• Energy Research
• Closed Access close
• Open Source close
• Embargo close
• IN close
• JP close
• AU close

Abstract Gold nanoparticles (Au-NPs) seeded plasmonic nanofluids (PNFs) have shown promising results in overall performance enhancement of direct absorption solar collector (DASC) due to localized surface plasmon resonance (LSPR) effect. For the work presented here, Au-NPs were synthesized by the wet chemical method and were utilized to prepare plasmonic nanofluid. The surface plasmon resonance peak of Au-NPs was observed at 531 nm using UV–Visible spectrophotometer study. The testing for performance enhancement of gold plasmonic nanofluid (GPNF) laden DASC so far is limited to laboratory scale setups or simulation studies. Considering the dearth of outdoor experimental studies, an attempt has been made in the present study to evaluate the thermal performance of Au-NPs (∼40 nm) based nanofluid (∼0.0002 wt%) in full scale DASC. The experiments have been performed at different flow rates under clear sky outdoor conditions in winter season at Jalandhar, India. The maximum collector outlet temperature was measured to be 55 °C with GPNF which is about 7 °C higher than the maximum outlet temperature obtained with de-ionized water as working fluid. Thermal efficiency with GPNF is about 33% higher than de-ionized water at the optimal flow rate of 0.030 kg/s.

Abstract DC microgrids have received wide interest in recent times because of the advantages related to improved power transfer capability, high efficiency, compatibility with distributed energy resources (DER) and reduced losses. However, the adoption of DC microgrids has been restricted because of the challenges in designing a reliable protection scheme. The challenge results from the high magnitude of the fault current without zero crossing, coupled with the requirement of high rapidity in fault detection. The scenario is further complicated during the variation in operational dynamics of microgrid either due to weather intermittency or network reconfiguration arising out of DER outage. Non-addressal of the above issues results in reduced grid resilience because of possible relay malfunction during stressed scenarios. In this regard, an ensemble classifier-based protection scheme has been proposed for DC microgrid with adaptability to system reconfiguration and weather intermittency. The adaptiveness has been achieved by online identification of network topology, while immunity to weather variation is attained by stochastic modelling of solar irradiance and wind speed. The use of local information for executing the protection tasks avoids the issues related to data loss and latency in the communication link. The task of operating mode detection, topology identification, fault detection/classification and section identification have been formulated as a set of classification problems and further solved using a random subspace sampling-based ensemble classifier technique. The reliability of the proposed scheme has been extensively validated for a wide range of fault scenarios involving wide variation in network topology, weather condition and fault parameters.

Abstract Designing a high-performance hydrofoil is a fundamental challenge for the current turbine blade designers. In this paper, the performance of S1210 hydrofoil, commonly used in the tidal current turbine blades, in presence of (i) Vortex Generators (VGs), and (ii) modified trailing edge is numerically studied. The results show that attaching counter-rotating VGs near the trailing edge of the foil can increase the lift coefficient by 17% and delay the stall angle from 10° to 12°. Constructing a rounded and thicker trailing edge can help to improve the hydrodynamic performance by increasing the lift coefficient by 13.5%. The combination of VGs (located near the trailing edge) and rounded trailing edge can increase the glide ratio significantly. These observations have been explained by plotting the pressure coefficients and velocity profiles at different locations on the foil surface. The findings will be useful to manufacture a stronger blade profile and extract more power from the current turbines that operate at wide current speed variation.

Longitudinal flow through central subchannel structures in an array of fuel rods in a nuclear reactor plays an important role in removing the heat generated inside the fuel rods. In this paper, an entropy generation analysis has been carried out for assessment of the performance of an infinite triangular as well as a square subchannel for single-phase forced turbulent flow. The performance is evaluated with the objective function being the overall entropy generation in a central subchannel. Various constraints such as dimensionless flow area subtended by the array of rods, pitch to diameter ratio for the configuration of rod bundles and volumetric heat generation to power density ratio of the subchannel imposed by power restrictions have been considered. The parameters include the dimensionless wall heat flux, duty parameter, length to diameter ratio for fuel rods, Reynolds number etc. It has been observed that for a pitch to diameter ratio constraint the square subchannel generates lesser amount of entropy and thus more acceptable compared to triangular structure. For the same constraint the optimum Reynolds number shifts towards higher value compared to triangular one. For dimensionless flow area constraint, on the other hand, the analysis reveals completely reverse phenomenon.

