David J. Bents and Vincent J. Scullin

Glenn Research Center, Cleveland, Ohio

Bei-Jiann Chang, Donald W. Johnson, and Christopher P. Garcia

QSS Group, Inc., Cleveland, Ohio

Ian J. Jakupca

Analex Corporation, Brook Park, Ohio

Hydrogen-Oxygen PEM Regenerative Fuel

Cell Development at the NASA Glenn

Research Center

NASA/TM—2005-214032

December 2005
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David J. Bents and Vincent J. Scullin

Glenn Research Center, Cleveland, Ohio

Bei-Jiann Chang, Donald W. Johnson, and Christopher P. Garcia

QSS Group, Inc., Cleveland, Ohio

Ian J. Jakupca

Analex Corporation, Brook Park, Ohio

Hydrogen-Oxygen PEM Regenerative Fuel

Cell Development at the NASA Glenn

Research Center

NASA/TM—2005-214032

December 2005

National Aeronautics and

Space Administration

Glenn Research Center

Prepared for the

2005 Fuel Cell Seminar

cosponsored by Ansaldo Fuel Cells, Ballard Power Systems, Inc., Ohio Means Business,

Hydrogen and Fuel Cell Letter, Acta, Engelhard Corporation, Entegris, Inc., W.L. Gore

and Associates, Inc., Umicore Autocat USA, Inc., Nextech Materials, Columbian Chemicals

Company, Sud-Chemie, Tanaka Precious Metals Group, Siemens, Poly Fuel,

and U.S. Fuel Cell Council

Palm Springs, California, November 14–18, 2005
Available from

NASA Center for Aerospace Information

7121 Standard Drive

Hanover, MD 21076

National Technical Information Service

5285 Port Royal Road

Springfield, VA 22100

Available electronically at http://gltrs.grc.nasa.gov

This work was sponsored by the Low Emissions Alternative

Power Project of the Vehicle Systems Program at the

NASA Glenn Research Center.
NASA/TM—2005-214032 1 

Hydrogen-Oxygen PEM Regenerative Fuel Cell 

Development at the NASA Glenn Research Center 

David J. Bents and Vincent J. Scullin 

National Aeronautics and Space Administration 

Glenn Research Center 

Cleveland, Ohio 44135 

Bei-Jiann Chang, Donald W. Johnson, and Christopher P. Garcia 

QSS Group, Inc. 

Cleveland, Ohio 44135 

Ian J. Jakupca 

Analex Corporation 

Brook Park, Ohio 44142 

Abstract 

The closed-cycle hydrogen-oxygen PEM regenerative fuel cell (RFC) at the NASA Glenn Research 

Center (NASA Glenn) has successfully demonstrated closed cycle operation at rated power for multiple 

charge-discharge cycles. During charge cycle the RFC has absorbed input electrical power simulating a 

solar day cycle ranging from zero to 15 kWe peak, and delivered steady 5 kWe output power for periods 

exceeding 8 hr. Orderly transitions from charge to discharge mode, and return to charging after full 

discharge, have been accomplished without incident. Continuing test operations focus on: 

 (1) Increasing the number of contiguous uninterrupted charge discharge cycles 

 (2) Increasing the performance envelope boundaries 

 (3) Operating the RFC as an energy storage device on a regular basis 

 (4) Gaining operational experience leading to development of fully automated operation 

 (5) Developing instrumentation and in situ fluid sampling strategies to monitor health and anticipate 

breakdowns 

Introduction 

The RFC is beginning to demonstrate its potential as an energy storage device for aerospace solar 

power systems such as solar electric aircraft, lunar and planetary surface installations; any airless 

environment where minimum system weight is critical. 

