Life-Cycle Costs 



In the pay-outs and energy/cost ratios tabulated for each of the 

 selected locations in tables 1 through 4, the first four columns deal 

 with life-cycle costs. A 10-ton unit was selected as the basis for cost 

 comparison because the size range of five to twenty tons at PMTC/NAS 

 Pt Mugu, considered reasonably representative, contained almost half of 

 the 250 cooling unit installations at that location. The basic installation 

 cost, including both the refrigeration and distribution subsystems, was 

 assumed to be equal for typical air conditioning and equipment cooling/ 

 refrigeration installations. At different locations, installation costs 

 (column 1) were adjusted for the geographic construction cost factors of 

 NAVFAC P-448. The net present value (column 2) combines investment and 

 all operating and maintenance costs, including periodic replacement of 

 condensers as well as replacement of complete cooling units „ This was 

 summed over a 30-year period of comparison for installations having units 

 with 5, 10, and 15-year lifetimes, and was calculated using discount factors 

 of NAVFAC P-442. A differential inflation rate of 7% for the cost of 

 electrical energy was also applied per current ECIP guidance. In comparing 

 columns 1 and 2, it is of interest to note that a MILCON investment of 

 $1.00 in cooling facilities also commits the Navy to the simultanrous 

 allocation of between $1.91 and $4.02 for 30-year operation and maintenance, 

 depending on location. Column 3 is simply the equivalent annual cost of the 

 totals from column 2. Column 4 is included to permit calculation of E/C 

 ratios and as an easy comparison of power consumption , since power costs 

 are not separated from the totals of colums 2 and 3. For standard coils, 

 power cost typically ranges between 1/3 and 2/3 of the total annualized 

 life-cycle costs; maintenance ranges between 6% and 10%, with capital 

 costs for the initial installation and major equipment replacement varying 

 between 28% and 54% of the total. 



A significant power cost factor is frequency of coil washing. Periodic 

 coil washings should be part of a station's preventive maintenance program. 

 Calculations of life-cycle costs included a preliminary evaluation of 

 more rapid coil performance degradation and added power consumption when 

 coils were not washed regularly. Infrequently washed or unwashed coils 

 subject to airside fouling in marine atmospheres were estimated to result 

 in higher power costs of approximately 15% and 25%, respectively. 



Pay-Outs and Energy/Cost Ratios 



The last four colums of tables 1-4 present simple pay-outs and energy/ 

 cost ratios, using data from the first four columns. For both pay-out 

 and E/C ratio, comparisons are made to the least cost or least efficient 

 standard coil and to the next least expensive coil alternative. Thus, the 



6 

 Power consumption estimates are based on running time, a rational 

 analysis of which is contained in Code L03B file memo dated 9 April 

 1979 entitled, "Estimating Energy Requirements Based on Relative 

 Heat Transfer" 



38 



