*Small Hydro Power Systems

*Conventional Vs SHP

*Potential Energy(Mass of water located at a higher elevation)Kinetic Energy(Water flows as a result of the mass being at a higher elevation)Mechanical Energy(Flowing mass of water turns a turbine runner)Electric Power(Turbine runner turns a directly coupled generator)The Concept of Hydropower

*Small Hydro Power Scheme

*Classification of Small Hydro Power

World wide

USA < 5 MWUK < 5 MWIndia < 25 MWSweden < 15 MWColombia < 20 MWAustralia < 20 MWChina < 25 MWPhilippines < 50 MWNew Zealand < 50 MWCanada < 20 MWErstwhile USSR < 30 MW

Indian Classification

Pico hydro < 10 kWMicro hydro 10 - 100 kW Mini hydro 0.1 - 3 MWSmall hydro 3 - 25 MW

*Potential of small hydro

World potential : ~2,00,000 MW Installed capacity : 60,000 MW

Indian potential : ~15000 MWInstalled capacity : ~1750 MWUnder implementation : ~500 MW

*Types of SHP

Run of the river schemesStorage typeSchemes on the canal dropsDam toe power house

*

*Run-of-the-river schemesNormally utilise the head and discharge of hilly streams, which uses water within the range of the natural river flow and generally has no reservoir or pondage to regulate the river flowComponents may includeDiversion weirIntake structureDe-silting chamberWater conductor systemFore bay with surplus escapePenstockPower houseTailrace channelSwitchyard & transmission arrangement

*

*

*Features of Run-of-the-riverdoes not stop river flowuse only a diversion weirwater is not carried over seasonslow costlocally builtSimple in construction and operationlong term reliabilityno flooding of in the up-streams of riverno environmental damage

*Schemes on the canal fallsThese are located on existing or proposed irrigation channels utilising the canal discharges and head created by falls, to generate powerTwo or three falls could be combined and aggregate heads utilised in a single power house

*

*Dam-toe power houseThis utilises the head of an existing irrigation dam/barrage located in the DamThese schemes have a relatively big reservoir that stores water in the rainy season and release it in the dry season

*

*Advantages of small hydro

Limited investmentShort gestation periodEnvironment friendlySimple civil workMinimum operation and maintenance costOperational flexibilityDecentralised power option

*Features of Storage dam type(Conventional Hydro)More complex & expensivewater can be carried over seasonsnot so environment friendlycapacity to reduce due to siltingflooding of river up-stream happenslong gestation period

*Weir and IntakeDiversion WeirObstruction in the river to raise the water level to divert water to the headraceMay not require a high dam or a big reservoir

IntakeStructure to take water from the river

*Settling Basin/ Desilting TankA pond to collect and flush out sediments and other suspended materials

To prevent suspended materials from entering the waterway and eventually the turbine

It is sometimes omitted in cases where inflow of sand and soil is minimal

*Headrace ChannelConveys water from the intake to the forebay

Usually an open canal made of concrete, but sometimes it is made of soil and/or pipes

*ForebayA pond-like structure at the top of the penstock to regulate fluctuations in the water

A spillway/surplus escape may be connected to the forebay

It also functions as a final settling basin for suspended materials in the water

*PenstockA pipe to convey water under pressure from the forebay to the turbineA steel pipe in the case of high pressure

Hard vinyl chloride pipes and FRP in the case of low pressure

*PowerhouseA shelter for the electro-mechanical equipment (turbine, generator, controllers and panels)

*

*Turbine & GeneratorTurbineConverts the water flow energy to rotational powerTurbineConverts the water flow energy to rotational powerGeneratorGenerates electricity from the rotational power of the turbine

*Tail RaceAfter leaving the turbine, the water discharges down a tailrace channel back into the river

*Switch Yard Grid Connected

Stand-alone system

*Designing a Scheme1. Capability and Demand survey2. Hydrology study and Site survey3. Pre-feasibility study4. Detailed survey

*1. Capability and Demand surveyHow much energy is needed ?What purposes ?When it is needed ?Where it is needed ?How much the user is willing to pay for electricity ?

*2. Hydrology study and Site surveyEstablishes potentialHow water flow variesWhere water should be taken for better economy & effectivenessShows how much power & when availableTakes into account various uses of water

*3. Pre-feasibility studyStudy of various energy options with cost(e.g) extension of griddiesel generationdifferent SHP designsHow well the demand & supply of power matches (Are the users happy with no power in a few low flow months?)

