Steven Carlson, P.E. CDH Energy Corp. Evansville, WI ACE06 San Antonio, 2006 Development of a Utility Energy Index.

Steven Carlson, P.E.CDH Energy Corp.Evansville, WIwww.cdhenergy.com

ACE06San Antonio, 2006

Development of aUtility Energy Index

Background

Support Benchmarking Efforts• Water• Wastewater

Funding Partnership• AwwaRF• CEC• NYSERDA

Contractors• CDH Energy• Stearns & Wheeler• Consultants from ORNL

– EPA Metric Development

Project Goals

What?• Produce Industry-wide energy performance metrics for:

– Water Utilities– Wastewater Utilities

Why?• Comparison to Peers• Comparison to Ideal• Identify savings potential• Prioritize where to look for improvements

How?• Mimic EPA Energy Star for Buildings Ratings

– Building characteristics– Operating Characteristics

Larger Picture:Benchmarking - History

Business: Total Quality Management"Benchmarking - a continuous, systematic process for evaluating the

products, services, and work processes of organizations that are recognized as representing best practices for the purpose of

organizational improvement."

Michael J. Spendolini, The Benchmarking Book, 1992 Identify actions to improve performance• Identify issues (metrics)• Collect Internal data (baseline)• Collect External data (comparison framework)• Analysis• Implement change• Monitor Impact

Energy Benchmarking

Energy Management Tool How am I doing?

• Relative to previous performance• Relative to other plants in the system• Relative to national average• Relative to a standard (“Best Practices”)

Single Parameter Comparisons

Wastewater Treatment PlantsAwwaRF Survey, 2004 Data, 300 observations

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Annual Energy Cost ($/MG)

Nu

mb

er

of

Pla

nts

Wastewater Treatment PlantsAwwaRF Survey, 2004 Data, 279 observations

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Annual Electricity Use (kWh/MG)

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mb

er

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nts

Define Performance:A Meaningful Metric

Rich dataset for comparison• Compare to what?• Data source?• Comparison method?

Normalize for unmanaged characteristics• Flow• Treatment level• Individual processes

McLaren F1 1994 Acceleration

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Time (sec)

Sp

ee

d (

mp

h)

Metrics

Devised based on type of available data Often normalized to flow Energy Cost ($/MG) Energy Use (kWh/MG)

• Source / Site ?• Electricity / Gas ?

Related to...• Water source, Quality, Distribution topography, etc

Desire to include multiple factors• f (operating conditions, plant loading, process, etc)

Information Model

Available energy use data? Factors impacting energy use? Exogenous vs Endogenous factors?

Volume

Source

Source type

E&G

Treatment

QualityVolume

Processes

E&G

Electricity & Gas

TopographyPressure

Distribution

Volume

E&G

TopographyPressure

Volume

Water QualityWater Source

Water Utility

Population

Literature Review• Population size

– 4,000 utilities serve pop > 10,000

• Source water distinction• Treatment levels (definitions, use frequency)• Existing energy data

– Surface 1,400 kWh/MG (85% pumping)– Ground 1,800 kWh/MG (nearly all pumping)

• Little information on characterizing distribution– Total main length

Population – Treatment

Sample / Response

Source• EPA Safe Drinking Water Information System

Criteria• Population > 10,000

Representation• 85% of national flow• 3,611 Water utilities

Process• Pilot / survey refinement• 1,723 three page surveys mailed• SDWIS address and contact info incomplete

Results• 217 responses (13%)• Additional NY surveys from State effort

Survey 97 parameters queried Water Source

• Average/design/maximum flow• Turbidity• Pumping HP / well depth

Treatment Objectives Process Methods

• Clarification, filtration, etc• Residuals handling

Distribution System• Population & area served• Main length• Pump HP• Elevation range• Pressure / zones

Survey

Energy• Electricity (kWh, kW, cost)

– Source– Treatment– Distribution

• Natural Gas• Other• On-site Generation• Engine-driven pumps

Misc.• Floor area of buildings (administration at plant)• Operational review of utility bills• Extraordinary events• General notes

Analysis

Minimal Filtering• Total kWh > 2,000 kWh/year• Total kWh < 5,000 kWh/MG• Flow, pump HP and main length were reported• 137 observations remain

Dependent Variable• Cost

– Operators interest– Easily combines fuel types– Price variation

• Source Energy– Policy interest– Fuel mix impacts

Log Transformation

Water Utility Energy Use

-4 -2 0 2 4 6 8

LN(Daily Average Flow MGD)

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LN(S

ourc

e E

nerg

y U

se k

Btu

)

Analysis – Single Parameter

Single parameter modelln(Source kBtu) = 15.49 + 0.988 x ln(Flow MGD)R2 = 0.76

Analysis of Variance Sum of Mean Source DF Squares Square F Value Pr > F Model 6 296.61614 49.43602 140.23 <.0001 Error 131 46.18114 0.35253 Corrected Total 137 342.79727 Root MSE 0.59374 R-Square 0.8653 Dependent Mean 17.72028 Adj R-Sq 0.8591 Coeff Var 3.35063 Parameter Estimates Parameter Standard Variable DF Estimate Error t Value Pr > |t| Intercept 1 8.63860 0.38143 22.65 <.0001 ln(flow) 1 0.53504 0.09018 5.93 <.0001 ln(p_flow) 1 -0.06773 0.01567 -4.32 <.0001 ln(total_hp) 1 0.24103 0.07650 3.15 0.0020 ln(raw_hp) 1 0.09625 0.02594 3.71 0.0003 ln(disrib_hp) 1 0.06563 0.02852 2.30 0.0230 ln(main_lngth)1 0.26772 0.08316 3.22 0.0016

