Economic Design

A proposed pumped storage project for peaking service must be able to show a liberal margin of economic superiority over competing thermal types. This requires that the undertaking be designed in accordance with the so-called lean project concept, in which all elements are closely tailored to the specific purpose of pumped storage and many features considered standard in the conventional hydroelectric plant are found superfluous.

Selection of the proper site is of paramount importance. The rock should be strong and tight so no more than local grouting is needed to inhibit leakage and no drainage system for the concrete lining of the tunnels is required. The upper storage reservoir should preferably be located in a natural basin in elevated highlands to provide the requisite storage capacity by use of low rimdikes. It is a great advantage if the lower reservoir can be located on tidewater. The head, probably the most important natural feature, should be high, in the range from 500 to 1500 ft (152 to 457 m). High head means smaller water quantities and consequently smaller sizes for a given power output. High head also permits higher turbine speeds, lower torque, and a smaller generator. The intake need be only a bell mouth at the end of the supply tunnel; consequently, headgates, cranes, and accessories can be eliminated. The individual units should be of large capacity to ensure minimum equipment costs.

Table 3 shows a typical form for the economic comparison of pumped storage and competitive thermal peaking, and Table 4 is a typical form for the project cost estimate with its overheads.

Table 5 shows the range of machine requirements for a deep upper reservoir in which the head variation due to daily drawdown is relatively large. Note that the maximum electric motor load to develop the full hydraulic capability of the pump, occurring at the minimum head of 970 ft (296 m), is 297 MVA. However, this loading is of comparatively short duration and may be sustained at 80°C temperature rise, which corresponds to 115% of normal rating. The normal rating at 60°C temperature rise would then be ffg, or 258 MVA,

TABLE 2 Arithmetic integration at full-load rejection (generating mode; wicket gates at 92% opening)
Survival Treasure

Survival Treasure

This is a collection of 3 guides all about survival. Within this collection you find the following titles: Outdoor Survival Skills, Survival Basics and The Wilderness Survival Guide.

Get My Free Ebook


Post a comment