Page 39 - Sustainable Cities and Communities Design Handbook

16 Sustainable Cities and Communities Design Handbook

wind, the force of the wind turns it, a gear coupling interacts with a turbine,
and electricity is generated and captured. While ancient in form, there have
been significant technological advances. The new generation of wind turbines
is stronger, more efficient, quieter, and less expensive. Today, wind turbines
are being installed in small communities and even smaller systems on rooftops
as part of the natural flow of air over buildings.
Solar generation systems capture sunlight including ultraviolet radiation
via solar cells (silicon). This process of passing sunlight through silicon creates
a chemical reaction that generates a small amount of electricity. This process is
described as a photovoltaic or PV reaction and is at the core of solar panel
systems. A second process uses sunlight to heat liquid (oil or water), which is
then converted to electricity. A number of communities are now looking into
more and more solar “concentrated” systems where the sun is captured in heat
tubes and used for heating and cooling. This is a great renewable technology for
use in water systems and buildings that have swimming pools.
Biomass is a remarkable chemical process that converts plant sugars (like
corn) into gases (ethanol or methane), which are then burned or used to
generate electricity. The process is referred to as “digestive” and it’s not unlike
an animal’s digestive system. The ever-appealing feature of this process is that
it can use abundant and seemingly unusable plant debris, such as rye grass,
wood chips, weeds, grape sludge, almond hulls, etc.
Geothermal is power extracted from heat stored in the earth, which
originates from the formation of the planet, from radioactive decay of
minerals, and from solar energy absorbed at the surface. It has been used for
space heating and bathing since ancient Roman times, but is now better known
for generating electricity. Worldwide, geothermal plants have the capacity to
generate about 10 GW as of 2007, and in practice generates 0.3% of global
electricity demand. In the last few years, engineers have developed several
remarkable devices called geothermal heat pumps, ground source heat pumps,
and geoexchangers that gather ground heat to provide heating for buildings
in cold climates. Through a similar process they can use ground sources
for building cooling in hot climates. More and more communities with
concentrations of buildings, like colleges, government centers, and shopping
malls are turning to geothermal systems.
Ocean and tidal waves generate power, the use of which was been pioneered
by the French and the Irish with their revolutionary SeaGen tidal power system.
The French have been generating power from the tides since 1966, and now
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Electricite ´ de France has announced a large commercial-scale tidal power system
that will be enough to generate 10 MW per year. America, particularly the Pacific
coastline, is equally capable of producing massive amounts of energy with the

right technology. Ocean power technologies vary, but the primary types are: wave
power conversion devices, which bob up and down with passing swells; tidal
powerdevices,which use strongtidal variations toproduce power;ocean current
devices, which look like wind turbines and are placed below the water surface to