Analysis and comparison of the performance parameters of passive and active indirect solar dryers with heat storage facility while drying carrot.

The performance of passive and active convection indirect solar drying systems provisioned with paraffin wax as heat storage was examined while drying carrot slices. The passive indirect solar dryer (type-I) was made initially, and it was upgraded with solar-powered fans to promote mass flow rate. The new assembly was considered an active setup (type-II). Data collected during experiments were analyzed to determine performance parameters and drying kinetics. There were average improvements of 11.8%, 12.2%, and 20.7% in actual heat supply, activation energy, and specific energy consumption in type-II compared to type-I. The averaged values of collector efficiency of type-I and type-II were 59.7 and 67.8%, and the drying efficiency was 11.1 and 14.2%, respectively, while their respective improvements were 13.6 and 27.93%. It was found that the coefficients of moisture diffusion (De), heat transfer (h), mass transfer (hm), and the rate of specific moisture extraction were increased by 20.83%, 16.9%, 14.52%, and 27.8%, respectively in type-II compared to type-I. A logarithmic correlation was observed for De, h, and hm demonstrating a decrease in moisture content (MC) increased the variables. The MC was diminished from 9.13 to 0.478 kg/kg of db in 15 h in type-I and 12 h in type-II with a 3 h saving in drying time with a better drying rate in type-II. The reliability of the results was assessed with uncertainty analysis.

A critical review on solar chimney power plant technology: influence of environment and geometrical parameters, barriers for commercialization, opportunities, and carbon emission mitigation.

Solar chimney power plant (SCPP) is one of the promising technologies to convert solar energy into carbon-free power generation. It has cost competitiveness, environment friendly and longer service life. Although remarkable advancements were achieved, commercialization aspect of the SCPP has not been established so far. Feasibility assessment of the large-scale plants was carried out by researchers in different climatic conditions across the globe but none of the studies materialized to date. However, it is almost four decades from the development of the first prototype, and no studies have been discussed the barriers to commercialization of the SCPP yet. Therefore, in this present study, a-state-of-the-art review has been presented which discussed the overview of SCPP technologies, factors affecting the flow and performance characteristics of the plant and major barriers in the commercialization aspect of the plant. The overview of SCPP technology including its global status and recent advances are spotlighted. The power potential and carbon emission mitigation of the SCPP based on the climatic condition and geographical location was studied by taking India as an example. In addition to that, the major challenges and opportunities in the SCPP are also addressed. Based on the analysis, a few recommendations are given for commercialization the plant.

Effect of start of main injection timing on performance, emission, and combustion characteristics of a VGT CI engine fueled with neem biodiesel.

The performance of engine parameters is more influenced with fuel injection strategies namely start of main injection timing (SoMI). An experimental analysis was performed to find the optimum SoMI timing based on performance, emission, and combustion characteristics. Base fuel of diesel and neem biodiesel was used as test fuels. The neem biodiesel was prepared by esterification and transesterification process. It is found from literature that neem biodiesel blend NB20 with diesel gives optimum performance and emission characteristics; therefore, NB20 blend was used for experiments. A variable geometry turbocharger (VGT) compression ignition (CI) engine was used to conduct the experiments. Engine performance parameters were estimated and compared with a base fuel of diesel and with NB20 blends. In this experimentation, fuel injection pressure (FIP) of 800 bar and engine speed of 1700 rpm were considered. SoMI timing was varied from 2° to 10° bTDC with an increment of 2° bTDC timing. Cylinder pressure (CP) and heat release rate (HRR) were estimated and found that are higher for diesel fuel compared to NB20 blend at different SoMI timings. The addition of neem biodiesel NB20 blend to diesel fuel decreases the exhaust emissions except NOx emissions. The BSFC was considerably reduced and BTE was improved almost equivalent to the diesel fuel for NB20. From the results, it is concluded that 10° bTDC SoMI timing provides 13% improvement in BTE, 21% decrement in BSFC, and 7.5% reduction in CO2 emissions.