Now showing 1 - 10 of 64
  • Publication
    Photo-active and optical properties of bismuth ferrite (BiFeO3): an experimental and theoretical study
    An experimental and a hybrid density functional theory study of the photo-active and optical properties of bismuth ferrite are presented. Phase-pure photo-catalytically active BFO was prepared experimentally with a 28% degradation of methyl orange observed over a 7- hour period. Direct and indirect band gaps were measured to be 2.10 and 1.92 eV, respectively. BFO was also studied computationally with the use of hybrid density functional theory, quite suitable for such a multiferroelectric material. This led to excellent, semiquantitative agreement between hybrid DFT and experimental approaches for absorption coefficients.
      2516Scopus© Citations 72
  • Publication
    Bubbling fluidised bed gasification of wheat straw-gasifier performance using mullite as bed material
    The adoption of wheat straw as a fuel for gasification processes has been hindered due to a lack of experience and its propensity to cause bed agglomeration in fluidised bed gasifiers. In this study wheat straw was gasified in a small scale, air blown bubbling fluidised bed using mullite as bed material. The gasifier was successfully operated and isothermal bed conditions maintained at temperatures up to 750 ◦C. Below this temperature, the gasifier was operated at equivalence ratios from 0.1 to 0.26. The maximum lower heating value of the producer gas was approximately 3.6 MJm−3 at standard temperature and pressure (STP) conditions and was obtained at an equivalence ratio of 0.165. In general, a producer gas with a lower heating value of approximately 3 MJm−3 at STP could be obtained across the entire range of equivalence ratios operated. The lower heating value tended to fluctuate, however, and it was considered more appropriate for use in heat applications than as a fuel for internal combustion engines. The concentration of combustibles in the producer gas was lower than that obtained from the gasification of wheat straw in a dual distributor type gasifier and a circulating fluidised bed. These differences were associated with reactor design and, in the case of the circulating fluidised bed, with higher temperatures. Equilibrium modelling at adiabatic conditions, which provides the maximum performance of the system, showed that the gasifier was operating at suboptimal equivalence ratios to achieve greatest efficiencies. The maximum calculated theoretical cold gas efficiency of 73% was obtained at an equivalence ratio of 0.35.
      975Scopus© Citations 8
  • Publication
    Miscanthus production and processing in Ireland: An analysis of energy requirements and environmental impacts
    The environmental impact of bioenergy supply systems can be determined using life cycle assessment methodologies. This study focuses on the impact of production of Miscanthus pellets and briquettes, potentially used to satisfy renewable energy requirements in Ireland. The impact categories considered are particularly important when assessing bioenergy systems; global warming potential, acidification potential, eutrophication potential, and energy demand. The scope of the study incorporates Miscanthus cultivation, harvest, processing and transport to a biomass distributor. The aim of the research is to evaluate the effects of changes in keys variables on the overall environmental impacts of the system. The scenarios examined include replacement of synthetic fertilisers with biosolids, Miscanthus processing by pelleting and briquetting, and transport distances of 50 and 100 km. Results indicate that maintenance and processing of the Miscanthus crop have the most environmental impacts with transport having less of an effect. Replacing synthetic fertiliser with biosolids results in a reduction in global warming potential of 23–33% and energy demand of 12–18%, but raises both acidification and eutrophication potential by 290–400% and 258–300%, respectively. Pelleting of Miscanthus requires more energy than briquetting, hence has higher impacts in each category assessed. Increasing the transport distance from 50 to 100 km, results in a small increase in each impact category. Miscanthus briquette production compares favourably with wood pellet, kerosene, and coal production, with Miscanthus pelleting proving more environmentally damaging.
