Fossil fuels that mainly supply the current increasing world’s energy demand originated from non-renewable resources. In addition to the depletion of their resources within the next short time, the combustion of fossil fuels to power industries and transportation also negatively impacts humans and the environment due to the release of various gaseous pollutants. To increase the share of renewables in the primary energy mix, the Government of Indonesia is currently struggling to meet a target of 23% by 2025. Therefore, more significant efforts to search for potential renewable energy sources are the only way to overcome this issue. Bioethanol is an eco-friendly renewable energy source since its combustion emits a low concentration of pollutants. Microalgae have gained significant interest in bioethanol production because of rapid biomass growth and relatively easy pre-treatment steps. It is renewable, carbon-neutral, sustainable and can be grown in wastewater coupling as wastewater treatment. This paper reviews bioethanol production, providing knowledge on the characteristics of microalgae potential for producing biomass to be converted into bioethanol, introducing process for bioethanol production, and presenting the potential challenges of bioethanol as a future renewable energy.

Abstract. This paper presents the results of numerical modelling of temperature distribution and flow pattern in a biomass cooking stove using CFD simulation. The biomass stove has been designed to suite the household cooking process. The stove consists of two pots. The first is the main pot located on the top of the combustion chamber where the heat from the combustion process is directly received. The second pot absorbs the heat from the exhaust gas.A chimney installed at the end of the stove releases the exhaust gas to the ambient air. During the tests, the height of chimney was varied to find the highest temperatures at both pots. Results showed that the height of the chimney at the highest temperatures of the pots is 1.65 m. This chimney height was validated by developing a model for computational fluid dynamics. Both experimental and simulations results show a good agreement and help in tune-fining the design of biomass cooking stove.

This study focuses on the investigation of the performance of dissimilar turbulence models on the calculations of flow-field and reactive scalars (temperature and species) of a turbulent non-premixed flame. Turbulence models examined in this study included: the standard k-ε, RNG k-ε, standard k-ω, SST k-ω (Shear Stress Transport) and the Reynolds Stress Model (RSM). For the sake of ease and simplicity, Eddy Dissipation combustion model (EDM) was used to calculate the temperature fields and species concentrations in the flame. Predictions generated by different turbulence models are then compared and validated against experimental measurements from a turbulent methane-air flame called flame A. Experimental measurements of flame A provides data on velocity, temperature and species concentrations. Results of the investigation showed that among five turbulence models tested, the standard k-ε model provides the predictions that are in closer agreement to the experimental data of flow-field, temperature, and species concentrations. In general, it can be deduced that apart from the standard k-ε model, other turbulence models are not capable of capturing the position and the value of peak temperature accurately. On the other hand, the standard k-ε turbulence model is able to accurately capture the position and compute the value of peak temperature in the flame. This is attributed due to a better prediction of the flow-field by the standard k-ε turbulence model than those of other turbulence models. These findings indicate that the standard k-ε turbulence model in combination with Eddy dissipation combustion model is capable of producing accurate predictions of flame flow-field and temperature.

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