U.S. Delivered Electric Energy Intensity: Are 20-Year Trends

U.S. Delivered Electric Energy Intensity: Are 20-Year Trends Sustainable?

Vanessa Schweizer Department of Engineering & Public Policy

Summer 2008 ORISE Postgraduate Researcher, NETL

[email protected] December 5, 2008

2008 USAEE/IAEE North American Conference

1

Overview

•  Why think beyond aggregate energy intensity?

•  U.S. Energy Intensity Indicators, DOE Office of Energy Efficiency and Renewable Energy (EERE)

•  Findings for delivered electric energy intensity and implications –  Historical ~20-year trends, 1985-2004 –  Projected ~20-year trends, 2006-2030

(AEO ‘08 reference case – industrial sector)

2

Beyond aggregate intensity

•  Improvements to delivered electric energy intensity are about half that of primary energy intensity.

•  Trends for delivered electricity consumption differ by sector.

€

BtuTotal$TotalGDP

=BtuResidential + BtuCommercial + BtuIndustrial + BtuTransportation$ResidentialGDP + $CommercialGDP + $IndustrialGDP + $TransportationGDP

3

EIA, Annual Energy Review 2006

4

http://www1.eere.energy.gov/ba/pba/intensityindicators/index.html

Provides: •  Indices of energy intensity trends that correspond to changes in

the efficiency of energy use (1985-2004) •  Economy-wide indicators

–  Total energy use, delivered energy use, and activity measures at multiple levels

–  Sectoral data •  Transportation •  Industrial •  Residential •  Commercial buildings •  Electricity generation

5

Structure of EERE indicators

Where I is energy intensity of subsector i

E is energy use for subsector i

A is activity for subsector i

Residential and commercial sector intensities:

(energy units)/SF

Industrial sector intensities:

(energy units)/$GDP

i

ii AEI =

EERE (2003). Energy Indicators System: Index Construction Methodology.

6

Why use indices?

Index numbers can be used to compare changes in some quantity from a specific base period (e.g. CPI).

Aggregate energy intensity is influenced by both subsector efficiency gains (component-based energy intensity) and changes to relative shares of subsector activity (structural change).

(Activity)Index e)(Energy UsIndex Intensity)Energy (AggregateIndex =

cture)Index(StruIntensity)Energy based-(ComponentIndex ×=Intensity)Energy (AggregateIndex

Findings for 20-year trends for delivered electric energy intensity and

their implications

7

8

Historical trend: EERE residential sector, delivered electricity

Residential sector components for delivered energy use, 2004 v. 1985

Energy use

Number of households

House size

Migration, type of housing, weather

Energy intensity

Delivered electricity

+65% +28% +19% +1% +7%

Total structure +20%

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

1985

1987

1989

1991

1993

1995

1997

1999

2001

2003

Inde

x (1

985

= 1.

0)Electricity UseTotal HouseholdsHouse SizeStructure (incl. Weather)Electricity Intensity (per square foot)

Source data: EERE (2008).

9

Historical trend: EERE commercial sector, delivered electricity

Commercial sector components for delivered energy use, 2004 v. 1985

Energy use

Floor space

Structure (weather factor)

Energy intensity

Delivered electricity

+74% +35% -2% +29%

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

1985

1987

1989

1991

1993

1995

1997

1999

2001

2003

Inde

x (1

985

= 1.

0)Electricity consumptionFloorspaceElectricity Intensity index (weather-adjusted)Weather factor


10

Historical trend: EERE industrial sector, delivered electricity

Industrial sector components for delivered energy use, 2004 v. 1985

Energy use GDP for industry

Mfg growth wrt non-mfg

Mfg shifts Energy intensity

Delivered electricity +25% +64% +6% -17% -12%

Total structure -13%

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

1985

1987

1989

1991

1993

1995

1997

1999

2001

2003

Inde

x (1

985

= 1.

0)

GDP in industry

Electric Intensity

Structure

Electricity use0.00.10.20.30.40.50.60.70.80.91.01.11.2

19851987

19891991

19931995

19971999

20012003

Inde

x (1

985

= 1.

0)

Relative Mfg/Non-Mfg Grow th

Within Mfg Shifts

Total Structure


11

Projected trend: AEO 08 industrial sector, delivered electricity


Energy use GDP* for industry

Mfg growth* wrt non-mfg

Mfg shifts* Energy intensity*

Delivered electricity +8% +37% +3% -13% -13%


*GDP in value of shipments Source data: AEO ‘08 reference case.

12

Summary of findings Activity (growth) largest contributor to electricity use. Efficiency gains (component intensity) vary: •  Residential: Efficiency gains offset by increased house size

–  1985-2004: +7% delivered electric energy intensity –  1985-2004: +19% electric use attributable to house size

•  Commercial: Efficiency effects unclear (non-existent?) –  1985-2004: +29% delivered electric energy intensity –  Data limitations prevent further refinement

•  Industry: Efficiency and structure effects about even in both historical and projected cases –  1985-2004: -12% energy intensity, -13% structural change –  2006-2030: -13% energy intensity, -10% structural change

Conclusions

•  It appears that fewer gains in delivered electric energy efficiency have been achieved in the residential and commercial buildings sectors.

•  In the residential sector, this analysis suggests that structural policy interventions with respect to housing size should be considered.

•  Indexing methods: An underutilized tool? –  Can be applied to projections from detailed models to enable

comparison with historical trends.

