Micro Hydro Designing

1

Workshop on Renewable EnergiesNovember 14-25, 2005

Nadi, Republic of the Fiji Islands

Module 4.3 MicroModule 4.3 Micro--HydroHydro

4.3.1 Designing 4.3.1 Designing Tokyo Electric Power Co. (TEPCO)

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ContentsContents

Design (Civil Structure)Weir, Intake, Settling basin, Headrace, Forebay, Penstock, Powerhouse

Head Loss Calculation

Design (Electrical and Mechanical Equipment)Inlet valve, Water turbine, Turbine governor, Power transmission facility, Generator, Control panels, Switchgear

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Types of WeirConcrete gravity damFloating concrete damEarth damRockfill damWet masonry damGabion damConcrete reinforced gabion damBrushwood damWooden damWooden-frame dam with gravel

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Characteristic of WeirCharacteristic of Weir

HighHighHighIntake efficiency

Gentle flow and easy to deal with flooding

Not governed by gradient, discharge or level of sediment load

Not governed by gradient, discharge or level of sediment load

River condition

From earth to bedrockGravelBedrockFoundation

Main material is earth.Riprap and core wall

Entire body is composed of concrete.Longer dam eproncut-off

Entire body is composed of concrete.Outline

Earth damFloating concrete damConcrete gravity damType

Longer epron

Cut-off

Concrete gravity dam Floating concrete dam Earth dam

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LowHighLowIntake efficiency

In case that rock fill dam could be washed away by normal river flow.

Not governed by gradient, discharge or level of sediment load.

In case that earth dam could be washed away by normal river flow.

River condition

From earth to bedrockFrom earth to bedrockFrom earth to bedrockFoundation

Gravel is wrapped by metal net.

Gravel is filled with mortal etc.

Main material is gravel.Core wallOutline

Gabion damWet masonry damRock fill damType

Rock fill dam Wet masonry dam Gabion dam

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LowFairHighIntake efficiency

In case that rock fill dam could be washed away by normal river flow.

Gentle river flowIn case that metal net could be damaged by strong river flow.

River condition

From earth to bedrockFrom earth to bedrockFrom earth to bedrockFoundation

Wooden frame is filled with gravel.

Main material is local bush wood.

Surface of gabion dam is reinforced with concrete.Outline

Wooden frame with gravel dam

Bush wood damConcrete reinforced gabion damType

Concrete reinforced gabion dam Bush wood dam Wooden frame with gravel dam

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Location of weir sitePerpendicular to river direction

Topographical & geological conditions

Easy access

Structural StabilityFall resistance, Sliding resistance & Soil bearing capacity against resultant external force (weir own weight, water pressure, sedimentation weight, earth quake & up lift)

SedimentationEasy flushing

Existing landslide, debris, erosion, drift woods etc.

Influence on head acquisitionRelationship between construction cost & usable head

Backwater effectInfluence on upstream area during flooding

Concerns to be addressed in Weir DesigningConcerns to be addressed in Weir Designing1-

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Civil Structure: IntakeCivil Structure: Intake

Type of Intake

Side intakeTypical intake

Perpendicular to river direction

Tyrolean intakeAlong the weir

Simple structure

Affected by sedimentation during flooding

More maintenance required

Side Intake

Tyrolean Intake

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FunctionAll the suspended materials that could adversary affect turbine should be removed.

