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Development Of Micro Hydro Power Generation Engineering Essay

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Published: Mon, 5 Dec 2016

ABSTRACT

Hydropower is a well established technology which is renewable, sustainable and has been producing power reliably for about a century. Hydro power stations are very sensitive to load variations and can be easily controlled. Hydropower produces about one-sixth of the world’s electricity demand. Typical hydropower turbines operate at an efficiency of 85 – 90%, higher than the efficiency of any other renewable source of energy.

Over the past century several large scale hydropower sites have been identified and many are under operation. These large scale projects constitute the majority of the hydro power produced. Development of new large scale projects encounters constraints with respect for environmental and economic feasibility aspects. This leads to the development of micro hydropower systems which come across as a cheaper and a sustainable source of

energy. Micro hydro power systems are aimed at producing electricity from a few kW up to 100kW.

We look at the possibility of implementing micro hydro power plants in small scale water distribution systems like tube wells and over head community tanks.

Introduction

History of Hydro Power

Hydropower was one of the earliest energy sources to reduce people work load. Early irrigation systems existed at least 5000 years ago of which the Noria was probably the earliest water-power device that rises water for this purpose. The device has evolved in deferent regions of the Middle and Far East. The first water mills were probably the vertical-axis corn mills which seem to have appeared during the first century BC in the Middle East [1].

In later centuries, water mills have developed sophistically and people started using them for other applications which included mining, paper making, iron working and wool industry. The range of efficiencies for the water wheels during the seventeenth century varied from 1 to 60 horsepower [1].

Later on, and as a result of the industry growth the first water turbine was patented by the French engineer Benoit Fourneyron. The turbine was a submerged vertical axis machine which used the guide vanes to direct the water on the blades and increased the efficiency of the turbine.

The potential energy stored in large reservoirs are converted into electricity by the used of turbines and generators. Not only does this result in an emission free power production but also a sustainable source of energy.

The world’s total hydropower generated is about 2593 TWh/year (average over 4 Years 1999-2002. Source BP: 2003).Large scale projects primarily across Asia and South America with production capacities over 1000 MW constitute the majority of the world’s hydropower. The further enhancement of the existing projects or the implementation of new power schemes has constraints both environmental and economical.

National hydro contributions (average over 4 Years 1999-2002. Source BP: (2003)

Hydro power is the most important renewable source of energy worldwide and contributes to 20% of the world’s electricity. China currently has the largest hydro electric power plant with the world with the capacity of 22.5 GW [2].

Source Online: http://en.wikipedia.org/wiki/File:Ren2008.pngRen2008

MICRO HYDROPOWER

Micro Hydropower systems are basically small power sources that are mostly used for individual users or group of users making them independent of the Local power Supplier.

It is one of the most cost effective and reliable source of producing power. Its key advantages include:

It has a high efficiency (e.g. 80 – 90%), the best of all energy technologies.

It has a high capacity factor (typically >50%)

It has a High predictability level, which varies rainfall patterns annually

These systems are durable, such system are designed to last

for more than 50 years.

BASICS OF MICRO HYDROPOWER

Head

Power is obtained from water that is coming from a respectable height that is called “head”. A simple hrizontal flowing water will not provide you with good hydraulic power. So consevation of energy takes place in water coming from a defined Head and resulting in power generation. So the two things that matter the most is Head and Flow. Its better to have a higher Head than high flow beacuase in this way we can make our design small. We don’t include Gross head in calculating power . Gross head is basically the distance between up and down streanm levels. So the turbine only takes the available head that is less than the Gross head and it is called “Net head”

Flow Rate

Flow rate is basically the volume of water passing in 1 second aand it is measured in cubic meter per second.

Output Power:

P = η ρ g Q H

Where :

“P” is the mechanical power “η” is the effeciency

“ρ” is the density of water “g” is acceleration due to Gravity

“Q” is the flow rate “H” is the Head

Classification of Hydropower

Hydropower systems are mainly distrubutes in some categories like small, medium , large , micro, mini according to their power generation.

Classification of Hydro Power

Large Hydro

More than 100MW and feeding into a large electricity grid

Medium Hydro

15MW – 100MW usually feeding into a grid

Small Hydro

1MW – 15MW usually feeding into a grid

Mini Hydro

Above 100kW, but below 1MW, either stand alone systems ormore often feeding into a grid

Micro Hydro

From 5kW to 100kW, usually provided for a small community or rural industries in remote areas away from the grid.

