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The use of Concentrated Solar Power technology for energy generation relies on the heating of fluids to high temperatures. One of the limitations of this technology is the low working efficiency of current solar receivers which hinders its application and utilization as a renewable clean energy source. This paper presents a novel concept to improve concentrated solar receiver efficiency through the recirculation of solid particles laden flow within the receiver. The recirculating characteristic of the fluid and solid particle mixture is expected to generate higher output fluid temperature than conventional solar receivers. This is expected to lead to significant improvements in the working performance of the concentrated solar receiver. The numerical study investigates this concept, using a commercial CFD package, employing the discrete particle model (DPM), a RNG k- e flow model and a discrete ordinate (DO) radiation model. It is found that the use of recirculating solid particles improves the energy absorption within the receiver and with it the thermal efficiency of the proposed solar receiver reaches to around 70%. Moreover, comparing this with a conventional solar receiver, this new concept exhibits a more uniform temperature distribution inside the cavity, which is mainly due to the recirculating flow characteristic and the well-controlled mixing of air and particles. The advantages of this novel concept of the solar receiver present its potential benefits in further applications in the process of energy conversion providing on enhanced heat transfer medium.

Solar distillation is one of the significant methods of getting fresh water from brackish and sea water by using free energy source from the sun. This is considered as the best solution for water production in remote, barren to semi- barren, small communities where fresh water is inaccessible. An experimental investigation is performed on a single slope solar still in the weather of Rajshahi, Bangladesh. The main purpose of this study is to evaluate the effect of phase change material (PCM) in a solar still and thus enhance its productivity. A single slope solar still with a basin area of 0.44105m2 is designed and constructed for this investigation. In this study,Bitumen has been used as phase change material to store thermal energy in the form of latent heat which offersgreat storage capacity per unit volume and per unit mass and provides heat during sunshine-off period. Results show that the efficiency of current solar still with PCM is comparatively higher than that of the still without PCM.

This study presents a numerical modeling of a downdraft gasifier. Wood (biomass) was considered as a feedstock for gasification as it is a cheap biomass and locally available. The numerical study was carried out to predict the flow behavior, the performance of the downdraft gasifier and the syngas composition precisely. The current downdraft gasifier was modeled using standard k–e turbulence model, DPM for discrete phase, nonpremixed combustion model for combustion and DO radiation model for radiation modeling. The flow behavior and the temperature distribution of the downdraft wood gasifier were addressed which helped to understand the internal combustion phenomenon. Results also showed that the predicted syngas compositions were as follows: Nitrogen-54.12%, Hydrogen-8.10%, Carbon Monoxide-16.04%, Carbon Dioxide-13.01%, Methane-2.35%, Water vapor-05.10% by volume. In addition gasifier, thermal efficiency was found about 72%. This gasification process produces syngas which is directly usable as an alterna...

The study presents an analysis and suggests about how renewable sources of energy can be an alternative option to produce electricity in an off-grid area. A case study is done by surveying 235 households in an off-grid area. Techno-economic analysis of the hybrid energy system is employed by using Hybrid Optimization of Multiple Energy Resources (HOMER) software. Four solar-PV modules (each of 1kW), two biogas generators (each of 3kW), three diesel generators (each of 5kW), five batteries (each of 160 Ah) and 5kW converter is found to be the best configuration in terms of Cost of Energy (COE), environmental conditions and Renewable Fraction (RF). The Cost of Energy (COE), Net Present Cost (NPC), capital cost of this configuration is found BDT15.382, BDT10007224, and BDT2582433 respectively. The renewable fraction of this system is found 75% which indicates a lower emission compared with thegrid based system and stand-alone diesel system. Although the COE is higher than grid electricity, this system offers a cheaper option than using kerosene oil and solar home systems (SHSs).

A recirculating flow solar particle cavity absorber (receiver) is modeled to investigate the flow behavior and heat transfer characteristics of a novel developing concept. It features a continuous recirculating flow of non-reacting metallic particles (black silicon carbide) with air which are used as a thermal enhancement medium. The aim of the present study is to numerically investigate the thermal behavior and flow characteristics of the proposed concept. The proposed solar particle receiver is modeled using two phase discrete particle model (DPM), RNG k-flow model and discrete ordinate (DO) radiation model. Numerical analysis is carried out considering a solar receiver with only air and the mixture of non-reacting particles and air as a heat transfer as well as heat carrying medium. The parametric investigation is conducted considering the incident solar flux on the receiver aperture and changing air flow rate and recirculation rate inside the receiver. A stand-alone feature of the recirculating flow s...