FLEXIBLE POWER GRID RESOURCES —AN NEA ANALYSIS

Charlie Barnhart, Mik Carbajales-Dale and Sally Benson

NEA@Stanford April 1, 2015

A need for power grid flexibility

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BPA demand, solar insolation and wind data, 5 minute intervals, April 2010

1.3 GW of storage by 2020 in CA “California adopts first-in-nation energy storage plan” October, 2014 "Storage really is the game changer in the electric industry. And while this new policy is not without risk, the potential rewards are enormous.” -Commissioner Mike Florio

Dave Fribush of PG&E, shows off the utility's new Yerba Buena battery energy storage project, Tuesday morning Oct. 15, 2013 in the hills above Evergreen Valley College in San Jose, Calif. ((Karl Mondon/Bay Area News Group))

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Energiewende Germany Finances Major Push Into Home Battery Storage for Solar

“… the program targets lead-acid and lithium-ion batteries.”

"As Germany looks out to 2050, the expectation is that the penetration of renewables could be as large as 80 to 90 percent," Kaun (Ben Kaun, EPRI) said. Coping with variability and the times when renewable production exceeds grid demand raises the perceived value of storing solar and wind in the form of hydrogen, a dispatchable resource. "There is significant loss in conversion from solar to hydrogen," he said. "But it's viewed as being better than zero” if faced with curtailment.

RenewEconomy, Giles Parkinson November 8, 2014 Energy Storage: A Different View from Germany, June 2014 Laurie Reese

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Capital Costs 5

The role NEA can play in making good policy decisions…

• What are the energetic and carbon costs of storage?

• How do these costs compare to existing flexible grid resources?

• How can we utilize storage technologies in ways that facilitate renewable proliferation in the spirit of environmental stewardship?

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Photo: Karim Nafatni

Flexible Generation Pathways

Stored Renewables

Responsive Gas

Generation

Grid Storage

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How does the energetic performance of stored renewables compare with

energetic performance of natural gas generation?

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Methodology • Developed a theoretical framework to combine the energetic

costs and carbon intensities of electricity generation resources and electrical energy storage technologies. • Track energy expenditures and flows as well as carbon emissions for

energy resources and storage technologies. • Data were obtained from several sources:

• Energy storage and energy generation life cycle assessment studies. • Data were divided into ‘cradle-to-gate’ and operational components.

Energy expenditures and carbon emissions associated with decommissioning and recycling were not considered.

• Data are harmonized to Cradle-to-Gate when possible but are uncertain.

• This work focused on building the theoretical framework.

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Carbon and Energy Intensity of Storage

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Grid-Scale Storage Technologies • safe • inexpensive • made from abundant

materials • high cycle-life • high round-trip efficiency

• Lead Acid (PbA) • Sodium Sulfur (NaS) • Flow (ZnBr, VRB) • Compressed air energy

storage (CAES) • Pumped hydroelectric

storage (PHS)

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Embodied Energy Requirements

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Energy throughput

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Life Cycle Storage CO2eq Emissions

Sources: Sullivan and Gaines, 2000 Denholm and Kulcinski, 2004 eGRID, EPA, 2009

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Source Carbon Multiplier Storage Tech

AC-AC efficiency

Source Carbon Multiplier

PbA 0.9 1.11 Li-Ion 0.9 1.11 NaS 0.75 1.33 CAES 1.36 0.74 PHS 0.85 1.18 VRB 0.75 1.33

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Resource Carbon and Energy Intensity

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The Generation Resource Footprint Energy Intensity of Gas, PV and Wind

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Energy Intensity data were obtained from numerous sources. Only post-2000 values were considered. Data were converted to electrical energy values by an energy quality correction value of 0.3 where appropriate. Gas: n=14 from 5 sources PV: n=24 from 27 sources Wind: n=42 from 4 sources (Kubiszewski et al., 2009 was in itself a meta-analysis considering 119 turbines)

Carbon Life Cycle Assessment (CO2eq)

~60% - 70% • Raw Materials Extraction • Materials Production • Module/System/Plant

Component Manufacture • Installation

~21% - 26% • Power Generation • System/Plant Operation • System Maintenance

~5% - 20% • Decommissioning • Disposal

0.1% • Raw Materials Extraction • Materials Production • System/Plant Component

Manufacture

99.8% • Fuel Cycle (13%) • Combustion (87%)

0.1% • Decommissioning • Disposal

86% • Raw Materials Extraction • Materials Production • Parts Manufacture • Wind/Turbine/Farm

Construction

9% • Power Generation • System/Plant Operation • System Maintenance

5% • Decommissioning • Disposal

Upstream Operational Downstream

NREL LCA Harmonization Studies (2012-2014) 420 to 670

O’Donoughue et al., 2014

3 to 45 Dolan and Heath, 2012

39 to 49 Hsu et al., 2012

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kg CO2eq/MWh

Flexible Electrical Energy Systems

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Big Ideas • Flexible power grid technologies affect the carbon and

energy intensity of the power grid • The energy resource predominates energy and carbon

intensities • Technological solutions not only need to be affordable,

they need to be aligned with the principles of environmental stewardship that guided policy makers to spur the use of renewable energy resources.

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Discussion and Conclusions

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• With today’s flexible grid technologies we should… • Store energy with efficient and long-lived technologies like Li-Ion

and PHS • Consider curtailing wind before storing it during times of oversupply • Employ solar to reduce carbon emissions • Use efficient high power capacity gas turbines • Promote swing capabilities of NGCC-CCS • Avoid storing grid power • Avoid older inefficient low capacity gas turbines • Avoid conventional PbA Storage

• R&D focus for tomorrow’s technologies should… • Focus on improving battery cycle life and efficiency • NGCC-CCS is a low carbon high efficiency technology, technology

for storage, capture and variable generation is needed.

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Data Sources for storage technologies

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• T. Reddy and D. Linden, 2010 • C. Rydh and B. Sanden, 2005 • Denholm and Kulcinski, 2004 • J.L. Sullivan and L. Gaines, 2010

Natural Gas Energy Data and Calculations

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US Power Grid Energy Data and Calculations

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How does storage affect the grid-wide EROI?

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