Small Hydro Plant Installation and Performance

Case Studies


Scientific Study, 2017
91 Pages, Grade: Post Graduate

Excerpt

Table of Contents

Chapter 1 Introduction
1.1 Importance of Electric Power plants
1.2 Energy Sources
1.3 Renewable Energy Scenario in India
1.4 Small Hydro Power Scenario
1.5 History of Small Power in India
1.6 Small hydro – The Concept
1.6.1 Run-of- River Scheme
1.6.2 Canal based Scheme
1.6.3 Dam toe Scheme
1.7 Component of small Hydro power Scheme

Chapter 2 Hydro Mechanical Equipment of SHP station
2.1 General
2.2 Hydro turbines
2.2.1 Classification of Turbines
2.3 Governing System
2.3.1 Performance Characteristics of Governor
2.4 Gates and valves
2.4.1 Types of Gate
2.4.2 Types of Valves

Chapter 3 Literature Review on performance of Hydro Mechanical Equipment
3.1 Work done by previous Researchers
3.2 Testing of Hydro Mechanical Equipment
3.2.1 Purpose of Testing
3.3 National & International Standards and Codes for Testing

Chapter 4 Methodology for Performance measurement and analysis of Hydro Mechanical Equipment
4.1 General
4.1.1 Turbine Model testing
4.1.2 Procedure of testing for turbines in Laboratory
4.1.3 Field Testing of Prototype
4.1.4 Testing of Governor
4.1.5 Testing of Valves
4.2 Efficiency Measurement
4.2.1 Head measurement
4.3 Speed Measurement
4.3.1 Direct Contact
4.3.2 Indirect Contact
4.4 Power Measurement
4.4.1 Direct Contact
4.4.2 Indirect Contact
4.5 Temperature Variation
4.6 Discharge Measurement
4.6.1 Current Meter Method
4.6.2 Pitot Tubes
4.6.3 Pressure Time Method
4.6.4 Acoustic Method
4.6.5 Electromagnetic Method
4.6.6 Ultrasonic Method
4.6.7 Tracer Method
4.6.8 Transit time Method
4.6.9 Weir Method
4.6.10 Float Method
4.7 Efficiency Measurement
4.7.1 Absolute Method
4.7.2 Thermodynamic Method
4.8 Characteristics and performance of hydro turbine
4.8.1 Main Characteristics Curve
4.8.2 Operating Characteristics Curve
4.8.3 Constant Effective Curve

Chapter 5 Case Study
5.1 Loharkhet SHP
5.2 Gangrel SHP
5.3 Birsinghpur SHP

Chapter 6 Results and Findings
6.1 General
6.2 Design Head
6.3 Power Potential studies
6.4 Installed capacity
6.5 Comparison graph at sites with measured and guaranteed by vendor
6.6 Results of variations in tabular form

Chapter 7 Conclusion & Future scope
7.1 Conclusion
7.2 Future scope

References

Photographs of Loharkhet SHP

Photographs of Gangrel SHP

Photographs of Birsinghpur SHP

Chapter 1

Preface

Energy is one of the most important inputs in the process of development. It is the most important universal measure of all kind of work by human beings and nature. Small hydro power is one of the mostly used methods for energy production being non- consumptive, no radioactive and non- polluting use of water resources and ideal for development areas which are located in remote and far off places from national grid. In recent years the necessity of carrying out performance and evaluation of small hydro power (SHP) plants has been felt globally and initiatives have been taken in countries to address this need. In India, performance testing is a prime-requisite to get subsidy for new SHP stations from the government. The tests are to be carried as per the provision of the International Standard IEC: 60041(1991) and guidelines of Government of India. This book emphasizes the important detail of the performance testing and evaluation carried out on three SHP’s located in three different states of India. Attempt has been made to carry out performance & evaluation of small hydro power plants at different sites. The various aspect of performance & evaluation of SHP plants are studied & described in this book for components, equipment specification & its characteristics. In this book various means of field testing of hydro mechanical equipment are also discussed and testing has been done on site and their characteristics curves are drawn. The various other findings were also made like the variation of turbine performance at present site and the guaranteed performance by the vendor.

