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.

Hydrogen for Energy Storage Analysis 

Overview

National Hydrogen 

Association Conference 

& Expo

Darlene Steward, Todd 

Ramsden, Kevin 

Harrison

National Renewable 

Energy Laboratory

May 3-6, 2010

Long Beach, CA

NREL/PR-560-48360

This presentation does not contain any proprietary, confidential, or otherwise restricted information
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Objectives

Compare hydrogen and competing technologies for utilityscale energy storage systems.

Explore the cost and GHG emissions impacts of interaction of 

hydrogen storage and variable renewable resources

Outline

Study Framework

Preliminary Study Results

– Lifecycle cost analysis for hydrogen and competing 

technologies

– GHG emissions credit impact for a remote wind farm

NREL Wind to Hydrogen Study Perspectives

Hydrogen Energy Storage System Modeling

2
3

Scenarios for Hydrogen Energy Storage Analyses

National Renewable Energy Laboratory Innovation for Our Energy Future

Battery

Electricity

Pump/Compressor

/Turbine

Electricity

Air or Water 

Reservoir

?Is hydrogen a 

potential solution for 

utility-scale energy 

storage

Shed 

electricity

?How would using 

hydrogen for 

storage impact cost 

and emissions for 

renewable 

resources Hydrogen 

Storage

Shed 

electricity

Comparison of costs for hydrogen and competing technologies

Study of hydrogen energy storage for a specific renewable resource
4

Energy Storage Scenario for Comparison 

Study

Nominal storage volume is 300 MWh (50 MW, 6 hours)

o Electricity is produced from the storage system during 6 peak hours (1 to 7 pm) 

on weekdays

o Electricity is purchased during off-peak hours to charge the system 

Electricity source: excess wind/off-peak grid electricity 

o Assumed steady and unlimited supply during off-peak hours (18 hours on 

weekdays and 24 hours on weekends)

o Assumed fixed purchase price of off-peak/renewable electricity

Source: HOMER model output

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5

Levelized Cost of Hydrogen and Competing Technologies

Hydrogen is competitive with batteries and could be competitive with CAES

and pumped hydro in locations that are not favorable for these technologies.

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Round-Trip Efficiency and Electricity Price Sensitivity

• Electricity price sensitivity

o Low-capital-cost, high-efficiency pumped hydro system is sensitive to electricity price

o High-capital-cost NiCd system is insensitive to electricity price

o For other storage systems, sensitivity to electricity price is roughly inversely 

proportional to round-trip efficiency 

NiCd battery

CAES

FC aboveground

Pumped hydro

FC/geologic

H2 Comb turbine

NaS battery

VR battery

0.00%

2.00%

4.00%

6.00%

8.00%

10.00%

12.00%

14.00%

0.0% 10.0% 20.0% 30.0% 40.0% 50.0% 60.0% 70.0% 80.0% 90.0%

Storage System Round-Trip Efficiency

Electricity Price Sensitivity (% change in 

LCE/c)

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Energy Storage & Greenhouse Gases

Source: Denholm, Paul. (October 2006). “Creating Baseload Wind Power Systems Using Advanced Compressed Air Energy Storage Concepts.” 

Poster presented at the University of Colorado Energy Initiative/NREL Symposium. http://www.nrel.gov/docs/fy07osti/40674.pdf

+ -

Additional energy from the 

windfarm can be captured for 

later use

Efficiency losses incurred by 

routing wind energy through the 

storage system reduce the 

greenhouse gas benefit of wind
8

Wind Farm Location

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The NREL Western Wind Data Set 

was used to identify a realistic 

remote wind farm location
9

Study Framework - Add Hydrogen Storage to a Base Case 

Without Storage

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750 

MW

Hydrogen 

Storage

400 MT

Curtailed 

electricity 

2%

Electricity to grid (storage + 

direct)

87% of total wind farm output

Storage Constrained Case

Electricity to storage

16% of total wind farm output

Electricity from storage

5% of total output

500

MW

Hydrogen 

Storage

2,600 MT

Curtailed 

electricity 

12%

(storage + direct)

68% of total wind farm output

Transmission Constrained Case

Electricity to storage

27% of total wind farm output

Electricity from storage

7% of total output

Curtailed 

electricity 

17%

Electricity 

to grid

83%

750 

MW

Base Case (without storage)

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Analysis of the base case 

provides LCOE and avoided 

emissions for comparison
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Primary Study Assumptions

Major Assumptions

o Electrolyzer and PEM fuel cell 

performance and cost values 

derived from mid-cost case of 

lifecycle cost analysis

o Hydrogen storage in geologic 

storage

o The storage system is located at 

the wind farm & all electricity 

charged to the storage system is 

derived from the wind farm

o A dedicated transmission line 

carries electricity from the wind 

farm/storage system to the grid 

near demand centers.

