find that incorporating LUC variables in the regional model structures increases significantly regression performance and predictive capacity for 66% of the indices. For the runoff ratio, baseflow index, and slope of the flow duration curve, the mean absolute error reduces by 53% and the variance of the residuals by 79%, on average. We attribute the explanatory capacity of LUC in the regional model to the pairwise monitoring setup, which increases the contrast of the land-use signal in the data set. As such, it may be a useful strategy to optimize data collection to support watershed management practices and improve decision-making in data-scarce regions.

  • Journal article
    Shevchenko I, Berloff P, 2016,

    Eddy Backscatter and Counter-Rotating Gyre Anomalies of Midlatitude Ocean Dynamics

    , Fluids, Vol: 1, ISSN: 2311-5521

    This work concerns how two competing mechanisms – eddy backscatter and2 counter-rotating gyre anomalies – influence the midlatitude ocean dynamics, as described by3 the eddy-resolving quasi-geostrophic (QG) model of wind-driven gyres. We analysed dynamical4 balances and effects of different eddy forcing components, as well as their dependencies on5 increasing vertical resolution and decreasing eddy viscosity and found that the eastward jet6 and its adjacent recirculation zones are maintained mostly by the eddy forcing via the eddy7 backscatter mechanism, whereas the time-mean eddy-forcing component plays not only direct8 jet-supporting but also indirect jet-inhibiting role. The latter is achieved by inducing zonally9 elongated anticyclonic/cyclonic Counter-rotating Gyre Anomaly (CGA) in the subpolar/subtropical10 gyre. The indirect effect of CGAs on the eastward jet is found to be moderate relative to the dominant11 eddy backscatter mechanism. We also found that the higher is the vertical baroclinic mode, the12 weaker is its backscatter role and the stronger is its CGA-driving role. Although the barotropic and13 first baroclinic modes are the most efficient ones in maintaining the backscatter, the higher, up to the14 fifth baroclinic modes also have significant but reverse impact that reduces the backscatter

  • Journal article
    Biton M, Yufit V, Tariq F, Kishimoto M, Brandon NPet al., 2016,

    Enhanced Imaging of Lithium Ion Battery Electrode Materials

    , Journal of the Electrochemical Society, Vol: 164, Pages: A6032-A6038, ISSN: 0013-4651

    In this study we present a novel method of lithium ion battery electrode sample preparation with a new type of epoxy impregnation,brominated (Br) epoxy, which is introduced here for the first time for this purpose and found suitable for focused ion beam scanningelectron microscope (FIB-SEM) tomography. The Br epoxy improves image contrast, which enables higher FIB-SEM resolution (3Dimaging), which is amongst the highest ever reported for composite LFP cathodes using FIB-SEM. In turn it means that the particlesare well defined and the size distribution of each phase can be analyzed accurately from the complex 3D electrode microstructureusing advanced quantification algorithms.The authors present for the first time a new methodology of contrast enhancement for 3D imaging, including novel advancedquantification, on a commercial Lithium Iron Phosphate (LFP) LiFePO4 cathode. The aim of this work is to improve the quality ofthe 3D imaging of challenging battery materials by developing methods to increase contrast between otherwise previously poorlydifferentiated phases. This is necessary to enable capture of the real geometry of electrode microstructures, which allows measurementof a wide range of microstructural properties such as pore/particle size distributions, surface area, tortuosity and porosity. Theseproperties play vital roles in determining the performance of battery electrodes.

  • Report
    Mechleri E, Staffell I, Lawal A, Ramos A, Shah N, Mac Dowell Net al., 2016,

    Evaluation of Process Control Strategies for Normal, Flexible and Upset Operation Conditions of CO2 Post Combustion Capture Processes

    , 2016/07

    This project focuses on performing an evaluation of process control strategies for normal and flexible operation conditions of CO2 post-combustion capture (PCC) processes. PCC is a promising, near-term technology for large-scale deployment for the decarbonisation of the power generation and other sectors. However, the integration of this technology imposes a well-known efficiency penalty on the power plant with which it is integrated. Once an optimal process design has been identified, this energy penalty can be somewhat reduced via application of an appropriate control strategy to the PCC plant. An appropriate process control strategy is also fundamental to guarantee the safety and feasibility of the process under flexible operating conditions that the power plants may be subject to.The aim of this project is to develop the process control strategy, to select appropriate control variables for a PCC process, and design efficient control structures for operation of a post-combustion capture process with minimum energy requirements for coal and natural gas power plants. The control structures are developed for power plant operating ranges of around 50% to 100% load.

  • Journal article
    von Srbik M-T, Marinescu M, Martinez-Botas RF, Offer GJet al., 2016,

    A physically meaningful equivalent circuit network model of a lithium-ion battery accounting for local electrochemical and thermal behaviour, variable double layer capacitance and degradation

    , Journal of Power Sources, Vol: 325, Pages: 171-184, ISSN: 0378-7753

    A novel electrical circuit analogy is proposed modellingelectrochemical systems under realistic automotive operation conditions. The model is developed for a lithium ion battery and is based on a pseudo 2D electrochemical model. Although cast in the framework familiar to application engineers, the model is essentially an electrochemical battery model: all variables have a direct physical interpretation and there is direct access to all states of the cell via the model variables (concentrations, potentials) for monitoring and control systems design. This is the first Equivalent Circuit Network-type model that tracks directly the evolution of species inside the cell. It accounts for complex electrochemical phenomena that are usually omitted in online battery performance predictors such as variable double layer capacitance, the full current-overpotential relation and overpotentials due to mass transport limitations. The coupled electrochemical and thermal model accounts for capacity fade via a loss in active species and for power fade via an increase in resistive solid electrolyte passivation layers at both electrodes. The model's capability to simulate cell behaviour under dynamic events is validated against test procedures, such as standard battery testing load cycles for current rates up to 20 C, as well as realistic automotive drive cycle loads.

  • Journal article
    Alberts G, Gurguc Z, Koutroumpis P, Martin R, Muuls M, Napp Tet al., 2016,

    Competition and norms: a self-defeating combination?

    , Energy Policy, Vol: 96, Pages: 504-523, ISSN: 1873-6777

    This paper investigates the effects of information feedback mechanisms on electricity and heating usage at a student hall of residence in London. In a randomised control trial, we formulate different treatments such as feedback information and norms, as well as prize competition among subjects. We show that information and norms lead to a sharp – more than 20% - reduction in overall energy consumption. Because participants do not pay for their energy consumption this response cannot be driven by cost saving incentives. Interestingly, when combining feedback and norms with a prize competition for achieving low energy consumption, the reduction effect – while present initially – disappears in the long run. This could suggest that external rewards reduce and even destroy intrinsic motivation to change behaviour.

  • Report
    Mechleri E, Rivotti P, Staffell I, Lawal A, Ramos A, Shah N, Mac Dowell Net al., 2016,

    Evaluation of Process Control Strategies for Normal, Flexible and Upset Operation Conditions of CO2 Post Combustion Capture Processes

    Mechleri E, Staffell I, Lawal A, Ramos A, Shah N, Mac Dowell Nclose, 2016, Evaluation of Process Control Strategies for Normal, Flexible and Upset Operation Conditions of CO2 Post Combustion Capture Processes, 2016/07

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