hydropower

5/20/2018 Hydropower

1/148

Chapter 1 1

1

1.1

1.1.1

Power is the rate of energy supply/consumption/demand. It is represented by P and Standard unit

of measurements in SI Unit is Watt.

( )sNmSJW

STime

mntDisplacemeNForce

Time

doneWork

STime

JEnergywattPower /1/11

)(

)(

)(

)()( ===

===

Energy can be in any form like Heat, Light, and Electricity

Energy in the form of Electricity is commonly termed as power and used widely all over the

world as it is easily transportable at high speed and convertible in to different form of energy

efficiently as per requirement. Electricity is taken as basic commodity as it is essential for running

communications and electronics equipments.

Energy is essential for anybody to perform work- day to day work (cooking, transportation,heating, cooling, lighting etc); Commercial activities (shopping complex, theatres, and cinema

halls) and Industrial use (production of goods, commodities, processing and refining etc)

Common units of Energy and Power measurements used in hydropower Engineering

Energy Power

Value Name Symbol Value Name Symbol

10 j Deca joule Daj 10 w Deca watt d w

10 j Hecta joule Hj 10 w Hecta watt h w

10 j Killo joule Kj 10 w Killo watt k w

10 j Mega joule MJ 10 w Mega watt Mw10 j Giga joule GJ 10 w Giga watt Gw

10 j Tera joule TJ 10 w Tera watt Tw

10 j Penta joule PJ 10 w Penta watt Pw

10 j Exa joule EJ 10 w Exa watt Ew

10 j Zetta joule ZJ 10 w Zetta watt Zw

1 HP = 735.5 W in Metric (MKS) system mostly used in Hydropower Engineering academic

courses but 1 HP = 746 W in FPS system not more used in academic exercise.

Hydropower engineering deals with the Electricity energy generated from the electro-mechanicalequipment (turbine-generator) and the unit of electricity energy measurement is KWh or Unit.

1 KWh or 1 Unit of electricity is the energy obtained from a heater (or other electrical appliances)

of 1 KW capacity in 1 hour.

JssJhrWhourKWKWh 510363600/100011000111 ====

Common Energy Conversion factorsUnit MJ KWh Ton of oil

Equivalent (TOE)Standardm

3gas

Raw OilBarel

Fuel wood(1 bhary)

1 MJ 1 0.278 0.0000236 0.025 0.000176 7.8E-051 KWh 3.6 1 0.000085 0.09 0.000635 0.000281 Ton of oil Equivalent (TOE) 42300 11750 1 1190 7.49 3.31

1 Standard m3 gas 40 11.11 0.00084 1 0.00629 0.002791 Raw Oil Barel 5650 1569 0.134 159 1 0.441 Fuel wood (1 bhary = 2.4m

3)

12800 3556 0.302 359 2.25 1

Source: 10 Yr 10000 MW Task force report 2009 (BS 2065)


2/148

Chapter 1 2

1.1.2

Sun is the main source of Energy in the form of solar radiation. Some of thatenergy has been preserved as fossil energy, some is directly or indirectly usable;

for example, via wind, hydro- or wave power.

The term solar constant is the amount of incoming solar electromagnetic radiationper unit area, measured on the outer surface of Earth's atmosphere, in a planeperpendicular to the rays.

The solar constant includes all types of solar radiation, not just visible light. It is measured by satellite to be roughly 1366 watts per square meter, though it

fluctuates by about 6.9% during a yearfrom 1412 W m2

in early January to1321

W m2

in early July, due to the Earth's varying distance from the sun by a few parts

per thousand from day to day.

For the whole Earth, with a area of 127,400,000 km2, the total energy rate is 174petawatts (1.74010

17W), plus or minus 3.5%. This value is the total rate of solar

energy received by the planet; about half, 89 PW, reaches the Earth's surface.

Primary Sources of Energy

Fossil fuels oil, natural gas and coal

Non Fossil fuels- namely nuclear power and renewable sources

Renewable sources- hydro, solar, wind, Geo-thermal, Tidal

Consumption of Energy and Power Situation in World

In 2008, total worldwide energy consumption was 474 exajoules (4741018J) with 80 to90 percent derived from the combustion of fossil fuels This is equivalent to an average

power consumption rate of 15 terawatts (1.5041013

W)

Economic Crisis from 2006-2009 the energy consumption has not been increased butslightly decreased

Rise of Energy consumption between 2005 and 2030 is approximately 41 percent.

This demand increase will take place in developing countries, where the present demand

of energy is low due to less or small economic activities which are expected to grow mostrapidly during its development process.


3/148

Chapter 1 3

Global economic output, as measured by Gross Domestic Product (GDP), (Nepal = 65 KWh/capita in2005 and targeted to reach 100 KWh/capita by 2012)

*OECD (Organization for Economic Cooperation and Development) Member Countries

(30)

Australia, Austria, Belgium, Canada, Czech Republic, Denmark, Finland, France, Germany,

Greece, Hungary, Iceland, Ireland, Italy, Japan, Korea, Luxembourg, Mexico, Netherlands, New

Zealand, Norway, Poland, Portugal, Slovak Republic, Spain, Sweden, Switzerland, Turkey,

United Kingdom, United StatesThe linkage between electricity demand and economic progress is evident when considering

electricity use (kilowatt-hours, kWh) on a per-capita basis relative to GDP per capita in countries


4/148

Chapter 1 4

around the world. China, South Korea and the United States are specifically highlighted in the

chart above, which displays OECD*countries in red and non-OECD nations in blue.

Source: The Outlook for Energy A View to 2030 http://exxonmobil.com/corporate/images/enlarged_eoworld.jpg

Modern energy supplies (Nuclear Energy) are still a precious commodity for millions of

people due to complex technology and higher risk posed to human and environmental

health due to leakage of radioactive radiation.

1.1.3 /

Yearly Energy Supply (Production) by type in MGJ

Type 51/52 52/53 53/54 54/55 55/56 56/57 57/58 58/59 59/60 60/61 61/62 62/63 63/64 64/65 65/66

Year 1994/95 1995/96 1996/97 1997/98 1998/99 1999/00 2000/01 2001/02 2002/03 2003/04 2004/05 2005/06 2006/07 2007/08 2008/09

Traditional 258.11 263.48 267.02 272.77 278.60 284.61 290.86 302.08 308.61 315.27 322.10 328.09 334.78 341.62 348.87

Fuel wood 230.55 235.37 237.45 242.56 247.76 253.09 258.64 269.16 274.96 280.89 286.96 292.46 298.33 304.72 311.17

Agri. Residue 10.35 10.56 11.63 11.89 12.14 12.44 12.73 13.03 13.33 13.63 13.96 14.01 14.37 14.36 14.68

Animal dung 17.21 17.55 17.93 18.32 18.70 19.08 19.49 19.90 20.32 20.75 21.18 21.63 22.08 22.54 23.02

Commercial 24.79 27.69 29.48 35.10 34.85 44.90 43.34 43.85 43.27 44.86 43.20 46.60 43.96 44.26 48.90

Petroleum 19.13 21.56 23.64 28.97 28.16 30.20 31.29 32.31 32.12 31.60 30.06 29.26 30.14 27.91 33.01

LPG 0.64 0.89 1.07 1.15 1.24 1.49 1.97 2.40 2.76 3.26 3.82 3.99 4.61 4.77 5.70

Motor sprit

(Gasoline)1.15 1.36 1.49 1.58 1.66 1.87 1.98 2.12 2.26 2.28 2.53 2.71 3.41 3.38 4.16

Air turbine

fuel1.36 1.45 1.75 1.87 2.00 2.04 2.28 1.72 1.91 2.32 2.42 2.33 2.31 2.49 2.49

Kerosene 6.56 7.58 8.82 12.52 10.69 12.01 11.47 14.02 12.64 11.27 8.66 8.22 7.17 5.63 2.54

High speed

Disel8.61 9.50 9.80 11.42 11.97 11.76 12.37 10.86 11.38 11.37 11.91 11.16 11.63 11.48 17.69

Light Disel oil 0.13 0.17 0.09 0.04 0.04 0.17 0.13 0.09 0.02 0.02 0.00 0.01 0.01 0.01 0.01

Fuel oil 0.43 0.34 0.34 0.04 0.17 0.43 0.59 0.58 0.55 0.42 -0.03 0.00 0.05 0.03 0.00

Others 0.26 0.26 0.30 0.34 0.38 0.43 0.48 0.52 0.59 0.66 0.75 0.84 0.95 0.12 0.41

Coal 2.85 3.07 2.56 2.60 2.90 10.48 7.45 6.48 5.72 7.29 6.46 10.36 6.16 8.24 7.75

Electricity 2.81 3.07 3.28 3.54 3.79 4.22 4.61 5.07 5.43 5.97 6.67 6.97 7.66 8.10 8.14

Renewable

(others)0.32 0.45 0.58 0.71 0.84 1.01 1.22 1.39 1.58 1.71 1.91 2.10 2.32 2.50 2.73

Biogas 0.30 0.43 0.55 0.68 0.81 0.98 1.18 1.35 1.53 1.65 1.85 2.03 2.22 2.38 2.59

Micro-hydro 0.02 0.02 0.02 0.03 0.03 0.03 0.04 0.04 0.05 0.05 0.06 0.07 0.09 0.11 0.14

Solar 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.001 0.002 0.002 0.003 0.003 0.003 0.004 0.006

Total 283.23 291.62 297.07 308.58 314.29 330.52 335.42 347.33 353.45 361.84 367.21 376.79 381.05 388.38 400.51


5/148

Chapter 1 5

Source: WECS Energy synopsis Report

Electricity is clean energyas it does not produce any type of pollution on its use, convertible to any form

of energy easily. Transportation and handling management is easy.

