Category: Renewable Energy Objective Questions

Ocean Energy Multiple Choice Questions on “Ocean Thermal Energy – 1”.

1. What is ocean thermal energy conversion?
a) Harnessing the temperature differences between surface waters and deep ocean waters
b) Harnessing the temperature differences between the coastal waters and deep ocean waters
c) Harnessing the heat energy from the underwater volcanoes
d) Harnessing the heat energy between surface water vapour and atmospheric gases

Answer: a
Clarification: The process of generating energy by using temperature difference (or gradient) varying with depth of seawater is called Ocean thermal energy conversion (OTEC). A temperature gradient exists between the surface waters and deep sea waters due to various physical phenomenon.

2. What is the temperature difference used in ocean thermal energy conversion? Note that F denotes Fahrenheit
a) 10 degree F
b) A minimum of 77 degree F
c) Between 50 and 60 degree F
d) A minimum of 100 degree F

Answer: b
Clarification: The temperature difference is at least 77 degree F (or 25 degree C). Ocean thermal energy conversion systems use this temperature difference between the surface and the bed (or deep sea waters) to generate electricity.

3. What is thermohaline circulation?
a) Circulation of halogens throughout the ocean
b) Circulation of halogens due to temperature differences throughout the ocean
c) Large scale ocean circulation driven by global density gradients
d) Large scale halogens circulation due to global density gradients

Answer: c
Clarification: Thermohaline circulation is a constituent of large scale ocean water movement and circulation caused due to global density gradients. The cause for this gradient is heat of the surface and freshwater fluxes. Halogens are group 17 elements in the periodic table and are not related to thermohaline circulation.

4. What is the maximum estimated potential of ocean thermal energy conversion per year?
a) 80 GWh
b) 900 MWh
c) 10000 TWh
d) 88000 TWh

Answer: d
Clarification: Ocean thermal energy conversion is one of the continuously available renewable energy resource. The maximum estimated potential is 880000 TWh per year. In fact, it is strongly believed that this resource could contribute to base-load power supply.

5. How does the cold and denser water masses sink to the depths of ocean?
a) Thermohaline circulation
b) Temperature gradient
c) Density gradient
d) Freshwater fluxes

Answer: a
Clarification: The cold and denser water masses formed by surface water sink to the depths of the ocean by thermohaline circulation. It is circulation of ocean water due to density gradient.

6. Why is ocean thermal energy conversion a renewable resource?
a) Because the temperature gradient lasts for a short period of time
b) Because the upwelling of cold water from the deep ocean is replaced by downwelling of surface waters
c) Because ocean water is available in plenty
d) Because of sun’s heat

Answer: b
Clarification: Ocean thermal energy conversion is a renewable resource because the temperature gradient is continuously restored. This occurs because the upwelling of cold water from the deep ocean is replaced by downwelling of surface waters.

7. Which of the following are types of systems used in ocean thermal energy conversion?
a) Horizontal and vertical
b) Vertical and open cycle
c) Open cycle and closed cycle
d) Horizontal and closed cycle

Answer: c
Clarification: The types of systems used in ocean thermal energy conversion are closed cycle and open cycle systems. Horizontal and vertical are related to turbines used in harnessing tidal and wind energy.

8. Which of the following is used as working fluid in closed cycle oceanic thermal energy conversion systems?
a) Thermohaline circulation
b) Temperature gradient
c) Greenhouse gases
d) Refrigerants

Answer: d
Clarification: Closed cycle oceanic thermal energy conversion systems use refrigerants like ammonia as working fluids. These fluids have low boiling points and are suitable to power the generator thereby producing electricity.

9. Rankine Cycle is the most commonly used heat cycle for ocean thermal energy conversion.
a) True
b) False

Answer: a
Clarification: Rankine Cycle is the most commonly used heat cycle for ocean thermal energy conversion. It is a model used to predict the performance of a steam turbine and was also used to study reciprocating steam engines.

10. _______ turbine is used in closed cycle ocean thermal energy conversion.
a) Horizontal
b) Low-pressure
c) High-pressure
d) Vertical

Answer: b
Clarification: Low-pressure turbines are used in closed cycle ocean thermal energy conversion. These systems use the Rankine heat cycle to generate electricity.

