SAAC Review Michael Schilmoeller Thursday May 19, 2011 SAAC

SAAC Review

Michael SchilmoellerThursday May 19, 2011

SAAC

2

Sources of Uncertainty

Scope of uncertainty

• Fifth Power Plan– Load requirements– Gas price– Hydrogeneration– Electricity price– Forced outage rates– Aluminum price– Carbon allowance cost– Production tax credits– Renewable Energy Credit

(Green tag value)

• Sixth Power Plan– aluminum price and

aluminum smelter loads were removed

– Power plant construction costs

– Technology availability– Conservation costs and

performance

3

CharacteristicsResource Planning?

Reduce size and likelihood of bad outcomes

✔ ✔

Cost – risk tradeoff: reducing risk is a money-losing proposition

✔ ✔

Imperfect Information ✔ ✔

Buying an automobile?

No "do-overs", irreversibility

✔ ✔

4

CharacteristicsResource Planning?

Use of scenarios ✔ ✔

Resource allocations reflect likelihood of scenarios

✔ ✔

Resource allocations reflect severity of scenarios

✔ ✔

… even if "we cannot assign probabilities"

✔ ✔

Buying an automobile?

Some resources in reserve, used only if necessary

✔ ✔

5

Identifying Long-Term Ratepayer Needs

• Why and for whom is a plant built?– For the market or the ratepayer?– Built for independent power producers (IPPs) for sales into the

market, with economic benefits to shareholders?

• How much of the plant is attributable to the ratepayer?– This is usually a capacity requirement consideration– To what extent does risk bear on the size of the plant’s share ?

6

How the NWPCCApproach Differs

• No perfect foresight, use of decision criteria for capacity additions

• Likelihood analysis of large sources of risk (“scenario analysis”)

• Adaptive plans that respond to futures

7

Excel Spinner Graph Model

• Represents one plan responding under each of 750 futures

• Illustrates “scenario analysis on steroids”

8

Modeling Process

The portfolio model

Like

lihoo

d (P

roba

bilit

y) Avg Cost

10000 12500 15000 17500 20000 22500 25000 27500 30000 32500

Power Cost (NPV 2004 $M)->

Risk = average ofcosts> 90% threshold

Like

lihoo

d (P

roba

bilit

y) Avg Cost

10000 12500 15000 17500 20000 22500 25000 27500 30000 32500



Like

lihoo

d (P

roba

bilit

y) Avg CostAvg Cost

10000 12500 15000 17500 20000 22500 25000 27500 30000 3250010000 12500 15000 17500 20000 22500 25000 27500 30000 32500



9

Space of feasible solutions

Finding Robust Plans

Relian

ce on th

e likeliest ou

tcome

Risk Aversion

Efficient Frontier

10

Impact on NPV Costs and Risk

0

10

20

30

40

50

60

70

80

9030

40

50

60

70

80

90

100

110

120

130

140

150

160

170

180

190

200

210

220

230

Freq

uenc

y

Billions of 2006 Constant Dollars

NPV 20-Year Study Costs

Scope of uncertainty

C:\Documents and Settings\Michael Schilmoeller\Desktop\NWPCC - Council\SAAC\Presentation materials\L813 NPV Costs.xlsm

11

Decision Trees

• Estimating the number of branches– Assume possible 3 values (high, medium, low) for each of 9

variables, 80 periods, with two subperiods each; plus 70 possible hydro years, one for each of 20 years, on- and off-peak energy determined by hydro year

– Number of estimates cases, assuming independence: 6,048,000

• Studies, given equal number k of possible values for n uncertainties:

• Impact of adding an uncertainty:

Decision trees & Monte Carlo simulation

iesuncertaint values, , nkkN n

kN

N

1

12

Monte Carlo Simulation

• MC represents the more likely values• The number of samples is determined by the

accuracy requirement for the statistics of interest• The number of samples mk necessary to obtain

a given level of precision in estimates of averages grows much more slowly than the number of variables k:

Decision trees & Monte Carlo simulation

k

k

m

m

k

k 11

13

Monte Carlo Samples

• How many samples are necessary to achieve reasonable cost and risk estimates?

• How precise is the sample mean of the tail, that is, TailVaR90?

Implication to Number of Futures

14

Assumed Distribution

0123456789

10111213141516

109

115

121

127

133

139

145

151

157

163

169

175

181

187

193

199

205

211

217

223

Freq

uenc

y


Tail Risk


C:\Documents and Settings\Michael Schilmoeller\Desktop\NWPCC - Council\SAAC\Presentation materials\L813 NPV Costs 02.xlsm

15Implication to Number of Futures

Dependence of Tail Average on Sample Size

0

10

20

30

40

50

60

70

11

6

11

6.7

5

11

7.5

11

8.2

5

11

9

11

9.7

5

12

0.5

12

1.2

5

12

2

12

2.7

5

12

3.5

12

4.2

5

12

5

12

5.7

5

12

6.5

12

7.2

5

12

8

12

8.7

5

12

9.5

13

0.2

5

13

1

13

1.7

5

75 samples per average

C:\Documents and Settings\Michael Schilmoeller\Desktop\NWPCC - Council\SAAC\Presentation materials\L813 NPV Costs 02.xlsm, worksheet “Samples_75”

