Due to its simplicity and low cost, the Wells turbine is the most common choice for driving oscillating-water-column (OWC) wave energy converters (WECs) power take-off system. This turbine is ...characterized by a flow rate that is a linear function of the pressure head and inversely proportional to the rotational speed before the onset of hard stall conditions. The Wells turbine has been simulated in wave tanks using porous plugs, where the flow rate exhibits linear behaviour. However, numerical and experimental results have shown that rotational speed variations significantly influence the performance of OWC WECs. This work aims to develop a novel real-time simulator of a Wells turbine for use in physical models of OWC power plants. The proposed simulator consists of a diaphragm whose diameter is adjusted in real-time as a function of the pressure head measured in the laboratory and the rotational speed calculated by a hardware-in-the-loop model. In this way, it is possible to reproduce the full behaviour of the Wells turbine before and after a hard stall. Experimental results demonstrate the effectiveness of the simulator. A performance analysis was conducted to understand the device’s potential and compare the damping that Wells and impulse turbines introduce.
•Air turbine real-time simulator for OWC wave plant physical modelling.•Hardware-in-the-loop experimental modelling of air turbines.•Physical modelling of Wells turbine dynamics including stall conditions.•Wave tank modelling of Wells and impulse turbines.
Environmental reasons and circular economy opportunities have increased the interest in brine concentration technologies. The high thermal efficiency of vacuum-assisted air gap membrane distillation ...(V-AGMD) performed in multi-envelope modules with high residence time suggests that it could be a competitive technology for brine concentration. However, most of the studies so far are for seawater feeds, and the effect of feed salinity in the performance of V-AGMD at pilot scale has not been yet thoroughly assessed. This paper presents the first statistical model of the performance of a spiral-wound V-AGMD module in which feed salinity is included as a variable. Permeate flux and thermal efficiency are estimated as a function of evaporation and cooling inlet temperatures, feed flow rate and salinity. Accurate model equations have been developed and validated using experimental results obtained in a pilot-scale plant at the solar MD facilities of CIEMAT-PSA. This is the first assessment of pilot-scale MD which shows that from concentrations above 105.2 g L−1, the maximum thermal efficiency is obtained by increasing the feed flow rate, unlike at lower salinities. Moreover, for salinities above 140.3 g L−1 some operating conditions are not conducive to permeate production.
•Performance model of V-AGMD at pilot scale including feed salinity as a variable.•Reduction of performance with feed salinity stronger than in lab-scale.•Increasing feed flow rate required for optimal performance at high salinity.•Operating conditions identified for which no permeate obtained at high salinity.
•Performance models of pilot V-AGMD modules published for the first time.•Feed flow rate crucial for the performance of pilot V-AGMD.•Predictions of STEC improved by modelling direct temperature ...measurements.•Optimization of performance including costs for an MD facility.•Thermal energy cost influences critically LCOW and dimensioning of the facility.
Membrane distillation using multi-envelope modules in vacuum enhanced air gap (V-AGMD) operation has been demonstrated as the best alternative to the current thermal desalination technologies. This work presents for the first time the use of response surface methodology (RSM) to model and validate the performance of V–AGMD operation for seawater desalination in three multi-envelope modules with different internal designs. Permeate productivity (PFlux) and condenser outlet temperature (TCO) were modelled and validated from results obtained in steady-state experiments, considering the evaporator inlet temperature, the condenser inlet temperature, and the feed flow rate as inputs. To gain accuracy in the estimations of thermal efficiency regarding previous works, a novel strategy was applied, consisting in calculating the specific thermal energy consumption (STEC) using the models of PFlux and TCO, developed from direct measurements. The models of the three modules were used to search the optimal operating conditions that minimize the levelized cost of water (LCOW) in a large-scale MD plant under different scenarios. Different costs of thermal and electrical energy were considered and their influence on the number of modules required in the facility was also discussed.
