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

Abstract

Assessment of mitigation strategies that combat global warming, urban heat islands (UHIs), and urban energy demand can be crucial for urban planners and energy providers, especially for hot, semi-arid urban environments where summertime cooling demands are excessive. Within this context, summertime regional impacts of cool roof and rooftop solar photovoltaic deployment on near-surface air temperature and cooling energy demand are examined for the two major USA cities of Arizona: Phoenix and Tucson. A detailed physics-based parametrization of solar photovoltaic panels is developed and implemented in a multilayer building energy model that is fully coupled to the Weather Research and Forecasting mesoscale numerical model. We conduct a suite of sensitivity experiments (with different coverage rates of cool roof and rooftop solar photovoltaic deployment) for a 10-day clear-sky extreme heat period over the Phoenix and Tucson metropolitan areas at high spatial resolution (1-km horizontal grid spacing). Results show that deployment of cool roofs and rooftop solar photovoltaic panels reduce near-surface air temperature across the diurnal cycle and decrease daily citywide cooling energy demand. During the day, cool roofs are more effective at cooling than rooftop solar photovoltaic systems, but during the night, solar panels are more efficient at reducing the UHI effect. For the maximum coverage rate deployment, cool roofs reduced daily citywide cooling energy demand by 13-14 %, while rooftop solar photovoltaic panels by 8-11 % (without considering the additional savings derived from their electricity production). The results presented here demonstrate that deployment of both roofing technologies have multiple benefits for the urban environment, while solar photovoltaic panels add additional value because they reduce the dependence on fossil fuel consumption for electricity generation. Keywords

A wedge strategy for mitigation of urban warming in future climate scenarios

“…In addition, this linear supposition seems to be a robust property for the air UHI as well. We will present evidence from published UHI mitigation studies using the air UHI (Taha et al, 1997;Georgescu et al, 2014;Stone et al, 2014;Salamanca et al, 2016).…”

“…Conversion of roof space to solar photovoltaics (PVs) can also cool the urban air (Hu et al, 2016;Salamanca et al, 2016). A typical solar PV has an albedo of 0.10 and a futuristic electricity conversion efficiency of 25 % (Hu et al, 2016), giving a heat removal rate equivalent to having a surface albedo of 0.33, which is 0.04 more than the average default roof albedo value.…”

“…A majority of the modeling studies deploy a mesoscale weather forecast model, such as the Weather Research Forecasting Model (WRF; Skamarock et al, 2008), and model simulations are performed for a business-as-usual case and for one or more mitigation strategies, including tree planting (Stone et al, 2013(Stone et al, , 2014, green roof (Li et al, 2014;Stone et al, 2014), cool roof (Georgescu et al, 2014), and rooftop solar panels (Salamanca et al, 2016).…”

Anthropogenic meso-meteorological feedbacks: a review of recent research

“…Модели, настроенные на поддержание климатических условий внутри помещений, могут включать учет и других антропогенных обратных связей, например, холодных крыш (с увеличенным альбедо) и солнечных панелей [61,127].…”

Climate change and growing megacities: hazards and vulnerability

“…Comparison with observational data has demonstrated that the physics-based modelling system is an effective tool for assessing (indoor) urban cooling requirements, which involves evaluating electricity consumption for different urban growth patterns and under extreme summertime weather conditions. These studies will be crucial for the development of reliable projections on future cooling needs and environmental consequences of rapidly urbanising regions under various climate scenarios (Bartos and Chester, 2015;Georgescu et al, 2012Georgescu et al, , 2014) that strategically incorporate adaptation and mitigation strategies alleviating energy demand Salamanca et al, 2016).…”