Sectorial Energy Consumption in Nepal

Historical trend of Sectorial Energy Consumption in Nepal (MGJ)

Year 51/52 52/53 53/54 54/55 55/56 56/57 57/58 58/59 59/60 60/61 61/62 62/63 63/64 64/65 65/66

Sector 1994/951995/961996/971997/981998/991999/00 2000/01 2001/02 2002/03 2003/04 2004/05 2005/06 2006/07 2007/08 2008/09

Residential 260.86 267.34 274.24 283.74 287.67 295.00 301.13 314.61 320.18 326.22 331.55 339.77 345.384 351.192 356.752

Industrial 11.08 11.76 6.43 6.90 7.54 15.72 12.99 12.52 11.97 13.72 12.74 12.99 12.7914 13.9887 13.3698

Commercial 2.56 2.85 3.20 2.94 3.20 3.71 4.13 4.94 4.09 5.33 5.33 5.71 4.6738 4.8857 5.1222

Transport 7.84 8.73 11.93 13.55 14.82 12.78 13.59 12.01 13.85 13.12 13.89 14.40 14.5095 15.0366 20.876

Agricultural 0.64 0.68 0.98 1.11 0.72 2.98 3.15 2.77 2.90 2.90 3.07 3.28 3.0106 2.5208 3.6464

Other 0.26 0.26 0.30 0.34 0.34 0.34 0.43 0.47 0.47 0.55 0.64 0.64 0.6803 0.7584 0.7399

Grand Total283.23 291.62 297.07 308.58 314.29 330.52 335.42 347.33 353.45 361.84 367.21 376.79 381.05 388.382 400.506


6/148

Chapter 1 6

Most of the Energy is used for residential use, The industrial use is comaparatively low and will

be very high in development of economic activities under the process of making new

industrialized Nepal

The amount of Per capita

electricity consumption reflects

the living standard of people and

their economic conditions.

The per capita electricity

consumption in Nepal is only 69

KWh and aimed to reach up to

100 KWh by 2012 (II nd Interim

Plan 2010-2012)

The per capita electricity

consumption of Nepalese people

is about 37 times less than the

world average and 27 times lessthan the average Asian people.

48% of the total population in

Nepal has access to the

Electricity. Only 8% of people

of rural areas enjoy it (MOF

2007, Energy Synopsis of Nepal

WECS-2010)

1.1.4

Side Effect of fossils fuels is emission of GHG gas (CO2, CH4 and N2O) causing the Globalwarming and climate change. Climate change rise of temperature, disturbance in rainfall

(monsoon rain, high intensity, unpredictable rain, landslide, flood and draught affecting


7/148

Chapter 1 7

agriculture, ecosystem, biodiversity causing large numbers of endangered species of flora and

fauna)

GHG Emissions from Fossil Fuel Combustion in Nepal in 1994/95 (Gg)

Sectors Diesel Kerosene Coal Gasoline LPG Fuel Oil Total

Residential - 291 2 - 24 - 317

Industrial 73 6 233 - - 8 320

Transport 360 19 2 75 - - 456

Agricultural 135 - - - - - 135

Commercial 4 113 26 - 15 8 166

Energy

Conversion

- - - - - 71 71

Total 572 429 263 75 39 87 1,465Sources: WECS 1996 in Nepal's Initial National Communication, 2004

Note: These exclude emissions from the burning of aviation fuel

GHG emission from Combustion of Fossils Fuel (1994/1995)

Residential21.6%

Industrial

21.8%

Transport

31.1%

Agricultural

9.2%

Commercial

11.3% Energy Conversion

4.8%

Sources: WECS 1996 in Nepal's Initial National Communication, 2004

Sectorial GHG Emission from Combustion of Fossils Fuel (1994/95)

Electricity Energy do not produce any emissions in its use so it is termed as clean energy and the

efficiency of the energy use also has been improved significantly due to invention of modern

electrical appliances.

1.1.5

The first hydropower development or installation in the world was in 1882 and it is in Wisconsin

of USA. The capacity of the first hydropower plant was only 200 kW. Similarly the first

hydropower development or installation in India was in 1987 in Darjeling. The capacity of the

Indian Hydropower project was of 130 kW. Pharping Hydel Powerhouse of 500 kW capacities is

the first powerhouse installed in Nepal in 1911.


8/148

Chapter 1 8

The Pharping hydropower station was developed with the technical and financial aid of British

Government at the cost of NRs 713373.07 within 17 months in 1911 (BS 1968 Jestha 9 completed

date) . The power house with the installed capacity of 500 kW was running successfully till 1981

but after then, the water used for the plant was diverted for drinking purpose and the plant was

shut down. Even now, this plant can be restarted if the supply of water is made possible (NEA,

2003a).

Nepals first hydropower plant was installed not so long time after the first hydropower plants

were installed in USA or in India

First Hydropower Plants

The Government of Nepal decided to open its doors to the private sector involving both local and

foreign investors to promote Public Private Partnership under the BOOT system in 1992 in order

to fulfill the growing electricity demand using Nepals abundant hydro potential.

Commissioning dates of hydropower Projects in Nepal

S.N. Name of Power project InstalledCapacity(MW)

AverageannualEnergy(GWh)

CommissionandoperationYear

Investor Cost perKW

A Hydro Electricity

1 Pharping 0.5 3.3 1911 Nepal/British RS 1426.75

2 Sundarijal 0.6 4.8 1936 Nepal

3 Panauti 2.4 7.0 1965 Russia

4 Pokhara Phewa 1.0 8.5 1967 India

5 Trishuli 21.0 114.5 1968 India US$1296.30

6 Sunkosi 10.0 70.0 1973 China US$1093.70

7 Tinau 1.0 10.2 1974 BPC

8 Gandak 15.0 48.0 1979 India US$1300.00

9 Kulekhani-1 60.0 201.0 1982WB andothers US$1950.00

10 Devighat 14.1 114.0 1983 India US$2781.69

11 Seti 1.5 1.8 1985 China

12 Kulekhani-II 32.0 95.0 1986 Japan US$1937.50

13 Marshyangdi 69.0 462.0 1989 German/WB US$3333.33

14 Andhikhola 5.1 38.0 1991 BPC

15 Jhimruk 12.3 81.0 1994 BPC

16 Chatara 3.2 3.8 1996 Nepal/WB

17 Puwa khola 6.2 48.0 1999 Nepal US$2887.10

18 Khimti 60.0 353.0 2000HPC/IPP-norway US$2250.00

19 Modi 14.0 87.0 2000 Nepal/Korea US$1864.86

20 Bhotekoshi 36.0 250.0 2000 IPP (USA) US$2666.67

21 Kaligandaki 144.0 625.0 2001 Nepal/ADB US$2638.89


9/148

Chapter 1 9

22 Indrawati 7.5 49.7 2002 IPP-Nepal US$2666.67

23 Chilime 22.1 137.0 2003 IPP-Nepal

24 Tatopani (Myagdi) 2.0 10.2 2004 Nepal

25 Sunkosi 2.6 14.4 2005 Nepal

26 Piluwa khola 3.0 19.4 2006 IPP-Nepal

27 Khudi 4.0 24.3 2006 IPP-Nepal

28 Middle Mrshyangdi 70.0 398.0 2009Nepal/German NRs 312000

29Small hydropwer-32 nos(Government) 8.1 37.0 different time Nepal

30Small hydropwer-12 nos(Ipp-Nepal) 7.64 40.0 different time Nepal-IPP

Total Hydro electricity 635.84 3355.9

B Thermal

1 Hetauda- Disel 14.4 43.0 1963 Nepal

2 Duhabi multifuel 39.0 165.0 1991Nepal-Finland

Total ThermalElectricity 53.4 208.0

Grand Total 689.24 3563.9Source: NEA annual report 2009, and 10 Yr 10000MW Task force Report 2009 (BS 2065)

Project under Construction

S.N. Name of Project InstalledCapacity(MW)

Investor Status

1 Lower Indrawati Khola SHP 4.50 IPP-Nepal

2 Mardi Khola SHP 3.10 IPP-Nepal completed

3 Ridhi Khola 2.40 IPP-Nepal completed

4 Upper Hadikhola 0.991 IPP-Nepal completed

5 Lower pilluwa 0.990 IPP-Nepal testing

6 Kulekhani III 14 Japan

7 Chamelia 30 Nepal/Korea

8 Mai khola (Himal Dolakha Hydro) 4.455 IPP-Nepal completed

9 Lower Modi (United hydro) 9.9 IPP-Nepal

10 Siprin khola (synergy HPP) 9.658 IPP Nepal

11Ankhu-1 Hpp (ankhu khola Jal bidhutcompany) 6.930 IPP Nepal

12Phawa khola HPP (Shivani Hpp Pvtltd) 4.950 IPP Nepal

Source: NEA annual report 2010/11

S.N. Description InstalledCapacity(MW)

Productionin Wetseason(maximumMW)

Productionin Dryseason(minimumMW)

Remarks

A Production of Electricity

1 Non Reservoir Project

NEA power projects 385.66 350 141.9Independent PowerProducers (IPP) 158.315 150 58.1

Sub Total 543.975 500 200

2 Reservoir Project

NEA power projects 92 0 92Independent PowerProducers (IPP) 0 0 0


10/148

Chapter 1 10

Sub Total 92 0 92

3 Thermal Power

NEA power projects 53.4 20 20

Total 689.375 520 312

B Import of electricity

1 River Agreement

Tanakpur 20 20 12.5

Max 20 MW and7,00,00,000 KWh

annually

Kosi 10 10 5

2 Import/Export 50 50 50

3 Commercial agreement 50 50

Sub Total 130 80 117.5

Grand TotalSupply/production 819.375 600 429.5

C Demand/supply (2007/08) 640/542 720/308

D Demand (2009/10) 815 878.8

E Demand (2010/11) 890 967

F Surplus/Deficit (10/11) -290 -537

Source: 10 Yr 10000 MW Task force Report 2009 (BS 2065) and NEA annual report 2010

Load Shedding minimum 2 hours in wet season and maximum 16 hours of a day in the dry season in 2009/10 and it

has been forecasted to increase up to 18 hours of load shedding in a day during dry season of 2011/12.