Pico Hydro

From a few 100Watts upto 5kW

Main Elements for Micro Hydropower Scheme

Turbines

Water has potential energy at Head which is converted into Kinetic energy when it comes down through the penstock pipe. That kinetic Energy is than converted into Mechanical Energy by the turbines.

We have to choose turbines according to our design setup which includes Head and Flow. Different turbines are made for different heads available to get the required result. These classifications are given as under:

 

Classification

Head (m)

Characteristics

1

Kaplan

Low Head 1m to 16m

High discharge, high efficiency and cost-effective. Suitable for canals & streams tidal.

2

Cross Flow

Small Head 5m to 50m

Simple Structure, cost-effective

3

Fransics

Medium Head 10 to 150m

Wide application range, good operating stability, high efficiency & medium discharge

4

Pelton

High Head 80 to 1100m

Wide range of high efficiency. Suitable for small discharge

Classification based on Head and Discharge[9]

Turbine Efficiency

Turbine efficiency is the main significant factor in Hydropower Generation. Different turbines have different efficiencies. The Kaplan and Pelton turbines have very high efficiency in contrast to the Cross Flow and Francis turbine. This is represented by turbine efficiency graph below:

Efficiency of Various Turbines Based on Discharge Rate[9]

Penstock Selection

The identification of an optimum pipe diameter for the penstock is essential for the overall performance of the power scheme.

The factors to be taken into consideration are:-

The frictional losses in the pipe: The larger the pipe the lesser is the frictional loss, but larger pipes will cost more.

Dynamic Pressure and Flow Requirements: The dynamic pressure and the flow required for the optimal performance of the turbine will also help in determining the pipe diameter required.

Cost-Benefit Ratio: The optimal pipe diameter is one that given the best cost-benefit ratio i.e. it should have the least cost per PSI of dynamic pressure achieved.

The graph below assumes that the pipeline does not have turns or fittings with a radius larger than 22 degrees and that the overall length is below 500 feet [3].

Pipe Selection from Head and Flow rate Comparison[3]

In cases where the head is low the best solution will be the use of a larger pipe diameter accommodating a larger flow rate for reactive type turbines such as Kaplan and Cross Flow.

For high heads smaller pipes are to be used leading to a high pressure low flow rate condition apt for impulsive turbines like Pelton and Francis.

BACKGROUND

We look at the current utilization, the scope and feasibility of expansion of micro hydro power across the South Asian Subcontinent. The population growth and the industrialization in the South Asian countries has exponentially increased the power requirements of the region. Most of these countries have a significant amount of electricity generated from large scale hydro electric projects.

Given below is a comparative study of the total energy consumption from different sources.

Bangladesh

Bhutan

India

Nepal

Pakistan

Srilanka

Biomass

16.64

0.29

139.30

7.40

23.36

3.58

Coal

0.00

0.01

166.90

0.17

3.30

0.00

Oil Prod.

3.71

0.04

116.00

0.77

15.21

3.01

Natural Gas

8.29

0.00

29.74

27.39

0.00

Hydro Electricity

0.23

0.12

17.69

0.14

6.47

0.83

Nuclear

0.00

0.00

5.33

0.00

0.42

0.00

Total Energy Consumption

28.87

0.46

474.95

8.48

76.15

7.42

Total commercial energy consumption

12.23

0.17

335.66

1.08

52.79

3,84

Per capita (kgoe/y)

89

243

315

44

355

200

Energy consumption of South Asian Countries in million toe[4]

The total hydro power potential of the South Asian countries is much more than what is currently being utilized. Environmental impact, lack of funding, geographical difficulties etc. are some of the major obstacles in the faced in the further development of hydro power. However micro hydro power is relatively untapped in these regions.

Bangladesh

In Bangladesh, hydropower capacity stands at 230MW currently, with the only hydroelectric project being the Karnafuly Hydro Electric Scheme [4]. In 1981, Bangladesh had carried out a survey in order to identify the potential of micro hydro power. The findings of the survey are given below.