      916Scopus© Citations 47
  • Publication
    Influence of coating properties on the adhesion of proteins to atmospheric plasma modified surfaces
    Protein adhesion is of key importance for the biocompatibility of medical devices. This study investigates the adsorption of protein, bovine serum albumin (BSA), onto both uncoated silicon wafers and nanometre thick fluorosiloxane coated wafers. A plasma polymerised coating was deposited from a mixture of tetramethylcyclotetrasiloxane (TC) and perfluorooctyltriethoxysilane (FS) (1:1 by vol. ratio). The liquid precursor mixture was nebulised into an atmospheric plasma jet formed using the PlasmaStreamTM system. The adsorption of protein on the plasma polymerised coatings was evaluated under dynamic flow conditions using a spectroscopic ellipsometry technique. The rate of protein adsorption onto coated and uncoated silicon wafer substrates was monitored over time after the BSA solution was introduced into a flow cell. These measurements indicated the adsorption of a 2 nm thick BSA protein layer on the uncoated silicon wafers. The ellipsometry thickness measurements of adsorbed protein on silicon wafer were confirmed using quartz crystal microbalance measurements (QCM). The BSA adsorption studies were then repeated with a fluorosiloxane coating. These coatings exhibited a highly textured surface morphology with low surface energy and a high water contact angle of 156 . The ellipsometry flow cell tests with BSA indicated almost no adsorption of protein onto the superhydrophobic fluorosiloxane coating. This study demonstrated the ability of ellipsometry to measure protein adsorption under dynamic flow 2 conditions and the influence of surface properties on protein adsorption.
      230
  • Publication
    Transport sector in Ireland: Can 2020 National targets drive indigenous biofuel production to success?
    Ireland's transport sector consumes just slightly less than one third of all energy in Ireland and is heavily dependent on oil imports, especially diesel. The European Union has set targets that are to be met by 2020, in order to guarantee a sustainable future for Europe and assure security of energy supply. There is an increase of biofuel usage in the transport sector, to reduce greenhouse gas emissions and encourage indigenous production of renewable sources. Currently, Ireland has only two licensed suppliers of biodiesel. The Irish government has issued a number of policy support mechanisms, and while that has increased the use of biofuels in Ireland, it has not necessarily aided the domestic suppliers of biofuels. The aim of this paper is to detail the existing policies and support mechanisms in Ireland and to examine whether it is possible for Ireland to produce biofuels indigenously while meeting the 2020 targets and competing with the alternative conventional imports. Alternatives to the current supply scenario will be considered, including alternatives such as electric vehicles, recovered waste vegetable oils, and grass gasification for biomethane for natural gas vehicles.
      1231Scopus© Citations 5
  • Publication
    Practical Experience with Woody Biomass in a Down-Draft Gasifier
    (Lifescience Global, 2013-02) ; ;
    Gasification is the cleanest method of obtaining energy from fossil fuels, but with increasing awareness of depleting fossil fuel reserves attention has shifted towards renewable sources of energy. Any carbonaceous material can be gasified to generate high-value end-products from otherwise potentially low-value materials. Gasification can also generate energy from purpose-grown bioenergy crops, and Ireland has an ideal climate to produce woody biomass for energy generation. This update outlines some preliminary results from an investigation into the most suitable woody feedstock for small-scale localised gasification to produce a synthetic gas suitable for use in internal combustion engines. Argentinean- and German-standard wood pellets and Irish-grown willow chips were gasified in a down-draft gasifier. Operation of the gasifier led to the observation that the willow chips bridged within the feedstock hopper which prevented completion of gasification. Implementing a stirring bar in the feedstock hopper prevented bridging and gasification was then successful. Collection of the gas produced during gasification of willow chip was unsuccessful, however gas composition analysis indicates pellets which meet the German-standard are more suitable than Argentinean-standard pellets for use in a down-draft gasifier; work is underway to determine the composition of willow-derived synthetic gas to determine the most suitable feedstock for decentralised gasification by rural communities in Ireland as part of smart farming systems.
      1124
  • Publication
    Influence of doping on the photoactive properties of magnetron-sputtered titania coatings: Experimental and theoretical study
    (American Physical Society, 2012-09) ; ; ;
    Titanium dioxide (TiO2) thin films, doped with chromium (Cr) and codoped with chromium-carbon (Cr, C) and chromium-nitrogen (Cr, N) of various concentrations, were deposited using magnetron sputtering. Postdeposition thermal treatments were carried out at 450 ◦C for 5 h to change the as-deposited amorphous coatings to their crystalline form. The crystalline phase was found to be dependent on the amount and type of dopant present. Ultraviolet-visible (UV-Vis) absorption data and band gap energies calculated by spectroscopic ellipsometry showed that, on increasing Cr concentration, a shift of the absorption edge towards visible light and a reduction of the band gap occurred. This was further improved by codoping of Cr with either N or C, with the latter case exhibiting more photo-activity towards visible light. In addition, hybrid density functional theory (DFT) calculations were performed for Cr-, N-. and C-monodoping, together with Cr-C and Cr-N codoping, in both rutile and anatase phases of crystalline titania. Using this method, absorption coefficients and band gaps were determined to explore photo-activity. Very good, semiquantitative agreement was found between the DFT and experimental approaches for these quantities, underlining the key role of state-of-the-art quantum calculations in interpreting and guiding experimental studies of doping in metal oxides.