The closed-cycle hydrogen-oxygen PEM regenerative fuel cell (RFC) at the NASA Glenn Research 

Center (Refs. 1 and 2) has successfully demonstrated closed cycle operation at rated power for multiple 

charge-discharge cycles. During charge cycles the RFC absorbed input electrical power simulating a solar 

day cycle ranging from zero to 15 kWe peak. During discharge cycles it delivered steady 4.5 to 4.8 kWe 

output power for periods exceeding 8 hr. Orderly transitions from charge to discharge mode, and return to 

charging after full discharge, were accomplished without incident. Continuing test operations focus on: 

(1) Increasing the number of contiguous uninterrupted charge discharge cycles 

(2) Increasing the performance envelope boundaries 

(3) Operating the RFC as an energy storage device on a regular basis 
NASA/TM—2005-214032 2 

(4) Gaining operational experience leading to development of fully automated operation 

(5) Developing instrumentation and in situ fluid sampling strategies to monitor health and anticipate 

breakdowns 

Table 1 presents a summary of test experience from August 2004 (date of last Fuel Cell Seminar 

publication) to the end of July 2005. In this table, “Power Absorbed” is the range of power levels 

sustained by the electrolyser in charging mode, and “Power Delivered” is the range of output powers 

delivered by the fuel cell stack and ancillaries during discharge mode. In the charge/discharge cycle tests, 

the electrolyser was normally driven by a power profile that approximates electrical output of a flat plate 

solar collector (hence the zero to 15 kWe peak), while the fuel cell was operated to deliver the maximum 

output power that could be sustained. The “longest elapsed run time” is defined as the longest elapsed 

time period during these tests that the RFC operated as an energy storage system uninterrupted for any 

reason other than orderly startup, shutdown or transitions between modes. For example, the test run of 

March 9–29, 2005, shown in Figure 1, reports a longest elapsed run time of 70 hr. This run contained two 

complete charge/discharge cycles which were carried out over a two week period, where electrolysis was 

accomplished in segments using a 4.5 kWe short stack. The segments were not contiguous but interrupted 

by normal (end of working day) shutdowns. The system however, was capable of resuming operation at 

any time during the shutdown period, hence the accumulation of elapsed hours from one segment to the 

next (elapsed hour accumulations ended when a test segment got curtailed). 

TABLE 1.—NASA CLOSED CYCLE RFC TESTING SUMMARY AUGUST 2004 TO JULY 2005

Computer SW platform

failure 10 hr (FC stack

not used)

zero to

15 kWe

Multiple Chge/Dischge

cycles + transitions

Dec 16 - 17,

2004

Successful outcome 149 hr 4.5 - 4.8

kWe

zero to

15 kWe

Multiple Chge/Dischge

cycles + transitions

June 21 - July

1, 2005

FC stack cell flooding 7 hr zero to 4.5 kWe

15 kWe

Multiple Chge/Dischge

cycles + transitions

May 17-20,

2005

EZ stack failure (bad cell) 4 hr Multiple Chge/Dischge 6 kWe 3.2 kWe

cycles + transitions

May 2 - 5, 2005

Recirculation pump failures 70 hr Charge/Discharge 4.5 kWe 4.8 kWe

cycles + transitions

Mar 9 - 29,

2005

Successful Outcome 8 hr 2.5 -

4.5 kWe

3.2 - 4.5

kWe

Safety Improvements

new software checkout

Feb 14 -

Mar18, 2005

FC stack crossover 9 hr 4.5 - 4.8

kWe

zero to

15 kWe

Charge/Discharge

cycles, new EZ stack

Dec 8 - 10,

 2004

Successful outcome 10 hr (FC stack

not used)

zero to

6 kWe

New EZ short stack

performance tests

Nov 30 - Dec 1,

 2004

Cell flooding, vent/purge

req’d 2.5 hr 3.0 - 4.5

kWe

(EZ stack

not used)

Non-venting Cell

flooding prevention

Oct 22 - 25,

2004

Pressure spike causes EZ

stack failure 21 hr 4.5 - 4.8

kWe

2.1 - 11

kWe

Charge/Discharge

cycles + transitions

Aug 3 - 4, 2004

Test Curtailed

By:

Longest

elapsed

run

Power

delivered

Power

absorbed

Test

Objectives

Date(s) of Test
NASA/TM—2005-214032 3 

Figure 1.—NASA closed cycle RFC testing March 9–29, 2005. 

Although the majority of the tests logged in Table 1 were curtailed by failures, the failures spawned 

hardware and software improvements which eventually rendered the system capable of longer operations 

at rated power. These improvements included: (1) methods to isolate and remove inert contaminants from 

the stack, thereby reducing to zero the amount of venting/purging that is required; (2) balanced void 

volumes within the recirculation loops, and carefully timed valves and orifices to minimize differential 

pressure swings due to mode transitions and reactant recombination; (3) “Fuzzy Logic” automated control 

for rapid power transitions while maintaining equilibrium within the fuel cell stack and recirculation 

loops (faster ramp up than a human operator); and (4) control strategies to identify and respond to 

individual cell dropoffs in an appropriate and timely manner (i.e., distinguish between flooding, dryout or 

inert contamination) leading to development of fully automatic controls. 