The increase of annual power demand at present is about 80 MW per year and it will increase with increase of

economic activities (industrial and commercial activities) within the country.

Trend of Electricity Demand in the future


11/148

Chapter 1 11

Source: NEA Annual report 2009/10.


12/148

Chapter 1


13/148

Chapter 1 13

1.1.

The worlds total technical feasible hydro potential is estimated at 14 370 TWh/year, of

which about 8082 TWh/year is currently considered economically feasible for

development.

About 700 GW (or about 2600 TWh/year) is already in operation, with a further 108 GW

under construction [Hydropower & Dams, World Atlas and Industry Guide, 2000].

Most of the remaining potential is in Africa, Asia and Latin America:

Remaining hydropower potential is in Africa, Asia and Latin AmericaTechnically feasible Economically feasible

potential: potential:

Africa 1750 TWh/year 1000 TWh/year

Asia 6800 TWh/year 3600 TWh/year

North + Central America 1660 TWh/year 1000 TWh/year

South America 2665 TWh/year 1600 TWh/year

Total 12835 TWh/year 7200 TWh/year

At present hydropower supplies about 20 per cent of the world's electricity. Hydro

supplies more than 50 per cent of national electricity in about 65 countries, more than 80

per cent in 32 countries and almost all of the electricity in 13 countries.(Source: IAEA Report on Hydropower and the World's Energy Future)

1.1.

Nepals theoretical hydropower potential of 83 GW is about 1.5% of worlds total

hydropower potential of 5610 GW in comparison with the Nepals land (147181 km2) of

only 0.11% of the world total (Shrestha, 1985, p.34).

This shows that hydropower potential per unit land area in Nepal is about 13 times higher

than that of the world average.As the aforementioned value of hydro potential does not include that from the small river

basins (i.e. catchment areas < 300 sq. km, river length < 10 km.) and there are significant

numbers of such rivers in Nepal, the real hydropower potential of Nepal might be much

higher than this. To date, there are no comprehensive and detailed studies defining the

total micro hydro potential of Nepal from such small rivers.


14/148

Chapter 1 14

Theoretical hydropower potential of rivers of Nepal

1.1.

Although Nepal has developed its first hydropower project about a century ago, the

development pace of its hydropower development is not as it was expected and needed.

Due to this, severe load shedding is unavoidable and becomes a part of Nepalese people.Only about 1.5% of the economically feasible potential or 1% of theoretical potential has

been installed. Only about 48% of the total population has access to the electricity.

Challenges

The following are the challenges that were faced in hydropower development in Nepal

Lack of political stabilityPolitical situation in Nepal is not favorable and stable since from 1990. Any one

of elected government has completed its full phase tenure since from the great

peoples movement in 1990 (Jan Andolan of 2046). Political parties and leaders

do not have clear vision for development of hydropower and its water resourcesfor well being of the Nepalese people. Political leaders focused only on benefits

of their own people and parties rather than the overall development of Nepal.

During Panchyat period also, the development pace in hydropower is not

encouraging as the development activities were based on grant and aid of

developed countries and developing partners. There was no vision of technologytransfer and independency. During Ranas regimes, the hydropower development

was carried out only for limited use of their own benefits.

Present political instability has brought disorder in laws and regulations enhanceviolence and insecurity at local and central level. This resulted retardation of

investment and development activities in hydropower.

Lack of Technology and Skilled man powerAlthough Nepal has large potential of hydropower development, it does not have

its own technology and sufficient skilled man power. The Nepalese engineer has


15/148

Chapter 1 15

lack of confidence in engineering due to little experience and knowledge in design

and construction of hydropower projects of large scale greater than 50 MW. Thetechnology and technical equipments for quality monitoring and standard

specifications and norms has not been developed in Nepal. The machines andhydro-mechanical equipments production and maintenance facilities has not been

developed fully yet.

Lack of InvestmentThe development of hydropower project needs considerable investment i.e. Rs

12~14 corore for 1 MW hydropower development. The gestation period (i.e. the

time period between the start of investment to the start of return from the project)

of the hydropower projects are higher than 4~5 years, and the payback period

(complete recovery of investment) of the hydropower projects are 8~10 years.

Although the investment in hydropower is relatively high but not more beneficial

compared to the investments in other sectors like trade and commerce, industriesetc, the investment in hydropower is not growing up in the scale as it is required.

Without foreign investment, the hydropower development could not be

accelerated to its desired level. For this, stable political system, Good safety and

security, clear policies and priority of hydropower developments, assured markets

and return of their investment mechanism are essentials for creating conducive

environment of investment in hydropower.

Lack of infrastructuresThe feasible and attractive hydropower projects are located in remote areas where

physical infrastructures like access road, transmission lines, basic health facilitiesand other essential skilled manpower and construction materials with equipmentsavailability is very poor or not available at the site. Development of these

infrastructures needs heavy investments.

The lack of integrated infrastructure developments policies made haphazard

developments resulting the minimum benefits of the infrastructures that could be

achieved. The poor maintenance and rehabilitation of the infrastructures reduces

the service quality and reliability of the services.

Risk imposed by Global Warming and Climate Change

The water is the basic raw material for the power production through hydropowerplant. The global warming (0.06 0C ~ 0.08 0C in Nepal~Himalayas) has resultedincrease of atmospheric temperature resulting the fast rate of snowmelt. The snow

in the Himalayas acts as the overhead tank and gives flow in the rivers

continuously throughout the years. Fast melting of snow due to global warming

results the depletion of snow storage and can cause depletion of low flow in long

term posing threats to the hydropower production. The disturbances in monsoon

rainfall pattern and amount are also attributed to the climate change. The extreme

drought and flood events with high sediment and debris flow seems to be more


16/148

Chapter 1 16

frequent in recent years posing serious uncertainties and threads to the hydro-

power projects. The GLOF events has been increased and caused serious floodswith debris flow which may damage the structures of hydropower projects. The

natural risks and threads have been taken as the one of the most difficultchallenges in hydropower development.

Opportunities

Nepal is in between the two giant countries China and India. Both of the countries are

developing very rapidly in recent years. They need lot of power/energy for their

development activities. Nepal has more than six thousands of rivers and rivulets and has

favorable topographical and geological conditions for hydropower developments. Thefollowing points can be taken as opportunities for hydropower development in Nepal.

Clean Energy

Hydropower is taken as clean energy as it does not produce any pollution during

its use and production. It is renewable and hence more attractive sources of

energy. The technology of its production and uses has been already developed and

affordable. The hydropower is easy to handle and transport from its production to

the load center.

The water of Nepalese rivers can be taken as white coal and policies has been

introduced to exploit the white coal in worldwide for supply of necessary energy(IAEA energy for future world).

Market availableThe market for Hydropower is easily available for Nepal since its neighbors are

being in developing phase and the economic activities are being taken at rapidly.

The electricity energy produced in Nepal can be exported to India and China thus

helps to reduce trade gap of the nations with these country.

Electricity produced can also be used for domestic use in promotion of industrial

activities and replacement of the petroleum fuels that has to be imported paying

hard currency. Thus market for hydropower development is abundant and can betaken as opportunities.

Favorable geological and topographical conditionsThe steep topography (High river gradient) with good geological conditions (hardrock in river bed) are the favorable and essentials for development of hydropower

projects at low cost of investment. The perennial rivers with considerable low

flow are good for hydropower productions. Although sediment flow rate in the

middle mountains and chure range are high, the sediment flow and production

rate in high Himalayas are less and can be taken as the opportunity.

Cheap labor force availability


17/148

Chapter 1 17

Nepal has developed lot of engineering institutes and technical centers after the

restoration of Democracy in 1989 (BS 2046). The institutions have produced lotof skilled and semi skilled man powers. Although the human resources do not

have experience of the mega projects, they have equipped with theoretical andpractical knowledge at the institutions. These human resources are available at

cheap rate compared to that of the man power from developed countries. The

availability of the man powers both skilled and unskilled labors can be taken as

good opportunities to develop hydropower schemes for harnessing nations water

resources.

1.2 ()

Power System comprised of three components; a) Production/generation b)

Transmission/ evacuation and c) Distribution.

1.2.1 /

Power production in the form of electricity needs rotation of the electric coil inside strong

magnetic fields. Generator is the electromechanical parts which converts the mechanicalenergy in to the electrical energy based on Faradys Principle. The coil is rotated in stron

magnetic field at high velocity to induce electricity in the coil. The range of voltage of

the generated current is 6.6KV to 11 KV. The shaft of the generator can be rotated

providing energy from various sources like from coal, Diesel and water. Based on the useof energy to drive the shaft of generator, power system can be grouped in to two systems.

Thermal Power system

Electricity is produced from running of generator directly from shaft energy obtained

from diesel engines. Steam engines can also be used for to drive the shaft of generator.Coals/Gasoline is used as main fuel for steam engines. The efficiency of the thermal

power system is relatively lower than the hydropower generation and it is expensive than

hydropower regarding the operation and maintenance cost. The total installed capacity of

thermal power is 53.4 MW but about 20 MW is in operational use.

Hydropower system

In this system, Electricity power is generated by the use potential or kinetic energy of

water. As, water is being renewable in nature, high importance has been provided for thissystem. Besides it, hydropower system is pollution free and so, it is taken as the

environmental friendly system for power production. Although the investment cost ishigh, the operation and maintenance cost is low and it is attractive being the clean energy

having no pollution during production and consumption. The total installed capacity is

about 634.3 MW out of which 92 MW is reservoir type and rest 542.3 MW is runoff river

types which produce about 500 MW only in wet season and 200 MW in dry season.

Advantages Disadvantages

i) Renewable (white coal) High gestation periodii) Running cost is low high investment costiii)Quick response (1 to 2 min) to power system (peaking) dependent in nature


18/148

Chapter 1 18

Solar power system

Solar or photovoltaic cells are used to trap solar energy and to produce electricity. InNepal solar system is used only for lighting the in the rural areas as the power production

is in small scale and expensive.In developed countries the other sources of power supply are Nuclear, Tidal, Wind and

Geothermal.

