Experimental determination of the overturning moment and net lateral force generated by a novel vertical axis wind turbine: experiment design under load uncertainty

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

New reduction factor for Cracked Square hollow section K-joints

Cracks are commonly observed at the hot spot stress location of tubular joints and it can be due to fatigue, accidental damage or corrosion. As a consequence, the plastic collapse load (Pc) of the tubular joints is reduced, and hence it is necessary to produce design guidance which can safely be used to estimate the static residual strength of cracked tubular structures in practice. This paper proposes a new expression for determining the reduction factor (FAR) of cracked square hollow section (SHS) K-joints. A completely new and robust finite element mesh generator which is validated using the full scale experimental test results is used for the parametric study to propose the new FAR expressions for cracked SHS K-joints. The crack area and the brace to chord width ratio (β) are shown to have the most profound effect on the Pc load of cracked SHS K-joints. For a given value of crack area, the variation of the FAR values is up to 3.6% for different values of β. Furthermore, the FAR values calculated using the existing equation given in the latest BS 7910:2013 + A1:2015 for circular hollow section (CHS) joints are revealed to be conservative up to 23.5%

Influence of statistical uncertainty of component reliability estimations on offshore wind farm availability

Offshore wind turbine reliability, one of the industry's biggest sources of uncertainty, is the focus of the present paper. Specifically the impact of uncertain component failure distributions at constant failure rates has been investigated with respect to its implications for wind farm availability. A fully probabilistic offshore wind simulation model has been applied to quantify results; effects shown in this paper underline the significant impact that failure probability distributions have on asset performance evaluation. It was found that wind farm availability numbers may vary in the range up to 20 % just by changing the distributions of failure to a different pattern; in particular those scenarios in which extensive failure accumulation occurred led to significant losses in production. Results are interpreted and discussed mainly from the viewpoint of an offshore wind farm developer, owner and operator, with implications underlined for application in state-of-the-art offshore wind O&M (Operations and Maintenance) models and simulation tools

Corrosion fatigue crack growth mechanisms in offshore monopile steel weldments

Offshore structures are generally fabricated of welded joints, which are considered as potential spots for crack initiation owing to the degree of stress concentrations imposed by the weld geometry and the effects of residual stresses introduced by welding processes. There are significant numbers of the current and anticipated offshore installations coupled with the use of newer materials and fabrication techniques. It is therefore important to understand the crack growth mechanisms in these structures accompanied with the effects of mean or residual stresses for a safe estimation of their service lives. In this paper, crack growth results of HAZ and weld materials similar to those used for offshore installations are presented. Tests were conducted in air and in simulated free-corrosion conditions at loading frequencies of 0.3 Hz in seawater, 5 Hz in air and at loading ratios of 0.1, 0.5 and 0.7. Results showed that crack growth rates were influenced by mean stresses, materials microstructure accompanied by welding procedure and environment. Crack growth results showed good agreement when compared with those obtained from other steels used for offshore structures

A systematic review of keys challenges of CO2 transport via pipelines

Transport of carbon dioxide (CO2) via pipeline from the point of capture to a geologically suitable location for either sequestration or enhanced hydrocarbon recovery is a vital aspect of the carbon capture and storage (CCS) chain. This means of CO2 transport has a number of advantages over other means of CO2 transport, such as truck, rail, and ship. Pipelines ensure continuous transport of CO2 from the capture point to the storage site, which is essential to transport the amount of CO2 captured from the source facilities, such as fossil fuel power plants, operating in a continuous manner. Furthermore, using pipelines is regarded as more economical than other means of CO2 transport The greatest challenges of CO2 transport via pipelines are related to integrity, flow assurance, capital and operating costs, and health, safety and environmental factors. Deployment of CCS pipeline projects is based either on point-to-point transport, in which case a specific source matches a specific storage point, or through the development of pipeline networks with a backbone CO2 pipeline. In the latter case, the CO2 streams, which are characterised by a varying impurity level and handled by the individual operators, are linked to the backbone CO2 pipeline for further compression and transport. This may pose some additional challenges. This review involves a systematic evaluation of various challenges that delay the deployment of CO2 pipeline transport and is based on an extensive survey of the literature. It is aimed at confidence-building in the technology and improving economics in the long run. Moreover, the knowledge gaps were identified, including lack of analyses on a holistic assessment of component impurities, corrosion consideration at the conceptual stage, the effect of elevation on CO2 dense phase characteristics, permissible water levels in liquefied CO2, and commercial risks associated with project abandonment or cancellation resulting from high project capital and operating costs

Conceptual energy and water recovery system for self-sustained nano membrane toilet

With about 2.4 billion people worldwide without access to improved sanitation facilities, there is a strong incentive for development of novel sanitation systems to improve the quality of life and reduce mortality. The Nano Membrane Toilet is expected to provide a unique household-scale system that would produce electricity and recover water from human excrement and urine. This study was undertaken to evaluate the performance of the conceptual energy and water recovery system for the Nano Membrane Toilet designed for a household of ten people and to assess its self-sustainability. A process model of the entire system, including the thermochemical conversion island, a Stirling engine and a water recovery system was developed in Aspen Plus®. The energy and water recovery system for the Nano Membrane Toilet was characterised with the specific net power output of 23.1 Wh/kgsettledsolids and water recovery rate of 13.4 dm3/day in the nominal operating mode. Additionally, if no supernatant was processed, the specific net power output was increased to 69.2 Wh/kgsettledsolids. Such household-scale system would deliver the net power output (1.9–5.8 W). This was found to be enough to charge mobile phones or power clock radios, or provide light for the household using low-voltage LED bulbs

