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

Scenario Development and Analysis of 

Hydrogen as a Large-Scale Energy Storage 

Medium 

RMEL Meeting

Darlene M. Steward 

National Renewable 

Energy Laboratory

darlene.steward@nrel.gov

Denver, CO

June 10, 2009

NREL/PR-560-45873
2

Introduction 

NREL Project Team

– Todd Ramsden 

– Darlene Steward

– Genevieve Saur

– Mike Penev

National Renewable Energy Laboratory Innovation for Our Energy Future
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Objective:

Evaluate the economic viability of the use of hydrogen for medium- to large-scale energy storage applications in comparison with 

other electricity storage technologies

Strategy:

Develop potentially viable hydrogen production and storage 

scenarios

Perform a lifecycle economic analysis to determine the levelized 

cost of delivering energy for the hydrogen scenarios

Benchmark against competing technologies on an “apples to 

apples” basis

– Batteries

– Pumped hydro 

– Compressed Air Energy Storage

Is Hydrogen a Viable Energy Storage Medium?
National Renewable Energy Laboratory 4 Innovation for Our Energy Future

Develop potentially viable hydrogen production 

and storage scenarios

Perform a lifecycle economic analysis to 

determine the levelized cost of delivering 

energy for the hydrogen scenarios

Benchmark against competing technologies on 

an “apples to apples” basis

– Batteries

– Pumped hydro 

– Compressed Air Energy Storage

Benchmarking Study: “Apples to Apples” Analysis
National Renewable Energy Laboratory 5 Innovation for Our Energy Future

Hydrogen for Bulk Energy Storage—Simple Scenario

Energy Arbitrage—Grid/renewable electricity is electrolyzed to produce 

hydrogen when demand is low and/or renewables must be purchased. 

Hydrogen is stored for use in a dispatchable fuel cell to provide power 

during periods of peak demand.

– Primary figure of merit is levelized cost of delivered electricity

– Storage system may also meet requirements for spinning reserve and other 

services, but no value is assigned to these services

Electricity

Hydrogen 

Storage

Electrolyzer

Fuel Cell
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Study Framework—System Configuration

50MW for 6 peak hours each weekday (300 MWh/day)

Two basic storage system configurations, both using an 

electrolyzer system to produce hydrogen and a fuel cell 

system to produce electricity:

– Case 1: Steel tank storage (above ground)

– Case 2: Geologic storage

3 timeframes/cost values considered:

– Near-term: Up to 2010 (current or high cost)

– Mid-term: 2010–2020

– Long-term: 2020–2030 (future assumed low cost)

Long-term case meant to represent best-case scenario 

for hydrogen-based energy storage using stretch goals 

based on fully mature, optimized hydrogen technologies

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Study Framework—Facility Life Economic Analysis

Financial Assumptions

– 40-year plant life (Some equipment will be replaced at more 

frequent intervals.)

– 10% after-tax internal rate of return

– 100% equity financing

Cost Assumptions

– Electricity is purchased from the grid during off-peak hours at 

3.8¢/kWh (lower-bound cost) or 6¢/kWh (upper-bound case)

– Natural gas is purchased at $5/mmBtu for the CAES system

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Study Framework— Facility Life Economic Analysis

Facility Lifecycle Economic Analysis Using the HOMER 

Model

– NREL distributed generation economic model 

(https://analysis.nrel.gov/homer)

– Least cost system optimization based on subsystem 

component costs and resource and load characteristics

– Model output is levelized cost (¢/kWh) of output electricity 

from the system

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Develop potentially viable hydrogen production 

and storage scenarios

Perform a facility lifecycle economic analysis to 

determine the levelized cost of delivering 

energy for the hydrogen scenarios

Benchmark against competing technologies on 

an “apples to apples” basis

– Batteries

– Pumped hydro 

– Compressed Air Energy Storage

Benchmarking Study: “Apples to Apples” Analysis
10

Fuel Cell Subsystem

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Solid Oxide Fuel Cell (SOFC) Polymer Electrolyte Fuel Cell 

