Inversin R. Allen Micro-hydropower Sourcebook

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Wrebalys

118

Penstocks

124

Materials

124

Sizing penstock pipes 125

Selecting pipe diameter 125

Selecting wall thickness 133

Expansion joints

136

Support piers, anchors, and thrusthlocks 138

Support piers 138

Anchors 140

Thrustblocks 144

Reducing the forces acting on a structure 145

Conditions for stability 146

Air valves

147

Powerhouses

150

Other components 154

Gates and valves

154

Stoplogs 154

Sliding gates

155

Gate valves

158

Butterfly valves 159

spillweys 159

Overflow spillways 160

Shaft spillways 166

Siphon spillways 161

nashracks and skimmers

162

%ashracks 162

Skimmers

165

Settling basins

166

QI.

TURBINES

Introduction

171

Basic theory 171

Ihrbine types

173

Pelton turbines 173

Basic relationships 174

Fabrication 175

Cost-reduction approaches 176

Errgo turbines 177

Basic relationships

177

Fabrication 177

Cost-reduction approaches 178

Cmssflow turbines

178

Basic relationships

180

Fabrication

180

Cost-reduction appmaches

182

Francis turbinas 182

Propeller turbines

182

Fabrication 184

Cost-reduction appmaches

185

Waterwheels

185

Pumps as turbines 185

Basic relationships

187

Miscellaneous 187

Watercurrent or in-stream turbine

187

Schneider engine

189

Segner turbine

189

Marine thrusters 189

‘fhrbine specifications 189

Turbine performance under new site conditions

191

Options for coupling 192

Direct coupling

192

17l

Belt drives

193

Flat belt?

193

V-belts

193

Timing

belts

194

Chain drives 194

Gear boxes

194

VII. HYDROPOWER:

ELEcrRIcfu vs. -CAL

Introduction

195

Ihints

of comparison

195

Impact on plant’s financial viability

195

Cost and sophistication

196

Energy conversion losses

197

Restrictions on the

size

of motor loads

197

Versatility

198

%anf3mission of power

198

VIII. GOVERNING

Introduction

199

Purpose of governing

199

why consider various governing options?

200

Extent of governing required 200

Heating loads

201

Lighting loads

201

Tkansformen

201

Motor loads

201

Approaches to governing

201

Couvclntional approaches 202

Oil-pressure governor

203

Mechanical governor

203

Load controller 208

Phase control

205

Step ballasts

205

Nonconventional approaches

205

Constant loads

207

Manual control

207

Fiow modification 208

Load modification 209

Large base load

209

Operation on the backside of power cm

210

Operation in parallal with dissipative load

211

‘lhrbine flow modification

213

xii

ELECTRICAL AGPECI’S

Introduction

217

v9.

217

Magnitude of power generated

217

Storage of energy

217

Cost and complexity of system

217

Convenience

218

lransmission of power

218

Inverters

218

Singlt+ vs. three-phase

219

Electrical equipment

219

Generator

220

?frpe of generator

220

Voltage

220

Frequency

220

Power rating

220

Speed

222

Physical characteristics

222

Monitoring and protection equipment and switchgear

223

195

199

217

Monitoring equipment 223

Switchgear 223

Protection equipment 223

CASE STUDIES

225

Introduction 225

Private-sector approach to implementing microhydropower schemes in Nepal

226

Immduction 226

Background 226

Butwal

226

Program history 227

llsdmical designs 229

Selection of turbine type

229

7brbine design

230

Design of a typical mill :installation

231

Installation teams

233

Installation of a mill

234

Site selection

234

Site layout

235

Quote for the installation

236

Design, fabrication, and delivery

23?