Name of river

Potential Energy (kW)

Name of river and site

Yearly Average

Min

Mean

Chittagong

Meghalaya Group

Fiaz Lake

4

Kangsha at Jariajanjail

16.7

274.3

Chota Kumira

15

Sari-gowain at Sarighat

6.4

128.2

Hinguli Chara

12

Sealock

81

Barak Group

6.4

524.4

Lungi Chara

10

Surma at Kanairghat

7.8

545.0

Budia Chara

10

Surma at Sylhet

80.8

660.0

Kushiyara at Sheola

7.2

138.8

Sylhet

Sonai-Bardal at Jaldhup

Nikharai Chara

26

Madhb Chara

78

Tripura Group

Ranga Pani Gung

616

Manu at Manu River Barage

10.4

83.7

Jamalpur

Brahmaputra Group

Bhugai-Kongsa

65.5

Old Brahmaputra at Mymensingh

19.4

704.9

Marisi

32.5

Lakhya at Demra

38.8

629.3

Old Brahmaputra at Bhairab Bazar

4.3

123.3

Summary of Survey Findings [4]

Out of the suitable locations identified there a power scheme was constructed for only one of the sites.

There are also a number of rivers that carry a high discharge during the monsoon months that dry up during the summer. A suitable scheme would involve the construction of diversion structures across rivers, construction of weirs and suitable power houses. The annual output potential from these rivers is estimated at 35kW and the annual energy production at 307GWh [4].

Pakistan

The annual electricity generation capacity in Pakistan is about 19,547MW, out of which 6599MW comes from hydro electric power [6]. The development of Micro Hydro power in the northern parts of the country serves the under developed communities.

The approximate hydro power potential is estimated to be 41,722MW of which only 15% has been harnessed successfully. Given below is the summary of the hydro power potential in various regions of Pakistan [6].

Region

Projects in operation (MW)

Public sector projects (MW)

Private sector projects (MW)

Projects with feasibility study (MW)

Projects with pre-feasibility study/ raw sites (MW)

Above 50MW

Below 50MW

Above 50MW

NWFP

3767.2

635.0

84.0

58.0

143.0

13584.0

Punjab

1698.0

96.0

0.0

3720.0

32.2

0.0

AJK

1036.1

973.1

828.7

420.0

48.2

1152.0

Northern Areas

93.7

18.0

0.0

505.0

71.5

10905.0

Sindh

0.0

0.0

0.0

0.0

49.5

80.0

Balochistan

0.0

0.0

0.0

0.0

0.5

0.0

Summary of Hydro Electric Power Potential in Pakistan[6]

A number of manageable high terrain waterfalls exists in North Pakistan. These areas are sparsely populated and can benefit from micro hydro power. About 300MW of recoverable potential upto 100W each is identified in the Northern waterfalls. Also the low head and high discharge canals present in Punjab can account for about 350MW of power derived from about 300 identified locations.

India

India currently ranks 5th in the world in the availability of usable hydro electric potential at 84,000MW at 60% load factor. But only 25% of this is currently being explored. In 2006, out of the 125,000MW generated 32,325MW was contributed by hydropower [7]. Given below is the basin wise statistics.

Basin

Potential (MW)

Potential Developed (MW)

Potential Under Development (MW)

Balance Potential (MW)

Balance Potential (%)

Indus Basin

19,988

3,731

1,156

14,701

73.55

Ganga Basin

10,715

1,901,

1,361

7,447

69.5

Central Indian Rivers

2,740

1,060

1,147

533

19.45

West Flowing Rivers

6,149

3,704

41

2,404

39.09

East Flowing Rivers

9,532

4,168

144

5,220

54.76

Brahmaputra Basin

34,920

661

1,085

33,175

95

Total

84,044

15,225

5,339

63,480

75.53

Basin-wise potential and status of Development at 60% load factor as of 1st January, 2005 [8]

The potential for micro hydro power is immense throughout India. A number of plants have been set up in the Himalayan region where the rivers are perennial. The current focus in the country is the development of small hydro power plants with capacities of over 1MW. But however the government encourages micro hydro power in the form of various subsidies.

DISCUSSION

Explanatory Data

This is a Micro-Hydropower System which requires no reservoirs like dams, rivers and stream flows. Water from Water Supply Network stored in a tank at a height (Head) is utilized for power generation. The water supply network provides a continuous water supply and such network setups are present in all parts of the world. The generated power is utilized different electric networks. This process of replacement of conventional fuels with renewable energy is very much economical as it eliminates the utility bill payment factor which is a huge concern in today’s world. If we can utilize this technique we can at least save lot of energy so that local supply authority network will not be overloaded or we can shift overload to off-peak so that we can avoid load shedding & over loading of system.

The components used in micro hydropower generation are as follows:C:UsersRHZDDesktopHYDROUntitled.png

System Block Diagram

A. Water supply network

The tube well (or any desalination plant) is used as water supply network of which water from the ground is sucked through pipes using electric motors to supply the storing tank. This water supply network scheme is at ground level and is commonly used everywhere.

