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Smith, William
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Smith, William
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Smith, William
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Now showing 1 - 9 of 9
- PublicationCan EV (electric vehicles) address Ireland’s CO2 emissions from transport?In the period 1990-2007, CO2 emissions from Ireland’s Transport sector increased by 181%. It has been proposed that a transition to electrically-powered vehicles (EV) – either battery-powered (BEV) or plug-in hybrids (PHEV) – offers the potential for significant reductions in these emissions. However, the benefits of PHEV – and of plug-in vehicles generally – accrue because some fraction of the fossil fuel normally consumed by the vehicle is displaced by electricity extracted from the national grid. The net benefit therefore depends on many factors, including the characteristics of the electricity generation and distribution system, and the proportion of vehicle-kilometres (vkm) completed under electric power. This paper examines these factors in an Irish context. On the basis of individual vehicles, it is found that electrification yields substantial and immediate reductions in greenhouse gas emissions for urban-type driving cycles. For inter-city travel, however, the percentage reduction attainable is much smaller, and the technical difficulty of achieving this capability is much greater. Unless that challenge can be overcome, it is shown, 50%-75% of CO2 emissions from private cars will remain beyond the reach of electrification.
1853Scopus© Citations 123 - PublicationVehicle pollutant formation & adverse health implications(University College Dublin. Urban Institute Ireland, 2007)
; ; 365 - PublicationOptimal concentration and temperatures of solar thermal power plantsUsing simple, finite-time, thermodynamic models of solar thermal power plants, the existence of an optimal solar receiver temperature has previously been demonstrated in literature. Scant attention has been paid, however, to the presence of an optimal level of solar concentration at which the conversion of incident sunlight to electricity (solar-to-electric efficiency) is maximized. This paper addresses that gap. The paper evaluates the impact, on the design of Rankine-cycle solar-trough and solar-tower power plants, of the existence of an optimal receiver temperature and an optimal level of solar concentration. Mathematical descriptions are derived describing the solar-to-electric efficiency of an idealized solar thermal plant in terms of its receiver temperature, ambient temperature, the receiver irradiance (radiation striking unit receiver area), solar receiver surface to working fluid conductance, condenser conductance, solar collector efficiency, convective loss coefficients and radiative loss coefficients. Using values from the literature appropriate to direct-steam and molten-salt plants, curves of optimal solar receiver temperature, and optimal solar-to-electric conversion efficiency, are generated as a function of receiver irradiance. The analysis shows that, as the thermal resistance of the solar receiver and condenser increases, the optimal receiver temperature increases whilst the optimal receiver irradiance decreases. The optimal level of receiver irradiance, for solar thermal plants employing a service fluid of molten salts, is found to occur within a range of values achievable using current solar tower technologies. The tradeoffs (in terms of solar-to-electric efficiency) involved in using molten salts rather than direct steam in the case of solar towers and solar troughs are investigated. The optimal receiver temperatures calculated with the model suggest the use of sub-critical Rankine cycles for solar trough plants, but super-critical Rankine cycles for solar tower plants, if the objective is to maximize solar-to-electric efficiency
949Scopus© Citations 32 - PublicationPlug-in hybrid electric vehicles—A low-carbon solution for Ireland?Between 1990 and 2006, the primary energy requirement of the Irish transport sector increased by 166%. Associated greenhouse gas (GHG) emissions have followed a corresponding trajectory, and are responsible—at least in part—for Ireland’s probable failure to meet its Kyoto targets. As in most countries, Ireland’s transport sector is almost totally reliant on oil—a commodity for which Ireland is totally dependent on imports—and therefore vulnerable to supply and price shocks. Conversely, the efficiency and carbon intensity of the Irish electricity supply system have both improved dramatically over the same period, with significant further improvements projected over the coming decade. This paper analyses the prospects for leveraging these changes by increasing the electrification of the Irish transport sector. Specifically, the potential benefits of plug-in hybrid-electric vehicles (PHEV) are assessed, in terms of reducing primary energy requirement (PER) and CO2 emissions. It is shown that, on a per-km basis, PHEV offer the potential for reductions of 50% or more in passenger car PER and CO2 intensity. However, the time required to turn over the existing fleet means that a decade or more will be required to significantly impact PER and emissions of the PC fleet.