Ocean wave energy continues to develop through innovation and a growing number of collaborations around the world. With the vast resource of wave energy on our doorstep it remains a focal point in ...ocean energy engineering with great potential. In order for wave energy to become more competitive and a serious player in the renewable energy mix, such innovations should not only benefit the wave energy sector but also other technological applications by providing attractive options for synergies in novel projects. This paper concerns the experimental investigation of Oscillating Water Column (OWC) Wave Energy Converter (WEC) technology and its potential as a Multi-Oscillating Water Column (M-OWC). This research investigation utilises a progressive and pragmatic experimental modelling approach, by cross comparing the models of a single standalone OWC, an OWC array and finally a modular M-OWC under the same environment and test conditions. Performance and characteristic responses are analysed while varying the values of OWC spacing, damping and wave conditions. The results indicate that the spacing of OWC chambers significantly affects the performance of an M-OWC. While performance improves with the increase of spacing, the efficiency of the M-OWC is greater than that of a single OWC or the OWC array at reduced spacing values. In addition, the results indicate that an OWC array is less efficient by having individual power take-off systems operating in isolation as opposed to the modular M-OWC.
•Terminating configuration of OWC chambers spacing significantly affects performance.•OWC array model performs poorly with the individual isolated PTOs.•Flow and power values generated by M-OWC superior to three singular OWC equivalent.•At low spacing, the M-OWC is superior with respect to overall effective CWR.•At suboptimal spacing the M-OWC has higher total CWR to the singular OWC and array.
In this paper, the self-propelled characteristics of the benchmark ONRT hull were studied experimentally at both Froude numbers, Fr = 0.20 and Fr = 0.30. The assessments were conducted under ...free-running conditions using a fully appended Office of Naval Research Tumblehome (ONRT), model 5613, scaled at 48.9, a customary proportion in academic research. To demonstrate the reliability of self-propulsion experiments conducted at the Istanbul Technical University, Ata Nutku Ship Model Testing Laboratory (ITU-AN), an uncertainty analysis method was applied to the ONRT results. The self-propulsion points from the studies in literature at both Fr = 0.20 and Fr = 0.30, were compared with the present test results. Based on the analysis results at self-propulsion points, it was noted that there was a high level of both intra-laboratory repeatability and inter-laboratory reproducibility characteristics. Through repeated tests, it was discerned that the uncertainties impacting essential parameters were, in descending magnitude, thrust, torque, and rotational rate. Consequently, this investigation enhances the precision and reliability of results by presenting the thrust and torque characteristics of the ONRT hull form, along with associated uncertainties for these Fr numbers.
•This study evaluates ITU-AN's self-propulsion experiment uncertainties, revealing ONRT hull propulsion factors.•The propeller rotation rates at Froude numbers of 0.20 and 0.30 were determined to be 9.007 rps and 14.103 rps, respectively.•As a result of repeated tests (N = 15), uncertainties of thrust and torque values are presented at a 95% confidence level.•In the repeatability analysis of the tests, uncertainties were found to be greater in thrust force than in torque values.•The reproducibility of self-propulsion tests was found to be high by an interlaboratory comparison.
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•For the first time, nine natural deep eutectic solvents were investigated for indigo carmine extraction.•New approach was presented for fast, simple and accurate determination of ...indigo carmine.•Central composite design with desirability function was used for experimental modeling and optimization.•Satisfactory repeatability, high enrichment, low LOD and wide linearity were obtained.
This study report optimization of vortex-assisted natural deep eutectic solvent based liquid-phase microextraction (VA-NADES-LPME) for determination of indigo-carmine in some food samples by UV–Visible spectrophotometer. To ensure efficient extraction, nine different NADES were prepared and tested for the extraction of indigo-carmine. In order to increase extraction efficiency of indigo-carmine, the effects of VA-NADES-LPME variables and their interactions were optimized with central composite design. The optimized method exhibited a linear range between 10 and 900 ng mL−1. Limit of detection, limit of quantification and enrichment factor were determined as 3.3 ng mL−1, 10 ng mL−1 and 135-fold, respectively. The applicability of the optimized method was investigated in selected food samples using the matrix-matching calibration curve. Using optimised experimental conditions (pH of 3.2, 75 µL of NADES-4, 285 µL of THF, and 4 min vortexing), satisfactory recovery results were found in the range of 95.9–104.2% with 1.4–3.7% of relative standard deviation. Finally, the optimized method was economical, simple, green, requires less laborious sampling, and provides superior accuracy and precision in trace-level analysis.
