• Energy Research
• Closed Access close
• Restricted close
• Embargo close
• IN close
• Renewable Energy 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 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.

Abstract Enhancing microalgae biomass productivity through different abiotic and environmental factors optimization is crucial. Design of experimental (DOE) methodology using Taguchi orthogonal array (OA) was studied to evaluate the specific influence of eight important factors (light, pH, temperature, carbon concentration, nitrates, phosphates, magnesium ion concentration and carbon source) on the biomass production using three levels of factor (2 1 × 3 7 ) variation with experimental matrix [L 18 -18 experimental trails]. All the factors were assigned with three levels except light illumination (2 1 ). Substantial influence on biomass productivity is observed with carbon concentration contributing 16.8%, followed by nitrates 12.8% and light 9.3%. Experimental setup eight (Light, pH-8.5, Temperature 25°C, Carbon concentration 10 g/l, nitrates 1.5 g/l, phosphates 0 g/l, magnesium 150 mg/l, Carbon source (glucose)) showed maximum biomass growth (5.26 g/l) and good substrate degradation (63%, COD removal efficiency) contributing to carbohydrate production (257 mg/g biomass) which is further converted to lipids (20% Total lipid and 10% Neutral lipids). Chlorophyll ( a , b ), carbohydrates composition, FAME analysis for lipid percentage were monitored during process operation. Elemental analysis reveals that the carbon to hydrogen and oxygen ratio present in dried algal biomass can be hydrothermally liquefied (HTL) to produce biocrude.

Abstract Small hydropower projects (SHPs), though generally considered more environmentally benign and socially acceptable as compared to large projects, yet their overall sustainability is under suspicion in the Himalayan regions. Almost all SHPs in this region are being developed as run of the river mode which generally causes less/no submergence and quite less displacement of people as compared to large reservoir based hydropower production mode. However, in the absence of proper planning and monitoring mechanism, these projects are causing implacable tunnelling of hills, choking of streams, conversion of streams into dry ditches and long term socio-environmental impacts. This paper presents a SHP development study from hydro rich Beas river basin of Himachal Pradesh, a state nestled in western Himalayan region of India. In depth field studies, focus group discussions with the project affected people and interaction with project proponents of five SHPs in this region suggest that sustainability issues with respect to SHPs are not small vis-a-vis size of their installed capacity. There is an urgent need to take steps to include SHPs having an installed capacity of above 10 MW into the ambit of environment clearance process which is absent in many countries of the world at present.

Abstract Pongamia residue (shells) is the byproduct from the biodiesel processing industry, which is a lignocellulosic biomass material. It is not suitable as feedstock in downdraft wood gasifier due to low bulk density (146 kg/m3) of shells as compared to wood (more than 350 kg/m3). Pelletization and gasification of pelletized shells was carried out in the present work. The heat transfer analysis in pellets of 17 mm and 11.5 mm was also carried out to evaluate thermal properties of this biomass. Shell pellets of 17 mm and 11.5 mm diameter and length in the range of 10–60 mm were gasified in a 20 kWe downdraft wood gasifier. The complete gasification of pellets with 17 mm diameter could not be achieved because of less porosity and presence of larger thermal gradient within the pellets. The gasification efficiency was 73% for 17 mm diameter pellets which is lower than that of 11.5 mm diameter pellets which was 95%. The calorific value of producer gas generated from smaller diameter pellets was higher (4.66 MJ/N m3) as compared to larger diameter pellets (3.98 MJ/N m3). Tar formation during gasification of smaller diameter pellets was low as compared to larger diameter pellets.

