NREL is a national laboratory of the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, operated by 

Renewable Electricity Futures: Exploratio

renewable electricity penetration in the United S

Maureen Hand, NRELEd DeMeo, RECS Inc.Donna Hostick, PNNLTrieu Mai, NRELC. Adam Schlosser, MIT

World Renewable Energy ForumDenver, ColoradoMay 17, 2012

NREL/PR‐6A20‐54948
Renewable Electricity Futures Intr• Renewable electricity generation characteristics are 

o Low‐ or no‐criteria air emissions that affect public heao Low‐carbon emission that affect climate changeo Low‐ or no‐fuel costs that mitigate risk of fuel price voo Domestic, sustainable source of energy that enhances 

•

... which motivates analysis to explore potential cha

a high renewable U.S. electric sector – Renewable E

Futures

• RE Futures is a rigorous analytical study that begins 

question:

o Can the U.S. power system supply electricity to meet c

demand on an hourly basis with high levels of renewab

including variable wind and solar generation?
RE Futures Study Organization

Project Leadership Team Members

NREL, MIT, RECS

DOE-EERE/OE

Steering 

Committee

Technology Teams (Vo

•Biopower•Geothermal Energy•Hydropower•Ocean Energy•Solar Energy•Wind Energy•Storage

Electric System Teams

•End-use electricity (Vol. 3)•Electric Power System Operations and Transmission (Vol. 4)

Supporting Modeling Analysis (Vol. 1)

• Over 140 Individual Contributors

• Over 50 Participating Organizations (Selected List)

o National Laboratories: INL, LBNL, NREL, ORNL, PNNL, SNLo Industry: Midwest Independent System Operator, Western Interstate Energ

Bank, Xcel Energy, Vestas Wind Systems, RES Americas, Black &Veatch

o Universities: Massachusetts Institute of Technology, University College Dub

Colorado, Virginia Polytechnic Institute and University, Texas Tech

o NGOs: Electric Power Research Institute, Environmental Defense Fund, Am

Energy‐Efficient Economy, Energy Foundation
Renewable Electricity Futures Intro

RE Futures does.... RE Futures does not...

Identify commercially available RE

generation technology combinations that

meet up to 80% or more of projected 2050

electricity demand in every hour of the year

Fully evaluate power sys

explore market mechan

RE generation

Identify electric sector characteristics

associated with specific levels of RE

generation

Evaluate policy efforts thgeneration

Demonstrate US electric sector carbon

emissions reductions

Assess optimal pathwaycarbon futures

Explore a select number of economic,

environmental and social impacts

Conduct comprehensive 

analysis

Illustrate a low‐carbon, domestic,sustainable, low‐fossil fuel electric sector

concept

Provide the final word o

generation, but encoura

investigation
Forum outline• Renewable Electricity Technologies – Ed D

(RECS Inc.)

• End‐Use Electricity Demand – Donna Hos

• Electric Sector Modeling – Trieu Mai (NR• Greenhouse Gas, Water & Other Environ

Implications – C. Adam Schlosser (MIT)

• Summary – Maureen Hand (NREL)
Renewable Electricity

Technologies
Current State of RE Power Genera

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1980

1981

1982

1983

1984

1985

1986

1987

1988

1989

1990

1991

1992

1993

1994

1995

Annual Installed Capacity (MW‐AC)

Annual PV Capacity Cumulative PV Capacity 

Wind So

• In 2010, 10% of U.S. electricity from renewables

o Hydropower = 6.4% (77 GW)o Wind = 2.4% (40 GW)o Biopower = 0.7% (6.7 GW)o Geothermal = 0.4% (3.4 GW)o Solar = 0.05% (2.6 GW)

• RE deployment has grown rapidly in recent years, especia

solar technologies
RE Resources Are Large and Widely Di• Total U.S. installed electricity generation capacit

• Technical resource potential shown, not econom

Bio ~100 GWCSP ~37,000 GWGeo ~36 GW(Hydrothermal only)
RE Options Have A Wide Range of Char

