Browsing by Author "Kolios, Athanasios J."
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Item Open Access CranSLIK v1.0: stochastic prediction of oil spill transport and fate using approximation methods(2015-07-22T00:00:00Z) Snow, Ben J.; Moulitsas, Irene; Kolios, Athanasios J.; De Dominicis, MichelaOil spill models are used to forecast the transport and fate of oil after it has been released. CranSLIK is a model that predicts the movement and spread of a surface oil spill at sea via a stochastic approach. The aim of this work is to identify parameters that can further improve the forecasting algorithms and expand the functionality of CranSLIK, while maintaining the run-time efficiency of the method. The results from multiple simulations performed using the operational, validated oil spill model, MEDSLIK-II, were analysed using multiple regression in order to identify improvements which could be incorporated into CranSLIK. This has led to a revised model, namely CranSLIK v2.0, which was validated against MEDSLIK-II forecasts for real oil spill cases. The new version of CranSLIK demonstrated significant forecasting improvements by capturing the oil spill accurately in real validation cases and also proved capable of simulating a broader range of oil spill scenarios.Item Open Access CranSLIK v2.0: improving the stochastic prediction of oil spill transport and fate using approximation methods(European Geosciences Union, 2015-10-26) Rutherford, R.; Moulitsas, Irene; Snow, Ben J.; Kolios, Athanasios J.; De Dominicis, MichelaOil spill models are used to forecast the transport and fate of oil after it has been released. CranSLIK is a model that predicts the movement and spread of a surface oil spill at sea via a stochastic approach. The aim of this work is to identify parameters that can further improve the forecasting algorithms and expand the functionality of CranSLIK, while maintaining the run-time efficiency of the method. The results from multiple simulations performed using the operational, validated oil spill model, MEDSLIK-II, were analysed using multiple regression in order to identify improvements which could be incorporated into CranSLIK. This has led to a revised model, namely CranSLIK v2.0, which was validated against MEDSLIK-II forecasts for real oil spill cases. The new version of CranSLIK demonstrated significant forecasting improvements by capturing the oil spill accurately in real validation cases and also proved capable of simulating a broader range of oil spill scenarios.Item Open Access Design and commissioning of a multi-mode prototype for thermochemical conversion of human faeces(Elsevier, 2018-03-23) Jurado Pontes, Nelia; Somorin, Tosin; Kolios, Athanasios J.; Wagland, Stuart; Patchigolla, Kumar; Fidalgo, Beatriz; Parker, Alison; McAdam, Ewan; Williams, Leon; Tyrrel, SeanThis article describes the design and commissioning of a micro-combustor for energy recovery from human faeces, which can operate both in updraft and downdraft modes. Energy recovery from faecal matter via thermochemical conversion has recently been identified as a feasible solution for sanitation problems in low income countries and locations of high income countries where access to sewage infrastructures is difficult or not possible. This technology can be applied to waterless toilets with the additional outcome of generating heat and power that can be used to pre-treat the faeces before their combustion and to ensure that the entire system is self-sustaining. The work presented here is framed within the Nano Membrane Toilet (NMT) project that is being carried out at Cranfield University, as part of the Reinvent the Toilet Challenge of the Bill and Melinda Gates Foundation. For this study, preliminary trials using simulant faeces pellets were first carried out to find out the optimum values for the main operating variables at the scale required by the process, i.e. a fuel flowrate between 0.4 and 1.2 g/min of dry faeces. Parameters such as ignition temperature, residence time, and maximum temperature reached, were determined and used for the final design of the bench-scale combustor prototype. The prototype was successfully commissioned and the first experimental results, using real human faeces, are discussed in the paper.Item Open Access Design of novel experimental facility for testing of tidal arrays(MDPI, 2013-08-12T00:00:00Z) Pintar, Matevz; Kolios, Athanasios J.In order to obtain the maximum amount of energy from tidal stream extraction devices, deployment in large arrays should be studied. The area of seabed with favorable conditions is fairly limited; therefore layout spacing has to be optimized. In this paper a feasibility study for a novel experimental facility, suitable for the testing of an array of tidal devices, is presented. To avoid space and scale limitations of towing tanks, testing is proposed to be performed in large lakes or calm seas using a self-propelled vessel, which will carry an array of devices with variable spacing, creating relevant speed differences and measuring their performance and loading. Using hydrodynamic scaling laws, an appropriate size for test turbines and the range of vessel speed was determined to fulfill experimental requirements. Computational fluid dynamic simulations, using the actuator disc method, have suggested a suitable turbine array configuration to resemble real application conditions. A simplified model of the vessel was analyzed using the finite elements method to determine the main scantlings. The hull resistance calculated by empirical formulae was found to be negligible compared to the resistance of the tested turbine. It was confirmed that turbine size and speed determined by scaling laws are also reasonable from a propulsion point of view.Item Open Access Environmental