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Chapter: Mechanical and Electrical : Power Plant Engineering : Power From Renewable Energy

Important Questions and Answers: Power From Renewable Energy

Mechanical and Electrical - Power Plant Engineering - Power From Renewable Energy

1. Define Tide?



The periodic rise and fall of the water level of sea which are carried by the action of sun and moon on water of the earth is called the tide.


2. In which system the power is Intermittently generated?

In a single basin arrangement power can be generated only intermittently.


3. What are the consistencies ‘Solar  farm’ndolar‘Stowaer’?



The solar farm consists of a whole field covered with parabolic trough concentrators and a ‘solar tower’consists of a central receiver on a tower and a whole field of tracking.


4. Define See beck effect?



‚If two dissimilar materials are joined to form a loop and the two junctions maintained at different temperatures, an e.m.f. will be set up around the loop‛.is is calledTh Seeback effect.


5. What is working principle of thermionic?


A thermionic converter works because of the phenomenon of ‘thermionic emission’.


6. What is Photo voltaic effect?



‘Photovoltaic effect’is defined as the generation of an electromotive force as a result of absorption of ionizing radiation.


7. Write a short notes on MHD –generator?



‘MHD generator’is a device which converts heat energy of a fuel directly into electrical energy without a conventional electric generator.


8. Write a short notes on Fuel cell?



A fuel‘ cell’isanelectrochemical device in which the chemical energy of a conventional fuel is converted directly and efficiently into low voltage, direct current electrical energy.


9. List the non –conventional energy sources?


The various non-conventional energy sources are as follows:

·        Solar energy

·        Wind energy

·        Energy from biomass and biogas

·        Ocean thermal energy conversion

·        Tidal energy

·        Geothermal energy

·        Hydrogen energy

·        Fuel cells

·        Magneto-hydrodynamics generator

·        Thermionic converter

·        Thermo-electric power.

10. Write the advantages of non –conventional Energy sources?


Advantages of non-conventional energy sources:


The leading advantages of non-conventional energy sources are:

1.     They do not pollute the atmosphere

2.     They are available in large quantities.

3.     They are well suited for decentralized use.


11.            Write the characteristic’sof wind energy?


1.     Wind-power systems do not pollute the atmosphere.

2.     Fuel provision and transport are not required in wind-power systems.

3.     Wind energy is a renewable source of energy.


4.     Wind energy when produced on small scale is cheaper, but competitive with conventional power generating systems when produced on a large scale.


Wind energy entails following short comings/problems:

1.     It is fluctuating in nature.

2.     Due to its irregularity it needs storage devices.

3.     Wind power generating systems produce ample noise.



12.          What are the types of wind mills?


1.     Multiple blade type

2.     Savonius type

3.     Darrieus type


13.            Write the types of wind machines?


1.     Horizontal axis wind machines

2.     Vertical axis wind machines


14.            Write the classification of Tidal power plants?


1.     Single Basin arrangement.

2.     Double Basin arrangement.



15.            What are the advantages and limitation of Tidal power generation? Advantages:


1.     Tidal power is completely independent of the precipitation (rain) and its uncertainty besides being inexhaustible.

2.     Large area of valuable land is not required.


3.     When a tidal power plant works in combination with thermal or hydro-electric system peak power demand can be effectively met with.


4.     Tidal power generation is free from pollution.




1.     Due to variation in tidal range the output is not uniform.


2.     Since the turbines have to work on a wide range of head variation (due to variable tidal range) the plant efficiency is affected.


3.     There is a fear of machinery being corroded due to corrosive sea water.

4.     It is difficult to carry out construction in sea.

5.     As compared to other sources of energy, the tidal power plant is costly.

6.     Sedimentation and silteration of basins are the problems associated with tidal power plants.


7.     The power transmission cost is high because the tidal power plants are located away from load centres.


The first commercial tidal power station in the World was constructed in France in 1965 across the mouth of La Rance Estuary. It has a high capacity of 240 MW. The average tidal range at La Rance is 8.4 m and the dam built across the estuary encloses an area of 22 km2.


