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  • Journal article
    Murray JE, Brindley HE, Bryant RG, Russell JE, Jenkins KF, Washington Ret al., 2016,

    Enhancing weak transient signals in SEVIRI false color imagery: Application to dust source detection in southern Africa

    , Journal of Geophysical Research: Atmospheres, Vol: 121, Pages: 10199-10219, ISSN: 2169-897X

    A method is described to significantly enhance the signature of dust events using observations from the Spinning Enhanced Visible and InfraRed Imager (SEVIRI). The approach involves the derivation of a composite clear-sky signal for selected channels on an individual time-step and pixel basis. These composite signals are subtracted from each observation in the relevant channels to enhance weak transient signals associated with either (a) low levels of dust emission, or (b) dust emissions with high salt or low quartz content. Different channel combinations, of the differenced data from the steps above, are then rendered in false color imagery for the purpose of improved identification of dust source locations and activity. We have applied this clear-sky difference (CSD) algorithm over three [globally significant] source regions in southern Africa: the Makgadikgadi Basin, Etosha Pan, and the Namibian and western South African coast. Case study analyses indicate three notable advantages associated with the CSD approach over established image rendering methods: (i) an improved ability to detect dust plumes, (ii) the observation of source activation earlier in the diurnal cycle, and (iii) an improved ability to resolve and pinpoint dust plume source locations.

  • Journal article
    Al-menhali A, Menke H, Blunt MJ, Krevor SCet al., 2016,

    Pore Scale Observations of Trapped CO2 in Mixed-Wet Carbonate Rock: Applications to Storage in Oil Fields

    , Environmental Science & Technology, Vol: 50, Pages: 10282-10290, ISSN: 0013-936X

    Geologic CO2 storage has been identified as a key to avoiding dangerous climate change. Storage in oil reservoirs dominates the portfolio of existing projects due to favorable economics. However, in an earlier related work (Al-Menhali and Krevor Environ. Sci. Technol. 2016, 50, 2727−2734), it was identified that an important trapping mechanism, residual trapping, is weakened in rocks with a mixed wetting state typical of oil reservoirs. We investigated the physical basis of this weakened trapping using pore scale observations of supercritical CO2 in mixed-wet carbonates. The wetting alteration induced by oil provided CO2-wet surfaces that served as conduits to flow. In situ measurements of contact angles showed that CO2 varied from nonwetting to wetting throughout the pore space, with contact angles ranging 25° < θ < 127°; in contrast, an inert gas, N2, was nonwetting with a smaller range of contact angle 24° < θ < 68°. Observations of trapped ganglia morphology showed that this wettability allowed CO2 to create large, connected, ganglia by inhabiting small pores in mixed-wet rocks. The connected ganglia persisted after three pore volumes of brine injection, facilitating the desaturation that leads to decreased trapping relative to water-wet systems.

  • Journal article
    Liu X, Wu B, Brandon NP, Wang Qet al., 2016,

    Tough ionogel-in-mask hybrid gel electrolytes in supercapacitors with durable pressure and thermal tolerances

    , Energy Technology, Vol: 5, Pages: 220-224, ISSN: 2194-4288

    A primary challenge of gel electrolytes in development of flexible and wearable devices is their weak mechanical performances, including their compressive stress, tensile strength, and puncture resistance. Here we prepare an ionogel-mask hybrid gel electrolyte, which successfully achieves synergic advantages of the high mechanical strength of the mask substance and the superior electrochemical and thermal characteristics of the ionogel. The fabricated supercapacitor can maintain a relatively stable capacitive performance even under a high pressure of 3236 kPa. Meanwhile, with the good thermal stability of the composite gel electrolyte, the solid-state supercapacitor can be operated at high temperatures ranging from 25 °C to 200 °C. The ionogel-mask hybrid gel can be superior tough gel electrolyte for solid-state flexible supercapacitors with durable advantages in both high temperatures and pressures.

  • Journal article
    Yu W, Yang Y, Graham N, 2016,

    Evaluation of ferrate as a coagulant aid/oxidant pretreatment for mitigating submerged ultrafiltration membrane fouling in drinking water treatment

