Energy savings for heat-island reduction strategies in Chicago and Houston (including updates for Baton Rouge, Sacramento, and Salt Lake City)

Abstract

In 1997, the U.S. Environmental Protection Agency (EPA) established the "Heat Island Reduction 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 CO 2 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 CO 2 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. Executive SummaryIn 1997, the U.S. Environmental Protection Agency (EPA) embarked on an initiative to quantify the potential benefits of Heat-Island Reduction (HIR) strategies (i.e., shade trees, reflective roofs, reflective pavements and urban vegetation). The goals were to reduce cooling-energy use in buildings, lower the ambient air temperature, reduce CO 2 emissions from power plants, and improve air quality in urban areas. Under this initiative, entitled "The Heat Island Reduction Initiative," the EPA...

Economic comparison of white, green, and black flat roofs in the United States

“…However, because there is no standard protocol for quantifying these urban heat island-related externalities, comparisons among these three roofing strategies are limited. To date there have been a number of published case studies that compare green roofs to black roofs [9][10][11][12][13] and white roofs to black roofs [14][15][16][17]. However, we could not find a comprehensive comparison of green and white roofs.…”

“…The purely economic 50-year net savings of $25/m 2 ($2.40/ft 2 ) in favor of white roofs, though only $1/m 2 -year when annualized, is likely to underestimate of the true societal advantages of white roofs-namely, dark roofs pose a public health threat by exacerbating urban heat islands. We 16 See the Global Cool Cities Alliance's Cool Roofs and Pavements Toolkit (http://coolrooftoolkit.org) for a complete list of U.S. cool roof building codes and standards. 17 These net primary energy and cost savings differ from, but are based on, those reported in Table 1 …”

Economic benefits for green roofs: a case study of the skaggs pharmacy building, university of utah

“…Sacramento, CA; Salt Lake City, UT; Chicago, IL; Houston, TX), Konopacki and Akbari at LBNL identifi ed an average 3.94% savings on building cooling energy consumption by applying high-albedo roof material to offi ce buildings metropolitan-wide [33].…”

Development of an operational modeling system for urban heat islands: an application to Athens, Greece

“…It is a phenomenon that is significant in itself since it occurs in the layer of the atmosphere where almost all daily human activities take place. Research has shown that heat islands have considerable implications for air quality (Rosenfeld et al, 1998;Sarrat et al, 2006;Davies et al, 2007), energy demand for cooling purposes (Santamouris et al, 2001;Konopacki and Akbari, 2002), human health (Conti et al, 2005;Haines et al, 2006), and regional/local atmospheric circulations (Lin et al, 2008;Miao et al, 2009). Further, although the UHI in itself does not influence global temperatures (Houghton et al, 2001), it does have an effect on local temperatures used for assessing climate change (Van Wevenberg et al, 2008).…”