Name a non-conventional renewable source of energy which can be harnessed for $24$ hours throughout the year.

In what form is geothermal energy stored in the Earth?

What do you mean by 'ocean thermal energy'? How can electricity be generated from this energy?

Name any two materials that are used to make solar cells.

Compare the advantages of generating energy from biomass with those of generating it from a hydropower plant.

Draw a labelled diagram of a floating gas holder type biogas plant and describe its working. Mention any two advantages of using animal dung for making biogas over using it as a fuel in the form of dried dung cakes.