    , Chemical Engineering Journal, Vol: 298, Pages: 234-242, ISSN: 1873-3212

    Although pre-coagulation can mitigate ultrafiltration (UF) membrane fouling in the treatment of surface waters for drinking water supply, biological activities (‘biofouling’) can induce a continuous increase in membrane fouling. To meet this challenge, potassium ferrate, K2FeO4, a combined oxidant and coagulant, was evaluated as a pre-treatment chemical for controlling submerged UF membrane fouling in water treatment. Ferrate use as an alternative to- (phase 1: ∼23 days), and in combination with- (phase 2: ∼30 days), conventional FeCl3, have been studied using parallel continuous bench-scale submerged membrane systems, using FeCl3 as the reference. The poorer performance of ferrate (alone) as a pre-treatment compared to FeCl3 (phase 1) was the result of a lower coagulation efficiency, which outweighed the beneficial impact of the ferrate on bacterial inactivation. The net reduction in pre-treatment performance led to an increase in the concentration of residual, active bacteria in the membrane tank, and bacteria associated large molecular weight (MW) organic substances, such as extracellular polymeric substances (EPS) or biopolymers, which were the principal cause of the higher rate of membrane fouling observed. In contrast, ferrate performed best as a coagulant aid/oxidant (FeCl3/K2FeO4) (phase 2), with the rate of membrane fouling (increase in transmembrane pressure) 4.5 times lower than conventional FeCl3 pre-treatment. This pre-treatment arrangement resulted in less bacteria (and EPS) and suspended solids in the membrane tank, and less accumulation of materials in the cake layer and within the membrane pores. The results indicated clearly the potential benefit of applying ferrate as a coagulant aid/oxidant with a coagulant, in UF pre-treatment, with the control of bacteria and EPS a key factor in reducing membrane fouling.

  • Journal article
    Allen RT, Hales NM, Baccarelli A, Jerrett M, Ezzati M, Dockery DW, Pope CAet al., 2016,

    Countervailing effects of income, air pollution, smoking, and obesity on aging and life expectancy: population-based study of U.S. Counties

    , Environmental Health, Vol: 15, ISSN: 1832-3367

    BackgroundIncome, air pollution, obesity, and smoking are primary factors associated with human health and longevity in population-based studies. These four factors may have countervailing impacts on longevity. This analysis investigates longevity trade-offs between air pollution and income, and explores how relative effects of income and air pollution on human longevity are potentially influenced by accounting for smoking and obesity.MethodsCounty-level data from 2,996 U.S. counties were analyzed in a cross-sectional analysis to investigate relationships between longevity and the four factors of interest: air pollution (mean 1999–2008 PM2.5), median income, smoking, and obesity. Two longevity measures were used: life expectancy (LE) and an exceptional aging (EA) index. Linear regression, generalized additive regression models, and bivariate thin-plate smoothing splines were used to estimate the benefits of living in counties with higher incomes or lower PM2.5. Models were estimated with and without controls for smoking, obesity, and other factors.ResultsModels which account for smoking and obesity result in substantially smaller estimates of the effects of income and pollution on longevity. Linear regression models without these two variables estimate that a $1,000 increase in median income (1 μg/m3 decrease in PM2.5) corresponds to a 27.39 (33.68) increase in EA and a 0.14 (0.12) increase in LE, whereas models that control for smoking and obesity estimate only a 12.32 (20.22) increase in EA and a 0.07 (0.05) increase in LE. Nonlinear models and thin-plate smoothing splines also illustrate that, at higher levels of income, the relative benefits of the income-pollution tradeoff changed—the benefit of higher incomes diminished relative to the benefit of lower air pollution exposure.ConclusionsHigher incomes and lower levels of air pollution both correspond with increased human longevity. Adjusting for smoking and obesity reduces estimates of the benefi

  • Journal article
    Propp K, Marinescu M, Auger DJ, O'Neill L, Fotouhi A, Somasundaram K, Offer GJ, Minton G, Longo S, Wild M, Knap Vet al., 2016,

    Multi-temperature state-dependent equivalent circuit discharge model for lithium-sulfur batteries

    , Journal of Power Sources, Vol: 328, Pages: 289-299, ISSN: 1873-2755

    Lithium-sulfur (Li-S) batteries are described extensively in the literature, but existing computational models aimed at scientific understanding are too complex for use in applications such as battery management. Computationally simple models are vital for exploitation. This paper proposes a non-linear state-of-charge dependent Li-S equivalent circuit network (ECN) model for a Li-S cell under discharge. Li-S batteries are fundamentally different to Li-ion batteries, and require chemistry-specific models. A new Li-S model is obtained using a ‘behavioural’ interpretation of the ECN model; as Li-S exhibits a ‘steep’ open-circuit voltage (OCV) profile at high states-of-charge, identification methods are designed to take into account OCV changes during current pulses. The prediction-error minimization technique is used. The model is parameterized from laboratory experiments using a mixed-size current pulse profile at four temperatures from 10 °C to 50 °C, giving linearized ECN parameters for a range of states-of-charge, currents and temperatures. These are used to create a nonlinear polynomial-based battery model suitable for use in a battery management system. When the model is used to predict the behaviour of a validation data set representing an automotive NEDC driving cycle, the terminal voltage predictions are judged accurate with a root mean square error of 32 mV.

