UGC NET Environmental Science Unit-V: Energy and Environment Syllabus

Unit-V: Energy and Environment syllabus — full chapter and topic list

Expand any chapter to see its topics and sub-topics. This is the whole examinable outline for Unit-V: Energy and Environment in UGC NET Environmental Science, not a summary of it.

1. 1

   Sun as a Source of Energy

   1 topic

   • Solar Radiation and Its Spectral Characteristics
2. 2

   Fossil Fuels

   9 topics

   • Classification
   • Composition
   • Physico-chemical Characteristics
   • Energy Content of Coal, Petroleum, and Natural Gas
   • Shale Oil
   • Coal Bed Methane
   • Gas Hydrates
   • Gross-Calorific Value
   • Net-Calorific Value
3. 3

   Principles of Generation of Energy from Various Sources

   6 topics

   • Hydro-power
   • Tidal Energy
   • Ocean Thermal Energy Conversion
   • Wind Power
   • Geothermal Energy
   • Solar Energy
     • Solar Collectors
     • Photo-voltaic Modules
     • Solar Ponds
4. 4

   Nuclear Energy

   3 topics

   • Fission and Fusion
   • Nuclear Fuels
   • Nuclear Reactor – Principles and Types
5. 5

   Bioenergy

   1 topic

   • Methods to Produce Energy from Biomass
6. 6

   Environmental Implications of Energy Use

   4 topics

   • Energy Use Pattern in India and the World
   • Emissions of CO2 in Developed and Developing Countries including India
   • Radiative Forcing and Global Warming
   • Impacts of Large Scale Exploitation of Solar, Wind, Hydro, and Nuclear Energy Sources

Unit-V: Energy and Environment flashcards for UGC NET Environmental Science

25 of 50 cards from the Unit-V: Energy and Environment deck — real questions with worked answers.

1. What is the approximate value of the solar constant, and what does it represent?

   About 1361-1367 W/m2 (commonly ~1.36 kW/m2). It is the solar radiation received per unit area on a surface perpendicular to the Sun's rays at the mean Earth-Sun distance, just outside the atmosphere.

2. How is incoming solar radiation distributed across the spectrum by wavelength?

   Roughly 8-9% ultraviolet (<0.4 micrometre), ~46-47% visible (0.4-0.7 micrometre), and ~45-46% infrared (>0.7 micrometre). The Sun radiates approximately as a black body at ~5800 K, peaking in the visible (~0.5 micrometre).

3. State Wien's displacement law and the peak wavelength of solar emission.

   Wien's law: lambda(max) = b/T, where b = 2.898 x 10^-3 m.K. For the Sun (~5800 K) the peak is near 0.50 micrometre (visible green); for Earth (~288 K) it is near 10 micrometre (infrared).

4. Name the three main fossil fuels and the rank classification of coal from lowest to highest grade.

   Fossil fuels: coal, petroleum (crude oil), and natural gas. Coal ranks (low to high): peat -> lignite (brown coal) -> sub-bituminous -> bituminous -> anthracite. Higher rank means more carbon, less moisture/volatiles, and higher calorific value.

5. What is the typical carbon content and calorific value range of anthracite versus lignite?

   Anthracite: ~86-98% fixed carbon, high calorific value (~30-35 MJ/kg). Lignite: ~25-35% carbon, high moisture, low calorific value (~10-20 MJ/kg).

6. What is proximate analysis of coal, and what four components does it measure?

   Proximate analysis determines coal quality by measuring moisture, volatile matter, fixed carbon, and ash content (expressed as percentages).

7. What does the ultimate (elemental) analysis of coal determine?

   It determines the elemental composition by weight: carbon, hydrogen, nitrogen, sulphur, and oxygen (CHNS-O), plus ash.

8. What is the approximate energy content (calorific value) of crude petroleum and natural gas?

   Crude petroleum: ~42-46 MJ/kg. Natural gas: ~50-55 MJ/kg (its main component methane has ~55.5 MJ/kg, the highest among fossil fuels).

9. What is the dominant chemical component of natural gas and its typical share?

   Methane (CH4), typically 70-90% (often ~85-95%) of natural gas, with smaller amounts of ethane, propane, butane, and impurities like CO2, N2 and H2S.

10. What is shale oil and how is it produced?

    Shale oil is unconventional petroleum. 'Oil shale' contains solid kerogen which is heated (pyrolysis/retorting at ~450-500 C) to produce synthetic crude. 'Tight oil' is liquid crude trapped in low-permeability shale, extracted by hydraulic fracturing (fracking) and horizontal drilling.

