Energy Savings of Heat-Island Reduction Strategies in Chicago and Houston (Including Updates for Baton Rouge, Sacramento, and Salt Lake City)

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Journal Article

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Initiative” to quantify the potential benefits of Heat-Island Reduction (HIR) strategies (i.e.,
shade trees, reflective roofs, reflective pavements and urban vegetation) to reduce coolingenergy
use in buildings, lower the ambient air temperature and improve urban air quality in
cities, and reduce CO2 emissions from power plants. Under this initiative, the Urban Heat Island
Pilot Project (UHIPP) was created with the objective of investigating the potential of HIR strategies
in residential and commercial buildings in three initial UHIPP cities: Baton Rouge, LA; Sacramento,
CA; and Salt Lake City, UT. Later two other cities, Chicago, IL and Houston, TX were
added to the UHIPP.
In an earlier report we summarized our efforts to calculate the annual energy savings, peak
power avoidance, and annual CO2 reduction obtainable from the introduction of HIR strategies in
the initial three cities. This report summarizes the results of our study for Chicago and Houston.
In this analysis, we focused on three building types that offer the highest potential savings:
single-family residence, office and retail store. Each building type was characterized in detail by
vintage and system type (i.e., old and new building constructions, and gas and electric heat). We
used the prototypical building characteristics developed earlier for each building type and
simulated the impact of HIR strategies on building cooling- and heating-energy use and peak
power demand using the DOE-2.1E model. Our simulations included the impact of (1)
strategically-placed shade trees near buildings [direct effect], (2) use of high-albedo roofing
material on the building [direct effect], (3) urban reforestation with high-albedo pavements and
building surfaces [indirect effect] and (4) combined strategies 1, 2, and 3 [direct and indirect
effects]. We then estimated the total roof area of air-conditioned buildings in each city using
readily obtainable data to calculate the metropolitan-wide impact of HIR strategies.
The results show that in Chicago, potential annual energy savings of $30M could be
realized by ratepayers from the combined direct and indirect effects of HIR strategies.
Additionally, peak power avoidance is estimated at 400 MW and the reduction in annual carbon
emissions at 58 ktC. In Houston, the potential annual energy savings are estimated at $82M, with
an avoidance of 730 MW in peak power and a reduction in annual carbon emissions of 170 ktC.

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