In the Loharkhet Site, it was observed that tail race channel can be down 10 m more, which would increase the head available for power generation. From the availability of10m head, we may reduce the losses of 2.44 million units. The difference loss also seen in actual power guaranteed to be produced by turbine range from 2.25 to 3.28 Million units. Apart from this transmission losses were 1.6% from the site. In addition to the above findings an additional unit of 2.5 MW may also be proposed at the existing site of the Loharkhet power station at Uttaranchal based upon the hydrology discharge data of the 7 years into consideration. In Birsinghpur Site, difference in actual power guaranteed to be produced by turbine ranges from 12.73 to 15.924 Million units for the head of 40m. The plant also incurred the loss of leakage of water from penstock & loss in power ranges from 13.4MW/year to11.17MW/year for 60m & 50 m head respectively. In Gangrel Site, this is an irrigation based site. The power production from site depends upon the amount of water required for irrigation purpose. Therefore, the utilization factor of plant is low. Difference in actual power guaranteed to be produced by turbine ranges from 26.2 to 37.42 million units.

Introduction

1.1 Importance of Electric Power Plants

Low cost and abundant supply of electric power is the major factor in the development of country. It is not possible for all consumers to have access to the electrical power available from the main power plants. Sometimes it is not worthwhile for the small isolated customers to afford the transmission and maintenance cost, even if connected to the main power. Until the year 1970’s an ideal way to produce small amount of electrical power was to use diesel or gas engine driven generators. But with the high increase in the energy consumption, price of diesel, gas and other pollution-related effects towards environment also rose. It was then that consideration of utilizing natural energy available from Sun, Wind, Stream, Small waterfalls came into existence which are more economical, provided that small and Low cost device can be made. In many areas where it is difficult to build thermal power station and supply to nearby place by a substation causes large transmission losses, small hydro plants are good alternative subject to availability of natural resource.

Energy may exist in many forms. Hydraulic energy, that which is possessed by a fluid, is a clean energy source. Without consuming the source, it only uses the water, which, after use, can be used for other purposes. Conversion of potential energy possessed by water into mechanical energy could be carried out with a high efficiency. Such technology, using hydro power, provides significant savings on exhaustible sources of energy. It may exist in any form of kinetic, pressure, potential, strain or thermal energy. Mechanical energy is that which is associated with the moving or rotating parts of machines, usually transmitting power. Machines utilizing hydraulic energy, with output in the form of a rotating shaft or a moving part of machine are known as hydraulic turbines.

1.2 Energy Sources

Sources of energy means material objects that contain energy in usable quantities. Energy is conventionally classified into such forms as chemical, mechanical, electrical, nuclear etc. Of the great variety of natural energy sources, those used in quantity to meet practical needs are referred as main or major sources. The major sources of energy are as follows:-

a) Fossils Fuels: Fossil energy is generated through the burning of fossil remains. At this burning the fossil fuel is used as a source of heat to make steam out of water. Examples of fossil fuels are oil, natural gas and coal. These fossil fuels are remains of dead materials of plants and animals. These plants and animals died over a million years ago and under the pressure of the earth's surface and through the decay of this material their came a process of compression with Carbon being the main part of these fossil fuels.

b) Nuclear power: Nuclear power is a form of energy which arise from a reaction within atomic nuclei. Mostly this form of energy comes out of nuclear fission. Atomic nuclei exist out of neutrons and protons. These little parts (neutrons and protons) are held together in the center of the atomic nucleus through binding energy. In a process where in atomic nuclei collide with each other, they fall apart and the loose parts come out of the atomic nucleus.

c) Alternative energy:- Alternative energy is a form of energy without waste-matters. It is also a form where the source, which delivers the energy, is endless. Some alternative energysources are sun, water and wind energy. Using these forms of alternative energy, electricity is produced. For instance, a hydro-electric station makes use of the fall between a lake and a river by building a flood control dam between the lake and the river. In one outlet of the dam, a turbine is installed. This turbine activates a generator and the water energy is transformed into electric energy.