impact assessment of the manufacturing of a commercial aircraft(2013-09-02T00:00:00Z) Kolios, Athanasios J.; Howe, Stuart; Asproulis, Nikolaos; Salonitis, Konstantinos; Shehab, Essam; Ball, Peter D.; Tjahjono, BennyThis paper documents the methodology and presents the results of a comprehensive LCA study of an Airbus A320 commercial airliner to determine the relative environmental impact of its manufacturing phase. The study was conducted in accordance with ISO 14040/44 using SimaPro LCA software, the EcoInvent inventory database and Eco-Indicator 99 weighting method, which allows the analysis to be outputted in a single score representing a number of damage models including damage to human health, ecosystem quality or resource depletion. Results indicate CFRP wings to have the most significant contribution to the overall environmental impact as a proportion to mass.Item Open Access Faeces - Urine separation via settling and displacement: Prototype tests for a novel non-sewered sanitation system(Elsevier, 2020-08-23) Hennigs, Jan; Ravndal, Kristin T.; Parker, Alison; Collins, Matt; Jiang, Ying; Kolios, Athanasios J.; McAdam, Ewan; Williams, Leon; Tyrrel, Sean F.The development of novel, non-sewered sanitation systems like the Nano Membrane Toilet requires thorough investigation of processes that may seem well-understood. For example, unlike the settling of primary sludge, the separation of solids from liquids in a small-volume container at the scale of a household toilet has not been studied before. In two sets of experiments, the settling of real faeces and toilet paper in settling columns and the settling of synthetic faeces in a conical tank are investigated to understand the factors affecting the liquid quality for downstream treatment processes. Toilet paper is found to be a major inhibitor to settling of solids. While a lower overflow point results in better phase separation through displacement of liquid, a higher overflow point and frequent removal of solids may be more advantageous for the liquid qualityItem Open Access Failure mode and effects analysis using a fuzzy-TOPSIS method: a case study of subsea control module(Inderscience, 2017-07-03) Kolios, Athanasios J.; Umofia, Anietie; Shafiee, MahmoodFailure mode and effects analysis (FMEA) is one of the most common reliability engineering techniques used for identifying, evaluating and mitigating the engineering risks. In this paper, the potential failure modes of a subsea control module (SCM) are identified based on industry experts' opinions and experiences. This is followed by a comprehensive component based FMEA study using the risk-priority-number (RPN) where the most critical failure modes in the SCM are revealed. A fuzzy TOPSIS-based multiple criteria decision making methodology is then proposed to analyse and prioritise the most critical failure modes identified by the FMEA study. To this aim, a distinct ten-parameter criticality model is developed and, for the first time, is applied to evaluate the risks associated with SCM failures. The results indicate that the proposed fuzzy TOPSIS model can significantly improve the performance and applicability of the conventional FMEA technique in offshore oil and gas industry.Item Open Access Field testing of a prototype mechanical dry toilet flush(Elsevier, 2019-02-17) Hennigs, Jan; Ravndal, Kristin T.; Blose, Thubelihle; Toolaram, Anju; Sindall, Rebecca C.; Barrington, Dani J.; Collins, Matt; Engineer, Bhavin; Kolios, Athanasios J.; McAdam, Ewan; Parker, Alison; Williams, Leon; Tyrrel, SeanA prototype of a non-fluid based mechanical toilet flush was tested in a semi-public, institutional setting and in selected peri-urban households in eThekwini municipality, Republic of South Africa. The mechanism's functionality and users' perception of the flush were assessed. User perception varied depending on background: Users accustomed to porcelain water flush toilets were open to, yet reserved about the idea of using a waterless flush in their homes. Those who commonly use Urine Diversion Dehydration Toilets were far more receptive. The user-centred field trials were complemented by a controlled laboratory experiment, using synthetic urine, -faeces, and -menstrual blood, to systematically assess the efficiency of three swipe materials to clean the rotating bowl of the flush. A silicone rubber with oil-bleed-effect was found to be the best performing material for the swipe. Lubrication of the bowl prior to use further reduced fouling. A mechanical waterless flush that does not require consumables, like plastic wrappers, is a novelty and could – implemented in existing dry toilet systems – improve acceptance and thus the success of waterless sanitation.Item Open Access Life-cycle assessment of self-generated electricity in Nigeria and Jatropha biodiesel as an alternative power fuel(Elsevier, 2017-06-21) Somorin, Tosin Onabanjo; Di Lorenzo, Giuseppina; Kolios, Athanasios J.Insufficient available energy has limited the economic growth of Nigeria. The country suffers from frequent power outages, and inconvenient black–outs while residents and industries are forced to depend on self-generated electricity. Life-cycle assessment methodology was used to assess the environmental burdens associated with self-generated electricity (SGE) and proposed embedded power generation in Nigeria. The study shows that SGE from 5 kVA diesel generators contributes to greenhouse gas (GHG) emissions of 1625 kg CO2 eq./MWh, along with other environmental burdens. Based on a point estimate of diesel electric generators in Nigeria, SGE can contribute 389 million tonnes CO2 eq. to climate change every year. This can reposition Nigeria as one of the top 20 emitters of CO2 globally. A mandatory diesel fuel displacement with Jatropha biodiesel can