Characterizing Electrolyzer Pe

for Use in 

Wind Energy Applicati

Kevin W. Harrison

Benjamin Kroposki

Christopher Pink

National Renewable Energy La

Presented at the American Wind Energy Association's (AWEA) WINDPOWER Annual Coin Pittsburgh, Pennsylvania, June 4-7, 2006.NREL/PR-560-40100
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Presentation Outlin

• Background• Characterization, Testing and • Economic Analysis• Large-scale R&D 
Wind and Solar Energy P

The “Solar and Wind Technologies for Hydrogen Productito Congress as required by Section 812 of the 2005 EnerThe report shows that wind and solar energy sources for present in many parts of the countryThe report is available at www.hydrogen.energy.gov/cong
Definition: 

A Gallon of Gasoline 

Kilogram of Hydrog

• Gasoline 

9108,000 – 123,500 BTU/gal

• Hydrogen

9116,000 BTU/kg

• 1 kilogram of hydrogen ≈ 1 gallon 

• One caveat, if fuel cells are twice 

as gasoline internal combustion eonly half the amount of hydrogen needed

– Twice the mileage with hydrogen 
How to produce hydroge

Electrolysis.

DC electricity 

from renewable 

sources

H

H

O

H

H

O

Focus of this research is on renew

production because it is the only wa

produce the gas without emis
Electricity Costs are 

Hydrogen costs via electrolysis with electricity co

$0.00$1.00$2.00$3.00$4.00$5.00$6.00$7.00$8.00

0.000 0.010 0.020 0.030 0.040 0.050 0.060 0.070 0.080 

Electricity costs $/kWh

H2 cost $/kg

Commercial System Efficiencies (54-67 kWh/kg)Ideal System (HHV of Hydrogen 39 kWh/kg)

`

DOE: $2.00 - 3.00 kg -1 delivered, untaxed, 2005$ 
Technology Character

• Alkaline

– Cheaper catalyst (Ni v. Pt)– Low current density ( 

↑ efficiency)

– Largest system < 10

3 $ kW-1

• PEM

– Pure water input requires H

20 vapor 

– Higher differential output pressure– Solid (not corrosive) electrolyte– 10

3 – 104 $ kW-1

• Solid Oxide 

– R&D
Characterization Testing and 

Development

• Completed 

characterizPEM electpower elecdesign

• Completed 

simulated using powe

• Completed 

5 kW PV a

• Continued 

10 kW win
Electrolyzer Requireme

• Ideally ~1.2 V cell-1

Æ f (I,T,P

• Practical cells ~ 2.0 – 2.5 V c

• N series-connected cells 

↑

V

ActualStack Potential

Stack Ideal Potential Stack Efficiency

=

Hydrogen 

Produce

An

Power Supply Efficiency Input Stack Energy (kWh)

kg

kWh HHV

 Efficiency System

⎟ +⎠⎞ ⎜

⎝⎛

⎠⎞ ⎜

⎝⎛

=
Modified VCS-10

+

40VDC

Step Down

Transformer

10 kW Bergey 

Excel

40 VDC Batt

Half-bridge 

Controlled SCR 

Bridge

Completed Power Electronic Interface Mo

System Integration and Component 
0

20406080

100120140160180

01234

Time (second)

Stack Current (A)Stack Voltage (V)

Variable Input Pow

• Programmable power supplies to vary input power to stack

• Wstack DC/
Monitor Performan

145150155160165170

42 122 202 2

Pressure (psig)

0

20406080

100120140160

0.0

20.8

41.7

66.0

86.8

107.6

128.7

149.6

170.4

196.7

217.5

Time (minutes)

Stack Current (Amps)

Current from external power 

supplies to stack

Hydrogen flow rate (scfm)

• Stack and system energy• Hydrogen pressure, flow and quality• Water temp., flow and quality

• ImpaTHD)
Modeling

3032343638404244464850

0 20 40 60 80 100 120 140 160

Stack Current (Amp)

Stack Voltage (Volt)

Tavg = 9.0 °CTavg = 14.8 °CTavg = 24.1 °CTavg = 32.4 °C

Cathode pressure range 86.6 - 103.4 psig

0

102030405060708090

0 20 40 60 

Cu

T Sicia

• IV data aelectrochemstack chara
Analysis of Performa

0

102030405060

0% 25% 50% 75% 

% of Full Stack Current

System Efficiency (%)

• System efficiency of PEM system at various levels of current and temperature
Economic Analysis Pu

Hydrogen Production

– How much does it cost to produc

for use as a transportation fuel?