Installation

238

Design modifications

240

costs 240

Other developments

241

Hardware

241

Mechanical heat generator

241

Heat storage cooker

242

Mill lighting

243

Cooperative approach to implementation

245

Observations

246

End uses and viability of microhydropower plants

246

Appropriateness of micro-hydropower technology

247

Villagec4mplemented micro-hydropower schemes in Pakistan

248

Introduction

248

Background

248

Implementation and cperation

249

‘IBchnical designs

252

Civil works

253

Intake area

253

Power canal

253

Forebay

254

Penstock

254

Powerhouse

255

lbrbo-generating equipment

256

‘Ihrbine

2S6

Generator

257

Governing

257

Distribution

258

costs 258

Observations

259

Expanding the scale of the program 259

Increasing the capacity of the plants

260

Benefits to the rural sector

261

Replication in other countries

261

Implications of design on long-term costs

262

Other project descriptions

263

A.PPENDKEs

A. Conversion factors and constants

265

B. Significant figures

267

C. Guide to field determina?ion of soil type

269

265

. . .

Xl11

xiv

D. Prepuring concrete

270

E. Masonry

272

E Water hammer

274

REPERENCES

INDEX

277

263

I. INTRODUCTION

NEED FOR ENERGY FOR RURAL DEVELOPMENT

In manjr developing countries, development activities

have been concentrated primarily in the urban or more

accessible areas, where the greatest number of people

can be served with t.he minimum effort and expense.

However, by far the largest percentage of the popula-

tion lives in rural areas. Because these people are more

thinly dispersed, frequently live in areas more difficult

to reach, are less vocal than their urban counterparts,

and have less disposable income, they have been

deprived of the benefits available to those in the urban

areas that result from these development activities:

e extension and improvement of transportation and

communications networks;

a provision of electricity and water and their asso-

ciated benefits;

e construction of schools, hospitals, and clinics;

o increased employment opportunities; and

a access to agricultural and health extension services.

From an iudividual’s point of view, the easiest means of

acquiring these amenities is to migrate to the towns and

cities, where he then also contributes to both mounting

urban problems and a dwindling agricultural base.

Addressing these issues places an additional demand on

limited resources, which often represents a net loss to

the nation and a reduced quality of life for its popula-

tion as a whole.

An energy source that can be viably implemented in a

rural setting would contribute to the attractiveness of

the rural areas. Electric power wuuld encourage the

establishment of government offices and associated ner-

vices; provide an incentive for better trained persons to

serve in the more remote areas; improve the quality of

educational, health, and other services; and enable indi-

vidual rural households to have access to amenities

which were formerly restricted to urban areas. An

affordable source of electrical as well as mechanical

and thermal energy could encourage the establishment

of agro-processing and cottage industries, which would

contribute to employment opportunities in rural areas,

increased disposable income, and a decreased drain on a

nation’s foreign exchange spent or importing agricul-

tural products.

Significant water resources are found in many develop-

ing countries. In areas where adequate water resources

are present, harnessing the power of falling water by

means of micro-hydropower plants is one way of provid-

ing affordable energy for the development of rural

areas.

MICRO-HYDROPOWER: AN APPROPRIATE ENERGY

SOURCE

Micro-hydropower has several advantages in common

with large-hydropower schemes:

o It relies on a renewable, nonpolluting, indigenous

resource that can displace petroleum-based fuels

that are frequently imported at considerable expense

and effort (Fig 1.1).

Fig. 1.1. Despite the

expense and

difficulty of tmnsport-

ing

fX?l to remote areas,

the

availability

and knowledge

internal combustion

engines

frequently lead to their use

even though

hydropower

can be harnessed nearby.

. As a component of a water development scheme, it

can be integrated with irrigation and water-supply

projects to maximize the benefits while sharing the

cost among several sectors (Fig. 1.2).

e It is a well-proven technology, generally well beyond

the research and development stage. In addition,

hydropower resources have already been harnessed

for years by rural entrepreneurs and farmers in

numerous Asian, African, and Latin American coun-

tries (Fig. 1.3).

Micro-hydropower technology also has a number of posi-

tive attributes not usually associated with large-hydro-

power plants. One is that, because of their size, micro-

hydropower schemes permit local villager involvement

in the full range of activities, from initiation and

implementation to operation, maintenance, and man-

agement (Fig. 1.4). When villagers contribute labor and

local materials, the costs incurred are lower, and when

villagers are committed to a properly planned and exe-

Introduction 1

Fig. 1.2. This micro-hydropower plant

integrated with

irrigation

scheme,

using excess water to genemte

power

for a

nearby town, thereby displacing

the diesel fuel

that

would otherwise be

used.

cuted project, the possibility of its long-term success

increases significantly.

