Subject:- Renewable Energy Sources

Topic:- Wind Energy

Difficulty:- High

• The composition of biogas is as follows

Component and Composition ( % by Volume )

$CH_4$ - 50% to 60%

$CO_2$ - 30% to 40%

$H_2 S$ and $N_2$ - 5% to 10%

$H_2 S$ and $O_2$ - Very small amount

The presence of $CO_2$ in biogas reduces its octane rating. The octane rating of biogas is 110 with $CO_2$ . in case the $CO_2$ is removed from the biogas ($CH_4$) its octane rating increases to about 130 as against the octane rating of petrol of 87.

The properties of biogas are as follows.

• It has excellent antiknock properties compared to petrol since its octane rating is Higher than petrol.

• Its auto-Ignition temperature ($7300^oC$) is higher than petrol (4700) which make it a safer fuel therefore it can use higher compression ratio.

• It reading mixes with air even at low temperatures. Thus it does not need to provide rich mixtures at the time of starting or at no loads (idling).

• Only Dis-Advantages using bio-gas is that it has low heating value compared to petrol. However use of Higher C.R. can compensate the loss of power output.

• Application of biogas in petrol Engine :-

Biogas can be used in SI engines after starting the engine on petrol. It needs about 550 liters of gas per kwh to run a SI engine. The engine can either run purely on biogas. Also it can run as duel fuel engine either on biogas or petrol. It has advantage that the engine can run on petrol if the avalability of biogas is not there.

• Use of Biogas in Diesel – Engines :-

Biogas can be better used in C.I. engine in a duel fuel engine to improve its performance. It is more convenient to use bio-gas since it has high self ignition temperature of about $7300^oC$. Moreover , the engine can be switched from fuel operation to diesel operation almost instantaneously in case of emergency.

• Advantages of using Bio-gas in C.I. Engines.:-

• A uniform gas-air mixture is available in multi-cylinder Engine

• Co emissions are greatly reduced.

• Clean combustion reduces the wear of engine parts & the lubricating oil consumption.

• Only small amount of costly diesel fuel is needed to run the engine.

• Other Applications of Bio-gas :-

• As fuel for cooking.

• Power developed by engine using biogas can be used for lighting pumping of water etc.

• As fuel furnaces.

• Bio-mass :-

Biomass is an organic matter produced by plants, both grown on land & grown on water & their derivatives & animal manure. The energy obtained from biomass is called the biomass energy.