Achieving a holistic view of the life cycle performance of existing dwellings

Models which fully evaluate the life cycle energy and greenhouse gas (GHG) emissions of national housing stocks are not reported in literature. Capturing a holistic view of energy and emissions of the residential sector is an important process that can lead to a more effective policy making. This paper presents a methodology which evaluates the life cycle energy and GHG emissions of retrofitting housing stocks considering all life cycle stages and incorporating, to the greatest extent possible, all upstream inputs. To achieve this, we developed a hybrid model of the existing Irish housing stock, comprising a process-based approach supplemented by input-output LCA for installation of materials and fit-outs and maintenance of appliances. Life cycle analysis (LCA) is a commonly accepted technique for evaluating cradle-to-grave environmental impacts of a product. Using an assumed 50-year life span in all cases, representative archetypes were used to estimate the performance along retro fitting, operation, maintenance and disassembly phases of the three selected house retrofit scenarios: BaseCase (no interven- tion), Current Standards (retrofitting to meet current building regulations) and Passive House (retrofitting to meet Passive House Standards). Results show that detached houses displayed the highest range of life cycle energy and exhibited the greatest absolute and percentage reductions compared to other house types, as life cycle energy ranges from 386-614 kWh/m2yr, 225-261 kWh/m2yr and 126-137 kWh/m2yr for all house scenarios, respectively. Using these results an assessment is provided for policy makers on a holistic view of the life cycle performance of existing dwellings

Embodied Energy Analysis: A Sustainable Construction Design Assessment Tool

Embodied energy analysis can be used as a construction design assessment tool in a sustainable matrix for a building. Its implementation however remains challenging mainly because of data measurement errors. A comparison between the deterministic embodied energy (EE) of a building and the stochastic EE of the same building undertaken using Monte Carlo simulation showed a wide variation in results. It is recommended that the specification of EE intensity of building materials in the construction industry can assist in producing accurate and more credible EE values of building

Teat detection for an automated milking system

Application time when placing all four cups to the udder of a cow is the primary time constraint in high capacity group milking. A human labourer can manually apply four cups per animal as it passes on a rotary carousel in less than ten seconds. Existing automated milking machines typically have an average attachment time in excess of one minute. These systems apply the cups to each udder quadrant individually. To speed up the process it is proposed to attach all four cups simultaneously. To achieve this, the 3D position and orientation of each teat must be known in approximate real time. This thesis documents the analysis of a stereo-vision system for teat location and presents further developments of the system for detection of teat orientation. Test results demonstrate the suitability of stereovision for teat location but indicate that further refinement of the system is required to produce increased accuracy and precision. The additional functionality developed for the system to determine teat orientation has also been tested. Results show that while accurate determination of teat orientation is possible issues still exist with reliability and robustness

Modelling the Impact of Leading Edge Erosion Progression on the Electricity Produced by Wind Turbines

This thesis discusses the development of a model to predict the progression of erosion on a wind turbine blade with time, and the effects that progressive erosion has on wind turbine Annual Energy Production (AEP). An Erosion Progression Model (EPM) has been produced which can predict the erosion due to rain droplet impacts on a wind turbine blade as a function of time, mean wind speed, and rainfall intensity. Novel methods to predict the erosion affected area, and to incorporate distributed erosion have been developed to predict realistic eroded blade surface geometries. Blade inspection data, provided by \O{}rsted, from two operational wind farms was used to validate EPM predictions. An experimental campaign, using pressure, force balance and infra-red thermography measurements, was undertaken to validate a method for testing a blade section with Detachable Leading Edges (DLEs) in the Durham 2m wind tunnel. Results from wind tunnel tests using DLEs with an eroded geometry, predicted by the EPM, were used to validate a two-dimensional Computational Fluid Dynamics (CFD) method for calculating aerodynamic forces on aerofoils with distributed erosion. Simulations of 205 combinations of mean wind speed, annual rainfall intensity and operating time were conducted using the validated CFD method. Blade Element Momentum (BEM) calculations of the DTU 10MW RWT, over 10 years of operation, when coupled with an annual wind distribution for Anholt offshore wind farm, showed that increases in both mean wind speed and annual rainfall intensity result in an increase in the percentage AEP loss. AEP losses of 0.4-1.6\% may be expected after 10 years, depending on the environmental conditions

Feed‐in Tariff Design for Domestic Scale Grid‐Connected PV Systems Using High Resolution Household Electricity Demand Data

