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Journal articleBertei A, Tariq F, Yufit V, et al., 2016,
Guidelines for the rational design and engineering of 3D manufactured solid oxide fuel cell composite electrodes
, Journal of the Electrochemical Society, Vol: 164, Pages: F89-F98, ISSN: 0013-4651The growth of 3D printing has opened the scope for designing microstructures for solid oxide fuel cells(SOFCs) with improved power density and lifetime. This technique can introduce structural modifications at a scale larger than particle size but smaller than cell size, such as by insertingelectrolyte pillars of ~5-100 µm. This study sets the minimum requirements for the rational design of 3D printedelectrodes based on an electrochemical model and analytical solutions for functional layers with negligible electronic resistanceand no mixed conduction. Results show that this structural modification enhances the power density when the ratio keffbetween effective conductivity and bulk conductivity of the ionic phase is smaller than 0.5. The maximum performance improvement is predicted as a function of keff. A design study on a wide range of pillar shapes indicates that improvements are achieved by any structural modification which provides ionic conduction up to a characteristic thickness ~10-40 µm without removing active volume at the electrolyte interface. The best performance is reached for thin (< ~2 µm) and long (> ~80 µm) pillars when the compositeelectrode is optimised for maximum three-phase boundarydensity, pointing towards the design of scaffolds with well-defined geometry and fractal structures.
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Journal articleSiegert MJ, 2016,
Vulnerable Antarctic ice shelves
, Nature Climate Change, Vol: 7, Pages: 11-12, ISSN: 1758-6798Standfirst: The decay of floating ice shelves around Antarctica speeds up ice flow from the continent and enhances sea-level rise. Now meltwater attributed to warm winds has been discovered on an East Antarctic ice shelf, suggesting greater vulnerability than previously thought.
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Journal articleZekri S, Madani K, Bazargan-Lari MR, et al., 2016,
Feasibility of adopting smart water meters in aquifer management: An integrated hydro-economic analysis
, AGRICULTURAL WATER MANAGEMENT, Vol: 181, Pages: 85-93, ISSN: 0378-3774 -
Journal articleMadani K, AghaKouchak A, Mirchi A, 2016,
Iran’s socio-economic drought: challenges of a water-bankrupt nation
, Iranian Studies, Vol: 49, Pages: 997-1016, ISSN: 1475-4819Iran is currently experiencing serious water problems. Frequent droughts coupled with over-abstraction of surface and groundwater through a large network of hydraulic infrastructure and deep wells have escalated the nation’s water situation to a critical level. This is evidenced by drying lakes, rivers and wetlands, declining groundwater levels, land subsidence, water quality degradation, soil erosion, desertification and more frequent dust storms. This paper overviews the major drivers of Iran’s water problems. It is argued that while climatic changes and economic sanctions are commonly blamed as the main drivers of water problems, Iran is mainly suffering from a socio-economic drought—i.e. “water bankruptcy,” where water demand exceeds the natural water supply. In theory, this problem can be resolved by re-establishing the balance between water supply and demand through developing additional sources of water supply and implementing aggressive water demand reduction plans. Nevertheless, the current structure of the water governance system in Iran and the absence of a comprehensive understanding of the root causes of the problem leave minimal hope of developing sustainable solutions to Iran’s unprecedented water problems.
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Journal articleMuniina K, Maksimovic C, Graham N, 2016,
A novel approach for estimating urban water end use characteristics of cities in the developing world
, Urban Water Journal, Vol: 14, Pages: 750-757, ISSN: 1573-062XThe design of alternative urban water supply interventions for a community located in a low-income country requires detailed and precise knowledge of the nature, frequency and intensity of various characteristic water end-uses in the community. Without the availability of this characteristic water use information, high resolution metering experiments are the usually preferred methods to measure the water use volumes. However, in the developing world, these high resolution experiments are not an available option. Leaving the imprecise household interviewing process of data collection as the only option. This paper presents a novel methodology that improves and expands on the socially collected water uses data, through the use of a stochastic modelling process of the water use volumes to estimate the total monthly water use of the community. The methodology not only improves the estimates of water use volumes but also provides a mathematical modelling description of the household water uses in the community.