Specification to be decidedMinimum diameter of suspended materials (depend on turbine specification; 0.5–1.0mm)Marginal settling speed (about 0.1m/s)Flow velocity in settling basin (about 0.3m/s)Length & wide Conduit section

Widening sectionSettling section

Bb

1.02.0

Dam

SpillwayStoplog Flushing gate

Intake

Headrace

Bsp

hs

hsp+

15cm

h0

10～

15ｃ

ｍ

hi

ic=1/20～1/30

IntakeStoplog

biＬｃＬｗＬｓ

Ｌ

Sediment Pit Flushing gate

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FunctionConveys water from intake to forebay

Specification to be decidedStructure type (Open channel)Longitudinal slope (1/50 – 1/500)Cross section (flow capacity)Material to be used

Flow capacity calculation Qd=A×R2/3×SL

1/2 ／nwhere,Qd: Flow capacity (design discharge: m3/s )A: Cross-sectional areaR: R = A/PP: Length of wet sidesSL: Longitudinal slopen: Coefficient of roughness

Civil structure: HeadraceCivil structure: Headrace

PA

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Characteristic of HeadraceCharacteristic of Headrace

Risk of scouring & collapseNot applicable to high permeable groundDifficult to remove sedimentation

Easy constructionInexpensiveEasy repair

Simple earth channel

Not applicable to small diameterLong construction period

Relatively expensiveMore man power

Not applicable to high permeable ground

Disadvantage

Great flexibility of cross section design

Local materialScouring resistanceApplicable to permeable groundEasy construction

Easy constructionLocal materialScouring resistanceEasy repair

Advantage

Concrete channelWet masonry channel

Lined channel(Rock & stone)Type

Simple earth channel

Lined channel (Rock and stone)

Wet masonry channel

Concrete channel

n = 0.030 n = 0.025 n = 0.020 n = 0.015

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Characteristic of HeadraceCharacteristic of Headrace

Not applicable to big diameterEasy to decay

InexpensiveFlexible to minor ground deformation

Wood fenced channel

Heavy weightHigh transportation cost

Heavy weightHigh transportation costDisadvantage

Easy constructionShort construction periodHigh resistance to external pressureApplicable to small diameter

Easy constructionShort construction periodApplicable to small diameterFlexible to cross section figure

Advantage

Hume pipe channelBox culvert channelType

n = 0.015

Wooded-fenced channel Closed pipe (Hume pipe, steel pipe)Box culvert channel

n = 0.015n = 0.015

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FunctionRegulates discharge fluctuation difference between penstock & headrace due to load fluctuation.Final settling basin

Specification to be decidedWater storage capacityLayout & dimension of each facility

Attached StructureSpillwayScreenRegulating gateSluice gate

Civil Structure: Civil Structure: ForebayForebay

Headrace

Spillway

Screen

Headrace

Penstock

Penstock

Screen

Spillway

Headrace

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Civil Structure: PenstockCivil Structure: Penstock

FunctionConvey water under pressure from forebay to turbine

Specification to be decidedRoute (Slope, geological conditions etc)Material to be usedDiameter

- Construction cost- Electricity generation decrease due

to loss at penstock- Durability (Life time, O&M cost)

Thickness- Water pressure, own weight, water

weight, other external force (earth quake etc.)

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Powerhouse

Function:Provides shelter for the electro-mechanical equipment (turbine, generator, control panels, etc.)

The size of the powerhouse and the layout:Determined taking into account convenience during installation, operation and maintenance.

Foundation:Classified into two:

•For Impulse turbine -Pelton turbine, Turgo turbine or cross-flow turbine, etc.

•For Reaction turbine -Francis turbine or propeller turbine, etc.

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a. Foundation for Impulse Turbine

The figures shows the foundation for the cross flow turbine. There is a space between center level of the runner and the tailwater level

Flood W ater Level(M axim um )

20cm

boSection A -A

20cmb

bo: depends on Q d and H e

30～ 50cm

ｈｃ

30～ 50cm

H L3

(see Ref.5 -3)

hc={ }1/ 31 .1×Q d 2

9 .8×ｂ２

A

A

A fterbay T ailrace cannel O utle t

Foundation for Impulse TurbineFoundation for Impulse Turbine

Space

(atmosphere pressure)

