Sasurie College of Engineering

Department of Electrical and Electronics Engineering

QUESTION BANK
Sub Code/Name: ME 6701/ Power Plant Engineering
Year/Sem: III/ V
UNIT V- ENERGY, ECONOMIC AND ENVIRONMENTAL ISSUES OF POWER
PLANTS
Power tariff types, Load distribution parameters, load curve, Comparison of site
selection criteria, relative merits & demerits, Capital & Operating Cost of
different power plants. Pollution control technologies including Waste Disposal
Options for Coal and Nuclear Power Plants.
PART A (2 Marks)
1. What are types of tariffs?
(1) Flat demand rate
(2) Straight line meter rate
(3) Step meter rate
(4) Block rate tariff
(5) Two part tariff
(6) Three part tariff.
2. What is the significance of load curve?
Importance of Load Curve:
The Daily Load Curve gives the information of load on the power station during
different running hours of the day.
The number of units generation per day is found from the area under the daily
Load Curve.
Average load is found from the Load Curve.
Average load= [Area (KWh) under daily load curve/24 hours]
The maximum demand of the station on that day is found from the highest
point of the daily Load Curve.
The size and the number of generating units can be determined from the load
curve.
This Load Curve helps to determine the operation schedule of the station. In
that case when all the units or the less units needs to running is found.
3. List the various costs of power generation.
a. capital costs necessary to build the generator
b. fuel costs to actually produce electric power
4. Compare the site selection criteria of different power plants.
Land Availability
Seismic Stability
Floodplain
Weather
Existing Site Hazards
Existing Land Use
Restricted Air Space
Cultural Resources
Threatened and Endangered Species
Proximity to Public Access Areas
State/Local Environmental Requirements
Proximity to Class I Visibility Areas
Proximity to Tribal Lands
Access to Cooling Water

 Fuel Supply Environment

Access to Grid
Rights of Way
Transportation Options Available
Labor and Skills Availability
Cost and Economic Environment
5. What do you mean by the sources of pollution?
The main sources of atmospheric pollution may be summarized as follows:
(a) The combustion of fuels to produce energy for heating and power generation
both in the
domestic sector as well as in the industrial sector.
(b) The exhaust emissions from the transport vehicles that use petrol, or diesel
oil etc.
(c) Waste gases, dust and heat from many industrial sites including chemical
manufacturers,
electrical power generating stations etc.
6. What are the main objectives of tariff?
Like other commodities, electrical energy is also sold at such a rate so that it not
only returns the cost but also earns reasonable profit. Therefore, a tariff should
include the following items :
(i) Recovery of cost of producing electrical energy at the power station.
(ii) Recovery of cost on the capital investment in transmission and distribution
systems.
(iii) Recovery of cost of operation and maintenance of supply of electrical energy
e.g., metering equipment, billing etc.
(iv) A suitable profit on the capital investment.
7. What are the various types of power stations?
Power Station Base load & Peak load
- Base Load: is the unvarying load that occurs almost all the day on
the station (>)
- Peak Load: are the various peak demands over and above the base
load (<)

Meeting the Load: Interconnecting two power stations, the more efficient plant is
assigned the base load, while the less efficient one is assigned the peak load.
8. List the elements of fixed and operating costs.
There are two types of costs for any electrical instrument for that matter any
instrument.
Fixed Cost
Running Cost
Fixed Cost : Fixed cost can also be sometimes called as capital cost because it
is the cost involved to put the instrument in place here it is generator and other
power plant equipment. To build a 500 MW plant it roughly takes 2500 crores.
This amount is taken as capital cost to generate 500 MW of power.