11. Open cycle ocean thermal energy conversion systems use _____ as the working fluid.
a) vapour from rivers
b) water from rivers
c) vapour from seawater
d) seawater

Answer: c
Clarification: Open cycle ocean thermal energy conversion systems use vapour from seawater as the working fluid. Unlike the closed cycle ocean thermal conversion systems, the working fluids are not thought as refrigerants.

12. What is the byproduct of an ocean thermal energy conversion system?
a) Electricity
b) Clean water
c) Water vapour
d) Cold water

Answer: d
Clarification: Ocean thermal energy conversion systems supply cold water as their by-product. These can be used for air conditioning and refrigeration. Electricity is the primary product.

13. Where is the world’s only operating ocean thermal energy conversion plant located?
a) Japan
b) United States
c) China
d) Korea

Answer: a
Clarification: Ocean thermal energy conversion was first developed in the 1880s. The world’s only operating ocean thermal energy conversion plant is located in Japan. The plant is overseen by Saga University.

14. Which of the following best describes the working of an ocean thermal energy conversion plant?
a) Oceanic water → evaporator → turbine/generator → electricity
b) Warm surface oceanic water → evaporator containing working fluid → turbine/generator → electricity
c) Cold surface oceanic water → electricity → evaporator containing working fluid → turbine/generator
d) Cold deep oceanic water → electricity → evaporator containing working fluid → turbine/generator

Answer: b
Clarification: Warm surface oceanic water is passed through an evaporator containing the working fluid. The vapourized fluid drives the turbine/generator thereby generating electricity. Deep oceanic water is not used as it’s cold.

15. The vapourized fluid in an ocean thermal energy conversion system is converted back into working liquid.
a) True
b) False

Answer: a
Clarification: The vapourized fluid in an ocean thermal energy conversion system is converted back into working liquid by passing it through a condenser. By using the deep oceanic cold water, the temperature of the condenser is maintained so as to cool the vapourized fluid.

Renewable Energy Multiple Choice Questions on “World Energy Status -1”.

1. Which of the following best describes world energy consumption?
a) Total energy produced and used by humanity
b) Total energy consumed by humanity
c) Total energy consumed by humans in the biological pyramid
d) Total energy produced by humans in the biological pyramid
Answer: a
Clarification: World energy consumption is the total energy produced and used by humanity. It includes all energy harnessed from every source.

2. Which of the following is NOT included in world energy consumption?
a) Solar energy
b) Energy from food
c) Energy from wind
d) Energy from fossil fuels
Answer: b
Clarification: Energy from food is not included in world energy consumption. Since the energy consumption from biomass is difficult to calculate, it has not been well-documented.

3. World energy consumption is measured _______
a) quarterly
b) half-yearly
c) yearly
d) every decade
Answer: c
Clarification: World energy consumption is generally measured year. It involves all energy harnessed from every possible energy source towards humanity’s endeavors.

4. Which of the following energy sources is majorly used?
a) Wind energy
b) Nuclear energy
c) Hydrogen energy
d) Fossil fuels
Answer: d
Clarification: Burning fossil fuels supplies more than 80 percent of world’s energy. It is the major cause of some of the world’s pressing problems like global warming and climate change.

5. Which of the following is perceived to contribute towards world population growth?
a) Uganda
b) USA
c) UK
d) Germany
Answer: a
Clarification: Developing countries like Uganda, Botswana, India, China, etc. are perceived to contribute towards immense growth of world population. This is because of poverty and high infant mortality rate.

6. Why is there a demand for renewable sources of energy?
a) Because they emit greenhouse gases
b) Because of low or zero carbon footprint
c) Because of the decreasing global temperatures
d) Because they are more efficient
Answer: b
Clarification: Renewable energy sources are required because they have zero or extremely low carbon footprint. Thus, greenhouse gas emissions from such sources are negligible as compared to fossil fuels.

7. As the population grows, the demand for energy ________
a) decreases
b) remains the same
c) increases
d) becomes volatile
Answer: c
Clarification: As world population increases, the demand for energy increases. This is because energy demand and consumption per capita increases.

8. Which of the following countries will experience a major increment in energy demand?
a) USA
b) France
c) UK
d) China
Answer: d
Clarification: China will experience a major increment in energy demand. China is the most populated country in the world and its population is expected to increase. Moreover, China is a developing country. Though the Chinese government have taken steps to curb the growth, catering to the demands of the existing population is extremely challenging.

