Hydroelectric energy, Solar energy and Wind energy are called renewable energies.

Explanation

(i) Hydroelectric energy, solar energy and wind energy are all obtained without burning of a fuel.
(ii) They do not cause air pollution and are thus, eco-friendly.
(iii) Sunrise, rainfall, wind are natural phenomena.
(iv) These phenomena are constantly and continuously happening on earth.
(v) By setting up hydroelectric power plant, solar panel and wind mills we can obtain these energies continuously, uninterrupted and at low cost. Hence, these sources are called renewable energy sources.