Part of the Solution to Reducing
Global Greenhouse Gas Emissions
is Urban Heat Island Management
Energy Management,
Emission Reductions
and
Global Warming
The Department of Energy estimates that a nationwide
UHI program could reduce annual carbon dioxide emissions by 45
million tons. Global Environmental Management,
Inc., employs advanced space technology for targeting urban features
that affect emissions, energy efficiency and air quality. Central
to this solution is the reduction of global greenhouse gases.
Electric utility companies can profit from
GEM's program, which increases an electric utility's competitive
edge in the search for more efficient methods of providing power
to larger customer bases at less cost. GEM provides unique products
and processes for maximizing the cost effectiveness of a citywide
Demand Side Management program aimed at freeing up existing energy
for alternative uses without new production costs or emissions.
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Temperature data derived
from satellite imagery is overlaid on a detailed base map of
Washington D.C. produced from aerial imagery. The colors of red,
yellow, purple and light blue illustrate temperature variations
over the hottest surface areas. Cool areas such as the grass
and trees in the Mall area appear in more natural color. The
Potomac River cuts across the lower left portion of the image.
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Cities expand, and manmade urban structures
replace natural land cover. Solar radiation heats the dark paved
surfaces and rooftops. The increased surface temperatures raise
ambient air temperatures. The increased surface and air temperatures
cause an increased demand on energy for cooling.
The increased generating capacity for cooling
energy involves significant increases in peak load production,
including greenhouse gas emissions. UHI mitigation reduces the
cooling energy demand and eliminates the emissions.
Further, emissions from the increased energy
production for cooling contributes to urban air pollution. Elevated
urban temperatures catalyze the formation of smog more rapidly.
These conditions result in increased illness and health care
costs. By lowering temperatures UHI mitigation reduces energy
production requirements and subsequent emissions and also slows
the formation of smog.
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According to the US Department of Energy one
sixth of the electricity consumed in the United States goes to
cooling buildings at an annual power cost of forty billion dollars.
Mitigation strategies for the reduction of urban temperatures
could save five to ten billion dollars in energy costs annually.
Reductions in ozone and smog could save another five billion dollars
in medical costs and lost work.
In Los Angeles, alone, the need for air conditioning
could be lowered by 30%, or 1.74 billion kilowatt-hours, saving
more than 170 million dollars per year in energy load reductions.
The need for peak capacity could be lowered by 1,500 Megawatts;
equivalent to two or three large power plants.
On top of the energy savings another 360 million
dollars could be saved in health care costs as a result of the
smog reduction. This brings the total savings in L.A. to more
than 1/2 Billion dollars annually.
Within the urban setting some places are, of course, hotter than others. These
sites should be identified and targeted for cooling in order of
priority. Site identification can be precisely established using
remotely sensed imagery with color enhancement, showing various
heat levels ranging from hot reds to cooler blues. Priority of
sites is determined by cross-referencing in a GIS pertinent information
such as land-cover type, surface temperature, albedo (reflectivity),
energy demand data, ownership, zoning, relationship to surrounding
surfaces, slope, aspect, and solar exposure.
Urban land-cover information is produced from remotely sensed imagery. The image
data is used to separate urban land-cover into classes for emissivity,
albedo and vegetative index. Surface temperatures are derived
from remotely sensed thermal data using a formula that combines
the brightness-temperature measured at the sensor, the surface
material's emissivity, and the atmospheric conditions. The multiple
remote sensing data sets are added to the local information within
the GIS where site prioritization occurs.
Once identified and prioritized, correcting overheated surfaces can be accomplished
at considerably less cost than the consequent expenses in energy
production and health care resulting from unrestrained thermal
conditions. GEM provides services to identify optimal land-cover
change for moderating urban temperatures. New Energy Star rated
roofing materials, cooler pavement composition, and increased
vegetation, along with urban designs incorporating greenways and
forested areas will mitigate urban temperature extremes. Cities
will become more comfortable to live in and their environments
more sustainable while increasing energy efficiency and economic
development.