reduce annual GHG emissions from SGE by 76% provided combined cycle power plants are adopted for embedded power generation. The magnitude of these benefits would depend on material inputs, seed yield as well as the environmental status of the reference fuel. Minimal use of fertilizers, chemicals and resources and fossil fuel substitution with renewable options can minimize adverse environmental burdens.Item Open Access A Political, Economic, Social, Technology, Legal and Environmental (PESTLE) Approach for Risk Identification of the Tidal Industry in the United Kingdom(MDPI AG, 2013-09-27T00:00:00Z) Kolios, Athanasios J.; Read, G.This paper presents a comprehensive analysis of renewable and especially tidal energy through a political, economic, social, technology, legal and environmental (PESTLE) analysis approach and by reviewing the most up to date relevant literature. The study focuses on the United Kingdom given the favourable environmental resources for such technologies; the number of different design concepts that are currently under development as well as the research funding that has been invested over the last few years. Findings of the analysis identify the risks and multiple stakeholders involved at all stages of the tidal energy projects development from the conceptualization of the design, right through to decommissioning. Many of the stakeholders present benefits to the tidal developers through funding, incentives and knowledge sharing, but at the same time they also present potential risks to the future of projects. This is mostly down to different approaches of the most important aspect of tidal energy that needs to be considered, making it hard for technologists and developers to equally address all requirements. From this research it can be concluded that several of these risks can be mitigated early on providing that particular stakeholders are involved at the correct stage of a project.Item Open Access Reanalysis of offshore T-joint fatigue life predictions based on a complete weld profile model(Elsevier, 2014-06-20) Lozano-Minguez, Estívaliz; Brennan, Feargal Peter; Kolios, Athanasios J.A comparison between the fatigue life predictions obtained by the stress concentration factors (SCFs) of 3D solid finite element (FE) models considering the weldment and the existing SCF parametric equations for tubular T-joints, is presented in this paper. From the study carried out, it was concluded that the existing parametric equations for predicting hot spot SCFs are very conservative and insufficient to be used for optimisation. SCFs should be carried out by modelling 3D solid joints which include the weldment and should be based on notch stresses measured on the external surface at the weld toe. The Offshore and Marine Renewable Energy industry could significantly reduce their investment costs using contemporary FE models, since slight overestimations of the SCF results in a corresponding large reduction in predicted service life.Item Open Access Reliability of floating foundation concepts for vertical axis wind turbines(2010-12-31T00:00:00Z) Kolios, Athanasios J.; Collu, Maurizio; Brennan, Feargal P.; Sphaler, S. H.; Estefen, S. F.; Pasqualino, I. P.Offshore wind turbines are developing at a rapid pace. By far the most common turbine configuration is the HAWT (Horizontal Axis Wind Turbine) and development of these machines is largely centered about drive train and blade issues with some work concerning foundations/ supporting structures. Several teams around the world are developing floating supporting structures for HAWT, mainly for deep water deployment. This paper describes the development of a floating support structure for Vertical Axis Wind Turbines (VAWT) with particular focus on structural/survival risk and reliability. Unlike Oil & Gas floating support structures, wind turbine floaters need to resist significant dynamic wind and machine loading in addition to wave excitation. Coupling of dynamic response modes can be difficult and consideration of these within a reliability framework presents several challenges. The paper describes a simplified procedure for risk assessment so that potential areas of concern can be quickly identified and uses a VAWT to illustrate the methods and reasoning employed.Item Open Access Thermodynamic analysis of a gamma type Stirling engine in an energy recovery system(Elsevier, 2018-04-01) Sowale, Ayodeji; Kolios, Athanasios J.; Fidalgo, Beatriz; Somorin, Tosin; Parker, Alison; Williams, Leon; Collins, Matt; McAdam, Ewan; Tyrrel, SeanThe demand for better hygiene has increased the need for developing more effective sanitation systems and facilities for the safe disposal of human urine and faeces. Non-Sewered Sanitary systems are considered to be one of the promising alternative solutions to the existing flush toilet system. An example of these systems is the Nano Membrane Toilet (NMT) system being developed at Cranfield University, which targets the safe disposal of human waste while generating power and recovering water. The NMT will generate energy from the conversion of human waste with the use of a micro-combustor; the heat produced will power a Stirling engine connected to a linear alternator to generate electricity. This study presents a numerical investigation of the thermodynamic analysis and operational characteristics of a quasi steady state model of the gamma type Stirling engine integrated into a combustor in the back end of the NMT system. The effects of the working gas, at different temperatures, on the Stirling engine performance are also presented. The results show that with the heater temperature of 390 °C from the heat supply via conduction at 820 W from the flue gas, the Stirling engine generates a daily power output of 27 Wh/h at a frequency of 23.85 Hz.