1,721,029 research outputs found
Autosub6000: a deep diving long range AUV
Get PDFWith an ultimate range up to 1000 km, a maximum operating depth of 6000 m, and a generous payload capacity, Autosub6000 is well placed to become one of the world's most capable deep diving Autonomous Underwater Vehicles (AUVs). Recently, Autosub6000 successfully completed its first deep water engineering trials, and in September 2008, fitted with a multibeam sonar, will carry out its first science missions. This paper will describe how we are tackling the design issues that specifically affect a deep diving AUV which must be capable of operating with true autonomy, independently of the mother ship, namely: carrying adequate energy for long endurance and range, coping with varying buoyancy, and maintaining accurate navigation throughout missions lasting up to several days. Results from the recent engineering trails are presented, and future missions and development plans are discussed
Fuel Cells in the Waste-to-Energy Chain: Distributed Generation Through Non-Conventional Fuels and Fuel Cells
No full textAs the availability of fossils fuels becomes more limited, the negative impact of their consumption becomes an increasingly relevant factor in our choices with regards to primary energy sources. The exponentially increasing demand for energy is reflected in the mass generation of by-products and waste flows which characterize current society’s development and use of fossil sources. The potential for recoverable material and energy in these ever-increasing refuse flows is huge, even after the separation of hazardous constituent elements, allowing safe and sustainable further exploitation of an otherwise 'wasted' resource. Fuel Cells in the Waste-to-Energy Chain explores the concept of waste-to-energy through a 5 step process which reflects the stages during the transformation of refuse flows to a valuable commodity such as clean energy. By providing selected, integrated alternatives to the current centralized, wasteful, fossil-fuel based infrastructure, Fuel Cells in the Waste-to-Energy Chain explores how the concept of waste-to-energy can be constructed and developed into a realistic solution. The entire spectrum of current and future energy problems is illuminated through the explanation of the operational, integration and marketing implications of high efficiency technological solutions using the real context of developed regions such as Europe. Up-to-date reviews are provided on the status of technology and demonstration, implementation and marketing perspectives. The detailed technological information and insight gathered from over twenty years of experience in the field makes Fuel Cells in the Waste-to-Energy Chain a valuable resource for all engineers and researchers in the fields of energy supply systems and waste conversion, as well as providing a key reference for discussions by policy makers, marketing experts and industry developers working in energy supply and waste management
Range-only positioning of a deep-diving Autonomous Underwater Vehicle from a surface ship
No full textThis paper describes a method for the precise postprocessed
positioning of a deep-diving autonomous underwater vehicle
(AUV) using only a set of acoustic ranges from a surface ship
while the AUV executes a closed path under the ship. This approach
avoids the use of either a precisely calibrated (and consequently
expensive) ultrashort baseline (USBL), or a long baseline
(LBL) system (which is expensive in ship time to deploy). Results of
Monte Carlo simulation and field results from the first trials of the
Autosub6000 AUV are presented to support the hypothesis that an
AUV at 6000-m depth can be positioned to an accuracy commensurate
with global positioning system (GPS) quality or better, within
a period of 1 h
A New Collision Avoidance System for the Autosub6000 Autonomous Underwater Vehicle
No full textThe recently developed Autosub6000 Autonomous Underwater Vehicle (AUV) is the latest in the Autosub series of AUVs that
have been built at the National Oceanography Centre, Southampton. The previous AUV have been deployed on numerous science missions over the last decade. Autosub6000, with its 6000m depth capability, is currently in demand for deep ocean bathymetric surveys using its Simrad EM2000 multibeam sonar system. However, the terrain that can currently be surveyed is limited due to the lack of an obstacle avoidance system. In order to survey rugged and challenging regions a new obstacle avoidance system is being developed. This system uses a Tritech Seaking mechanically scanned sonar system oriented to scan vertically in front of the AUV to provide details of obstacles as well as changes in terrain. This paper describes the obstacle avoidance approach adopted and outlines its implemenation within Autosub6000. Simulation outputs showing the performance of the system are presented and results from trials of the Tritech Seaking sonar are also given
Life cycle inventory data and metrics for high-temperature fuel cells: A streamlined decision-support tool and case study application
No full textIn recognition of the growing global importance of high-temperature fuel cells (HTFCs) as future energy systems, their commercial market take-off needs to be supported by life-cycle performance metrics. However, research and application of life cycle approaches and tools are not broadly reflected in fuel cell and hydrogen energy technologies due to technical barriers to data collection and analyzing instruments. In this work, an interactive Excel-based decision support system (DSS) for power-to-gas-to-power life cycle assessment (LCA) and techno-economic analysis is presented. The aim of the proposed model is two-fold. Firstly, promote the availability, exchange, and use of coherent and quality-assured life cycle data in a systematic and uniform way. Secondly, serves as guidance model for scale-up and enable non-expert users to improve the knowledge-base of FC life-cycle performance and set up product eco-profiles at the conceptual design stage of a project. The tool uses cutting-edge LCA methodology LCA-ReCiPe 2016 for key environmental performance indicators and a simple levelized cost of energy (electricity or fuel) for the economic attractiveness. The applicability of the model is tested through a case study on Solid Oxide Fuel Cells (SOFC) demonstrating the capability to acknowledge the trade-offs between possible impacts
The yellow pages of SOFC technology. International Status of SOFC deployment 2017