In addition to generating electric% micro-hydropower

--.

plants permit the generation of mechanical energy,

which can be used to power agro-processing machinery

or cottage industries directly (Fig. 1.5). This permits

the use of a less complex technology, which in turn is

both less expensive and more easily understood. The

increased efficiency of direct conversion to mechanical

power, rather than using a generator and then motors to

provide it, means that up to twice the useful power is

available from a given turbine, depending on the size of

the plant.

Another attribute is that the small size of individual

Fig. 1.3. Water falling about 5 m through an

open

flume to

a Pelton turbine built of wood provides sufficient

power to

saw timber. Examples of

such

locally designed, b::ilt, and

2 Introduction

Fig. 1.4. Micro-hydropower projects permit significant

villager incwlvement in all phases of the work.

plants creates widesEead potential for micro-hydro-

power schemes in terms of the number of sites which

can be exploited. Sites for large schemes are relatively

few, and the energy generated has to be transmitted

over larger distances to serve the end users. The eco-

nomics of power transmission implies that the large

quanti”.ies of power generated by large plants must be

restricted to the few load centers that can most readily

use it-cities and larger towns. The decentralized

opemted micro-hydropower plants

are

found in a number

of countries

throughout the world and have

often been in

use for generations.

Fig. 1.5.

Women

in rumf areas spend numerous hours per-

forming tedious, strenuous, and energydemanding tasks

such

milling grain for domestic consumption. Such

areas need mechanical more than electrical energy. The

nature of micro-hydropower resources coincides more

closely with the dispersed nature of rural populations; it

permits energy

bc genrratcd near where it is to be

used, leading to reduced transmission costs (Fig. 1.6).

Several types of turbines commonly used with micro-

hydropower schemes lend themselves to sim& designs

and fabrication techniques, which in turn<ncocrage -

their local manufacture (Fig. 1.7). Because the turbine

can bc one of the more expensive components of a

micro-hydropower scheme

, considerable savings are pos-

sible if locally fabricated equipment is used. Efficiency

is not necessarily a major consideratio.1 if adequate

water resources are available which they often are;

neither is the need for high-quality and long-lasting tur-

bines if turbinrs can easily be repaired locally. In addi-

tion, designs for turbo-generating units vary widely

MPPU manufactured

in Nepal (p. 1781, here shown per-

forming

the same task performed by the

woman at

the

left,

primarily addresses

these

needs, although electricity

can

also be genemted

desired (see Fig. 7.3).

depending on their end use, from systems incorporating

only a generator with no governing or speed control

devices to stand-alone, fully automated systems gener-

ating utility-grade power.

Whereas large-hydropower schemes incorporate massive

dams and major civil works, relying heavily on steel and

concrete, a wide rangeof designs and materials for the

civil works components is possible for micro-hydropower

schemes (Fig. 1.8). Dams are rarely used, and the civil

works for numerous schemes have been built with sev-

eral bags of cement as the only material imported into

the area.

Finally, large-hydropower schemes, primarily because

they impound a large body of water behind a dam, can

have a variety of adverse impacts on the surrounding

Fig. 1.6. Micro-hydropower is one

the

few

means of providing

useful

amounts

energy to remote communities.

Introduction 3

area: flooding of arable land; social dislocation;

increased incidence of certain diseases; and decreased

fish populations. because micro-hydropower schemes

involve move modest undertakings and seldom require

dams, social and environmental concerns are rarely

raised.

PERCEIVED OBSTACLES TO VIABLE MICRO-HYDRO-

POWER SCHEMES

With all the apparent advantages of micro-hydropower

technology, one may question why it has not found more

widespread acceptance. There are several reasons.

Over the years, engineering firms and implementing

agencies have gained considerable experience in design-

ing and constructing large-hydropower projects. As

interest in harnessing small-hydropower resources has

grown, some of these groups have been employed to

implement smaller schemes. Rather than considering

the unique aspects of small hydropower and their impli-

cation on plant design and construction, these groups

often have simply scaled down their more conventional

designs and construction techniques. The increased cost

of smaller project which results from economies of

scale and the lack of cost savings otherwise possible

through the use of nonconventional materials, designs,

and construction techniques for small schemes are fac-

tors which have given micro-hydropower plants the

reputation of being excessively expensive. Fortunately,

a growing awareness of this problem and of more cost-

effective designs and approaches to construction make

micro-hydropower developments a more attractive

alternative.