  • Journal article
    Fennell PS, Zhang Z, Hills T, Scott Set al., 2016,

    Spouted Bed Reactor for kinetic Measurements of Reduction of Fe2O3 in a CO2/CO Atmosphere Part I - Atmospheric Pressure Measurements and Equipment Commissioning

    , Chemical Engineering Research & Design, Vol: 114, Pages: 307-320, ISSN: 1744-3563

    A high pressure and high temperature spouted bed reactor, operating in fluidisation mode, has been designed and validated at low pressure for the study of gas-solid reaction kinetics. Measurements suggested the bed exhibited a fast rate of gas interchange between the bubble and particulate phases. Pressurised injection of the particles to the bottom of the bed allowed the introduction of solid reactants in a simple and controlled manner. The suitability of the reactor for the purpose of kinetic studies was demonstrated by investigation of the intrinsic kinetics of the initial stage of the reduction of Fe2O3 with CO over multiple cycles for chemical looping.Changes of pore structure over the initial cycles were found to affect the observed kinetics of the reduction. The initial intrinsic rate constant of the reduction reaction (ki) was measured by using a kinetic model which incorporated an effectiveness factor. The uncertainty arising from the measurement of particle porosity in the model was compensated for by the tortuosity factor. The average activation energy obtained for cycles three to five was 61 ± 8 kJ/mol, which is comparable with previous studies using both fluidised beds and thermogravimetry.

  • Journal article
    Gschwend FJ, Brandt A, Chambon CL, Tu WC, Weigand L, Hallett JPet al., 2016,

    Pretreatment of Lignocellulosic Biomass with Low-cost Ionic Liquids.

    , Jove-Journal of Visualized Experiments, Vol: 114, ISSN: 1940-087X

    A number of ionic liquids (ILs) with economically attractive production costs have recently received growing interest as media for the delignification of a variety of lignocellulosic feedstocks. Here we demonstrate the use of these low-cost protic ILs in the deconstruction of lignocellulosic biomass (Ionosolv pretreatment), yielding cellulose and a purified lignin. In the most generic process, the protic ionic liquid is synthesized by accurate combination of aqueous acid and amine base. The water content is adjusted subsequently. For the delignification, the biomass is placed into a vessel with IL solution at elevated temperatures to dissolve the lignin and hemicellulose, leaving a cellulose-rich pulp ready for saccharification (hydrolysis to fermentable sugars). The lignin is later precipitated from the IL by the addition of water and recovered as a solid. The removal of the added water regenerates the ionic liquid, which can be reused multiple times. This protocol is useful to investigate the significant potential of protic ILs for use in commercial biomass pretreatment/lignin fractionation for producing biofuels or renewable chemicals and materials.

  • Journal article
    Abolghasemi M, Piggott MD, Spinneken J, Vire A, Cotter CJ, Crammond Set al., 2016,

    Simulating tidal turbines with multi-scale mesh optimisation techniques

    , Journal of Fluids and Structures, Vol: 66, Pages: 69-90, ISSN: 1095-8622

    Embedding tidal turbines within simulations of realistic large-scale tidal flows is a highly multi-scale problem that poses significant computational challenges. Here this problem is tackled using actuator disc momentum (ADM) theory and Reynolds-averaged Navier-Stokes (RANS) with, for the first time, dynamically adaptive mesh optimisation techniques. Both k-ω and k-ω SST RANS models have been developed within the Fluidity framework, an adaptive mesh CFD solver, and the model is validated against two sets of experimental flume test results. A brief comparison against a similar OpenFOAM model is presented to portray the benefits of the finite element discretisation scheme employed in the Fluidity ADM model. This model has been developed with the aim that it will be seamlessly combined with larger numerical models simulating tidal flows in realistic domains. This is where the mesh optimisation capability is a major advantage as it enables the mesh to be refined dynamically in time and only in the locations required, thus making optimal use of limited computational resources.

  • Journal article
    Wu B, Parkes MP, de Benedetti L, Marquis AJ, Offer GJ, Brandon NPet al., 2016,

    Real-time monitoring of proton exchange membrane fuel cell stack failure

    , Journal of Applied Electrochemistry, Vol: 46, Pages: 1157-1162, ISSN: 1572-8838

    Uneven pressure drops in a 75-cell 9.5-kWe protonexchange membrane fuel cell stack with a U-shaped flowconfiguration have been shown to cause localised flooding.Condensed water then leads to localised cell heating, resultingin reduced membrane durability. Upon purging of the anodemanifold, the resulting mechanical strain on the membranecan lead to the formation of a pin-hole/membrane crack and arapid decrease in open circuit voltage due to gas crossover.This failure has the potential to cascade to neighbouring cellsdue to the bipolar plate coupling and the current densityheterogeneities arising from the pin-hole/membrane crack.Reintroduction of hydrogen after failure results in cell voltageloss propagating from the pin-hole/membrane crack locationdue to reactant crossover from the anode to the cathode, giventhat the anode pressure is higher than the cathode pressure.Through these observations, it is recommended that purging isavoided when the onset of flooding is observed to preventirreparable damage to the stack.