B. Overhead tank

An overhead tank at a respectable height, beside the water supply network (tube well) has been utilized for the Head.

The tank will store the potential energy for the purpose. This energy is then converted into mechanical energy by a small turbine. Water from tube will directly go to storing tank through proper channel of supply pipes.

C. Power House Mechanism

The power house design consists of a turbine coupled with a generator at the users premise. Pressure of the water as potential energy has been utilized to run turbine at a specific speed. The turbine runs the generator and produces electricity in a way that power produced could also be supplied to local loads or stored in batteries. Water from the turbines is then supplied to neighboring local bodies.

Two efficiencies are involved here, the mechanical and the electrical. Utility bill is reduced by power house production since the power for running motors is saved by the production of power house and by also supplying back the extra generation to the grid which saves their bill too. So load on the supply authority has been reduced to some extent in this way.

Case Study

Assuming we need to supply a small park and the surrounding with power through an existing setup with a new approach of Hydropower production.

The main power to the park is provided by the local supply authority which has its own water supply network (tube well). Utilizing the present continuous water supply network we will generate the required power. The project will minimize the expense of power consumption by the park and surroundings.

LayoutC:UsersRHZDDesktopHYDROUntitled2.png

Power Requirements

The power generate by the Hydropower plant will be mostly utilized for lighting and fans. A unit of 17.55kW is designed to be installed at the site that shall remain operational throughout the year provided standard operation and maintenance procedure are adopted. The possibility of variation in capacity is subjected to discharge. The power calculations are based on the following assumptions:

Lighting

Energy savers: 250 (each of 48watts)

= 250*48 = 12000 watts

Fans 1 in each shop (95 watt each)

= 95*20 = 1900 watts

Total power consumption = 13900 watts

Total power generated is 17.55kW, whereas, the consumption is estimated to a tune of 13.9kW. The remaining 3.65kW will be accounted for transmission/distribution line losses and future demand.

Numerical Data

Head Range

Hg = 21.219m = 69.6168 ft

Hn = 20m = 65.6168 ft

Discharge

Q = 3.917722cusec

Design Parameters

Power Output = 18kW

Mechanical Components

Dia of Penstock Pipe = 6″

Dia of Runner = 16″

Length of Runner = 3″

RPM of Turbine = 407.46 RPM

Dia of Generator = 12″

Speed of Generator = 1500 RPM

Speed of Turbine = 407 RPM

Dia of Turbine Pulley = 44.176″

Ratio of turbine pulley to Generator Pulley = 3.68133

Control system

Components

Capacity

Qty

Generator

18kW

1

Main Switch

30Amp

1

Ampere Meter

30Amp

3

Volt Meter

500V

3

M.C.B

18Amp

3

Cable

7/.036

1 bundle

Results and Conclusion

The design works in the same way as other hydropower plants but it does not require any reservoirs like dams, rivers or stream flow, instead it utilizes the water supplied by the general water supply network i.e. by the Tube well. These Tube wells are present ubiquitously. Water from this network goes to an overhead tank which is installed just besides the tube well.

Water with a potential at a respectable height flows down towards the turbine through penstock pipe with a respectable flow, for desired output. Cross flow turbines is coupled with the generator and are installed in the power house. Water flowing through penstock pipe starts the turbine which converts the kinetic energy of water into mechanical energy which in turn is converted into electrical energy by the coupled Generator. An electrical panel is also installed in power house which controls and supply the generated power.

The generated power is used to run the motors installed is Tube wells shifting it from local power supply to our hydropower plants supplied power and excess power will be utilized by other electric networks (based on our needs). The outgoing water from turbine is utilized for other domestic purposes. In this way generated power according to design parameters comes out to be 37.8KW with cross over turbine with efficiency of 80 percent , running at 499 rpm, flow rate comes out to be 161 lit/sec. Overall efficiency of network is Civil work is negligible here .

Since power taken by tube well motor is 30 KW (30 horse power). 7 KW power is saved which is utilized for other purposes. Load on local supplier has been reduced. Thus 7 KW power can be supplied to children parks etc and also to batteries for storage.

Future Work

In future the work can be improved much by improving the diameter of pipe through which water flows from tank. Discharge could be improved much further by working on penstock. Also solar energy can be utilized with hydal energy to be independent of power supplying companies for starting motor. Further work could be done to introduce cascading systems of tube wells, motors and also storing tanks. Thus distributed networks of power improve economy as well as removes centralized power supplying policies. Also everyone in the state could be independent of its own production and utilization.


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