– System uses wind electricity to p

hydrogen for transportation purp

– Results in $/kg of hydrogen

– Whether wind at site can compet

distributed H

2 production
Electrolyzer

- Produces hydrogen whenever 

the turbine produces electricity, except during peak electricity demand hours Vestas V82 turbine • 1.65 MW

Evaluated two wind sites• Minnesota WROC Site• Gobblers’ Knob

Case 1: Hydrogen Produ

at the Wind Site

Electricity Hydrogen
Hydrogen F

Case 2: Distributed Hydrogen 

Using Xcel Aggregate Wind 

Wind Sites

Grid

Lamar

Peetz

Ponnequin

Xcel Aggregate Wind

Electricity

Electrolyzer

Electricity

Signal

Must meet a filling station demand

Htr

Hyd
Model Results

• Good wind resource is a key to prod

hydrogen

– 12-16% price reduction in hydrogen pro

• Production at the wind site makes fis

cost reductions offset delivery cost

• Cost reductions and efficiency impro

be obtained by electrolyzer manufaclow price hydrogen

• If aggregate wind electricity is availa

station for $0.038/kWh, the potential hydrogen production, compression afrom wind below the DOE cost target delivered

∴Xcel Decides Go!
Project Objective

This project examines the issues with using renergy to produce hydrogen by electrolyzing 

• Characterize electrolyzer performance under va

conditions

• Design and develop shared power electronics pa

controllers to reduce cost and optimize system pidentify opportunities for system cost reduction tbreakthroughs in component integration

• Test, evaluate and optimize the renewable elect

performance for both

• Dedicated hydrogen production• Electricity/hydrogen cogeneration
Wind2H2E Wind Testing Con

H2

Compression

(F

DC BUS

DC-DC

Converters

DC-D

Conve

Northern Power 

Systems 

100 kW WT

Excess AC Power

H2 Output

H2 Storage 

3,500 PSI
Wind2H2E Grid Testing Con

Proton Energy 

HOGEN 40RE

H2

Compression

(F

AC Power

H2 Output

Teledyne 

HM-100

H2 Storage 

3,500 PSI

Utility Grid
Acknowledgements 

References

• Thanks to:

– Johanna Levene, Ben Kroposki, Bill Kramer an– Peter Lilienthal and Tom Lambert for HOMER 

enhancements

– H2A team for hydrogen equipment assumption– Team of Xcel, NREL, EPRI and John Cornish– Specifically Frank Novachek and Vicki McCarl 

their invaluable assistance and support during 

• References:

– www.nrel.gov/homer– WindPower paper and presentation, An Econo

Hydrogen Production from Wind

– www.hydrogen.energy.gov/h2a_analysis.html
Backup Slides
Key Common Assump

Parameter Assumption

• Costs are assumed to be $740/kW, $40

near, mid and long term

• Electrolyzer and compression efficienc

(based on 39 kWh/kg HHV) in short, m

Electrolyzer

• Uses AC power

Compressor • $600,000, $300,000 and $100,000 for 

in near, mid and long term

• Includes compressor energy requireme• Discount rate used to convert between 

annualized costs

Annual Real 

Interest Rate • Study uses 10%

Hydrogen 

Dispensing

• No hydrogen dispensing costs included

Detailed assumptions are available in Appendix A 
Key Common Assumptions 

Parameter Assumption

• Peak electricity usage is from 4-7 p.m. 

hydrogen can be produced during thos

Peak 

Electricity

• There are no peak hours during the we

can run 24 hours a day

System • Hydrogen is compressed after producti

Pressure • Storage is provided at 6500 psi

• Turbine costs are not specifically used 

cost of wind generated electricity is us

• Assumes this cost includes capital, rep

costs of the wind turbines

• Xcel Energy purchases wind generate

$0.038/kWh

Wind Turbine 

Capital and Operating Costs

Detailed assumptions are available in Appendix A 
Wind2H2E Project Feat

Feature ImportanceDirect DC feed to electrolyzer

Grid connected and isolated w

system efficiency gains & futuintegration capital cost reduct

Concurrent AC feed to electrolyzer

Permits clear comparison to dperformanc

e

Multiple commercial electrolyzers

Grid connected and isolated w

and reduced operability risk, agains 

Medium pressure range compression and storage

Reduced operability risk, reduhydrogen & improved reliabili

Hydrogen ICE generator set

H

2 or H

2/NG mixed fuel option

Initial siting at NREL controlled facility

World class R&D practices anH

2 handling practices from ex

System transportability for redeployment Utility value after R&D testing
Analysis Tool

• The HOMER® Model was developed 

allow users to optimize electric systeit easier to evaluate the many possibconfigurations

– Hydrogen added in 2004, enhanced in 

The Problem:Case 2: You are tryhydrogen load (sho- How much electrgrid provide?- Should you add mor more storage to - How much does t