Now showing 1 - 9 of 9
  • 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.
      1827Scopus© Citations 68
  • Publication
    The Direct Use of Post-Processing Wood Dust in Gas Turbines
    (Scientific Research Publishing, 2012-09) ; ;
    Woody biomass is a widely-used and favourable material for energy production due to its carbon neutral status. Energy is generally derived either through direct combustion or gasification. The Irish forestry sector is forecasted to expand significantly in coming years, and so the opportunity exists for the bioenergy sector to take advantage of the material for which there will be no demand from current markets. A by-product of wood processing, wood dust is the cheapest form of wood material available to the bioenergy sector. Currently wood dust is primarily processed into wood pellets for energy generation. Research was conducted on post-processing birch wood dust; the calorific value and the Wobbe Index were determined for a number of wood particle sizes and wood dust concentrations. The Wobbe Index determined for the upper explosive concentration (4000 g/m3) falls within range of that of hydrogen gas, and wood dust-air mixtures of this concentration could therefore behave in a similar manner in a gas turbine. Due to its slightly lower HHV and higher particle density, however, alterations to the gas turbine would be necessary to accommodate wood dust to prevent abrasive damage to the turbine. As an unwanted by-product of wood processing the direct use of wood dust in a gas turbine for energy generation could therefore have economic and environmental benefits.
      608
  • 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.
      1132
  • Publication
    Combining Wind and Pumped Hydro Energy Storage for Renewable Energy Generation in Ireland
    (Hindawi Publishing Corporation, 2014-08-21) ; ; ;
    Ireland has one of the highest wind energy potentials in Europe. The intermittent nature of wind makes this renewable resource impractical as a sole source of energy. Combining wind energy with pumped hydro energy storage (PHES) can overcome this intermittency, consuming energy during low-demand periods and supplying energy for periods of high demand. Currently Ireland has a number of hydroelectric power plants and wind farms of various scales in operation. A feasibility study was conducted to investigate the potential of securing a reliable source of renewable energy by increasing the penetration of hydroelectric power by means of combined wind-PHES developments. The greatest wind potential is experienced along the western coast of Ireland and a number of sites were identified here which satisfied a minimum mean wind speed criterion of 10.5 ms−1. Each site was then further evaluated according to topographical requirements for PHES. All but two of the identified sites are immediately unsuitable due to the presence of areas protected under European legislation; this highlights the nonenergy related obstacles in the path of renewable energy generation in Ireland and suggests that a compromise should be researched which could facilitate both renewable energy generation and species and habitat protection in Europe.
      781
  • Publication
    Energy and economic implications of anaerobic digestion pasteurisation regulations in Ireland
    The use of anaerobic digestion for the treatment of organic wastes is spreading throughout Europe. A number of restrictions on organic wastes which can be treated in anaerobic digestion facilities and the subsequent handling of the digested material are specified in European legislation. Regulation 1774/2002/EC as amended states that after reduction the material must be heated to either 70 °C or 90 °C for a minimum of 60 min. An alternative Irish national standard of 60 °C for 48 h twice has been introduced in place of the EU standard. Anaerobic digestion systems are successful only if they produce a significant energy output. The aim of this research was therefore to examine both the EU and Irish national standards as well as a number of alternative treatment scenarios to determine their respective pasteurisation efficiency and energetic requirement. Post-digestion pasteurisation above 60 °C was found to satisfactorily remove all viable Escherichia coli bacteria from the test feedstock. It was determined that the most energy and economically efficient heat treatments were 60 °C for 1 h, 70 °C for 1 h (EU standard), and 80 °C for 30 min. The Irish national standard was found to be prohibitively energy inefficient and expensive.
      1151Scopus© Citations 18
  • 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.
      1034Scopus© Citations 8
  • Publication
    Analysis of bed agglomeration during gasification of wheat straw in a bubbling fluidised bed gasifier using mullite as bed material
    The quantity and composition of the ash content of straw poses technical challenges to its thermal conversion and have been widely reported to cause severe ash sintering and bed agglomeration during fluidised bed gasification. Literature indicates that a combination of reactor design and bed material measures is required to avoid defluidisation at temperatures above 800 °C. Using scanning electron microscopy and energy dispersive X-ray spectroscopy this study investigated the initial agglomeration of a mullite bed during the gasification of wheat straw in a small scale, air blown bubbling fluidised bed. The results show that the temperatures along the height of the bed converge prior to any marked drop in pressure or heating of the lower freeboard. This convergence was seen to occur at temperatures close to 750 °C in repeated gasification experiments. Energy dispersive X-ray spectroscopy indicates coating-induced agglomeration caused by the reaction of alkali metals with silica. Scanning electron microscopy under high magnification revealed a layered structure to the agglomerates, where ash particles are subsumed into a fused material. This suggests the formation of agglomerates by the three step agglomeration process postulated by other authors. Analysis of indices used to predict agglomeration on the basis of a fuel's ash content and composition indicates that the Alkali Index is the most accurate, successfully predicting agglomeration for 7 of the 9 fuels where agglomeration was observed.
      1024Scopus© Citations 30
  • Publication
    The influence of measurement methodology on soil infiltration rate
    (Academic Journals, 2012) ;
    The recorded rate at which water infiltrates into a soil is influenced by the physical condition of the soil, current and previous uses of the soil and the method and equipment used to record the infiltration rate. Soil’s natural variability and the potential inaccuracy associated with particular methods can overestimate infiltration rate. To determine the most suitable apparatus for repeated use at a small-scale, a number of trials were conducted to investigate the influence of the method and moisture regime on the recorded infiltration rate. Trials were conducted on a medium clay-loam soil which has cropping history of maize-winter wheat-grass-grass-grass. It was observed that there was no significant difference in recorded infiltration rates which could be attributed to the practice of pre-saturating the soil prior to measuring infiltration rate. Furthermore, there was no significant difference between the rates recorded using a single ring infiltrometer and a double ring infiltrometer, indicating that these methods are equally suitable for infiltration rate determination when working at this scale which facilitates multiple replications in the same location or within a short timeframe.
      701
  • Publication
    The potential of Miscanthus to harbour known cereal pathogens
    Miscanthus holds great potential as a bioenergy crop and Ireland has ideal conditions for its cultivation, however limited information is available about the interactions between Miscanthus and soil fungi which are pathogenic to other crops grown in Ireland and the UK. Miscanthus may therefore be susceptible to soil-borne pathogens present in the soil prior to crop establishment or may harbour pathogens and facilitate transmission of disease to other crops. The response of Miscanthus to a number of fungal species was recorded to determine the vulnerability of Miscanthus to some of the most important cereal pathogens in Ireland. The microbial species were selected based on their presence in soil and their known pathogenicity towards cereal crops currently grown in Ireland. A number of fungi caused a significant level of infection on detached Miscanthus leaves: Rhizoctonia solani, Fusarium poae (Fusarium sporotrichiella var. poae) and Sordaria fimicola caused the greatest level of symptoms while Fusarium culmorum caused the greatest visual disease symptoms in living tissue during whole plant tests. The results suggest that Miscanthus is susceptible to a number of cereal fungal pathogens, and that of all the species investigated Fusarium species pose the greatest threat to Miscanthus plantings in Ireland. Fusarium is a known causative agent of blight in cereals, thus its ability to survive both on living and discarded Miscanthus tissue is important as it suggests that Miscanthus could act as a 'disease bridge' for cereal pathogens.
      613Scopus© Citations 4