CERES :: Browsing by Author "Kolios, Athanasios J."

Browsing by Author "Kolios, Athanasios J."

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Open Access
Carbon Brainprint Case Study: novel offshore vertical axis wind turbines
(2011-07-31T00:00:00Z) Parsons, David J.; Chatterton, Julia C.; Brennan, Feargal P.; Kolios, Athanasios J.
As part of the transition to a ‘low carbon economy', renewable technologies are expected toplay an increasing role in reducing dependence on fossil fuels for energy and electricity. Windpower in particular is likely to become a much larger contributor to the UK's energy mix. Thecurrent dominant design for large, grid-connected wind turbines is a three blade rotor with ahorizontal rotating axis. The concept of a vertical axis wind turbine (VAWT) is relatively new, buthas several advantages over horizontal axis alternatives. It is able to capture the wind from anydirection, and the vertical axis is such that the rotor equipment is located at base level, makingit is simpler and less costly to install and maintain. The Energy Technologies Institute (ETI) is a UK-based company formed from global industriesand the UK government. One of three projects looking at new turbine design and concepts foroffshore wind is the Novel Offshore Vertical Axis (NOVA) project, a UK-based consortiumlaunched in January 2009 to look at the feasibility of a NOVA turbine. achieved through the installation of NOVA wind turbines, in comparison to conventionalhorizontal axis wind turbines (HAWTs) for offshore power generation. The increased powerrating of the NOVA turbines compared to current HAWTs is expected to provide considerablereductions in lifetime greenhouse gas emissions. It compared the emissions from 1 GWinstallations over 20 years, based on a life cycle analysis of construction, operation anddisposal. The comparison used the popular Vestas V90 3 MW model and the proposed NOVA10 MW units. The estimated lifetime emissions were 521 kt CO2e for the conventional design and419 kt CO2e for NOVA. Using budget share to attribute the reductions to the project partners,Cranfield's brainprint was 34 kt CO2e. As there are no current NOVA units in operation, there were high uncertainties associated withthe estimates. A Monte-Carlo simulation resulted in a mean difference in emissions betweenthe two installations of 102 kt CO2e, with a standard deviation of 108.
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, Michela
Oil 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.
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, Michela
Oil 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.
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, Sean
This 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.
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.
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, Benny
This 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.
Open Access
Experimental determination of the overturning moment and net lateral force generated by a novel vertical axis wind turbine: experiment design under load uncertainty
(Blackwell Publishing Ltd, 2013-01-31T00:00:00Z) Kolios, Athanasios J.; Chahardehi, Amir Ebrahim; Brennan, Feargal P.
Recent developments in harnessing wind energy propose new, radically different designs to alleviate some of the difficulties associated with conventional wind turbines. New designs however require testing for a variety of reasons ranging from gaining confidence in the analytical models used in the design and development through to satisfaction of certification requirements. Medium-scale prototype testing of large-scale concepts, where parameters such as the response of the structure and the loading conditions are often highly uncertain demand special consideration. This article presents the design of a special test rig and calculation methodology for the experimental determination of the overturning moment and net force generated by the NOVA Vertical Axis Wind Turbine using a field experimental setup. The design of the experimental model involves dealing with modelling uncertainties as loads in operation and therefore the response of the structure are largely unknown before testing has been carried out. The variability in the wind speed and direction also need to be accommodated for.
Open Access
Faecal-wood biomass co-combustion and ash composition analysis
(Elsevier, 2017-05-16) Somorin, Tosin; Kolios, Athanasios J.; Parker, Alison; McAdam, Ewan J.; Williams, Leon; Tyrrel, Sean
Fuel blending is a widely used approach in biomass combustion, particularly for feedstocks with low calorific value and high moisture content. In on-site sanitation technologies, fuel blending is proposed as a pre-treatment requirement to reduce moisture levels and improve the physiochemical properties of raw faeces prior to drying. This study investigates the co-combustion performance of wood dust: raw human faeces blends at varying air-to-fuel ratios in a bench-scale combustor test rig. It concludes with ash composition analyses and discusses their potential application and related problems. The study shows that a 50:50 wood dust (WD): raw human faeces (FC) can reduce moisture levels in raw human faeces by ∼40% prior to drying. The minimum acceptable blend for treating moist faeces without prior drying at a combustion air flow rate of 14–18 L/min is 30:70 WD: FC. For self-sustained ignition and flame propagation, the minimum combustion temperature required for conversion of the fuel to ash is ∼400 °C. The most abundant elements in faecal ash are potassium and calcium, while elements such as nickel, aluminium and iron are in trace quantities. This suggests the potential use of faecal ash as a soil conditioner, but increases the tendency for fly ash formation and sintering problems.
