Cook Legacy CollegeTraining Module M-200:

Fundamentals of Small Hydro

Goals of This 15-Minute Module

Know what small hydro is.

Understand major features, components, and selection criteria

Understand technical and financial considerations when assessing a site

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Fundamentals of Small Hydro

SH 103:Review and

Quiz

SH 102: Fundamentals

SH 101: Overview and Background

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What is Small HydroSmall Hydro (also called small hydroelectric or small hydro) refers to the generation of electrical power by using diverted water to rotate a turbine.The major components include:• An intake• A penstock• A turbine & generator• A switchyard for connection to the power pole

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What is Small HydroThe most commonly used form in intake structure design is the “Discharge Equation.”Different forms are used for flow over the spillway, Coanda accelerator, measurement weirs, and various secondary spills.Generally the value of C, the discharge coefficient, will adjust based on some empirical test.The basic discharge equation is Q=Clh^3/2

Where:Q=FlowC=Discharge coefficientl=Length of the weirh=head above the crest

The most important thing when selecting and implementing a discharge equation is ensuring it matches in all respects the condition it was intended for.

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Calculating Power PotentialPower is given as:P=HQkGWhere:P=Power in wattsH=Head (the difference in elevation between the intake and the powerhouseQ=Flow in m^3/sG=Gravity (9.8 m/s^2)k=Turbine efficiencyA quick estimate is to take 7 * Q* H

Head (m)Head (m)

Flow (m3/s)

Power in kW » 7 x Head x Flow

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What is Small Hydro

What counts as small hydro?

Typical Power

Micro < 100 kW

Mini 100 to 1,000 kW

Small 1 to 50 MW

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What is Small Hydro Type of grid

– Central-grid: Generated power is sold back to a power grid such as a utility.

– Isolated-grid or off-grid: Generated power is used locally near the point of generation.

Type of civil works– Run-of-river

• No water storage

• Power varies with flow available from river: lower firm capacity

– Reservoir

• Higher firm capacity year-round

• Significant damming usually required

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Process for Sizing Site

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Process for Sizing Site

Flow-Duration Curve

0.0

10.0

20.0

30.0

40.0

50.0

0 10 20 30 40 50 60 70 80 90 100Percent Time Flow Equalled or Exceeded (%)

Flo

w (

m³/

s)

• Estimate flow duration curve based on Measurements of flow over time

Size of drainage above site, specific run-off, and shape of flow duration curve

The easiest way to mess up a high head site is to overestimate the flow (as this is the only variable)

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Process for Sizing SiteFlow-Duration Curve

0.0

10.0

20.0

30.0

40.0

50.0

0 10 20 30 40 50 60 70 80 90 100Percent Time Flow Equalled or Exceeded (%)

Flo

w (

m³/

s)

Picking the Turbine• Estimate the installed capacity

at various points on the FDC

• Estimate the cost of equipment cost associated with those. This includes questions such as the size of the equipment and how many nozzles will be used.

• Integrate the area under the curve with various scenarios and pick the best payback. Sometimes this can be approximated by simply slicing the FDC into a few scenarios.

For example:The green line has high capacity to “catch” high flow events, but may not run enough to be worth the cost.The blue line will be cheaper, but may leave power on the table. The red line may be the best return.

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Small Hydro Major Components

The most expensive cost component for a small hydro plant is the Civil Cost. Much of our approach is in lowering the civil cap-ex.

Civil Cost55%

Mechanical & Controls25%

Electrical10%

Other10%

Small Hydro Cost Estimate

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Small Hydro Major ComponentsThe major components for the site are:• Intake structure• Penstock• Powerhouse – the primary components of the powerhouse are:

o Turbine-generatoro Switchyard

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Intake StructureThe intake structure needs to deliver clean water to the penstock

Traditional intakes include a coarse screen with secondary screening and settling basins to remove sand.Coanda screens eliminate secondary screening need & use overflowing water to stay clean.

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Turbine Types

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Pelton Turbine Details

As Coanda Screens are most suitable for medium and high head sites they are commonly paired with Pelton MachinesPeltons have a series of nozzles controlled by actuated needle valves, that spray water onto the runners.

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Turbine Types

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Turbine Types

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Low Head Hydro: Natel HydoEngine

In the low head space, we offer complementary process equipment to a range of turbine designs.

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Low Head Hydro: Cleanpower Turbinator

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Other Powerhouse Components

The generator is connected to the turbine.A generator can be either synchronous (i.e. designed to work with an existing load) or asynchronous.For very small sites an induction motor can be used in place of the generator.

Additional components are the plant controls and basic facility requirements like lighting, fire protection, personnel protection, and monitoring equipment.

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Design Considerations

Technical Financial

Environmental Regulatory

Plant

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Design Considerations

Intake Design

• Side intake• Coanda

Turbine Selection• Head• Flow• Fish

Penstock Design• Distance• Pressure

T&D Design• Distance• Connection Type

Technical

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Design Considerations

Cap-Ex• Civil• Mechanical• Consultancy

Funding Sources• NGO• Private Funding• Equipment

Cost of Capital Payback of Components• Cheap & swap• Long term value

Financial

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Design Considerations

Water Grid Connection

Permitting AgencyConstruction Permits

Regulatory

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Design Considerations

Social• Build projects good for

people• Don’t screw landowners.

Be fair.

Fisheries• Improve diversion• Improve survival

Land Use• Intake• T&D

Proper O&M

Environmental

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Review Questions What are the components of calculating

power capacity?

What are the balance of plant benefits of a Coanda intake