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Journal articleDehbi HM, Blangiardo M, Gulliver J, et al., 2016,
Air pollution and cardiovascular mortality with over 25 years follow-up: A combined analysis of two British cohorts
, Environment International, Vol: 99, Pages: 275-281, ISSN: 1873-6750BACKGROUND: Adverse effects of air pollution on cardiovascular disease (CVD) mortality are well established. There are comparatively fewer studies in Europe, and in the UK particularly, than in North America. We examined associations in two British cohorts with >25years of follow-up. METHODS: Annual average NO2, SO2 and black smoke (BS) air pollution exposure estimates for 1991 were obtained from land use regression models using contemporaneous monitoring data. From the European Study of Cohorts and Air Pollution (ESCAPE), air pollution estimates in 2010-11 were obtained for NO2, NOx, PM10, PMcoarse and PM2.5. The exposure estimates were assigned to place of residence 1989 for participants in a national birth cohort born in 1946, the MRC National Study of Health and Development (NSHD), and an adult multi-ethnic London cohort, Southall and Brent Revisited (SABRE) recruited 1988-91. The combined median follow-up was 26years. Single-pollutant competing risk models were employed, adjusting for individual risk factors. RESULTS: Elevated non-significant hazard ratios for CVD mortality were seen with 1991 BS and SO2 and with ESCAPE PM10 and PM2.5 in fully adjusted linear models. Per 10μg/m(3) increase HRs were 1.11 [95% CI: 0.76-1.61] for BS, 1.05 [95% CI: 0.91-1.22] for SO2, 1.16 [95% CI: 0.70-1.92] for PM10 and 1.30 [95% CI: 0.39-4.34] for PM2.5, with largest effects seen in the fourth quartile of BS and PM2.5 compared to the first with HR 1.24 [95% CI: 0.91-1.61] and 1.21 [95% CI: 0.88-1.66] respectively. There were no consistent associations with other ESCAPE pollutants, or with 1991 NO2. Modelling using Cox regression led to similar results. CONCLUSION: Our results support a detrimental long-term effect for air pollutants on cardiovascular mortality.
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Journal articleParkes MA, Tompsett DA, d'Avezac M, et al., 2016,
The atomistic structure of yttria stabilised zirconia at 6.7 mol%: an ab initio study.
, Physical Chemistry Chemical Physics, Vol: 18, Pages: 31277-31285, ISSN: 1463-9084Yttria stabilized zirconia (YSZ) is an important oxide ion conductor used in solid oxide fuel cells, oxygen sensing devices, and for oxygen separation. Doping pure zirconia (ZrO2) with yttria (Y2O3) stabilizes the cubic structure against phonon induced distortions and this facilitates high oxide ion conductivity. The local atomic structure of the dopant is, however, not fully understood. X-ray and neutron diffraction experiments have established that, for dopant concentrations below 40 mol% Y2O3, no long range order is established. A variety of local structures have been suggested on the basis of theoretical and computational models of dopant energetics. These studies have been restricted by the difficulty of establishing force field models with predictive accuracy or exploring the large space of dopant configurations with first principles theory. In the current study a comprehensive search for all symmetry independent configurations (2857 candidates) is performed for 6.7 mol% YSZ modelled in a 2 × 2 × 2 periodic supercell using gradient corrected density functional theory. The lowest energy dopant structures are found to have oxygen vacancy pairs preferentially aligned along the ⟨210⟩ crystallographic direction in contrast to previous results which have suggested that orientation along the ⟨111⟩ orientation is favourable. Analysis of the defect structures suggests that the Y(3+)-Ovac interatomic separation is an important parameter for determining the relative configurational energies. Current force field models are found to be poor predictors of the lowest energy structures. It is suggested that the energies from a simple point charge model evaluated at unrelaxed geometries is actually a better descriptor of the energy ordering of dopant structures. Using these observations a pragmatic procedure for identifying low energy structures in more complicated material models is suggested. Calculation of the oxygen vacancy migration activat
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Journal articleEzzati M, Baumgartner JC, 2016,
Household energy and health: where next for research and practice?