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 quality
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, Mahmood
Failure 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.
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, Sean
A 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.
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.
Open Access
Multi-criteria assessment of offshore wind turbine support structures
(Elsevier Science B.V., Amsterdam., 2011-11-30T00:00:00Z) Lozano Minguez, Estivaliz; Kolios, Athanasios J.; Brennan, Feargal P.
Wind power, especially offshore, is considered one of the most promising sources of ‘clean’ energy towards meeting the EU and UK targets for 2020 and 2050. Deployment of wind turbines in constantly increasing water depths has raised the issue of the appropriate selection of the most suitable support structures’ options. Based on experience and technology from the offshore oil and gas industry, several different configurations have been proposed for different operational conditions. This paper presents a methodology for the systematic assessment of the selection of the most preferable, among the different configurations, support structures for offshore wind turbines, taking into consideration several attributes through the widely used multi-criteria decision making method TOPSIS (Technique for Order Preference by Similarity to Ideal Solution) for the benchmarking of those candidate options. An application comparing a monopile, a tripod and a jacket, for a reference 5.5 MW wind turbine and a reference depth of 40 m, considering multiple engineering, economical and environmental attributes, will illustrate the effectiveness of the proposed method
Open Access
Numerical Simulation of Material Strength Deterioration due to Pitting Corrosion
(Elsevier BV, 2014-06-02T00:00:00Z) Kolios, Athanasios J.; Srikanth, Sumant; Salonitis, Konstantinos
Pitting corrosion is an insidious form of localized corrosion affecting characteristics of various engineering metallic alloys. Currently very limited literature exists with regard to systematic characterization of pitted surfaces or the efficient use of numerical methods to assess its effect, i.e. fatigue life reduction caused by the state of a corroded specimen and particularly through the study of stress concentrations considering the geometrical anomalies introduced to a surface. Much of the predictive analysis for corrosion is in fact derived from empirical means. This papers aims at exploring the use of numerical simulation to assess stress concentrating effects of pitting corrosion. Relevant parameters for characterization of pitting corrosion and its intensity are identified through literature review and preliminary simulations. 2-D and 3-D parametric models are subsequently created using stochastic parametric Finite Element Analysis, studying the effect of various randomized characteristics of pitting on the stress concentration factor.
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.
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.
Open Access
Reliability assessment of cutting tools life based on advanced approximation methods
(Elsevier BV, 2013-12-31T00:00:00Z) Salonitis, Konstantinos; Kolios, Athanasios J.
Cutting tools' reliability influences the whole manufacturing efficiency. However, in most cases the same cutting tool may be used for different operations with different processing parameters, making thus difficult to estimate the remaining life of the tool precisely. The present study proposes a new reliability estimation approach to the cutting tools based on advanced approximation methods. Reliability-based design/operation is a technique extensively employed for problems of structural reliability, assessing the performance of critical infrastructure under stochastic design parameters. Due to the complexity of machining processes which involve a significant number of hidden or difficult to statistically model variables, advanced approximation methods, such as response surface or surrogate modelling methods may be applied, starting from a few sample points obtained through fundamental experiments and extending them to models able to predict/estimate the values of control values/indicators as a function of the key design variables, often referred to as limit states. Having constructed such models, and according to the level of probability that need to be measured, different reliability analysis methods can be employed such as Monte Carlo Simulations or First Order Reliability Methods (FORM). In the present study these two reliability analysis methods are assessed for estimating the reliability of cutting tools.
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.
Open Access
Techno-economic optimisation of offshore wind farms based on life cycle cost analysis on the UK
(Elsevier, 2018-08-03) Mytilinou, Varvara; Kolios, Athanasios J.
In order to reduce the cost of energy per MWh in wind energy sector and support investment decisions, an optimisation methodology is developed and applied on Round 3 offshore zones, which are specific sites released by the Crown Estate for offshore wind farm deployments, and for each zone individually in the UK. The 8-objective optimisation problem includes five techno-economic Life Cycle Cost factors that are directly linked to the physical aspects of each location, where three different wind farm layouts and four types of turbines are considered. Optimal trade-offs are revealed by using NSGA II and sensitivity analysis is conducted for deeper insight for both industrial and policy-making purposes. Four optimum solutions were discovered in the range between £1.6 and £1.8 billion; the areas of Seagreen Alpha, East Anglia One and Hornsea Project One. The highly complex nature of the decision variables and their interdependencies were revealed, where the combinations of site-layout and site-turbine size captured above 20% of total Sobol indices in total cost. The proposed framework could also be applied to other sectors in order to increase investment confidence.
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, Sean
The 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.