Get PDFLe celle a combustibile ad ossidi solidi (SOFC) sono una tecnologia di frontiera per convertire l’energia chimica di idrocarburi fossili o rinnovabili in elettricità e calore, attraverso una reazione elettrochimica. Decenni di ricerca e sviluppo stanno dando i loro frutti, e sono già numerose le applicazioni per la generazione di potenza elettrica pulita ed affidabile presso consumatori in tutto il mondo. Le SOFC possono utilizzare gas naturale, biogas e combustibili liquidi per la generazione di potenza elettrica e calore a efficienze record (fino al 60% netto di efficienza elettrica di sistema) anche a piccola scala e a carico parziale. Il potenziale di questa tecnologia è enorme e imprese dinamiche emergono in tutto il mondo, che trasformano le SOFC in prodotto, portandole a mercati diversi e variegati: potenza portatile, micro-cogenerazione, cogenerazione a scala commerciale, generatori di potenza ausiliare. In questo Dossier, viene riportata una panoramica concisa ma completa della diffusione a livello industriale della tecnologia e delle applicazioni SOFC nel mondo. Tutti gli sviluppatori principali delle SOFC vengono profilati: vengono descritti la loro tecnologia specifica, i loro prodotti e i loro mercati – a dimostrazione che la generazione di energia pulita, silenziosa ed affidabile sta diventando una realtà commerciale
Autosub6000: results of its engineering trials and first science missions
Get PDFIn September 2007 on RRS Discovery, the Autosub6000 Autonomous Underwater Vehicle (AUV)
completed its first deep water engineering trials, and less than a year later, fitted with a multibeam
bathymetric mapping sonar, carried out its first science missions, as part of a geology and
geophysics science cruise onboard the RRS James Cook to investigate potential geo-hazards
(such as tsunami generating landslides) on the European and North African margin. In the spirit of
true AUV autonomy, while the AUV was deployed, we used the ship for seabed coring operations,
and once the AUV was recovered, the high resolution bathymetry which it had obtained guided
the next coring operations. In this paper we will describe how we are tackling the issues that
specifically affect a deep diving AUV capable of operating with true autonomy, and independently
of the mother ship: How to carry enough energy for long endurance and range? How to operate
safely and efficiently with varying buoyancy? How to maintain accurate navigation throughout
missions lasting up to several days
Proceedings of the 6th European fuel cell. Piero Lunghi Conference, Naples 16-18 December, 2015
No full textA concept design for an ultra-long-range survey class AUV
Get PDFGliders and flight-style Autonomous Underwater Vehicles (AUVs) are used to perform perform autonomous surveys of large areas of open ocean. Glider missions are characterized by their profiling flight pattern, slow speed, long range (1000s of km) and many month mission duration. Flight-style AUV missions are faster, of shorter range (100s of km) and multi day duration. An AUV combining many aspects of both vehicle classes would be of considerable value.This paper investigates the factors that affect the range of a
traditional flight-style AUVs. A generic range model is outlined
which factors in the effects of buoyancy on the range. The model
shows that to create a very long range AUV it is necessary to reduce the hotel load on the AUV to the order of 1W and to add wings to overcome the vehicle’s positive buoyancy whilst travelling at the reduced speed required for long range.Using this model a concept long range AUV is outlined that is capable of travelling up to 5000km. The practical issues associated with achieving this range are also discussed
On the Dynamics of Solid Oxide Fuel Cell Stacks: Preliminary Model-Driven Monitoring
No full textThe inexorable inclusion of high temperature fuel cells in the energy grid of the world’s major economies accentuates the needs for more robust systems capable of tolerating non-stationary conditions with minor degradation. It seems undeniable that the latter needs to be addressed mainly by basic and applied research on the fuel cell stack components (electrodes, interconnects, etc...), yet there is still space for performance improvement by optimising system integration. This paper encompasses the experimental procedure used to fully characterise a 6-cell intermediate temperature solid oxide fuel cell (IT-SOFC) short stack when operating in non-stationary conditions and in dissimilar load demands, fuel flows, fuel utilisations and temperatures, simulating to some extent a real-life appliance capable of following electrical load and/or heat demand. The spanning of such input factors allows generating a space-matrix of variables – voltages, temperatures and output gas compositions – that describe the system’s dynamic and stationary performance considering null degradation. This experimental approach can produce appropriate values so as to generate simple autoregressive models suitable for real-time one-step-ahead predictions of the output variables. In this work, the most effective mathematical correlation between the numerous inputs and outputs resulted to be a non-linear autoregressive exogenous (ARX) model built by means of a treepartition algorithm (i.e. binary search trees). The normalised root mean square error (NRMSE) of the calculated fit of the train data was above 94% in all of the cases denoting that the model simulates exceptionally well the system’s outputs in the studied ranges. Additionally, the model was validated with test data, more particularly a dynamic current-voltage curve, and the results show how the simulated points follow remarkably well the experimental results. It must be noted that the electrical current imposed to the SOFC stack in the test data ranged from 5A to 20A, which is the range in which the model performs best; nevertheless outside these bounds the model is capable of simulating exceptionally well the voltage output, especially at high current densities. This dynamic model can be of great use for preliminary design & control of power plants incorporating nominal size stacks from the same manufacturer/integrator by increasing the understanding of how the plant will perform when in transient conditions. Furthermore, the present model is capable of assessing online the degradation rate of a fuel cell stack by comparing the experimental results with the expected ones from the model
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