Question

A hydroelectric power station takes its water from a lake whose water level is 50 m above the turbine. Assuming an overall efficiency of 40%, calculate the mass of water which must flow through the turbine each second to produce power output of 1 MW. (Take g = 10 m s^-2)

Answer 1

Height h = 50 m, g = 10 ms^-2

Power out put = 1 MW = 10⁶ J/S

But this is only 40 %

∴ P.E. required = `100/40 xx 1000000`

= m × 10 × 50

= 2500000

Mass of water = m = `2500000/500`

= 5000 kg