*Pre-feasibility study (cont.)Recommendations formanagement structuretariff structurecontingency planstime scale to correct hydrological study results

Should outline more than one engineering design option (transmit electricity to load or shift load to site)

*4. Detailed SurveyDetailed engineering calculations of the selected schemeFinancial study supply & InstallationO & M study - Transmission & commissioningTechnical design should suit local conditions (finance, skills, accessibility, repair facility,.)Time required for project completionTariff structureScope for contingency finance

*Power (kW) = f (Head, Discharge, Efficiency) P = f (H, Q, )QHPower

*Flow Duration Curve (FDC)

*HydrologyFlow prediction by area-rainfall methodFlow prediction by correlation methodHead measurement Flow measurement

*Area-rainfall methodCatchment area with contour mapsSelect the highest head (less turbine cost)Find annual average daily flow using rain-gauge dataCalculate net flow after evaporation, use of water, seepage, etc. from dataAccount for flow variation during monthsCalculate the lowest flowConstruct FDC

*Correlation methodConduct sample field measurements10 / year or 6 / lean periodCorrelate FDC with data from Govt. agenciesCorrect FDC with site data

*Head MeasurementWater filled tube (with scales or person)Water filled tube and pressure gaugeSpirit level and plank (or string)Altimeter (9 mm Hg/100 m)Sighting meterSighting with spirit levelDumpy level / theodoliteElectronic Digital LevelsGPS (Global Positioning System)

*

*Head Measurement using Abney-level Method

*Head measurement using spirit level and plank

*Topographic MapsUsed to locate headsUsed to locate various components of SHP plant>100m, use 1:50,000 mapsSmaller maps with 10m contours are useful

*Flow MeasurementSalt gulp method (turbulent flows)Bucket methodFloat methodPropeller devicesWeir methodStage control method (for little large dams)

*Salt gulp method100 g salt for 0.1 m3/s flow over 50 m distance (estimate salt required)record conductivity each 5 sec. and plotQ = mass of salt / (factor * area under curve)

*

*Bucket methodDivert entire flow to bucketrecord timesuitable for small streams only

*Float methodApproximate onlyuse different floats and averagereduce surface velocity by:large, slow, clear stream: 0.75small regular channel, smooth stream : 0.65shallow (0.5m) turbulent stream : 0.45very shallow, rocky stream: 0.25

Q = A * V

*

*Weir MethodNatural sections

Rectangular weir Q = 1.8 (L-0.2 h) h**1.5

Triangular weir Q = 1.4 h**2.5

L in m, h in cm, Q in m3/s

*

*Flow Measurement using Integrated, handheld meter

*Reconnaissance StudyData Collection (Basic Reference Materials)Topographic maps (Minimum Requirement)Detailed maps with a scale of at least 1/50,000Landform, location of villages, slope of river, catchment area of proposed site, access roadRainfall dataMonthly and annual rainfall data of adjacent areasIsohyetal mapsHydrological data (Minimum Requirement)River discharge data from the adjacent areasSocio-economic informationOthersClimate mapDistribution line mapExisting proposal from local government and residents

*Map StudyCatchment Area (Drainage Area)

Trace Maintain ridgeMeasure the area with a planimeterDetermine River Gradient & Profile

*Assessment of Power Potential

Power potential is the product of available head and quantity of water at any point of time and is determined by using the following formula:

P = 9.81 QH

Where, P = Power output in kW Q = Discharge in m3/s H = Head (Net head) in m = Overall efficiency (0.5 to 0.7)

*ExamplesCalculate flow needed to run a 50 kW factory with a water fall of 20 m heightPnet= 9.81 Q HQ= 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

*Assessment of Power Potential contd.Small run-of-the-river schemes generally have meager discharge data and data for studies 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 the basis of monthly or 10 days average flow.

*Cut-away drawing of a water turbine generator

*TurbinesHead Pressure(40m)(3-40m)(

*Impulse turbineWater jet from nozzle impact - deflection of water - momentum transfer - rotates runneroperates in air; no pressure drop across runnercasing only to control splashingcheapersmallest runner preferred

*Pelton wheel and nozzles

*Reaction turbineRotating element is fully immersedenclosed in a pressure casingclearance between runner & casing minimisedrunner blades are profiled to have pressure drop - lift forces - causes runner to rotate

*Kaplan Turbine

*Francis Turbine

*Bulb Turbine

*Pump as Turbine (PAT)Cheaper (due to large scale production of pumps)

Disadvantages:poorly understood characteristicslower efficienciesunknown wear characteristicspoor part flow efficiency

*Selection of Turbine

*Typical Turbine Efficiencies