1.3 Renewable energy Scenario in India

Indian Government has accorded very high priority to develop and expand installed capacity base through non-conventional sources of electricity generation. There is a separate Ministry of Government of India to exclusively focus on this important area of power generation. National electricity policy notified in 2005 in pursuance of Electricity Act, 2003, prescribes that state Electricity regulatory commissions should be produced and supplied to the grid through the non-conventional sources. Some of the regulatory commissions have come out with specific policy guidelines with a different approach on tariff for these plants in order to encourage these technologies and plants. National Electricity tariff Policy mandates that State Commissions should fix such minimum percentage. India has very high potential for these capacities.

Table 1.1 Non - Conventional Energy Sources

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1.4 Small Hydro power Scenario

The per capita consumption in India is only 606KWH per year which is much below even the average per capita consumption of the world which is 2400KWH per year. In our country, where there are many small villages, which are situated near the banks of the stream where a head of 10 m can easily be trapped with is sufficient flow available especially during the time when power is most needed. Although the cost of the electricity is not too high, but the cost of transmission of the power from the main power station to the localities is too high. This apart, there are too many transmission losses incurred in the due process. Because of this, it is feasible to construct a small micro hydro turbine which is of less cost and could be manufactured and installed easily.

1.5 History of Small Hydro power in India

In India, the history of hydropower is as old as 110 years. The first small hydro-power project of 130 KW, in 1897, was erected and commissioned in Darjeeling. This was followed by Sivasamudram project of 4500 KW, another SHP project in 1902 in Mysore, Karnataka. Following this, numbers of small hydro projects were setup in various hilly areas of the country. Till Independence (1947), the country had an installed capacity of 1362MW, which included 508MW hydro projects, mainly small and medium size projects. A planned development of hydropower projects in India started only in post independent era. The focus was laid on large-scale power generation through big hydro, thermal and nuclear route. First 50 years after independence saw a capacity addition of 85019 MW including 21644 MW of hydropower stations, most of them were being large hydro. Since the development was mainly in the central sector and state electricity boards (SEBs) were more or less tuned to the central planning system, relatively less importance was given to small projects. In late 80s it was realized that the development of small hydro power (SHP) potential has remained largely untapped as the focus was on large-scale power generation. Small Hydro power projects in India can be broadly categorized as: Small hydro projects in the hill, where small streams are available. These are mostly of medium/high head utilizing discharge. The water is diverted by the weir and intake, is conveyed to the fore-bay, at the entrance to the penstock. The penstock conveys the water to the turbines in the powerhouse to generate electricity. These projects may be further categorized as run-of- river schemes and dam based schemes. Small Hydropower projects in the plains and other region of the country, which utilize water regulated for other purpose like irrigation or drinking water canals, small dams etc. are usually of low head utilizing large discharge. These projects may be further categorized as Canal based and dam based schemes. The state wise identified hydel sites and potential up to 25MW capacity (as on 31/3/2009).

Table 1.2 Potential of hydro in Different states of India

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1.6 Small Hydro: The Concept

Hydroelectric power is the technology of generating electric power from the potential energy of water through rivers, canals or streams. Water is fed via a channel to a turbine where it strikes the turbine blades and causes the shaft to rotate. The rotating shaft is connected to a generator which converts the mechanical energy of the shaft into electrical energy. Hydro power projects are generally categorized in two segments i.e. small and large hydro power. There is a tendency to define small hydro by power output whose upper limit varies from 5 to 50 MW. This definition varies from country to country. In India, Central Electricity Authority (CEA) classifies SHP schemes as given in the following table:

Table 1.3 Micro, Mini, and small hydro schemes in India [1]

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* CEA, in its publication (1982), defines small hydropower only up to 15MW station capacity. However with the transfer of mandate for hydropower now with the Ministry of non-conventional energy sources upto 25 MW, small hydropower is taken upto 25 MW in India. There is a worldwide tendency of defining SHP output. Countries follow different limits to define SHP, the upper limit ranging between 5 to 50 MW. The following table (Table 1.4) reports the same.

