Save Energy et al., 1992). Despite these different assumptions, coal is still projected to be a major energy source for power generation in 2010.
The additional generating capacity does not necessarily require the construction of new plants. Repowering, broadly defined to include any activity that stabilizes or reverses the age-induced deterioration of generating units (Makovich and Smalley, 1993), can result in improved efficiency and increased generating capacity at less than replacement cost. According to some projections, an emphasis on repowering—including performance optimization, component replacement, component refurbishment, life extension, and/or unit upgrading—is likely over the next decade (Makovich and Smalley, 1993). This forecast trend is consistent with the low number of scheduled power plant retirements reported to the North American Reliability Council for the period through 2003. Although a large number of the fossil-fuel-fired steam plants operating today are nearing the end of their nominal life (40 to 45 years), utilities appear to be planning to continue using them for the foreseeable future (EIA, 1994b).
The choice of technologies to meet additional generating capacity requirements depends on both peak load and baseload needs. Peak load is the maximum load during a specified period of time, whereas baseload is the minimum amount of power required during a specified period at a steady state. According to EIA projections (EIA, 1994a), there will be a need through 2010 for flexible generating technologies, such as gas-fired or oil- and gas-fired combined-cycle and combustion turbine systems, designed primarily to meet peak and intermediate load requirements but able to meet baseload requirements as needed. Peak load requirements are anticipated to increase from 589 GW in 1994 to 804 GW in 2010 (Makovich and Smalley, 1993).
How much of the projected demand for electricity is likely to be supplied by coal? This section addresses the major competing sources of energy for electric power generation over the time periods of interest for this study. More extensive discussions can be found in the various references cited throughout this section.
The coal base of the world is large, some 1,145 billion tons. The top two producing countries are China and the United States. The U.S. demonstrated reserve base (DRB) of coal is now estimated to be 474 billion tons (EIA, 1992). The DRB is the amount of coal that can potentially be mined by surface or underground methods. The amount of coal that can be extracted economically using available technology, taking into consideration the laws, regulations, economics, and usages that affect coal production, is the recoverable portion of the DRB; EIA currently uses an estimate of 56 percent of the DRB, which equals 265