Fuel Cell Powered Data Centers: In-Rack DC Generation

Li Zhao, Jack Brouwer

National Fuel Cell Research Center

University of California, Irvine

Sean James, Eric Peterson,

Fuel Cell Powered Data Centers:

In-Rack DC Generation

Motivation

• Data center energy consumption doubled from 2000 to 2006

• More than 60 billion kWh at 2006

• That consumption could double again by 2011*

• Expected to double every 5 years

• Implementation of fuel cell technologies in data centers

Motivation

571.4 kW fuel to the Power Plant 371.4 kW Generation Losses (A) Traditional Data Center

(with U.S. Grid Average Efficiency, 2011)

200 kW Generated 16 kW T&D Losses 184 kW to the Data Center 18 kW UPS PUE = 1.838 Fuel to Server Efficiency = 17.5%

338.7 kW Natural Gas to the PEMFC 50.8 kW Conversion Losses (B) PEMFC Powered Data Center 287.9 kW Hydrogen to the Fuel Cell 119.9 kW Generation Losses 7.1 kW to FC BoP PUE = 1.575 Fuel to Server Efficiency = 29.5%

3.4 kW to FC Cooling 157.5 kW to the Data Center 52.5kW to Cooling 100 kW to the Servers 5 kW to Lighting 61 kW to Cooling 5 kW Lighting 100 kW to the Servers

NG

NG

Fuel Cell – 29.5%

Grid – 17.5%

Savings:

571.4 kW fuel to the Power Plant 371.4 kW Generation Losses (A) Traditional Data Center

(with U.S. Grid Average Efficiency, 2011)

200 kW Generated 16 kW T&D Losses 184 kW to the Data Center 18 kW UPS PUE = 1.838 Fuel to Server Efficiency = 17.5%

338.7 kW Natural Gas to the PEMFC 50.8 kW Conversion Losses (B) PEMFC Powered Data Center 287.9 kW Hydrogen to the Fuel Cell 119.9 kW Generation Losses 7.1 kW to FC BoP PUE = 1.575 3.4 kW to FC Cooling 157.5 kW to the Data Center 52.5kW to Cooling 100 kW to the Servers 5 kW to Lighting 61 kW to Cooling 5 kW Lighting 100 kW to the Servers

Fuel Cells in Data Center– Centralized Implementation

Courtesy to

• eBay Inc. implemented 6MW

fuel cells from Bloom Energy® in

its Utah data center

• A grid parallel configuration

A simple way.

A better way?

Our Design and The In-Rack Generation Systems

• A direct generation method that places fuel cells at the rack

level inches from servers

– limits the failure domain to a few dozen servers

– Low voltage DC direct connection enabled

– Equipment such as power distribution units, high voltage

transformers, expensive switchgear, and AC-DC power

supplies in servers could be eliminated

• Use of a 10 kW PEMFC stack and system as the distributed

power source to power a server rack

• Use of a 2.5 kW SOFC stack and system as the distributed DC

power source to power a server rack

PEMFC Stack and System _ Performance

30%

40%

50%

60%

70%

0

2

4

6

8

10

12

Effic

ie

ncy

Fuel Cell Power (kW)

35

40

45

50

55

60

0

100

200

300

V

oltag

e

(V)

Current (A)

-2

2

6

10

14

0

10

20

30

Po

wer (k

W

)

Time (s)

Total Power

Fuel Cell Power

Battery Power

0kW to 9.0kW at t=10

-2

2

6

10

14

0

10

20

30

Po

wer (k

W

)

Time (s)

Total Power

Fuel Cell Power

Battery Power

PEMFC Stack and System _ Server Dynamics

Cold startup time = 90s

t=30, hybrid system turned on

t=90, FC started purging

t=120, FC met the load

-1

0

1

2

3

4

5

6

0

30

60

90

120

Po

w

er

(kW

)

Time (s)

Total Power

Fuel Cell Power

Battery Power

PEMFC Stack and System _ System Losses

The power outputs of the 12kW in-rack PEMFC system under various external

loads. Error bars in the data indicate + one standard deviation from 5 different

SOFC Stack and System

Engen 2500

Natural gas

208VAC

120VAC

Cooling water out

Cooling water in

Reformer water

Exhaust

Forming gas

Condensate

2.5kW

Combustible gas detector

Ethernet cable

Drain

Air

SOFC Stack and System Performance

• Characterized I-V relation

within the operating range.

• Provide information on

overall data center design:

bus, power supply, DC/DC.

• Electrical efficiency >52%

under standard operating

conditions.

0

10

20

30

40

50

60

70

0

5

10

15

20

25

30

St

ack

V

o

lt

ag

e

(V

)

Current (A)

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0

5

10

15

20

25

30

St

ack

E

ff

ic

ien

cy

Current (A)

SOFC Stack and System Performance

• Characterized the heat

rejected at various power

outputs.

• Provide information on

sizing of the cooling system

for data centers.

• Power to Heat Ratio over 1

at full load.

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

kW

SOFC Stack and System Transient Performance

• Characterized ramping

behavior of the fuel cell

system with controlled

ramp loads.

• Ramp rate of 1 A/s

achieved.

• No significant power

overshoot observed.

• With proper system design

the SOFC system could

ramp fast.

1.5

1.7

1.9

2.1

2.3

2.5

2.7

0

50

100

150

200

Sy

st

em

P

owe

r

(kW

)

Time (s)

SOFC Stack and System Transient Performance

• Ramp up and down

with various ramp rates

were tested.

• System responds

immediately to the

transient demand

perturbation.

• The SOFC system could

follow fast load

transients.

10

15

20

25

30

0

100

200

300

400

500

600

700

800

900

Cur

ren

t

(A)

Time (s)

Current Applied to the Stacks

1.5

2

2.5

3

0

100

200

300

400

500

600

700

800

900

P

o

w

er

(k

W)

Time (s)

Summary and Conclusions

• The use of an in-rack 10 kW PEMFC stack and system and a

2.5 kW SOFC stack and system as the distributed DC power

sources to power a server rack are evaluated.

• The PEMFC hybrid system is found to respond quickly and

reproducibly to load changes directly from the server rack.

• The SOFC stack and system is demonstrated with dynamic

load following capability.

• The implementation of SOFC system in the data center

introduces advantages such as fuel flexibility, and the

production of high quality heat for co-generation or cooling

(e.g., absorption cooling).

Acknowledgement

• Prof. Samuelsen (UCI)

• Richard Hack (UCI)

• Brendan Shaffer (UCI)

• APEP Students and Staffs (UCI)

• Jason Lemos (Hydrogenics)

• Jack Basi (Commscope)

• Francesco Ghigliazza (SOLIDpower)

• Stefano Modena (SOLIDpower)