What type of energy is utilized by a sailing boat?

In a box-type solar cooker,what is the range of temperature that can be achieved in two or three hours?

Mention three advantages of converting domestic sewage to sewage gas.

"Electricity generated by the water stored in a dam can be considered to be another form of solar energy." Explain by describing the series of energy transformations in sequence taking place during the process.

Why should copper tubes be given a higher number of coils in a solar water heater?

$(i)$ Name the four gases commonly present in biogas.
$(ii)$ List two advantages of using biogas over fossil fuels.