9. Despite significant investments in renewable sector, why are fossil fuels still used?
a) Because of logistic, structural and operational issues
b) Because people do not trust the renewable sector
c) Because fossil fuels are cheap
d) Because global warming is a hoax
Answer: a
Clarification: Despite significant investments in renewable energy sector, fossil fuels still dominate and supply 80% of world’s energy. This is mainly because of logistic, structural and operational issues. For instance, it is a financial challenge to replace the existing machinery.

10. Which of the following institutions publish energy data?
a) NASA
b) International Energy Agency (IEA)
c) ISRO
d) Microsoft
Answer: b
Clarification: Institutions such as the International Energy Agency (IEA), the U.S. Energy Information Administration (EIA) and the European Environment Agency (EEA) publish energy data. NASA and ISRO are space agencies. Microsoft is a for-profit software solution company.

11. What is total primary energy supply?
a) Total energy produced and used by humanity
b) Total energy consumed by humanity
c) Sum of energy production minus storage changes
d) Sum of energy production including storage changes
Answer: c
Clarification: Total primary energy supply (TPES) is the sum of energy production minus storage changes. TPES can be used as an estimator for energy consumption as yearly changes in energy storage are negligible.

12. What is the unit of total primary energy supply?
a) Watts
b) Joules
c) Newtons
d) Watt-hours
Answer: d
Clarification: Total primary energy supply (TPES) is measured in watt-hours (Wh). In 2013, IEA estimated that TPES was 157.5 petawatt hours. Watts is the unit of power. Joules is the unit of energy. Newtons is the unit of force.

13. What was the growth in energy demand in the year 2018 as stated by IEA?
a) 2.3%
b) 1.3%
c) 1%
d) 0.5%
Answer: a
Clarification: In 2018, the growth in energy demand was 2.3%. This was remarkable because until then the average annual growth rate was 1.3%. Emissions also increase as the demand for energy increases.

14. World energy consumption is a power source metric of civilization.
a) True
b) False
Answer: a
Clarification: World energy consumption is a power source metric of civilization. It has deep implications for humanity in terms of policy making and political decisions.

15. It estimated that the world energy consumption will grow by 50% between 2018 and 2050.
a) True
b) False
Answer: a
Clarification: It is estimated that the world energy consumption will grow by 50% between 2018 and 2050. Many renowned energy organizations like IEA and EIA agree with this estimate. This is to cater to the demands of growing population.

Solar Energy Multiple Choice Questions on “Solar Collectors – 1”.

1. What is a solar collector?
a) A system to collect heat by absorbing sunlight
b) A system to collect rainwater using sunlight
c) A system to collect electricity by using sunlight
d) A device to reflect sunlight back
Answer: a
Clarification: A solar collector is a system to collect heat by absorbing sunlight and use it for various applications. It is neither a system to collect rainwater nor electricity. However, it could be used to perform such processes.

2. What is aperture area in a solar collector?
a) Area of the system
b) Area in the receiver that receives the solar radiation
c) Area occupied by the system after installation
d) Cross-sectional area of the receiver
Answer: b
Clarification: Aperture area of a receiver is that area which receives the solar radiation. It need not be same as the entire size of the receiver. It is not same as the area occupied by the system after installation.

3. Aperture area of a solar collector is roughly equal to _______
a) Coolant area
b) Generator area
c) Absorber area
d) System area
Answer: c
Clarification: In a solar collector, the aperture area is approximately equal to absorber area. This enables absorption of (almost) all the sunlight that is incident on the aperture area.

4. What are the components of a flat plate collector?
a) Flat box, a plate with reflective coating and fluid circulation passageways, an opaque cover, a circulating fluid
b) Flat box, a dark coloured plate with fluid circulation passageways, an opaque, a circulating fluid
c) Flat box, a dark coloured plate with fluid circulation passageways, a transparent cover
d) Flat box, a dark coloured plate fluid circulation passageways, a transparent cover, a circulating fluid
Answer: d
Clarification: A flat plate solar collector consists of various components. Firstly, it consists of a flat box or an enclosure to hold the entire setup. A dark coloured plate is fitted with fluid circulation passageways and transparent cover. Finally, a circulating fluid which flows through the entire setup.