Technology Variability Time 

Scale

Dispatchability Geographic Diversity 

Potential

Predict

Bioenergy Seasons +++ + ++ PV Minutes to years + ++ + 

CSP (with thermal storage)

Hours to years ++ + ++ 

Geothermal (Hydrothermal)

Years +++ NA ++ 

Hydropower(run of river)

Hours to years ++ + ++ 

Hydropower (reservoir)

Days to years +++ + ++ 

Wind Minutes to years + ++ + 

• Some are dispatchable like conventional fossil plants (

• Others show variability and uncertainty (e.g., wind, PV

• Most are widely distributed geographically (except ge

hydrothermal)
Other Key RE Deployment Iss

• Area requirements:

o Gross estimate for RE Futures

scenarios: < 3% of US land area

o About half used for biopowero Majority of remainder for wind,

but only about 5% is actually

disturbed

Roug

Total Con

REF 80% 

Biomass All Other All Other Transmis2009 Cor

Major RoGolf Cour

• Other siting issues:

o Streamlined permitting processes neededo Wildlife and habitat disturbance concernso Public acceptance for generation and transmission

• Critical materials:

o Rare earths for permanent‐magnet generatorso Some PV materials (e.g., In, Te, Cd)

* USDA 2010, 
End‐use Electricity De
Historical and Projected Demand

Sector High-Demand Projection Low-Demand ProjecResidential 2% decline in intensity over 2010 levels 30% decline in intensCommercial 5% increase in intensity over 2010 levels 32% decline in intensIndustrial 35% decline in intensity over 2010 levels 50% decline in intensTransportation <3% PHEV penetration 40% of vehicle sales 
Electricity Intensity Projections are Compar

Other Studies

Residential (electricity use per household)

Commercial (electricity use per square foot) Industrial (electricity us

• Building sector p

focused on who

intensities

• Industrial sector 

relied on cases d

EIA
Demand‐Side Flexibility Increases the Poten

to Meet Electricity Requirements

• Regional, seasonal, and diurnal variability 

electricity requirements impact the potent

production

o Electricity use projections were converted to 

hourly system load profiles

• Demand‐side options considered:

o Thermal (cooling) storage to shift commercial 

conditioning loads based on regional cost sup

o Regional demand response (interruptible load

curves were developed to meet operating res

o Dynamic scheduling of electric vehicle chargin

over 40% of PHEV load was under utility‐cont

charging
Electric Sector Model
RE Futures Modeling Framework

Technology cost & performanceResource availabilityDemand projectionDemand-side technologiesGrid operationsTransmission costs

Black & VeatchTechnology TeamsFlexible ResourcesEnd-Use ElectricitySystem OperationsTransmission

rooftop PVpenetration

20

of gen

Implications

GHG Emissions

Water Use

Land Use

Direct Costs
Transitioning to High Renewable E

80% RE‐ITI scenario

• 80% RE generation in 2050 requires ~20 GW/year between 2011

GW/year in 2041‐2050 (higher under High‐Demand scenario)

• These installation rates are higher than U.S. capacity additions i

and 2009 (11 GW) and would place challenges on RE industries

• Recent growth in the U.S. and globally demonstrate the scalabil

industries, e.g. U.S. wind industry grew rapidly during the last d

PV production capacity comparable with scenarios
All Regions Could Contribute to RE Su
Multiple Technology Pathways Exist• Over two dozen scenarios modeled

• Technology deployment depends on scenario assum

all cases examined, RE resources exist to compensatvariations in access to transmission, grid flexibility, r

availability, technology costs, and electricity deman

• Future RE technology cost and performance is a maj

deployment driver
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Power (GW)

Date

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Power (GW)

Date

CurtaWindPVGas CGas CHydrCSPBiopCoalGeotNucleShiftLoad

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Apr-27 00:00

A

pr-27 12:00

A

pr-28 00:00

A

pr-28 12:00

A

pr-29 00:00

A

pr-29 12:00

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pr-30 00:00

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pr-30 12:00

Power (GW)

Date

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Apr-27 00:00

A

pr-27 12:00

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pr-28 00:00

A

pr-28 12:00

A

pr-29 00:00

A

pr-29 12:00

A

pr-30 00:00

A

pr-30 12:00

Power (GW)

