Development and testing of the fuel cell power module for 3-ton electric

forklift LOTOTSKYY, Mykhaylo; PARSONS, Adrian; TOLJ, Ivan;

KLOCHKO, Yevgeniy; KHAN, Irshad; BREY, Ali;

SHENKER, Maurice; SMITH, Fahmida; SITA, Cordellia;

LINKOV, Vladimir

Background

AC Motors

DC / AC DC / DC

Battery

Auxiliaries

CGH2

+MH

H2 storage:

FC

MH H 2 purification

& compression

system H 2 ; P~50 bar

H2

HEAT

AIR

HP buffer

A

C

Cooling water

Steam Condensate

Pure H 2 P≤200 bar

80 VDC MAX 300 ADC

Forklift equipment

Power module components

Original developments

within this project

B

• In 2012-2015, HySA Systems integrated a metal hydride (MH) H2

storage extension tank in a commercial GenDrive 1600-80CEA fuel cell power module (Plug Power Inc.) which was installed in a 3 tonne STILL electric forklift.

• Main performances (VDI-60):➢ Energy consumption 11.15 kWh/h.➢H2 fuel consumption 689 NL/kWh

(CGH2 31%, MH 69%).

• The prototype is in operation at Impala Platinum refineries in Springs, South Africa, since September 2015.

• Main malfunctions identified were mainly related to Li-ion battery.

[1] Lototskyy, M.V. et al., Metal hydride hydrogen storage and supply systems for electric forklift with low-temperature protonexchange membrane fuel cell power module Int. J. Hydrogen Energy, 41 (2016) 13831-13842. [2] Lototskyy, M.V. et al., Performance of electric forklift with low-temperature polymer exchange membrane fuel cell power module and metal hydride hydrogen storage extension tank J. Power Sources, 316 (2016) 239-250

Specification and concept design

Fuel Cell Stack

MH Bed Encased in Lead

Anode Humidifier

Air Intake Filter

Compressor Motor Drive

Cathode Air Compressor

8.4 kWh SLA Battery Bank

Cooling Radiator and fan

Cathode Heat Exchanger

System Control Electronics

H2 Recirculation Pump

H2 Reducer

• Donor vehicle: STILL RX60-30L;• Bus voltage (VDC): 80;• Output power (kW): ~15 (average), up to 30 (peak);• Dimensions (mm): 840 (L) x 1010 (W) x 777 (H);• Weight (kg): 1800…1900

➢ Stack: closed cathode FC;➢ H2 storage: integrated MH

storage unit, 20 Nm3;➢ Battery bank: deep cycle

lead-acid, 8…10 kWh.

BoP design• The BoP designed

around Ballard 9SSL / 75 Cell FC Stack.

• Main subsystems include:o The Cathode, Air

Subsystem;o The Anode, H2

Subsystem;o The Closed Circuit

Water cooling (stack) / heating (MH) subsystem.

• Challenges:o Component selection

constraints (availability, functionality & performance, size);

o Insufficient weight (ballast required);

