Energy and
Environmental
Policy
District Cooling,
Carbon and LEED®
Mark Spurr, IDEA Legislative Director
Earlier this year, I addressed the key
role that district energy can play in
achieving carbon reductions cost-effectively (Third Quarter 2008, District
Energy). In that column, the economics of
carbon reduction were quantified in terms
of the cost per unit of electricity produced,
with district energy providing a means of
achieving ‘right-sized’ combined heat and
power. This column focuses on district
cooling and examines the nexus of three
trends: strong worldwide growth in district
cooling, particularly in the Middle East;
economic valuation of carbon dioxide (CO2)
emission reductions; and increasing interest
by real estate developers in meeting green
building certifications.
Wide Variety in
District Cooling
It is difficult to generalize about the
carbon impacts of district cooling because
there are many case-specific variables,
including
district cooling technology used,
conventional building cooling system
that would otherwise be used and
characteristics of the power generation,
transmission and distribution grid.
To demonstrate the breadth of this
range, four examples were chosen to
illustrate the carbon reduction potential
of district cooling. Key assumptions are
shown in table 1.
Scenarios 1 and 2 represent potential
North American or European conditions,
with district cooling competing with build-ing-scale water-cooled electric centrifugal
chillers. In Scenario 1 we assume that all
power for either district cooling or build-ing-scale chillers comes from new natural
gas combined-cycle power plants. Scenario 2
illustrates the impact if power instead comes
from new pulverized coal power plants.
(Despite higher CO2 emissions with coal,
long-term natural gas supply constraints
may result in coal continuing to have a
share of new generation capacity.)
Scenarios 3 and 4 illustrate potential
Middle East conditions, with district cooling
competing with air-cooled chillers due
to severe water constraints in the region.
(District cooling systems are far better able
to use alternative water sources, such as
treated sewage effluent, untreated seawater
or treated seawater.) Grid power is assumed
to come from new natural gas combined-cycle power plants. Scenario 3 depicts a
typical electric centrifugal district cooling
system. In Scenario 4 it is assumed that
gas engine-driven chillers provide half of
the district cooling capacity and 80 percent
of the annual energy.
Value of District Cooling
Carbon Reductions
The results of the analysis, summarized in table 2, show that district cooling
can provide reductions of 14 percent to
45 percent in CO2 emissions compared
with conventional building cooling systems.
The economic value of CO2 reductions
is potentially significant in a competitive
energy market, with reductions ranging
up to $0.016 or $0.031 per ton-hour at
CO2 values of $50 or $100 per metric
ton, respectively.
District cooling can provide
reductions of 14 percent to
45 percent in CO2 emissions
compared with conventional
building cooling systems.
Although an effective international
treaty to reduce CO2 and other greenhouse gas emissions is most likely several
years away, I believe that the push to reduce
greenhouse gas emissions is inexorable.
Consequently, economic valuation of
greenhouse gas emissions should be a key
part of energy planning at all levels,
including national energy policy, company
strategic planning and options analysis for
energy facilities.
LEED®
The Leadership in Energy and Environmental Design (LEED®) Green Building