1.2.2 /

Generally the load centre is far from the generation or production system and the power

produced from the plants are evacuated or transmitted to the distribution centre through

transmission line. Transmission Lines do not supply the power to the customer it suppliesthe power to the distribution centre (Sub stations) only. The electricity generated from the

generators are in 11 to 25 KV range and stepped up to the transmission voltage33/66/132/230 KV. Transmission line may be single circuit or double circuit depending

upon the numbers of wires in the transmission line. In developed country high

transmission voltage 765 KV and 1200 KV as power capacity is directly

proportional to the square of transmission voltage.For transmission line greater than

600 km, DC transmission is economical at 400 KV and the line is connected to AC

system at the two ends through a transformer connecting through converter and inverter

(silicon control rectifier)

1.2.3

Based on supply system, power system can be divided into isolated and grid system. Inisolated system the power is supplied from a definite power plant while in grid system the

supply of power is made available from multi power plants. Failure of a particular power

plant will not disturb the power supply in grid system. The grid system might be regional,

national or international also.

Advantage

Use of remote energy source Improve reliability Utilization of the time difference between various time zones where peak demand

are not coincident, require low installed capacity

Maintenance of power plant possible without disturbing the supplyDisadvantage

High power loss in transmission lines in the grid connected system due to long

transmission lines

1.3 ,

Less than 100 KW: Micro

100 KW to 500 KW: Mini

500 KW to 10 MW: Small hydro

10 MW to 300 MW: Medium Hydro

Bigger than 300 MW: Big Hydro


19/148

Chapter 1 19

1.3.2

Low, medium and high head are terms used to indicate the most suitable type of turbine

for the project. Various types of turbines are used depending upon the head of the powerplant.

Low Head up to 10 m Use: Cross-flow, axial-flow or propeller turbine (Kaplan)

Medium Head 10 m to 200 m Use: Cross-flow, Francis, Pelton or Turgo turbine

High Head 200 m to 1000 m Use: Pelton, Turgo-impulse or Francis turbine

Francis Turbine

Pelton Turbine

Kaplan Turbine (Propeller)

Pelton Turbine Runner Close view


20/148

Chapter 1 20

Bulb Turbine (horizontal and vertical alignment)

Schematic View of Hydropower Plant

Dandekar book

Low head Less than 15 m

Medium head 15 to 70 mHigh Head 71 to 250 m

Very High Head above 250 m

P.N. Modi and Seth Book

Low head Less than 30 m

Medium head 30 to 250 mHigh Head above 250 m

Turbine Type and Use

High head Impulse Turbine (Pelton,

turgo turbine)

Medium Head Mixed flow Turbine

(Farncis,)

Low Head axial flow Turbine (Kaplan,

Bulb, Propeller)Medium and Low Head Turbines are

Reactive Turbine


21/148

Chapter 1 21

1.3.3

Runoff the river, Pondage Runoff River (PROR), storage, pump storage plants and Tidal

Run-of-River (RoR) type

A run-of-river project is built to use some or most of the flow in a stream depending upon

the flow throughout the year. No attempt is made to store water for the dry periods. A

run-of-river project would not normally have a dam, other than an intake weir, which is a

very low head structure at the intake. The intake weir keeps the water in the stream high

enough to fill the pipe at all times.

Suitable where the fluctuation of flow in dry season and wet season flow are small like inrivers coming from Tibet at border such schemes do not alter the flow regime at the

downstream. Khimti, Khudi, Trishuli etc

Pondage Run-off River Type (PROR)

Run off river plants are provided with pondage to regulate flow to the plant which

enables them to take care of our to hour fluctuation in load on the plant throughout the

day or week. The water in river are stored at the head pond during non peak load or off

peak load hours of a day to with draw or use the stored water for power production

during the peak hours of load. The PROR power plants may operates at full capacity forall hours during high flow or rainy season but it produces power at full capacity at peak

load hours. The power plant may shut down or operate at lower capacity during the peak

off hours in dry season. At the same location, the installed capacity of the PROR plants

are higher than the ROR type plants and operate at full capacity only at peak load hours.

Marshyangdi 69 MW, Middle Marshyangdi 70 MW and Kaligandaki A 144 MW are

PROR project in Nepal.

Reservoir Storage Plants

Hydropower plants which draw water from large storage reservoirs developed byconstructing dam across the river are called reservoir or storage project. Depending upon

the storage volume, these plants can hold surplus water from periods when the stream

flow exceeds demands for utilization during the period when demand exceeds the stream

flow. Better utilization of hydropower potential is thus achieved with such plants. The

water flow stores in wet season to supply in dry season. Kulekhani reservoir project is

only one storage project in Nepal Kulekhani-I 60 MW and Kulekhani-II 32 MW.

Pump storage


22/148

Chapter 1 22

Plants in which all or portion of the water used by these plants is pumped back to the

head water pond to be made available again for the power generation during peak hours

of demand. This type of the power plant essentially consists of a tail water pond and headwater pond. During peak load water is drawn from the head water ponds through the

penstock to operate hydro electric generating units. The water is collected in to tail water

pond and during the off peak hours, pumps are operated to pump the water back from the

tail water pond to the head water pond. Power for operating the pumps is provided by

some of peak thermal or hydropower plant.

For head up to 120 m special Francis turbine has been developed for the pump storage

plants. The runners of the turbines are so shaped that they can be used both as turbine as

well as pumps. Such turbines are known as reversible turbines.

For high head, multistage centrifugal pumps are used for pumping water and high head

Francis Turbines are installed in power production.

Tidal Plants

Sea water rises or falls twice a day, each full cycle occupying about 12 hours 25 minutes.

The tidal range or the difference between the high tide and low tide level is utilized to

generate power.

This is accomplished constructing a basin separated from the sea by a wall and installing

a turbine in opening through this wall.

During high tide water passes from the sea to the basin thus running the turbine and

generating power. During low tide, water from the basin flows back to the sea which can

also be utilized to generate power by providing another set of turbine operating in

opposite flow direction.

ExampleFrance: Rance power plant, tidal range 11 m, 9 units of 38 MW each with total

capacity of 342 MW.

12 hr 25 min 12 hr 25 min

Tidal Ran e


23/148

Chapter 1 23

Base load plant and Peak plants

Base load plants

As the name indicates base load plants are those which are capable of substantially

continuous operation in the base of the load curve throughout the year. Both ROR and

Reservoir plants can be used as base load hydro plants. When ROR plants withoutpondage are used as base load plants, their full plant discharge is seldom more than the

minimum flow of the river and can not support the power system during dry season.Hence the reservoir hydro power plants are used as base load plants during the low flow

season.

Peak Load Plants

Peak load plants are those designed and constructed primarily for taking care of peak loadof a power system. Pumped storage plants are peak load plants. PROR plants can operate

both as peak load and base load plants depending upon the river flow and load on the

power system.

During High flow seasonROR plants runs at maximum capacity and acts as base load plants in Nepal

Thermal plants and reservoir plants are operated as peak load plants to generate extra

power needed beyond the capacity of the ROR plants.

During Dry Flow season or low flow season

ROR plant operates at very low capacity due to lean flow available at dry season. TheROR plants only can not support the base load of the power system. Hence additionalpower that may require supporting the base load, reservoir power plants and thermal

power plants are also operated as the base load plants. PROR projects are used as peak

load power plants and load shedding plan is introduced at peak our due to insufficient

power production during dry flow season.

Hydropower plants have better peaking characteristics (response fast maximum 3 to 4

minutes) and there is absolutely no wastage when they are idle.

Thermal power plants have slow response (at least 30 minutes) and continuous loss of

fuel at idle conditions.


24/148

Chapter 1 24


25/148

1Chapter 2

2.0 Power Regulation

Power regulation is the study of the power or energy consumption/demand

variations and their relationships in a particular power supply system for a

community, society, cities, and region or in country or countries. The demand of

power is termed as load and supply of energy is termed as power in power

regulation study. As the individual consumer level, the electrical demand is quiteunpredictable, however as the demands of the various users are accumulated and

added at a feeder or substation, they begin to exhibit definite pattern.

2.1 Power variation: Daily, weekly and seasonal

Power consumption in a community or society is not constant forever. It

fluctuates hour to hours in a day and day to day in week and month to months in

different seasons. The power consumption in a society or community depends on

the following factors.

Population: the population number/size that has to be served by the powersystem directly governs the power consumption/demand in the system. Higher

the number of people larger the power/energy demand. During tourist season the

power demand in Pokhara is higher than that in the non tourist season due to

increase of the people in the city that has to be served. The power demand in

small city is smaller than that of the demand in big cities. Balaju substation needs

high power/energy than that in Bhaktapur substation.

Climate: the climate is another important factor that influences rate of energy

consumption per unit time. In Nepal, the power demand is higher in winterseason for heating purpose compared to that in summer season while in India; the

power demand in winter is less than that compared in summer season mainly due

to high temperature and high power demand for cooling.

Living standard: the living standard and life style of the people also directly

affects the energy/power demand. The use of electrical appliances for cooking

(rice cooker, hot plate, oven etc), heating and cooling consumes considerable

amount of electric energy. The industrial area needs a lot of energy and power

compared to that in residential areas. The energy consumptions in city areas are

higher than that of remote areas mainly due to life style and living standard of the

people.

Daily Load Curve: Daily Variation of power supply or demand in a power

system is known as daily load curve. The power demand is not constant in

different hours of a day and it varies from hours to hours depending on the types

of areas that have to be served. For domestic area, the peak demand generally

occurs at 18:00 to 20:00 for cooking and lighting purpose at evening. The peak

demand times slightly shifted earlier during winter season and the peak demand

is also higher than that in summer season. The daily load curve for industrial area

is quite different than that of the residential as the peak load generally occurs in

day time as the industries runs at full phase during the office working hours. Thepeak load may not alter too much even in night time if there are large numbers of

industries that runs continuously 24 hours.


