Renewable Energy Sources Questions and Answers

Answer: D

Biogas is predominantly methane.

Biogas is produced by the anaerobic digestion of organic matter such as cattle dung, crop residues and sewage sludge. It typically contains about 55 to 70 per cent methane and 30 to 45 per cent carbon dioxide, with small amounts of hydrogen sulphide, hydrogen and water vapour. The methane is what makes it a fuel.

Hydrogen and carbon monoxide are minor or absent, and ethane is not a significant component. Producer gas, not biogas, is the fuel rich in carbon monoxide.

Answer: C

The renewable source is hydroelectric power.

Hydroelectric power uses flowing or falling water, which the water cycle, driven by the sun, replenishes continually.

Natural gas and petroleum oil are fossil fuels, finite stocks formed over millions of years. Nuclear power depends on uranium, a mined and finite resource, so it is classed as non-renewable even though it emits little carbon.

Answer: B

The ISA was founded in 2015 in Paris.

The International Solar Alliance was launched by India and France on 30 November 2015 at the COP21 climate conference in Paris. Its headquarters are at Gurugram, India, and its framework agreement entered into force in December 2017.

2017 is the year the agreement took effect, not the founding, and the London dates are wrong in both year and place.

Answer: A

Pairs (1) and (3) are correct: hydrogen is an alternative energy and solar energy is used for water heating.

Biogas comes from degradable waste and geothermal energy uses heat from the Earth, not wind, so (2) and (4) are wrong. Option A.

Hydrogen is an alternative energy source and solar energy is used in water heaters. Biogas is made from biodegradable waste such as dung and kitchen waste, not from non-degradable waste, and geothermal energy comes from the Earth's heat, not from wind speed and direction.

Answer: B

The main source of wind energy is the Sun's uneven heating of the Earth.

The Sun heats land and sea, and the equator and the poles, by different amounts. Warm air rises and cooler air flows in to take its place, creating differences in pressure that move air as wind. Wind power is therefore an indirect form of solar energy.

The Earth's rotation deflects winds (the Coriolis effect) but does not supply their energy. Ocean currents are themselves driven largely by winds, and gravitational force is the energy behind tidal power, not wind.

Answer: B

The source that is not renewable is natural gas.

Natural gas is a fossil fuel formed from organic matter over millions of years. Once extracted and burned it cannot be replaced on any human time scale, so it is non-renewable.

Geothermal energy (the Earth's internal heat), flowing water (hydropower) and biomass (plant and animal matter that regrows) are all renewable sources.

Like coal and petroleum, natural gas also releases carbon dioxide when burned, whereas the renewable sources are replenished by natural processes.

Answer: B

The untrue statement is The output power of solar cell is high.

A single solar cell produces only a small voltage (about 0.5 volt for a silicon cell) and a small power, and typical commercial cells convert only about 15-20% of the sunlight falling on them into electricity. That is why many cells are joined into panels and arrays.

The other statements are true. A solar cooker burns no fuel and so causes no pollution. Ocean thermal energy uses the temperature difference between warm surface water and cold deep water, whereas tidal energy uses the rise and fall of the tides. Nuclear plants do carry a risk of accidental radiation leakage, as Chernobyl and Fukushima showed.

Answer: C

Ocean thermal energy is due to the temperature difference at different levels in the ocean.

In tropical seas, surface water is warmed by the sun to about 25-28 °C while water a kilometre down stays at about 5 °C. Ocean thermal energy conversion (OTEC) uses that difference of 20 °C or more to run a heat engine, typically by vaporising a working fluid such as ammonia with warm water and condensing it with cold water.

Tides produce tidal energy and waves produce wave energy, both of which are separate technologies. Pressure differences with depth are not used to generate this kind of power.

Answer: A

Running water is the source of hydel power.

Hydro-electric (hydel) power is generated when flowing or falling water turns turbines connected to generators, which convert the water's kinetic and potential energy into electricity. Dams store river water so that it can be released through the turbines when needed.

Thermal power comes from burning coal, oil or gas to raise steam, and nuclear power from the heat of nuclear fission; neither uses running water as its energy source. Since hydel power does, 'None of the above' is wrong.

Answer: C

The resource that is not renewable is fossil fuel.

Coal, oil and natural gas formed from the remains of plants and animals over millions of years. Once burnt they cannot be replaced on any human time scale, so they are non-renewable, and burning them also releases carbon dioxide.

Solar energy, wind energy and hydel (hydroelectric) power come from sunlight, moving air and flowing water, which nature renews continuously, so all three are renewable.