Wind energy is a promising alternate energy resource. However, the on-land wind farms are limited by space, noise, and visual pollution and, therefore, many countries build wind farms near the shore. Until now, most offshore wind farms have been built in relatively shallow water (less than 30 m) with fixed tower type wind turbines. Recently, several countries have planned to move wind farms to deep water offshore locations to find stronger and steadier wind fields as compared to near shore locations. For the wind farms in deeper water, floating platforms have been proposed to support the wind turbine. The model tests described in this paper were peiformed at MARIN (maritime research institute netherlands) with a model setup corresponding to a 1:50 Froude scaling. The wind turbine was a scaled model of the national renewable energy lab (NREL) 5 MW horizontal axis reference wind turbine supported by three different generic floating platforms: a spar, a semisubmersible, and a tension-leg platform (TLF). The wave environment used in the tests is representative of the offshore in the state of Maine. In order to capture coupling between the floating platform and the wind turbine, the 1st bending mode of the turbine tower was also modeled. The main purpose of the model tests was to generate data on coupled motions and loads betvi'een the three floating platforms and the same wind turbine for the operational, design, and survival seas states. The data are to be used for the calibration and improvement of the existing design analysis and performance numerical codes. An additional objective of the model tests was to establish the advantages and disadvantages among the three floating platform concepts on the basis of the test data. The paper gives details of the scaled model wind turbine and floating platforms, the setup configurations, and the instrumentation to measure motions, accelerations, and loads along with the wind turbine rpni, torque, and thrust for the three floating wind turbines. The data and data analysis results are discussed in the work of
Beyond many of Earth's coasts exists a vast deepwater wind resource that can be tapped to provide substantial amounts of clean, renewable energy. However, much of this resource resides in waters deeper than 60 m where current flxed bottom wind turbine technology is no longer economically viable. As a result, many are looking to floating wind turbines as a means of harnessing this deepwater offshore wind resource. The preferred floating platform technology for this application, however, is currently up for debate. To begin the process of assessing the unique behavior of various platform concepts for floating wind turbines, 1150th scale model tests in a wind/wave basin were performed at the Maritime Research Institute Netherlands (MARIN) of three floating wind turbine concepts. The Froude scaled tests simulated the response of the 126 m rotor diameter National Renewable Energy Lab (NREL) 5MW, horizontal axis Reference Wind Turbine attached via a flexible tower in turn to three distinct platforms, these being a tension leg-platform, a spar-buoy, and a semisubmersible. A large number of tests were performed ranging from simple free-decay tests to complex operating conditions with irregular sea states and dynamic winds. The high-quality wind environments, unique to these tests, were realized in the offshore basin via a novel wind machine, which exhibited low swirl and turbulence intensity in the flow field. Recorded data fi-om the floating wind turbine models include rotor torque and position, tower top and base forces and moments, mooring line tensions, six-axis platform motions, and accelerations at key locations on the nacelle, tower, and platform. A comprehensive overview of the test program, including basic system identification results, is covered in previously published works. In this paper, the results of a comprehensive data analysis are presented, which illuminate the unique coupled system behavior of the three floating wind turbines subjected to combined wind and wave environments. The relative performance of each of the three systems is discussed with an emphasis placed on global motions, flexible tower dynamics, and mooring system response. The results demonstrate the unique advantages and disadvantages of each floating wind turbine platform. Journal of Offshore Mechanics and Arctic Engineering
In this study, seven organic amendments (biosolid compost, farm yard manure, fish manure, horse manure, spent mushroom, pig manure, and poultry manure) were investigated for their effects on the reduction of hexavalent chromium [chromate, Cr(VI)] in a mineral soil (Manawatu sandy soil) low in organic matter content. Addition of organic amendments enhanced the rate of reduction of Cr(VI) to Cr(III) in the soil. At the same level of total organic carbon addition, there was a significant difference in the extent of Cr(VI) reduction among the soils treated with organic amendments. There was, however, a significant positive linear relationship between the extent of Cr(VI) reduction and the amount of dissolved organic carbon in the soil. The effect of biosolid compost on the uptake of Cr(VI) from the soil, treated with various levels of Cr(VI) (0-1200 mg Cr kg(-1) soil), was examined with mustard (Brassica juncea L.) plants. Increasing addition of Cr(VI) increased Cr concentration in plants, resulting in decreased plant growth (i.e., phytotoxicity). Addition of the biosolid compost was effective in reducing the phytotoxicity of Cr(VI). The redistribution of Cr(VI) in various soil components was evaluated by a sequential fractionation scheme. In the unamended soil, the concentration of Cr was higher in the organic-bound, oxide-bound, and residual fractions than in the soluble and exchangeable fractions. Addition of organic amendments also decreased the concentration of the soluble and exchangeable fractions but especially increased the organic-bound fraction in soil.
While Cr(III) is strongly retained onto soil particles, Cr(VI) is very weakly adsorbed and is readily available In this study, seven organic amendments (biosolid compost, farm yard manure, fish manure, horse manure, spent mushroom, pig ma-for plant uptake and leaching to ground water (James nure, and poultry manure) were investigated for their effects on the and Bartlett, 1983). Leaching studies have indicated that reduction of hexavalent chromium [chromate, Cr(VI)] in a mineral Cr(VI) is readily leached compared with Cr(III) and soil (Manawatu sandy soil) low in organic matter content. Addition anions, such as arsenate (Carey et al., 1996; Bolan and of organic amendments enhanced the rate of reduction of Cr(VI) to Thiyagarajan, 2001). Chromium(VI) can be reduced to Cr(III) in the soil. At the same level of total organic carbon addition, Cr(III) in the environments where a ready source of there was a significant difference in the extent of Cr(VI) reduction electrons is available. Suitable conditions for Cr(VI) among the soils treated with organic amendments. There was, however, a significant positive linear relationship between the extent of reduction occur where organic matter is present to act Cr(VI) reduction and the amount of dissolved organic carbon in the as an electron donor, and Cr(VI) reduction is enhanced soil. The effect of biosolid compost on the uptake of Cr(VI) from the in acid rather than alkaline soils (Bartlett and Kimble soil, treated with various levels of Cr(VI) (0-1200 mg Cr kg Ϫ1 soil), 1976; Cary et al., 1977). Reduction of Cr(VI) to Cr(III), was examined with mustard (Brassica juncea L.) plants. Increasing and subsequent hydroxide precipitation of Cr(III) ion, addition of Cr(VI) increased Cr concentration in plants, resulting in is the most common method of treating Cr(VI)-contamidecreased plant growth (i.e., phytotoxicity). Addition of the biosolid nated industrial effluents (Besseliever, 1969). Various compost was effective in reducing the phytotoxicity of Cr(VI). The redistribution of Cr(VI) in various soil components was evaluated organic materials, such as powdered leaves (Suseela et by a sequential fractionation scheme. In the unamended soil, the al., 1987) and Scotch pine (Pinus sylvestris L.) bark concentration of Cr was higher in the organic-bound, oxide-bound, (Alves et al., 1993) have been used to remove Cr(VI) and residual fractions than in the soluble and exchangeable fractions.from industrial effluents. Addition of organic amendments also decreased the concentration of
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