Page 321 - Sustainable On-Site CHP Systems Design, Construction, and Operations

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Metric Purpose Functional Relation Variables
=
Current Indicate Cost Fuel ∑ Q Price Cost Fuel = total rate of
expenditure the rate of j Fuel, j Fuel, j monetary expenditure on
rate for fuel expenditure fuel for the system
(Cost ) of funds on Q = rate of fuel use
Fuel Fuel, j
fuel for the by fuel input j to the CHP
CHP plant system
Price = price of fuel
Fuel, j
for fuel input j to the CHP
system
TABLE 17-2 Summary of Functional Relations for CHP System-Level Metrics (Continued)

For example, the daily average value for electricity production by the CHP system
based on Eq. (17-57) is given as

24 hours
Daily average electric power output = ∫ W elec dt (17-59)
0
Efficiencies and Utilization Factors
Average value for time period t to t
0 1
t 1
∫ (metricnum )dt
Daily average value = t 0
t 1
∫ (metricdenom )dt
t 0
(17-60)
∑ metrricnum j
n 1
=
≈ n 1 jn 0
∑ metricdenom j
=
jn 0
Example applications of Eq. (17-60) to daily average efficiency or effectiveness and
average over the last n hours follow.
Daily Average Value
24 hours
∫ (metricnum )dt
Daily average value = 0
24 houurs
∫ (metricdenom )dt
0
(17-61)
24
∑ metricnum j
≈ 24 = j 1
∑ metricdenom j
= j 1