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Hence,
Heat gained by vessel = Mv * Sv * (T b - T { ) Joule
Heat gained by water in HPP = Mw * Sw * (T b - T } ) Joule
Heat gained by water in LPP = (M SIeam * L wboil ) Joule
Energy of fuel = (M fuel * K fuel ) Jules
Where,
M v
S v
= Mass of vessel
= Specific heat capacity of vessel
(T b -T 1 ) = Change in temperature (from Tl to boiling Point)
M w = Mass of water
S w = Specific heat capacity of water
M SIeam = Mass of evaporated water during LPP
L wboil = Latent heat of boiling of water
M fuel = Mass of consumed fuel
K fuel = Calorific values of fuel^
Efficiency (overall) = {M w * S w * (T b – T 1 } + M SIeam * L wboil + M v * S v * (T b – T 1 )}/ (M fuel * K fuel )
Efficiency (overall) - {Heat gained by water in HPP + Heal gained water in LPP + Heat gained by
vessel} /{Quantity of fuel consumed * unit calorific values of fuel}
Hence, heat gained vessel (made from aluminium) is equal to heat gained from T1°C to T boil °C and heat
gained by water is equal to the summation of heat gained during High Power and Low Power Phase.
Fuels like LPG and kerosene could be weighted by weighting machines. Mass of cylinder or stove before
and after experiment gives the mass of fuel consumed. But for biogas, measurement of flow of gas is
essential, which gives the amount of biogas consumed during experiments.
The efficiency of biogas stove calculated as per adopted methodology mentioned above is found to be 49.44
percent, 43.80 percent and 32.26 percent for perfectly controlled, semi-controlled and uncontrolled
conditions respectively.
The efficiency of a given stove is not constant. It could vary on the basis of surrounding conditions and
quality of fuel used. A high value of efficiency could be obtained under controlled conditions. But in practice
this value is normally lower than the value found in the controlled laboratory condition
(CES/IOE, 2001).
4.2 MERITS AND DEMERITS OF BIOGAS
Like other equipments, biogas plant has both merits and demerits (more merits than few demerits). The
merits and demerits identified so far are described below:
4.2.1 Merits of Biogas
a. Energy Available
As biogas plant utilizes locally available raw materials, the gas obtained from it can be cheaper and reliable.
Biogas can be used for following purposes to save energy:
■ Fuelwood can be saved while using if for cooking
■ Kerosene can be saved while using it for lighting and refrigeration;
■ Diesel can be saved while using it for running
■ Electricity will be generated while using it for electricity generation.
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