1776Scopus© Citations 54 - PublicationExamination of Low-cost Systems for the Determination of Kinematic Driving Cycles and Engine Operating Conditions in Dublin, IrelandWith increased numbers of vehicles on Irish roads, there is now a need to be able to scientifically assess the quantity of pollutant material to which populations are exposed. Traditionally, emissions have been determined using kinematic (vehicle speed) data but recent studies have identified that other parameters are of interest. The work in this Paper focuses on the development and testing of a purpose-built software system to extract on-board diagnostic data from a vehicle in order to derive a driving cycle and to use other engine characteristic data to better inform local pollutant and energy consumption models for Dublin. Comparisons with GPS data shows the system to be cost effective (price and computing overhead) and reliable.
649Scopus© Citations 4 - PublicationProjecting EU demand for natural gas to 2030: A meta-analysisGas demand projections for the EU27 from a variety of sources are compared. Projected demand varies widely between sources, even when similar rates of economic growth and policy strength are assumed. The divergence is shown to result from differing assumptions concerning future energy intensity, on the one hand, and the future contribution of nuclear power and renewables (RES) to electricity generation on the other. The variation with time of some of these projections is also examined. It is found that the gas demand projected by both the International Energy Agency (IEA) and the European Commission (EC) for 2020 and for 2030 has tended to decrease with each successive projection. This is understandable, since the penetration of RES-E has continued to exceed expectations. However, in an economically depressed, post-Fukushima Europe, estimates of future growth in both RES and nuclear generation may need significant revision. The Energy Efficiency Directive, as agreed by the Council of the European Union and the European Parliament in April 2012 (Council of the European Union, 2012), will also impact significantly on future gas demand, even though the measures incorporated are weaker than the original proposal. The analysis presented here shows that a “nuclear decline” due to the Fukushima disaster is seen to moderate, rather than reverse, projected demand decay. A significant shortfall in projected RES capacity, if it were to occur, constitutes a potential source of additional gas demand. Although the emphasis in this paper is on the EU27 as a whole, consideration is given to the regional heterogeneity of each of these impacts. Hence, although aggregate demand growth for the next decade or two is likely to be moderate or (more probably) negative, local demand growth in some regions may be significant. Ensuring adequate access to these specific regions – via interconnection to their EU27 neighbours, and/or directly from extra-EU sources – will therefore be essential. Hence, implementation of the Third Energy Plan should remain a priority.
645Scopus© Citations 12 - PublicationThe Effect of a Three-Way Catalytic Converter on Particulate Matter from a Gasoline Direct-Injection Engine During Cold-StartThis work investigates the effect of a three-way catalytic converter and sampling dilution ratio on nano-scale exhaust particulate matter emissions from a gasoline direct-injection engine during cold-start and warm-up transients. Experimental results are presented from a four cylinder in-line, four stroke, wall-guided direct-injection, turbo-charged and inter-cooled 1.6 litre gasoline engine. A fast-response particulate spectrometer for exhaust nano-particle measurement up to 1000 nm was utilised. It was observed that the three-way catalytic converter had a significant effect on particle number density, reducing the total particle number by up to 65 % over the duration of the cold-start test. The greatest change in particle number density occurred for particles less than 23 nm diameter, with reductions of up to 95 % being observed, whilst the number density for particles above 50 nm diameter exhibited a significant increase. The exhaust temperature plays a significant role on the influence of the catalytic converter on the nano-scale particulate matter. It is evident that the dilution ratio of the exhaust sample has a distinct effect on the particulate matter number and size distribution, influencing the engine-out PM more significantly than the tailpipe-out PM during cold-start engine operation. The catalytic converter also has a considerable effect on the estimated total particle mass.
1763Scopus© Citations 20 - PublicationCan CFD accurately predict the heat-transfer and pressure-drop performance of finned-tube bundles?A Computational Fluid Dynamics (CFD) model capable of predicting heat-transfer and pressure-drop performance of finned-tube bundles in cross flow is presented. Three helically-wound fin geometries are investigated: solid (continuous); partially-serrated; and fully-serrated. A steady-state approach, with a two-equation turbulence model, is employed to examine Reynolds numbers in the range of 5000-30,000. The external Nusselt number and overall pressure drop predicted by the CFD model are compared with those predicted by published empirical correlations. The CFD results fall within the range of values predicted by the empirical correlations. The CFD results show that the Nusselt number increases by up to 23% between the partially- and fully-serrated fins; this sensitivity to serration geometry is not captured in any currently published empirical correlations.
1135Scopus© Citations 15 - PublicationDescription of the development of the LabVIEW instantaneous emissions estimation software for use in the urban environment project air quality work package(University College Dublin. Urban Institute Ireland, 2007)
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