11. What is Coal Bed Methane (CBM)?

    CBM is natural gas (mainly methane) adsorbed onto the surface of coal seams. It is extracted by drilling wells and reducing reservoir pressure (often by dewatering), allowing methane to desorb and flow. It is a cleaner unconventional gas source.

12. What are gas hydrates (methane hydrates)?

    Gas hydrates are ice-like crystalline solids in which methane molecules are trapped within a cage of water molecules (clathrates). They form under high pressure and low temperature, found in deep ocean sediments and permafrost, representing a vast potential energy resource.

13. Define Gross Calorific Value (GCV) / Higher Heating Value.

    GCV (HHV) is the total heat released by completely burning a unit of fuel when the combustion products are cooled back to the initial temperature AND the water vapour formed is condensed to liquid, recovering its latent heat.

14. Define Net Calorific Value (NCV) / Lower Heating Value and how it relates to GCV.

    NCV (LHV) is the heat released when the water produced in combustion remains as vapour, so the latent heat of vaporization is NOT recovered. NCV = GCV - latent heat of the water formed; thus NCV < GCV.

15. Give the approximate relationship between NCV and GCV in terms of hydrogen content.

    NCV = GCV - 2.26 x (9 x H) approximately (MJ/kg), where H is the mass fraction of hydrogen; each kg of H produces ~9 kg of water and 2.26 MJ/kg is the latent heat of vaporization of water. Moisture in the fuel also reduces NCV.

16. What is hydropower and the basic formula for power output of a hydroelectric plant?

    Hydropower converts the energy of flowing/falling water into electricity. Power P = rho x g x Q x H x eta, where rho = water density (1000 kg/m3), g = 9.81 m/s2, Q = flow rate (m3/s), H = head (m), and eta = efficiency.

17. How is tidal energy generated and what are its two main technologies?

    Tidal energy harnesses the rise and fall of sea levels caused by gravitational pull of the Moon and Sun. Technologies: (1) tidal barrages/range schemes using the head difference between high and low tide to drive turbines, and (2) tidal stream/current turbines driven by tidal flow.

18. What is Ocean Thermal Energy Conversion (OTEC) and the temperature difference it requires?

    OTEC generates electricity using the temperature difference between warm surface seawater and cold deep seawater. It requires a gradient of at least ~20 C (~1000 m depth difference). Cycles include closed (working fluid like ammonia), open (flash-evaporated seawater), and hybrid.

19. What is the formula for power available in wind, and how does it depend on wind speed?

    P = (1/2) x rho x A x v^3, where rho = air density, A = swept area, v = wind speed. Power is proportional to the CUBE of wind speed, so doubling wind speed gives 8x the power.

20. State the Betz limit for wind turbines.

    The Betz limit is the maximum fraction of wind kinetic energy a turbine can extract: 16/27 = 0.593 (~59.3%). No wind turbine can convert more than ~59.3% of the wind's kinetic energy into mechanical energy.

21. What is geothermal energy and its main resource types?

    Geothermal energy is heat from the Earth's interior. Resource types: hydrothermal (hot water/steam reservoirs), geopressured, hot dry rock (enhanced geothermal systems), and magma. Used for electricity (dry steam, flash steam, binary cycle plants) and direct heating.

22. Name the main technologies for harnessing solar energy.

    (1) Solar photovoltaic (PV) - direct conversion of sunlight to electricity via semiconductors (photovoltaic effect); (2) Solar thermal - collecting heat for water heating or to drive turbines; and (3) Concentrated Solar Power (CSP) using mirrors/lenses to focus sunlight.

23. What is the photovoltaic effect?

    The photovoltaic effect is the generation of voltage and electric current in a semiconductor (e.g. silicon p-n junction) when exposed to light: absorbed photons excite electrons across the band gap, creating electron-hole pairs that are separated to produce a DC current.

24. Distinguish nuclear fission from nuclear fusion.

    Fission: a heavy nucleus (e.g. U-235) splits into lighter nuclei, releasing energy and neutrons. Fusion: light nuclei (e.g. deuterium + tritium) combine to form a heavier nucleus (helium), releasing energy. Fusion releases more energy per unit mass and powers the Sun.

25. Write a representative nuclear fission reaction of Uranium-235.

    n + U-235 -> (U-236*) -> e.g. Ba-141 + Kr-92 + 3 neutrons + ~200 MeV energy. The released neutrons sustain a chain reaction.

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