Page 283 - Handbook of Energy Engineering Calculations
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are parties of interest in the harnessing of hydro sites, and stringent
government regulations prevail, including those of the U.S. Corps of
Engineers, Federal Power Commission, Bureau of Reclamation, Geological
Survey, and Securities and Exchange Commission.
5. Assess ways that the selected capacity can be used to serve customers
Prime capacity is that which is continuously available. Firm capacity is much
larger and is dependent upon interconnection with other power plants and the
extent to which load curves permit variable-capacity operation. The
incremental cost for additional turbine-generator capacity is small, so that
many alternatives for economic development of a site must be considered.
The alternatives include a wide variety of base load, peak load, run-of-river,
and pumped-storage plants. All are concerned with fitting installed capacity,
runoff, and storage to the load curve of the power system and to give
minimum cost over the life of the installation. In this evaluation it is essential
clearly to distinguish capacity (kW) from energy (kWh) as they are not
interchangeable. In any practical evaluation of water power in this electrical
era, it should be recognized that the most favorable economics will be found
with an interconnected electric system where the different methods of
generating power are complementary as well as competitive.
As noted above, there is an increasing tendency in many areas to allocate
hydro capacity to peaking service and to foster pumped-water storage for the
same objective. Pumped storage, to be practical, requires the use of two
reservoirs for the storage of water—one at considerably higher elevation, say,
500 to 1000 ft (150 to 300 m). A reversible pump-turbine operates
alternatively (1) to raise water from the lower to the upper reservoir during
off-peak periods, and (2) to generate power during peak-load periods by
letting the water flow in the opposite direction through the turbine. Proximity
of favorable sites on an interconnected electrical transmission system reduces
the investment burden. Under such circumstances the return of 2 kWh on-
peak for 3 kWh pumping off-peak has been demonstrated to be an attractive
method of economically utilizing interconnected fossil-fuel, nuclear-fuel, and
hydro-power plants.
Related Calculations. The procedures and considerations given here apply to
hydroelectric installations anywhere in the world. Since each hydro site is