APC 400kW1MW User Manual download pdf (Page 45)

Table 5-1 was taken from the “Report to Congress on Server and Data Center Energy

Efficiency Public Law 109-431” and compares the emissions of a PEMFC and a diesel

generator. The first set of data is the amount of pollutant that would be emitted per hour of

equipment use. In one hour, the diesel generator would emit 20.282 lb/MW of nitrogen oxides,

while the PEMFC would only emit 0.100 lb/MW. The second set of data is the total emissions

that the PEMFC and diesel generator would emit if they were used to backup power for 24

hours in one year. It should be noted that in this comparison, the diesel generator has a much

larger power generating capacity of 600 kW compared to the 150 kW of the PEMFC. However,

if multiple PEMFCs were used to provide 600 kW of power, the total emissions from the

PEMFCs would still be much less than those of the diesel generator [1, p. 78].

Table 5-1 Emissions of a PEMFC versus a Diesel Generator [K]

PEMFC Diesel Generator

Capacity, kW 150 600

Heat Rate, Btu/kWh 9,750 10,000

Emissions Factors

, lb/MWh 0.100 20.282

, lb/MWh 0.006 2.900

, lb/MWh 1,170 1,650

Annual Emissions (based on 24 hours of operation per year)

, lb/MW-year 2 487

, lb/MW-year 0.14 69.60

, ton/MW-year 14 20

(NO

= Nitrogen Oxides, SO

= Sulfur Dioxide, CO

= Carbon Dioxide)

5.3 Increased Reliability

As discussed in section 3.1, the reliability of primary and secondary power for data

centers is crucial in order to maintain business and avoid major losses. The typical data center

is equipped with emergency generators to provide backup power in the case of a grid

disturbance or short term outage. However, generators are only designed to provide power for

an intermittent use and have reduced reliability from engines failing to start [29, pp. 170-171].

As seen in Figure 5-2 well maintained generators fail to run for 24 hours 15% of the time. In

order to increase diesel generator reliability, data centers have redundant generators [62, p. 6].

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APC 400kW1MW User Manual Page 45