σ=1.677

0

10

20

30

40

50

60

70

80

90

30

40

50

60

70

80

90

100

110

120

130

140

150

160

170

180

190

200

210

220

230

Freq

uenc

y



16

Accuracy and Sample Size• Estimated accuracy of TailVaR90 statistic is

still only ± $3.3 B (2σ)!*

0

10

20

30

40

50

60

70

80

90

30

40

50

60

70

80

90

100

110

120

130

140

150

160

170

180

190

200

210

220

230

Freq

uenc

y




0

10

20

30

40

50

60

70

116

116.

7511

7.5

118.

25 119

119.

7512

0.5

121.

25 122

122.

7512

3.5

124.

25 125

125.

7512

6.5

127.

25 128

128.

7512

9.5

130.

25 131

131.

75

75 samples per average

*Stay tuned to see why the precision is actually 1000x better than this!

17

Accuracy Relative to the Efficient Frontier

123200

124200

125200

126200

127200

128200

129200

77000 78000 79000 80000 81000 82000 83000

Ris

k (N

PV

$2

00

6 M

)

Cost (NPV $2006 M)

L813

L813 L813 Frontier

C:\Backups\Plan 6\Studies\L813\Analysis of Optimization Run_L813vL811.xls


18

Finding the Best Plan

• Each plan is exposed to exactly the same set of futures, except for electricity price

• Look for the plan that minimizes cost and risk

• Challenge: there may be many plans (Sixth Plan possible resource portfolios:1.3 x 1031)

Implication to Number of Plans

19

Space of feasible solutions

The Set of Plans Precedes the Efficient Frontier

Relian

ce on th

e likeliest ou

tcome

Risk Aversion

Efficient Frontier


20

Finding the “Best” Plan

155600

155800

156000

156200

156400

156600

156800

157000

0 500

1000

1500

2000

2500

3000

3500

4000

4500

5000

5500

6000

6500

7000

7500

8000Ta

ilVar

90 ($

M N

PV)

simulation number

Reduction in TailVar90with increasing

simulations (plans)

C:\Documents and Settings\Michael Schilmoeller\Desktop\NWPCC - Council\SAAC\Presentation materials\Asymptotic reduction in risk with increasing plans.xlsm


21

How Many 20-Year Studies?

• How long would this take on the Council’s Aurora2 server?

studiesyear -20 10 2.625

750 3500

futures plans

6

n

Implication to Computational Burden

22

• Assume a benchmark machine can process 20-year studies as fast:– Xeon 5365, 3.0 MHz, L2 Cache 2x4, 4 cores/4

threads per core– 38 GFLOPS on the LinPack standard– To the extent this machine underperforms the Council

server, the time estimate would be longer

• Total time requirement for one study on the Tianhe-1A: 3.54 days (3 days, 12 hours, 51 minutes) and estimated cost $37,318

On the World’s Fastest Machine

Implication to Computational Burden

23

How the RPM Satisfies the Requirements of a Risk Model• Statistical distributions of hourly data

– Estimating hourly cost and generation– Application to limited-energy resources– The price duration curve and the revenue curve

• Valuation costing• An open-system models• Unit aggregation• Performance and precision

24

Estimating Energy Generation

Price duration curve (PDC)

Statistical distributions

25

Gross Value of Resources Using Statistical Parameters of

Distributions

e

ee

ge

ee

g

e

ge

dd

ppd

(h))(p

p

p

NN

dNpdNpc

12

1

21

2/)/ln(

ln ofdeviation standard is

price gas theis

pricey electricit average theis

variablerandom )1,0( afor CDF theis

where

(4) )()( Assumes:

1) prices are lognormally distributed

2) 1MW capacity

3) No outages

V


26

Estimating Energy Generation

*

*

1)(CDFcf

)(CDF

Calculus) of Thm (Fund

)(CDF

*

*

gg

gg

g

ppgHg

gH

ppg

e

P

eH

p

V

NCp

pNCp

V

dppNCV

Applied to equation (4), this gives us a closed-form evaluation of the capacity factor and energy.


27

Implementation in the RPM

• Distributions represent hourly prices for electricity and fuel over hydro year quarters, on- and off-peak– Sept-Nov, Dec-Feb, Mar-May, June-Aug– Conventional 6x16 definition– Use of “standard months”

• Easily verified with chronological model• Execution time <30µsecs• 56 plants x 80 periods x 2 subperiods


28

Energy-Limited Dispatch


29

Application of Revenue Curve Equilibrium Prices


Cu

mu

lati

ve M

ark

et

Pri

ce

(mil

ls/k

W)

Time (hours) 8760

Diesel ECC

SCCT ECC

CCCT ECC

Net revenue for the diesel (negative)

h* for diesel

Source: page 5, Figure 3, Q:\MS\Markets and Prices\Market Price Theory MJS\Price Relationships in Equilibrium2.doc

30

“Valuation” CostingComplications from correlation of fuel price, energy, market prices

priceLoads (solid) & resources (grayed)

Valuation Costing

)( imi

im ppqQpc --= åOnly correlations are now those with the market

31

Open-System Models

?

