L-11 HydropowerConcepts & Simulation

7/23/2019 L-11 HydropowerConcepts & Simulation

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Hydrologic Engineering Center

HydropowerConcepts

How Does Hydropower Affect

Reservoir Simulation?



Topic Objective:

To know the basic hydropower concepts andhow they affect reservoir system analysis.

Power Definitions

Power Demand

Types of Hydropower projects

Computing power release

Reservoir hydropower simulation



Definitions

Work = Force × Distance (ft-lbs. or N-m)

Power = Rate of doing work

Referred to as Capacity (to do work)

Electric Capacity given in Kilowatts orMegawatts (KW or MW)

1 Kilowatt = 1,000 N-m/sec = 737.56 ft-lbs./sec

Energy = Work = Power * Time

Electric Energy given in Kilowatt-hours orMegawatt-hours (KWH or MWH)

Work accomplished, but not how fast!



Nature of Power Demand

Demand for Power must be exactly met

Supply == Demand at all times

Surplus supply must have a use. You can’t storepower on the grid.

Shortages have severe consequences!

Supply based on Maximum (Peak) Demand

Demand varies:

During day

Days of week

Seasonally



Load Curve

Load: demand for

power

Load Curve: Graph of

load changing with

time

Typical Weekly Load:

Sunday low

Nights low

Mid-day peak or

Morning/Evening peak

– varies seasonally



Demand vs. % of time(Same weekly demand)

Shows usage of powerresources

Shows % time required

Base = 100%

Peak < 5%

Value depends on

alternative resources

Load –Duration



Base Load - the minimum load in a period oftime.

Base Load Plant – a power plant that runs at

a constant capacity to carry base load Peak Load - the maximum load in a period of

time.

Peaking Plant - operates to provide powerduring maximum load periods

Load Characterization



Plant Factor

Plant Factor - the fraction of the day during whichthe plant ran at capacity

Plant Factor = 6 hrs of generation at 100% capacity

= 6/24 x 100/100 = .25 or 25%

Plant Factor - the fraction of capacity the plant ranat to meet load ( Avg. Load / Capacity ) Plant Capacity = 60,000 kW

Avg. Load = 8,750 kW

Plant Factor = 8,750 / 60,000 = 15%

If the Plant ran at Capacity to meet this load, it wouldoperate 15% of the time



Load carrying ability of a hydropower plantduring the “Critical Period”

Critical Period (for hydropower) - when thelimitations of hydroelectric power supplydue to water conditions are most criticalwith respect to system load requirements

Drought period (or low water availability)

coincident with..

High demand

Dependable Capacity



Dependable (Firm) Energy

Energy associated with Dependable Capacity

Electric energy which is intended to have

assured availability to the customer to meet

all or any agreed upon portion of his load

requirements

Assured availability usually means that no

shortages will be tolerated



Separate benefits for energy & capacity Energy … power generated

Capacity … ability to generate

Primary Power benefits for dependablecapacity and firm energy Energy based on kW-Hrs on demand

Capacity based on availability at critical period

Secondary Power benefits for energyproduced during high flow periods Secondary value usually much lower

Value of Energy and Capacity



Storage Reservoirs

All or part of the reservoir pool is allocatedto power

For generation – a power pool

To maintain head – buffer or operating inactive

Releases made to meet Energy demand

Power storage used when flow is low

Headwater varies with pool

Tailwater dependent on flow

Primary and Secondary energy are outputs



Run-of-River Reservoirs

Headwater essentially constant

Tailwater dependent on flow

Energy is a function of flow (in & out)

Energy is Secondary with lower value

Often downstream from storage reservoir



Storage – Peaking Reservoirs

Peaking Power operates for short interval

High releases during generation

Minimum Releases during non-power

periods Releases impact downstream system



Power demand function of pool level

Firm energy from minimum power pool topower rule curve

Higher energy produced when above powerrule curve

Provides more energy when water supply ishigh

Storage – Power Guide Curve



Firm Energy Computations

Computed for the Critical Period.

Energy produced during the period ofmaximum drawdown is determined

Annual Firm Energy is based on the sum ofminimum energy produced in each timeperiod of the calendar year.

Dependable Capacity is the capacity associated

with Firm Energy.



Power Equation

Power = weight of a discharge “falling” adistance

Power (kW) = [Q * w * h * e] / 737.56

Q = discharge in cfs

w = weight of water in lbs./ft3

h = net head in feet (Total h - Hydraulic losses)

e = efficiency of generator & turbine units

737.56 ft-lbs./sec = 1 Kilowatt



Q = 737.56 (kW) / (w * h * e)

if, e = constant 0.86

w = 62.4 lbs./ft3

Q = 13.74 ( kW / h )

h = Headwater - Tailwater - Losses

Headwater, Tailwater, & Loss depend on Q

Iterative solution is required

Calculation of Power Release



Power Release Determination:Instantaneous

Assume net Head Initial estimate based on end of previous period or

iteration

Compute Q, based on capacity (kW)