26/148

2Chapter 2

Typical Daily load curve for residential Area

Typical Daily load curve for industrial/commercial Area

Weekly load curve: the power demand or consumption in a community or

society is not same in all days of a week. The variations of the load in different

days of a week are known as weekly load curve.

Typical Weekly load curve for industrial/commercial and domestic Area

Pow

er(MW)

2422201816121086

Time of a Day

Power(MW)

2422201816121086

Time of a Day

Commercial

Industrial

Power(MW)

SatFriThuWedTue10

MonSun

Days of a week

Domestic


27/148

3Chapter 2

Source: NEA annual report 2009

Source: NEA Annual Report 2009


28/148

4Chapter 2

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Average

MW load demand 930 950 920 900 885 870 840 850 880 900 880 900 892.083

MM-power available 430 425 430 440 450 500 560 600 600 585 550 500 505.833

0

100

200

300

400

500

600

700

800

900

1000

Pow

erDemand(MW)

Month

Monthly Variation of Load in Power System

Typical monthly Load variation pattern in Nepal in 2009/10

Seasonal load curve: The curve showing the variation of power consumption or

demand in a power system feeding to a community/society or cities in different

seasons is known as seasonal load curve. The seasonal load of a particular place is

mainly governed by the climate and culture besides the living standard & style of

the society. E.g. the power demand in the winter in Himalayan and high mountain

areas are higher than that in the Terai/ plain terrain region of Nepal mainly due to

cold and arid climate in the winter season. The power demand in the Septemberand October is high in Nepalese society mainly due to main festival (Dashain and

Tihar) and culture (Depawali). The industries and commercial sectors are also run

at full phase targeting the supply and service for the main festival.

The study of the power/load variation is important for planning of power

production/generation and transmission and distribution utilities. It also helps to

impose systematic tariff of electricity based on the consumption amount and the

sector of services. It also helps to prepare guide lines for operation and

maintenance of power projects to achieve the targeted service at optimum cost for


29/148

5Chapter 2

generation, transmission and distribution system. Hence it ultimately helps to

formulate policies in energy sectors to support sustainable economic development

of country.

2.2 Different types of factors and their relationship

Load Factor: It is the ratio of the average load during a certain period to the

maximum or peak load during that period. The load factor is thus related to the

certain period of time consideration and therefore, there will bedaily load factor,

weekly load factor, monthly load factorand yearly load factordepending uponthe time period.

LoadtoPeakingcorrespondEnergyTotal

oducedEnergyTotal

LoadPeak

LoadAverageLFfactorLoad

Pr)( ==

Load factor of a power plant that has been used to supply the power in a system

would vary greatly with the character of the load. High load factor in Industrial

area is nearly 1 while it is low in residential area as low as 0.25 to 0.30.

The installed capacity of a power plant/s has to be equal to the peak load but the

total number of units KWh generated or used will be governed by the average

load.If load factor of a power plant is low, large proportion of the generating capacity

remain idle for most of the time and the cost of generation per unit energy (KWh)

/power is high.

Load factor value of 0.80 is generally taken during the feasibility study of

hydropower project in Nepal.

Utilization factor or Plant use factor: It is the ratio of peak load developedduring a certain period to the installed capacity of the plant.

CapacityInstalled

periodcertainduringDevelopedLoadPeakUFfactornUtilizatio =)(

It represents the maximum proportion of the installed capacity utilized during that

period of consideration.

With constant head commonly in hydropower plant, utilization factor wouldrepresent the ratio of the water actually utilized for peak load power supplycorresponding to the maximum water that can be withdraw from the river to

produce installed capacity.

The values of utilization factor commonly vary from 0.4 to 0.9 depending uponthe plant capacity, load factor and available pondage or storage.

Capacity Factor or Plant factor:It is defined as the ratio of the energy that the

plant actually produced during any period to the energy that it might have

produced if operated at full capacity throughout the period.


30/148

6Chapter 2

TCapacityInstalled

TdAverageLoa

oducedEnergyofCapacityPotential

gyoducedEnerActuallyCFfactorCapacity

==

Pr

Pr)(

The capacity factor will be equal to the load factor if the maximum peak load of

the duration is equal to the installed capacity of the power plant/s

For hydropower plants, the capacity factors varies from about 0.25 to 0.75

depending upon the plant capacity, available pondage and storage and the load

characteristics curve.

Diversity factor: It is the ratio of sum of all individual max demands by the

customer to the actual peak load of a system.

systemtheofloadpeakActualcustomerthebydemandindividualsumDFfactorDiversity max)( =

This factor gives the time diversification of the load and used to decide the

sufficient generating plants and transmission utilities.

If all demands came at the same time, the diversity factor will be Unity or one.The installed capacity that needed to be installed in the power system would be

much more. But the Diversity factor is generally much higher than unity (greaterthan 10 for domestic and greater than 5 for domestic)

Reserve factor:it is the reciprocal of utilization factor. It is the ratio of Installedcapacity to the peak Load.

LoadPeak

CapacityInstalledFactorserve =Re

Relationship between Capacity factor, Load factor and Utilization factor

Capacity factor = load factor* Utilization factor and

Reserve factor = load factor / Capacity Factor

Proof

CF = LFUF

From RHS

LFUF = Average load/Peak load Peak load/ Installed capacity

= Average load/Installed capacity = CF

So, CF = LFUF and RFCF

LF

UF==

1


31/148

7Chapter 2

Numerical Examples:

1 Two Turbo Generators each of capacity 25000 KW have been installed at a hydel powerplant. During certain period the load on the hydel plant varies from 15000 KW to 40000

KW. Calculate as follows:a. The total installed capacityb. The load factorc. The plant factor or capacity factord. The utilization factor

Solution: a) the total installed capacity = 2*25000 = 50000 KW

b) The Load factor LF =average load/peak load= 27500/40000 = .6875 = 68.75%

c) The plant factor = Average load/installed capacity = 27500/50000 = 55.00%

d)Utilization factor = Peak load/installed capacity = 40000/50000 =0.80 = 80.00%

2 A power station supplies the following loads to the consumer as given below:a. Time (hr) 0-6 6-10 10-12 12-16 16-20 20-22 22-24b. Load (MW) 30 70 90 60 100 80 60

i) Draw the load curve load factor for the plantii) What is the load factor of a stand by equipment of 30 MW capacity if it is taken

up all loads above the 70 MW? What is the plant factor and plant use factor of the

standby equipment?

Solution: i) Draw the curve by yourself

For Load factor calculationAverage load = (30*6+70*4+90*2+60*4+100*4+80*2+60*2)/24 = 1560/24

Load Factor (LF) = Average Load/Peak Load = 1560/(100*24) = 0.65 = 65.0%

ii) Installed capacity of stand by station (equipment) = 30 MW

Load taken by stand by station

Time (hr) 0-6 6-10 10-12 12-16 16-20 20-22 22-24Load (MW) 0 0 20 0 30 10 0

Average Load = (20*2+30*4+10*2)/8 = 180/8 = 22.50

Load factor for the stand by station = 22.50/30 = 0.75 = 75.0%Plant factor or capacity factor of the stand by station

= actually produced energy/potential to produce energy

= (ave load*T)/(Installed capacity *T) = (20*2+30*4+10*2)/(30*8) = 180/240= 22.5/30 = 0.75 = 75.0%

iii) Plant use factor or Utilization factor of the stand by station

= peak load /Installed capacity = 30 /30 = 1.0 = 100%

Check for relationship CF = LF* UF or 0.75 = 0.75*1 =0.75 holds true

Home work: Find the load factor, capacity factor and utilization factor of a stand by thermal

power plant having a capacity of 200 MW to supply power at the time greater than 700 MW in

Power system of Nepal at the following situation:

Time

(hr)0-6 6-8 8-10 10-12 12-14 14-16 16-18 18-20 20-22 22-24

Load

(MW)500 700 800 875 900 850 825 875 800 600


32/148

8Chapter 2

2.3 Definition and meaning of terms such as Firm power, Secondary power

Flow at intake site (m3/s)

Year: 2006

Day Jan. Feb. Mar. Apr. May Jun. Jul. Aug. Sep. Oct. Nov. Dec. Year

1 2.11 1.99 1.74 1.55 2.25 4.54 15.89 13.96 16.11 14.78 3.76 1.22

2 2.08 1.99 1.74 1.52 2.16 5.12 16.66 14.42 13.88 13.69 3.48 1.15

3 2.02 1.94 1.68 1.48 2.14 8.25 15.16 13.96 13.25 13.25 3.21 1.15

4 1.99 2.02 1.68 1.61 1.91 6.53 16.33 13.69 12.17 12.08 2.91 1.07

5 1.99 2.08 1.61 1.80 1.85 8.14 16.11 16.66 11.43 11.78 2.65 1.02

6 1.97 2.08 1.61 1.94 1.74 8.30 15.05 14.70 10.04 10.91 2.56 0.99

7 1.91 2.08 1.57 2.05 1.68 8.90 15.46 14.07 8.74 9.55 2.39 0.93

8 1.91 2.08 1.57 1.97 1.68 8.11 14.61 14.51 11.08 7.92 2.14 0.899 1.94 1.99 1.61 1.74 1.59 7.54 16.79 14.07 36.20 7.27 2.05 0.84

