Environmental Engineering Reference
In-Depth Information
Fig. 7.4 Individual cell
voltage for the 20 kW PEM
stack at open circuit,
T = 346 K and
P
air
= 250 kPa
Fig. 7.5 Individual cell
voltage for the 20 kW PEM
stack at full load, T = 346 K
and P
air
= 250 kPa
humidify the inlet air at 70C, P
cool
refers to the heat absorbed by water cooling,
P
airout
is associated with the enthalpy of the cathode outlet stream, and P
H
2
is the
power related to the fuel fed to the stack, calculated by hydrogen high heating
value, taking into account the fuel utilization coefficient (see
Sect. 7.2
). All the
above power terms are calculated from experimental measurements, except for the
air supply consumption, since a centralized compression plant is used for all tests
conducted at higher pressure. For this reason, the compression consumption is
estimated from the literature [
1
,
2
]. It can be noticed that the power entering the
stack as fuel P
H
ðÞ
is recovered as stack electric power (P
stack
), cooling heat (P
cool
)
and as part of the heat flowing from cathode side (P
airout
). Whereas, the main
energy losses are due to the humidification and compression devices (8.5 kW at
