Non Conventional Methods of Power Generation Interview Questions and Answers:

1. What are renewable and non-renewable energy resources ?

Ans. Renewable energy resources are those resources which can be used to produce energy again and again e.g., hydro energy, solar energy, tidal energy, geothermal energy etc. Non-renewable energy resources are those sources which cannot be replenished once they are used e.g., coal, oil, gas etc.

2. What are conventional and non-conventional energy resources ?

Ans. The fossil fuels (i.e., coal, petroleum and natural gas), hydro power and nuclear fuels fall under the category of conventional energy resources. Conventional energy resources are used conventionally and can be stored. The alternative of conventional energy resources are known as non-conventional energy resource. The non-conventional energy resources cannot be easily stored. Solar energy, wind energy, tidal energy, geothermal energy, ocean thermal energy, bio energy fall under the category of non-conventional energy resources.

3. What is MHD power generation ?

Ans. MHD power generation is the production of electric power utilizing a high temperature conducting plasma moving through an intense magnetic field. It is a direct heat-to-­electricity conversion technique based on Faraday’s laws of electromagnetic induction.

4. How are MHD systems classified ?

Ans. MHD systems may be classified as (i) open cycle systems and (ii) closed cycle systems. In an open cycle system, the working fluid after doing useful work (generating electrical energy) is discharged to the atmosphere through a stack while in a closed cycle system the working fluid is recycled to the heat source and thus used again and again. The operation of MHD generators directly on combustion products is an open cycle system using air as working fluid. In closed cycle systems gases used on the working fluid are helium or argon.

5. Whether power generated by MHD systems is ac or dc ?

Ans. The power generated by MHD system is dc which can be converted into ac by using an inverter.

6. What are the different factors in MHD generation that influence the output power ?

Ans. There are three parameters which govern the power output, for constant plate area and spacing and these parameters are the gas velocity, flux density and gaseous conductivity. The power output varies as (i) square of flux density, (ii) square of gas velocity and (iii) directly as the gaseous conductivity i.e., P α B2; P α v2 and P α σ.

7. What is basic difference between thermoelectric power generator and thermionic converter ?

Ans. The thermoelectric power generator is a device which directly converts heat energy into electrical energy and its working is based upon Seebeck thermoelectric effect while a thermionic converter transforms heat energy directly into electrical energy by utilizing thermionic emission.

8. What are the main drawbacks of thermoelectric generators ?

Ans. The main drawbacks of thermoelectric generators are high cost, low efficiency and low output.

9. What is solar cell ?

Ans. Solar cell is a device which directly converts incident solar radiation into electric current. It is based on photovoltaic energy conversion phenomenon and that is why it is also called photovoltaic cell.

10. What is the principle of operation of a solar cell ?

Ans. The solar cell operate on the principle of photovoltaic effect, which is a process of generating emf as a result of absorption of ionizing radiation.

11. What are the different types of solar cells ?

Ans. According to type of crystal, the solar cells are of three types:

  1. Monocrystalline silicon solar cells (band gap 1.12 eV)
  2. Polycrystalline silicon solar cells (band gap 1.12 eV)
  3. Thin film or amorphous silicon solar cells (band gap 1.75 eV)

12. Where are photovoltaic systems used ?

Ans. PV systems are best suited to rural areas and are used for (i) pumping water for drinking and irrigation, (ii) street lighting, (iii) rural telephone exchange operation, (iv) battery charging, (v) radio beacons for ship navigation at airports and in pocket calculators, watches, toys, electric fences etc.

13. What is fuel cell ?

Ans. A fuel cell is an electrochemical cell that converts chemical energy into electrical energy without combustion. In fuel cells, the chemical energy of reactants is converted into electrical energy as an isothermal process.

14. What are the advantages of fuel cells ?

Ans. The advantages of fuel cells are: (i) high efficiency (about 40%), (ii) simple and safe, (iii) noiseless operation and little maintenance due to absence of moving parts, (iv) pollution free, (v) compact, lighter and smaller and (vi) water bi-product of reaction.

15. Where are fuel cells used ?

Ans. Fuel cells can he used in vehicles, submarine, spacecrafts, locomotives and defense etc.

16. What is solar energy ?

Ans. Solar radiation in the form of electromagnetic radiation emitted by the sun is called the solar energy and this energy can be converted to useful form of energy, such as heat and electricity by different technologies. Solar energy is an essentially inexhaustible source potentially capable of meeting significant portion of the world’s future energy needs with a minimum of adverse environmental consequences. Solar energy is the most promising of the unconventional energy resources. In shear size, it has the potential to supply all the energy requirements: electrical thermal process, and chemical, an even transportation fuel.