Multi-Parameter Model

Improved from 0.76

Flow (total & purchased)Pumping Horsepower (total, raw, distribution)Main Length

Analysis – Critique Model

Energy Use Distribution with Model Residuals

0 25 50 75 100

Y Percentile

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23ln

(So

urc

e k

Btu

)

Modeled Distribution(Raw)

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Ln (modeled energy kBtu/yr)

Percentile Scale

Modeled Distribution(Smoothed Gamma Distribution)

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Ln (modeled energy kBtu/yr)

Percentile Scale

Grading on a Curve

Parameters define peer group curve.

Enter source energy to find score.

1 - Calculate Source Energy Use

Source Energy Use

Site Energy Type Units Site Energy Annual Use x Conversion =

Source Energy Use

(kBtu/yr)

Electricity kWh 2,805,420 11.1 31,140,162

Natural gas therms 3,834 100 383,400

Fuel oil #2 gallons 139 0

Propane gallons 91 0

31,523,562

17.2662

Annual primary energy use (kBtu per yr)

ln (primary energy use)

2 – Predict Model Energy Use and Resulting Score

Predicted Model Energy Use and Adjusted Energy Use

Parameter Units Value

Natural Logarithm Transform

Model Coefficient

Constant 8.6386 = 8.6386

Average Daily Total Flow kGD 6550 8.7872 x 0.5350 = 4.7015

Purchased Daily Flow kGD 0 0.0000 x -0.0677 = 0.0000

Total Pump Horsepower HP 2550 7.8438 x 0.2410 = 1.8906

Raw/Source Pump Horsepower HP 1275 7.1515 x 0.0963 = 0.6883

Distribtion Pump Horsepower HP 1275 7.1515 x 0.0656 = 0.4694

Total Water Main Length miles 150 5.0106 x 0.2677 = 1.3414

= 17.7298

17.7298 ÷ 17.7203 = 1.0005

17.2662 ÷ 1.0005 = 17.2569

= 77

Mean predicted annual energy use (SUM of above)

Adjustment Factor: Divide SUM above by 17.7203 (average utility in model)

Adjusted Energy Use: Divide ln (primary energy use) by adjustment factor

Benchmark Score (Percentile) from Modeled Energy Use Distribution

•Apply utility parameters to model•Adjust model to sample mean•Determine benchmark score

3 - Calculate Target Energy Use

Benchmark Score

Source Energy kBtu/yr

Difference kBtu/yr Diff. (%)

Electricity kWh/MG

Natural Gas

therm/MGFuel Oil Gal/MG

Propane Gal/MG

77 31,523,562 1173 1.6 0 0

99% 1% 0% 0%

10 107,559,870 76,036,308 241% 4004 5.5 0 0

25 73,887,630 42,364,068 134% 2750 3.8 0 0

50 48,970,787 17,447,225 55% 1823 2.5 0 0

75 32,658,521 1,134,959 4% 1216 1.7 0 0

90 22,803,463 (8,720,099) -28% 849 1.2 0 0

Estimated Site Energy*

*Site energy estimate is based on actual proportion of fuel source use at the utility

•Determine energy use for other scores•Apply energy source fraction (site or sample) to restate in site energy units•Determine relative change to reach target

Additional Data Characteristics

Raw / Treatment / Distribution kWh isolation finds more related parameters• n = 93 have two or more categories• n = 35 have all three categories

Raw• Flow• Raw HP• Purchased flow• Raw NTU• Other energy• Pressure filter

Distribution• Flow• Distrib. HP• Distrib. main length

Treatment• Flow• Distrib. Main• Well depth• Raw NTU• Raw HP• Distrib. Pressure• Distrib. Storage• Treat Oxidation• Treat Recarbonation• Treat Aeration• Residual Sand• Residual Gravity• Pressure Filter

Energy Use by Category

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kWh/MG

Uti

liti

es Raw

Treat

Distrib

Categories don’t appear different Difficult to consistently segregate

Source/Treatment/Distribution?

How to Use the Information?

Moving Toward Best Practice

How is it defined?• Target Score / Rating (relative performance)• System performance (rules of thumb)

– Process level energy data & metrics

• Energy Model (absolute standard) How is it achieved?

• Look at system details• Design characteristics (changeable?)• Operational parameters (changeable?)• Management actions (changeable?)

Implementation & Feedback

Using the Metrics

The metric isn’t the destination,Just the mile marker...A hint that potential improvements exists.

Still need to figure out where to go• Apply expertise• Investigate systems• Devise changes• Assess performance

Summary

Project Goals• Collect Data (surveys)• Define Comparison Framework• Create Metrics• Water / Wastewater• Demonstrate Use (case studies)

Metric only gives the score Use information in Applying

Benchmarking process• Investigate why• Motivate action• Confirm project impact• Manage energy use