Three other factors have reduced the attractiveness of

micro-hydropower:

e The significant cost and sophistication of the turbo-

generating equipment have been a barrier. Until

Fig. 1.8.

These

two

schemes,

which each generate

5-l 0

kW, illustmte the

range of

design

options possible to

those implementing

micro-hydropower projects. A portion

Fig. 2.7. Simple turbine designs

encoumge local

fabrica-

tion

and

repair

of equipment.

recently, only firms primarily invoiced in manufac-

turing equipment for large-hydropower plants have

produced such equipment. High overhead costs, the

conventionai approach to equipment desrgn, and eco-

nomies of scale have resulted in relatively high costs

for micro-hydropower equipment. However, the

number of small entrepreneurs specializing in the

manufacture of small turbo-generating equipment in

both industrialized arId developing countries has

grown, leading to significant ccst reductions.

m Government agencies now implementing small-

hydropower schemes have been responsible for the

generation, transmission, and distribution of electri-

city on a national scale. To these agencies, con-

structing smal!-hydropower plants drain large

resources for a relatively small contribution to the

national electricity supply. Their lack of motivation

the power canal,

foreboy,

and powerhouse are visible in

both schemes. The penstock to

the

plant at the

left is

buried.

4 Introduction

for implementing such schemes has increased their

inefficiency, resulting in further increases in the

effort and cost of installing small plants.

The high costs and difficulties of central government

agencies operating and maintaining plants in remote

areas further discourage the development of these

plants. Reducing the staff for a 30 kW plant in

Nepal to 14 may be a step in the right direction but

one

person

selected from the village who would be

backed up by technical assistance from a regional or

central agency when needed would be a more appro-

priate staff for such a plant. AlthouGh high staffing

costs is another factor which contributes to the

impression that micro-hydropower plants ar++ inap-

propriate, the problem is with conventional govern-

ment approaches to implementation and operation of

small-hydropower plants and is not intrinsic in the

technology. In Papua New Guinea, for example,

several private plants with capacities of up to

100 kW are run with the part-time inputs of a single

person.

It is increasingly recognized that the development of

micro-hydropower schemes holds out more promise for

contributing to rural development than for significantly

increasing a nation’s indigenous energy-generating capa-

city. If the government is to implement such schemes,

their effective implementation requires that the

government agency involved in rural development,

cooperatives, small industries,

possibly agriculture,

rather than that involved in the power sector should

take on the responsibility. The government of Burundi,

for example, has placed the development of small-

hydropower plants under the Ministry of Rural Devel-

opment. Governments might also find it beneficial to

encourage active private-sector involvement in this sec-

tor. For example, whereas the government of Nepal has

encountered high costs for implmementing and operat-

ing micro-hydropower schemes, a number of private

companies have demonstrated their ability to cost-

effectively implement micro-hydropower plants to

directly drive agro-processing equipment and generate

small quantities of electrical power. Because of these

experiences, His Majesty’s Government recently ruled

that private individuals are now free to generate and

sell electric power generated by their micro-hydropower

plants. The United States, where the national grid is

well established, provides another example of where

legislation mandating that utilities purchase any power

offered to them has significantly encouraged the cost-

effective development of small-hydropower resources

by the private sector.

There are numerous examples from around the world

which illustrate where the apparent obstacles to effec-

tively implementing micro-hydropower schemes have

been overcome. These highlight the fact that this is

possible and that there is a need to consider alternative

approaches to implementing and managing such schemes

in order that indigenous waterpower resources can be

harnessed to contribute most beneficially to the devel-

opment of the rural areas.

OVERVIRW OF THE MICRO-HYDROPOWER SOURCE-

BOOK

Although micro-hydropower technology has the poten-

tial to make a significant contribution at an acceptable

cost, the factors summarized above have discouraged

the widespread development of this technology. The

purpose of the Micro-Hydropower Sourcebook is to

address primarily the technical issues encountered in

the planning, design, implementation, and operation of

micro-hydropower plants. However, numerous other

factors, some mentioned above, must be considered

carefully if a successful micv:o-hydropower plant

pro-

gram is to be implemented.

