Environ. Res. Lett. 6 (July-September 2011) 034001
doi:10.1088/1748-9326/6/3/034001
Regional climate consequences of large-scale cool roof and photovoltaic array deployment
Dev Millstein and Surabi Menon
Lawrence Berkeley National Laboratory Berkeley CA USA
E-mail: dmillstein@lbl.gov
Abstract. Modifications to the surface albedo through the deployment of cool roofs and pavements (reflective materials) and photovoltaic arrays (low reflection) have the potential to change radiative forcing surface temperatures and regional weather patterns. In this work we investigate the regional climate and radiative effects of modifying surface albedo to mimic massive deployment of cool surfaces (roofs and pavements) and separately photovoltaic arrays across the United States. We use a fully coupled regional climate model the Weather Research and Forecasting (WRF) model to investigate feedbacks between surface albedo changes surface temperature precipitation and average cloud cover. With the adoption of cool roofs and pavements domain-wide annual average outgoing radiation increased by 0.16 ± 0.03 W m – 2 (mean ± 95% C.I.) and afternoon summertime temperature in urban locations was reduced by 0.11–0.53 °C although some urban areas showed no statistically significant temperature changes. In response to increased urban albedo some rural locations showed summer afternoon temperature increases of up to + 0.27 °C and these regions were correlated with less cloud cover and lower precipitation. The emissions offset obtained by this increase in outgoing radiation is calculated to be 3.3 ± 0.5 Gt CO2 (mean ± 95% C.I.). The hypothetical solar arrays were designed to be able to produce one terawatt of peak energy and were located in the Mojave Desert of California. To simulate the arrays the desert surface albedo was darkened causing local afternoon temperature increases of up to + 0.4 °C. Due to the solar arrays local and regional wind patterns within a 300 km radius were affected. Statistically significant but lower magnitude changes to temperature and radiation could be seen across the domain due to the introduction of the solar arrays. The addition of photovoltaic arrays caused no significant change to summertime outgoing radiation when averaged over the full domain as interannual variation across the continent obscured more consistent local forcing.
Keywords: photovoltaics cool roofs CO2 offsets radiative forcing urban environment
Contents
1. Introduction
2. Methods
2.1. Model details
2.2. Scenarios
2.3. Model evaluation
3. Results and discussion
3.1. Cool surfaces: urban brightening
3.2. Hot surfaces: desert PV
3.3. CO2 offsets from radiative forcing
3.4. Impact of low albedo desert PV
4. Conclusions
Acknowledgments
References