The alkyl monoesters of fatty acids derived from vegetable oils or animal fats, known as bio diesel, are attracting considerable interest as an alternative fuel for diesel engines. Biodiesel-fueled engines produce less carbon monoxide, unburnt hydrocarbons, and particulate emissions than diesel-fueled engines. However, bio diesel has different chemical and physical properties than diesel fuel, including a larger bulk modulus and a higher cetane number. Some of these properties can be affected by oxidation of the fuel during storage. These changes can affect the timing of the combustion process and potentially increase the emissions of oxides of nitrogen. The objective of this study was to evaluate the effect of injection and combustion timing on bio diesel combustion and exhaust emissions. Bio diesel fuel is a clean burning fuel made from natural renewable sources such as rice bran vegetable oil. Bio diesel operates in compression ignition engines similar to diesel fuel. It can be burnt in any standard unmodified diesel engine blended with 20% to 30% bio diesel with diesel. Rice bran oil can be converted into bio diesel fuel as ethyl ester by transestirification. Experimental investigations have been carried out using bio diesel as an alternative fuel in single cylinder, compression ignition engine under varying operating conditions and by varying the injection timings with respect to TDC. In this work various parameters such as brake power, peak pressure rise, and emissions during combustion process under varying operating conditions with diesel, bio diesel, bio diesel blends were measured. The exhaust emissions from the engine were measured using exhaust gas analyzer.

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This paper presents a hand cranked generator or an exercise bicycle to generate small amount of energy which is effectively stored in a supercapacitor Bank. Supercapacitors can absorb and deliver huge bursts of power in a short span of time owing to its low ESR (Equivalent Series Resistance).If more charging current is given to the battery it may lead to excessive heating and decreases the life of the battery but the charging current limit of supercapacitors is very high. Thus it can be charged rapidly which is a very useful feature for energy harvesting applications. The energy generated by hand cranking or coupling the generator with an exercise bicycle rapidly charges the supercapacitor bank via a current limiter. The supercapacitor Bank can then be effectively discharged using a low voltage boost converter to store the energy in a battery or to power small devices. This way the energy generated by the exercise bicycle which is an ambient source of energy can be effectively utilized which would have otherwise gone wasted.

Conversion of human mechanical energy to usable electrical energy may seem like something from science fiction for the earliest generation of electronical engineers. But owing to the recent scientific advancements, it is no longer just a fiction but a reality. Researchers are working hard-time to improvise this idea by making attractive advancements in the field every day. This particular advancement gets much attention because it seems to be the most likely candidate to limit the usage of batteries, which have become a paradigm in the commercial world. Harvesting human energy can eliminate the limitations of scientific advancements in the portable and implantable devices due to the usage of batteries as their power source. There are several methods by which energy can be harvested from human activities, including but not restricted to thermoelectric generation, piezoelectric generation and triboelectric generation. These biomechanical phenomena can be tamed for commercial electricity usage under various circumstances. This paper provides a detailed review on these methods and the advancements made so far by researchers all around the globe.

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