Non Conventional Energy Source MCQ Quiz - Objective Question with Answer for Non Conventional Energy Source - Download Free PDF

String inverters handle groups of solar panels (strings) individually. If one string is affected by shading, dirt, or mismatch (like different panel orientations or aging), it only impacts that specific string, not the entire system.

In contrast, central inverters connect many strings together, and a problem in one string (like shading or a faulty panel) can drag down the performance of the whole system.

Thus, string inverters reduce power loss from partial shading or panel mismatch, increasing overall system efficiency and performance.

String Inverter Technology

• A string inverter connects a “string” of solar panels (typically 8–30 panels) to a single inverter. Each string is treated as an independent unit.
• DC power from each string is sent to a dedicated string inverter, which converts it to AC power. Multiple string inverters are used across a large system.

Central Inverter Technology

• A central inverter collects DC power from many strings (hundreds of panels), combined through DC combiner boxes, and converts all the power to AC in one large unit.
• DC strings feed into combiner boxes. Combiner boxes route the power to a single large inverter (hundreds of kW to MW). AC power is sent to the grid or a distribution system.

Leaving liquids uncovered in a refrigerator increases humidity, reduces efficiency, and leads to higher energy consumption. Covering liquids helps maintain lower moisture levels and keeps the refrigerator running efficiently, reducing energy costs.

Thus, option 3 is the correct answer because it is NOT an energy conservation measure but rather an energy-wasting habit.

• Use electronic chokes and fan regulators: Energy-efficient option as electronic chokes reduce power losses and regulators control fan speed efficiently.
• Use proper quantity of water for cooking: Helps in reducing unnecessary energy consumption during heating.
• Uncover all liquids placed in refrigerators: Uncovered liquids increase moisture inside the fridge, making the compressor work harder, and leading to higher energy consumption.
• Do not overload the washing machine: Prevents excessive energy and water usage, ensuring optimal efficiency.

The image shows a large collection of interconnected solar panels arranged in a grid to form a solar array.

Important terms related to Solar Plant:

• Solar Cell: The smallest unit that converts sunlight into electricity. Many solar cells make up a solar module.
• Solar Module (Panel): A single panel consisting of multiple solar cells connected.
• Solar Array: A group of multiple solar modules connected to generate higher power output. This is what is shown in the image.
• Battery Bank: A storage system for energy, but the image does not show batteries.

Explanation:

Ocean Energy Techniques

Ocean energy techniques utilize various mechanisms to harness the energy from oceanic processes. Among these techniques, Ocean Thermal Energy Conversion (OTEC) is a prominent technology that uses the thermal gradient between surface and deeper ocean waters. Let's examine the statements provided:

1. Statement 1: "Ocean thermal energy conversion (OTEC) technology uses the temperature difference between surface warmer water and deeper colder water encountered in oceans as the source of thermal energy." (Correct)

   • This statement correctly describes the basic principle of OTEC, which relies on the temperature gradient between warm surface water and cold deep water to generate energy.

2. Statement 2: "The open cycle of OTEC can be configured to produce desalinated water as well as electricity." (Correct)

   • In the open cycle OTEC process, warm seawater is evaporated under low pressure, and the steam produced drives a turbine to generate electricity. The steam is then condensed using cold seawater, resulting in desalinated water as a byproduct.

3. Statement 3: "The closed-cycle OTEC utilizes ocean water as a working fluid for power generation." (Incorrect)

   • In the closed-cycle OTEC, a working fluid with a low boiling point (such as ammonia) is used instead of ocean water. This fluid is vaporized by warm surface seawater, and the vapor drives a turbine to generate electricity. The vapor is then condensed using cold deep seawater and recirculated in the system.

Explanation:

Wound Rotor Induction Generators in Wind Turbines

Definition: Wound rotor induction generators (WRIGs) are a type of induction generator where the rotor windings are connected to external resistances through slip rings. This configuration allows for control over the rotor circuit resistance, making WRIGs suitable for applications requiring variable speed operations, such as wind turbines.

Working Principle: In a wound rotor induction generator, the stator windings are connected to the grid or load, while the rotor windings are connected to external resistances. When the rotor turns, an electromotive force (EMF) is induced in the rotor windings due to the relative motion between the rotor and the rotating magnetic field produced by the stator. By adjusting the external resistance, it is possible to control the rotor current and, consequently, the generator's output characteristics.