This includes cost of equipment, cost for procurement of land , buildings ,

construction and erection costs, transportation and rehabilitation for displaced
people, living space for the employees of the plant etc.
Interest : The interest for the fixed cost also should be calculate and must be
considered as a part of fixed cost.
Depreciation : Depreciation is another aspect to be considered as a part of
fixed cost. When we buy a generator and use it for a long time, the efficiency
falls due to degradation. The lower efficiency will result in high running costs and
it will uneconomical to run the station.
Running Cost : Running cost is the cost of the fuel which is used to generate
the electricity and maintenance costs for the plan equipment and operation
costs. The cost of the fuel is not always constant for a generator. It is not a linear
function. Cost per MW increases as the generation is increased.
The operations costs include salaries and wages to the employees and this cost
practically remains constant for a generation. This is taking under running costs.
Maintenance costs are the costs incurred in regular maintenance of machines.
This includes cleaning of all water tubes in case of thermal power plants and
generators bearings check and operations similar to this.
9. Define diversity factor.
It is defined as the ratio of the sum of the individual non-coincident maximum
loads of various subdivisions of the system to the maximum demand of the
complete system.
Diversity Factor = Sum of Individual Max. Demands
The diversity factor is always less than or equal to 1.
10. Enumerate the waste disposal options for nuclear power plants.
Nuclear Disposal:
Geological: burrowing nuclear waste into the ground to the point where it is out
of human reach
Reprocessing: the process involves taking waste and separating the useful
components from those that arent as useful.
Transmutation: It specifically involves converting a chemical element into
another less harmful one. Space Disposal: putting nuclear waste on a space
shuttle and launching the shuttle into space.
11. Give the relative merits and demerits of different power plants.
1. List down the wastes associated with nuclear power.
1. Gaseous effluents.
2. Uranium mine and mill tailings. Tailings are residues from uranium
mining .
3. Low-level wastes (LLW). These are classified as wastes that contain less
than 10 nCi
(nanocuries) per gram of transuranium contaminants
4. High-level wastes (HLW). These are generated in the reprocessing of spent
fuel. They contain essentially all the fission products and most of the
transuranium elements not separated during reprocessing. Such wastes are to be
disposed of carefully.
5. Spent fuel. This is unreprocessed spent fuel that is removed from the
reactor core after
Reaching its end-of-life core service.
12. Define Three-Part Tariff .
According to this tariff the customer pays some fixed
amount in addition to the charges for maximum demand and energy consumed.
The fixed amount to be charged depends upon the occasional increase in fuel
price, rise in wages of labour etc. It is expressed by the expression Y = DX + EZ
+ C.

13. Write the measures are being taken to control pollution and
improve the environment.
(1) Planting of planting trees/shrubs ;
(2) Public awareness campaigns;
(3) Setting up eco-clubs in schools;
(4) Development and protection of the Ridge area;
(5) Development of wildlife sanctuary ;
(6) Development of old lakes;
(7) 10 City Forest Sites have been identified by the Forest Department.
These will be
Developed by the Forest Department as Green Lungs for various
areas.
14. Mention the factors make pollution from vehicles.
Four factors make pollution from the vehicles more serious in developing
countries.
(1) Poor quality of vehicles creating more particulates and burning fuels
inefficiently.
(2) Lower quality of fuel being used leads to far greater quantities of pollutants.
(3) Concentration of motor vehicles in a few large cities
(4) Exposure of a larger percentage of population that lives and moves in the
open.
15. Enumerate the waste disposal options for nuclear power plants.
Storage is the number one solution for coal ash disposal largely because
involve more steps and
thus are more expensive than the landfill option.
16. What is meant by air pollution?
Air pollution may be defined as the presence of impurities in excessive quantity
and duration to cause adverse effects on plants, animals, human beings and
materials.
17. What are the main sources of air pollution?
Natural sources and
Man made or anthropogenic sources
18. List the types of air pollutants.
Particulate pollutants
Gaseous pollutants
19. What do you understand by suspended particulate?
Suspended particulate matter is a complex mixture of small and large particles
with size less than 100 varying origin and chemical composition. The largest
source
of particulate matter is coal-fired power plants, but auto and diesel exhaust are
also
prime contributors, especially along busy transportation corridors.
20. Write short note on radioactive property of hazardous waste.
In the spontaneous break down of the nucleus of an atom, mainly three types of
radioactive materials are found to be hazardous namely:
particles, particles, radiations.
The particle emission occurs mainly in radioactive isotope and the radiations
are the electron released from a radioactive nucleus. The radiations are
electromagnetic radiation traveling at speed of light.
21. How can you control the emission of nitrogen oxides? OR Explain
EGR method.
Since high temperature favors the production of nitrogen oxide, the emission
may