17. What is solar constant ?

Ans. The rate at which solar radiation strikes earth’s upper atmosphere is expressed as the solar constant. This is the average amount of energy received in a unit time on a unit area perpendicular to the sun’s direction at a mean distance of the earth from the sun (149,604,970 km).

18. What is solar collector and what are their types ?

Ans. A solar collector is a device that absorbs the incident solar radiation and converts into useful heat which is used for heating a collector fluid such as water, oil or air. The surface of a solar collector is designed for high absorption and low emission. Solar collectors can be classified as non-concentrating or flat-plate type and concentrating or focusing collectors.

In the non-concentrating type, the collector area (i.e., the area that intercept the solar radiation) is the same as the absorber area (i.e., the area absorbing the radiation). In these types, the whole solar panel absorbs the light. Concentrating collectors make use of optical systems in the form of reflectors or refractors to concentrate the energy of direct solar radiation on the absorbing surface. The reflectors may be flat mirrors or in the shape of a parabolic trough or paraboloidal dish concentrating solar collectors are employed to heat a working fluid for power cycles.

19. What are the important components of flat plate collectors ?

Ans. Flat plate collector consists of transparent cover, absorber plate, series of tubes and housing with thermal insulation.

20. Where are flat plate solar collectors used ?

Ans. Flat plate solar collectors are used for water heating, space heating and power generation.

21. What are the different types of solar thermal power plants ?

Ans. Solar thermal power plants are of two types: (i) solar distributed collector power plants and (ii) solar central receiving power plants.

22. What are solar power towers ?

Ans. A solar power tower is a large tower surrounded by tracking mirrors called heliostats. These mirrors align themselves and focus sunlight on the receiver at the top of tower. The receiver collects the sun’s heat in a heat transfer fluid, which is used to produce steam for a conventional steam turbine located at the foot of tower for generation of electricity.

23. What are the main components of a solar chimney power plant ?

Ans. The main components of a solar chimney power plant are air heater of large area, a high chimney and air turbine.

24. What are solar ponds ?

Ans. Solar ponds are also called the solar salt ponds. A solar pond is a shallow body of water, about 1 m deep containing dissolved salts to generate a stable density gradient (fresh water on the top and denser salt water at bottom). Solar radiation passes through the upper layer to the bottom layer. The upper layer provides thermal insulation. Convection of water particles is prevented by the graded salt concentration. Temperature of water in upper layers is lower. Heat from the lower layers of water is exchanged with the working fluid in the heat exchanger.

25. What is a solar furnace ?

Ans. A solar furnace is a structure used to harness the rays of the sun in order to produce high temperatures. This is achieved by using a curved mirror (or an array of mirrors) acting as a parabolic reflector to concentrate light (Insolation) onto a focal point. The temperature of the focal point may reach up to 3,000°C, and this heat can be used to generate electricity, melt steel or make hydrogen fuel.

26. What is wind energy ? What causes wind to blow ?

Ans. Wind is air in motion. Winds are generated due to the atmospheric temperature difference caused by different areas getting different fluxes of sunlight. Air mass tends to move from hotter to the cooler regions, thereby generating winds.

27. Differentiate wind turbine and wind mill.

Ans. A wind turbine is a rotary device that extracts energy from the wind and converts into rotary mechanical energy. If the mechanical energy is used directly by machinery, such as for pumping water or grinding stones, the machine is called a windmill. In case the mechanical energy is instead converted into electricity, the machine is known as wind generator, wind turbine generator (WTG), wind power unit (WPU), wind energy converter (WEC) or aerogenerator.

28. Give the classification of wind turbines.

Ans. Basically, the wind turbines are of two types namely horizontal axis wind turbines, such as traditional farm windmills used for pumping water and the vertical axis wind turbines, such as the eggbeater-style Darrieus model, named offer its French inventer.

Most large modern wind turbines are horizontal axis turbines.

classification of wind turbines

In horizontal-axis turbines, the axis of rotation is horizontal with respect to ground (and roughly parallel to the wind stream) while in vertical-axis turbines, the axis of rotation is vertical with respect to ground (and roughly perpendicular to the wind stream).

