Name the largest component of biogas.

What is ocean thermal energy?

What do you suggest to overcome the problem of "limitation of sources of energy"? Mention any three suggestions for the effective use of energy.

The temperature difference required up to a water level difference of $1000 \,m$ for operating an Ocean Thermal Energy Conversion $(OTEC)$ system is: (in $^{\circ} C$)

Mention any one reason due to which most of the thermal power plants are set up near coal or oil fields.

What are the limitations in obtaining energy from wind?