be controlled by lowering the combustion temperature. This can be achieved by

recirculating the exhaust gases, which will no longer burn. Hence it will not
produce
any heat if re-circulated and will quench the heat of the combustion gases. This
method is called Exhaust Gas Recirculation(EGR). The temperature in the
cylinder
ranges from 500oC and the end of compression stroke (before ignition) to about
3000oC after ignition, which produces nitrogen oxides. Hence to reduce the formation
of
nitrogen oxides the temperature must be maintained as low as 1300 oC which can
be
maintained by adopting EGR method.
22. What are the sources of hydrogen fluoride?
Hydrogen Fluoride is released by aluminium industry, chemical industries, textile
and fertilizer industries. HF affects the respiratory track, bone fluorisis, skin
burns,
and destroys the crops.
23. Write short note on incineration process used in managing
hazardous waste.
The incineration process is very complex and involves chemistry, physics and
thermodynamics. During this process, the bonds between the molecules break
and
free radicals are formed leading to violent reactions, and finally to harmless
products.
Some reactions are also speeded up by catalysts at high temperature.
24. Define green house effect.
The green house effect is a naturally occurring process that makes the earth
warmer by trapping more energy in the atmosphere. The green house gases
absorb
and hold heat from the sun, preventing it from escaping back into the space.
25. Define global warming
Global warming is defined as the increase in temperature of the earth, which
causes more changes in climate.
26. What are the effects of global warming?
More heat waves
Expansion of desert area
Natural fires in forest land
More evaporation of water from oceans and water bodies
Melting of ice caps in artic and Antarctica regions
More cloud formation in the atmosphere
Rise in sea level
More drought
More impacts on plants, animals and humans.
27. When is a waste said to be hazardous?
A waste is said to be hazardous if it posses one or the more of the following
characteristics
Toxicity
Reactivity
Ignitability
Radioactivity
Corrosivity
28. What are major vehicle pollutants?

The major pollutants due to vehicles are

Carbon monoxide
Hydrocarbons
Oxides of nitrogen
Lead components and
Suspended particulate matter.
29. Write short note on nitrification / denitrification
An approach to nitrogen control utilizes aerobic bacteria to convert
ammonia(NH4+) to (NO2-) which is nitrification followed by an anaerobic stage in
which different bacteria converts nitrates to nitrogen gas(N 2) which is
denitrification.
The overall process is referred to as nitrification / denitrification.
30. Explain drying and dewatering.
The shredded waste material is pre-dried to decrease its weight by removing the
amount of moisture. If there is any need for incineration of sludge from
treatment
plants, then dewatering is essential.
31. What are the two main classifications in sources of radioactive
pollution?
Natural sources
Man-made sources
32. What is half-life of a radioactive substance?
The half-life of a radioactive substance is defined as the time taken for decaying
half of the material present.
33. What are the factors to which the effect of radioactive pollutants
depend on?
Duration of exposure to the radiation
Strength of the radiation
Half life period of the radioactive pollutant
Rate of diffusion of the pollutant
Environmental conditions

34. What is DRE?

DRE refers to the destruction and removal efficiency that evaluates the
measurement of qualitative functioning of an incinerator. A DRE value of 99.99
indicates that one molecule of an organic compound is released in to the
atmosphere
for every 10,000 molecules of pollutant treated by the incinerator.
35. What is waste treatment?
Waste treatment technique or process change the physical,chemical and
biological
character of waste.
36. What are the objectives of waste treatment?
i)To recover the material or energy resources from the waste.
ii)To neutralise the waste.
iii)To reduce the volume of waste.
37. What is an clean technology?
Clean technology is an integrated preventive environmental and business
strategy
which uses fewer raw materials, less energy and generate less waste than an
existing

