Page 162 - Handbook of Energy Engineering Calculations

$974,988; this was rounded to $975,000. Since the difference in the initial
cost between units D and E is $6,720,000 - $4,200,000 = $2,520,000, this
cost difference will be recovered in $2,520,000/974,988 - 2.58 years, or about
one-eighth of the 20-year life span of the equipment.
Also, note that the 20-year differential in cost/kWh produced between units

D and E is equivalent to over 4.6 times the initial equipment cost of unit E.
When considering the values output of a life-cycle model, remember that
such values are only as valid as the data input. So take precautions to input

both reasonable and accurate data to the life-cycle cost model. Be careful in
attempting to distinguish model outputs that vary less than 0.5 mil from one
another.
Since the predictions of this life-cycle cost model cannot be compared to
actual measurements at this time, a potential shortcoming of the model lies

with the validity of the data and assumptions used for input. For this reason,
the model is best applied to establish comparisons to differentiate between
several pieces of competing equipment.

Related Calculations. The first gas turbines to enter industrial service in the

early 1950s represented a blend of steam-turbine and aerothermodynamic
design. In the late-1950s/early-1960s, lightweight industrial gas turbines
derived directly from aircraft engines were introduced into electric power
generation, pipeline compression, industrial power generation, and a variety

of other applications. These machines had performance characteristics similar
to their steam-turbine counterparts, namely pressure ratios of about 12:1,
firing temperatures of 1200–1500°F (649–816°C), and thermal efficiencies in
the 23–27 percent range.

In the 1970s, a new breed of aeroderivative gas turbines entered industrial
service. These units, with simple-cycle thermal efficiencies in the 32–37
percent bracket, represented a new technological approach to
aerothermodynamic design.

Today, these second-generation units are joined by hybrid designs that
incorporate some of the aeroderivative design advances but still maintain the
basic structural concepts of the heavy-frame machines. These hybrid units are
not approaching the simple-cycle thermal-efficiency levels reached by some

of the early second-generation aeroderivative units first earmarked for
industrial use.