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TL;DR: This study indicates that mooring workspace and equipment design deficiencies are related to the limited deck space, which is primarily maximized for ship cargo.
8 citations
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08 Jun 2014TL;DR: The derivation of the efficiency weights originally proposed is discussed, and the potential for defining new weights in light of increased array-to-inverter (DC- to-AC) system rating ratios in modern PV systems is investigated.
Abstract: The Sandia Inverter Performance Test Protocol defined two possible weighted-average efficiency values for use in comparing inverter performance, of which one definition was selected by the California Energy Commission for use in their Buydown incentive program leading to widespread use in the photovoltaic inverter market. This paper discusses the derivation of the efficiency weights originally proposed, and investigates the potential for defining new weights in light of increased array-to-inverter (DC-to-AC) system rating ratios in modern PV systems.
8 citations
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25 Sep 2018TL;DR: In this paper, the authors assess the expected development of wind energy towards the availability of the required raw materials up to 2050, and find that wind power is in a favorable position, over solar thermal and photovoltaic power.
Abstract: The installation of new electrical power plants from renewable sources is key in the transition towards a low-carbon economy. An important amount of diverse raw materials is required for this development. Due to its current prominence among renewable energy sources, we assess the expected development of wind energy towards the availability of the required raw materials up to 2050. Wind power is found to be in a favourable position, over solar thermal and photovoltaic power. Among the two main wind turbine technologies, the installation of direct drive turbines with permanent magnets faces a more challenging future. Recycling is an important strategy to simultaneously reduce risks and costs.
8 citations
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01 Jan 2009TL;DR: In this paper, the authors focus on the case of planned disconnect of a completion and work over (CWO) riser, where the analysis is based on an irregular wave approach and the Monte Carlo technique, using time-domain simulations.
Abstract: The term ‘riser recoil’ refers to the situation when the lower end of a top tensioned riser is released, and the riser is lifted up by the riser tensioner and/or top motion compensator system on the supporting vessel. The elastic energy stored in the riser is then released, and the riser ‘recoils’. This paper focuses on the case of planned disconnect. Recoil of Marine Drilling Risers has been the subject of several research papers over the past two decades. Some examples are listed in references [2] through [7]. Completion and Work Over (CWO) risers are unique in the sense that they may be simultaneously connected to both the riser tensioner system and the top motion compensator system of a drilling vessel. A Marine Drilling riser, on the other hand, is only connected to the riser tensioner system. Typically the riser tensioner system has a stroke of ± 8–9 m, whereas the top motion compensator system has only ± 3.5–4 m. It is imperative that the connector is lifted clear of the subsea structure in order to avoid damage to the equipment after the riser has been disconnected. The operating window for planned disconnect of CWO risers is severely limited by the available stroke of the top motion compensator. One of the purposes of the disconnect analysis is to establish the maximum wave height at which there is still sufficient clearance between the connector and the subsea structure after disconnect. Previous experience has shown that this may be the governing limitation for workover operations. The current industry practice is to use a regular wave approach in the analysis. The wave frequency is varied in order to find the maximum response, and hence one is actually searching for the extreme response, without paying attention to the probability that this will occur. In this paper a new method is presented, where the analysis is based on an irregular wave approach and the Monte Carlo technique, using time-domain simulations. Acceptance criteria are established based on a stochastic analysis, and are based on target levels of probability of exceedance. The results are documented through a case study of a typical CWO riser system connected to a semi-submersible in typical North Sea environmental conditions. The semi-submersible and the CWO riser system are exposed to both regular and irregular waves. Comparison of the resulting allowable wave height indicates that using the approach presented here with irregular waves will give a considerable increase in the operating window, and the resulting operability, compared to a regular wave analysis.Copyright © 2009 by ASME
8 citations
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01 Jan 1980TL;DR: In this article, a procedure to calculate horizontal slow drift excitation forces on an infinitely long horizontal cylinder in irregular beam sea waves is presented, where the hydrodynamic boundary value problem is solved correctly to second order in wave amplitude.
Abstract: A procedure to calculate horizontal slow drift excitation forces on an infinitely long horizontal cylinder in irregular beam sea waves is presented. The hydrodynamic boundary-value problem is solved correctly to second order in wave amplitude. Results in the form of second order transfer functions are presented for different two-dimensional shapes. It is concluded that Newman's approximative method is a practical way to calculate slow drift excitation forces on a ship in beam sea and suggested that it may be used in a more general case. Applications of the results for moored ships are discussed.
8 citations
Authors
Showing all 1935 results
Name | H-index | Papers | Citations |
---|---|---|---|
Sergio A. Jimenez | 84 | 416 | 28486 |
Hao Yu | 81 | 981 | 27765 |
Clifford Nass | 65 | 195 | 22615 |
Odd M. Faltinsen | 50 | 247 | 11374 |
Otilia Mó | 46 | 382 | 8641 |
Zefeng Zhou | 38 | 84 | 8653 |
Asgeir J. Sørensen | 35 | 221 | 4459 |
Michael Havbro Faber | 33 | 260 | 4372 |
Deborah Greaves | 31 | 194 | 3141 |
Alessandro Toffoli | 30 | 117 | 2494 |
Yang Miang Goh | 27 | 53 | 2051 |
Narasi Sridhar | 27 | 202 | 3017 |
Elzbieta M. Bitner-Gregersen | 26 | 109 | 2234 |
Jørgen Amdahl | 26 | 150 | 2157 |
Christopher D. Taylor | 25 | 143 | 2840 |