An essential requirement for hydropower generation is a

stream with a combination of adequate head-the drop

in elevation-over a reasonable reach of the stream and

adequate flow to meet the expected demand for the

power to be generated. The Sorrcebook therefore

begins with the chapter, Ikll@?URING HEAD AND DXS-

CHARGE, which describes a range of methods for

measuring these two parameters which is sufficiently

broad to address most situations.

Although the head between any two points at a specific

site remains unchanged over time, the same cannot be

said of flow, the other critical parameter. Flow is

affected by several factors, primarily precipitation, but

also geological features, the nature of the soil, vegeta-

tion cover, agriculture practices, temperature, and

land-use patterns in the catchment basin. Measuring

flow at one po:nt in time is of little use in planning for a

hydropower pla*+ because that flow may not be tepte-

sentative of the flow available most of the time. The

chapter, STRRAMFLOW CHARACTERISTICS AND

DESIGN FLOW. reviews methods of teducine flow data

gathered over a period of time to forms whiih can be

used to size turbines and predict the effect of flow

variations on the power and energy genemted over the

year. Because few streamgaging data are available at

most micro-hy&opowet sites, several methods for pre

dieting flow characteristics at an ungaged site are also

described.

Now that the reader has been introduced to techniques

for measuring both head and flow, the next task is to

prospect for a potential site. This means selecting a

site with sufficient head so that the available flow can

meet projected power needs. Although a plant might be

located at the base of a waterfall, it is mote likely to be

found along a stream such as that shown in Fig. 1.9. In

selecting a site, it is essential to undersand the options

for laying out a hydropower scheme and the features to

look for in locating the intake and powerhouse along the

stream. These are described in the next chapter, SlTR

SRLRCTION AND RASK LAYOUT. At the end ofthis

chapter, examples ate presented which illustrate how

and why some existing hydropower plants

were

laid out

as they were.

Once the site has been selected and the basic layout

prepared as described in the previous chapter, it is

Introduction 5

FL@ 1.9. A typical ccuntryside where a small-hydropc

bwer plant might

be located to exploit

drop

in c.ievaZion “Hg’?

necessary to develop the scheme in detail. The CML

WORKS chapter first describes the function of all the

possible basic components-dam or weir, intake, power

conduit, forebay, penstock, powerhouse, and tailrace-

which might be included in a micro-hydropower scheme

to help identify which of these components are neces-

sary and which should be excluded. The chapter then

analyzes the design of each component, including basic

dimensions, alternative materials, and design configura-

tions that have been used at existing sites. Other com-

ponents--spillways, settling basins, trashracks and

skimmers, ‘and gates and valves-are included in the

design of several basic components. Spillways, for

example, can be included in a dam, intake area, or fore-

bay. These components are therefore described sepa-

rately toward the end of this chapter.

The civil structures convey water to the turbine in the

powerhouse where the power carried by the water is

harnessed. For the generation of electricity in the

micro-hydropower range, this equipment-turbines,

generators, governing devices, and associated electrical

equipment-is often purchased as a packaged unit. This

unit can be considered a “black box”-a box containing

an assort.ment of electrical, mechanical, and hydraulic

devices into which water is fed and out of which elec-

trical power is drawn (Fig. 1.10).

From a technical point of view, someone purchasing a

packaged unit does not need to know what components

are included within this black box or to understand how

each functions; the purcha.ser simply specifies the head

6 Introduction

INPIIT:

flow

head

Other factors

possibly

influencing the choice of

equipment:

qunlity of water

site accesslbiltty

climatic

conditions

altitude

variability of flow

penstock configuration

nature of load

method of operation

powerhouse size

etc.

OUTPUT: ac or dc

voltage

I requency

number of phases

Fig. 1.10. A packaged turbo-generating unit can be consid-

ered

a “black box.”

The

site developer specifies the

desired input and output values and other constmints, and

the equipment

supplier selects

the

appropriate “box” to

satisfy those criteria.