o Power from the wind farm will be 

curtailed (shed) if:

o It exceeds the maximum 

charging rate of the storage 

system + maximum capacity 

of the transmission line

o The storage system is full

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Hydrogen 

Storage

Shed 

electricity

10
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Wind Farm and Hydrogen Storage for Storage 

Constrained Case - Hydrogen to Storage

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0

5,000

10,000

15,000

20,000

25,000

30,000

1/2/062/2/063/2/064/2/065/2/066/2/067/2/068/2/069/2/06

10/2/0611/2/0612/2/06

Energy (MWh/day)

Electricity From Wind (kW)

Hydrogen to Storage (kW)
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Wind Farm and Hydrogen Storage for Storage 

Constrained Case - Hydrogen from Storage

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0

5,000

10,000

15,000

20,000

25,000

30,000

1/2/062/2/063/2/064/2/065/2/066/2/067/2/068/2/069/2/06

10/2/0611/2/0612/2/06

Energy (MWh/day)

Electricity From

Wind (kW)

Hydrogen from

Storage (kW)
13

Summary of Preliminary Results

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Storage reduces the amount of electricity that must be curtailed and 

reduces the LCOE

Base Case Storage 

Constrained

Transmission 

Constrained

Electricity Direct from Wind 

Farm to Transmission Line

82.7 82.7 60.8

Electricity from Storage N/A 4.5 7.4

Electricity Shed 17.3 1.9 11.7

Net Electricity to 

Transmission Line

82.7 87.2 68.2

Transmission Line Utilization 56.0 59.0 69.0

Without cost of carbon 13 10 12

@ cost of carbon $50/MT 

CO2eq

9 6 8

@ cost of carbon $100/MT 

CO2eq

5 2 4

 (% of Total Wind Farm Output)

 (% of Total Transmission Line Capacity)

 (LCOE ¢/kWh)

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Effect of a Cost of Carbon on the Competitiveness of Wind 

& Hydrogen Storage System

Cost comparison for Chicago Grid Electricity v Wind Electricity for Various Storage Configurations

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0

2

4

6

8

10

12

14

16

0 50 100

Cost of Electricity c/kWh

Cost of Carbon $2008/MT CO2eq

Chicago grid 

Base case wind

Transmission 

constrained wind

Storage constrained 

wind

Credit for avoided emissions reduces LCOE for wind electricity below 

grid price

14
15

NREL Wind to Hydrogen Project - 10kW Wind 

Turbine Powered Electrolysis

• Initial tests with third generation power electronics, wind speed 

measurement and control algorithm indicate further improved energy 

capture of wind electricity into hydrogen production

0

2000

4000

6000

8000

10000

12000

14000

0 5 10 15 20 25 30 35 40

Wind Speed (MPH)

Power (Watts)

Gen 2 – DC Power Gen 1 – DC Power

Planned increased 

energy capture from 

Gen 2 to Gen 3

Increased energy 

capture from Gen 1 

to Gen 2

Available 

wind power = Preliminary results 

showing increased energy 

capture with new TSR 

algorithm. Algorithm is 

currently being tuned for 

stability.
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Cost Analysis

• Cost analysis performed based 

on NREL’s power electronics 

optimization and testing and 

on our electrolyzer cost 

analysis study

• Large centralized system 

capable of 50,000 kg per day 

production 

• Optimized power conversion 

system due to a closer 

coupling of the wind turbine to 

the electrolyzer stack can 

reduce the total cost of 

hydrogen by 7%. 

Capital Component (uninstalled) Baseline 

System

Optimized 

System

1.5 MW Wind Turbine

Rotor $248,000 $248,000

Drive Train $1,280,000 $1,180,000

including power 

electronics $100,000 $0

Control System $10,000 $10,000

Tower $184,000 $184,000

Balance of Station $262,000 $262,000

2.33 MW Electrolyzer $1,570,000 $1,350,000

including power 

electronics $220,000 $0

New Power Electronics Interface $0 $70,000

Resulting Hydrogen Cost ($/kg) $6.25 $5.83
17

Key Findings from Wind2H2 RD&D

System Efficiency (HHV): At rated stack current...

– The PEM electrolyzer system efficiency of 57% 

– The alkaline system had a system efficiency of 41%

• H2 production about 20% lower than the manufacturer’s rated flow rate

• 50% system efficiency would be realized if rated flow were achieved

Cost Reductions from Power Electronics Optimization:

– Analysis showed a potential 7% reduction in cost per kg of 

hydrogen based on capital cost improvement

• Projected cost of hydrogen falling to $5.83/kg from a baseline of 

$6.25/kg

Energy Transfer Improvements: PV configuration testing compared 

direct-connection to the electrolyzer stack with a connection through 

power electronics

– The MPPT power electronics system captured between 10% and 

20% more energy than the direct-connect configuration
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Thank You

Questions?
19

Thank You

National Renewable Energy Laboratory Innovation for Our Energy Future

Darlene Steward

Darlene.steward@nrel.gov