Table 1.4 Worldwide definitions for small hydropower [2]

illustration not visible in this excerpt

Small hydro power projects in India can be broadly categorized in two Categories as:

a. Small hydro power projects in the hills where small streams are available. These are mostly of medium high head utilizing small discharges. The water is diverted by the weir and intake, is conveyed to the fore-bay, at the entrance of the penstock. The penstock conveys the water to the turbines in the power house to generate electricity. These projects may be further categorized as run- of- river schemes and dam based.

b. Small hydro power projects in India in the plains and other regions of the country, which utilizes water regulated for other purpose like irrigation / drinking water canals, small dams etc. are usually of low head utilizing large discharges. These projects may be further categorized as following schemes [1]

1.6.1 Run- of- River Scheme

These are those schemes, in which water is diverted from a stream without creating any storage in the river. In these schemes (eg. Chilla Power Plant, Haridwar, India, Chief Joseph Dam, USA), power is generated from flowing water and available head. The output of run-of-river plant is subject to instantaneous flow of the stream. The layout of a typical run-of-river scheme is shown in Fig. 1.1.

Table 1.5 Classifications Based on Head [2]

illustration not visible in this excerpt

(a) Chilla Power Plant, Haridwar, India (b) Chief Joseph Dam, USA

(Source: http://www.resortsinrajajinationalpark.com) (Source: Wikipedia, Public Domain)

Figure 1.1 (a-b) Run- of river Scheme

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Figure 1.2 Canal Based scheme, Somanamaradi, India (Source: http://www.ahec.org.in)

1.6.2 Canal Based Schemes

Canal Based small hydro power scheme is one which is planned to generate power by utilizing the fall and flow in the canal. These schemes may be planned in the canal itself or in the by-pass channel. A typical layout of canal based small hydro scheme is shown in fig. 1.2.

1.6.3 Dam toe Schemes

Dam toe schemes are those in which water is stored in the river by constructing a dam across the river and power is generated by controlled flow from storage. These are common in India.

illustration not visible in this excerpt

Figure 1.3 Dam Toe Scheme, Nagarjuna Sagar Dam, India (Source: Wikipedia, Public Domain)

1.7 Components of small hydro power scheme

The various components of a typical hydropower scheme are given below:-

i) Diversion and Intake structure-

The Intake to a hydropower scheme should be situated to prevent river borne debris and usually large flows from being funneled into intake, especially during heavy rains. At the same time, there is a need to ensure that an adequate flow of water is diverted toward structure of temporary or permanent construction, commonly called a weir is often constructed across a part or the entire stream. A weir is a structure specially designed to divert the required flow into the intake, not to store water. It might either channel the flow toward the intake or simply provide the required depth of water at the intake for flows enter of its own accord. Where the stream bed is susceptible to erosion weir also maintain the level of the stream bed constant near the intake otherwise the stream bed might erode so badly that the stream eventually will be too low for water to enter the intake.

ii) Fore-bay or Balancing Reservoir

It is a basin located just before the entrance to the penstock. Its size may vary depending on the quantity of the water being conveyed to the penstock and whether it is to serve the storage. In some cases it is virtually non-existent. To be most cost-effective, the fore-bay must be of a size adequate to fulfill its function, neither significantly large nor smaller. It can serve the following purposes; it can serve as a final setting basin where any water-borne debris, which either passed through the intake or was swept into the canal may be removed. It can also be used for storage. The important components in the fore-bay are:

a) Spillway
b) Scouring Gate
c) Gate to the penstock
d) Trash rack

When the flow entering the fore-bay may exceed the flow leaving via the penstock, such as when a gate at the intake has been set improperly or the valve to turbine has been closed on during heavy rains or excess flows enter the canal from stream or from run off uphill of canal, one side of fore-bay might have spillway. Incoming water can carry sizable quantities of floating debris. A trash rack is often included at the inlet to the penstock. Drainage is also required when fore-bay is being repaired.

iii) Penstock

It is a pipe that conveys water, under pressure to turbine, except for some scheme with very low head, such as open-flume Francis and propeller turbines, in-stream turbines and traditional water wheels. It can be installed either above or below the ground. The ones buried, though costly, is prevented from landslides, falling rocks bush fires and tampering. It is not easy for inspection, maintenance or repairs as compared to penstock above the ground when it is subjected to temperature variations. This leads to thermal expansion, which causes stresses in the pipe. Support piers are used for straight lines of exposed pipes, primarily to prevent the pipe from sagging and becoming over stressed.