5. Why is a transparent cover used in a flat plate collector?
a) To maximize transmission of the incident sunlight into the box
b) To minimize transmission of the incident sunlight into the box
c) To entirely reflect the incident sunlight back
d) To ensure partial transmission of the incident sunlight into the box
Answer: a
Clarification: A transparent cover is used in a flat plate collector. This is because it maximizes the transmission of the incident sunlight into the box thereby collecting maximum sunlight for thermal energy.

6. Which of the following is generally used as circulating fluid in tropical and sub-tropical climates?
a) A mixture of ethylene glycol and water
b) Water
c) A mixture of propylene glycol and water
d) Glycerol
Answer: b
Clarification: Water is used as circulating fluid in tropical and sub-tropical climates. This is because it has good properties as a coolant. A mixture of water with ethylene glycol or glycerol or propylene glycol is not used as coolant in tropical and sub-tropical climates.

7. Which of the following is generally used as circulating fluid in freezing climates?
a) Liquid carbon dioxide
b) Water
c) A mixture of propylene glycol and water
d) Liquid nitrogen
Answer: c
Clarification: In freezing climates, antifreeze solution like a mixture of water with propylene glycol or ethylene glycol or glycerol is used as coolants. Liquid carbon dioxide, water and liquid nitrogen are not used as coolants in freezing climates.

8. Why are antifreeze solutions (antifreeze agents with water) used as coolants in freezing climates?
a) To increase boiling point of water
b) To decrease boiling point of water
c) To increase freezing point of water
d) To decrease freezing point water
Answer: d
Clarification: Antifreeze solution is used as coolants in freezing climates. This is because they decrease the freezing point of water thereby preventing it from solidifying into ice.

9. Adding antifreeze agents to water _________
a) increases its durability as coolant
b) decreases its durability as coolant
c) turns water into a coolant
d) prevents water from acting as a coolant
Answer: a
Clarification: Adding antifreeze agents to water increases its durability as coolant. This is because it depresses the freezing point of water and prevents it from becoming ice.

10. Which of the following is a circulating fluid in evacuated flat-plate solar collectors?
a) Water
b) Steam
c) Nitrogen
d) Hydrogen
Answer: b
Clarification: Evacuated flat-plate solar collectors are a more recent technology. It uses steam as its circulating fluid. Nitrogen and hydrogen are not used as circulating fluid. Water is mainly used in flat-plat collectors.

11. Evacuated flat-plate solar collectors are a type of _______
a) concentrating collectors
b) photovoltaic technology
c) non-concentrating collectors
d) solar stills
Answer: c
Clarification: Evacuated flat-plate solar collectors are a type of non-concentrating collectors. Solar stills and photovoltaic technology are not solar collectors.

12. Which of the following are used as absorbers in evacuated-tube solar collectors?
a) Carbon tubes
b) Wooden or metallic tubes
c) Plastic or glass tubes
d) Metallic or glass tubes
Answer: d
Clarification: Metallic or glass tubes are used as absorbers in evacuated-tube solar collectors. Wood and plastic are thermal insulators and hence, cannot be used to create passageways for the heat carrying circulating fluid.

13. What is a heat pipe?
a) A heat-transfer device
b) A pipe made of heat
c) A pipe that consists of heat
d) A heat pumping device
Answer: a
Clarification: A heat pipe is a heat-transfer device. It combines the principles of thermal conductivity and phase transition to effectively transfer heat between two solid interfaces.

14. For better efficiency, solar collectors do not coat their transparent cover with an anti-reflective coating.
a) True
b) False
Answer: b
Clarification: For better efficiency, solar collectors coat their transparent cover with an anti-reflective coating. The anti-reflective coating reduces the amount of reflection dramatically. Thus, the amount of sunlight collected is increased.

15. Evacuated tube solar collectors use a glass tube to surround absorber with high vacuum.
a) True
b) False
Answer: a
Clarification: Evacuated tube solar collectors use a glass tube to surround absorber with high vacuum. This is used to effectively resist atmospheric pressure and reduce conductive and convective losses.

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Wind Energy Multiple Choice Questions & on “Nature of Winds”.