, Lancet, Vol: 389, Pages: 130-132, ISSN: 0140-6736 -
Journal articlePorter RTJ, Fairweather M, Kolster C, et al., 2016,
Cost and performance of some carbon capture technology options for producing different quality CO2 product streams
, International Journal of Greenhouse Gas Control, Vol: 57, Pages: 185-195, ISSN: 1750-5836A techno-economic assessment of power plants with CO2 capture technologies with a focus on process scenarios that deliver different grades of CO2 product purity is presented. The three leading CO2 capture technologies are considered, namely; oxyfuel combustion, pre-combustion and post-combustion capture. The study uses a combination of process simulation of flue gas cleaning processes, modelling with a power plant cost and performance calculator and literature values of key performance criteria in order to evaluate the performance, cost and CO2 product purity of the considered CO2 capture options. For oxyfuel combustion capture plants, three raw CO2 flue gas processing strategies of compression and dehydration only, double flash system purification and distillation purification are considered. Analysis of pre-combustion capture options is based on integrated gasification combined cycle plants using physical solvent systems for capturing CO2 and sulfur species via three routes; co-capture of sulfur impurities with the CO2 stream using Selexol™ solvent, separate capture of CO2 and sulfur impurities using Selexol™, and Rectisol® solvent systems for separate capture of sulfur impurities and CO2. Analysis of post-combustion capture plants was made with and without some conventional pollution control devices. The results highlight the wide variation in CO2 product purity for different oxyfuel combustion capture scenarios and the wide cost variation for the pre-combustion capture scenarios. The post-combustion capture plant with conventional pollution control devices offers high CO2 purity (99.99 mol%) for average cost of considered technologies. The calculations performed will be of use in further analyses of whole chain CCS for the safe and economic capture, transport and storage of CO2.
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Journal articleSchaeffer N, Grimes SM, Cheeseman CR, 2016,
Use of extraction chromatography in the recycling of critical metals from thin film Leach solutions
, Inorganica Chimica Acta, Vol: 457, Pages: 53-58, ISSN: 1873-3255Phosphors and optoelectronic thin film electronic device layers contain critical metals including lanthanides and indium that should be recycled. Solvent impregnated resins (SIRs) containing (i) DEHPA (ii) DODGAA and (iii) DODGAA with the ionic liquid [C4mim][Tf2N] are investigated in extraction chromatography methodologies to recover and separate critical metals from dilute solutions that model those leached from thin films. Optimum adsorption of metals occurs at pH 1.5-3.5 but is highest on DODGAA-[C4mim][Tf2N]. The recovery and separation of adsorbed metal species on the DODGAA-[C4mim][Tf2N] SIR resin from solutions containing the glass matrix ions, Ca(II) and Al(III), along with In(III) and Sn(IV) or lanthanide ions is achieved by elution with HNO3. Ca(II) and Al(III) are completely eluted with 0.1M HNO3 retaining the target critical metal species on the resin. Separation of In from Sn is achieved by elution of In(III) with 2.5M HNO3 and Sn(IV) with 5M acid. La is separated from the other lanthanides by elution of La(III) with 2.5M HNO3 and the remaining lanthanides with 5M acid. The SIR resins can be reused over a series of at least five cycles of loading,stripping, and rinsing to reduce reagent costs and achieve economic critical metal recovery byextraction chromatography.
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Journal articleRathgeber F, Ham DA, Mitchell L, et al., 2016,
Firedrake: Automating the finite element method by composing abstractions
, ACM Transactions on Mathematical Software, Vol: 43, ISSN: 0098-3500Firedrake is a new tool for automating the numerical solution of partial differential equations. Firedrake adopts the domain-specific language for the finite element method of the FEniCS project, but with a pure Python runtime-only implementation centered on the composition of several existing and new abstractions for particular aspects of scientific computing. The result is a more complete separation of concerns that eases the incorporation of separate contributions from computer scientists, numerical analysts, and application specialists. These contributions may add functionality or improve performance. Firedrake benefits from automatically applying new optimizations. This includes factorizing mixed function spaces, transforming and vectorizing inner loops, and intrinsically supporting block matrix operations. Importantly, Firedrake presents a simple public API for escaping the UFL abstraction. This allows users to implement common operations that fall outside of pure variational formulations, such as flux limiters.