technology. It produces products and provide services at a higher efficiency

,increased profitability and reduces risk to the environment.
38. What are the advantages of clean technology?
i)It helps to use fewer raw materials and energy and generate less waste.
ii)It helps to ensure worker safety.
iii)It reduce the impacts for products along the entire life cycle from material
extraction to disposal.
39. What is disposal?
Disposal is the discharge, deposit, injection, dumping, spiling, leaking or
placing of waste in to or any land, water or air.
40. What are the elements of waste minimisation strategy?
a. Reduction at source
b. Recycle/Reuse
c. Treatment
d. Disposal.
41. What are the possible solutions of waste disposal?
i)Install a fume incinerator.
ii)Install a condenser to recover the solvent for reuse
42.What are the wastes associated with nuclear power?
1. Gaseous effluents. .
2. Uranium mine and mill tailings.
3. Low-level wastes (LLW).
4. High-level wastes (HLW).
5. Spent fuel.
43. What are the pollution materials due to coal power plant?
Sulfur dioxide (SO2), Nitrogen oxides (NOx, Particulate matter, Mercury.
44. Discuss the effect of power plant type on costs.
1. Fixed Cost and 2. Operational Cost. 3. INITIAL COST
45. What are the OPERATIONAL COSTS?
The elements that make up the operating expenditure of a power plant include
the following
(1) Cost of fuels.
(2) Labour cost.
(3) Cost of maintenance and repairs.
(4) Cost of stores (other than fuel).
(5) Supervision.
(6) Taxes.
46. Explain briefly the requirements of a tariff.
(1) It should be easier to understand.
(2) It should provide low rates for high consumption.
(3) It should encourage the consumers having high load factors.
(4) It should take into account maximum demand charges and energy charges.
(5) It should provide less charges for power connections than for lighting.
(6) It should avoid the complication of separate wiring and metering connections.
47.Define Flat Demand Rate.
It is based on the number of lamps installed and a fixed number of hours
of use per month or per year. The rate is expressed as a certain price per lamp or
per unit of demand (kW) of the consumer. This energy rate eliminates the use of
metering equipment. It is expressed by the expression.
48. Define Block Rate Tariff.
According to this tariff a certain price per units (kWh) is charged for all or any
part of block of each unit and for succeeding blocks of energy the corresponding
unit chargesdecrease.
It is expressed by the expression Y = E1Z1 + E2Z2 + E3Z3 + E4Z4 + .....

where E1, E2, E3.... are unit energy charges for energy blocks of magnitude Z1,
Zz, Zg,.... respectively.
49. Discuss the economic factors to be considered for plant selection.
(1) Location of power plant
(2) Availability of water in power plant
(3) Availability of labour nearer to power plant
(4) Land cost of power plant
(5) Low operating cost
(6) Low maintenance cost
(7) Low cost of energy generation
(8) Low capital cost
50. Define Demand factor .
The ratio of (a) the maximum real power consumed by a system to (b) the
maximum real power that would be consumed if the entire load connected to the
system were to be activated at the same time.
DF = max . demand of the consumer / connected load
For a consumer, the demand factor is the ratio of its max demand to the
connected load.
PART-B
1. Describe, what you understand by power plant economics? Explain
the fixed costs and operating costs of a power station.
2. Summarize the elements which contribute to the cost of the
electricity? And how can the cost power generation be reduced?
3. Discuss the cost of electrical generation? What are the various types
of cost associated with power generation?
4. Define tariff? Discuss and compare various tariff used in practice.
5. i) Explain the term depreciation and discuss various methods of
calculating the depreciation of an electrical plant.
ii) Explain load curves and load duration curves? Discuss their utility in
the economics of generation.
6. A generating stations as a maximum demand (MD) of 15 MW and the
daily load curve on the station is as follows, 10pm to 05 am 2500 KW
01pm to 04pm 10000KW 05am to 07 am 3000KW 04pm to 06pm
12000KW ,07pm to 11am 9000KW 06 pm to 08pm 15000KW 11am to
01pm 6000KW 08pm to 10pm 5000KW Determine the size and the
number of generator units, plant load factor, plant capacity factor, use
factor and reserve capacity of plant.
7. Explain the pollution control technologies including waste disposal
options for coal power plant.
8. i) Illustrate the short note on nuclear waste disposal.
ii) A central power station has annual factors as follows. Load factor =
60%, capacity factor = 40% and use factor = 45%.power station has a
maximum demand of 15000 KW. Determine the annual energy
production, reserve capacity over and above peak load hours per year
not in service.
9. Generalize in detail Capital & Operating Cost of different power
plants.
10. i) List and discuss any 4 power tariff structure adopted by
TANGEDCO.
ii) Name the pollution control technologies adopted in thermal power
plants and describe anyone.
11. Explain the pollution control technologies including waste disposal
options for nuclear power plant.

