small hydro technology 6

8/16/2019 Small Hydro Technology 6

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Small Hydro

PowerSystems

Power Generation

http://en.wikipedia.org/wiki/Image:Orontes.jpg


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Power (kW) = f (Head, Discharge, Efficiency)

P = f (H, Q, η)

Q

H

Power


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Hydrology

Flow prediction by area-rainfallmethod

Flow prediction by correlation method

Head measurement

Flow measurement


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Area-rainfall method

Catchment area with contour maps

Select the highest head (less turbine cost)

Find annual average daily flow using rain-

gauge data Calculate net flow available after

evaporation, use of water, seepage, etc.from data

Account for flow variation during months Calculate the lowest flow

Construct FDC


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Flow Duration Curve (FDC)

DefinitionA graphical representation of aranking of all the flows in a given

period, from the lowest to thehighest, where the rank is thepercentage of time the flow valueis equalled or exceeded.


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Correlation method

Conduct sample field measurements

10 / year or 6 / lean period

Correlate FDC with data from Govt.agencies

Correct FDC with site data


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Head Measurement

Water filled tube (with scales or person)

Water filled tube and pressure gauge

Spirit level and plank (or string)

Altimeter (9 mm Hg/100 m)

Sighting meter

Sighting with spirit level

Dumpy level / theodolite

Electronic Digital Levels

GPS (Global Positioning System)


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Head Measurement using

Abney-level Method


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Head measurement using

spirit level and plank


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Topographic Maps

Used to locateheads

Used to locatevarious

components ofSHP plant

>100m, use1:50,000 maps

Smaller mapswith 10mcontours areuseful


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Flow Measurement

Salt gulp method (turbulent flows)

Bucket method

Float method

Propeller devices

Weir method

Stage control method(for little large dams)


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Salt gulp method

100 g salt for 0.1 m3/s flow over 50m distance (estimate salt required)

record conductivity each 5 sec. andplot

Q = mass of salt / (factor * area

under curve)


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Bucket method

Divert entire flow to bucket

record time

suitable for small streams only


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Float method

Approximate method only

use different floats and average thetime

reduce surface velocity by:large, slow, clear stream : 0.75

small regular channel, smooth stream : 0.65

shallow (0.5m) turbulent stream : 0.45very shallow, rocky stream : 0.25

Q = A * V


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Weir Method

Natural sections

Rectangular weirQ = 1.8 (L-0.2 h) h**1.5

Triangular weirQ = 1.4 h**2.5

L in m, h in cm, Q in m

3

/s


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Fl M t i I t t d


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Flow Measurement using Integrated,

handheld meter


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Reconnaissance Study Data Collection (Basic Reference Materials)

Topographic maps (Minimum Requirement) Detailed maps with a scale of at least 1/50,000 Landform, location of villages, slope of river, catchment area

of proposed site, access road

Rainfall data

Monthly and annual rainfall data of adjacent areas Isohyetal maps

Hydrological data (Minimum Requirement) River discharge data from the adjacent areas

Socio-economic information

Others Climate map

Distribution line map

Existing proposal from local government and residents


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Map Study

Catchment Area

(Drainage Area)

1. Trace Maintain ridge

2. Measure the areawith a planimeter

3. Determine River

Gradient & Profile


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Assessment of Power Potential

Power potential is the product of availablehead and quantity of water at any point oftime and is determined by using the followingformula:

P = 9.81 ηQH

Where, P = Power output in kW

Q = Discharge in m3 /sH = Head (Net head) in m

η = Overall efficiency (0.5 to 0.7)


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Examples

Calculate flow needed to run a 50 kWfactory with a water fall of 20 m height

Pnet = 9.81 η Q H

Q = 50 / (10*0.5*20)

= 0.509 m3 /s

Calculate Power when the flow is 150 lt/s

and head is 90 ft.Pnet = 9.81 * 0.5 * 0.15 * 30

= 22.07 kW


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Assessment of Power Potential – contd.

Small run-of-the-river schemes generallyhave meager discharge data and data forstudies has to be generated by hydrological

approaches. The power potential for a small hydro

scheme is determined corresponding to 75%and 50% water availability.

The power potential may be computed on thebasis of monthly or 10 days average flow.


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Cut-away

drawing of awater

turbine

generator


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Turbines

Head Pressure(40m) (3-40m) (


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Impulse turbine

Water jet from nozzle impact -deflection of water - momentumtransfer - rotates runner

operates in air; no pressure dropacross runner

casing only to control splashing

cheaper

smallest runner preferred


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Pelton wheel

and nozzles

http://localhost/var/www/apps/conversion/tmp/scratch_4/Pelton%20wheel%20_%20Pelton%20turbine%20_%20Hydro-power%20(3D%20animation).flvhttp://localhost/var/www/apps/conversion/tmp/scratch_4/Pelton%20wheel%20_%20Pelton%20turbine%20_%20Hydro-power%20(3D%20animation).flv


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Reaction turbine

Rotating element is fully immersed

enclosed in a pressure casing

clearance between runner & casing

minimised

runner blades are profiled to havepressure drop - lift forces - causes

runner to rotate

http://localhost/var/www/apps/conversion/tmp/scratch_4/Kaplan%20turbine%20_%20Run-of-the-river%20hydroelectricity%20-%20How%20it%20works!%20(Animation).flv


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Kaplan Turbine

http://localhost/var/www/apps/conversion/tmp/scratch_4/Kaplan%20turbine%20_%20Run-of-the-river%20hydroelectricity%20-%20How%20it%20works!%20(Animation).flvhttp://localhost/var/www/apps/conversion/tmp/scratch_4/Kaplan%20turbine%20_%20Run-of-the-river%20hydroelectricity%20-%20How%20it%20works!%20(Animation).flv


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Francis Turbine

http://localhost/var/www/apps/conversion/tmp/scratch_4/Francis-Turbine%20(3D-Animation).flvhttp://localhost/var/www/apps/conversion/tmp/scratch_4/Francis-Turbine%20(3D-Animation).flv


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Bulb Turbine


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Pump as Turbine (PAT)

Cheaper (due to large scaleproduction of pumps)

Disadvantages:

poorly understood characteristics

lower efficiencies

unknown wear characteristics

poor part flow efficiency


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Selectionof Turbine


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Typical Turbine Efficiencies

small hydro technology 6

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