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Journal articleChen SS, Sun Y, Tsang DC, et al., 2016,
Potential impact of flowback water from hydraulic fracturing on agricultural soil quality: metal/metalloid bioaccessibility, Microtox bioassay, and enzyme activities
, Science of the Total Environment, Vol: 579, Pages: 1419-1429, ISSN: 0048-9697Hydraulic fracturing has advanced the development of shale gas extraction, while inadvertent spills of flowback water may pose a risk to the surrounding environment due to its high salt content, metals/metalloids (As, Se, Fe and Sr), and organic additives. This study investigated the potential impact of flowback water on four representative soils from shale gas regions in Northeast China using synthetic flowback solutions. The compositions of the solutions were representative of flowback water arising at different stages after fracturing well establishment. The effects of solution composition of flowback water on soil ecosystem were assessed in terms of metal mobility and bioaccessibility, as well as biological endpoints using Microtox bioassay (Vibrio fischeri) and enzyme activity tests. After one-month artificial aging of the soils with various flowback solutions, the mobility and bioaccessibility of As(V) and Se(VI) decreased as the ionic strength of the flowback solutions increased. The results inferred a stronger binding affinity of As(V) and Se(VI) with the soils. Nevertheless, the soil toxicity to Vibrio fischeri only presented a moderate increase after aging, while dehydrogenase and phosphomonoesterase activities were significantly suppressed with increasing ionic strength of flowback solutions. On the contrary, polyacrylamide in the flowback solutions led to higher dehydrogenase activity. These results indicated that soil enzyme activities were sensitive to the composition of flowback solutions. A preliminary human health risk assessment related to As(V) suggested a low level of cancer risk through exposure via ingestion, while holistic assessment of environmental implications is required.
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Journal articlePrentice IC, Rogers A, Medlyn BE, et al., 2016,
A roadmap for improving the representation of photosynthesis in Earth system models
, New Phytologist, Vol: 213, Pages: 22-42, ISSN: 1469-8137Accurate representation of photosynthesis in terrestrial biosphere models (TBMs) is essential for robust projections of global change. However, current representations vary markedly between TBMs, contributing uncertainty to projections of global carbon fluxes. ● Here we compared the representation of photosynthesis in seven TBMs by examining leaf and canopy level responses of A to key environmental variables: light, temperature,carbon dioxide concentration, vapor pressure deficit and soil water content. ● We identified research areas where limited process knowledge prevents inclusion ofphysiological phenomena in current TBMs and research areas where data are urgently needed for model parameterization or evaluation.● We provide a roadmap for new science needed to improve the representation ofphotosynthesis in the next generation of terrestrial biosphere and Earth System Models.
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Journal articleMadani K, Pierce TW, Mirchi A, 2016,
Serious games on environmental management
, Sustainable Cities and Society, Vol: 29, Pages: 1-11, ISSN: 2210-6707Serious environmental management games can improve understanding of practical environmental sustainability challenges by offering opportunities to obtain first-hand experiences that may be otherwise too costly, difficult or dangerous to reproduce in reality. Game-based learning (GBL) has been found to increase soft skills, such as critical thinking, creative problem solving and teamwork, as well as to improve cognitive development, learning retention and social learning, which are important for future environmental researchers and professionals. Environmental management games can be applied in educational settings to promote awareness about sustainable resource planning and management among citizens who are increasingly exposed to products of the information age. This paper provides an overview of game-based learning and the state of serious games (SG) for environmental management, offering insight into their potential as effective tools in facilitating environmental education. SGs have been shown to possess numerous qualities that have been connected with improved learning experiences and cognitive development, but research must continue to study the SGs’ efficacy. Shortcomings found with games reviewed are that few evaluate or explain pedagogical foundation, and many are hard to implement or not accessible. Methods employed in determining the effectiveness of SGs vary greatly among environmental studies, necessitating a standardized methodology to reduce disparities in testing procedures. Furthermore, a centralized source, effectively an online database for SGs, is needed for locating and obtaining information pertaining to the available environmental games and their most appropriate applications.
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Journal articleBaran D, Ashraf RS, Hanifi DA, et al., 2016,
Reducing the efficiency-stability-cost gap of organic photovoltaics with highly efficient and stable small molecule acceptor ternary solar cells
, Nature Materials, Vol: 16, Pages: 363-369, ISSN: 1476-4660Technological deployment of organic photovoltaic modules requires improvements in device light-conversion efficiency and stability while keeping material costs low. Here we demonstrate highly efficient and stable solar cells using a ternary approach, wherein two non-fullerene acceptors are combined with both a scalable and affordable donor polymer, poly(3-hexylthiophene) (P3HT), and a high-efficiency, low-bandgap polymer in a single-layer bulk-heterojunction device. The addition of a strongly absorbing small molecule acceptor into a P3HT-based non-fullerene blend increases the device efficiency up to 7.7 ± 0.1% without any solvent additives. The improvement is assigned to changes in microstructure that reduce charge recombination and increase the photovoltage, and to improved light harvesting across the visible region. The stability of P3HT-based devices in ambient conditions is also significantly improved relative to polymer:fullerene devices. Combined with a low-bandgap donor polymer (PBDTTT-EFT, also known as PCE10), the two mixed acceptors also lead to solar cells with 11.0 ± 0.4% efficiency and a high open-circuit voltage of 1.03 ± 0.01 V.