  • Journal article
    Boon M, Bijeljic B, Niu B, Krevor Set al., 2016,

    Observations of 3-D transverse dispersion and dilution in natural consolidated rock by X-ray tomography

    , Advances in Water Resources, Vol: 96, Pages: 266-281, ISSN: 0309-1708

    Recent studies have demonstrated the importance of transverse dispersion for dilution and mixing of solutes but most observations have remained limited to two-dimensional sand-box models. We present a new core-flood test to characterize solute transport in 3-D natural-rock media. A device consisting of three annular regions was used for fluid injection into a cylindrical rock core. Pure water was injected into the center and outer region and a NaI solution into the middle region. Steady state transverse dispersion of NaI was visualized with an X-ray medical CT-scanner for a range of Peclét numbers. Three methods were used to calculate Dt: (1) fitting an analytical solution, (2) analyzing the second-central moment, and (3) analyzing the dilution index and reactor ratio. Transverse dispersion decreased with distance due to flow focusing. Furthermore, Dt in the power-law regime showed sub-linear behavior. Overall, the reactor ratios were high confirming the homogeneity of Berea sandstone.

  • Journal article
    Mac Dowell N, Shah N, Staffell I, Heuberger Cet al., 2016,

    Quantifying the Value of CCS for the Future ElectricitySystem

    , Energy & Environmental Science, Vol: 9, Pages: 2497-2510, ISSN: 1754-5706

    Many studies have quantified the cost of Carbon Capture and Storage (CCS) power plants, butrelatively few discuss or appreciate the unique value this technology provides to the electricity system.CCS is routinely identified as a key factor in least-cost transitions to a low-carbon electricitysystem in 2050, one with significant value by providing dispatchable and low-carbon electricity.This paper investigates production, demand and stability characteristics of the current and futureelectricity system. We analyse the Carbon Intensity (CI) of electricity systems composed of unabatedthermal (coal and gas), abated (CCS), and wind power plants for different levels of windavailability with a view to quantifying the value to the system of different generation mixes. As athought experiment we consider the supply side of a UK-sized electricity system and compare theeffect of combining wind and CCS capacity with unabated thermal power plants. The resultingcapacity mix, system cost and CI are used to highlight the importance of differentiating betweenintermittent and firm low-carbon power generators. We observe that, in the absence of energystorage or demand side management, the deployment of intermittent renewable capacity cannotsignificantly displace unabated thermal power, and consequently can achieve only moderatereductions in overall CI. A system deploying sufficient wind capacity to meet peak demand canreduce CI from 0.78 tCO2/MWh, a level according to unabated fossil power generation, to 0.38tCO2/MWh. The deployment of CCS power plants displaces unabated thermal plants, and whilstit is more costly than unabated thermal plus wind, this system can achieve an overall CI of 0.1tCO2/MWh. The need to evaluate CCS using a systemic perspective in order to appreciate itsunique value is a core conclusion of this study.

  • Journal article
    Alonso Alvarez D, Ekins-Daukes N, 2016,

    SPICE modelling of photoluminescence and electroluminescence based current-voltage curves of solar cells for concentration applications

    , Journal of Green Engineering, Vol: 5, Pages: 33-48, ISSN: 2245-4586

    Quantitative photoluminescence (PL) or electroluminescence (EL) experiments can be usedto probe fast and in a non-destructive way the current-voltage (IV) characteristics ofindividual subcells in a multi-junction device, information that is, otherwise, not available.PL-based IV has the advantage that it is contactless and can be performed even in partlyfinished devices, allowing for an early diagnosis of the expected performance of the solarcells in the production environment. In this work we simulate the PL- and EL-based IVcurves of single junction solar cells to assess their validity compared with the true IV curveand identify injection regimes where artefacts might appear due to the limited in-planecarrier transport in the solar cell layers. We model the whole photovoltaic device as anetwork of sub-circuits, each of them describing the solar cell behaviour using the two diodemodel. The sub-circuits are connected to the neighbouring ones with a resistor, representingthe in-plane transport in the cell. The resulting circuit, involving several thousand subcircuits,is solved using SPICE.

  • Conference paper
    Mechleri E, fennell P, Mac Dowell N,

    Flexible operation strategies for coal- and gas-CCS power stations under the UK and USA markets

    , 13th Greenhouse Gas Control Technologies (GHGT) conference
  • Journal article
    Geen R, Czaja A, Haigh JD, 2016,

    The effects of increasing humidity on heat transport by extratropical waves

    , Geophysical Research Letters, Vol: 43, Pages: 8314-8321, ISSN: 1944-8007

    This study emphasizes the separate contributions of the warm and cold sectors of extratropical cyclones to poleward heat transport. Aquaplanet simulations are performed with an intermediate complexity climate model in which the response of the atmosphere to a range of values of saturation vapor pressure is assessed. These simulations reveal stronger poleward transport of latent heat in the warm sector as saturation vapor pressure is increased and an unexpected increase in poleward sensible heat transport in the cold sector. The latter results nearly equally from changes in the background stability of the atmosphere at low levels and changes in the temporal correlation between wind and temperature fields throughout the troposphere. Increased stability at low level reduces the likelihood that movement of cooler air over warmer water results in an absolutely unstable temperature profile, leading to less asymmetric damping of temperature and meridional velocity anomalies in cold and warm sectors.

