Scheduling the TVA Hydro System Using RiverWares Optimization

1
Scheduling the TVA Hydro System Using RiverWares
Optimization

• Suzanne H. Biddle, P.E.
• Tennessee Valley Authority

2
TVA region covers 40,000 sq miles
KY
VA
NASHVILLE
NC
KNOXVILLE
TN
CHATTANOOGA
HL
SC
MS
GA
AL
Watershed Power Service Area
3
Average annual rainfall above Chattanooga is
about 51 inches and runoff is about 22 inches
4
TVA operates the reservoir system to meet
multipurpose objectives

• Navigation
• Flood damage reduction
• Power generation
• Recreation
• Water quality
• Water supply

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River Scheduling issues two hydro forecasts each
day
Inputs Future value of water Hourly hydropower
value Inflow forecast Initial conditions Objective
s
9 day optimization using marginal costs for water
allocation
9 day optimization using block costs for daily
generation schedule
3 day optimization using block costs for hourly
generation schedule
daily hydro forecast (14 days)
hourly generation preschedule (current day 2
forecast days)
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Optimization covers short term, but also
considers long term tradeoff
Future Value of Water 14 - 120 Days
RiverWare 6-Hourly Forecast 14 Days
Observed Values 3 - 14 Days
Current Day
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Many reservoirs follow seasonal guide curves
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These objectives are used in optimizing the hydro
system

• Day 1 outflows are fixed
• Ending targets are fixed for non-storage
  tributaries and main river
• Minimum flow requirements
• Top and bottom of daily operating zone
  non-storage tribs and main river only
• Minimum operations guides
• Flood guides
• Minimize spill
• Special operations
• Economic objective function

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What does economic objective function mean?

• All operating constraints must first be satisfied
• Then, with any remaining flexibility
• Maximize avoided operating cost delta (value of
  water in storage)

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Is water worth more this week or in future weeks?
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After water is allocated, block cost data is used
to determine which hours to run
12
The reservoir system is modeled as a whole for
hydropower optimization