A significant development milestone was achieved during the test series June 24 to July 1 when the 

RFC was operated for seven complete charge/discharge cycles without failure. Five of these cycles were 

run continuously over an uninterrupted 120 hr period, from June 26 to July 1. These five contiguous 

back-to-back charge/discharge cycles at full power, with transitions, are shown in Figure 2. 

During charge cycles the RFC absorbed daytime solar electrical current profiles of 0 to 15 kWe 

storing the energy as pressurized hydrogen and oxygen gas. The RFC delivered back the stored energy 

during discharge as steady 4.5 to 5 kWe electrical power. Electrical energy delivered during each cycle 

ranged from 38 to 40 kW/hr. Full power was sustained during both charge and discharge modes 

throughout the duration of test demonstrating maximum system performance. Smooth transitions at the 

end of the electrolysis (charge) cycle to fuel cell (discharge) mode were repeatedly accomplished, and 

smooth transitions at the end of discharge (fuel cell) mode back to charge mode (electrolysis) were 

repeated. At the conclusion of testing the hardware remained fully capable of repeating another 

charge/discharge cycle without servicing or intervention. The RFC demonstrated fully closed cycle 

operation during the test period (hermetically sealed system, nothing goes in, nothing goes out other than 

electrical power and heat). Reactant inventory (water) losses measured at the end of the test period (seven 

full charge/discharge cycles including the five contiguous back-to-back cycles) were less than 1 percent. 

RFC Operation March 9-29. 2005

0

50

100

150

200

250

0 10 20 30 40 50 60 70 80

Elapsed Time, Hr

0

50

100

150

200

250

300

350

400

450

Pressure, psig

Electrolyzer Current

Fuel Cell Current

Hydrogen Tank

Reactant Tank Pressure, psig

Elapsed Time,hrs

 

 

 Stack Current, A

150

100

50

0

200

250

0 10 20 30 40 50 60 70 80

Electrolyser (EZ) 4.5kWe Fuel Cell (FC) 4.8kWe
NASA/TM—2005-214032 4 

RFC Reactant Versus Time 

0

100

200

300

400

500

600

700

800

900

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5

Time, days

-20

30

80

130

180

Water, lbs

H2 Tank Pressure O2 Tank Pressure Water

NASA Glenn RFC cycle test Jun 26 - July 1, 2005

-100

-50

0

50

100

150

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5

Time, days

0

20

40

60

80

100

120

140

160

180

200

220

240

260

280

300

320

340

360

380

400

420

Stack Voltage, vdc

EZ Current FC Current EZ Stack Voltage FC Stack Voltage

100

150

 50

 0

400

300

200

100

 0

 80

 40

 0

100

Pressure, psig Stack Current, A Stack vdc

 30

 80

 20

Water, lbm,

 NASA Glenn RFC cycle test Jun 26-July 1, 2005 

Elapsed Time, days

EZ FC EZ FC EZ FC EZ FC EZ FC

EZ FC EZ FC EZ FC EZ FC EZ FC

Figure 2.—NASA closed cycle RFC testing June 26 to July 1, 2005. 

Figure 2 summarizes system performance over the five days operation. In the topmost plot “Stack 

Current,” the sin2

-shaped trace represents electrolyser current applied during charge (day) cycle, which is 

followed by a square wave shaped trace that represents fuel cell output current during the discharge 

(night) cycle, plotted over the entire five day period. The day/night cycle applied was 16/8 hr, 

respectively, roughly corresponding to local summertime day/night conditions. In the middle plot, the top 

trace is electrolyser stack voltage, while the lower trace is the fuel cell stack voltage. Note how stack 

voltages idle to open circuit then fall during recombination. The RFC system ran completely sealed closed 

cycle over the five day period (no venting no purging). The bottom plot depicts overall reactant balance 

over the five days, coincident with the power profiles. The wide amplitude traces correspond to (oxygen 

and hydrogen) reactant tank pressures, while the smaller amplitude trace corresponds to pounds of water 

remaining, as measured by the oxygen phase separator tank level. Water inventory is minimum when 

reactant tank pressures are at their peak. As hydrogen and oxygen are consumed the water level rises. 