29. What factors are taken into consideration in site selection for a wind plant ?

Ans. The main factors governing the site selection for a wind power plant are: (i) availability of wind, (ii) availability of land, (iii) accessibility to land and (iv) grid stability.

30. What are the advantages of generation of electricity from winds.

Ans. Wind energy is free, renewable resource, therefore, no matter how much is used today, there will still be the same supply in the future. Wind energy is also a source of clean, non-polluting electricity. Unlike conventional power plants, wind plants produce no air pollutants or greenhouse.

31. What is tidal power ?

Ans. Tidal power, also called the tidal energy, is a form of hydropower that converts the energy of tides into electricity or other useful forms.

32. Enumerate the advantages of tidal wave energy.

Ans. The main advantages of tidal wave energy are:

  • It is a free and renewable energy source.
  • It is a relatively pollution free.
  • Wave-power devices do not require large land masses like solar or wind.
  • After removal of power, the waves are in placid state.

33. What are the limitations of tidal wave energy ?

Ans. The limitations of total wave energy are: (i) corrosive sea­water, (ii) high capital investment, (iii) relative complicated energy conversion devices, (iv) very severe peak stresses in storms, (v) relative scarcity of accessibility sites of large wave activity and (vi) relatively unknown problems of biological growth of marine organisms.

34. What is geothermal energy ?

Ans. Geothermal energy is the earth’s natural heat available inside the earth. It originates from the original formation of the planet, from radioactive decay of minerals, from volcanic activity and from solar energy absorbed at the surface.

35. What are the various types of geothermal resources ?

Ans. Geothermal resources are of the following types:

(i) Hydrothermal, (ii) Geopressurised, (iii) Hard dry rock and (iv) Active volcanic vents and magna.

36. Classify the geothermal power plants.

Ans. There are basically four types of geothermal power plants, namely flashed steam plant, dry steam plant, binary power plant and hybrid power plant, which are in operation.

37. How do the geothermal power plants differ from conventional thermal power plants ?

Ans. The main differences between geothermal power plants and conventional power plants are:

  1. Geothermal power plants have smaller unit sizes (5, 10, 15 MW), whereas the conventional steam thermal power plants have large unit sizes (200, 500, 800 MW)
  2. A variety of systems are used in geothermal power plants for extraction of steam from geothermal energy resources.
  3. Geothermal power plants need a large flow of geothermal fluid (due to lesser temperature and pressure).
  4. Geothermal power plants are located on the geothermal field. It is not technically feasible to transport hot geothermal fluid over long distances due to the fact that there will be drop in pressure and temperature.

38. What is ocean thermal energy ?

Ans. The sun’s heat warms the surface water a lot more than the deep ocean water, and this temperature difference creates thermal energy.

39. How are ocean thermal energy plants classified ?

Ans. OTEC power plants may be classified on the basis of (i) location and (ii) cycle as below:

OTEC power plants

40. What are the problems that are associated with conversion of ocean thermal energy into electrical power ?

Ans. The technical difficulties associated with OTEC plants are:

  1. Degradation of heat exchanger performance by dissolved gases.
  2. Degradation of heat exchanger performance by microbial fouling.
  3. Improper sealing.

The evaporator, turbine and condenser operate in partial vacuum ranging from 3% to 1% atmospheric pressure. This poses a number of practical concerns. First, the system must be carefully sealed to avoid in-leakage of atmospheric air that can severely degrade or shut down operation.

41. What is biomass energy ?

Ans. Organic matter derived from biological organism (plants, algae, animals) are called biomass and the energy obtained from biomass is called biomass energy.

42. What are the biomass sources?

Ans. Biomass energy is derived from five distinct energy sources: (i) Garbage, (ii) Wood, (iii) Waste, (iv) Landfill gases, (v) Alcohol fuel.

43. Name the biomass conversion processes.

Ans. The processes used for the biomass conversion to energy or to fuels are: (i) Direct combustion (ii) Thermochemical conversion and (iii) Biochemical conversion.

44. Enumerate the applications of biomass energy.

Ans. The practical applications of biomass energy include (i) bio­gas plants, (ii) biomass briquetting, (iii) electricity generation and (iv) bio fuel etc.

45. What is gasifier and what are its applications ?

Ans. A gasifier is a system that converts solid biomass energy into combustible gas. Biomass is combusted by way of controlling the flow of air into the gasifier to convert the solid state into gas state, generating a combustible gas which mainly consists of H2, CO, CH4 and Cn Hm.

Applications of gasifier are heat generation, water pumping and electricity generation.