(PEM) (a.k.a., Proton Exchange 

Membrane Fuel Cell)

Sources: http://en.wikipedia.org/wiki/Proton_exchange_membrane_fuel_cell

http://en.wikipedia.org/wiki/Solid_oxide_fuel_cell
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Fuel Cell Subsystem

Current Timeframe Value Future Timeframe Value

System 

component SOFC PEM SOFC PEM

Fuel Cell System 

installed capital 

cost

$900/kW $3,000/kW $390/kW $400/kW

Stack 

replacement 

frequency/cost 

10 years/30% 

of initial capital 

cost

13 years /30% of 

initial capital cost

10 years/30%

of initial capital 

cost

26 years /30% 

of initial capital 

cost

O&M costs $27/kW-yr. $50/kW-yr. $12/kW-yr. $20/kW-yr.

Fuel cell life 10 yr. (15,660 h 

operation)

13 yr. (20,000 h 

operation)

10 yr. (15,660 h 

operation)

26 yr. (40,000 h 

operation)

Fuel cell system 

efficiency 60% 42% 70% 53%

Power converter 

efficiency N/A 90% N/A 90%

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SOFC—Solid Oxide Fuel Cell

PEM—Polymer Electrolyte Membrane Fuel Cell
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Electrolyzer and Storage Subsystems

Current Timeframe 

Value Future Timeframe Value

Electrolyzer

System Efficiency 73% (HHV) 87% (HHV)

Capital Cost $675/kW $300/kW

Steel Tank Storage

Capital Cost (28,600 kg 

nominal storage 

example*, Hydrogen 

compressed to 2500 

psi)

$30.7M (includes 

compressor)

$12.3M (includes 

compressor)

Geologic Storage

Capital Cost (28,600 kg 

nominal storage, 

Hydrogen compressed 

to 1800 psi)

$7.8M (includes 

compressor)

$5.8M (includes 

compressor)

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*Storage costs shown are for 28,600 kg example. Modeled storage volume and costs are 

determined for each case and timeframe.
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Cost of Energy for PEM Fuel Cell vs. Solid Oxide Fuel Cell

Chart represents 

“bounding case” 

information

-High Cost Bounding 

Case: Current timeframe, 

aboveground storage

- Low Cost Bounding 

Case: Future timeframe, 

geologic storage

Current timeframe

Future timeframe
National Renewable Energy Laboratory 14 Innovation for Our Energy Future

Develop potentially viable hydrogen production 

and storage scenarios

Perform a lifecycle economic analysis to 

determine the levelized cost of delivering 

energy for the hydrogen scenarios

Benchmark against competing technologies on 

an “apples to apples” basis

– Batteries

– Pumped hydro 

– Compressed Air Energy Storage

Benchmarking Study: “Apples to Apples” Analysis
National Renewable Energy Laboratory 15 Innovation for Our Energy Future

Benchmarking Analysis—Evaluate all Technologies 

for the Same Scenario

Analysis of competing technologies within the same study 

framework as the original analysis and bounding cases

• Current timeframe—High cost due to technology immaturity 

and few installations

– Actual installations and costs when available

• Future timeframe—Lower cost due to technology maturity and 

more installations

– Best available information on projected costs and DOE 

targets

Competing Technologies

– Batteries

• Nickel Cadmium

• Sodium Sulfur

• Vanadium Redox

– Pumped Hydro

– Compressed Air Energy Storage
National Renewable Energy Laboratory 16 Innovation for Our Energy Future

Develop potentially viable hydrogen production 

and storage scenarios

Perform a lifecycle economic analysis to 

determine the levelized cost of delivering 

energy for the hydrogen scenarios

Benchmark against competing technologies on 

an “apples to apples” basis

– Batteries

– Pumped hydro 

– Compressed Air Energy Storage

Benchmarking Study: “Apples to Apples” Analysis
National Renewable Energy Laboratory 17 Innovation for Our Energy Future

Benchmarking Analysis—Batteries

Three Battery Technologies

Nickel Cadmium 

– Demonstrated utility-scale project outside Fairbanks Alaska: 13 MWh (26 

MW at 30 min.) 