      632Scopus© Citations 22
  • Publication
    Regional integration of renewable energy systems in Ireland - The role of hybrid energy systems for small communities
    Due to a lack of indigenous fossil energy resources, Ireland's energy supply constantly teeters on the brink of political, geopolitical, and geographical unease. The potential risk to the security of the energy supply combined with the contribution of anthropogenic greenhouse gas emissions to climate change gives a clear indication of Ireland's need to reduce dependency on imported fossil fuels as primary energy source. A feasibility analysis to investigate the available renewable energy options was conducted using HOMER software. The net present cost, the cost of energy, and the CO2 emissions of each potential energy combination were considered in determining the most suitable renewable and non-renewable hybrid energy system. Wind energy was shown to have the greatest potential for renewable energy generation in Ireland: wind energy was a component of the majority of the optimal hybrid systems both in stand-alone and grid-connected systems. In 2010 the contribution of wind energy to gross electricity consumption in Ireland approximated 10%, and the results of this feasibility study indicate that there is great potential for wind-generated energy production in Ireland. Due to the inherent variability of wind energy the grid-connected system results are particularly relevant, which show that in more than half of the analyses investigating electrical energy demand the incorporation of wind energy offset the CO2 emissions of the non-renewable elements to such a degree that the whole system had negative CO2 emissions, which has serious implications for Kyoto Protocol emissions limits. Ireland also has significant potential for hydropower generation despite only accounting for 2% of the gross electricity consumption in 2010. Wind and hydro energy should therefore be thoroughly explored to secure an indigenous primary energy source in Ireland.
      1812Scopus© Citations 68
  • Publication
    Antifouling coatings made with Cold Spray onto polymers: Process characterization
    Cold Spray (CS) of copper particles onto polymers has been validated as an effective tool for maintaining surface integrity in bioenvironments. CS requires limited heat input, can be applied locally or in large areas. The key parameters are particle penetration depth and copper surface coverage. However, the process parameters that can optimize the coating performance with deposition have not been comprehensively explored. In this paper, copper particles were deposited onto two polymers used in marine applications. A detailed analysis was carried out to correlate the key surface properties to the process so as to determine the optimum conditions.
      795Scopus© Citations 22
  • Publication
    Development of a bacterial propionate-biosensor for anaerobic digestion monitoring
    Monitoring anaerobic digestion (AD) leachate for changes in acetate and propionate concentrations is essential for effective AD operation. In this paper the development of a novel propionate cell-based biosensor is described. A previously designed E. coli mutant (IMD Wldgy) that could selectively determine acetate concentrations in synthetic leachates, based on oxygen uptake measurements, was used as a starting point in the development of a propionate biosensor. However, the propionate-grown IMD Wldgy cells exhibited extremely low propionate:acetate O2 consumption ratios (1:2.4). Screening for alternative propionate-grown E. coli strains naturally possessing a more favourable propionate:acetate O2 consumption ratio identified strain IMD 1, which exhibited a positive ratio (1.6:1). To improve the selectivity of the strain, successive gene knockouts were performed generating the IMD 1 hldgyep mutant. However, propionate-grown IMD 1hdlgyep's O2 consumption ratio was deemed too low to be considered as a propionate detecting bio-element. It was reasoned that the mechanisms by which E. coli activates acetate had to be removed. Deleting acs (acetyl-CoA synthesase) and ackA (acetate kinase) from IMD Wldgyep, resulted in an E. coli IMD Wldgyepak knockout mutant that, when grown on propionate, produced a mean propionate:acetate O2 consumption ratio of approx. 13:1. The resulting IMD Wldgyep and IMD Wldgyepak strains, which formed the acetate- and propionate-biosensor, respectively, were capable of detecting acetate and propionate concentrations ranging from 0.05 mM to 4.5 mM within two-phase AD synthetic leachates.
    Scopus© Citations 7  303