unitized regenerative fuel cells for hydrogen energy...

H. Ito, Japan-Norway Energy Science Week 2015, 28 May 2015, Tokyo H. Ito, Japan-Norway Energy Science Week 2015, 28 May 2015, Tokyo 1

Unitized Regenerative Fuel Cells for

Hydrogen Energy Storage Systems

Japan-Norway Energy Science Week 2015

Hiroshi Ito, Akihiro Nakano

National Institute of Advanced Industrial Science and Technology (AIST)

Naoki Miyazaki, Masayoshi Ishida

University of Tsukuba


Outline

1. Background / Scope

2. R&D on Unitized Regenerative Fuel Cell (URFC)

3. R&D on Hydrogen storage with metal hydride

4. Summary


Grid Independent RE-Hydrogen System

Grid Connected RE-Hydrogen System Hydrogen may be used as fuel in

almost every application where fossil fuels are being used today.

Hydrogen is useful as an energy

carrier, because energy storage density is significantly high with compressed form, liquefied form, or metal hydride.

From sustainability point of view,

a synergy between hydrogen and electricity and renewable energy sources is particularly promising.

Hydrogen production with water

electrolysis must be suitable for renewable energy sources.

. F. Barbir, Solar Energy 78 (2005) pp. 661-669.

A Synergy between Hydrogen and Electricity


Totalized Hydrogen Energy Utilization System (THEUS)

Hydrogen station

To enhance the versatility of hydrogen energy in the industrial, the commercial, and the transportation sectors through THEUS.


Outline

URFC and MH tank have been evaluated as key components of hydrogen energy system in stationary applications.

A bench-scale URFC was installed and would be evaluated as an energy

conversion system. MH tank was developed by own and evaluated in a long time operation.

In particular, we have been focusing on the thermal energy recovery

from the both operations of URFC and MH tank.


Overview of Unitized Reversible Fuel Cell (URFC)

URFC System

Cell reactions

Advantages Long-term and large quantities of energy

storage compared to current secondary batteries.

Continuous running permits to make a rate of operation double compared to individual use of FC and Ely.

Acquisition of oxygen as by-products

Electrolysis Overall : H2 electrode (cathode) : O2 electrode (anode) :

Fuel Cell Overall : H2 electrode (anode) : O2 electrode (cathode) :

+22H 2e H ( )g−+ → ↑

+2 2H O( ) 2H 1/ 2O ( ) 2el g −→ + ↑ +

2 2 2H O( ) H ( ) 1/ 2O ( )l g g→ +

2 2 2H ( ) 1/ 2O ( ) H O( )g g l+ =+

2H ( ) 2H 2eg −→ ++

2 21/ 2O ( ) 2H 2e H O( )g l−+ + →

URFC

Hydrogen Storage Unit

H2 H2

Pure Water

Fuel Cell (FC)

Power OutputPower Input

Heat

Water O2/Air

Electrolyzer (Ely)

Possible applications Hydrogen energy storage system for load

leveling at buildings Remote hospital Lake water purification Remote UPS system


←DC Power

←DC Load

←Chiller

DI water supply

URFC stack

Installation of a bench-scale URFC

Overview

Inside

• Installed in March 2014 • Supplied from Takasago Thermal Engineering Co.


Specifications of bench-scale URFC

Electrolysis operation

Input power (rated) 4.5 kW Gas production rate H2: 1.0Nm3/h, O2: 0.5Nm3/h Gas pressure H2: 0.9MPa(G)_max, O2: Atmospheric

Fuel cell operation

Power output (rated) 0.8 kW H2 utilization >90% H2 pressure <0.05MPa(G)

System

Cell/stack Membrane Nafion 115

Electrocatalyst H2 side Pt O2 side Pt/Ir-black

Active area 250 cm2


Schematic draw of gas/liquid flows around URFC

Circulationpump

Water purifier

Membranehumidifier

Chiller

Chiller

Blower

Water drain

Air

Air / O2

DI water

Chiller

Circulationpump

Chi

ller

BH2

H2

Gas (O2)-waterseparator

Gas (H2)-waterseparator

Circulationpump

Pump-1

Pump-2

Pump-3

BLW

Component Rated power consumption

Cooling water pump (Pump-1) 90 W Water circulation pump (Pump-2) 60 W H2 circulation pump (Pump-3) 26 W Air blower (BLW) 500 W

• Hydrogen is recirculated. • Air is humidified using a membrane humidifier.