Sodium Sulfur

– NGK Insulators Ltd. of Japan is currently the only supplier.

– Tokyo Electric Power Company (TEPCO) has developed several utilityscale projects with NGK. Demonstration projects range from 500 kW to 6 

MW in scale including two 48-MWh plants.

Vanadium Redox Flow Batteries

– Currently, the major suppliers of Vanadium Redox batteries are VRB Power 

Systems, Inc. of Canada and Sumitomo Electric Industries (SEI) of Japan. 

– Demonstrated installations range in size from 3 MW for 1.5 seconds of 

storage to 500 kW for up to 10 hours of storage. 
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Battery Charge Characteristics—NiCd Example
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The cost of NiCd batteries is high in comparison to sodium sulfur and Vanadium 

Redox batteries due to relatively high capacity ($/kWh) costs.

Battery System Cost of Output Energy
National Renewable Energy Laboratory 20 Innovation for Our Energy Future

Develop potentially viable hydrogen production 

and storage scenarios

Perform a lifecycle economic analysis to 

determine the levelized cost of delivering 

energy for the hydrogen scenarios

Benchmark against competing technologies on 

an “apples to apples” basis

– Batteries

– Pumped hydro 

– Compressed Air Energy Storage

Benchmarking Study: “Apples to Apples” Analysis
National Renewable Energy Laboratory 21 Innovation for Our Energy Future

Benchmarking Analysis—Pumped Hydro and CAES

Pumped Hydro

The first plant built in the United States in 1928–29 featured 

two 3-MW reversible turbines. 

Today, pumped hydro capacity in the United States is about 

19,000 MW. 

Compressed Air Energy Storage

There are two major CAES installations in Huntorf, Germany 

(built in the 1970s) and in McIntosh, Alabama (built in the 

1990s). 

Plants, built and proposed, range in size from 110 MW to 

2700 MW.
National Renewable Energy Laboratory 22 Innovation for Our Energy Future

Source: Nakhamkin, M., and M. Chiruvolu, Available Compressed Air 

Energy Storage (CAES) Concepts.

Schematic for Alabama McIntosh 110-MW CAES Plant
National Renewable Energy Laboratory 23 Innovation for Our Energy Future

Benchmarking Analysis—Pumped Hydro and CAES

Both technologies are low cost relative to hydrogen fuel cells or batteries.
National Renewable Energy Laboratory 24 Innovation for Our Energy Future

Benchmarking Cost Analysis Results

Hydrogen could be competitive with alternative technologies for the bulk 

electricity storage (50 MW, 6 hours) scenario analyzed.

– As fuel cell technology matures, electricity could be produced from 

geologically stored hydrogen for under 20¢/kWh.

– Because of its high energy density, aboveground storage of hydrogen could 

be competitive in locations where CAES and pumped hydro are not 

feasible.
National Renewable Energy Laboratory 25 Innovation for Our Energy Future

Benchmarking—Other Benefits and Drawbacks of Hydrogen Energy Storage 

Relative to Alternatives

System Operation

Benefits Drawbacks

Modular (can size the electrolyzer 

separately from FC to produce extra 

hydrogen)

Low electrolysis/FC round trip (AC to AC) 

efficiency (50–55%)

Even lower round-trip efficiency when 

hydrogen is used in a combustion turbine 

(<40%)

Very high energy density for compressed 

hydrogen (>100 times the energy density for 

compressed air at 120 bar ∆P, CC GT)

Hydrogen storage in geologic formations 

other than salt caverns may not be feasible

System can be fully discharged at all current 

levels

Electrolyzers and fuel cells require cooling

Cost

Benefits Drawbacks

Research has potential to drive down costs Use of precious metal catalysts for lowtemperature fuel cells

Currently high cost relative to competing 

technologies (>$1,000/kW)