1. What is the definition of wind?
a) Air in net motion
b) Air in motion
c) Gas molecules in random motion
d) Stationary gas molecules

Answer: a
Clarification: Wind is better defined as air in net motion. On a microscopic level, gas molecules are always in a random motion and are not visible to the naked eye. In fact, motion of individual gas molecules cannot be sensed by our senses. Thus, gas molecules are never stationary.

2. Which of the following involves studying the physics of wind flow?
a) Microbial fuel cells
b) Fluid dynamics
c) Combustion
d) Polymer science

Answer: b
Clarification: Fluid dynamics involves the studies of wind motion and its underlying physics. Fluids consists of both, liquids and gases. Hence, wind is also a fluid because it consists of gas molecules.

3. Which of the following best describes the motion of air on earth?
a) A two-dimensional vector
b) A one-dimensional vector
c) A three-dimensional vector
d) A four-dimensional vector

Answer: c
Clarification: The motion of air on earth is best described as a three-dimensional vector. It is also important to note that air motion is typically described and studied relative to earth’s rotation.

4. Which of the following are the three individual components/dimensions best used to describe air motion on earth?
a) A meridional component pointing south-to-north, a zonal component pointing north-to-east, a vertical upward component pointing from ground to sky
b) A zonal component pointing south-to-north, a meridional component pointing west-to-east and downward component pointing from sky to ground
c) A meridional component pointing north-to-south, a zonal component pointing east-to-south, a vertical upward component pointing from ground to sky
d) A meridional component pointing south-to-north, a zonal component pointing west-to-east, a vertical upward component pointing from ground to sky

Answer: d
Clarification: The three individual components that correspond to the three dimensions are – a meridional component pointing south-to-north, a zonal component pointing west-to-east and a vertical upward component pointing from ground to sky.

5. Which of the following devices indicate wind direction?
a) Weather vanes, windsocks
b) Multimeter, oscilloscope
c) Accelerometer
d) Wind’s direction cannot be measured

Answer: a
Clarification: The direction of wind is generally indicated by weather vanes, windsocks and balloons. Multimeters and oscilloscopes are electronic instruments used to measure voltage and current. Accelerometer is a device that measures a body’s acceleration.

6. What is geostrophic wind?
a) Wind generated due to disbalance between wind forces and Coriolis force
b) Wind generated due to balance between pressure gradient force and Coriolis force
c) A special wind generated from geothermal energy
d) Wind flowing in stratosphere

Answer: b
Clarification: Geostrophic wind is the wind generated due to balance between pressure gradient force and Coriolis force. It occurs above the atmospheric boundary layer (ABL).

7. What are eddies in wind?
a) Areas where the global wind blows opposite to that of the net direction of wind-motion
b) Areas where the local wind blows in the same direction as the net direction of wind-motion
c) Areas where the local wind blows opposite to that of the net direction of wind-motion
d) Areas where the local wind blows randomly to that of the net direction of wind-motion

Answer: c
Clarification: Eddies are small areas where the local wind blows opposite to that of the net direction of wind-motion for a short period of time. Eddies are always local in nature and do not occur globally.

8. The Coriolis force deflects the wind to the right in Northern Hemisphere until ______
a) equilibrium of forces is not achieved
b) gas molecules stop moving
c) water vapour evaporates
d) equilibrium of forces is achieved

Answer: d
Clarification: The Coriolis force deflects the wind to the right in Northern Hemisphere until an equilibrium is achieved. The equilibrium is between the pressure gradient of the wind and the Coriolis force.

9. Wind speed is measure by ______
a) anemometers
b) odometers
c) ammeter
d) weather vanes

Answer: a
Clarification: Anemometers are used to measure wind speeds. They are commonly used in weather stations. Odometers measure distance of a wheeled vehicle. Ammeters measure current and weather vanes are used to indicate the direction of wind.

10. What is wind speed?
a) Net molecular flux along the wind axis divided by the mean molecular number density
b) Molecular flux along the wind axis divided by the mean molecular number density
c) Net molecular flux along the wind axis divided by molecular number density
d) Molecular flux opposite the wind axis divided by the mean molecular number density

Answer: a
Clarification: Wind speed is defined as the net molecular flux along the wind axis divided by the mean molecular number density. Flux is the number of molecules crossing a unit area (square meter) in a unit time (second). Mean molecular number density is the number of molecules per cubic meter.