Electrolysis operation - i-V characteristics

At 40°C

14

15

16

17

18

19

0 0.2 0.4 0.6 0.8 1 1.2C

ell s

tack

vol

tage

[V]

Current density [A/cm2]

900 kPaG(60°C)

500 kPaG(60°C)

0 kPaG(60°C)

14

15

16

17

18

19

0 0.2 0.4 0.6 0.8 1 1.2

Cel

l sta

ck v

olta

ge [V

]


900 kPaG(40°C)

500 kPaG(40°C)

0 kPaG(40°C)

At 60°C

The effect of temperature on the performance was relatively large, while the effect of pressure was small.


Fuel cell operation

4

5

6

7

8

9

10

0 0.1 0.2 0.3 0.4 0.5 0.6

Cel

l sta

ck v

olta

ge [

V]


70 °C

60 °C

The cell/stack performance was significantly influenced by the operating temperature, which should be higher than 60 °C.


Continuous operation

H2 pressure

Current

Voltage

Cell temp.

Fuel cell mode Electrolysis mode Switching (ca. 5min)

←0.9MPa 75℃→

100A→

7.9V→

←22V

←60℃

←250A

Switching

Current

Voltage

Cell temp.

Since the operation interface was well-organized, the system could be operated and switched easily. Switching time was 5-10 min.


Schematic of the experimental set-up

Metal hydride bed in AIST

Experimental set-up of MH tank


Metal Hydride Tank

(Metal hydride alloy) - Japanese version - Composition: MmNi5 Total weight: 50 kg Size：500 μm Reaction heat ∆h Absorption： 28.93 kJ/molH2 Desorption： 27.87 kJ/molH2


Individual absorption/desorption test results

H/M=0.18-0.94 MH utilization ratio: 94% GH2: 5920 NL

Operating conditions （Absorption: 9 hour） H2 flow rate: 11.0 NL/min Circulation water : 32 ℃, 1.12 l/min （Desorption: 13 hour） H2 flow rate: 7.6 NL/min Circulation water : 12 ℃, 0.46 l/min

P-C isotherm Absorption Desorption

Qcw = 6.84 MJ, ε = 89.4 % Qcw = 6.62 MJ, ε = 89.8 %

Reaction heat recovery rate：ε = (Qcw/QMHreact)×100

∵QMHreact = VH2×∆h

Recoverd thermal energy from coolant: Qcw


Absorption-desorption continuous test results

(a) P-C isotherm (b) Temperature of coolant

Reaction heat recovery rate, ε Day1 AB 87.4 % DS 73.3 % Day2 AB 75.4 % DS 72.5 % Day3 AB 76.2 % DS 72.3 %


Summary

In this study, we investigated the performance of URFC and MH tank as key components of hydrogen storage system. The bench-scale URFC could operated quite successfully. The performance of each operation mode in URFC was comparable

with that of individual apparatus of PEM electrolyzer and PEMFC. MH tank was developed and tested in daily cycle operation.

Reaction heat recovery rate was excellent as over 70 %.

The connection between URFC and MH tank was completed, and

consolidated test is ongoing.

H. Ito, Japan-Norway Energy Science Week 2015, 28 May 2015, Tokyo H. Ito, Japan-Norway Energy Science Week 2015, 28 May 2015, Tokyo

Thank you very much for your attention!

18

Hiroshi Ito [email protected]

unitized regenerative fuel cells for hydrogen energy...

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