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Journal articleRitson JP, Bell M, Brazier RE, et al., 2016,
Managing peatland vegetation for drinking water treatment
, Scientific Reports, Vol: 6, ISSN: 2045-2322Peatland ecosystem servicesinclude drinking water provision, flood mitigation, habitat provision and carbon sequestration. Dissolved organic carbon (DOC) removal is a key treatment process for the supply of potablewaterdownstream frompeat-dominated catchments. A transition from peat-forming Sphagnummoss to vascular plants has been observed in peatlands degraded by (a) land management, (b) atmospheric deposition and (c) climate change. Herewithinwe show that the presence of vascular plants with higherannual above-ground biomass productionleads to a seasonaladdition of labileplantmaterialinto the peatland ecosystemaslitter recalcitranceis lower. The net effect willbe asmaller litter carbon pool dueto higher rates of decomposition, and a greater seasonal pattern of DOC flux. Conventional water treatment involving coagulation-flocculation-sedimentation may be impeded byvascularplant-derivedDOC. It has been shown thatvascularplant-derived DOC is more difficult to remove via these methodsthan DOC derived from Sphagnum, whilst also being less susceptible to microbial mineralisation before reaching the treatment works. These results provide evidence that practices aimed at re-establishing Sphagnummoss on degraded peatlands could reduce costs and improve efficacy at water treatment works, offering an alternative to ‘end-of-pipe’ solutionsthrough management of ecosystem service provision.
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Journal articleManap N, Voulvoulis N, 2016,
Data analysis for environmental impact of dredging
, Journal of Cleaner Production, Vol: 137, Pages: 394-404, ISSN: 0959-6526The aim of this paper is twofold; first is to identify the environmental impact of dredging related to water and sediment quality; and second is to identify the main factors determining the environmental impact of dredging. The method of this research is data analysis using historical dredging data from three dredging projects performed from 2006 to 2008 at two connected rivers in Perak, Malaysia. The indices measured to identify the impact include: total suspended solids, dissolved oxygen, chemical oxygen demand, biochemical oxygen demand, pH, total organic content, iron, zinc, manganese, copper, chromium, mercury, arsenic, and lead. The factors are then identified through determination of relationships between concentration levels in sediment and water and identification of patterns of impact in the water and caged fish during dredging activities. The results of the analysis show that dredging performed in these rivers has an impact on the environment. The impact includes an increase in levels of most of the monitored indices, including dissolved oxygen and metal concentrations in highly contaminated areas. The main factors associated with the environmental impacts of dredging are the contamination level of the sediment and the contamination level of the neighbouring area, aspects that are the main scientific value added by this paper. This paper draws conclusions regarding the importance of two analyses prior to commencement of dredging: sediment quality analysis and analysis of contamination level in the neighbouring area prior to dredging. The results of this paper could help to better anticipate the environmental impact of dredging and allow for suitable mitigation measures to be identified, especially for developing countries such as Malaysia.
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Journal articleZulkafli Z, Perez K, Vitolo C, et al., 2016,
User-driven design of decision support systems for polycentric environmental resources management
, Environmental Modelling & Software, Vol: 88, Pages: 58-73, ISSN: 1364-8152Open and decentralized technologies such as the Internet provide increasing opportunities to create knowledge and deliver computer-based decision support for multiple types of users across scales. However, environmental decision support systems/tools (henceforth EDSS) are often strongly science-driven and assuming single types of decision makers, and hence poorly suited for more decentralized and polycentric decision making contexts. In such contexts, EDSS need to be tailored to meet diverse user requirements to ensure that it provides useful (relevant), usable (intuitive), and exchangeable (institutionally unobstructed) information for decision support for different types of actors. To address these issues, we present a participatory framework for designing EDSS that emphasizes a more complete understanding of the decision making structures and iterative design of the user interface. We illustrate the application of the framework through a case study within the context of water-stressed upstream/downstream communities in Lima, Peru.