Abstract In this research, photovoltaic thermal integrated thermoelectric cooler (PVT-TEC) collector has been analyzed, considering three different types of PV modules, namely opaque, semitransparent and Aluminium base. The analysis is based on two models namely, thermal model and artificial neural network (ANN) model. The advantage of ANN model is that it does not require several parameters and complex calculations, unlike thermal model. The performance of opaque PVT-TEC collector [Case 1] has been studied by considering air [Case 1a] and water [Case 1b] as working fluids. The overall electrical efficiency and thermal efficiency of [Case 1b] is greater than [Case 1a] by 1.9–2.8% and 20.8–21.8%, respectively. Also, the impact of base cover material of PV module has been discussed by evaluating and comparing the performances of [Case 1b] opaque PVT-TEC water collector, [Case 2] semitransparent PVT-TEC water collector and [Case 3] Aluminium base PVT-TEC water collector. The results demonstrate that the daily overall electrical energy gain, daily rate of thermal energy gain and daily overall exergy gain is the highest for [Case 3] Aluminium base PVT-TEC water collector. Further, the results calculated from thermal model have been compared with ANN model and a fair agreement has been achieved.

Abstract A floating wave energy converter (FWEC) with central buoy (CB), circumferentially connected by a set of four, smoothly-finished tubular floats is proposed. The central buoy and floats are connected rigidly at one end while the other end is hinged, enabling a relative motion. The rotation of floats about the CB represents the energy extraction mode of the device. Float shapes of five different configurations, including a newly-proposed ‘bean float,’ are investigated to estimate their power outputs with linear PTO. FWEC remains afloat and re-centered using taut-moored tethers. The frequency-domain model is utilized to determine the hydrodynamic coefficients of the device, assuming a Potential Wave Theory (PWT). The research evaluates the impact of the obtained hydrodynamic coefficients on the average power absorbed by the FWEC. The influence of a linear power take-off (PTO) system on the average power output of FWEC is studied by optimization of the damping coefficients for the encountered regular waves. Further, time-domain analysis is carried out on the ‘bean float’ - FWEC configuration using an open-source computer-aided engineering tool called WEC-Sim (Wave Energy Converter Simulator), and MATLAB® - Simulink® implementing nonlinear buoyancy and Froude-Krylov forces.

Abstract Daylight has a significant role for energy conservation in buildings. Luminous efficacy models have been applied by many researchers to estimate the illuminance level from available irradiance data. In the present study, the characteristics of global (Kg) and diffuse (Kd) luminous efficacies are reported based on measured data for the humid sub-tropical region of New Delhi, India. Four existing efficacy models have been compared based on the measured irradiance and illuminance data. Statistical analysis indicates that the existing models performed poorly for the selected location. The performance of the models was significantly improved when the optimized coefficients were adopted using the measured data. Global and diffuse efficacy under clear, intermediate, overcast and all sky conditions, using existing and developed efficacy models were computed and compared. A good agreement has been exhibited for variation of efficacies with the measured values for different sky conditions from cloud to clear skies. Variation of global and diffuse efficacy for sky (clear, intermediate and overcast) w.r.t. solar altitude angle and sky clearness index has been presented. Finally, mean monthly global (Lg) and diffuse (Ld) illuminance were also estimated using the original and optimized version of efficacy models to provide impression of deviation of the models.

This article deals with comparative energy and exergetic analysis for evaluation of natural gas fired combined cycle power plant and solar concentrator aided (feed water heating and low pressure steam generation options) natural gas fired combined cycle power plant. Heat Transfer analysis of Linear Fresnel reflecting solar concentrator (LFRSC) is used to predict the effect of focal distance and width of reflector upon the reflecting surface area. Performance analysis of LFRSC with energetic and exergetic methods and the effect, of concentration ratio and inlet temperature of the fluid is carried out to determine, overall heat loss coefficient of the circular evacuated tube absorber at different receiver temperatures. An instantaneous increase in power generation capacity of about 10% is observed by substituting solar thermal energy for feed water heater and low pressure steam generation. It is observed that the utilization of solar energy for feed water heating and low pressure steam generation is more effective based on exergetic analysis rather than energetic analysis. Furthermore, for a solar aided feed water heating and low pressure steam generation, it is found that the land area requirement is 7 ha/MW for large scale solar thermal storage system to run the plant for 24 h.