Conference Papers

A Life Cycle Assessment of Emissions Reduction Potential in the Existing Irish Housing Stock: a Perspective of International and Domestic Sources

A. A. Famuyibo et al. — Tue, 06 Nov 2012 02:21:02 PST

As the volume of imported materials increases, the magnitude of the imported environmental impacts becomes a greater factor in the energy demand and related CO₂ emissions from the residential sector. As supply chains of goods within the global arena expands across country and region, domestic consumption of imported goods results in CO₂ emissions in countries of production. Given that these emissions are attributable to countries of import, directing information towards environmental policy experts on a complete view of total emissions of retrofitting along international and domestic sources will have an impact on decision making, and for the first time in Ireland a study of the shares (%) of these sources is the primary aim of this paper. The housing stock has been categorised into thirteen representative archetypes to statistically reflect the mix of key energy related characteristics within the stock of Irish dwellings. Detailed life cycle inventories were prepared for each these archetypes to identify their impacts and then a suite of energy efficient retrofit technologies were applied under ‘meet current building regulations’(current standard) and ‘meet anticipated future regulations’ (passive house standard) to identify the impact of retrofitting on life cycle performance of the housing stock. Results show that although for the average dwelling, operational phase consumption and emissions is much greater than any other phase across all options, there is a wide variation in the shares (%) of international and domestic sources on this balance across the retrofit options.

Analysing Domestic Electricity Smart Metering Data Using Self Organising Maps

Fintan McLoughlin et al. — Tue, 05 Jun 2012 07:16:56 PDT

This paper investigates a method of classifying domestic electricity load profiles through Self Organising Maps (SOMs). Approximately four thousand customers are divided into groups based on their electricity demand patterns. Dwelling and occupant characteristics are then investigated for each group. The results show that SOMs are an effective way of classifying customers into groups in terms of their electrical load profile and that certain dwelling and occupant characteristics are significant factors in determining which group they end up in.

Fluorescence Emission Study of Cdse/ZnS Quantum Dot and Au Nanoparticles Composite for Application in Quantum Dot Solar Concentrators

Subhash Chandra et al. — Fri, 10 Feb 2012 06:36:41 PST

Fluorescence of core shell (CdSe/ZnS) quantum dots (QDs) and Au nanoparticles (NPs) composite has been studied for application in quantum dot solar concentrators (QDSC). We conclude two points from the particular QD/Au NP composite studied. One; for the particular Au NPs concentration, the relative fluorescence emission enhancement increases with decreasing QD concentration. Second; the enhancement is more pronounced for the Au nanoparticles whose surface plasmon resonance wavelength overlaps with the absorption peak of QDs. The fundamental concept that could describe the change in fluorescence emission of QDs in the presence of Au NPs is the locally enhanced electromagnetic field induced by the surface plasmon resonance in the Au NPs. This leads to change in absorption, excitation and emission rate for the QDs. The optimal concentration depends on the coupling and spacing between neighbouring QDs and Au NPs.

Comparative Embodied Energy Analysis of a Steel and Concrete Structural System in Ireland

Adolf Acquaye et al. — Wed, 19 Oct 2011 04:53:43 PDT

Engineering building design focuses on optimising operational energy use and ignores the energy required to procure and construct a building. This energy, termed ‘embodied energy’, can be very significant when compared to operational energy. Therefore, it is important to minimise the embodied in buildings; this must be done at the design stage. This paper presents a comparative embodied energy analysis of two structural design solutions for a modern office building: one in concrete and one in steel. Process analysis is used to determine production, transport and construction energy requirements for all system components. Results indicate that the steel solution has more than two and a half times as much embodied energy as the concrete solution.

A Parametric Analysis of Domestic Electricity Consumption Patterns in Ireland

Fintan McLoughlin et al. — Fri, 24 Jun 2011 01:03:17 PDT

This paper reports findings from a study of electrical load profiles obtained from a survey of a representative cross section of approximately 4,000 Irish dwellings. Electricity demand was recorded at half-hourly intervals for each dwelling over a six month period from 1st July 2009 to 31st December 2009. Descriptive statistics are shown for each electrical parameter such as mean, maximum demand, load factor and time of use (ToU) of electricity consumption. The mean power demand and daily mean load factor of the sample was 0.512kW and 23.43% respectively for all dwellings over the monitoring period. A mean daily maximum demand of 2.5kW was recorded for the sample. The most frequent ToU for maximum and minimum electricity consumption over the monitoring period was 18:00 - 18:30 and 06:30 – 07:00 respectively.