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Journal articleWang H, Prentice IC, Davis TW, et al., 2016,
Photosynthetic responses to altitude: an explanation based on optimality principles
, New Phytologist, Vol: 213, Pages: 976-982, ISSN: 1469-8137 -
Journal articleChiong MS, Rajoo S, Romagnoli A, et al., 2016,
One-dimensional pulse-flow modeling of a twin-scroll turbine
, Energy, Vol: 115, Pages: 1291-1304, ISSN: 0360-5442This paper presents a revised one-dimensional (1D) pulse flow modeling of twin-scroll turbocharger turbine under pulse flow operating conditions. The proposed methodology in this paper provides further consideration for the turbine partial admission performance during model characterization. This gives rise to significant improvement on the model pulse flow prediction quality compared to the previous model. The results show that a twin-scroll turbine is not operating at full admission throughout the in-phase pulse flow conditions. Instead, they are operating at unequal admission state due to disparity in the magnitude of turbine inlet flow. On the other hand, during out-of-phase pulse flow, a twin-scroll turbine is working at partial admission state for majority of the pulse cycle. An amended mathematical correlation in calculating the twin-scroll turbine partial admission characteristics is also presented in the paper. The impact of its accuracy on the pulse flow model prediction is explored.
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Journal articleWatts N, Adger WN, Ayeb-Karlsson S, et al., 2016,
The Lancet Countdown: tracking progress on health and climate change
, The Lancet, Vol: 389, Pages: 1151-1164, ISSN: 0140-6736The Lancet Countdown: tracking progress on health and climate change is an international, multidisciplinary research collaboration between academic institutions and practitioners across the world. It follows on from the work of the 2015 Lancet Commission, which concluded that the response to climate change could be “the greatest global health opportunity of the 21st century”. The Lancet Countdown aims to track the health impacts of climate hazards; health resilience and adaptation; health co-benefits of climate change mitigation; economics and finance; and political and broader engagement. These focus areas form the five thematic working groups of the Lancet Countdown and represent different aspects of the complex association between health and climate change. These thematic groups will provide indicators for a global overview of health and climate change; national case studies highlighting countries leading the way or going against the trend; and engagement with a range of stakeholders. The Lancet Countdown ultimately aims to report annually on a series of indicators across these five working groups. This paper outlines the potential indicators and indicator domains to be tracked by the collaboration, with suggestions on the methodologies and datasets available to achieve this end. The proposed indicator domains require further refinement, and mark the beginning of an ongoing consultation process—from November, 2016 to early 2017—to develop these domains, identify key areas not currently covered, and change indicators where necessary. This collaboration will actively seek to engage with existing monitoring processes, such as the UN Sustainable Development Goals and WHO's climate and health country profiles. The indicators will also evolve over time through ongoing collaboration with experts and a range of stakeholders, and be dependent on the emergence of new evidence and knowledge. During the course of its work, the Lancet Countdown will ad
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Journal articleRead L, Madani K, Mokhtari S, et al., 2016,
Stakeholder-driven multi-attribute analysis for energy project selection under uncertainty
, Energy, Vol: 119, Pages: 744-753, ISSN: 0360-5442In practice, selecting an energy project for development requires balancing criteria and competing stakeholder priorities to identify the best alternative. Energy source selection can be modeled as multi-criteria decision-maker problems to provide quantitative support to reconcile technical, economic, environmental, social, and political factors with respect to the stakeholders' interests. Decision making among these complex interactions should also account for the uncertainty present in the input data. In response, this work develops a stochastic decision analysis framework to evaluate alternatives by involving stakeholders to identify both quantitative and qualitative selection criteria and performance metrics which carry uncertainties. The developed framework is illustrated using a case study from Fairbanks, Alaska, where decision makers and residents must decide on a new source of energy for heating and electricity. We approach this problem in a five step methodology: (1) engaging experts (role players) to develop criteria of project performance; (2) collecting a range of quantitative and qualitative input information to determine the performance of each proposed solution according to the selected criteria; (3) performing a Monte-Carlo analysis to capture uncertainties given in the inputs; (4) applying multi-criteria decision-making, social choice (voting), and fallback bargaining methods to account for three different levels of cooperation among the stakeholders; and (5) computing an aggregate performance index (API) score for each alternative based on its performance across criteria and cooperation levels. API scores communicate relative performance between alternatives. In this way, our methodology maps uncertainty from the input data to reflect risk in the decision and incorporates varying degrees of cooperation into the analysis to identify an optimal and practical alternative.