10 1.91 1.97 1.61 1.74 2.36 8.03 16.22 12.71 12.71 6.97 1.83 0.84

11 1.85 1.91 1.74 1.70 2.28 10.12 14.07 11.87 13.88 6.69 2.11 0.86

12 1.83 1.91 2.42 1.68 3.73 8.74 14.61 11.57 13.69 6.40 1.91 0.86

13 1.83 1.91 2.33 1.68 4.27 8.25 21.17 11.29 11.29 6.89 1.80 0.84

14 1.88 1.91 2.14 1.68 4.90 7.40 13.61 10.91 11.35 7.08 1.72 0.81

15 1.99 1.83 2.08 1.61 3.54 6.97 13.61 8.95 12.65 7.35 1.68 0.76

16 1.99 1.83 1.97 1.61 2.39 6.83 13.34 8.82 11.43 6.45 1.63 0.75

17 1.94 1.85 1.85 1.52 1.99 7.27 13.69 7.78 11.13 5.99 1.52 0.75

18 1.91 1.91 1.72 3.08 2.11 7.35 13.61 7.21 10.99 5.52 1.48 0.7119 1.91 1.91 1.61 5.74 1.85 6.83 14.07 7.46 10.26 5.36 1.48 0.65

20 1.91 1.99 1.70 4.16 1.99 6.34 29.39 10.86 9.77 5.23 1.55 0.60

21 1.91 1.91 1.72 3.43 2.16 5.93 19.92 9.61 9.17 5.63 1.52 0.59

22 1.83 1.91 1.65 2.65 2.05 5.72 17.64 9.25 8.82 5.31 1.48 0.58

23 1.99 1.91 1.61 2.56 2.28 6.04 17.31 8.38 25.64 5.12 1.48 0.57

24 1.97 1.91 1.55 2.56 2.14 5.93 16.76 7.97 51.16 4.76 1.42 0.56

25 1.91 1.83 1.55 10.45 2.05 6.31 17.09 8.90 43.82 4.68 1.42 0.55

26 1.88 1.83 1.72 4.00 2.02 11.21 17.85 21.88 30.75 4.49 1.42 0.52

27 1.83 1.83 1.74 3.37 2.19 11.13 41.91 17.85 20.47 4.35 1.44 0.51

28 1.83 1.83 1.74 2.62 5.39 14.61 17.53 14.23 18.40 4.30 1.39 0.51

29 1.91 1.68 2.39 4.68 16.22 16.98 17.09 19.95 4.22 1.33 0.51

30 1.91 1.63 2.28 6.18 14.78 17.53 49.26 16.87 4.14 1.28 0.49

31 1.97 1.59 6.48 15.16 17.85 4.00 0.49

Min 1.83 1.83 1.55 1.48 1.59 4.54 13.34 7.21 8.74 4.00 1.28 0.49 0.49

Mean 1.93 1.93 1.75 2.60 2.78 8.25 17.25 13.61 16.90 7.16 1.93 0.76 6.40

Max 2.11 2.08 2.42 10.45 6.48 16.22 41.91 49.26 51.16 14.78 3.76 1.22 51.16


33/148

9Chapter 2

Mean Monthly and Yearly Discharge (m3/s) at intake site

Year Jan. Feb. Mar. Apr. May Jun. Jul. Aug. Sep. Oct. Nov. Dec. Year

1983 1.53 1.22 0.98 1.93 4.87 24.66 12.08 12.63 5.42 2.65 1.72 1.58 5.88

1984 1.46 1.14 0.93 1.24 1.96 7.53 21.97 11.76 20.36 5.38 3.32 2.23 6.61

1985 1.66 1.59 1.21 1.27 2.31 4.71 12.64 11.95 12.44 9.66 4.10 2.42 5.50

1986 1.58 1.15 1.01 1.68 2.31 4.51 12.71 9.78 18.04 6.39 2.92 1.82 5.39

1987 1.26 1.06 1.18 1.37 1.95 4.02 18.36 38.76 15.92 8.67 3.76 2.30 8.19

1988 1.60 1.34 1.54 1.39 1.94 3.34 8.12 9.34 16.88 4.53 1.84 1.77 4.47

1989 1.65 1.42 1.39 1.04 2.68 8.73 11.76 9.13 13.51 5.63 2.66 1.97 5.12

1990 1.49 1.51 2.18 3.82 7.52 20.04 18.44 16.76 12.32 6.85 2.11 1.80 7.89

1991 2.23 1.79 1.78 1.87 2.25 8.55 19.09 16.78 15.17 3.54 2.21 1.49 6.40

1992 1.21 1.15 0.89 1.27 2.74 2.92 8.46 6.93 5.58 3.58 2.07 1.48 3.18

1993 1.40 1.09 0.93 1.93 2.17 4.36 8.34 11.38 7.02 4.58 2.88 1.97 4.00

1994 1.45 1.20 1.05 1.60 2.12 4.00 6.87 7.38 5.59 3.57 2.15 1.68 3.24

1995 1.58 1.30 1.08 1.40 2.10 3.80 9.00 13.92 6.65 5.77 3.13 1.78 4.32

1996 2.54 0.93 0.82 0.75 1.56 3.18 13.93 14.31 7.59 3.43 1.55 1.10 4.30

1997 0.75 0.69 0.57 0.97 1.27 7.78 7.46 58.24 46.54 21.15 7.67 3.70 13.04

1998 1.80 1.86 3.67 5.25 4.46 7.65 38.64 25.64 29.66 12.46 3.16 2.05 11.38

1999 1.76 1.49 1.12 0.92 2.31 16.74 33.75 33.20 28.85 13.66 4.95 3.18 11.84

2000 3.24 2.94 2.01 2.63 6.40 10.64 13.72 16.60 16.55 9.72 5.09 2.52 7.67

2001 1.57 1.51 1.28 1.23 3.81 7.05 10.72 15.13 19.57 20.36 5.36 2.68 7.54

2002 1.73 1.40 1.14 2.26 2.09 5.36 30.75 16.00 15.50 5.44 2.27 1.04 7.14

2003 0.62 0.61 0.77 0.88 0.76 10.59 29.66 17.36 12.41 8.65 2.21 0.69 7.10

2004 1.17 0.75 0.76 0.90 2.59 8.68 23.98 9.88 14.83 9.28 3.48 1.71 6.50

2005 1.06 0.79 0.54 0.79 1.09 2.99 19.38 23.13 10.42 8.00 3.00 0.90 6.07

2006 1.93 1.93 1.75 2.60 2.78 8.25 17.25 13.61 16.90 7.16 1.93 0.76 6.40

Mean 1.60 1.33 1.28 1.71 2.82 8.29 17.31 17.55 15.98 7.92 3.15 2.09 7.05


34/148

10Chapter 2


35/148

11Chapter 2

Duration curve:

The study of variations of the load or supply of power by Load factor, capacity

factor and utilization factors are possible only for short period of particularduration like daily weekly and monthly. For longer duration greater than five

years, it becomes cumbersome to plot the curves and to utilize them for various

calculations on yearly basis. Complexity will be added to account variations of

daily load curves for different season and varying demand.

Duration curve is the plot of loads or power supply/production and the percentage

of time (generally 1 year) during which those loads or power supply/production is

equal or higher occurred. Depending upon the parameter like load, flow or power

the duration curve is called as Load duration curve or Flow Duration Curve or

Power Duration Curve.

The Duration curve may be constructed for any duration of times. The load or

flow or power occurred during the time period is arranged in descending order

along with the time during which they occurred.

The area under the load duration curve represents the total energy

production/consumption for the duration. The load factor is given by the ratio of

area under the curve to the area of the rectangular corresponding to the maximum

demand occurring during the course of time.

Typical Load duration curve for a hydropower plant

Firm Power: It is also known as primary power and the energy generated from

the firm power is known as base energy.

Curve with Storage

O

D

B

A

C

Primary Energy

Pw = IP

Fp(w)

Power(MW)

Time % of a Year

Secondary Energy

40% 100%

Pw = Installed Power IP = Q40H

Fp (w) =Firm Power = QminHQ40= 40 % time exceedence flow

Qmin= Minimum flow

Load Factor LF =Area under the

curve CBAO/Area of the rectangleAOCD


36/148

12Chapter 2

The minimum power which can be generated throughout the year from the hydro

electric plant is called its firm or primary power.

For a Run-off-River plant without any storage, the firm power would correspond

to the minimum flow of the river which would be available throughout the whole

year. By providing the storage (pondage), the firm power can be considerably

increased.

The primary energy is reliable and available throughout the whole year and hence

have high value for reliable supply of energy.

Secondary Power:It is also known as non firm power. The power in addition to

the firm power would be generated for only a part of the year is known as

secondary or non firm power. The power is also known as surplus power and the

energy is known as surplus Energy. The secondary power is available

intermittently at unpredictable time and hence has less value compared to that of

primary power.

The secondary power is useful in an interconnected system of power plants. At off

peak hours, the secondary power station (captive plant or thermal plants acting as

stand by station) may call upon to relieve inter connected station thus affecting

economy. The secondary power may also be used to take care of reducing load

shedding hours by sharing the load as per power supply from peaking power

plant.

Numerical Example: Assuming that the daily flow of a river is constant at 15 m3/ and

net head of the power plant is 10 m and overall efficiency of 80%. What would be the

firm capacity of a Run-off-River (ROR) plants? What would be the firm power if the

power plant is developed as Pondage Run-off-River (PROR) designed to operate as a

peaking power station for 8 hours in a day (8 hours peaking power station)? What should

be the magnitude of the pondage and pondage factor?

Solution: Firm capacity of the ROR project without any pondage = QHP=

P = 1000*9.8*15*10*0.80 = 1176000 W = 1176 KW = 1.176 MW

Firm power of 8 hour peaking PROR project

Volume of water flow in 24 hours or in 1 day = 24*60*60*15 =1296000 m3

The flow rate if the flow is to be used in 8 hours

= Design flow Q = 1296000/(8*60*60) = 45 m3/s

Firm capacity of PROR project of 8 hours peaking station = QHP =

P = 1000*9.8*45*10*0.80 = 3528000 W = 3528 KW = 3.528 MW

Pondage factor = Q PROR/QROR = 24/Peaking hour = 45/15 = 24/8 = 3.0


37/148

13Chapter 2

Magnitude of the pondage = volume of water stored in 16 hours = 16*60*60*15

=864000 m3= 0.864 million m

3.

