Renewable Energy Power Plants: MCQs, Short Questions with Answers & Explanations

Answer: c) Per capita energy consumption

Explanation: There is a direct correlation between a nation’s economic development and its energy use. High per capita energy consumption indicates advanced industrialization, better infrastructure, and higher domestic comfort levels.

Answer: d) availability can change due to climatic condition.

Explanation: Renewable sources like solar and wind are “intermittent.” Solar energy is unavailable at night or during heavy rain, and wind energy depends on fluctuating wind speeds, making them less predictable than coal or gas.

Answer: Carbon Dioxide \(CO_2\)

Explanation: While water vapor is the most abundant greenhouse gas, Carbon Dioxide is the primary gas emitted through human activities (burning fossil fuels, deforestation) and is the main driver of global temperature increases.

Answer: Greenhouse Effect

Explanation: Global warming occurs when greenhouse gases (like \(CO_2\) and methane) trap heat from the sun in the Earth’s atmosphere that would otherwise radiate back into space.

Answer: a) Solar energy

Explanation: Government initiatives like the National Solar Mission and subsidies (Feed-in Tariffs) have incentivized large-scale solar park installations and rooftop solar adoption across India.

Answer: b) Solar Energy

Explanation: Almost all energy forms—including wind (caused by uneven heating of the atmosphere), hydro (water cycle), and fossil fuels (ancient preserved plant matter)—are fundamentally derived from the Sun’s radiation.

Answer: c) direct as well as diffuse radiation

Explanation: A pyranometer measures “Global Solar Radiation,” which is the sum of the direct beam radiation and the diffuse radiation scattered by the atmosphere from the entire hemispherical sky.

Answer: b) Nuclear fusion reaction

Answer: b) Fill Factor

Explanation: The Fill Factor (FF) measures the quality of a solar cell. It is the ratio of the maximum power \(V_{mp} \times I_{mp}\) to the theoretical power determined by the Open Circuit Voltage and Short Circuit Current \(V_{oc} \times I_{sc}\).

Answer: Electromagnetic waves

Explanation: Solar energy travels through the vacuum of space as electromagnetic radiation, spanning a spectrum from ultraviolet to visible light and infrared.

Answer: Black (Dull/Matte Black)

Explanation: Darker colors, particularly dull black, have high absorptivity and low reflectivity, allowing them to capture the most thermal energy from sunlight.

Answer: Solar Module

Explanation: A single solar cell produces very low voltage. To provide useful power, many cells are connected in series/parallel and encapsulated into a “module.”

Answer: Silicon

Explanation: Crystalline Silicon (monocrystalline and polycrystalline) is the most abundant and standard semiconductor material used in over 90% of the world’s solar PV production.

Flat plate collectors are fixed, collect both direct and diffuse radiation, and are used for low-temperature applications (water heating). Concentrating collectors use mirrors/lenses to focus sunlight, require tracking, and reach much higher temperatures for power generation.

Beam radiation is solar radiation received directly from the sun without being scattered. Diffuse radiation is radiation scattered by atmospheric particles. Total (Global) radiation is the sum of both.

Answer: A cell is the basic semiconductor unit. A module is a collection of cells connected and framed. An array is a complete power-generating unit consisting of multiple modules connected together.

Answer: c) Velocity

Explanation: The power in the wind is proportional to the cube of its velocity \(P \propto v^3\). Even a small increase in wind speed leads to a massive increase in power output.

Answer: d) Blades

Explanation: The blades are the airfoils that physically interact with the wind to capture kinetic energy and convert it into rotational mechanical energy.

Answer: d) Horizontal type wind turbine

Explanation: Horizontal Axis Wind Turbines (HAWT) are significantly more efficient than Vertical Axis types because the blades move perpendicular to the wind, catching more energy throughout the entire rotation.

Answer: a) 1 year

Explanation: Most modern wind turbines generate enough energy to “pay back” the energy consumed during their manufacture and installation within 3 to 9 months.

Answer: Anemometer

Explanation: Usually, a cup-type anemometer is used on top of the wind turbine’s nacelle to measure wind speed and transmit data to the controller.

Answer: Aero-generator

Explanation: An aero-generator is the specific name for the machine that converts the mechanical energy of the wind turbine rotor into electrical energy.

Answer: Mechanical energy into Electrical energy

Explanation: Using electromagnetic induction, the generator uses the rotation of the turbine shaft to move conductors through a magnetic field, producing electricity.

Answer: Chennai

Explanation: NIWE is an autonomous R&D institution under the Ministry of New and Renewable Energy, located in Chennai, Tamil Nadu.

Answer: d) All of these

Explanation: The nacelle is the large enclosure at the top of the tower that contains the key power conversion components like the generator, gearbox, and braking systems.

Answer: a) 3 m/s

Explanation: Cut-in speed is the minimum wind speed required for the turbine blades to start rotating and generating usable power.

