Page 28 - June 2021

To figure out the amount of energy that can be

harvested from falling raindrops, we will need to

know how much rain is falling and how fast.

Although raindrops fall from miles above the

ground, they don’t accelerate the whole way

down. Instead, they reach a terminal velocity

within a few seconds when the force of air
resistance balances out the pull of gravity.

Because the terminal velocity is related to air

resistance, the value is different for
raindrops of different sizes. For example, a

raindrop on the heavier side would have a

terminal velocity of around 10 meters per

second (m/s), while drizzles would have a much
lower terminal velocity of 1 m/s.

For the sake of our exercise, let’s use the

outlandish amount of rain that fell near the
states in India, feature Arunachal

Pradesh, Sikkim, West Bengal, Odisha,

Uttarakhand, Karnataka and Kerala.

Rainfall at vadakara in keralafrom Aug 9 to 11 is

806 mm of water that fell there over the course

of three days represent about 0.447 inches