o Alignment of the communication protocols

AIR MASS FLOW

METERAIR FILTER

A

N

O

D

E

T1

MANUAL SHUT-

OFF VALVE

P8C

O

O

L

A

N

T

M

M

AIR Scroll

COMPRESSOR

Cathode Heat

Exchanger

GAS – GAS

HUMIDIFIER

HYDROGEN

PURGE VALVE

HYDROGEN

RECIRCULATION

PUMP

O2 IN

CHECK

VALVE

H2 Line

H2 Supply

from Metal

HYDRIDE

Bed

SV

AIR STOICHIOMETRY = 1.8

H2

STOICHIOMETRY = 1.6

CHECK

VALVE

O2 OUT

H2 IN

From Cooling

System

Cooling

System Return

From Cooling

System

Cooling System

Return

Compressor

Motor Drive

H2 Buffer Tanks

MANUAL SHUT-

OFF VALVE

H2 Charge

Input

From Cooling

System

Cooling System

Return

CHECK

VALVELIQUID H2O

KNOCKOUT

LIQUID H2O

KNOCKOUT

H2O DRAIN

EXHAUST

MANUAL SHUT-

OFF VALVE

CHECK

VALVE

Metal

Hydride

Bed

Ba

llard

9S

SL

/ 75

Ce

ll Fu

el C

ell S

tack

H2

H2 Leak

detector

H2

H2

Concentration

Sensor

Pressure

Reducing Valve

AIR REFERENCE

PRESSURE

H2 OUT

P1

T2P2

T4P4

C

A

T

H

O

D

E

T3P3

T5P5

ISOLATION

VALVE

V-41

T6P6

P7

Air Reference

Pressure

V-43

ISOLATION

VALVE

RH

1

RH

2

Thermal Insulation

Thermal InsulationTherm Insu

Th

erm

al In

su

latio

n

Thermal InsulationThermal Insulation

H2

Air

Temperature control

Stack cooling / MH heating system• Stack cooling system is coupled with the

system of heating the MH tank

Gas supply systems

MH bed

MH hydrogen storage• Main challenge of conventional solution (MH

containers in a water tank) is insufficient system weight. Suggested approach: assembly of cassettes each comprising several MH containers encased in lead.

• Special procedure of lead encasing which allows to simultaneously activate the MH material in the MH cassette has been developed.

• When heated with running water to T=40–50 °C, the cassette releases more than 60% of its full capacity (~2.5 Nm3) at the H2 flow rate of 25 NL/min.

• 8 MH cassettes have been manufactured and installed in the frame of forklift power module to form, together with 9L buffer cylinder, a hydrogen storage tank.

• The tank is characterised by H2 storage capacity above 20 Nm3 (1.8 kg) and has a weight ~1.2 tonnesthat allows to provide counterbalancing weight (1850 kg for the whole power module within the space constrains) necessary for the safe operation of 3 tonneforklift.

• The tank can provide >2 hour long H2 supply to the FC stack operated at 11 kWe (H2 flow rate of 120 NL/min).

• The refuelling time of the MH tank (T=15–20 °C, P(H2)=150–180 bar) is about 15–20 minutes.

✓ Patent application filed: UK1806840.3; 26.04.2018

Lead encasing

Left: two ready-to-use MH cassettes. Right: MH tank for forklift power module comprising 8 MH cassettes

0 20 40 60 80 100 120

0

10

20

30

40

50

H2 flow rate [NL/min]

H2 pressure [bar]

T(MH) [oC]

T(in) [oC]T

, P

, F

R

Time [min]0 20 40 60 80 100 120

0

10

20

30

40

50

60

H2 pressure [bar]

H2 flow rate [NL/min]

T(MH) [oC]

T, P

, F

R

Time [min]

T(in) [oC]

H2 charge (left) and discharge (right) performance of the MH cassette; water flow ~4 L/min

System prototyping• All BoP components have been identified,

procured and assembled off-board;• Most of the components are standard, from

automotive industry;• Main challenge – the communication

interface link between the various components;

• The PLC supplier has developed special firmware for the control system to enable it to communicate with the components via CAN2.0 protocol;

• The CAN implementation has been completed, and all of the BoP components requiring CAN bus communication have been integrated into a network controlled by an industrial PLC system;

• Original cell voltage monitoring system has been developed;

• The switching Load Bank Resistors have been introduced to emulate various operating conditions.

➢ The off-board test results will be presented below.

HMI screenshots

Electrical layout (1)

• Initial configuration: auxiliary DC/DC converters are connected to 84 (7 x 12) V battery terminals

Electrical layout (1): test results

0 500 1000 1500 2000

0

50

100

150

200

250

300

350

H2 f

low

, C

urr

ent,

Voltage

time [seconds]

Battery voltage [V]

FC current [A]

H2 flow [NL/min]

0

2000

4000

6000

8000

10000

12000

14000

Sta

ck P

ow

er

[W]

Stack power [W]

1700 1800 1900 200060

70

80

90

time

Voltag

e• At maximum stack

power, the battery voltage drops below the minimum voltage required for the operation of the auxiliary DC/DC’s resulting in the stack shut-down.

