International Journal of Energy and Environmental Engineering

Abstract The identification of offshore wind farms necessitates the consideration of multiple factors, including technical, social, economic, and ecological ones, amongst others. In the current study, a multi-criterial model is applied by incorporating wind speed, water depth, grid proximity, tourism activities, and marine spatial constraint factors to determine optimum sites for offshore wind farm placements in the Republic of Mauritius. The North-Eastern region, off the coast of Grand Gaube, has been found to be promising, with an annual electricity potential of 1650 GWh, owing to favourable wind regime of about 7.95 m/s at 100 m height. Moreover, the site location, at an average water depth of 38 m, favours the adoption of conventional jacket foundation. A levelized cost analysis reveals that the electricity generated from the offshore farm would be priced at $163/MWh, which makes it cost-competitive as compared to heavy fuel oil at $218/MWh. A scenario looking at the installation of a 608 MW offshore wind plant, which represents the theoretical maximum that may be attained in the optimum region identified, revealed that exploitation of this site has the potential to decrease up to 1.5 times the share of imported fuel oil and diesel for electricity needs. Besides providing guidelines for the implementation of offshore wind technology in Mauritius, the paper reflects on important gaps for adoption, including factors that seek to ease policy uptake. Graphical abstract

Abstract Waterflooding is renowned improved oil recovery method worldwide to recover medium to light crude oil. LSWF is an emergent IOR method which reduces the quantity of residual oil saturation by implementing waterfloods of low salt concentration. LSWF can increment the oil recovery up to 10–20% compared to simple waterflooding. A synthetic 3D simulation model is generated in this study using commercial black oil simulator (Eclipse 100). Two base cases of low and high salinity water flooding are simulated, and impact of low salinity water flooding on FOE, FOPR, FOPT, FPR, FSPR, FSPT is analyzed. Sensitivity analyses of injection water salinity, relative permeability curves, grid refinement, Low salinity slug size and end point saturation effects are also conducted (LASLTFNC). LSWF enhances the oil recovery efficiency by 17% compared to HSWF. Sensitivity of wettability (relative permeability curves) exhibits maximum recovery of 75.96% in presence of strongly water wet system. Similarly, sensitivity of grid refinement exhibits variation in ultimate recovery of 5.24% between LSWF base case and refined grid case. Sensitivity of injection water salinity from 1000 to 35,000 PPM (sea water) results in ultimate recovery between 60.88 and 75.96%, respectively. The continuous injection of LS water is not economical for whole production life therefore the injection of slug can help in the withdrawal of almost similar volume of oil with better cost. Economic analysis of five different LSWF cases and one HSWF case is carried out to evaluate the most economically viable injection scenario. From case-1 to case-6, injection of low salinity water for 450 days followed by high saline water turns out to be the most optimum case with NPV of 20.422 million dollars.

Abstract The growth curve is an important characteristic to estimate microalgae biomass production for biofuel generation, since they can measure the variation between concentrations of limiting factors of culture medium. Therefore, this work aimed to evaluate the development of Chlorella vulgaris with triplicate cultivation of three different concentrations of nitrogen and phosphorus (Treatment 1: 0.50 g L−1 Ca(NO3)2·4H2O and 0.13 g L−1 KH2PO4, Treatment 2: 0.50 g L−1 Ca(NO3)2·4H2O and 0.39 g L−1 KH2PO4, Treatment 3: 1.50 g L−1 Ca(NO3)2·4H2O and 0.13 g L−1 KH2PO4,). Growth curve using Gompertz model presented high R2 (0.96 ≤ R2 ≤ 0.99) in the three studied treatments. In the thirteenth day, turbidity in the treatment with higher nitrogen concentration (203.67 NTU) was 2.15 times higher than the first treatment (94.56 NTU) and 1.78 times higher than the treatment with higher level of phosphorus (113.9 NTU). We therefore observed a major biomass production, chlorophylls and carotenoids in the treatment with higher concentration of nitrogen, while in high levels of phosphorus the growth is not statistically significant from the first treatment with lower nitrogen and phosphorus concentration (p value > 0.05). In the end of cultivation, there was an increase of 203.12% in chlorophyll-a in the third treatment compared to the first treatment and of 246.42% in comparison with the second treatment. For carotenoids, the highest increase was seen compared to the first treatment (192%) than for the second treatment (137.5%). Therefore the treatment with lower phosphorous concentration in the cultivation medium presented slightly higher chlorophyll concentration and smaller carotenoids with the treatment with higher phosphorus concentration. The ash content demonstrated that this microalgae have a great potential for energy use.

Abstract In severe wave conditions, the ship propulsion system is loaded with high fluctuations due to external disturbances. The highly fluctuating loads enforce radical changes in the main engine torque, which in turn demands variation of the fuel rate injected into the cylinders if a constant rotational speed strategy is applied. Therefore, the temperature of gases varies to a large extent during the combustion process in the cylinders. The emitted NOx is a function of this highly fluctuating temperature. The main goal of this study is to investigate NOx emission under the aforementioned conditions when a usual constant RPM control strategy is applied in waves similar to the calm water condition. The paper presents a mathematical model of the whole system, which is applied to a selected ship both in regular waves and in calm water conditions. The results show that the sea waves, in comparison with the calm water condition, can radically increase the emitted NOx under the constant rotational speed strategy. This change can reach even 1014 times more, averagely. The results also show that the higher the wave height the higher the emitted NOx. It is concluded that the control strategy of keeping the engine rotational speed in waves at a constant level is the most important reason for the significantly increased NOx emission in waves in comparison with the calm water condition.

Abstract The transport sector produces one-third of the world’s greenhouse gasses. World consumption of nonrenewable energy through vehicles increases the interest in studies of different nanoparticle biodiesel blend behavior in a diesel engine. In this research, a comprehensive approach is taken using a wide variety of appraised nanoparticles to make blends. The CI diesel engine's engine performance and emission characteristics are studied with Malaysian commercial fuel using various nanoparticles (TiO2, Al2O3, CuO, CeO2, CNT, and GNP) blend to discover the best one. 100 ppm of each nanoparticle is used to make a blend via the ultrasonic technique. Mechanical and emission performance is tested in diesel engines (Yanmar TF 120 M) with 100% engine load at variable engine speed (2100-900 rpm). Graphical presentation and comparison of each fuel blend are discussed in this paper. All the ternary blends have shown improved engine performance. Al2O3 has shown a 3.68% reduction in BSFC when compared to neat B10. The average highest BTE recorded is a 14.59% increase when the B10 + TiO2 blend is used, followed by CNT and CeO2. Al2O3 has shown a 21.84% and 86.20% reduction in CO and HC when compared to B10, while CNT and GNP have shown a 6.03% and 2.06% of reduction in NOx emission when compared with B10.