Advantages:

• Variable Speed Operation: Wound rotor induction generators allow for variable speed operation, which is critical for maximizing the efficiency and power output of wind turbines. This capability enables the turbine to operate efficiently across a range of wind speeds.
• Improved Power Quality: By adjusting the rotor resistance, WRIGs can improve power quality and reduce fluctuations in the output power.
• Enhanced Control: The ability to control the rotor resistance provides better control over the generator's performance, making it easier to optimize the turbine's operation under varying wind conditions.

Disadvantages:

• Complexity: The presence of slip rings and external resistances adds complexity to the generator's design and maintenance.
• Higher Cost: The additional components required for rotor resistance control can increase the overall cost of the generator.

Applications: Wound rotor induction generators are commonly used in wind turbines due to their ability to operate efficiently across a range of wind speeds and their enhanced control capabilities. They are also used in other applications requiring variable speed operation and improved power quality.

Correct Option Analysis:

The correct option is:

Option 4: Allow variable speed operation.

This option correctly highlights the primary advantage of using wound rotor induction generators in wind turbines. Variable speed operation is essential for wind turbines to optimize power generation and efficiency under varying wind conditions. WRIGs enable this by allowing adjustments to the rotor resistance, which in turn controls the generator's output characteristics. This capability makes WRIGs particularly well-suited for wind energy applications, where wind speeds can fluctuate significantly.

Additional Information

To further understand the analysis, let’s evaluate the other options:

Option 1: Reduce the overall cost.

While wound rotor induction generators offer several advantages, reducing the overall cost is not one of them. In fact, the complexity and additional components required for rotor resistance control can increase the overall cost of the generator compared to simpler designs like squirrel cage induction generators.

Option 2: Make the turbine noiseless.

This option is incorrect. The noise generated by a wind turbine is primarily due to aerodynamic factors and mechanical components such as the gearbox and blades, rather than the type of generator used. While WRIGs do not significantly contribute to noise reduction, their primary benefit lies in enabling variable speed operation.

Option 3: Increase the wind turbine size.

This option is also incorrect. The size of a wind turbine is primarily determined by the rotor diameter and the height of the tower, which are designed to capture the maximum amount of wind energy. The type of generator used does not directly influence the physical size of the wind turbine.

Conclusion:

Understanding the advantages and applications of wound rotor induction generators is crucial for recognizing their suitability for wind turbines. The key benefit of WRIGs is their ability to allow variable speed operation, which is essential for optimizing the performance and efficiency of wind turbines under varying wind conditions. This capability sets them apart from other types of generators and makes them a preferred choice for wind energy applications, despite their higher cost and complexity.

The correct answer is None of the above.

Key Points

• Ocean Thermal Energy also called Ocean Thermal Energy Conversion (OTEC) refers to a method of using the temperature difference between the deep parts of the sea which are hot and the shallow parts of the sea which are cold to run a heat engine and produce useful work. Basically, Ocean thermal energy conversion is an electricity generation system. 
• Ocean Thermal Energy Conversion uses the ocean thermal gradient between a cooler deep and warmer shallow or surface seawaters to run a heat engine and produce useful work, usually in the form of electricity.

Additional Information 

• The water at the surface of the sea or ocean is heated by the Sun while the water in deeper sections is relatively cold.
• This difference in temperature is exploited to obtain energy in ocean-thermal-energy conversion plants.
• These plants can operate if the temperature difference between the water at the surface and water at depths up to 2 km is 293 K (20C) or more.
• The warm surface- water is used to boil a volatile liquid like ammonia.
• The vapors of the liquid are then used to run the turbine of the generator.
• The cold water from the depth of the ocean is pumped up and condenses vapor again to liquid.
• The energy potential from the sea (tidal energy, wave energy, and ocean thermal energy) is quite large, but efficient commercial exploitation is difficult.

Central receiver system

Central receiver (or power tower) systems use a field of distributed mirrors also known as the heliostats that individually track the sun and focus the sunlight on the top of a tower.

By concentrating the sunlight 600–1000 times, they achieve temperatures from 500°C to 1000°C. 

A heat-transfer fluid heated in the receiver is used to heat a working fluid, which, in turn, is used in a conventional turbine generator to produce electricity. 

Biomass

Biomass is a renewable organic material that comes from plants and animals.

Biomass contains stored chemical energy from the sun that is produced by plants through photosynthesis. Biomass can be burned directly for heat or converted to liquid and gaseous fuels through various processes.

Some examples of biomass fuels are wood, crops, manure, and cow dung.

The correct sequence in increasing order is:

D < B < C < A

The correct answer is option 2.