Abstract Methane dry reforming with CO2 using FeO powder in molten salt has been investigated at various flow rates of CH4/CO2 mixed gases (CH4/CO2=1) between 50 and 400 ml/min at 1223 K in an infrared furnace. This work is carried out to determine the usefulness of this method for the chemical storage of solar energy. The CH4/CO2 mixed gases passing through the molten salt (Na2CO3/K2CO3=1) containing the FeO powder were catalytically decomposed into CO, H2 and H2O. The product gas mole ratios, CO/H2/H2O, were shown to be 3:1:1 for a high flow rate of 200 ml/min and to be CO/H2=2:1 for a low flow rate of 50 ml/min. The results were explained in terms of the kinetics of the CH4-reforming reaction and the thermodynamics of the redox process of FeO powder mixed in the molten salt; CH 4 +2FeO⇒2Fe+H 2 +CO+H 2 O Fe+CO 2 ⇒FeO+CO for a high flow rate, and FeO+CH 4 ⇒Fe+2H 2 +CO Fe+CO 2 ⇒FeO+CO for a low flow rate.

Abstract Thermal energy storage systems based on Phase change materials (PCM) are an attractive option to bridge the temporal and spatial gap between the energy demand and supply. But, these systems possess poor thermal conductivity causing reduced rate of heat transfer. The objective of the present study is to numerically analyze the melting process in an optimized finned latent heat storage system dispersed with varying volume fraction of Graphene nano plates (GNP). The individual effect of incorporating fins, GNP and a combination of both at different volume fraction has been studied. Effective thermal conductivity of nano-composite PCM has been theoretically evaluated including the effect of aspect ratio, interfacial thermal resistance, anisotropy, non-linear effects as well as concentration for the dispersed GNP. In this work, Dynamic differential scanning calorimetry tests are performed to evaluate the phase change temperature, latent heat and specific heat of the sugar alcohol (d- mannitol). Transient variation of liquid fraction, average temperature and radial/longitudinal temperature differentials are presented which would be useful for designing medium temperature (160–200 °C) storage systems for various applications. Fin height is varied to obtain an optimum fin size such that natural convection currents are not impeded. Various heat transfer models (including natural convection) are analysed using the actual plant data of a double effect solar absorption system at different arrangements of fins and GNP. Effect of Reynolds number and inlet temperature of HTF on the system performance have also been studied. A reduction of 68% in total melting time is observed in finned LHSS with 5% GNP as compared to a conventional system.

The Nigerian government is committed to sustaining rice production to meet national demand. Nevertheless, political tension and climate-induced stressors remain crucial constraints in achieving policy targets. This study examines whether climate change and political instability significantly threaten rice production in Nigeria. First, we employed nonparametric methods to estimate the country's rainfall and temperature trends between 1980Q1 and 2015Q4. Second, we employed the autoregressive distributed lag (ARDL) technique to examine the effects of climate change and political instability on rice production. The results show that while temperature has an increasing pattern, rainfall exhibits no significant trend. The findings from the ARDL estimate reveal that rice production responds negatively to temperature changes but is less sensitive to changes in rainfall. In addition, political instability adversely affects rice production in Nigeria. We argue that Nigeria's slow growth in rice production can be traced back to the impact of climate change and political tension in rice farming areas. As a result, reducing the overall degree of conflict to ensure political stability is critical to boosting the country's self-sufficiency in rice production. We also recommend that farmers be supported and trained to adopt improved rice varieties less prone to extreme climate events while supporting them with irrigation facilities to facilitate rice production.

Abstract The 2013/2017 Nankai Trough (Japan) and 2017 Shenhu Area (China) offshore methane hydrate production tests showed the world the possibility and feasibility of the oceanic methane hydrate production by depressurization. However, the relatively low gas production rate still remained as one of the critical bottlenecks for the economical utilization. This study chose the Nankai Trough as a target area, and aimed at the gas recovery enhancement from the methane hydrate reservoir using vertical wells. A traditional single-vertical-well system and a new dual-vertical-well system were proposed, and special production strategies of the aggressive depressurization and permeability improvement were applied to these two systems for the effectiveness verification. Based on the 15-year simulation results, it was found that the middle low-permeability silt-dominated layers in the reservoir held the key to the gas recovery enhancement, and for the single-vertical-well system, the permeability improvement in this sublayer seemed more reliable and feasible than the aggressive depressurization. On the other hand, the dual-vertical-well system significantly exceeded the single-vertical-well system due to the synergistic effect of the two wellbores, and could raise the average gas production rate (9.5 × 103 m3/day) by one order of magnitude (to 7.9 × 104 m3/day). Moreover, if this new system was combined with the aggressive depressurization, the average gas production rate could be further raised by one order of magnitude (to 3.4 × 105 m3/day).