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Journal articleHdidouan D, Staffell IL, 2016,
The impact of climate change on the levelised cost of wind energy
, Renewable Energy, Vol: 101, Pages: 575-592, ISSN: 1879-0682Society's dependence on weather systems has broadened to include electricity generation from wind turbines. Climate change is altering energy flows in the atmosphere, which will affect the economic potential of wind power. Changes to wind resources and their upstream impacts on the energy industry have received limited academic attention, despite their risks earning interest from investors.We propose a framework for assessing the impact of climate change on the cost of wind energy, going from the change in hourly wind speed distributions from radiative forcing through to energy output and levelised cost of electricity (LCOE) from wind farms. The paper outlines the proof of concept for this framework, exploring the limitations of global climate models for assessing wind resources, and a novel Weibull transfer function to characterise the climate signal.The framework is demonstrated by considering the UK's wind resources to 2100. Results are mixed: capacity factors increase in some regions and decrease in others, while the year-to-year variation generally increases. This highlights important financial and risk impacts which can be adopted into policy to enhance energy system resilience to the impacts of climate change. We call for greater emphasis to be placed on modelling wind resources in climate science.
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Journal articleBoldrin P, Ruiz Trejo E, Mermelstein J, et al., 2016,
Strategies for carbon and sulfur tolerant solid oxide fuel cell materials, incorporating lessons from heterogeneous catalysis
, Chemical Reviews, Vol: 116, Pages: 13633-13684, ISSN: 1520-6890Solid oxide fuel cells (SOFCs) are a rapidly emerging energy technology for a low carbon world, providing high efficiency, potential to use carbonaceous fuels and compatibility with carbon capture and storage. However, current state-of-the-art materials have low tolerance to sulfur, a common contaminant of many fuels, and are vulnerable to deactivation due to carbon deposition when using carbon-containing compounds. In this review we first study the theoretical basis behind carbon and sulfur poisoning, before examining the strategies towards carbon and sulfur tolerance used so far in the SOFC literature. We then study the more extensive relevant heterogeneous catalysis literature for strategies and materials which could be incorporated into carbon and sulfur tolerant fuel cells.
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Journal articleStevens T, Madani K, 2016,
Future climate impacts on maize farming and food security in Malawi
, Scientific Reports, Vol: 6, ISSN: 2045-2322Agriculture is the mainstay of Malawi’s economy and maize is the most important crop for food security. As a Least Developed Country (LDC), adverse effects of climate change (CC) on agriculture in Malawi are expected to be significant. We examined the impacts of CC on maize production and food security in Malawi’s dominant cereal producing region, Lilongwe District. We used five Global Circulation Models (GCMs) to make future (2011 to 2100) rainfall and temperature projections and simulated maize yields under these projections. Our future rainfall projections did not reveal a strong increasing or decreasing trend, but temperatures are expected to increase. Our crop modelling results, for the short-term future, suggest that maize farming might benefit from CC. However, faster crop growth could worsen Malawi’s soil fertility problem. Increasing temperature could drive lower maize yields in the medium to long-term future. Consequently, up to 12% of the population in Lilongwe District might be vulnerable to food insecurity by the end of the century. Measures to increase soil fertility and moisture must be developed to build resilience into Malawi’s agriculture sector.
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Journal articleKeenan TF, Prentice IC, Canadell JG, et al., 2016,
Recent pause in the growth rate of atmospheric CO2 due to enhanced terrestrial carbon uptake
, Nature Communications, Vol: 7, Pages: 1-10, ISSN: 2041-1723Terrestrial ecosystems play a significant role in the global carbon cycle and offset a large fraction of anthropogenic CO2 emissions. The terrestrial carbon sink is increasing, yet the mechanisms responsible for its enhancement, and implications for the growth rate of atmospheric CO2, remain unclear. Here using global carbon budget estimates, ground, atmospheric and satellite observations, and multiple global vegetation models, we report a recent pause in the growth rate of atmospheric CO2, and a decline in the fraction of anthropogenic emissions that remain in the atmosphere, despite increasing anthropogenic emissions. We attribute the observed decline to increases in the terrestrial sink during the past decade, associated with the effects of rising atmospheric CO2 on vegetation and the slowdown in the rate of warming on global respiration. The pause in the atmospheric CO2 growth rate provides further evidence of the roles of CO2 fertilization and warming-induced respiration, and highlights the need to protect both existing carbon stocks and regions, where the sink is growing rapidly.