The advent of large samples of smart metering data allows policymakers to design Feed‐in Tariffs which are more targeted and efficient. This paper presents a methodology which uses these data to design FITs for domestic scale gridconnected PV systems in Ireland. A sample of 2,551 household electricity demand data collected at ½‐hourly intervals, electricity output from a 2.82 kWp PV system over the same time interval as well as PV system costs and electricity tariffs were used to determine the required FIT to make it worthwhile for the households to invest in the PV system. The methodology shows that it is possible to design single, multiple and continuous FITs. Continuous FITs are the most efficient and result in no overcompensation to the housholder while single and multiple FITs are less efficient since they result in different levels of overcompensation. In the PV case study considered, it was shown that the use of three FITs (0.3170, 0.3315 and 0.3475 €/kWh) resulted in a 59.6% reduction in overcompensation compared to a single FIT of 0.3475 €/kWh; assuming immediate and complete uptake of the technology, this would result in NPV savings of over €597m to the Irish government over a 25 year lifetime

Life-cycle assessment of non-domestic building stocks: A meta-analysis of current modelling methods

Building stock models (BSMs) are essential for simulating the contributions of regional and national building sectors to climate change under different policy scenarios, and for identifying pathways to climate change mitigation. To date, BSMs have focused on the operational life-cycle impacts of domestic dwellings; there has been less emphasis either on non-domestic buildings (NDBs) or full life-cycle analysis. This paper provides a first review of the theory and practice of NDB stock modelling which considers life-cycle energy, emissions and costs. A meta-analysis of the literature was undertaken involving a structured search of relevant articles in key scientific repositories. 98 in-scope studies were identified and data collected on their aims and objectives, methodologies, data sources, system boundaries, considered impacts, representativeness, uncertainty analysis, validation and verification techniques, further research identified, model transparency and software tools employed. The review necessitated the classification of modelling methodologies. The existing ‘bottom-up’ and ‘top-down’ groups were found to be ambiguous and led to confusion. Therefore, an alternative methodology classification is proposed, considering both the modelling technique and model simulation data used. The findings of the analysis indicate that most approaches use engineering models employing archetype data. However, almost all current life-cycle models of NDB stocks are incomplete. Only one study considered the full building life-cycle and most did not include uncertainty analysis. The reproducibility of study results is poor since most do not provide sufficiently-detailed information on the models and data used. Critically, there is a lack of representative input data which limits their usefulness as evidence in policymaking

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

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

The Effects of Physical Activity on Greenhouse Gas Emissions for Common Transport Modes in European Countries

This paper applies a life cycle methodology to estimate activity-related contributions of transport modes to GHG emissions. The methodology uses national input-output tables, environmental accounts, household budget data and nutritional data to derive food-sector GHG coefficients of consumption for ten European countries. The food energy requirements for each mode of transport are estimated taking account of the modal activity level and energy requirements. Walking, cycling, driving and bus travel are considered. Typical national food energy-related emissions for walking, cycling, and driving ranged from 25.6 - 77.3 gCO2-eq/pass.km, 10.4 - 31.4 gCO2-eq/pass.km and 1.7 - 5.2 gCO2-eq/pass.km; passenger transport was found to result in no food-related emissions above those for a resting individual. Emissions vary between countries and depend on the emissions intensities of their energy sectors as well as food prices and average body weights. A life cycle assessment of modal emissions in the UK was undertaken using the food-energy emissions intensities estimated. UK car travel was found to have the highest emissions intensity, followed by bus travel, cycling and walking

Analysis of the Thermal Performance of a Solar Water Heating System with Flat Plate Collectors in a Temperate Climate

The thermal performance of a solar water heating system with 4 m2 flat plate collectors in Dublin, Ireland is presented in this paper. The experimental setup consisted of a commercially available forced circulation domestic scale system fitted with an automated sub‐system that controlled hot water draw‐offs and the operation of an auxiliary immersion heater. The system was tested over a year and the maximum recorded collector outlet fluid temperature was 70.4 oC while the maximum water temperature at the bottom of the hot water tank was 59.9 oC. The annual average daily energy collected was 19.6 MJ/d, energy delivered by the solar coil was 16.2 MJ/d, supply pipe loss was 3.2 MJ/d, solar fraction was 32.2%, collector efficiency was 45.6% and system efficiency was 37.8%. Supply pipe losses represented 16.4% of energy collected

Evaluation of Wind Energy Forecasts: the Undervalued Importance of Data Preparation

The evaluation of wind energy forecasts is a key task for those involved in the wind power sector, and the accurate evaluation of forecasts is fundamental to make informed decisions both in business and research. To evaluate the accuracy of a forecast, observed values must be compared against forecast values over a test period. At times, however, the actual generation of a wind farm can be affected by factors that are outside the scope of the forecast model. Evaluating a forecast using a data set that includes such out-of-scope observations might give a biased or inconsistent assessment. In the data preparation phase, then, the evaluator should identify out-of-scope data and decide whether to include or remove these from the data set. In this paper, we carry out an empirical study based on data from an existing wind farm and a number of day-ahead forecasts in order to highlight the effects of including in- and out-of-scope data on forecast accuracies. The results show that the outcome of the evaluation varies significantly depending on the criteria adopted in the data selection