This is the correct answer. Charcoal is smokeless and has the highest heat generation efficiency.

Fossil fuels are used in thermal power plants to heat water to produce steam, which runs the turbine and produces electricity.

This is the correct answer. Nuclear energy is obtained when uranium atom is bombarded with neutrons.

This is the correct answer. Hydropower plants convert the potential energy of the stored water into kinetic energy of the flowing water. The running water turns the turbine, which produces electricity.

This is the correct answer. It contains 75% methane and does not produce smoke, and leaves no residue.

This is the correct answer. In Denmark, 28% of electricity need is generated through wind power.

Anaerobic microorganisms convert the complex substance of slurry into methane and other substances in the absence of oxygen in  a few days.

This is the correct answer. The waste from the nuclear plants cannot be disposed off easily as it contains radioactive substances.

This is the correct answer. The entire process of manufacturing of solar cells is quite expensive.

This is the correct answer. Ocean thermal plants can operate only when the temperature difference between water at the surface and water at the depths up to 2 km is more than 293 K or 20^o C, which is required to boil liquid ammonia and the vapours run the turbine.

Nuclear energy is obtained when the nucleus of uranium atom is bombarded with low energy neutrons.

This is an incorrect answer. If the water is stored at a higher height, the potential energy of the water is more and hence, the kinetic energy of the water is also more. Thus, production of electricity is more.

This is the correct answer. Non-conventional sources of energy are those which are new sources of energy, derived to meet energy needs.

This is the correct answer. Concave mirror reflects and focusses the sunlight at a point, due to which temperature at the point increases, which heats and cooks up the food.

This is the correct answer. Solar cells are made up of silicon because when sunlight falls on them, they produce free electrons, which conduct electricity.