  • Report
    Holt J, Leach A, Mumford JD, MacLeod A, Tomlinson D, Baker R, Christodoulou M, Russo L, Marechal Aet al., 2016,

    Development of probabilistic models for quantitative pathway analysis of plant pest introduction for the EU territory

    , Parma, Italy, Publisher: European Food Safety Authority, 2016:EN-1062

    This report demonstrates a probabilistic quantitative pathway analysis model that can be used in risk assessment for plant pest introduction into EU territory on a range of edible commodities (apples, oranges, stone fruits and wheat). Two types of model were developed: a general commodity model that simulates distribution of an imported infested/infected commodity to and within the EU from source countries by month; and a consignment model that simulates the movement and distribution of individual consignments from source countries to destinations in the EU. The general pathway model has two modules. Module 1 is a trade pathway model, with a Eurostat database of five years of monthly trade volumes for each specific commodity into the EU28 from all source countries and territories. Infestation levels based on interception records, commercial quality standards or other information determine volume of infested commodity entering and transhipped within the EU. Module 2 allocates commodity volumes to processing, retail use and waste streams and overlays the distribution onto EU NUTS2 regions based on population densities and processing unit locations. Transfer potential to domestic host crops is a function of distribution of imported infested product and area of domestic production in NUTS2 regions, pest dispersal potential, and phenology of susceptibility in domestic crops. The consignment model covers the several routes on supply chains for processing and retail use. The output of the general pathway model is a distribution of estimated volumes of infested produce by NUTS2 region across the EU28, by month or annually; this is then related to the accessible susceptible domestic crop. Risk is expressed as a potential volume of infested fruit in potential contact with an area of susceptible domestic host crop. The output of the consignment model is a volume of infested produce retained at each stage along the specific consignment trade chain.

  • Journal article
    Jaligot R, Wilson DC, Cheeseman CR, Shaker B, Stretz Jet al., 2016,

    Applying value chain analysis to informal sector recycling: A case study of the Zabaleen

    , Resources, Conservation and Recycling, Vol: 114, Pages: 80-91, ISSN: 0921-3449

    A methodology has been developed to apply value chain analysis (VCA) to the informal recycling sector, and demonstrated using the Zabaleen in Cairo, Egypt as a case study. The VCA methodology provides a ‘toolkit’ comprising four stages. The first involves mapping the value chain and has been demonstrated using the recycling of polyethylene terephthalate (PET) bottles as the particular example. Stage 2 tabulates the value added at each step in the value chain; this has been demonstrated for different types of plastics as well as other recycled fractions. Stage 3 identifies and then applies a set of indicators for the development of the informal sector recycling value chain in order to address technical and socio-economic challenges. The indicators proposed are in three categories: connections in the value chain, waste valorisation and the enabling environment. Stage 4 involves developing a system dynamic map that shows connections between the indicators, and the stocks and flow variables in the value chain. In particular, it identifies the most highly connected indicators on which to focus interventions, as these are likely to have the greatest impact on the overall system. For the Zabaleen, these are improving the quality of waste inputs into the value chain through source segregation, optimising access to waste and upgrading recycling activities through access to finance and technical knowledge.

  • Journal article
    Gray CL, Hill SLL, Newbold T, Hudson LN, Borger L, Contu S, Hoskins AJ, Ferrier S, Purvis A, Scharlemann JPWet al., 2016,

    Local biodiversity is higher inside than outside terrestrial protected areas worldwide

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

    Protected areas are widely considered essential for biodiversity conservation. However, few global studies have demonstrated that protection benefits a broad range of species. Here, using a new global biodiversity database with unprecedented geographic and taxonomic coverage, we compare four biodiversity measures at sites sampled in multiple land uses inside and outside protected areas. Globally, species richness is 10.6% higher and abundance 14.5% higher in samples taken inside protected areas compared with samples taken outside, but neither rarefaction-based richness nor endemicity differ significantly. Importantly, we show that the positive effects of protection are mostly attributable to differences in land use between protected and unprotected sites. Nonetheless, even within some human-dominated land uses, species richness and abundance are higher in protected sites. Our results reinforce the global importance of protected areas but suggest that protection does not consistently benefit species with small ranges or increase the variety of ecological niches.

  • Journal article
    Omoruyi U, Page S, Hallett J, Miller PWet al., 2016,

    Homogeneous Catalyzed Reactions of Levulinic Acid: To γ-Valerolactone and Beyond

    , Chemsuschem, Vol: 9, Pages: 2037-2047, ISSN: 1864-564X

    Platform chemicals derived from lignocellulosic plant biomass are viewed as a sustainable replacement for crude oil-based feedstocks. Levulinic acid (LA) is one such biomass-derived chemical that has been widely studied for further catalytic transformation to γ-valerolactone (GVL), an important ‘green’ fuel additive, solvent, and fine chemical intermediate. Although the transformation of LA to GVL can be achieved using heterogeneous catalysis, homogeneous catalytic systems that operate under milder reactions, give higher selectivities and can be recycled continuously are attracting considerable attention. A range of new homogeneous catalysts have now been demonstrated to efficiently convert LA to GVL and to transform LA directly to other value-added chemicals such as 1,4-pentanediol (1,4-PDO) and 2-methyltetrahydrofuran (2-MTHF). This Minireview covers recent advances in the area of homogeneous catalysis for the conversion of levulinic acid and levulinic ester derivatives to GVL and chemicals beyond GVL.