Date

CurtaWindPVGas Gas HydrCSPBiopCoalGeoNuclShiftLoad

Electricity Supply & Demand Can Be Balanc

Hour of the Year *

80% RE‐ITI scenario

Baseline scenario

Peak

Off‐Peak
Transmission & System Flexibility Help SuppRenewable Integration

80% RE‐ITI scenario

• Maintaining sufficient capacity on the system for planning reser

• Relying on demand‐side interruptible load, conventional genera

natural gas generators), and storage to manage increased variab

• Mitigating curtailment with storage and controlled charging of e

• Relying on the dispatchability of coal, NG, and RE (e.g. biopowe

CSP with storage)

• Transmitting greater amounts of power over longer distances to 

electricity demand profiles and aggregate variability of wind an
Incremental Direct Costs of Achieving High 

Penetration are Similar to Other Low Carbo

• The incremental costs of the RE Futures scenarios are comparab

and clean energy scenarios, evaluated by EIA and EPA, with sim

reductions (~40% reduction by 2030, ~80% reduction by 2050)

• Baseline scenario assumes no new policies, expiration of RE ince

limited coal retirements

• Further technological advances can reduce these incremental co

• Incremental costs should be weighed with other implications of 

deployment

$0

$10$20$30$40$50$60

2010 2020 2030 2040 

Real 2009$/MWh

Year

Increase in retail electricity price relative to reference/baseline

Core 80% RE (ReEDS) EIA 2009cEPA 2009 EIA 2010cEPA 2010 EIA 2011b

EIA 2011c
Greenhouse Gas, Wat

Other EnvironmentaImplications
Achieving 80% RE Reduces Annual Power S

Emissions by ~80%

• Combustion‐only and full life‐cycle basis

• Other considerations include: criteria air pollu

use, natural gas price volatility, and power sec
Water Use Factors Generally Lower for RE v

Technologies

Withdrawal (gal/MWh) Consumptive 

Renewable Technologies
Achieving 80% RE reduces power sector wate

Change in 2050 water consum

80% RE‐ITI and Baseline 
Summary
Future work needed• A comprehensive cost‐benefit analysis to better understand 

and environmental implications of high renewable electricit

to today’s electricity system largely based on conventional t

alternative futures in which other sources of clean energy ar

scale

• Further investigation of the more complete set of issues aro

of power system reliability because RE Futures only partially 

implications of high penetrations of renewable energy for sy

• Improved understanding of the institutional challenges asso

integration of high levels of renewable electricity, including 

market mechanisms that enable the emergence of flexible tsolutions and mitigate market risks for a range of stakeholde

project developers.

• Analysis of the role and implications of energy research and 

activities in accelerating technology advancements and in br

portfolio of economically viable future renewable energy su

supply‐ and demand‐side flexibility tools
Key Results: Renewable Electricity 

• Commercially available renewable generation technologies, are more than 

80% of U.S. electricity in 2050 while maintaining an operable electric pow

• All regions of the country could contribute substantial renewable electrici

• Multiple technology pathways exist to compensate for constraints limiting 

of resources, power transmission infrastructure or grid flexibility.

• Annual renewable capacity additions are consistent with current global pr

no insurmountable long‐term constraints to manufacturing capacity, mate

availability were identified.

• Electricity supply and demand can be balanced in every hour of the year i

electricity from renewable resources (50% variable wind and PV).

• New challenges to power system planning and operation include managem

periods and curtailment of excess electricity generation.

• A more flexible system that utilizes a broad portfolio of supply‐ and dema

is needed to accommodate increasing levels of renewable electricity gene

• Additional transmission infrastructure is required to connect generation fr

remote renewable resources to load centers, enable resource and reserve 

distances, and smooth output profiles of variable generators by enabling g

diversity.

• A direct incremental cost associated with high levels of renewable generat

continued evolution of today’s conventional generation system, is reflecte

electricity prices. Direct environmental and social implications are also ass

renewable futures examined, including carbon emission reductions.

• With higher demand growth, high levels of renewable generation present 

grid integration challenges.