Page 274 - Handbook of Energy Engineering Calculations

to minimize remaining energy after the water exists from the runner blades.
Other improvements being sought for pumps are: (1) modifying the runner-
blade profiles or using a turbine runner in a pump casing, (2) adding flow-
control devices such as wicket gates to a standard pump design or stay vanes
to adjust turbine output.

Many components of hydroturbines are being improved to reduce space
requirements and civil costs, and to simplify design, operation, and
maintenance. Cast parts used in older turbines have largely been replaced by

fabricated components. Stainless steel is commonly recommended for guide
vanes, runners, and draft-tube inlets because of better resistance to cavitation,
erosion, and corrosion. In special cases, there are economic tradeoffs between
using carbon steel with a suitable coating material and using stainless steel.
Some engineers are experimenting with plastics, but much more long-term

experience is needed before most designers will feel comfortable with
plastics. Further, stainless steel material costs are relatively low compared to
labor costs. And stainless steel has proven most cost-effective for hydro-

turbine applications.
While hydro power does provide pollution-free energy, it can be subject to
the vagaries of the weather and climatic conditions. Thus, at the time of this
writing, some 30 hydroelectric stations in the northwestern part of the United
States had to cut their electrical output because the combination of a severe

drought and prolonged cold weather forced a reduction in water flow to the
stations. Purchase of replacement power—usually from fossil-fuel-fired
plants—may be necessary when such cutbacks occur. Thus, the choice of

hydro power must be carefully considered before a final decision is made.
This procedure is based on the work of Jason Makansi, associate editor,
Power magazine, and reported in that publication.

ECONOMIC EVALUATION OF SMALL-SCALE HYDRO

SITES

A city is considering a small hydro-power installation to save fossil fuel. To

obtain the savings, the following steps will be taken: refurbish an existing
dam, install new turbines, operate the generating plant. Outline the
considerations a designer must weigh before undertaking the actual