Assessing summertime urban air conditioning consumption in a semiarid environment

Abstract

Evaluation of built environment energy demand is necessary in light of global projections of urban expansion. Of particular concern are rapidly expanding urban areas in environments where consumption requirements for cooling are excessive. Here, we simulate urban air conditioning (AC) electric consumption for several extreme heat events during summertime over a semiarid metropolitan area with the Weather Research and Forecasting (WRF) model coupled to a multilayer building energy scheme. Observed total load values obtained from an electric utility company were split into two parts, one linked to meteorology (i.e., AC consumption) which was compared to WRF simulations, and another to human behavior. WRF-simulated non-dimensional AC consumption profiles compared favorably to diurnal observations in terms of both amplitude and timing. The hourly ratio of AC to total electricity consumption accounted for ∼53% of diurnally averaged total electric demand, ranging from ∼35% during early morning to ∼65% during evening hours. Our work highlights the importance of modeling AC electricity consumption and its role for the sustainable planning of future urban energy needs. Finally, the methodology presented in this article establishes a new energy consumption-modeling framework that can be applied to any urban environment where the use of AC systems is prevalent.

Citywide Impacts of Cool Roof and Rooftop Solar Photovoltaic Deployment on Near-Surface Air Temperature and Cooling Energy Demand

“…The BEP+BEM system is a building energy model (BEM; integrated into a multilayer building effect parametrization (BEP; Martilli et al 2002) that computes heat exchange between the buildings and the outdoor environment as well as the anthropogenic heating due to air-conditioning systems (Salamanca et al 2012b(Salamanca et al , 2015Martilli 2014;Chow et al 2014). The BEP+BEM system's ability to reproduce the observed diurnal cycle of near-surface variables (air temperature, wind speed, and wind direction) and citywide air-conditioning electricity consumption has been demonstrated on several occasions (specifically, during several recent extreme heat events including that analyzed here) for the Phoenix metropolitan area (Salamanca et al 2013. The excellent agreement obtained in these two previous studies provides confidence in assessing regional impacts of large-scale cool roof and rooftop solar photovoltaic deployment.…”

“…The same period has been extensively evaluated against observations for air temperature, wind speed, and wind direction for the Phoenix metropolitan area (Salamanca et al 2013, but now we further include the Tucson metropolitan area for the assessment of the model performance (see Sect. 3).…”

“…For the non-urban part, land-use categories were implemented using the MODIS satellite land-cover classification. Building morphological characteristics and thermal properties for roofs, roads, and vertical walls were obtained from Burian et al (2002) and Clarke et al (1991), and are detailed in Salamanca et al (2013Salamanca et al ( , 2014Salamanca et al ( , 2015. During the 10-day extreme heat period it was assumed that every building made use of air-conditioning systems and the resulting anthropogenic heat was rejected as sensible heat into the urban environment.…”

Environmental impacts of reflective materials: Is high albedo a ‘silver bullet’ for mitigating urban heat island?

“…Moreover, a study by Jacobson and Ten Hoeve [63] found that increasing worldwide roof albedo 8 would lead to local cooling but global warming, though highly uncertain, resulting from the magnified feedbacks at high latitudes over snow and sea ice. One main reason for the diversity in results is the turbulent mixing of mass and thermal energy in the lower atmosphere.…”

“…While a significant spatial and temporal variation is observed in the UHI intensity, many cities show a magnitude of 5-11 o C by mid-morning [4]. Elevated environmental temperatures in urban areas lead to rise of energy consumption for cooling [5][6][7][8], increase of peak electricity demand [9], degradation of air quality [10][11][12][13], and deterioration of thermal stress on residents [14,15]. In particular, UHI 6 temperature, if not negligible [21,53].…”