The two major sources of energy can be classified under:

• Conventional Sources
• Non-Conventional Sources

​

Conventional Sources:

• It is also known as non-renewable sources of energy.
• It is available in limited quantity apart from hydro-electric power.

Non-Conventional Sources:

• It is also known as renewable sources of energy
• It uses again and again without depletion.
• Examples include solar energy, bio-energy, tidal energy, and wind energy.
   

Difference Between Conventional and Non-conventional Sources of Energy:

The correct answer is Silicon.

Key Points

Concept:

• Solar cell: A solar cell, or photovoltaic cell, is an electrical device that converts the energy of light (Sunlight) directly into electricity by the photovoltaic effect, which is a physical and chemical phenomenon.
• Solar cells are made of semiconductor materials like silicon, cadmium telluride, and copper indium gallium selenide.
• The working principle of solar cells is based on the photovoltaic effect.
• The photovoltaic effect is the production of electricity by a material when it is exposed to light.
• The common single-junction silicon solar cell can produce a maximum open-circuit voltage of approximately 0.5 - 0.6 V.

Explanation:

• For making the solar cell, semiconductor materials are used such that silicon, cadmium telluride, and copper indium gallium selenide.
• Copper, Iron, and Aluminium are conductors and metals they are used to make wires and various metallic object.

So, The material is used for making Solar cells is Silicon.

The two major sources of energy can be classified under:

• Conventional Sources
• Non-Conventional Sources

​

Conventional Sources:

• It is also known as a non-renewable source of energy.
• It is available in limited quantity apart from hydroelectric power.

Non-Conventional Sources:

• It is also known as a renewable source of energy
• It uses again and again without depletion.
• Examples include solar energy, bio-energy, tidal energy, and wind energy.
   

Additional Information

Difference Between Conventional and Non-conventional Sources of Energy:

Different types of Solar cell and their efficiency is shown below:

Out of the following solar cell, the Monocrystalline panel has higher efficiency but is expensive too.

• Wind energy is harnessed by using a wind turbine generator.
• Wind turbines convert the energy in wind to electricity by rotating propeller-like blades around a rotor. The rotor turns the drive shaft, which turns an electric generator.
• Three key factors affect the amount of energy a turbine can harness from the wind are wind speed, air density, and swept area.
• At Hydropower plant salient pole type alternator is used to convert hydro energy into electrical energy.
• Steam turbine-driven generators (Turbo generators) are commonly used in solar thermal electric power plants, coal, geothermal, nuclear, waste incineration plants, and natural gas power plants.

Advantages of Tidal Energy:

• Tides are easily predictable
• Inexpensive to maintain
• Reliable and renewable source of energy
• High energy density than other renewable energy forms
• It produces no greenhouse gases or other waste
• Vertical-axis turbines and offshore turbines are inexpensive to build and have a less environmental impact
• Tidal turbines are 80% efficient, which is higher than solar or wind energy generators.
• Barrages reduce the damage of high tidal surges on the land.
   

Disadvantages of Tidal Energy:

• Initial construction cost is very high and not economical.
• Formation of silt behind the barrage.
• Effect on animals and plants living near tidal stations.
• Very few suitable sites for constructing barrages.
• Disturbs migration of living creatures in the ocean.
• Water cannot be replenished, and hence dirt gets settled within the coast.
• It produces power for only about 10 h of the day when the tide is moving in and out.

Additional Information 

Tidal Energy:

It is a kind of Non-conventional or renewable energy source.

Tides are alternating rise and fall of water level of the sea which is caused by the gravitational action of the kinetic energy of sun and moon on the water and earth.

The waveform of Tides of Sea:

Basic principle of Tidal Power Plant:

• A dam is constructed in such as way that a basin gets separated from the sea and a difference in water level is obtained between basin and sea.
• The basin is filled during high tides and emptied during the low tides through the turbine.
• The potential energy of water stored in the basin is used to drive the turbine which turns into electrical energy by means of a generator.

The correct answer is option 1.

Biomass

• Biomass is renewable organic material that comes from living organisms, such as plants and animals.
• The most common biomass materials used for energy are plants, wood, and waste. 
• Biomass can be converted into useful products such as bio-fuels, bio-char, syngas, power, heat, and fertilizer by a process called biomass gasification.
• Burning biomass releases methane, hydrogen, carbon monoxide, carbon dioxide, nitrogen oxides, and other pollutants and particulates.
• If these pollutants are not captured and recycled, burning biomass can create smog and severe health problems.