13

14

References Ang B.W. & Zhang, F.Q. 2000, A survey of index decomposition analysis in

energy and environmental studies. Energy, 25, 1149-1176. EERE 2008, Energy Intensity Indicators, viewed 30 June 2008. http://

www1.eere.energy.gov/ba/pba/intensityindicators/ EERE 2003, Energy Indicators System: Index Construction Methodolgy,

viewed 30 June 2008. http://www1.eere.energy.gov/ba/pba/intensityindicators/methodology.html

Liu, N & Ang, B.W. 2007, Factors shaping aggregate energy intensity trend for industry: Energy intensity versus product mix. Energy Economics, 29, 609-635.

Roop J.M. et al., January 2002, Indicators of Energy Intensity in the Economy: A Proposed Methodology, paper presented at the conference of experts convened to settle on appropriate methodology for indicators.

15

Backup slides

16

http://www1.eere.energy.gov/ba/pba/intensityindicators/index.html

Data sources •  Industrial sector: Annual Energy Review 2004, Bureau of Economic

Analysis’ Gross Product Data •  Residential sector: EIA Residential Energy Consumption Survey,

Annual Energy Review 2004 •  Commercial buildings sector: EIA Commercial Buildings Energy

Consumption Survey, Annual Energy Review 2004

Method •  Time series indexes for subsectors generate higher level indexes •  The logarithmic mean Divisia index (LMDI) method is used

17


Residential energy intensity indicators comprised from

•  Trends of housing types within regions

Commercial energy intensity indicators aggregated due to data limitations

Industrial energy intensity indicators comprised from

•  NAICS subsector trends in manufacturing

•  Trends of activity between manufacturing, nonmanufacturing subsectors

EERE (2003). Energy Indicators System: Index Construction Methodology.

18


This means that aggregate energy intensity is defined as

i

ii AEI =

∑∑=

i

i

AE

I

19

Energy-weighted rates of change

From it follows that .

represents total sector activity for component i.

By substitution, yielding the derivative

Dividing both sides by E, the derivative can be rewritten

∑ ∑ ∑++=i i i

ii

iiii dt

dIASdtdSAI

dtdAIS

dtdE

∑∑=

i

i

AE

I EIAEi i

iii ==∑ ∑

AAS i

i =

∑=i

ii IASE

++== ∑ ∑ ∑

i i i

iii

iiiii dt

IdIASdtSdIAS

dtAdIAS

EdtEd

dtdE

Elnlnln1ln1

20

Energy-weighted rates of change

Weights are then normalized to sum to 1.

The first term corresponds to activity effects, the second to structural effects, and the last to subsector intensity.

( )

−=≈==

0,

,

0,,*

lni

Ti

iTiii

iii

wwww

wwEE

EIAS

++== ∑ ∑ ∑

i i i

iii

iiiii dt

IdIASdtSdIAS

dtAdIAS

EdtEd

dtdE

Elnlnln1ln1

21

Time series index calculations

Integrating all terms yields the expression

To obtain the ratio (index) of energy change over time, the multiplicative relationship of the indexes is revealed

∑ ∑∑

+

+

=

i i i

Tii

i

Tii

T

ii

T

II

wSS

wAAw

EE

0,

,*

0,

,*

0

*

0

lnlnlnln

( ) intstract0

.........exp Ι×Ι×Ι=++=EET

22

Detail on the LMDI method The Divisia index •  Can yield a chain-weighted assessment of changes to aggregate

intensity over time •  Assumes that data vary in more or less a continuous fashion when

logarithmic-mean weighting is used •  Permits variable weighting over time •  Permits multiplicative or additive decomposition of relative growth rates •  Does not introduce residual terms (allows perfect decomposition) when

logarithmic-mean weighting is used

23

Component EERE indexes •  Residential

–  Activity: Total households (by building type, region)

–  Structure •  Housing type shift

(share of households by building type)

•  House size (avg. sq. ft. per household)

•  Weather (heating-/cooling-degree day adjustments)

•  Regional shift (share of households by region)

–  Residential intensity (Btu/sq. ft; weather adjusted)

•  Industrial –  Activity: GDP (value added) –  Structure

•  Shifts between manufacturing, non-manufacturing (relative growth of manuf. activity to non-manuf.)

•  Shifts within manufacturing (gross output and value added shifts of selected NAICS sectors)

–  Industrial intensity (Btu/$GDP) •  Commercial

–  Activity: Total square footage –  Structure: Weather –  Commercial intensity

(Btu/sq. ft; weather adjusted)

24


25


26

EERE economy-wide findings Although aggregate energy intensity

decreasing, decreases vary by sector.

I will focus on delivered energy intensity and electric energy intensity for industrial, residential, and commercial sectors.

Five sector energy intensity indices for delivered and total energy, 2004 v. 1985

Transportation Industry Residential buildings

Commercial buildings

Electricity sector

Delivered energy -14.2% -20.2% -17.6% +1.7% -4.7%

Total energy -14.2% -18.7% -9.3% +12.0% NA

http://www1.eere.energy.gov/ba/pba/intensityindicators/delivered_energy.html

27

EERE residential sector – delivered energy


Energy use

Number of households

House size

Migration, type of housing, weather

Energy intensity

Delivered energy +18% +28% +19% -6% -18%

Total structure +12%

http://www1.eere.energy.gov/ba/pba/intensityindicators/delivered_residentiial.html

28

EERE commercial sector – delivered energy


Energy use

Floor space

Structure (weather factor)

Energy intensity

Delivered energy +36% +35% -2% +2%

http://www1.eere.energy.gov/ba/pba/intensityindicators/delivered_residentiial.html

29

EERE industrial sector – delivered energy


Energy use GDP for industry

Mfg growth wrt non-mfg

Mfg shifts Energy intensity

Delivered energy +8% +64% +7.5% -23% -20%


http://www1.eere.energy.gov/ba/pba/intensityindicators/delivered_industrial.html

Documents

U.S. Delivered Electric Energy Intensity: Are 20-Year Trends