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Section A-A

1.5×d3

Flood Water Level(Maximum)30～50cmｈｃ

2× ｄ3

d3

20cm

1.15× d3

1.5×d3

Hs

Hs：depens on characteristic of turbine

HL3

(see Ref.5-3)

hc={ }1/ 31.1×Qd2

9.8×ｂ２

A

A

b. Foundation for Reaction Turbine

The below figures show the foundation for the Francis turbine. The outlet level of the draft tube is under the level of tailwater

Foundation for Reaction TurbineFoundation for Reaction Turbine

Filled with waterIn the draft tube

This head is also effectively utilized

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Effective HeadEffective Head

HgHHe

HL3

HL1

HL2

Intake

Settling Basin

Headrace

ForebayPenstock

Powerhouse

Tailrace

Effective Head (Net head) := The total head actually acting on the turbine= Gross head – Head loss

He = Hg – (HL1 + HL2 + HL3)where, He: Effective head

Hg: Gross headHL1: Loss from intake to forebayHL2: Loss at penstockHL3: Loss at tailrace and draft tube

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Calculation of Head LossCalculation of Head LossThe head loss at the penstock (HL2) can be calculated by the following equations.

HL2 = hf + he + hv + howhere,

hf: Frictional loss at penstockhe: Inlet losshv: Valve lossho: Other losses (Bend losses, loss on changes in cross-

sectional area and others)

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<Reference > Head Loss at Penstock<Reference > Head Loss at Penstock(1) Frictional loss

Frictional loss (hf) is the biggest of the losses at penstock.

hf = f ×(Lp/Dp ) ×Vp2/2g

where, hf: Frictional loss at penstock (m)f : Coefficient on the diameter of penstock pipe (Dp).

f = 124.5×n2/Dp1/3

Lp: Length of penstock (m)Vp: Velocity at penstock (m/s)

Vp = Q/Apg: Acceleration due to gravity (9.8m/sec2)Dp: Diameter of penstock pipe (m)n : Coefficient of roughness

(steel pipe: n = 0.012, plastic pipe: n = 0.011)Q: Design discharge (m3/s)Ap: Cross sectional area of penstock pipe (m2)

Ap = 3.14×Dp2/4.0

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<Reference > Head Loss at Penstock<Reference > Head Loss at Penstock(2) Inlet Loss

hi = fe × Vp2/2g

where, hi: Inlet loss (m)fe: Coefficient on the form at the inlet

Usually fe = 0.5 in micro-hydro schemes.

(3) Valve Losshv = fv × Vp2 /2g

where, hv: Valve loss (m)fv: Coefficient on the type of valve,

fv = 0.1 (butterfly valve)

(4) OthersBend loss and loss due to changes in cross-sectional area are considered other losses. However, these losses can be neglected in micro-hydro schemes. Usually, the person planning the micro-hydro scheme must take account of following margins as other losses.

ho = 5 to 10%× (hf + he +hv)

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Equipment and Functions

1. Inlet valve:Controls the supply of water from the penstock to the turbine

2. Water turbine:Converts the water energy into rotating power

3. Generator:Generates the electricity by the driving force from the turbine

4. Driving facility:Transmits the rotation power of the turbine to the generator

5. Control facility of turbine and generator:Controls the speed, output of the unit.

6. Switchgear / transformer :Controls the electric power and increases the voltage of transmission

lines, if required7. Control panels:

Controls and protects the above facilities for safe operation.

Note: Items 5, 6 & 7 above may sometimes be combined in one panel.

Design of E/M EquipmentDesign of E/M Equipment

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1. Inlet Valve

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2. Water TurbineTypes:

Impulse turbines: Rotates the runner by the impulse of water jets by converting the pressure head into the velocity head through nozzles.

Reaction turbines: Rotates the runner by the pressure head.