Geomiso TNL: A Software for Non-Linear Static T-Spline-Based Isogeometric Analysis of Complex Multi-Patch Structures

A new software, Geomiso TNL, is proposed to facilitate the use of isogeometric analysis and 3D design with NURBS and T-splines. Its dual nature eliminates geometric errors by merging geometric design with mesh generation into a single procedure. It is based on the isogeometric method, the powerful generalization of the traditional finite element method. This paper presents four sample applications in non-linear solid and structural mechanics. This software is seen to handle these situations remarkably well, as the numerical examples exhibit significantly improved accuracy of the results, such as displacement, strain and stress fields, and reduced computational cost when compared with finite element analysis. It is argued that Geomiso TNL is a new, more efficient, alternative to finite element software packages and possesses several advantages

An experimental investigation of the combustion performance of human faeces

Poor sanitation is one of the major hindrances to the global sustainable development goals. The Reinvent the Toilet Challenge of the Bill and Melinda Gates Foundation is set to develop affordable, next-generation sanitary systems that can ensure safe treatment and wide accessibility without compromise on sustainable use of natural resources and the environment. Energy recovery from human excreta is likely to be a cornerstone of future sustainable sanitary systems. Faeces combustion was investigated using a bench-scale downdraft combustor test rig, alongside with wood biomass and simulant faeces. Parameters such as air flow rate, fuel pellet size, bed height, and fuel ignition mode were varied to establish the combustion operating range of the test rig and the optimum conditions for converting the faecal biomass to energy. The experimental results show that the dry human faeces had a higher energy content (∼25 MJ/kg) than wood biomass. At equivalence ratio between 0.86 and 1.12, the combustion temperature and fuel burn rate ranged from 431 to 558 °C and 1.53 to 2.30 g/min respectively. Preliminary results for the simulant faeces show that a minimum combustion bed temperature of 600 ± 10 °C can handle faeces up to 60 wt.% moisture at optimum air-to-fuel ratio. Further investigation is required to establish the appropriate trade-off limits for drying and energy recovery, considering different stool types, moisture content and drying characteristics. This is important for the design and further development of a self-sustained energy conversion and recovery systems for the NMT and similar sanitary solutions

A congestion-free vehicle route reservation architecture

Transportation research is mainly focused on answering the question of how to eliminate traffic congestion over large scale areas. Inasmuch as a large portion of big cities suffers from traffic congestion with severe (in many cases) consequences on personal mobility. Drawbacks of congestion include driver delay and frustration, higher fuel consumption, air pollution and financial losses (in terms of man-hours lost on working days). Congestion has, traditionally, been a difficult problem to tackle since traffic demand fluctuates dynamically. The major cause of congestion is that a portion of the network is conferred to accommodate higher number of vehicles than its actual capacity. Nonetheless, congestion usually occurs due to lack of an efficient management of transport network utilization and not because demand exceeds network's capacity [1]. Therefore, it is possible to alleviate congestion if vehicles are more effectively distributed over the entire network achieving better load balancing. • "© 20xx IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, in-cluding reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to serv-ers or lists, or reuse of any copyrighted component of this work in other works. C. Menelaou, P. Kolios, S. Timotheou and C. G. Panayiotou, "A congestion-free vehicle route reservation architecture," 2016 18th Mediterranean Electrotechnical Conference (MELECON), Lemesos, 2016, pp. 1-6. doi: 10.1109/MELCON.2016.7495458 • https://www.ieee.org/publications_standards/publications/rights/rights_policies.html Document type: Conference objec

On the Complexity of Congestion Free Routing in Transportation Networks

Traffic congestion has been proven a difficult problem to tackle, particularly in big cities where the number of cars are steadily increasing while the infrastructure remains stagnant. Several approaches have been proposed to alleviate the effects of traffic congestion, however, so far congestion is still a big problem in most cities. In this work we investigate a new route reservation approach to address the problem which is motivated by air traffic control. This paper formulates the route reservation problem under different assumptions and examines the complexity of the resulting formulations. Two waiting strategies are investigated, (i) vehicles are allowed to wait at the source before they start their journey, and (ii) they are allowed to wait at every road junction. Strategy (i) though more practical to implement, results to an NP-complete problem while strategy (ii) results to a problem that can be solved in polynomial time but it is not easily implemented since the infrastructure does not have adequate space for vehicles to wait until congestion downstream is cleared. Finally, a heuristic algorithm (based on time-expanded networks) is derived as a solution to both proposed waiting strategies. © 20xx IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works C. Menelaou, P. Kolios, S. Timotheou and C. Panayiotou, "On the Complexity of Congestion Free Routing in Transportation Networks," 2015 IEEE 18th International Conference on Intelligent Transportation Systems, Las Palmas, 2015, pp. 2819-2824. doi: 10.1109/ITSC.2015.453 Document type: Conference objec