systematic review and harmonization of life cycle ghg ... · – chapter 1 renewable energy and...

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Systematic Review and Harmonization of Life Cycle GHG Emission Estimates for Electricity Generation Technologies

WREF Forum: Sustainability of Renewable Electricity Generation Technologies

Garvin Heath

May 14, 2012 NREL/PR-6A20-54871

NATIONAL RENEWABLE ENERGY LABORATORY 2

Life cycle assessment (LCA) – quantifies resource consumption, energy use, and emissions, from cradle-to-grave

• Practiced for 40 years • Methods codified in standards (e.g.,

ISO) and guidelines, though some methodological issues persist

Selected by IPCC as most appropriate basis for consistent comparison of renewable and conventional energy technologies in Special Report on Renewables

GHG Mitigation Benefit of Renewables: Quantifying Attributable GHG Emissions

Source: IPCC SRREN

NATIONAL RENEWABLE ENERGY LABORATORY

Need for Systematic Review & Meta-Analysis

Context – Considerable previous work in assessing life cycle

environmental impacts of electricity generation technologies

• Scrutinized > 2,000 references to date – Lack of holistic evaluation of this work in a

consistent manner, especially across technologies – Methodological inconsistency has hampered

cross-study comparisons – Result is impression amongst decision makers that

state of the science is inconclusive

3


Need for Systematic Review & Meta-Analysis

Context – Considerable previous work in assessing life cycle

environmental impacts of electricity generation technologies

• Scrutinized > 2,000 references to date – Lack of holistic evaluation of this work in a

consistent manner, especially across technologies – Methodological inconsistency has hampered

cross-study comparisons – Result is impression amongst decision makers that

state of the science is inconclusive LCA Harmonization Study goals

– Understand range of published results – Reduce uncertainty and inconsistency around

estimates of environmental impacts of electricity generation technologies

– Make the information useful to decision makers in the near term

4


Impact of Research Contribution to important studies

– IPCC SRREN: comprehensive assessment of estimates of GHG emissions from electricity generation technologies (renewable and conventional)

• Also, transportation fuels, land use change and water

Contribution to science – Special issue of Journal of Industrial

Ecology on meta-analysis of LCAs • Publication date early May, 2012 • 8 articles from project in special issue

– Special sessions at International LCA conferences on meta-analysis of energy LCAs

5


Literature Review Methods and Caveats Methods

Literature collection – > 2,000 reviewed – Exhaustive search of English

language publications – All pub types (articles, reports,

conf papers, theses…) Literature screening

– Quality methods of LCA and GHG accounting

– Transparency of reporting inputs, assumptions, and results

– Relevance of evaluated technology today/near future

Caveats Distributions of literature estimates

– Not assessment of likelihood – Not a prediction, though newer

designs included – Might not capture true min., max.,

or central tendency (countered by repeated study of many technologies)

Limited to available literature – Not all technology variations

studied or studied frequently Technologies considered in isolation

– System impacts typically not studied (↑reserves for ↑ wind)

– Typically do not consider fleet of existing units (could weight technologies by deployment to estimate)

– Land use change not considered (or removed)

6


Literature Review Counts

Note: Some double counting is inherent in the Totals given that some references investigate more than one technology. Note2: The counts represent progress to-date and will differ from final results once the project is completed.

Technology Category References Reviewed

Passing the First Screen

Passing the Second Screen

Providing Life Cycle GHG Emissions Estimates

Biopower 369 162 84 52 Coal 273 192 110 52 Concentrating solar power 125 45 19 13 Geothermal 46 24 9 6 Hydro 89 45 11 11 Natural gas 251 157 77 40 Nuclear 249 196 64 32 Ocean energy 64 30 6 5 Oil 68 45 19 10 Photovoltaics 400 239 75 26 Wind 231 174 72 49 Totals 2165 1309 546 296 % of total reviewed 60% 25% 14% % of those passing first screen 42% 23% % of those passing second screen 54%

7


Large Variability for Some Technologies, RE Emissions Considerably Lower than Fossil

8

IPCC SRREN SPM Fig 8


Published Estimates for Harmonized Technologies

9


Methodological Harmonization Reduces Variability and Clarifies Central Tendency

10


Acknowledgements

11

Funding from US DOE / EERE and EPRI Project Leadership: Garvin Heath and Margaret Mann Contributors: NREL: Ethan Warner, Patrick O'Donoughue, Stacey Dolan, David Hsu, John Burkhardt, Pamala Sawyer, Martin Vorum, Elliot Cohen BNL (PV): Vasilis Fthenakis, Hyung Chul Kim, Symbiotic Engineering (coal): Michael Whitaker