Design for E/M EquipmentDesign for E/M Equipment

PropellerKaplan

FransisPump-as-Turbine

Reaction

CrossflowCrossflowTurgo

PeltonTurgo

ImpulseLowMediumHigh

HeadType

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Design of E/M EquipmentDesign of E/M EquipmentPeltonPelton TurbineTurbine

Acting water jet emitted from the nozzle to the bucket of runnerGood characteristics for discharge change

- Discharge: Small (0.2 – 3 m3/s)- Head: High head (75 – 400m)

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Design Design ofof E/M EquipmentE/M Equipment

PeltonPelton TurbineTurbine

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Arc shape runner blades are welded on the both side of iron plate discsEasy manufacturing and simple structure

- Discharge: Small (0.1 – 10 m3/s)- Head: Low, middle head (2 – 200 m)

WaterWater

Guide VaneGuide VaneCrossCross--Flow W/TFlow W/T

CrossCross--Flow TurbineFlow Turbine

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Design of E/M EquipmentDesign of E/M Equipment

CrossCross--Flow TurbineFlow Turbine

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Design Design of of E/M EquipmentE/M Equipment

Francis TurbineFrancis TurbineWide ranging utilization from various head and output Simple structure

- Discharge: Various (0.4 – 20 m3/s)- Head: Low to high (15 – 300 m)

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Francis TurbineFrancis Turbine

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Reverse Pump Turbine (Pump as Turbine)Reverse Pump Turbine (Pump as Turbine)1-

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GeneratorGenerator

Propeller RunnerPropeller RunnerGuide Vane Guide Vane (Wicket Gate)(Wicket Gate)

Timing BeltTiming BeltDraft Tube Draft Tube

Tubular TurbineTubular TurbineTubular type(Cylinder type) propeller turbine Package type is remarked recently

- Discharge: Various (1.5 – 40 m3/s)- Head: low head (3 – 20m)

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Tubular TurbineTubular Turbine1-

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Pico HydroPico Hydro


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Design Design ofof E/M EquipmentE/M EquipmentFlow chart of designing hydro turbineFlow chart of designing hydro turbine

Power plant H,Q

Number of units

Turbine type selection by the selection chart

Ns limit

N limit calculation from the Ns limit

N (min-1)

More than 500Tubular

200 – 900Propeller

100 – 350Diagonal flow

50 – 350Francis

8 – 25Pelton

Range of Ns(m-kW)Turbine type

Ns[m-kW] = N × 5/4

1/2

HP

Specific speed:

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1

10

100

1000

0.01 0.1 1 10 100Water Discharge

Effe

ctive

Hea

d

Selection of turbine type i.e.:i.e.: H = 25m, Q = 0.45mH = 25m, Q = 0.45m33/s/s

→→ Cross FlowCross Flow

oror Horizontal FrancisHorizontal Francis

Horizontal FrancisHorizontal Francis

Cross FlowCross Flow

Horizontal Horizontal PeltonPelton

Horizontal PropellerHorizontal Propeller

(m3/s, ft3/s)

(m, ft)

(3,529)(352.9)(35.29)(3.529)(0.3529)

(3.28)

(3,280)

(32.8)

(328)

(82ft) (15.88ft3/s)

Vertical FrancisVertical Francis


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3. GeneratorSynchronous:

Independent exciter rotor, applicable for both isolated and existing power networks

Asynchronous (induction):

No exciter rotor is usually applicable in networks with other power sources. In isolated networks, it must be connected to capacitors to generate electricity.

Generator output: Pg (kVA) = (9.8 x H x Q x η)/pf

WherePg: Capacity (kVA) H : Net head (m)Q: Rated discharge (m3/s)η: Combined efficiency of turbine & generator etc (%) pf: Power factor ( %)


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3. Generator

Speed and Number of Generator Poles - The rated rotational speed is specified according to the frequency

(50 or 60 Hz) of the power network and the number of poles by the following formula:

For synchronous generators:P (nos.) = 120 x f/N0 N0 (min-1) = 120 x f/P

where, P : Number of poles f : Frequency (Hz)

N0 : Rated rotational speed (min-1)

For induction generators: N (min-1) = (1-S) x N0

where, N : Actual speed of induction generator (min-

1) S : Slip (normally S= -0.02)N0 : Rated rotational speed (min-1)


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Standard rated speeds and number of poles for synchronous generators

300250243603002040033318450375165144291460050012720600109007508

12001000618001500460 Hz50 HzNo. of poles

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Comparative table of synchronous and induction generators

•No synchronizer• Inrush current(Parallel-in around synchronous speed is preferable.)