iv) Power House building

The power house protects the turbine, generator and electrical and mechanical equipment. Its size and configuration depend on function it serves. Conventionally, it is large enough to include this equipment but also a workshop, office and sanitary facilities. For micro-hydro projects, it is enough to have turbo-generating equipment with sufficient space on all sides to permit easy access for installation, operation, maintenance and repair. Power house comprises turbine, generator, inlet valve and other auxiliary systems like cooling water, drainage and de-watering systems, auxiliary power system, emergency and standby power system and equipment, lighting system, instrumentation protection and control system, ventilation system, station grounding, fir fighting equipment etc.

v) Tail Race

It is usually short, open canal which leads the water from the powerhouse back into a stream, generally the stream from which the water came. It is a component of every scheme except low-head plants where the water emerges from a draft tube directly into the stream. It is a short and is located near a stream. The successful implementation of small hydro projects depends on the availability of specific equipment with the required characteristics duly tested and certified, but presently no plan is available nationwide to test the small hydro equipment at site. It is, therefore, necessary to prepare the suitable guidelines for testing of equipment at site under working conditions based on the field experiences.

Chapter 2 Hydro mechanical equipment of SHP stations

2.1 General

Hydraulic machines are those machines which convert either hydraulic energy into mechanical or mechanical energy into hydraulic energy. Machines converting hydraulic energy into mechanical are called Turbines while machines converting mechanical energy into hydraulic energy are called Pumps.

2.2 Hydro turbines

Hydro turbines are defined as the hydraulic machines, which convert hydraulic energy into mechanical energy. This mechanical energy is used in running an electric generator, which is coupled to shaft of the turbine. Thus the mechanical energy converts to electrical energy. The electric power, earned from hydraulic energy is hydraulic power.

2.2.1 Classification Of turbines

In general a water turbine consists of a wheel called runner (or rotor), having especially designed vanes or blades or buckets. The water processing a large amount of hydraulic energy when strikes the runner, it does work on the runner and causes it to rotate. The mechanical energy so developed is supplied to generator coupled to the runner, which then produces electrical energy. Selecting the best turbine for any particular hydro-site depends upon the site characteristics, the dominant ones being the head and flow available. Selection also depends on the desired running speed of the generator or other device loading the turbine.

2.2.1.1 On the basis of the flow regime in the turbine

There are two fundamental mechanisms of converting potential energy possessed by water into mechanical energy in a turbine. Firstly, the pressure of flow applies a force on the runner blade face as the flow proceeds within the turbine. Such turbines are called reaction turbines. In this case, as the runner is fully immersed, the casing should be designed to sustain the pressure. Secondly, water pressure, before entering the runner, is converted into kinetic energy which impinges upon the buckets in the form of a jet. The buckets are mounted on the runner periphery. These types of turbines are termed as impulse turbines. Water, after hitting the buckets, falls into the tail water with little remaining energy due to which the casing design need not be as strong as that of reaction turbines. Impulse and Reaction turbines can be further sub-divided. Impulse turbine includes pelton wheel turbine, cross flow turbine and turgo turbine. In the pelton wheel turbine, the total head available is first converted into kinetic energy. This is virtually accomplished in one or more nozzles. The jets issuing from the nozzle strikes vane attached to the periphery of the rotating wheel, because of the rate of the change of angular momentum and the motion of the vanes, work is done on the runner on the fluid, and thus the energy is transferred.

2.2.1.1.1 Francis turbine

It is a mixed flow type of reaction turbine. It is named in honor of James B. Francis (1815-92), an American engineer who was the first to develop an inward radial flow type of reaction turbine in 1849. It is one having a runner with fixed buckets (vanes), usually nine or more, to which the water enters the turbine in a radial direction, with respect to the shaft, and is discharged in an axial direction. Principal components consist of the runner, a water supply case to supply to convey water to the runner, wicket gates to control the quantity of water and distribute it equally to the runner and a draft tube to convey the water away from the turbines. It can be mounted on the horizontal and vertical shafts. Vertical one requires a smaller plan area and permits a deeper setting of the turbine with respect to tail water elevation locating the generator below tail water. Vertical ones are more costly as compared to the horizontal turbine, because of the large thrust bearing. It is generally provided with a 90* elbow draft tube to minimize head loss.

