No abstract

In this study, Vietnamese spent coffee ground (SCG) were subjected to produce biodiesel for fuel application. The extraction processes were conducted with three organic solvents, i.e., hexane, petroleum ether and dimethyl ether. The extraction oil seems to be favored in hexane solvent (17.06%) as compared with petroleum ether (16.62%) and dimethyl ether (16.18%). The extraction processes tend to sufficiently follow the empirical hyperbolic model with R 2 of 0.973, 0.970 and 0.969 for hexane, petroleum ether, and dimethyl ether. The transesterification was optimized using Taguchi design with three variable molar ratios of MeOH and extracted oil (MeOH/EO), catalyst (NaOH) concentration and temperature. The transesterification reached the best yield 76.23% at MeOH of 6:1, NaOH of 0.75 wt% and temperature of 55 °C. Some acquired biodiesel quality was determined within the American Society for Testing and Materials and European standards (EN) norms for biodiesel. Life cycle assessment was also performed to evaluate the impact of the SCG biodiesel production; the industrial process was designed based on laboratory tests aimed with TRACI 2.1 tool. The obtained results indicated that oil extraction is the most effective on biodiesel production, contributing to global warming around 21.04 kg CO 2 eq/kg.

This paper presents a method to estimate the yield and analyze the performance of a grid-connected photovoltaic (PV) power plant including a rooftop PV system and a solar farm. The yield model was developed based on a commercial PV model in a MATLAB/Simulink environment. A simulation model is built to connect with the PV rooftop system and the solar farm in which their total installed capacities are 0.986 and 30.7 MW, respectively. The simulated and measured final yield results of a rooftop PV system in Vietnam are compared. Additionally, this paper provides a function of reducing the final yield corresponding to different PV operation temperature values. Furthermore, the performance of both a rooftop PV system and a solar farm, in Vietnam, are evaluated as the rated power of 0.986 and 30.7 MWp, respectively. The results also show that their performance is satisfactory, in which the value of the performance ratio (PR) average reaches 70% for the rooftop PV system and 80.45% for the solar farm within a six-month period, in 2019. The PR is also compared with a global PR average from 70% to 80% for a sufficiently well-performed solar system.

No abstract

Absorption refrigeration cycle used a common mixture of NH3-H2O has been developing widely. However, almost previous studies are system theory studies and exclusive applications or experimental studies for each component of the system. This paper is (shown?) showed the state points of the fluids in designed NH3-H2O absorption refrigeration machine that is the corporation of theoritical (theoretical?) calculations and practical measurements of a completed machine and steady working. The purpose of this paper is optimizing the working condition for (the?) entire machine according to the condition in Vietnam and satisfying the heat supplying (supply?). The correlation of optimal generation temperature with condensation, absorption and evaporation temperatures of the machine components are set into (a?) an regression equation which was established in the multivariate regression method. The optimal coefficients of performance were compared with experiments having the average deviation is 1.2% and with other studies having the deviations are from 2 to 7%.