Source: Crotogino and Huebner, Energy Storage in Salt Caverns / Developments and Concrete Projects for Adiabatic Compressed Air and for Hydrogen 

Storage, SMRI Spring 2008 Technical Conference, Portugal, April 2008.
National Renewable Energy Laboratory 26 Innovation for Our Energy Future

Benefits and Drawbacks of Hydrogen Energy Storage

Environmental

Benefits Drawbacks

Catalyst can be reclaimed at end of life Environmental impacts of mining and 

manufacturing of catalyst

Low round-trip efficiency increases 

emissions for conventional electricity 

and reduces replacement by 

renewables

Source: Denholm, Paul, and Gerald L. Kulcinski, Life cycle energy requirements and greenhouse gas emissions from large scale energy storage systems, Energy 

Conversion and Management, 45 (2004) 2153-2172. 
National Renewable Energy Laboratory 27 Innovation for Our Energy Future

Benefits and Drawbacks of Battery Energy Storage

System Operation

Benefits Drawbacks

Modular Battery voltage to current relationship 

limits the amount of energy that can be 

extracted, especially at high current

Mid range to high round trip efficiency 

(65–75%)

Cost

Benefits Drawbacks

Sodium sulfur and Vanadium Redox 

battery system cost

Nickel cadmium battery system cost

High round-trip efficiency reduces 

arbitrage scenario costs

Environmental

Benefits Drawbacks

Toxic and hazardous materials

Source: EPRI-DOE Handbook of Energy Storage for Transmission and Distribution Applications, 2003, EPRI, Palo Alto, CA and the U.S. Department of Energy, 

Washington, DC.
National Renewable Energy Laboratory 28 Innovation for Our Energy Future

Benefits and Drawbacks of Pumped Hydro Energy Storage

System Operation

Benefits Drawbacks

Well established and simple technology System requires large reservoir of water (or 

suitable location for reservoir)

High round-trip efficiency (70–80%) System requires mountainous terrain

Extremely low energy density (0.7 kWh/m3)

Cost

Benefits Drawbacks

Inexpensive to build and operate

Environmental

Benefits Drawbacks

No toxic or hazardous materials Large water losses due to evaporation, 

especially in dry climates

Habitat loss due to reservoir flooding

Stream flow and fish migration disruption

Source: Denholm, Paul, and Gerald L. Kulcinski, Life cycle energy requirements and greenhouse gas emissions from large scale energy storage systems, Energy Conversion 

and Management, 45 (2004) 2153-2172. 
National Renewable Energy Laboratory 29 Innovation for Our Energy Future

Benefits and Drawbacks of Compressed Air Energy Storage

System Operation

Benefits Drawbacks

Proposed advanced designs store heat from 

compression giving theoretical efficiency of 

70%—comparable to pumped hydro

Low round-trip efficiency (54%) with waste 

heat from combustion used to heat 

expanding air—42% without

Very low storage energy density (2.4 

kWh/m3)

Must be located near suitable geologic 

caverns

Cost

Benefits Drawbacks

Low cost

Environmental

Benefits Drawbacks

Approximately 1/3 of output energy is 

derived from natural gas feed to combustion 

turbines resulting in additional GHG 

emissions

Source: Crotogino and Huebner, Energy Storage in Salt Caverns / Developments and Concrete Projects for Adiabatic Compressed Air and for Hydrogen Storage, SMRI Spring 

2008 Technical Conference, Portugal, April 2008.
National Renewable Energy Laboratory 30 Innovation for Our Energy Future

Conclusions

Hydrogen has several important advantages over competing 

technologies, including:

– Very high storage energy density (170 kWh/m3 vs. 2.4 for CAES 

and 0.7 for pumped hydro)

• Allows for potential economic viability of above-ground storage

– Relatively low environmental impact in comparison with other 

technologies

The major disadvantage of hydrogen energy storage is cost. 

– Research and deployment of electrolyzers and fuel cells may 

reduce cost significantly.
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Thank You

Questions?