illustration not visible in this excerpt

Figure 2.1 Francis Turbine (Source: Wikipedia, Public Domain)

2.2.1.1.2 Axial flow turbine

These are those in which flow through the runner is aligned with axis of rotation. These are generally used for net head up to 40 meters head with the power production of 25 MW. S-turbines are used below 30 meters head and 8MW capacity. Bulb units can be used for low head if the diameter is more than 1m. A propeller turbine is one having a runner with four, five or six blades in which the water passes through the runner in an axial direction with respect to the shaft. Pitch of the blade may be fixed or movable. The efficiency curve of a typical fixed blade propeller turbine forms sharp peak, more abrupt than a Francis turbine curve. The conventional propeller or Kaplan (variable pitch blade) turbines are mounted with a vertical shaft. Kaplan turbine was developed by Austrian engineer V. Kaplan (1876- 1934). Suitable for low heads and hence requires a large quantity of water to develop large amount of power.

2.2.1.1.2.1 Tubular turbines

These turbines are horizontal or slant mounted units with propeller runners. The generators are located outside of the water passageway. These are always equipped with fixed or variable pitch runners and with or without wicket gate assemblies. Performance characteristics of a turbine are similar to the performance characteristics for propeller turbines. The performance range of this turbine with variable pitch blade and without wicket gates is greater than for a fixed blade propeller turbine but less than for a Kaplan turbine.

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Figure 2.2 Propeller Turbine (Source: Wikipedia, Public Domain)

2.2.1.1.2.2 Bulb turbines

These are horizontal, which have propeller runners directly connected to generator. It is available with fixed or variable pitch blades and with or without a wicket gate mechanism. Performance characteristics curve are similar to the tubular turbines. The efficiency of this turbine is approximately 2% over a vertical unit and 1% over a turbine unit because of straight water passageway. It requires small floor space but maintenance time is large than tube turbine.

2.2.1.1.2.3 Pit type bulb turbine

In this, turbine is coupled to standard high speeds generator through step up bevel gears are generally used. It has lower efficiency than bulb turbines. Its maximum size is limited to the 5MW to 10 MW to the larger extent.

2.2.1.1.3 Impulse turbine

Those turbines with one or more free jets discharging water that impinges on the buckets of a runner are impulse turbines. Usually, efficiency is around 90 %. In comparison to reaction turbines, the cost of impulse turbines is lesser. These may be mounted vertically or horizontally. However, in case of lower capacity sizes with horizontal mounting and single nozzle units, the additional space requirements compensated by lower generator costs. Lesser floor space is required in case of vertically mounted units and hence are often commissioned for large capacity units with multi-nozzle arrangements. Horizontal impulse turbine is suitable for small hydro applications that have less water discharge available for power production.

illustration not visible in this excerpt

Figure 2.3 Pelton Turbine (Source: Wikipedia, Public Domain)

2.2.1.1.3.1 Turgo Impulse turbine

This turbine is higher in specific speed than the typical impulse turbine. The difference between a pelton unit and a turgo is that, jet enters one side of the runner and exits on the other side of the runner. Head range for this is 15m to 300m. it can be used for production up to 7500 KW. Efficiency is nearly about 82% – 83%.

illustration not visible in this excerpt

Figure 2.4 Turgo Turbine (Source: Author’s own work)

[...]

Excerpt out of 91 pages

Details

Title
Small Hydro Plant Installation and Performance
Subtitle
Case Studies
Course
Mechanical Engineering
Grade
Post Graduate
Authors
Year
2017
Pages
91
Catalog Number
V383457
ISBN (eBook)
9783668610576
ISBN (Book)
9783668610583
File size
2475 KB
Language
English
Tags
Hydro, Plant, Installation, Performance
Quote paper
Shubhankar Bhowmick (Author)Vivek Kumar Gaba (Author)Suraj Kumar Mukti (Author), 2017, Small Hydro Plant Installation and Performance, Munich, GRIN Verlag, https://www.grin.com/document/383457

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