Open-System Models

32

Modeling Evolution

• Problems with open-system production cost models– valuing imports and exports– desire to understand the implications of events

outside the “bubble”

• As computers became more powerful and less expensive, closed-system hourly models became more popular– better representation of operational costs and

constraints (start-up, ramps, etc.)– more intuitive

Open-System Models

33

Open Systems Models• The treatment of the Region as an island seems

like a throw-back– We give up insight into how events and

circumstances outside the region affect us– We give up some dynamic feedback

• Open systems models, however, assist us to isolate the costs and risks of participant we call the “regional ratepayer”

• Any risk model must be an open-system model

Open-System Models

34

The Closed- Electricity System Model

fuel price+εi

dispatchprice

energygeneration

energyrequire-ments

market price +εi for electricity

Only one electricity price balances requirements and generation

• If fuel price is the only “independent” variable, the assumed source of uncertainty, electricity price will move in perfect correlation

• That is, outside influences drive the results• We are back to an open system

Open-System Models

35

The RPM Convention

• Respect the first law of thermodynamics: energy generated and used must balance

• The link to the outside world is import and export to areas outside the region

• Import (export) is the “free variable” that permits the system to balance generation and accommodate all sources of uncertainty

• We assure balance by controlling generation through electricity price. The model finds a suitable price by iteration.

Open-System Models

36

Equilibrium search

Open-System Models

37

Unit Aggregation

0.00

2.00

4.00

6.00

8.00

10.00

12.00

4000 5000 6000 7000 8000 9000 10000 11000 12000 13000 14000 15000 16000 17000

VO

M ($

/MW

h)

Heat Rate (BTU/kWh)

West 1 West 2 West 3

West 4 Beaver East 4

East 5 East 7 East 8

Hermiston Ignore East 1

• Forty-three dispatchable regional gas-fired generation units are aggregated by heat rate and variable operation cost

• The following illustration assumes $4.00/MMBTU gas price for scaling

Source: C:\Backups\Plan 6\Studies\Data Development\Resources\Existing Non-Hydro\100526 Update\Cluster_Chart_100528_183006.xls

Unit Aggregation

38

Cluster Analysis

11

30

12

19

13

05

12

90

11

31

12

46

12

47 1

24

81

02

11

04

10

20

14

67

14

68

16

50

16

51

11

98

11

99

12

01

12

02

10

23

11

36

10

28

14

75

14

43

13

68

12

00

12

28

10

89 15

71

14

11

10

00

12

04

12

03

10

01

05

41

79

71

29

11

29

21

40

21

40

3

01

23

45

Dendrogram of agnes(x = Both_Units, diss = FALSE, metric = "manhattan", stand = TRUE)

Agglomerative Coefficient = 0.98Both_Units

He

igh

t

Source: C:\Backups\Plan 6\Studies\Data Development\Resources\Existing Non-Hydro\100526 Update\R Agnes cluster analysis\Cluster Analysis on units.doc

Unit Aggregation

39

Performance

• The RPM performs a 20-year simulation of one plan under one future in 0.4 seconds

• A server and nine worker computers provide “trivially parallel” processing on bundles of futures. A master unit summarizes and hosts the optimizer.

• The distributed computation system completes simulations for one plan under the 750 futures in 30 seconds

• Results for 3500 plans (2.6 million 20-year studies) require about 29 hours

Performance and Precision

40

Precision

Source: email from Schilmoeller, Michael, Monday, December 14, 2009 12:01 PM, to Power Planning Division, based on Q:\SixthPlan\AdminRecord\t6 Regional Portfolio Model\L812\Analysis of Optimization Run_L812.xls

Performance and Precision

41

Choice of Excel as a Platform• The importance of transparency and

accessibility, availability of diagnostics• Olivia• The ability of Olivia to write VBA code for

the model• RPM’s layout of data and formulas • High-performance Excel

– XLLs– Carefully controlled calculations

• System requirements• Crystal Ball and CB Turbo

42

The Efficient Frontier

123

124

125

126

127

128

129

77 78 79 80 81 82 83

Th

ou

sa

nd

s

Thousands

Side Effects

Inef

fect

ive

source: \EUCI 100323 Presentation\Efficient Frontier\EUCI 100323 01.xls

123

124

125

126

127

128

129

77 78 79 80 81 82 83

Th

ou

sa

nd

s

Thousands

Side Effects

Inef

fect

ive

source: \EUCI 100323 Presentation\Efficient Frontier\EUCI 100323 01.xls

43

What does the Efficient Frontier Tell Us?• The Efficient Frontier does not

tell us what to do• The Efficient Frontier tells us

what not to do• Most useful if there are a large

number of choices

44

End