Answer: c) 59%

Explanation: The Betz Limit defines the maximum theoretical efficiency of a wind turbine as 59.3%. No turbine can capture 100% of the wind’s energy because the air must still be moving to exit the rotor area.

Answer: c) Dutch wind mill

Explanation: Darrieus and Savonius are Vertical Axis Wind Turbines (VAWT). Traditional windmills (like the Dutch style) and modern three-blade turbines are Horizontal Axis (HAWT).

Answer: d) Yaw control

Explanation: Yaw control is the mechanism that rotates the entire nacelle on top of the tower to keep the rotor facing directly into the wind as the wind direction changes.

Answer: b) Induction machine

Explanation: Specifically, Doubly Fed Induction Generators (DFIG) are widely used because they allow the turbine to operate efficiently over a range of different wind speeds.

Answer: b) 23 m/s to 25 m/s (Note: Units in options are km/hr, but standard “Cut-out” speed is usually 25 m/s).

Explanation: The “Cut-out speed” (approx. 25 m/s) is the limit at which the turbine is shut down and braked to prevent mechanical failure during high storms.

Answer: b) increases in cubic power of wind velocity

Explanation: This follows the equation $P = 0.5 \rho A v^3$. If wind speed doubles, the power increases eight times ($2^3=8$).

Answer: b) low head and small capacity.

Explanation: Small hydro plants are typically “run-of-river” systems built on small streams with low heads and capacities usually under 25 MW.

Answer: b) hydro power plant

Explanation: Hydroelectric plants utilize the energy of falling or flowing water to turn a turbine connected to a generator.

Answer: c) Hilly areas

Explanation: Hilly terrain provides the natural “head” (vertical drop) required to create high water pressure to drive the turbines.

Answer: Hilly

Explanation: Same as above; hills provide gravity-based water pressure.

Answer: Reaction (Axial flow)

Explanation: The Kaplan turbine is a water turbine with adjustable blades, used primarily for low-head and high-flow applications.

Answer: A water turbine converts hydraulic energy into mechanical rotation. Impulse turbines (Pelton) use the velocity of a water jet. Reaction turbines (Francis/Kaplan) use both the pressure and velocity of water.

Answer: b) Lower environmental impact

Explanation: Micro hydro does not require large dams or reservoirs, meaning they do not flood large areas of land or displace human populations and wildlife.

Answer: b) 30 m to 90 m net head with medium water flow rate

Explanation: The Francis turbine is a mixed-flow reaction turbine designed for medium-head and medium-flow conditions.

Answer: a) High head impulse turbine

Explanation: The Pelton wheel is an impulse turbine used for very high heads (up to 1000m or more) where a high-velocity jet of water strikes buckets on the rotor.

Answer: d) All of the above are equally true

Explanation: Micro hydro is sustainable because it is decentralized, eco-friendly, and provides electricity to remote rural areas without massive infrastructure.

Answer: d) Organic matter

Explanation: Biomass is renewable organic material that comes from plants and animals, such as wood, agricultural waste, and manure.

Answer: c) Transesterification

Explanation: Transesterification is a chemical process where vegetable oil or animal fat reacts with an alcohol (like methanol) to produce biodiesel and glycerin.

Answer: d) Water

Explanation: Biomass refers to recently living organic material. Water is an inorganic substance.

Answer: Anaerobic Digestion (or Fermentation)

Explanation: Biogas is formed when bacteria break down organic matter in the absence of oxygen.

Answer: Gobar Gas (in India)

Explanation: In India, it is commonly called Gobar gas as it is primarily produced using cow dung (Gobar).

Answer: Chemical

Explanation: Through photosynthesis, plants capture solar energy and store it as chemical energy in the form of glucose and other organic molecules.

Answer: Bio-fuel is fuel produced from contemporary biomass (like ethanol). Fossil fuels are ancient biomass (coal/oil). Bio-fuels are renewable and have a much lower net carbon footprint.

Answer: b) Methane

Explanation: Biogas/Gobar gas typically consists of 50–70% Methane ($CH_4$), which is the combustible component used for heating and power.

Answer: c) Producer gas

Explanation: Gasification is a process that converts organic materials into “Producer gas” (also called syngas), which is a mixture of Hydrogen, Carbon Monoxide, and Methane.

Answer: c) Cow dung

Explanation: Cow dung is the most widely used feedstock for small-scale biogas plants in rural sectors due to its high methanogen content.

Answer: b) Impurities

Explanation: Rectification is a distillation process used to purify the raw ethanol produced from fermentation, removing water and other impurities to make it suitable for fuel use.

Answer: d) CH4, CO2, H2S and N2 only

Explanation: Biogas is a mixture. While Methane ($CH_4$) and Carbon Dioxide ($CO_2$) are the primary gases, trace amounts of Hydrogen Sulfide ($H_2S$) and Nitrogen ($N_2$) are almost always present.