16.            Write the advantages of MHD systems?


1.     More reliable since there are no moving parts.


2.     In MHD system the efficiency can be about 50% (still higher expected) as compared to less than 40% for most efficient steam plants.


3.     Power produced is free of pollution.

4.     As soon as it is started it can reach the full power level.

5.     The size of plant is considerably smaller than conventional fossil fuel plants.

6.     Less overall operational cost.

7.     The capital cost of MHD plants is comparable to those of conventional steam plants.

8.     Better utilization of fuel.

9.     Suitable for peak power generation and emergency service.


17.            Write the advantages and disadvantages of fuel cell?




1.     Conversion efficiencies are very high.

2.     Require little attention and less maintenance.


3.     Can be installed near the use point, thus reducing electrical transmission requirements and accompanying losses.


4.     Fuel cell does not make any noise.


5.     A little time is needed to go into operation.

6.     Space requirement considerably less in comparison to conventional power plants.



1.     High initial cost

2.     Low service life.


18.            Write the application of fuel cell?


The application of fuel cell relate to:


1.     Domestic use.

2.     Automotive vehicles

3.     Central power stations.

4.     Special applications.



19.            Write the advantages of OTEC?


1.     Ocean is an infinite heat reservoir which receives solar incidence throughout the year.

2.     Energy is freely available


20.            Write the disadvantages of OTEC?



1.     Efficiency is very low, about 2.5%, as compared to 30 - 40% efficiency for conventional power plants.


2.     Capital cost is very high


21.            Define –Tidal power plant?



The tidal power plants are generally classified on the basis of the number of basins used for power generations. They are further subdivided as one-way or two-way system as per the cycle of operation for power generation.


22. Define –Renewable sources of energy?



Renewable sources of energy are continuously produced in nature, and they will not get exhausted eventually in future.


23. Define –Non-renewable source of energy?



Non-renewable sources of energy will get exhausted eventually in future. Example: Energy from fossil fuels.


24. Mention some conventional sources?


Fossil fuels, hydel energy and nuclear energy.


25. Mention some Non-conventional sources?



Solar energy, wind energy, tidal energy, ocean thermal energy, geothermal energy and biomass.


26. What are the 3 –mayor energy sources?



The energy sources available can also be classified into three major types based on the yield of net energy. They are:




i) Primary energy sources,

ii) Secondary energy sources,

iii)            Supplementary energy sources.


27.            What are the five general categories of geothermal sources?


The following five general categories of geothermal sources have been identified.


1.     Hydrothermal convective systems

·         Vapour –dominated or dry steam fields.

·         Liquid –dominated system or wet steam fields.


·         Hot –water fields.

2.     Geopressure resources.

3.     Petro-thermal or hot dry rocks (HDR)

4.     Magma resources

5.     Valcanoes.


28.            Write the application of geothermal energy?


The following are the three main applications of the steam and hot water from the wet geothermal reservoirs:


1.     Generation of electric power.

2.     Space heating for buildings.

3.     Industrial process heat.

The major benefit of geothermal energy is its varied application and versatility.


29. What are the Advantages and disadvantages of Geothermal Energy over other Energy forms?


Advantages of geothermal process:


1.     Geothermal energy is cheaper.

2.     It is versatile in its use.

3.     It is the least polluting as compared to other conventional energy sources.

4.     It is amenable for multiple uses from a single resources

5.     Geothermal power plants have the highest annual load factors of 85 percent to 90 per cent compared to 45 per cent to 50 per cent for fossil fuel plants.


6.     It delivers greater amount of net energy from its system as compared to other alternative or conventional systems.


7.     Geothermal energy from the earth’sinterior is almost as inexhaustible as solar or wind energy, so long as its sources are actively sought and economically tapped.






1.     Low overall power production efficiency (about 15% as compared to 35% to 40% for fossil fuel plants).


2.     Drilling operation is noisy.

3.     Large areas are needed for exploitation of geo-thermal energy.


5.     The withdrawal of large amounts of steam or water from a hydro-thermal reservoir may result in surface subsidence or settlement.


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