• Origin – too high internal resistance of the lead-acid battery.

➢ Electrical layout should be modified.

Electrical layout (2)

• Revised configuration: auxiliary DC/DC converters were removed (auxiliaries connected directly to 24 V and 48 V branches of the battery bank); one battery was removed from the bank.

Electrical layout (2): test results

• No battery voltage drop was observed.

• Unstable operation when the load power (peaks) exceeds MAX stack power.

• Heating-up the battery during the operation at high load power (incl. peak load).

➢ Electrical layout should be further modified

0 1000 2000 3000 4000 5000 6000

0

50

100

150

200

250

300

350

400

450

500

Cu

rre

nt,

Volta

ge

time [seconds]

Battery voltage [V]

FC current [A]

0

1600

3200

4800

6400

8000

9600

11200

12800

14400

16000

BoP power [W]

Pow

er

Stack power [W]

Electrical layout (3)

• Revised configuration: To compensate for the peak power draw of the load, an ultra capacitor was added to the system in parallel with the Lead Acid battery

Electrical layout (3): test results• Stable operation at peak power up to 30

kW.• The battery contribution to the load power

during the peaks decreases in ~2 times due to the contribution of ultra capacitor.

• The battery is not heated-up.• The battery depth of discharge is also

significantly lower than for the layout (2).• Average fuel cell power required is ~8 kW.

✓ Average energy consumption ~ 9.0 kWh/h✓ Average load power ~ 8.1 kW✓ Average BoP power ~ 900 W✓ Average H2 consumption ~ 900 NL/kWh✓ Estimated system efficiency ~30%

(related to HHV)

3000 3200 3400 3600 3800 4000

0

20

40

60

80

100

Ba

ttery

volta

ge

[V

]

time [seconds]

Battery voltage

0

5000

10000

15000

20000

25000

30000

35000

40000

Battery power Load power

BoP power

Po

we

r [W

] Stack power

0 1000 2000 3000 4000

0

5000

10000

15000

20000

25000

30000

35000

Po

we

r [W

]

time [seconds]

Load power

Stack power

Assembling on-board prototype• Based on the test results

presented above, the BoPconfiguration has been updated.

• All BoP parts for the on-board prototype have been procured.

• Assembling of the prototype power module is in progress.

• The control algorithm is being finalised towards:o Automatic switch of the

stack to a) Standby, b) Run and c) Shutdown modes depending on the system status;

o Optimisation of the fuel supply and purging strategy to reduce H2 consumption and increase efficiency.

Conclusions• General layout of fuel cell power module for 3 tonne electric forklift

with integrated MH hydrogen storage system has been elaborated.• The module fits in the space and weight constrains of the application

and comprises the following components: o 14.5 kW closed cathode PEMFC stack (Ballard);o Lead-acid battery bank;o Advanced metal hydride hydrogen storage tank (20 Nm3 H2).

• Test bench prototype of the power module has been built and tested in various hardware configurations.

• The optimal electrical system layout providing it stable operation at presence of peak loads (up to 30 kW) has been identified including:o Powering of auxiliary system components directly from the

sections of the battery bank;o Sizing of the battery bank;o Introducing ultra-capacitors.

• Further increase of the overall system efficiency by the optimisation of purging strategy, together with the assembling of the on-board prototype, is underway.

Acknowledgements

• Impala Platinum Limited – co-funder;

• Department of Science and Technology (DST) via HySA Programme (projects KP3-S02 and KP3-S03) – co-funder;

• European Commission, Grant Agreement number: 778307 –HYDRIDE4MOBILITY – H2020-MSCA-RISE-2017 “HYDRIDE4MOBILITY” –support of international collaboration.