Hydrodynamic performance of a dual-floater hybrid system combining a floating breakwater and an oscillating-buoy type wave energy converter

The high cost of power generation impedes commercial-scale wave power operations. The objective of this work is to provide a cost-sharing solution by combining wave energy extraction and coastal protection. A two-dimensional numerical wave tank was developed using Star-CCM+ Computational Fluid Dynamics software to investigate the hydrodynamic performance of a dual-floater hybrid system consisting of a floating breakwater and an oscillating-buoy type wave energy converter (WEC), and was compared with published experimental results. The differences between the hydrodynamic performance of the hybrid system, a single WEC and a single breakwater were compared. Wave resonance in the WEC-breakwater gap has a significant impact on system performance, with the hybrid system demonstrating both better wave attenuation and wave energy extraction capabilities at low wave frequencies, i.e., wider effective frequency. Forces on the breakwater were generally reduced due to the WEC. Wave resonance in the narrow gap has an adverse effect on the energy efficiency of the hybrid system with an asymmetric WEC, while a beneficial effect with a symmetric WEC. The wave energy conversion efficiency of hybrid system can be improved by increasing the draft and width of the WEC and decreasing the distance between the WEC and the breakwater. The findings of this paper make wave energy economically competitive and commercial-scale wave power operations possible

Hydrodynamic performance of a dual-floater hybrid system combining a floating breakwater and an oscillating-buoy type wave energy converter

The high cost of power generation impedes commercial-scale wave power operations. The objective of this work is to provide a cost-sharing solution by combining wave energy extraction and coastal protection. A two-dimensional numerical wave tank was developed using Star-CCM+ Computational Fluid Dynamics software to investigate the hydrodynamic performance of a dual-floater hybrid system consisting of a floating breakwater and an oscillating-buoy type wave energy converter (WEC), and was compared with published experimental results. The differences between the hydrodynamic performance of the hybrid system, a single WEC and a single breakwater were compared. Wave resonance in the WEC-breakwater gap has a significant impact on system performance, with the hybrid system demonstrating both better wave attenuation and wave energy extraction capabilities at low wave frequencies, i.e., wider effective frequency. Forces on the breakwater were generally reduced due to the WEC. Wave resonance in the narrow gap has an adverse effect on the energy efficiency of the hybrid system with an asymmetric WEC, while a beneficial effect with a symmetric WEC. The wave energy conversion efficiency of hybrid system can be improved by increasing the draft and width of the WEC and decreasing the distance between the WEC and the breakwater. The findings of this paper make wave energy economically competitive and commercial-scale wave power operations possible

Hydrodynamic performance of a floating breakwater as an oscillating-buoy type wave energy converter

Combined floating breakwater and wave energy converter systems have the potential to provide a cost-effective solution to offshore power supply and coastal protection. This will make wave energy economically competitive and commercial-scale wave power operations possible. This paper investigates the hydrodynamic features of wave energy converters that meet the dual objectives of wave energy extraction and attenuation for such a combined system. A two-dimensional numerical model was established using Star-CCM+ commercial software based on viscous Computational Fluid Dynamics theory to investigate the hydrodynamic performance of an oscillating buoy Wave Energy Converter (WEC) type floating breakwater under regular waves. The model proposed in this paper was verified with published experimental results. The hydrodynamics of symmetric and asymmetric floaters were investigated to demonstrate their wave attenuation and energy extraction performance, including square bottomed, triangular bottomed (with and without a baffle plate), and the Berkley Wedge. The asymmetric floaters were found to have higher power conversion efficiency and better wave attenuation performance, especially the Berkeley Wedge bottom device and the triangular-baffle bottom device. The triangular-baffle bottom device with a simpler geometry achieved similar wave attenuation and energy extraction performance characteristics to that of the Berkeley Wedge device. The maximum energy conversion efficiency of the triangular-baffle bottom floater reached up to 93%, an impressive WEC device among many designs for wave energy conversion. There may be a great potential for this newly proposed triangular-baffle bottom WEC type of floater to be an ideal coastal structure for both coastal protection and wave energy extraction

Ethanol and nicotine interaction within the posterior ventral tegmental area in male and female alcohol-preferring rats: evidence of synergy and differential gene activation in the nucleus accumbens shell

