A stochastic optimization approach to reduce greenhouse gas emissions from buildings and transportation Ebrahim Karan a, * , Somayeh Asadi b , Lewis Ntaimo c a Department of Applied Engineering, Safety, and Technology, Millersville University, Osburn Hall, PO Box 1002, 40 East Frederick Street, Millersville, PA 17551, USA b Department of Architectural Engineering, Pennsylvania State University,104 Engineering Unit A, University Park, PA 16802, USA c Department of Industrial and Systems Engineering, Texas A&M University, 3131 TAMU, College Station, TX 77843, USA article info Article history: Received 14 November 2015 Received in revised form 23 February 2016 Accepted 16 March 2016 Keywords: CO 2 emissions Mitigation strategy Electric vehicle Solar energy Buildings Transportation abstract The magnitude of building- and transportation-related GHG (greenhouse gas) emissions makes the adoption of all-EVs (electric vehicles) powered with renewable power as one of the most effective strategies to reduce emission of GHGs. This paper formulates the problem of GHG mitigation strategy under uncertain conditions and optimizes the strategies in which EVs are powered by solar energy. Under a pre-specified budget, the objective is to determine the type of EV and power generation capacity of the solar system in such a way as to maximize GHG emissions reductions. The model supports the three primary solar systems: off-grid, grid-tied, and hybrid. First, a stochastic optimization model using probability distributions of stochastic variables and EV and solar system specifications is developed. The model is then validated by comparing the estimated values of the optimal strategies and actual values. It is found that the mitigation strategies in which EVs are powered by a hybrid solar system lead to the best cost-expected reduction of CO 2 emissions ratio. The results show an accuracy of about 4% for mitigation strategies in which EVs are powered by a grid-tied or hybrid solar system and 11% when applied to estimate the CO 2 emissions reductions of an off-grid system. Published by Elsevier Ltd. 1. Introduction To help break down the complex subject matter of climate change, many researchers examined the links between human activities and climate change [2,31,38]. The examination of the literature facilitates an understanding of how GHGs (greenhouse gases) emissions contribute to global warming and what are nat- ural and human sources of GHG emissions. This, in turn, translates to the development and implementation of GHG mitigation stra- tegies. The burning of fossil fuels to generate electricity or drive cars has undoubtedly released carbon dioxide (CO 2 ) and other heat- trapping GHG emissions into the atmosphere and thus increased the concentration of atmospheric CO 2 emissions [24]. The main human activities that emit CO 2 emissions are (1) the combustion of fossil fuels to generate electricity, accounting for about 37% of total U.S. CO 2 emissions and 31% of total U.S. GHG emissions in 2013; (2) the combustion of fossil fuels such as gasoline and diesel to transport people and goods, accounting for about 31% of total U.S. CO 2 emissions and 26% of total U.S. GHG emissions in 2013; and (3) industrial processes such as the production and consumption of minerals and chemicals, accounting for about 15% of total U.S. CO 2 emissions and 12% of total U.S. GHG emissions in 2013 [6]. To make informed decisions, policy makers need to be familiar with a wide variety of carbon reducing technologies, GHG emission mitigation inventories and potential costs and benefits of specific GHG mitigation strategies. When looking at the GHGs that are associated with electricity generation and transportation, the adoption of hybrid and all-EVs (electric vehicles) instead of con- ventional gasoline powered vehicles with renewable source of power presents the most effective GHG emissions mitigation strategy [8]. This strategy not only saves considerable amounts of transportation-related CO 2 emissions [10], but also reduces the demand for electricity in buildings, which is mainly supplied by coal-fired generation. Because many factors that affect the success or scale of GHG emissions reductions are uncertain and complex, mitigation strategies are having difficulty delivering the desired outcome sought by policy makers. Thus, urban community * Corresponding author. E-mail addresses: Ebrahim.karan@millersville.edu (E. Karan), asadi@engr.psu. edu (S. Asadi), ntaimo@tamu.edu (L. Ntaimo). Contents lists available at ScienceDirect Energy journal homepage: www.elsevier.com/locate/energy http://dx.doi.org/10.1016/j.energy.2016.03.076 0360-5442/Published by Elsevier Ltd. Energy 106 (2016) 367e377