NATIONAL RENEWABLE ENERGY LABORATORY 12

Supplemental Slides


IPCC SRREN Ch. 2: Biopower

13


IPCC SRREN Ch. 3: PV

14


IPCC SRREN Ch. 3: CSP

15


IPCC SRREN Ch. 4: Geothermal

16


IPCC SRREN Ch. 5: Hydropower

17


IPCC SRREN Ch. 6: Ocean Energy

18


IPCC SRREN Ch. 7: Wind

19


Natural Gas

20

0

200

400

600

800

1,000

1,200

Published Harmonized Published Harmonized Published Harmonized

Life

Cyc

le G

HG E

mis

sion

s (g

CO2e

/kW

h)

Estimates: 54 14 40 References: 36 5 36

KEY TO BOX PLOT MAX 75th

MEDIAN 25th MIN

All Tech NGCT NGCC


Coal

21

600

800

1,000

1,200

1,400

1,600

1,800

As-Published Harmonized As-Published Harmonized As-Published Harmonized As-Published Harmonized As-Published Harmonized

Life

Cyc

le G

HG E

mis

sion

s (g

CO

2e/k

Wh)

Count: 164 108 19 14 23References: 53 40 16 10 13

KEY TO BOX PLOTMAX

75th

MEDIAN

25th

MIN

All Four Technologies Subcritical IGCC Fluidized Bed Supercritical


CSP

22


Wind

23


Nuclear

24

0

50

100

150

200

250

As Reported Harmonized As Reported Harmonized As Reported Harmonized

LWR PWR BWR

Life

Cyc

le G

HG

Em

issio

ns (

g C

O2e

/kW

h)

Count of Estimates: 99 59 25 Count of References: 27 15 7


C-Si PV

25


Harmonization Methods

Types of Harmonization

System Harmonization – System boundaries – GWPs – GWIs (full harmonization)

Technological Harmonization – Plant performance

characteristics (eff., CF,) – Lifetime

Geographic Harmonization – Solar resource

Method

1. Proportional adjustment of denominator of:

2. Addition or subtraction for system boundary

3. Full harmonization: Recalculation of GWI x material mass (activity) for whole LCI

26

GWP weightedlifetimeGHGGHG

I PR LT Aη

−

=× × × ×


Special Report on Renewable Energy Sources and Climate Change Mitigation

27

– Summary for Policy Makers (SPM) – Technical Summary – Chapter 1 Renewable Energy and Climate Change – Chapter 2 Bioenergy – Chapter 3 Direct Solar Energy – Chapter 4 Geothermal Energy – Chapter 5 Hydropower – Chapter 6 Ocean Energy – Chapter 7 Wind Energy – Chapter 8 Integration of Renewable Energy into Present and Future

Energy Systems – Chapter 9 Renewable Energy in the Context of Sustainable

Development – Chapter 10 Mitigation Potential and Costs – Chapter 11 Policy, Financing and Implementation

– Annex II Methodology

Systematic Review and Harmonization of Life Cycle GHG Emission Estimates for Electricity Generation TechnologiesGHG Mitigation Benefit of Renewables: Quantifying Attributable GHG EmissionsNeed for Systematic Review & Meta-AnalysisNeed for Systematic Review & Meta-AnalysisImpact of Research Literature Review Methods and CaveatsLiterature Review CountsLarge Variability for Some Technologies, �RE Emissions Considerably Lower than FossilPublished Estimates for Harmonized TechnologiesMethodological Harmonization Reduces Variability and Clarifies Central TendencyAcknowledgementsSupplemental SlidesIPCC SRREN Ch. 2: Biopower IPCC SRREN Ch. 3: PV IPCC SRREN Ch. 3: CSP IPCC SRREN Ch. 4: Geothermal IPCC SRREN Ch. 5: Hydropower IPCC SRREN Ch. 6: Ocean Energy IPCC SRREN Ch. 7: Wind Natural GasCoalCSP WindNuclearC-Si PVHarmonization MethodsSpecial Report on Renewable Energy Sources and Climate Change Mitigation

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