request competitive bids. To pursue ESPC financing under the IDIQ, simply provide IST staff with the necessary information and they will determine whether it would be economically advantageous for them to build the system or—as they have for all their installations thus far—convince a third party to finance the project. To save on lim- ited travel funds, IST personnel will usually do a preliminary assessment by telephone to determine whether economics are promising enough for them to further investigate the project and whether a DORFP should be done. They will look for the following positive factors.
• Expensive utility rates for conventional water heating—about $6/MBtu or more (2ў/kWh of electricity, 60ў per therm of natural gas, 55ў per gallon of propane, or 83ў per gallon of fuel oil; average energy costs for Federal facilities in FY 1995 were 6.1ў/kWh of electricity, 35ў per therm of natural gas, 64ў per gallon of propane, and 60ў per gallon of fuel oil, according to a FEMP survey) • High direct normal solar radiation— 4 kWh per square meter or more, loca- tion in the three or two highest bands, respectively, in Figures 5 or 6 on pages 6 and 7.
• High levels of hot-water use—10,000 gal- lons per day or more; or a long cooling season of 9 months or longer • Continuous facility use—preferably 7 days per week, 52 weeks per year • Adequate unshaded space for the collec- tor field • For air-conditioning, inability to tolerate system shutdown during a power failure. Certainly, it is not always necessary to meet each of these criteria. Furthermore, a very high indication in one area, such as energy costs, could overshadow counter- indications in another area. Lower sunshine levels or hot-water use might suggest alter- native solar water-heating technologies.
(7) Central plants for district heating or water-heating systems (8) Operation and maintenance (O&M) facilities, such as for transportation vehicles and equipment, requiring large volumes of hot water (9) Production or assembly facilities requiring large amounts of hot water (e.g., munitions facilities) (10) Gymnasiums and recreation facilities with heated, indoor swimming pools (11) Bachelor officer quarters and guest residential facilities (12) Any other facility requiring large amounts of hot water on a continuous basis or otherwise meeting most of the criteria listed in “Application Screening.” • Oversizing the system so full capacity is not always used (if not an ESPC) • Lack of commitment to system mainte- nance (if not an ESPC).
Equipment Integration Integrating the parabolic-trough collector system into the existing hot-water system is simply a matter of adding a line routing the cold intake water through the heat exchanger in the thermal storage tank on its way to the existing conventional water heater. Prisons with security perimeters might need to penetrate a wall to do this. The collector field requires electrical con- nections for the pump and the tracking sys- tem. Valves are included for the intake and outflow of the fluid loop and one is added on the old line direct to the water heater, making it easy to bypass the parabolic- trough system if ever necessary.
What to Avoid If purchasing a system or seeking an ESPC project, one should be aware of cer- tain considerations. No one of these situa- tions would preclude a project, but be sure to inform IST staff about:
• Areas particularly prone to very severe weather—high winds, tornados, hail storms or hurricanes—or to vandalism • Areas with unusually high dust or dirt loads in the air • Particularly mineral-rich water supply (can foul the heat exchanger and the rest of potable loop—less of a problem for troughs than for other solar water-heating systems) • Facilities facing possible closure or reduction in hot-water or air-conditioning use • Missed opportunities to make a parabolic- trough project more economically attrac- tive by adopting water conservation measures, switching fuels, or installing more efficient conventional water heaters as part of the project.
(The IDIQ does allow such measures to be incorporated into and financed as part of a trough project and IST will investigate their inclusion.) • Situations where a conventional energy source is expected to become available that is significantly less expensive than that currently used • Situations where the space dedicated to the collector field could later be needed for building expansion Maintenance Impact Parabolic-trough collector systems require somewhat more maintenance than most nonconcentrating solar water-heating or other renewable energy or energy efficiency installations. Because high- temperature and high-pressure fluid is involved, they should be monitored regu- larly.
Also, the mirror surfaces should be washed every few months. Consequently, although facility staff could easily take on these duties, the system installers usually also maintain the system. Under an ESPC, this is standard practice. The mirror surfaces will degrade slowly with time and may need replacement after about 15 years. The pumps and tracking equipment should last for the life of the pro- ject, but the pump seals will likely need to be replaced after about 10 years and the tracking equipment controls may need replacement as soon as 10 years or as late as 30 years.
Because the solar collector system reduces the amount of time that the conven- tional hot-water heater operates, the heater should last longer. There is no other real impact on existing equipment. Where to Apply This technology is best applied at: (1) Hospitals (2) Other large health care facilities such as large clinics (3) Military and civilian detention facilities (4) Food preparation and service facilities (5) Dormitories and barracks (6) Laundries Equipment Warranties If IST sells a system, they guarantee the general collector system for 5 years; individual components such as pumps carry whatever warranty the manufacturer pro- vides. Note that under an ESPC, replace- 15