•No voltage regulation

•Leading power factor operation

•Only on-grid operation

•No excitation•High maintainability

•High rotational speed

Induction generators

•Synchronizer•Less electro-mechanical impact at parallel-in

•Voltage regulation

•Reactive power adjustment (Usually lagging power factor)

•Excitation circuit

•Relatively large air gap

Synchronous generators

Parallel-in operationOperationStructure

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4. Driving Facility (Speed Increaser)To match the speed of the turbine and generator

– Gearbox type:The turbine shaft and generator shaft are coupled with gears with parallel shafts in one box with anti-friction bearings according to the speed ratio between the turbine and generator. The life is long but the cost is relatively high. (Efficiency: 95 –97%, depending on the type)

– Belt type:The turbine shaft and generator shaft are coupled with pulleys or flywheels and belts according to the speed ratio between the turbine and generator. The cost is relatively low but the life is short. (Efficiency: 95 – 98%, depending on the type of belt)

In the case of a micro hydro-power plant, a V-belt or flat belt type coupling is usually adopted to save the cost because the gearboxtype transmitter is very expensive.

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5. Control Facility of Turbine and Generator

5.1 Speed Governor:The speed governor is adopted to keep the turbine speed constantbecause the speed fluctuates if there are changes in the load, water head or flow.

(1) Mechanical/Electrical type: Controls the turbine speed constantly by regulating the guide vanes / needle vanes according to load. There are two types of power source:

• Pressure-oil type• Motor type

Ancillary Equipment: Servomotor, pressure pump and tank, sump tank, piping or electric motor for gate operating mechanism


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(2) Dummy load type:Generator output is always constant at a micro hydro power station where a dummy load governor is applied to. In order to keep the frequency constant, the relationship “generator output = customers load + dummy load” is essential. The dummy load is controlled by an electronic load controller (ELC) to meet the above equation.

Transformer Customers of Electricity

Dummy Load Governor

SpillwayUpper Reservoir

G-T

Upper Dam

Power House


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The capacity of dummy load is calculated as follows:

Pd (kW) = Pg (kVA) x pf (decimal) x SF where,

Pd: Capacity of dummy load (Unity load: kW)Pg: Rated output of generator (kVA) pf: Rated power factor of generator SF: Safety factor according to cooling method (1.2 – 1.4 times

generator output in kW) to avoid over-heating the heater


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5.2 Generator ExciterIn the case of a synchronous generator, an exciter is necessary for supplying field current to the generator and keeps the terminal voltage constant even though the load fluctuates. The type of exciter is classified as follows:


• DC exciter:A DC generator directory coupled with main shaft supplies field current of the synchronous generator. The generator terminal voltage is regulated by adjusting the output voltage of DC exciter. Maintenance on brushes, commutator is necessary.

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Design Design ofof E/M EquipmentE/M Equipment• AC exciter:

The excitation circuit consists of an AC exciter directly coupled to the main generator, a rotary rectifier and a separately provided automatic voltage regulator with a thyristor (AVR). (High initial cost but low maintenance cost)

G

PT

CT

Ex. Tr

AVR

DC100V

PulseGenerator

Rotating section

ACEx

(Speed Detector)

Brushless exciter

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• Static excitation:Direct thyristorexcitation method. DC current for the field coil is supplied through a slip ring from a thyristorwith an excitation transformer. (Low initial cost but high maintenance cost)

G

PT

CT

Ex. Tr

AVR PulseGenerator

Slip ring

(Speed Detector)

Static excitation

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6. SwitchgearsSingle Line Diagram:The typical single diagram for a 380/220V distribution line

V

Hz

H

A x3

ELC (with Hz Relay)G

Turbine

Transmitterif required

Dummy Load

MagnetContactor

x3

NFB

Generator

V x3

Fuse

To Custmer

LampIndicator


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NFB

CB(MCCB)

Switchgear board including ELC

ELC


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7. Control Panels

7.1 Control Methods:

• Supervisory control method is classified into continuous supervisory, remote continuous control and occasional control.

