Renewable Energy Sources MCQ [Free PDF] – 8 Objective Questions with Answers

B — To produce methane-rich biogas from organic waste. Anaerobic reactors decompose organic matter without oxygen, giving biogas (mainly CH₄ and CO₂).

C — Bio-fuels. These are fuels such as ethanol, biodiesel and biogas obtained from biological material like plants, crop residues or organic waste.

An energy yield ratio of 14:3 means energy delivered : energy invested = 14 : 3. For 240 kJ invested, lifetime energy yield is 240×14/3 = 1120 kJ.

At the Northern Hemisphere summer solstice, the Sun's declination reaches approximately +23.45° (commonly rounded to +23.5°). This corresponds to the Sun being directly overhead near the Tropic of Cancer.

D — Modules. A single PV cell gives only about 0.5–0.6 V, so many cells are connected to form a module; modules form strings and arrays.

D — To heat the working fluid. Parabolic collectors concentrate sunlight onto a receiver tube, raising the temperature of the working fluid (e.g., thermal oil) that later produces steam.

A — Pyrolysis. It is thermal decomposition of biomass without oxygen, producing bio-oil, char and gas; gasification uses limited oxygen.

D — By changing the number of poles. Pole changing alters the synchronous speed (Ns = 120f/P), allowing operation at more than one speed band.