Experimental modelling applied to the study of orogenic wedge dynamics has been a subject of fruitful research for more than 30years, although the technique dates back as far as the early XIXth ...century. On one hand, several first order parameters controlling the structural evolution of mountain belts have been intensively investigated using the classic tectonic “sandbox” models. The main parameters are the properties of the basal décollement, the deforming material, the backstop, and fluxes, kinematics and surface processes. On the other hand, the morphological evolution of a mountain relief subjected to changing tectonic or climatic forcing has been addressed using another kind of approach called “geomorphic” models. Nowadays, the literature is extremely rich, particularly for the sandbox technique, so that it becomes difficult to have an exhaustive view of the effects of the above parameters on mountain evolution. In this article, we propose a detailed review of the main results obtained using both “tectonic” and “geomorphic” approaches. Our goal is to provide an almost complete state-of-the-art in the experimental study of relief dynamics to guide present and future researchers in their understanding of mountain belt evolution.
► Experimental modelling approaches have provided insights on our understanding of the dynamical evolution of mountain belts. ► Several first order and interdependent parameters control the evolution of accretionary wedges. ► The influence of each parameter is reviewed to help and guide researchers in their understanding of mountain belt evolution.
This paper aims at developing a mooring methodology for floating point absorber arrays. To date, the literature gives no clear indications of the mooring influence on the potential energy conversion ...of a floating wave energy converter. Hence, this study targets to provide general insights into the dynamics of a floating wave energy converter under the influence of moorings. These are gained by conducting an experimental study on the motion response of a wave energy converter array in regular wave conditions using three different mooring systems: a taut line mooring, a vertical tension leg mooring, and a conventional slack catenary mooring. Results show that the potential energy conversion is strongly influenced by the choice of the mooring system and the incident wavelength. In intermediate wavelengths, a taut mooring system leads to a 8% increase in energy conversion potential. In contrast, the tension-leg moored array exceeds the potentially converted energy of the catenary moored array in wavelengths significantly longer than the wave energy converter’s length by over 80%. The results of this study provide an insight into the site-specific design of point absorber arrays and the best choice of the mooring system to increase the potential power output.
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•A modular frame-connected point absorber array is investigated experimentally.•WEC length affects its motion characteristics and should be adapted to wave climate.•Performance of WEC decreases strongly with increasing wavelength.•Taut mooring system is recommended over catenary and vertical tension leg systems.•Vertical tension leg system shows best performance in waves longer than the WEC.
Vortex flow characteristics in a reservoir and horizontal water intake have been predicted by using regression models in this numerical research. In this paper, three standalone machine learning ...models – Random Forest (RF), K-nearest neighbours (KNN), Gradient Boosting (GB) – and a proposed hybrid model based on Lévy Jaya Algorithm (LJA) and GB (LJA-GB) are employed to estimate the effect of trash racks on flow properties at power intakes. The experimental data which are prepared for the proposed study in this paper were obtained through a rectangular laboratory tank 8.3 m3 with various submergence depths and Froude numbers on nine trash racks with 63.7%–84.1% opening, made out of 2, 2.5, 4, and 6 mm thick copper wire. The outcomes revealed that the proposed LJA-GB model shows the best overall performance among the four models used for estimation. Thus, the LJA-GB model has the lowest mean absolute error (MAE) (0.3344), mean squared error (MSE) (0.1784), and root mean squared error (RMSE) (0.4223) values and highest R-squared (Formula: see text) (0.9899) and Willmott’s index (WI) values (0.9508) in the testing stage metrics for Formula: see text estimation and MAE (0.0061), MSE (0.0001), RMSE (0.0073), Formula: see text (0.9971), WI (0.9727) for Formula: see text estimation. Whereas the RF and KNN models exhibited poor performance in both stages of estimation.
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