Evaluating and Improving Logistics Costs During Offshore Wind Turbine Construction
Issue:
Volume 4, Issue 4, December 2018
Pages:
65-74
Received:
7 December 2018
Accepted:
20 December 2018
Published:
11 January 2019
DOI:
10.11648/j.ijtet.20180404.11
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Views:
Abstract: Background: During the whole life cycle of an offshore wind farm, from cradle to grave, logistics is needed. Particularly during wind turbine construction, vessels are intensively used. However, no study has been found to evaluate logistics costs during this particular turbine construction phase. Objective: In order to close this gap, this paper aims to propose an Offshore Logistics Cost (OLC) framework, evaluate OLC impact on total cost and identify recommendations to reduce this impact. Methodology: This study considers two quantitative approaches to evaluate OLC share. First quantitative approach is based on cost information found in twenty related studies from literature. Second quantitative approach was developed in two steps. A first step is a bottom up calculation model. This model performs OLC calculations for each scenario identified. In a second step, OLC results are used as input to two existing calculation models: National Renewable Energy Laboratory (NREL) simplified model and commonly accepted model developed by Megavind. Variance of results are then analyzed to determine a representative range for OLC impact on total cost. Results: Using some related values from literature review, this study assesses wind turbine construction offshore logistics to represent around 1.2% of Levelized Cost of Energy (LCOE). Using bottom up approach, this study evaluates offshore logistics during wind turbine construction with a broader contribution, conservatively from 0.6 to 7.6% of LCOE for offshore wind turbines over 4 MW power rating. It is also demonstrated that the higher the wind turbine size, the lower offshore logistics impact on LCOE. Conclusion: Offshore wind logistics costs during construction phase can represent between 0.6 and 7.6% of LCOE and it appears necessary to optimize these costs to contribute to a competitive LCOE. As main offshore logistics cost drivers have been identified, areas to reduce LCOE impact are suggested: increasing weather limits to reduce waiting on weather costs, minimizing work offshore, improving processes, using economy of scale and optimizing vessel use.
Abstract: Background: During the whole life cycle of an offshore wind farm, from cradle to grave, logistics is needed. Particularly during wind turbine construction, vessels are intensively used. However, no study has been found to evaluate logistics costs during this particular turbine construction phase. Objective: In order to close this gap, this paper ai...
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The Effect of Groundwater Seepage on Stability of Tunnel by Using Strength Reduction Method Considering Fluid Solid Coupling
Zhaobing Zhang,
Xiaoguang Jin,
Yayong Li,
Zhongya Zhang
Issue:
Volume 4, Issue 4, December 2018
Pages:
75-82
Received:
2 December 2018
Accepted:
25 December 2018
Published:
22 January 2019
DOI:
10.11648/j.ijtet.20180404.12
Downloads:
Views:
Abstract: During the construction period of tunnels, groundwater seepage may lead to large deformation and even collapse of tunnel. To study the effect of groundwater seepage on stability of tunnel, the strength reduction method considering fluid solid coupling was employed to calculate safety factor of tunnel by using numerical simulation. Firstly, three working cases were established to investigate the effect of groundwater seepage and calculation mode on safety factor of tunnel. Then the fluid solid indirect coupling mode was adopted to investigate the relationship between safety factor and groundwater level. Numerical results show that safety factor considering groundwater seepage is about 20% less than that without considering groundwater seepage. Numerical results of two calculation modes are almost identical, but the computational time of fluid solid indirect coupling mode is far less compared with that of fluid solid coupling mode. Safety factor of tunnel linearly decreases with the increase of groundwater level, with the slope of 0.26. Moreover, tunnel crown settlement increases with the increase of groundwater level when the strength reduction factor is equal. Groundwater seepage is unfavorable to control tunnel deformation. In the watery zone, groundwater level should be lowered to improve stability of tunnel on condition that it does not seriously affect surrounding environment.
Abstract: During the construction period of tunnels, groundwater seepage may lead to large deformation and even collapse of tunnel. To study the effect of groundwater seepage on stability of tunnel, the strength reduction method considering fluid solid coupling was employed to calculate safety factor of tunnel by using numerical simulation. Firstly, three wo...
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