Novel materials for Non-Optical Solar Concentration

S. McCormack et al. — Sat, 29 Jan 2011 04:08:26 PST

Trends in Environmental Health Education:Opening Address

Brian Norton — Sat, 29 Jan 2011 03:22:53 PST

Indoor and Outdoor testing of small-scale quantum dot solar concentrators of various geometries and QD concentrations

Brenda Rowan et al. — Sat, 29 Jan 2011 03:22:51 PST

Efficiency, Intermittency and Viability: Scientific Challenges in Harnessing Solar Energy

Brian Norton — Sat, 29 Jan 2011 03:22:48 PST

Modelling of Re-absorption Losses in Quantum Dot Solar Concentrators

Manus Kennedy — Sat, 15 Jan 2011 04:24:23 PST

A Monte-Carlo ray-trace model has been developed which allows the calculation of the optical efficiency (ηopt) and concentration ratio (CR) values of a Quantum Dot Solar Concentrator (QDSC). In this paper, ηopt values have been calculated using a range of material refractive indices, material attenuation coefficients, and quantum dot (QD) quantum efficiencies (QE). Spectral overlap leads to reabsorption of light in the device which leads to increased escape cone losses and QD QE losses. Results have been obtained for ideal QD spectra, where there is 0% overlap between QD emission and absorption spectra (and hence no re-absorption), and for real QD spectra, where there is ~60% overlap. The effect of placing a spectrally selective reflective surface on the top of the QDSC, in order to reduce escape cone losses, has also been examined.

Ray-trace Modelling of Reflectors for Quantum Dot Solar Concentrators

Manus Kennedy et al. — Sat, 15 Jan 2011 04:24:22 PST

Quantum Dot Solar Concentrators (QDSCs) are static, non-imaging concentrators which do not require expensive solar tracking and concentrate both direct and diffuse light. Optical efficiencies (ηopt) and concentration ratios (C) of a single plate QDSC were calculated by Monte-Carlo ray-trace modelling. Consideration of reflection, refraction, quantum dot (QD) photon emission and absorption and light attenuation in the device matrix were included in the analysis. In this paper, the effect of placing plane and diffuse reflectors at the rear surface was analyzed. Mirrors with a structured surface (saw-tooth shaped) were also modelled and the effect of each reflector type on C was determined, for direct and diffuse incident light. The diffuse and structured reflectors perform better than the plane reflector under direct light, but there is no significant difference under diffuse light. A spectrally selective reflector, placed at the top surface, reflects light emitted by QDs inside the escape cone back into the concentrator. For a particular set of model parameters, the model results show an increase in C of 13% due to the inclusion of a spectrally selective reflector.

Modelling the Effect of Device Geometry on Concentration Ratios of Quantum Dot Solar Concentrators

Manus Kennedy et al. — Sat, 15 Jan 2011 04:24:20 PST

Quantum dot solar concentrators (QDSCs) are static, nonimaging concentrators which concentrate both direct and diffuse light. Using Monte-Carlo ray-trace modelling, concentration ratios (C) were predicted for QDSCs of different 2-D geometries. The optimum shape and size were determined, for given system parameters, by calculating the relative cost per unit power output. Devices with different 3-D geometry were also compared. The thickness of the plate was varied and devices with tapered thickness were modelled to investigate the effect on C.

Ray-trace Modelling of Quantum Dot Solar Concentrators

Manus Kennedy et al. — Sat, 15 Jan 2011 04:18:50 PST

Ray-trace modelling has been used to investigate the performance of luminescent solar concentrator (LSC) plates containing high quantum yield (QY) NIR emitting quantum dots (qd). Optical efficiencies and spectrally enhanced concentration ratios are compared to those of LSC plates containing green and orange emitting qds. Concentration ratios 2-5 times higher are predicted with the NIR emitting qds, partly due to the broader absorption range but more significantly due to lower re-absorption losses. The performance of the NIR plate is found to be similar to that predicted for a plate containing a single red Coumarin dye. For each luminescent species, the predicted optical efficiencies are higher for diffuse incidence than for direct incidence, as a higher fraction of the diffuse incident spectrum is within the absorption range.