RATIONALE: Ethanol and nicotine are frequently co-abused. The biological basis for the high co-morbidity rate is not known. Alcohol-preferring (P) rats will self-administer EtOH or nicotine directly into the posterior ventral tegmental area (pVTA). OBJECTIVE: The current experiments examined whether sub-threshold concentrations of EtOH and nicotine would support the development of self-administration behaviors if the drugs were combined. METHODS: Rats were implanted with a guide cannula aimed at the pVTA. Rats were randomly assigned to groups that self-administered sub-threshold concentrations of EtOH (50 mg%) or nicotine (1 μM) or combinations of ethanol (25 or 50 mg%) and nicotine (0.5 or 1.0 μM). Alterations in gene expression downstream projections areas (nucleus accumbens shell, AcbSh) were assessed following a single, acute exposure to EtOH (50 mg%), nicotine (1 μM), or ethanol and nicotine (50 mg% + 1 μM) directly into the pVTA. RESULTS: The results indicated that P rats would co-administer EtOH and nicotine directly into the pVTA at concentrations that did not support individual self-administration. EtOH and nicotine directly administered into the pVTA resulted in alterations in gene expression in the AcbSh (50.8-fold increase in brain-derived neurotrophic factor (BDNF), 2.4-fold decrease in glial cell line-derived neurotrophic factor (GDNF), 10.3-fold increase in vesicular glutamate transporter 1 (Vglut1)) that were not observed following microinjections of equivalent concentrations/doses of ethanol or nicotine. CONCLUSION: The data indicate that ethanol and nicotine act synergistically to produce reinforcement and alter gene expression within the mesolimbic dopamine system. The high rate of co-morbidity of alcoholism and nicotine dependence could be the result of the interactions of EtOH and nicotine within the mesolimbic dopamine system

Solvent Optimization Studies for a New EURO-GANEX Process with 2,2’-Oxybis( N,N -di- n -decylpropanamide) (mTDDGA) and Its Radiolysis Products

The diglycolamide 2,2’-oxybis(N,N-di-n-decylpropanamide) (mTDDGA) is being studied as an extractant for actinides and lanthanides in the European Grouped Actinide Extraction (EURO-GANEX) process. The aim is the development of a more simplified process using a single extractant instead of a mixture of extractants used in the current EURO-GANEX process. This work presents solvent optimization studies of mTDDGA, with regards to the extraction characteristics of the different diastereomers of mTDGA and of mixed diastereomer solutions. Also radiolysis behavior has been studied by irradiation of solvent extraction systems in a gamma irradiation facility using $^{60}$Co. The availability of irradiated organic solutions made it possible to gain valuable insights into the plutonium loading capacity after gamma-irradiation of the solvent up to 445 kGy and to quantify degradation compounds. Solvent extraction characteristic of the major degradation compounds themselves were determined. Like other methylated diglycolamides, we found a remarkable difference in extraction of up to two orders of magnitude between the two diastereomers. High plutonium loading (36 g L$^{−1}$) is feasible using this single extractant, even after absorbing a dose of 445 kGy. This remarkable observation is possibly promoted by the presence of the main degradation compound which extracts plutonium verywell

Gamma-radiolytic stability of new methylated TODGA derivatives for minor actinide recycling

The stability against gamma radiation of MeTODGA (methyl tetraoctyldiglycolamide) and Me2TODGA (dimethyl tetraoctyldiglycolamide), derivatives from the well-known extractant TODGA (N,N,N′,N′-tetraoctyldiglycolamide), were studied and compared. Solutions of MeTODGA and Me2TODGA in alkane diluents were subjected to 60Co γ-irradiation in the presence and absence of nitric acid and analyzed using LC-MS to determine their rates of radiolytic concentration decrease, as well as to identify radiolysis products. The results of product identification from three different laboratories are compared and found to be in good agreement. The diglycolamide (DGA) concentrations decreased exponentially with increasing absorbed dose. The MeTODGA degradation rate constants (dose constants) were uninfluenced by the presence of nitric acid, but the acid increased the rate of degradation for Me2TODGA. The degradation products formed by irradiation are also initially produced in greater amounts in acid-contacted solution, but products may also be degraded by continued radiolysis. The identified radiolysis products suggest that the weakest bonds are those in the diglycolamide center of these molecules