DOE EERE Research Reports

Sufficient pre-retrofit data have been collected at one site (the 82nd Heating and Cooling Steam Plant at Fort Bragg, North Carolina) to perform an analysis and project possible fuel use and electrical production. One configuration of equipment is considered—three 3.5 MW gas turbines with heat recovery steam generators and a supplemental boiler for peak loading—and compared with the existing gas-fired steam boiler plant. Turbine operation is controlled to meet the distribution system thermal loads, while electricity produced offsets purchases that would be made from the local utility. It is projected that one gas turbine would operate continuously, a second would operate at full load 92% of the time and at part load 8% of the time, and that the third would operate at full-load 54% of the time and at part load 38% of the time and would be idle 8% of the time. Gas turbine operation would provide 495.2 (469,700 ×106 Btu) of the 583.5 TJ (553,400 × 106 Btu) annual thermal load while producing 86,490 MWh of electricity; natural gas use increases from 748 TJ (7.10 × 106 therms) using the steam boilers to 1210 TJ (11.5 ×106 therms) for the turbines and supplemental boiler.

Estimated reductions in energy costs are heavily dependent on the relative costs of electricity and natural gas. On-site generation avoids purchases of approximately $2.5 million of electricity based on the average real time prices for 1998 through 2000. The net difference in costs for natural gas between the existing boiler plant and the proposed gas turbine plant is about $1.61 million. Savings in energy costs would be approximately $890,000 per year using average 1999 natural gas rates for industrial customers in North Carolina.