Note how water level at the end of the five days is just about the same as it was in the beginning. Since 

the fuel cell stack was operating at maximum current during these tests, overall system round trip energy 

storage efficiency was less than 50 percent. This demonstration fulfilled NASA’s Low Emissions 

Alternative Power Aircraft Fuel Cell Power System Regenerative Fuel Cell (LEAP AFCPS RFC) Task 

FY05 milestone criteria “Demonstrate repeatable system performance over multiple (4 to 10) repeated 

contiguous charge/discharge cycles” thus confirming the RFC’s potential as an energy storage device for 

aerospace solar power systems such as solar electric aircraft, lunar and planetary surface installations; any 

airless environment where minimum system weight is critical. 
NASA/TM—2005-214032 5 

References 

1. D.J. Bents, V.J. Scullin, B.J. Chang, D.W. Johnson, and C.P. Garcia, “Hydrogen-Oxygen PEM Regenerative Fuel 

Cell Energy Storage System,” 2004 Fuel Cell Seminar, San Antonio, TX, Nov. 1–5, 2004, NASA/TM—2005-

213381. 

2. B.J. Chang, D.W. Johnson, C.P. Garcia, I.J. Jakupca, V.J. Scullin, and D.J. Bents, “Regenerative Fuel Cell Test Rig at 

Glenn Research Center,” Proc. First International Energy Conversion Engineering Conference (AIAA, ASME, IEEE), 

Portsmouth, VA, Aug. 17–21, 2003, AIAA–2003–5942, NASA/TM—2003-212375. 
This publication is available from the NASA Center for AeroSpace Information, 301–621–0390.

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E–15388

WBS–22–066–20–04

11

Hydrogen-Oxygen PEM Regenerative Fuel Cell Development

at the NASA Glenn Research Center

David J. Bents, Vincent J. Scullin, Bei-Jiann Chang, Donald W. Johnson,

Christopher P. Garcia, and Ian J. Jakupca

Fuel cells; Regenerative fuel cells; Hydrogen/oxygen

Unclassified -Unlimited

Subject Category: 44

Prepared for the 2005 Fuel Cell Seminar cosponsored by Ansaldo Fuel Cells, Ballard Power Systems, Inc., Ohio Means

Business, Hydrogen and Fuel Cell Letter, Acta, Engelhard Corporation, Entegris, Inc., W.L. Gore and Associates, Inc.,

Umicore Autocat USA, Inc., Nextech Materials, Columbian Chemicals Company, Süd-Chemie, Tanaka Precious Metals

Group, Siemens, Poly Fuel, and U.S. Fuel Cell Council, Palm Springs, California, November 14–18, 2005. David J. Bents

and Vincent J. Scullin, NASA Glenn Research Center; Bei-Jiann Chang, Donald W. Johnson, and Christopher P. Garcia,

QSS Group, Inc., 21000 Brookpark Road, Cleveland, Ohio 44135; and Ian J. Jakupca, Analex Corporation, 1100 Apollo

Drive, Brook Park, Ohio 44142. Responsible person, David J. Bents, organization code RPT, 216–433–6135.

The closed-cycle hydrogen-oxygen PEM regenerative fuel cell (RFC) at the NASA Glenn Research Center has successfully demonstrated closed cycle operation at rated power for multiple charge-discharge cycles. During charge cycle the

RFC has absorbed input electrical power simulating a solar day cycle ranging from zero to 15 kWe peak, and delivered

steady 5 kWe output power for periods exceeding 8 hr. Orderly transitions from charge to discharge mode, and return to

charging after full discharge, have been accomplished without incident. Continuing test operations focus on: (1)

Increasing the number of contiguous uninterrupted charge discharge cycles; (2) Increasing the performance envelope

boundaries; (3) Operating the RFC as an energy storage device on a regular basis; (4) Gaining operational experience

leading to development of fully automated operation; and (5) Developing instrumentation and in situ fluid sampling

strategies to monitor health and anticipate breakdowns.