  • Journal article
    Alhajaj A, Mac Dowell N, Shah N, 2016,

    A techno-economic analysis of post-combustion CO2 capture and compression applied to a combined cycle gas turbine: Part II. Identifying the cost-optimal control and design variables

    , International Journal of Greenhouse Gas Control, Vol: 52, Pages: 331-343, ISSN: 1750-5836

    A detailed optimization-orientated model of monoethanolamine-based CO2 capture plant and compression train in which all the technical and economic assumptions are defined and/or optimized was developed and used to simultaneously determine the cost optimal control and design variables including feed fraction ratio at different degrees of capture (DOC), which represents the amount of CO2 removed, for plant designs that partially bypass the CO2 capture process so as to achieve low to moderate reductions of CO2, but at lower overall cost. The effects of varying carbon prices on the levelized cost of CO2 capture and compression were also studied. The capture bypass option was observed to be the cost optimal choice for lower than 60% overall DOC. Carbon prices were observed to have a clear impact on the cost optimal DOC, with the cost-optimal DOC shifting from 70%–80% to 85%–90% at carbon prices of $4/tCO2to $23/tCO2 respectively. The study highlighted that if a suitably high carbon price does not materialize through a market mechanism, appropriate policies need to be put in place to achieve decarbonisation targets.

  • Conference paper
    Fu H, Cao K, Xu R, Bhouri MA, Martinez-Botas R, Kim S-G, Yeatman EMet al., 2016,

    Footstep energy harvesting using heel strike-induced airflow for human activity sensing

    , 13th IEEE International Conference on Wearable and Implantable Body Sensor Networks (BSN), Publisher: IEEE, Pages: 124-129, ISSN: 2376-8886

    Body sensor networks are increasingly popular in healthcare, sports, military and security. However, the power supply from conventional batteries is a key bottleneck for the development of body condition monitoring. Energy harvesting from human motion to power wearable or implantable devices is a promising alternative. This paper presents an airflow energy harvester to harness human motion energy from footsteps. An air bladder-turbine energy harvester is designed to convert the footstep motion into electrical energy. The bladders are embedded in shoes to induce airflow from foot-strikes. The turbine is employed to generate electrical energy from airflow. The design parameters of the turbine rotor, including the blade number and the inner diameter of the blades (the diameter of the turbine shaft), were optimized using the computational fluid dynamics (CFD) method. A prototype was developed and tested with footsteps from a 65 kg person. The peak output power of the harvester was first measured for different resistive loads and showed a maximum value of 90.6 mW with a 30.4 Ω load. The harvested energy was then regulated and stored in a power management circuit. 14.8 mJ was stored in the circuit from 165 footsteps, which means 90 μJ was obtained per footstep. The regulated energy was finally used to fully power a fitness tracker which consists of a pedometer and a Bluetooth module. 7.38 mJ was consumed by the tracker per Bluetooth configuration and data transmission. The tracker operated normally with the harvester working continuously.

  • Journal article
    Jordan T, Bamber J, Williams C, Paden J, Siegert MJ, Huybrechts P, Gagliardini O, Gillet-Chaulet Fet al., 2016,

    An ice sheet wide framework for radar-inference of englacial attenuation and basal reflection with application to Greenland

    , Cryosphere, Vol: 10, Pages: 1547-1570, ISSN: 1994-0424

    Radar inference of the bulk properties of glacierbeds, most notably identifying basal melting, is, in general,derived from the basal reflection coefficient. On the scale ofan ice sheet, unambiguous determination of basal reflectionis primarily limited by uncertainty in the englacial attenuationof the radio wave, which is an Arrhenius function oftemperature. Existing bed-returned power algorithms for derivingattenuation assume that the attenuation rate is regionallyconstant, which is not feasible at an ice-sheet-wide scale.Here we introduce a new semi-empirical framework for derivingenglacial attenuation, and, to demonstrate its efficacy,we apply it to the Greenland Ice Sheet. A central featureis the use of a prior Arrhenius temperature model to estimatethe spatial variation in englacial attenuation as a firstguess input for the radar algorithm. We demonstrate regionsof solution convergence for two input temperature fields andfor independently analysed field campaigns. The coverageachieved is a trade-off with uncertainty and we propose thatthe algorithm can be “tuned” for discrimination of basal melt(attenuation loss uncertainty ∼ 5 dB). This is supported byour physically realistic (∼ 20 dB) range for the basal reflectioncoefficient. Finally, we show that the attenuation solutioncan be used to predict the temperature bias of thermomechanicalice sheet models and is in agreement with known modeltemperature biases at the Dye 3 ice core.

