Question

How to convert gravitation potential to heat energy?

Answer 1

All hydroelectric power stations work on the power of falling of water from heights, and potential energy of water gets converted to kinetic energy due to, which is used to run turbines of generators.

Hydropower energy storage uses extra power to raise height of water by pumping to higher reservoir, and using this water to run turbines by using its potential energy in times of need to run generators. So you are using kinetic — potential— kinetic energy conversions in the process, using gravitational difference of potentials to generate electricity.