Environmental Engineering Reference
In-Depth Information
The working fluid in a Rankine cycle follows a closed loop and is reused
constantly. The water vapour and entrained droplets often seen billowing
from power stations are generated by the cooling systems (not from the
closed loop Rankine power cycle) and represent the waste heat that could
not be converted to useful work. Note that cooling towers operate using the
latent heat of vapourisation of the cooling fluid. The white billowing clouds
that form in cooling tower operation are the result of water droplets that are
entrained in the cooling tower airflow; they are not, as commonly thought,
steam. Although many substances could be used in the Rankine cycle, water
is usually the fluid of choice due to its favourable properties, such as non-
toxicity and non-reactive chemistry, abundance and low cost, as well as its
thermodynamic properties.
5.1.4.2 Gas Cycles
One of the principal advantages the Gas cycles have over other cycles is that
during the compression stage relatively little work is required to drive the
pump due to the working fluid being in its liquid phase at this point. By
condensing the fluid to liquid, the work required by the pump will only
consume approximately 1%-3% of the turbine power and so give a much
higher efficiency for a real cycle. The benefit of this is lost somewhat due to
the lower heat addition temperature. Gas turbines, for instance, have turbine
entry temperatures approaching 1500°C. Nonetheless, the efficiencies of
steam cycles and gas turbines are fairly well matched.
5.2 Strategic Urban Planning Programme:
Lacking Energy Component
Strategic planning is a technique that has been applied to many facets of
human activity; the application of strategic planning in urban contexts—in
cities, regions and other metropolitan areas—is a relatively recent develop-
ment. Its beginnings were eminently practical and artistical: a mixture of
thought, techniques and art or expertise.
Fifteen years of practice proved to be enough time for the technique to
spread and for the first 'Meeting of American and European Cities for the
Exchange of Experiences in Strategic Planning' to be organised. Institutions
sponsoring the meeting, held in Barcelona in 1993, included the Inter-
American Development Bank, the European Community Commission and
the Iberoamerican Cooperation Institute. The cities of Amsterdam, Lisbon,
Lille, Barcelona, Toronto and Santiago de Chile participated, among others.
At that meeting, it was demonstrated—along with other relevant aspects—
that if cooperative processes are used in large cities in order to carry out