  • Journal article
    de Hoogh K, Gulliver J, van Donkelaar A, Martin RV, Marshall JD, Bechle MJ, Cesaroni G, Cirach Pradas M, Dedele A, Eeftens M, Forsberg B, Galassi C, Heinrich J, Hoffmann B, Jacquemin B, Katsouyanni K, Korek M, Kunzli N, Lindley SJ, Lepeule J, Meleux F, de Nazelle A, Nieuwenhuijsen M, Nystad W, Raaschou-Nielsen O, Peters A, Peuch V-H, Rouil L, Udvardy O, Slama R, Stempfelet M, Stephanou EG, Tsai MY, Yli-Tuomi T, Weinmayr G, Brunekreef B, Vienneau D, Hoek Get al., 2016,

    Development of West-European PM2.5 and NO2 land use regression models incorporating satellite-derived and chemical transport modelling data

    , ENVIRONMENTAL RESEARCH, Vol: 151, Pages: 1-10, ISSN: 0013-9351
  • Journal article
    Brant HL, Ewers RM, Vythilingam I, Drakeley C, Benedick S, Mumford JDet al., 2016,

    Vertical stratification of adult mosquitoes (Diptera: Culicidae) within a tropical rainforest in Sabah, Malaysia

    , Malaria Journal, Vol: 15, ISSN: 1475-2875

    BackgroundMalaria cases caused by Plasmodium knowlesi, a simian parasite naturally found in long-tailed and pig-tailed macaques, are increasing rapidly in Sabah, Malaysia. One hypothesis is that this increase is associated with changes in land use. A study was carried out to identify the anopheline vectors present in different forest types and to observe the human landing behaviour of mosquitoes. MethodsMosquito collections were carried out using human landing catches at ground and canopy levels in the Tawau Division of Sabah. Collections were conducted along an anthropogenic disturbance gradient (primary forest, lightly logged virgin jungle reserve and salvage logged forest) between 18:00-22:00h. ResultsAnopheles balabacensis, a vector of P. knowlesi, was the predominant species in all collection areas, accounting for 70% of the total catch, with a peak landing time of 18:30-20:00h. Anopheles balabacensis had a preference for landing on humans at ground level compared to the canopy (p<0.0001). A greater abundance of mosquitoes were landing in the logged forest compared to the primary forest (p<0.0001). There was no difference between mosquito abundance in the logged forest and lightly logged forest (p=0.554). A higher evening temperature (p<0.0001) and rainfall (p<0.0001) significantly decreased mosquito abundance during collection nights. ConclusionsThis study demonstrates the potential ability of An. balabacensis to transmit P. knowlesi between canopy-dwelling simian hosts and ground-dwelling humans, and that forest disturbance increases the abundance of this disease vector. These results, in combination with regional patterns of land use change, may partly explain the rapid rise in P. knowlesi cases in Sabah. This study provides essential data on anthropophily for the principal vector of P. knowlesi which is important for the planning of vector control strategies.

  • Journal article
    Le Quéré C, Buitenhuis ET, Moriarty R, Alvain S, Aumont O, Bopp L, Chollet S, Enright C, Franklin DJ, Geider RJ, Harrison SP, Hirst AG, Larsen S, Legendre L, Platt T, Prentice IC, Rivkin RB, Sailley S, Sathyendranath S, Stephens N, Vogt M, Vallina SMet al., 2016,

    Role of zooplankton dynamics for Southern Ocean phytoplankton biomass and global biogeochemical cycles

    , Biogeosciences, Vol: 13, Pages: 4111-4133, ISSN: 1726-4170

    Global ocean biogeochemistry models currently employed in climate change projections use highly simplified representations of pelagic food webs. These food webs do not necessarily include critical pathways by which ecosystems interact with ocean biogeochemistry and climate. Here we present a global biogeochemical model which incorporates ecosystem dynamics based on the representation of ten plankton functional types (PFTs): six types of phytoplankton, three types of zooplankton, and heterotrophic procaryotes. We improved the representation of zooplankton dynamics in our model through (a) the explicit inclusion of large, slow-growing macrozooplankton (e.g. krill), and (b) the introduction of trophic cascades among the three zooplankton types. We use the model to quantitatively assess the relative roles of iron vs. grazing in determining phytoplankton biomass in the Southern Ocean high-nutrient low-chlorophyll (HNLC) region during summer. When model simulations do not include macrozooplankton grazing explicitly, they systematically overestimate Southern Ocean chlorophyll biomass during the summer, even when there is no iron deposition from dust. When model simulations include a slow-growing macrozooplankton and trophic cascades among three zooplankton types, the high-chlorophyll summer bias in the Southern Ocean HNLC region largely disappears. Our model results suggest that the observed low phytoplankton biomass in the Southern Ocean during summer is primarily explained by the dynamics of the Southern Ocean zooplankton community, despite iron limitation of phytoplankton community growth rates. This result has implications for the representation of global biogeochemical cycles in models as zooplankton faecal pellets sink rapidly and partly control the carbon export to the intermediate and deep ocean.