• The operational control method is classified into manual control, one-man control and fully automatic control.

• The output control method is classified into dummy load governorcontrol for isolated grid, discharge control, water level control and programmable control.


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7.2 Instrumentation

• Pressure gauge for penstock• Voltmeter with change-over switch for output voltage • Voltmeter with change-over switch for output of dummy load

(ballast) • Ammeter with change-over switch for ampere of generator output • Frequency meter for rotational speed of generator• Hour meter for operating time• kWh (kW hour) meter and kVh (kVar hour) meter, which are

required to summarize and check total energy generation at the power plant


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7.3 Protection of Plant and 380/220V Distribution Line

Considering the same reason for cost saving in instrumentation, the following minimal protection is required for micro-hydro power plants in rural electrification.1. Over-speed of turbine and generator (detected by frequency)2. Under-voltage 3. Over-voltage4. Over-current by NFB (No Fuse Breaker) or MCCB (Molded Case Circuit

Breaker) for low-tension circuits.

When an item 1, 2 or 3 is detected, the protective relay is activated and forces the main circuit breaker trip. At that time, the unit shall be stopped to check conditions.


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Design Design ofof E/M EquipmentE/M EquipmentExerciseThere is a potential site with the following conditions:

Net head: 10 mDischarge: 1 m3/sFrequency: 50 HzSynchronous generator is required.

Q1: Which types of turbine are preferable for the site?

Q2: How wide of the applicable range of specific speed ona selected turbine?

Q3: How wide of the rotational speed range will be applicable for the selected turbine when the turbine efficiency is 0.6?

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Design Design ofof E/M EquipmentE/M EquipmentAnswerThere is a potential site with the following conditions:

Net head: 10 (m)Discharge: 1 (m3/s)Frequency: 50 (Hz)Synchronous generator is required.

Q1: Which types of turbine are preferable for the site?A1: Cross Flow, Horizontal Propeller, and Horizontal

Francis (Please refer to the selection chart.)

Q2: How wide of the applicable range of specific speed ona selected turbine?

A2: If the horizontal propeller is selected, the range of Ns is 200 – 900 (m-kW).

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1

10

100

1000

0.01 0.1 1 10 100Water Discharge

Effe

ctive

Hea

d

Selection of turbine type

Horizontal FrancisHorizontal Francis

Cross FlowCross Flow

Horizontal Horizontal PeltonPelton

Horizontal PropellerHorizontal Propeller

(m3/s, ft3/s)

(m, ft)

(3,529)(352.9)(35.29)(3.529)(0.3529)

(3.28)

(3,280)

(32.8)

(328)

Vertical FrancisVertical Francis


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Design Design ofof E/M EquipmentE/M EquipmentAnswerQ3: How wide of the rotational speed range will be applicable for

the selected turbine when the turbine efficiency is 0.6? A3: The turbine output P is

P = 9.8 ηt Q H = 9.8 × 0.6 × 1 × 10 = 58.8 (kW)so that the minimum and maximum rotational speeds are calculated as follows:

Nmin = Nsmin × H5/4 / P1/2

= 200 × 105/4 / 58.81/2

= 463 (min-1)Nmax = 900 × 105/4 / 58.81/2

= 2087 (min-1)Considering the standard rated speed, the speed range from 500 to 1500 (min-1) is applicable for the direct coupled generator.In case that 500 (min-1) is selected as the turbine rated speed considering turbine characteristics, a speed increaser is preferable to apply because lower speed generators are costly.

Micro Hydro Designing

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