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Journal articleMattevi C, 2016,
Graphitic carbon nitride as a catalyst support in fuel cells and electrolyzers
, Electrochimica Acta, Vol: 222, Pages: 44-57, ISSN: 1873-3859Electrochemical power sources, such as polymer electrolyte membrane fuel cells (PEMFCs), require the use of precious metal catalysts which are deposited as nanoparticles onto supports in order to minimize their mass loading and therefore cost. State-of-the-art/commercial supports are based on forms of carbon black. However, carbon supports present disadvantages including corrosion in the operating fuel cell environment and loss of catalyst activity. Here we review recent work examining the potential of different varieties of graphitic carbon nitride (gCN) as catalyst supports, highlighting their likely benefits, as well as the challenges associated with their implementation. The performance of gCN and hybrid gCN-carbon materials as PEMFC electrodes is discussed, as well as their potential for use in alkaline systems and water electrolyzers. We illustrate the discussion with examples taken from our own recent studies.
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Journal articleThomas RT, Prentice IC, Graven H, et al., 2016,
Increased light-use efficiency in northern terrestrial ecosystems indicated by CO2 and greening observations
, Geophysical Research Letters, Vol: 43, Pages: 11339-11349, ISSN: 1944-8007Observations show an increasing amplitude in the seasonal cycle of CO2 (ASC) north of 45°N of 56 ± 9.8% over the last 50 years and an increase in vegetation greenness of 7.5–15% in high northern latitudes since the 1980s. However, the causes of these changes remain uncertain. Historical simulations from terrestrial biosphere models in the Multiscale Synthesis and Terrestrial Model Intercomparison Project are compared to the ASC and greenness observations, using the TM3 atmospheric transport model to translate surface fluxes into CO2 concentrations. We find that the modeled change in ASC is too small but the mean greening trend is generally captured. Modeled increases in greenness are primarily driven by warming, whereas ASC changes are primarily driven by increasing CO2. We suggest that increases in ecosystem-scale light use efficiency (LUE) have contributed to the observed ASC increase but are underestimated by current models. We highlight potential mechanisms that could increase modeled LUE.
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Journal articleChakrabarti BK, Nir DP, Yufit V, et al., 2016,
Studies of performance enhancement of rGO-modified carbon electrodes for Vanadium Redox Flow Systems
, ChemElectroChem, Vol: 4, Pages: 194-200, ISSN: 2196-0216Reduced graphene oxide (rGO) suspended in an N,N′-dimethylformamide (DMF) solvent underwent electrophoretic deposition (EPD) on carbon paper (CP) electrodes. X-ray computed micro-tomography (XMT) indicates a 24 % increase in the specific surface area of CP modified with rGO in comparison to the untreated sample. Furthermore, XMT confirms that the deposition also penetrates into the substrate. Raman analysis shows that the rGO deposited is more amorphous than the CP electrode. A significant reduction in charge-transfer resistance of the VO2+/VO2+ reaction is also observed (from impedance measurements) in modified samples in comparison to untreated CP electrodes.
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Journal articleMerla Y, Wu B, Yufit V, et al., 2016,
Extending battery life: a low-cost practical diagnostic technique for lithium-ion batteries
, Journal of Power Sources, Vol: 331, Pages: 224-231, ISSN: 0378-7753Modern applications of lithium-ion batteries such as smartphones, hybrid & electric vehicles and grid scale electricity storage demand long lifetime and high performance which typically makes them the limiting factor in a system. Understanding the state-of-health during operation is important in order to optimise for long term durability and performance. However, this requires accurate in-operando diagnostic techniques that are cost effective and practical. We present a novel diagnosis method based upon differential thermal voltammetry demonstrated on a battery pack made from commercial lithium-ion cells where one cell was deliberately aged prior to experiment. The cells were in parallel whilst being thermally managed with forced air convection. We show for the first time, a diagnosis method capable of quantitatively determining the state-of-health of four cells simultaneously by only using temperature and voltage readings for both charge and discharge. Measurements are achieved using low-cost thermocouples and a single voltage measurement at a frequency of 1 Hz, demonstrating the feasibility of implementing this approach on real world battery management systems. The technique could be particularly useful under charge when constant current or constant power is common, this therefore should be of significant interest to all lithium-ion battery users.
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