  • Journal article
    Clancy ARJ, White E, Tay HH, Yau HC, Shafferet al., 2016,

    Systematic Comparison of Conventional and Reductive Single-walled Carbon Nanotube Purifications

    , Carbon, Vol: 108, Pages: 423-432, ISSN: 0008-6223

    As-synthesised single-walled carbon nanotubes (SWCNTs) are often contaminated withamorphous carbon and residual catalyst particles. These contaminants have a detrimental effecton the effective mechanical and electronic properties, limiting their performance in manyapplications. A comparative series of SWCNT purifications including acid treatments, gasphase purifications and recently-developed reductive purifications have been conducted usinga single commercial SWCNT type (Tuball™). Each of the purification procedures was selectedfor its potential scalability to bulk quantities and evaluated for the extent of impurity removal,SWCNT damage, and overall yield. Raman spectra confirmed that reductive purification usingsodium naphthalide gave the lowest D/G ratio, suggesting that the sp2carbon framework wasmost effectively preserved, while removing a large percentage of the metal impurities.Conversely, nitric acid treatment was most effective at removing catalytic impurities, but thesp2carbon framework was most heavily damaged in the process. The development of scalable,one pot, reductive separations provides a useful new approach to SWCNT purification.

  • Journal article
    Funke SW, Kramer SC, Piggott MD,

    Design optimisation and resource assessment for tidal-stream renewable energy farms using a new continuous turbine approach

    , Renewable Energy, ISSN: 1879-0682

    This paper presents a new approach for optimising the design of tidal stream turbine farms. In this approach, the turbine farm is represented by a turbine density function that specifies the number of turbines per unit area and an associated continuous locally-enhanced bottom friction field. The farm design question is formulated as a mathematical optimisation problem constrained by the shallow water equations and solved with efficient, gradient-based optimisation methods. The resulting method is accurate, computationally efficient, allows complex installation constraints, and supports different goal quantities such as to maximise power or profit. The outputs of the optimisation are the optimal number of turbines, their location within the farm, the overall farm profit, the farm's power extraction, and the installation cost.We demonstrate the capabilities of the method on a validated numerical model of the Pentland Firth, Scotland. We optimise the design of four tidal farms simultaneously, as well as individually, and study how farms in close proximity may impact upon one another.

  • Journal article
    Newbold T, Hudson LN, Arnell AP, Contu S, De Palma A, Ferrier S, Hill SLL, Hoskins A, Lysenko I, Phillips HRP, Burton VJ, Chng CWT, Emerson S, Gao D, Pask-Hale G, Hutton J, Jung M, Sanchez Ortiz K, Simmons BI, Whitmee S, Zhang H, Scharlemann JPW, Purvis A, Purvis Aet al., 2016,

    Has land use pushed terrestrial biodiversity beyond the planetary boundary? A global assessment

    , Science, Vol: 353, Pages: 288-291, ISSN: 0036-8075

    Land use and related pressures have reduced local terrestrial biodiversity, but it is unclear how the magnitude of change relates to the recently proposed planetary boundary (‘safe limit’). We estimate that land use and related pressures have already reduced local biodiversity intactness – the average proportion of natural biodiversity remaining in local ecosystems – beyond its recently-proposed planetary boundary across 58.1% of the world’s land surface, where 71.4% of the human population live. Biodiversity intactness within most biomes (especially grassland biomes), most biodiversity hotspots, and even some wilderness areas, is inferred to be beyond the boundary. Such widespread transgression of safe limits suggests that biodiversity loss, if unchecked, will undermine efforts towards long-term sustainable development.

  • Journal article
    Sandwell P, Duggan G, Nelson J, Ekins-Daukes Net al., 2016,

    The environmental impact of lightweight HCPV modules: efficient design and effective deployment

    , Progress in Photovoltaics, Vol: 24, Pages: 1458-1472, ISSN: 1099-159X

    We present a life cycle analysis of a lightweight design of high concentration photovoltaic module. The materials and processes used in construction are considered to assess the total environmental impact of the module construction in terms of the cumulative energy demand and embodied greenhouse gas emissions, which were found to be 355.3MJ and 27.9 kgCO2eq respectively. We consider six potential deployment locations and the system energy payback times are calculated to be 0.22–0.33 years whilst the greenhouse gas payback times are 0.29–0.88 years. The emission intensities over the life- times of the systems are found to be 6.5–9.8 g CO2eq/kWh, lower than those of other HCPV, PV and CSP technologies in similar locations.

  • Report
    Few SPM, Schmidt O, Gambhir A, 2016,

    Electrical energy storage for mitigating climate change

    , Publisher: Grantham Institute, Imperial College London, 20

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