12. i) Name and elaborate on the elements that contribute to the cost
of electricity.
ii) Brief: Base load, peak load and average load of a thermal power
plant.
13. Explain the pollution due to nuclear power plant.
14. Explain the methods to reduce the pollution.
15. Enumerate the following:
(i) Load factor (LF)
(ii) Plant Use Factor (Puf):
(iii)Demand factor (DF)
16. Discuss the effect of power plant type on costs.
17. Explain the requirements of a tariff. Discuss the various types of
tariffs.
18. Explain load curve.
19. The maximum (peak) load on a thermal power plant of 60 MW
capacity is 50 MW at an annual load factor of 50%. The loads having
maximum demands of 25 MW, 20 MW, 8 MW and, 5 MW
are connected to the power station.
Determine: (a) Average load on power station (b) Energy generated per
year (c) Demand factor
(d) Diversity factor.
Solution.
(a) Load factor = Average load/Maximum demand
Average load = 0.5 50 = 25 MW
(b) E = Energy generated per year
= Average load 8760 = 219 106 kWh.
(c) Demand factor = Maximum demand/Connected load = 50/(25 + 20 + 8 + 5)
= 0.86
(d) Diversity factor = M1/M2
Where M1 = Sum of individual maximum demands = 25 + 20 + 8 + 5 = 58 MW
M2 = Simultaneous maximum demand = 50 MW
Diversity factor =58/50= 1.16.
20. A new factory having a minimum demand of 100 kW and a load
factor of 25% is comparing two power supply agencies.
(a) Public supply tariff is Rs. 40 per kW of maximum demand plus 2
paise per kWh.
Capital cost = Rs. 70,000
Interest and depreciation = 10%
(b) Private oil engine generating station.
Capital Cost = Rs. 250,000
Fuel consumption = 0.3 kg per kWh
Cost of fuel = Rs. 70 per tonne
Wages = 0.4 paise per kWh
Maintenance cost = 0.3 paise per kWh
Interest and depreciation = 15%.
Solution. Load factor = Average load/Maximum demand
Average load = Load factor Maximum demand = 0.25 700 = 175 kW.
Energy consumed per year = 175 8760 = 153.3 104 kWh.
(a) Public Supply
Maximum demand charges per year = 40 700 = Rs. 28,000.
Energy charge per year =(2/100) 153.3 104 = 30,660
Interest and depreciation =(10/100) 70,000 = Rs. 7,000.
Total cost = Rs. [28,000 + 30,660 + 7,000] = Rs. 65,660
Energy cost per kWh = (65,660/153.3x104)x100=429 paise

(b) Private oil engine generating station

Fuel consumption =((0.3 x 153.3 x104 )= 460 tonnes
Cost of fuel = 460 70 = Rs. 32,000
Cost of wages and maintenance= {(0.4 + 0.3)100} 153.3 104 = Rs. 10,731.
Interest and depreciation =(15/100) 250,000 = Rs. 37,500
Total cost = Rs. [33,203 + 10,731 + 37,500]= Rs. 80,431
Energy cost per kWh=(80,431/153.3 x104) 100 = 5.2 paise.
21. Discuss in detail the economic factors to be considered for plant
selection.