2.4 Power Grids, its Components of Power System

Power grid is an essential component of the power system and it is dedicated to

evacuate power from the generation point to the nearby load centre and then

distribute to the end customer. The power grid can be separated in to two parts i)

transmission lines and ii) distribution system.

Based on the number of production units connected to the grid, it can be classified

in to isolated and integrated grid. In isolated grid, the power to the grid is

supplied from only one power station while in integrated grid the power is

supplied from two or more than two power stations. East to West and South toNorth integrated power grid networks has been developed to supply energy and

power to the customers in all over the Nepal.

The INPS (integrated Nepal Power System) has to be capable of catering the peak

load although it may be present only for fraction of time while the base load

demand is available for most part of the year.

In grid system, the general planning is such that some station may be run as base

load station while some other may be run as peak load stations.

Power production is designed for optimizing the cost and comprising mixture of

thermal, hydro and nuclear sources.

Planning Strategies

1) What should be the percentage of each type of power production facility

Natural resources may dictate the choice of power production like Hydro in

abundant water resources area, Thermal if coal or petroleum mines are

available or Nuclear if sophisticated technology is available considering the

overall economy.

2) Formulate power operation policies to meet the demand satisfactory

Guiding principle

Maximum Load sharing by hydro as it is clean and renewable, ROR

and PROR in rainy season and Reservoir and PROR in dry season

Reservoir or PROR for peaking demand as quick response

Special attention for development of pumped storage hydro plants for

use of excess energy during peak off hours to


38/148

14Chapter 2

Advantages of integrated grid (INPS) over the isolated Grid

Increase Reliability: in the event of a forced or planned outage of apower station, the affected system can be fed from other stations.

River flow, storage facilities, floods and draughts are the factors that

may affect the hydropower generation.

Reduction in the Total Capacity:in an isolated system, reserve units

must be maintained separately in power station but the reduction in

total installed capacity depends on the the characteristics of inter

connected system and desired degree of service reliability.

Economic Operation:power station might be far from the load centre

depending upon the natural resources available e.g. thermal station can

be built close to the source fuels (Coal, mines, petroleum refineries)

Power Grid Component

Switch yard at power station Step up transformer

Transmission lines Wires/towers/insulators

Substation energy meter/switch yards step down transformer

Distribution network pole/tower transformer step up/down connecting wires,

insulators, energy meter fuses etc

Safety notice


39/148

Chapter 3 of Hydropower Engineering

1

3.0 Planning and Layout of Hydropower Projects 6 hours

As the investment cost and gestation period for hydropower projects are high, the pay back

return periods of the projects are relatively longer than that in other industrial sector. Planning

of the hydropower projects needs to be done based on systematic and scientific studies with

long term vision. The scientific studies include Topographical surveying, hydrological study,geological study and investigation, the project economics, finance, power evacuation,

construction material survey & testing and environmental studies (IEE or EIA) depending on

the project size and its impacts to the environment and society.

The initial planning and layout of hydropower projects is generally carried out based on

secondary data, maps and information. The final planning and layout of the hydropower

project is achieved only after systematic and scientific analyses of observed/surveyed data by

experts of different fields like engineers, economist, environmentalist and planners.

3.1 Site selection for Hydropower Projects: Reconnaissance, preliminary,hydrological and geological investigations

Site selection for hydropower projects: the ideal site for hydropower projects needs

to consider following factors

i) Accessibility: the intake and power house site should easily accessible. It makes

economic in transportation of construction materials, equipments, and man

power. It greatly affects the economy of the power plant. The delay in Arun-III

and Karnali Projects implementations are delayed mainly due to poor in access.

ii) Near to load centre: the ideal power plant should be near to the load centre. Itwill reduce not only the cost of transmission lines but also reduce the power loss

in the transmission system. The cost of transmission lines construction and

losses of energy directly depends on the length of the transmission lines and

affects the power plant economy. Shorter the length of transmission/distributed,

better the site of the project.

iii) High topographic variation: the power production from a hydel project

directly proportional to the head of the power plant. The head of the power plant

is defined as the elevation difference between the water level at the head race

and tail race channel at static flow condition. High head difference in short

distance is available in high topographic variation site or terrain. It is

advantageous to the power project as the cost of water conveyance per unit head

of the power plant will be reduced for power projects in high topographic

variation sites.

iv) Sound Geological condition: the ideal location of the power plant need to have

sound geological condition i.e. stable free from land slide, made up of hard

rocky crack free area, free from fault and thrust lines MCT (main central thrust)

and MBT (main boundary thrust)

v) Less variation of flow in different season: The flows available in the river

directly influence the power production and hence benefits of the hydel plant

affecting the economy of the project. The hydel plants with considerable low


40/148


2

flow are good to produce considerable high amount of firm power/energy. The

design parameters for head work structures design like scour depth, spillway,

size and shape of the weir/dam directly related to the high flood or design flood

magnitude. Smaller the magnitude of the flood flow, smaller the size, depth, and

shape of the structures. Hence the less variation of flow in low flow and high

flow season are more favorable for hydropower. The river flow at high

mountain site coming from Tibet like Arun, Karnali, Tamakosi have

comparatively lower variation of flow.

Different level and types of study: Reconnaissance (preliminary), Prefeasibility

and Feasibility study

Based on the depth of study, extend of analyses and coverage, the studies for

hydropower development can be classified in to mainly three phases/levels/types of

study as follows:

a) Reconnaissance or preliminary b) Prefeasibility and c) Feasibility

DoED has been prepared study guidelines of hydropower projects. The guidelines have

described the depth of analyses, coverage and requirements of testing and observations

for following different categories and types of Hydropower projects:

Hydropower Project size: 1 MW to 10 MW, 10 MW to less than 100 MW and greater

than 100 MW.

Types of Project: Run-off- river (ROR), Storage (Pondage, Reservoir)

The additional study requirements for underground structures have been given in the

study guide lines.

a) Reconnaissance (preliminary) study

It is mainly based on secondary data from maps, aerial photographs and

reconnaissance (just walk thorough field visit, eye observation)

It is conceptual design of the project based on preliminary assessment of

topographical, geological and hydrological parameters

This study is mainly for license acquisition purpose looking for access road,

transmission line, location of power house and intake site.

The alternative schemes are studied to select the most suitable projects alternativesbased on the tentative cost estimate.

The tentative cost estimate is based on major items and lump sum basis taken

considering experience of similar projects.

Investigations in Preliminary or reconnaissance level of study

Hydrological Analyses Geological/geo-technical Topographical

Assess mean monthly

flow and find 90%

probability exceedence

flow

Collect and review of

geological map, section

and Aerial photographs

Collect available largest

scale map of the project

area

Carry out measurement at

head work site during the

Regional geology and

structure

Carry out X-section

survey at the head works,


41/148


3

driest period of the flow spillway, powerhouse and

tail race site covering

HFL

Prepare catchment map

Assess the peak flood

discharge

General geology, general

morphology of the project

area

Conduct longitudinal

profile survey of the

project interest site

Check the presence of

Glacier lakes and likely

hood of the GLOF

Collect available

data/information about

seismological study

b) Prefeasibility Study

In this level of study, the review of the study made in reconnaissance studies

with further detail field surveyed data and observations obtained from precise

instruments, data series of long time and detail investigation.

General layout (showing location of the structures in Maps or drawings) of theselected alternative sites of the project components with design of civil

structures carried out using the topographical maps prepared at larger scale 5 m

contour interval for whole project area and 1 m contour interval in major

components like weir and intake, desanding basin, headrace canal, fore

bay/surge tank, penstock and power house with tail race and switch yards.

Preliminary selection of electromechanical equipment should be carried out

determining the basic parameters of turbine, generators, transformer and switch

yards

Installed capacity with number of units should be determined

Investigations in Prefeasibility level of study


Collect long term

climatologically data

rainfall evaporation, temp

etc

Collect stream flow &

sediment flow data of the

study basin or of

hydrologically similar

basin in the vicinity

Conduct detail Geological

and Geo-morphological

survey for particular sites

for intakes, desander,

canal/tunnel surge tanks,

penstock powerhouse and

tail race

Establish Control points

and new bench marks

Conduct leveling and

traverse survey for tying

control point/benchmarks

with triangulation points

of Survey department

Estimate mean monthly

flow at the intake site and

develop flow duration

curve, design flood of 50,

100 and 200 years return

period

Detail information about

the faults, characteristics

of rock, hardness

(strength), type, cracks,

permeability etc

Prepare topographical

map of whole area with 5

m contour interval, I m

contour interval for major

structural components for

at least two most

promising alternatives,

borrow area, surplus pit


42/148


4

area.

Establish a gauge station

at intake site to collect

primary data water level

and discharge

Carry out 3 cross section

survey each at intake and

power house site

covering HFL

Collect and analyze the

earthquake catalogue

(earthquake data recorded

by seismographs) of the

project area or vicinity to

it

Conduct strip survey for

water conveyance route,

canal/tunnel,

aqueduct/siphon with

detail X-section survey of

cross drainages lying

across the canal/penstock

pipe to produce 2 m

contour interval map

Develop rating curve at

intake and power house

site with slope area

method

Conduct survey for bore

holes, test pits and seismic

refraction lines

Estimate sediment load inthe river at the intake site

Carry out X-section of therivers at interval of 50 m

to 100m covering at least

500 m u/s and d/s, HFL,

reservoir impoundage

area

c) Feasibility Study

In this level of study, Detail analyses of all levels were carried out based on detail field

investigation/observations of long time series to finalize and optimize the componentsof the power projects. After completion of this study, the power project is ready to

implement for construction process. Before construction, Detail engineering design is

to be carried out to confirm the safety of the structures and bill of quantity (BOQ).

Environment study (EIA- Environment Impact Assessment or IEE-Initial Environment

Examination) also need to be completed. Environment study needs to include the

impact assessment and mitigation options and measures to minimize the adverse effects

on environment.

