Subject:- Renewable Energy Sources

Topic:- Wind Energy

Difficulty:- High

Calculate the following parameters of a biogas system.

a) Volume of Biogas Digester.

b) Power available from biogas Digester

Given:

Calorific value of methane:$28mJ/m^3$

Burner Efficiency:70%

No. of cows:8

Retention period:20 days

Temperature of fermentation:$300^o C$

Dry matter (cow dung )collected per cow per day:2kg

Density of matter in fluid (slurry) in digester=$50kg/m^3$.

Biogas yield=$0.2 m^3/kg$ of dry input

Methane proportion in Biogas:0.7

Given:-

No. of cowa=8; η burner=0.7

c.v of $CH_4 =28 MJ / m^3$

Retention Period = 20 Days.

Dry matter (caw dung) Collected /cow /day = 2kg.

Density , $P= 50kg /m^3$

Biogas Yield $=0.2 m^3 / kg$ of dry input

Method in biogas = 0.7

Find

1) Volume of biogas digesters :-

Mass of dry input / day

M = dry matter /cow/day X no. of cows

= 2 X 8 = 16Kg /day

Volume of fluid in digester,

$Vf= m(kg/day) /(P(Kg /m^3) )$

$=16 /50=0.32 m^3 /day$

Digester volume Vd= Vf X no. of days of retention period

$= 0.32 X 20=6.4 m^3$

Volume of biogas Vb = Biogas Yield Per Kg of dry Input X Mass of dry Input

= 0.2x16

$=3.2 m^3 / day$

2) Power Available from digester E: -

E= Efficiency of burner X C.V. of methane X Volume of biogas (Vb) x factor of methane in Gas

= 0.7 x (28 x 10³ KJ/m³)x 3.2x0.7

=43904 KJ/day = 43904÷(24x3600)

E = 0.508 KW