Thermodynamic Modelling and Ray-trace Modelling of Luminescent Solar Concentrators: a Comparison of the two Approaches

Manus Kennedy et al. — Sat, 15 Jan 2011 04:18:41 PST

The electrical and spectral output from luminescent solar concentrator (LSC) devices is predicted using thermodynamic modelling and ray-trace modelling techniques. Predicted output from four LSCs of varying dimensions, containing different luminescent dyes, are found to be in good agreement with measured output taken from fabricated LSCs. Despite the many different processes involved in the two modelling approach, predicted short circuit current densities from both approaches are found to be in excellent agreement.

Ray Trace Modelling of Multiple Dyes in a Luminescent Solar Concentrator

Manus Kennedy et al. — Sat, 15 Jan 2011 04:12:17 PST

A previously developed Monte-Carlo ray-trace model has been modified to incorporate multiple luminescent species. Liquid luminescent solar concentrators (LSCs) have been fabricated to verify the ray-trace predictions for LSCs containing multiple luminescent dyes. Single dye and multiple dye solutions of varying concentrations can be easily prepared and inserted into the experimental liquid LSC setup. In this way, experimental uncertainties, such as reduction in the luminescent quantum yield, can be reduced. Hence, the spectral effects of various single and multiple dyes can be analysed and compared more accurately with ray-trace predictions. Initial results from the liquid LSC characterisation and comparison with model predictions are presented here.

Solar Cell Efficiency Enhancement Through Down-Shifting and Up-Converting Layers: the Ephocell Project: Luminescent Downshifting Quantum Yield Measurements

M. Kennedy et al. — Sat, 15 Jan 2011 04:12:16 PST

Organic cells and dye-sensitized cells developed to-date have a narrow active absorption range, relative to the spectral range of the available solar resource. Their efficiency could be significantly enhanced through a process of down-shifting (DS) and up-conversion of non-absorbable photons converting them to photons better matching the spectral response of the particular solar cell. The DS molecules must exhibit a large Stokes shift and high luminescent quantum yield when incorporated in the downshifting polymer layer. In this paper, the QY of a downshifting Europium (III) complex in solution is determined using two distinct experimental techniques. The QY is measured for varying concentration and at varying excitation wavelength.

New Concept for Luminescent Solar Concentrators

Subhash Chandra et al. — Fri, 14 Jan 2011 03:50:47 PST

We have studied the excitation rate of Lumogen Red dye molecules by enhanced local electromagnetic field of Au nanoparticles for thin film luminescent solar concentrator (LSCs).The localized enhanced electromagnetic field of Au nanoparticles leads to an increase the excitation rate, and consequently in emission rate of dye molecules. By varying the distance between Au nanoparticles and dye film we showed transition form quenching to enhancement in edge emission and resultant ISC current output of thin film LSCs. When dye molecules were placed in the range of enhanced electromagnetic field of Au nanoparticles. Two competing factors affected the edge emission of thin film LSC; increased excitation rate (by enhanced local electromagnetic field of Au nanoparticles) and distance between Au nanoparticles and dye molecules.

Assessment of the Embodied CO2eq in Buildings towards a Sustainable Building Design and Construction