Economical and financial analyses were carried out in details to find EIRR (Economic

Internal Rate of Return). Loan Payback return period considering the cost of project

development and benefit gained from the project.

The construction schedule and working drawings with cost estimates are prepared in

this level of study.

Topography, Hydrology and Geology will play the main decisive role for the selection

of final location and capacity of hydropower projects.

Investigations in Feasibility level of study


Carry out discharge

measurement at the

intake site at least 4 or 5

Conduct more detail

Geological and Geo-

morphological survey for

Review and update

topographic map prepared

in prefeasibility level of


43/148


5

times in each season

(rainy, dry and medium

flow season )

particular sites for intakes,

desander, canal/tunnel

surge tanks, penstock

powerhouse and tail race

study and conduct detail

survey if required

Check the estimated flow

data at the intake based

on secondary data with

observed flow at the

gauge site established

near the intake. Check

with rainfall data also if

necessary and modify

properly if required

Detail information based

on field observations for

discontinuity (cracks)

major and minor joints,

bedding slope, foliation of

planes, the faults, thrust

and folds with their

orientation, classification

of rock, hardness

(strength), type,

permeability etc

Conduct strip survey of

access road and

transmission lines

alignment to prepare

topographic map of 1:

5000 scale with 5 m

contour interval fixing the

bench marks in an interval

of 500 m including details

of cross drainages

Update and upgrade

design flow parameters

for power generation,

structures, design flood

and flood levels,

diversion flood and FDC

Excavate test pit to collect

samples for laboratory

analyses to know nature of

soil and its profile at

intake, desander and

powerhouse site

Conduct socio-economic

survey with the

information of land use

and land cover for socio

environmental hazard and

mitigation analyses

Carry out water quality

sampling and sediment

analyses Hardness,corrosiveness (quality)

and quantity of sediments

(PSD and Mineralogical

analyses)

Perform SPT (Standard

Penetration test) and

permeability test in eachtest pit to know strength

and permeability of the

soil/rocks at the major

parts of hydropower

project.

Assess magnitude of

GLOF and its risk if there

are any glacier lakes in

upstream catchment

Identify and investigate

Borrow area (quarry

site)for the construction

materials such as

impervious soils, stones,

gravel and sand

Collect the information

about location, intensity,

magnitude and frequency

of past earth quake records

of greater than 4 rector

scale for determination of

earth quake factor to

design dam and

powerhouse


44/148


6

3.2 Requirements for Hydropower Planning: Use of Flow Duration and Mass curvesEnergy flow diagram, estimation of power potential, Demand and Prediction

3.2.1 Preparation and Use of Flow Duration Curve (FDC)

The flow duration curve is the curve plotted between the percentages of time exceeded

in abscissa and the flow in ordinates. The flow values may be daily, weekly or monthly.

The FDC is prepared by arranging the flows in decreasing order of magnitudes as

ordinates and the percentage of time under consideration in which the flow is equaled

or exceeded as abscissa. The % of time exceedencing is obtained by cumulative sum of

% of time.

Mean Monthly and Yearly Discharge (m3/s) at intake site

Year Jan. Feb. Mar. Apr. May Jun. Jul. Aug. Sep. Oct. Nov. Dec. Year

1983 1.53 1.22 0.98 1.93 4.87 24.66 12.08 12.63 5.42 2.65 1.72 1.58 5.88

1984 1.46 1.14 0.93 1.24 1.96 7.53 21.97 11.76 20.36 5.38 3.32 2.23 6.61

1985 1.66 1.59 1.21 1.27 2.31 4.71 12.64 11.95 12.44 9.66 4.10 2.42 5.50

1986 1.58 1.15 1.01 1.68 2.31 4.51 12.71 9.78 18.04 6.39 2.92 1.82 5.39

1987 1.26 1.06 1.18 1.37 1.95 4.02 18.36 38.76 15.92 8.67 3.76 2.30 8.19

1988 1.60 1.34 1.54 1.39 1.94 3.34 8.12 9.34 16.88 4.53 1.84 1.77 4.47

1989 1.65 1.42 1.39 1.04 2.68 8.73 11.76 9.13 13.51 5.63 2.66 1.97 5.12

1990 1.49 1.51 2.18 3.82 7.52 20.04 18.44 16.76 12.32 6.85 2.11 1.80 7.89

1991 2.23 1.79 1.78 1.87 2.25 8.55 19.09 16.78 15.17 3.54 2.21 1.49 6.40

1992 1.21 1.15 0.89 1.27 2.74 2.92 8.46 6.93 5.58 3.58 2.07 1.48 3.18

1993 1.40 1.09 0.93 1.93 2.17 4.36 8.34 11.38 7.02 4.58 2.88 1.97 4.00

1994 1.45 1.20 1.05 1.60 2.12 4.00 6.87 7.38 5.59 3.57 2.15 1.68 3.24

1995 1.58 1.30 1.08 1.40 2.10 3.80 9.00 13.92 6.65 5.77 3.13 1.78 4.32

1996 2.54 0.93 0.82 0.75 1.56 3.18 13.93 14.31 7.59 3.43 1.55 1.10 4.30

1997 0.75 0.69 0.57 0.97 1.27 7.78 7.46 58.24 46.54 21.15 7.67 3.70 13.04

1998 1.80 1.86 3.67 5.25 4.46 7.65 38.64 25.64 29.66 12.46 3.16 2.05 11.381999 1.76 1.49 1.12 0.92 2.31 16.74 33.75 33.20 28.85 13.66 4.95 3.18 11.84

2000 3.24 2.94 2.01 2.63 6.40 10.64 13.72 16.60 16.55 9.72 5.09 2.52 7.67

2001 1.57 1.51 1.28 1.23 3.81 7.05 10.72 15.13 19.57 20.36 5.36 2.68 7.54

2002 1.73 1.40 1.14 2.26 2.09 5.36 30.75 16.00 15.50 5.44 2.27 1.04 7.14

2003 0.62 0.61 0.77 0.88 0.76 10.59 29.66 17.36 12.41 8.65 2.21 0.69 7.10

2004 1.17 0.75 0.76 0.90 2.59 8.68 23.98 9.88 14.83 9.28 3.48 1.71 6.50

2005 1.06 0.79 0.54 0.79 1.09 2.99 19.38 23.13 10.42 8.00 3.00 0.90 6.07

2006 1.93 1.93 1.75 2.60 2.78 8.25 17.25 13.61 16.90 7.16 1.93 0.76 6.40

Mean 1.60 1.33 1.28 1.71 2.82 8.29 17.31 17.55 15.98 7.92 3.15 2.09 7.05


45/148


7

Example of Preparation of flow duration curve from Mean monthly flow

(/

)

1200

(2

)

%

%

%

%

(/

)

%

(/

)

1.60 17.55 31 8.4 8.4 8.33 8.33 17.55 8.33 18.36

1.33 17.31 31 8.4 16. 8.33 16.67 17.31 16.67 12.71

1.28 15.8 30 8.22 25.21 8.33 25.00 15.8 25.00 8.73

1.71 8.2 30 8.22 33.42 8.33 33.33 8.2 33.33 6.65

2.82 7.2 31 8.4 41.2 8.33 41.67 7.2 41.67 4.02

8.2 3.15 30 8.22 50.14 8.33 50.00 3.15 50.00 2.2

17.3

12.82 31 8.4 58.63 8.33 58.33 2.82 58.33 2.21

17.5

52.0 31 8.4 67.12 8.33 66.67 2.0 66.67 1.82

15.

81.71 30 8.22 75.34 8.33 75.00 1.71 75.00 1.54

7.2 1.60 31 8.4 83.84 8.33 83.33 1.60 83.33 1.24

3.15 1.33 28 7.67 1.51 8.33 1.67 1.33 1.67 0.7

2.0 1.28 31 8.4 100.00 8.33 100.00 1.28 100.00 0.54

365 100.0 100.


46/148


8

The FDC curve prepared from mean monthly flow are not precise or accurate than that

was prepared from mean daily flow data since there was considerable variation in mean

daily flow within each month and range is higher in wet season flow. The range of

difference of flow in FDC derived from monthly data may be in the range of 5 to 15%

with the flow in FDC derived from mean daily data depending upon the characteristics

of stream. The difference between the daily and monthly flow duration curve will be

negligible for a stream with steady flow but much greater for very flashy streams.

Calendar Year Basis FDC: Average flow is computed for each day, week or months

from large numbers of years to compute long term average mean flow in a year. The

Long term mean flow is used to plot FDC against the time exccedence based on the

calendar.

Total Period Basis FDC: Flow rates for the entire period under consideration

(irrespective of the calendar year in which they occurred) are arranged in increasingand decreasing order of magnitude. The FDC is then prepared using the flow rates for

the entire period. The total period basis FDC gives true or realistic FDC as the actual

flow rates appear at appropriate place in the curve.

Uses of FDC

The FDC is generally used to determine the installed capacity, firm energy and

secondary energy that can be produced from Hydropower project.

The FDC is also used to plot the power duration curve. The power duration curve is

prepared by multiplying the ordinate of the FDC with the constant value equivalent to

H of the power project.

FDC can also be used for checking the sufficiency of the available water to with draw

Q continuously.

FDC relates the flow rate with duration but it does not give sequential information

regarding the flow. FDC are no use where time sequence of flow is important.

Numerical Example:

#1) Calculate the installed capacity. Firm power, firm energy and secondary energy that

can be produced from a hydropower project at following conditions:

Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Flow Q

(m3/s)

1.80 1.50 1.20 1.10 2.30 6.00 8.50 15.00 13.00 .00 3.50 3.00

A) Design discharge is Q40B) Gross head of the power project is 75 m with conveyance efficiency of 85%C) Electromechanical efficiency of 0.80D) Minimum release at downstream to maintain ecosystem is 0.1 m3/s

#2)calculates the minimum volume of the water that needed to be stored in pondage if the firm poweris needed to increase corresponding to the 3 m

3/s flow.


47/1

hydropower

Documents