Power Plant Engineering

110 POWER PLANT ENGINEERING

The dimensional relationship of [E/C^2 ] is

2

J

(m/s)

=

2

2

N.m.s

m

=

N

m

s^2 = kg.

Example 2. A turbine generator unit has output of 150 mW and efficiency of 0.80. Calculate
energy supplied per hours by steam generator.

Solution. Output of turbine generator = 150 mW

Input to turbine =

150

0.8

= 187.5 mW

Energy input for 1 hour operation
= 187.5 (mW) × 1 (hr) = 187.5 mW-hr
1 mW hr = 3.6 × 10^9 J
187.5 mW hr = 675 × 10^9 J.
Example 3. A 100 mW geothermal power plant is operated for 11 months in a year. 1 month is
for maintenance shutdown. The cost of electrical energy supplied is Rs. 2.5/- per kW-hr. Calculate the
total earning by the power plant neglecting losses.
Solution. Total hours = (24 hr) × (30 days) × (11 months) = 7920 hrs
Total energy generated = MW × hr
= 100 × 7920 = 7920 × 100 mW hr = 792 × 10^3 kW hr
Total cost of energy sold
= kW hr × Rs. × kW hr = 792 × 10^3 × 2.5 Rs.
= Rs. 1980000.00.
Example 4. Calculate annual requirement of lignite (fuel) for a thermal power plant rated 2000
mW under following conditions.

Plant rating 2000 mW,

Annual load factor =

×

Energy Delivered

Rated power Total hours in year

= 0.5

Plant efficiency =

Electrical power output

Thermal power input = 0.25

Utility factor of fuel =

Useful energy in fuel

Available energy in fuel

= 0.7

Available energy density in coal = 14 mJ/kg.

Solution. Total energy delivered in year

(mW hr)e = Rated power × Hours × Load factor hours in year

= 365 × 24 = 8760 hrs

(mW hr)e = 2000 × 8760 × 0.5 = 8760000