Determine Tailwater for Q

Calculate net Head, based on headwater,tailwater and losses

Compute new discharge using net Head Repeat until net Head remains the same



Compute Average Q for period

Compute ending Storage Outflow = Qpower + Losses + Evaporation

Determine ending Elevation Calculate avg. Headwater for period

Repeat until average Q remains the same

Power Release Determination:Period Average



Leakage & Seepage

Evaporation - dependent on release

Fish Ladders

Navigation Locks

Water Supply withdrawals

Station use: cooling, power,

Minimum releases during non-generationperiods

Water Lost to Hydropower



Hydropower Limits

Penstock Flow Capacity – can’t release morethan penstock can carry

Turbine Capacity – can’t release more than theturbine can discharge

Generator Overload Capacity – can’t generatemore than maximum capacity

Variable efficiency – maximum efficiency exists

in a narrow range of head and discharge



References

Estimate of National Hydroelectric Power Potentialat Existing Dams, USACE, July 1977

Hydroelectric Power Evaluation, Federal PowerCommission, FPC P-35, March 1968

Hydropower, EM 1110-2-1701, 31 Dec 1985

Potential for Increasing the Output of ExistingHydroelectric Plants, USACE, HEC July 1981



Hydrologic Engineering Center

Hydropower Simulation

HEC-ResSim



Objectives

To know how to:

Add a Power Plant to a reservoir and define Power

Plant Data

Add Hydropower Rules to the system

Control Release Allocation to outlets

Review the hydropower output options



Hydropower Data

Physical Data

Add Power Plant

Define Power Plant Data Outlet Capacity

Power Capacity

Efficiency

Losses

Station Use

Hyd. losses

Add Tailwater Elevation



Add a Power Plant

Add Power Planta) Use component-specific menu

b) Use right-click shortcut menu

P Pl D O l



Power Plant Data-OutletCapacity

Physical Powerhouse

Capacity

Elevation vs Flow

Limits Flow for power

generation

Considerations:

“Best Gate”

“Full Gate”

P Pl t D t P



Power Plant Data-PowerCapacity

Select Capacity tab in Power Plant dialog

Enter the Installed Capacity (MW).

Select the Variable Capacity option

Installed Capacity with Overload factor

Enter the Overload Factor Function of Reservoir Elevation

Function of Reservoir Storage

Function of Release

Function of Operating Head

P Pl t D t Pl t



Power Plant Data-PlantEfficiency

Select Efficiency tab in Power Plant dialog

Select the Efficiency Method option Constant

Function of Reservoir Elevation

Function of Release Function of Operating Head



Power Plant Data-Station Use

Select Station Use tab in Power Plant dialog

Select the Station Use Method option Constant

Function of Release

Station use is not available for power generation

P Pl t D t H d li



Power Plant Data-HydraulicLosses

Select Hyd. Losses tab in Power Plant dialog

Select the Hydraulic Losses Method option Constant (feet/meter)

Function of Release (Release vs. loss)

Hydraulic Loss is subtracted from Gross Head in power

computations.



Add Tailwater Elevation

Add Tailwatera) Use component-specific menu

b) Use right-click shortcut menu

Tailwater

Tailwater appears in tree below theselected component



Define Tailwater Elevation

Select Tailwater

Enter data

Constant Elevation

Downstream Control

Rating Curve

If multiple data,

higher controls



Hydropower - Power Guide Curve

Hydropower - Schedule

Hydropower - System Schedule

Hydropower - Time-series Requirement

Hydropower Operation Rules

Hydropower Power Guide



Create the rule

Select the top and bottom zones

of the power pool

Hydropower-Power GuideCurve



Complete thetable to define

the rule

% Storage vs.

% Plant Factor

Power Generation

Pattern

Power Guide Curve



Power Generation Pattern

Pattern applies all year

Weekly Pattern

Seasonal Variation

Specify weekly Pattern for:

All Week

Weekdays & Weekends

Each Day



Power Generation Pattern

Seasonal Variation



Create the rule Requirement varies

Monthly

Seasonally

Specified as:

Plant Factor

Daily MWH

Weekly MWH

Monthly MWH

Starting day of week Week belongs…day

Period to satisfy the

requirement

Hydropower-Schedule



Hydropower Schedule



Hydropower-System Schedule

d i i



Hydropower-Time Series

R l All i Wh ?



Release Allocation-What?

What is Release Allocation? Which outlets should release first, next, and so on

Balanced approach

Evenly weighted (e.g., 50:50 split (default))

Unevenly weighted (e.g. 60:40 split)

Sequential approach

Hydropower reservoirs often direct any release to thepower plant first

Other outlets release water when the power plant

reaches capacity Release Allocation is an “operations” option

Define the priority (or order) to the available outlets

R l All ti H ?



Release Allocation – How?

Operations Tab in Reservoir Editor Use Specified Release Allocation

Specify Allocation Type

Balanced

Specify the component weighting

Sequential

Specify the component order

P O t t O ti



Reports

Power Summary

Plots Options

Plot

Plot Power

User Plots

Power Output Options

P S R t



Power Summary Report

P Pl



Power Plot

U D i d Pl t E l



User Designed Plot Example

Bring up thedefault plot

Open the “SelectPlot Variables”

menu





Save Custom Plots for reuse



Save Custom Plots for reuse

Summary



Summary

In the Reservoir Editor, Physical Tab… Add Power Plant

Define Power Plant Parameters

Add Tailwater

In the Reservoir Editor, Operations Tab… Add Hydropower Rule to an Operating Zone Specify Hydropower Requirements

Specify Release Allocation Type

Analyze results with plots and reports

Questions?



Questions?

L-11 HydropowerConcepts & Simulation

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