Abstract
Micro-algae are a large and diverse group of simple typically autotrophic organisms which have the potential to produce greater amounts of non-polar lipids and biomass than most terrestrial biodiesel feedstocks. Having emerged as one of the most promising sources for biodiesel production, they are gaining research interests in the current energy scenario due to their phenomenal growth potential (< 21 days log phase) in addition to relatively high lipids production which are also excellent source of biodiesel. In this study, engine performance and emission profile was performed using biodiesel fuels and blends from micro-algal technology in a compression ignition engine. The technology of micro-algae involved open pond cultivation and the use of photo-bioreactor model BF-115 Bioflo/celli Gen made in the US of 14 litre capacity (200 Lux light intensity) and flowrate of 2.5L/min. The micro-algal species used were Chlorella vulgaris and Scenedesmus spp. The biodiesel produced were blended with conventional diesel (AGO) at different proportions. The performance parameters evaluated include: engine power, torque, brake specific fuel consumption (BSFC), smoke opacity, thermal gravimetry, thermal efficiency, exhaust gas temperatures and lubricity while the varying effects of emission pollutants during combustion were also studied. Results showed that viscosity, density and lubricity have significant effects on engine output power and torque than when throttled with AGO which was used as control. Combustion efficiency and emission profile were better than the AGO due to the oxygenated nature of the micro-algal biodiesel which brought about complete combustion. A striking deduction arrived is that oxygen content of the algal biodiesel had direct influence on smoke opacity and emissions in the engine and also thermo-gravimetrically stable for other thermal applications. The engine tests (BSFC, BTE, ThE, MechE, EGT) and overall emissions (CO2, CO, VOCs, HC, SOx, NOx) were within acceptable limits and comparable with AGO. The implication of the study is that Micro-algal technology is feasible and can revolutionise development in biodiesel industry.
Highlights
There is constant rising worldwide demand for motor and power generation fuels together with environmental concerns in terms of greenhouse gases, climate change mitigation, economic growth and stability and the ongoing depletion of oil reserves
As the scope of study is on the performance of the biodiesel in a CI engine, methodology is limited to the use of produced algal biodiesel to power a four stroke diesel engine TD 300 and the various parameters measured as presented (2.2)
Even though polyunsaturated fatty acids produce more nitrogen oxides (NOx) than saturated fatty acids, but in this case a balance in composition was observed between saturation and poly-unsaturation which may be responsible for the low NOx levels
Summary
There is constant rising worldwide demand for motor and power generation fuels together with environmental concerns in terms of greenhouse gases, climate change mitigation, economic growth and stability and the ongoing depletion of oil reserves. These are all major factors for the development of economically, rational, renewable energy technology platforms [1, 2]. Climate change appears to be the most timeconstrained driver of renewable energy technology development This is because a reduction in CO2 emissions of 25 – 40% by 2020 and 80 – 90% by 2050 is predicted to be required to limit global temperature increases to less than the 2oC limit agreed at the 2009 Copenhagen Climate Change Summit [3].
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