Specific energy consumption of PEM water electrolysers in

atmospheric and pressurised conditions

Joonas Koponen, Antti Kosonen, Kimmo Huoman, Jero Ahola, Tero Ahonen, and Vesa Ruuskanen

/ Outline of the presentation

• Introduction

• Compression methods

• Experimental work

• Conclusion

1. INTRODUCTION

/ General overview

/ PEM water electrolysis IRD E1050 • 4.5 kW nominal power• 1 Nm3/h of H2• Max. 50 bar (H2)• 33 cells• 69 cm2 cell area

2. COMPRESSION METHODS

/ The reversible voltage as a function of pressure

• If the hydrogen pressure increases from 2 bar to 50 bar, the reversible voltage increases by 4 %

PEM water electrolysis

/ Idealized post-electrolysis compression methods

To 50 bar: • Adiabatic one-stage 0.3 kWh/Nm3

• Adiabatic two-stage 0.2 kWh/Nm3

HHV of hydrogen is 3.54 kWh/Nm3

3. EXPERIMENTAL WORKTHE EFFECT OF H2 OUTLET PRESSURE

/ Laboratory setupHydrogen system by a Danish company

IRD• Hydrogen storage 0.7 m3 (~120 kWh at

50 bar)

/ Hydrogen production rate estimation (1/2)

• Hydrogen production rate estimated based on the stack DC current in the

IRD system

• IRD’s own current sensor used

• Verification using high-accuracy zero-flux current transformer, 300 A

– Absolute error, compared to IRD’s sensor, within 1 A in the control range of the electrolyser

• Verification of the production rate by monitoring the hydrogen storage

pressure and outdoor temperature

/ Hydrogen production rate estimation (2/2)

Estimated: stack DC current Calculated: change in storage pressure

Stack power 4.6 kW

1.02 Nm3/h

1.00 Nm3/h

/ The effect of the hydrogen gas outlet pressure

• In each test run the hydrogen storage (0.7 m3) is filled from 10 bar to 15 bar

• 20 bar, 30 bar, 40 bar

• Operation of the hydrogen dryer sets the minimum hydrogen outlet pressure

• Test runs as a function of load with 25 % steps (of nominal load)

• H2 in O2 increases as current density decreases or as pressure increases

/ Performance and operation of the PEM stack (1/2)

LoadMean stack

voltage

Mean stack

current

Mean H2prod. rate

Hydrogen produced

Specific energy cons.

Stack efficiency

(%) (V) (A) (Nm3/h) (Nm3) (kWh/Nm3) (%HHV)Hydrogen outlet pressure 20 bar

25 54.7 17.7 0.24 3.40 3.98 88.950 56.0 35.5 0.49 3.21 4.06 87.275 58.4 52.8 0.73 3.04 4.23 83.7100 61.6 70.4 0.97 3.19 4.47 79.2

Hydrogen outlet pressure 30 bar50 56.2 35.5 0.49 3.20 4.07 87.075 58.4 52.8 0.73 3.40 4.22 84.0100 61.6 70.4 0.97 3.57 4.47 79.2

Hydrogen outlet pressure 40 bar100 61.3 70.4 0.97 3.09 4.45 79.6

/ Performance and operation of the PEM stack (2/2)

/ Conclusion

• The measurements show no notable increase in the specific energy

consumption of the electrolyser stack as the hydrogen outlet pressure is

increased from 20 bar to 40 bar

• Partial load operation is limited, if hydrogen outlet pressure is increased

• The measurement system for stack voltage, stack current, hydrogen

storage pressure, and hydrogen storage temperature will be upgraded and

improved

/ Conclusion

Published in: J. Koponen, A. Kosonen, K. Huoman, J. Ahola, T. Ahonen, and

V. Ruuskanen, “Specific energy consumption of PEM water electrolysers in

atmospheric and pressurised conditions,” in Proc. 18th European Conf. on

Power Electron. and Applicat. (EPE ‘16–ECCE Europe), Karlsruhe, Germany,

Sep. 2016.

Thank you!

Questions? Comments?