A Life Cycle Assessment of the PureCell Stationary Fuel Cell System ...

Electricity Generation
The input of natural gas and the emissions caused by the steam reforming process are
taken into account here. Table 4-24 gives the natural gas input and the emissions for the
production of 200 kWh, which is equal to running the PureCell system for one hour.
These data are given to show which calculations were used to determine the emissions.
Thereafter these data are scaled up to the PureCell system lifetime of 85,000 hrs in
order to provide the inventory data which are needed to describe the PureCell system’s
total life cycle.
Products Amount Unit
Generated electricity, 480 Volt, 60 Hz 200 kWh
Produced heat at 140 F 271.025 kWh
Materials/fuels
Natural gas FAL (Franklin) 2050 cuft
3
Emissions to air
NOx 0.0032 lb
CO 0.0046 lb
CO2 112.2 kg
non-methane hydrocarbon (NMHC) 0.000072 lb
Table 4-24: 200 kWh electricity generation inventory data
The natural gas input and the emission of NO , CO and NMHC are data measured by
UTC Power [21]. The CO
2
emissions however are calculated, since no measured data
are available. The calculations are based on the assumption that natural gas is
100% CH 4
. In practice, this is usually around 95%, with the other 5% mainly including
ethane, nitrogen, and higher order hydrocarbons. Another assumption is that all the
carbon input results in CO
2
output, thereby neglecting the CO and NMHC emissions.
The calculations are based on the steam reforming and low shift reactions:
CH + +
(steam reforming)
4
H
2O
→ CO 3H
2
CO + H +
(shift reaction)
2O
→ CO2
H
2
This results in the following overall reaction:
CH 2 + H
4
+ H
2O
→ CO2
4
2
x
3 cuft = cubic feet
41