Adolf Acquaye et al. — Fri, 14 Jan 2011 03:22:40 PST

Research studies have shown that the initial energy embodied in a building can be as much as 67% of the operational energy over a 25 year period. With growing global concerns over material and resource consumption and the emissions of CO2 into the atmosphere, the energy embodied in buildings constructed in town and cities becomes important and one of the key issues that needs to be tackled in the design stages in order to strive towards sustainable buildings design. In this paper, a hybrid embodied carbon dioxide equivalent (CO2eq) methodology used to assess the CO2eq embodied in buildings is presented. The hybrid methodology consists of an Input-Output (I-O) and a process-based analysis. The I-O analysis is undertaken using re-derived Supply and Use and Input-Output data for Ireland which includes energy inputs into imported construction products and materials and construction sub-sectoral energy data. The Grand Canal Apartments in Dublin, Ireland is used as a case study. The buildings substructure, internal walls, floors, stairs, frame and roof was analysed in the study. The Irish construction sector is divided into five different sub-sectors, each having direct input-output energy intensities and accounting for different construction activities. The construction sub-sectoral I-O direct energy intensities ranges from 25.61tCO2eq/m€ for general fit-out to 493.27tCO2eq/m€ for the use of construction machinery. When embodied CO2eq analysis is carried out at the construction sub-sectoral level, there is a methodological improvement in the calculated values for the direct input-output as well as the total energy intensities over other traditional hybrid methods because of the use of disaggregated sub-sector construction data which can be more specifically applied to the type of construction project being considered. This hybrid methodology further makes use of disaggregates factors that disaggregate the energy supply sectors in the Input-Output analysis into individual sub-sectors supplying energy to the construction sector. Increasing population in urban cities and town means that new building and other social infrastructure needs to be constructed. Embodied CO2eq emissions of new buildings should be used as one of the sustainable indicators to measure the whole life sustainability of buildings. The embodied CO2eq of a Grand Canal apartment building was estimated to be 0.00718tCO2eq/€. Energy saving efforts and sustainability initiatives in the construction sector such as considerations to embodied CO2eq of building materials, selection and design options can play a significant role in reducing the overall future CO2eq of the country. Reduction in the CO2eq embodied in buildings helps to tackle environmental pollution but needs however to be balanced with economic and social costs in order to achieve an overall sustainable urban solution.

The Generation of Domestic Electricity Load Profiles through Markov Chain Modelling

Aidan Duffy et al. — Thu, 13 Jan 2011 07:08:57 PST

Micro-generation technologies such as photovoltaics and micro-wind power are becoming increasing popular among homeowners, mainly a result of policy support mechanisms helping to improve cost competiveness as compared to traditional fossil fuel generation. National government strategies to reduce electricity demand generated from fossil fuels and to meet European Union 20/20 targets is driving this change. However, the real performance of these technologies in a domestic setting is not often known as high time resolution models for domestic electricity load profiles are not readily available. As a result, projections in terms of reducing electricity demand and financial paybacks for these micro-generation technologies are not always realistic. Domestic electricity load profiles are often highly stochastic, influenced by many different independent variables such as environmental, dwelling and occupant characteristics that shape individual customer’s load across a single day. This paper presents a stochastic method for generating electricity load profiles based on the application of a Markov chain process. Electricity consumption was recorded at half hourly intervals over a six month period for five individual Irish dwelling types and used to generate synthetic electricity load profiles. The purpose of this paper is to determine whether Markov chain modelling is an effective way of re-generating electricity load profiles for domestic dwellings and identify shortcomings with this particular technique. The results show that the magnitude component of the load profile can be reproduced effectively whilst the temporal distribution needs to be addressed further.

A Life Cycle Cost Analysis of Large-scale Thermal Energy Storage Technologies for Buildings using Combined Heat and Power

Kenneth Gaine et al. — Thu, 13 Jan 2011 06:45:04 PST

Buildings account for approximately 40% of energy consumption and greenhouse gas (GHG) emissions in developed economies, of which approximately 55% of building energy is used for heating and cooling. The reduction of building-related GHG emissions is a high international policy priority. For this reason and because there are many technical solutions for this, these polices should involve significant improvements in the uptake of small-scale energy efficient (EE) systems. However the widespread deployment of many technologies, must overcome a number of barriers, one of which is a temporal (diurnal or seasonal) mismatch between supply and demand. Costeffective thermal storage solutions have the potential to improve financial performance, while simultaneously reducing associated GHG emissions. The aim of this paper is to identify existing thermal energy storage (TES) technologies and to present and asses the economic and technical performance of each for a typical large scale mixed development. Technologies identified include: Borehole Thermal Energy Storage (BTES) and Aquifer Thermal Energy Storage (ATES). A Heat transfer analyses and system simulations of a variety of BTES systems are carried out using a Finite Element Analysis package (ANSYS) and energy balance simulation software (TRNSYS) to determine the optimal system design. Financial models for each system are developed, including capital, installation, running and maintenance costs. Using this information the unit costs of energy recovered from the storage area are estimated. It was found that a deep BTES was the least economically attractive solution for daily storage and that a medium depth in the region of 50 meters was the most feasible with running costs of approximately €0.055 per kWh.