Center for Earth Systems Engineering and Management

Sonoma County, CA is on an ambitious pathway to meeting stringent carbon emissions goals that are part of California Assembly Bill 32. At the county-level, climate planners are currently evaluating options to assist residents of the county in reducing their carbon footprint and also for saving money. The Sonoma County Energy Independence Program (SCEIP) is one such county-level measure that is currently underway. SCEIP is a revolving loan fund that eligible residents may utilize to install distributed solar energy on their property. The fund operates like a property tax assessment, except that it only remains for a period of 20 years rather than in perpetuity.

This analysis intends to estimate the potential countywide effect that the $100M SCEIP fund might achieve on the C02 and cost footprint for the residential building energy sector. A functional unit of one typical home in the county is selected for a 25 year analysis period. Outside source data for the lifecycle emissions generated by the production, installation and operations of a PV system are utilized. Recent home energy survey data for the region is also utilized to predict a “typical” system size and profile that might be funded by the SCEIP program. A marginal cost-benefit calculation is employed to determine what size solar system a typical resident might purchase, which drives the life cycle assessment of the functional unit. Next, the total number of homes that might be financed by the SCEIP bond is determined in order to forecast the potential totalized effect on the County’s lifecycle emissions and cost profile.

The final results are evaluated and it is determined that the analysis is likely conservative in its estimation of the effects of the SCEIP program. This is due to the fact that currently offered subsidies are not utilized in the marginal benefit calculation for the solar system but do exist, the efficiency of solar technology is increasing, and the cost of a system over its lifecycle is currently decreasing. The final results show that financing distributed solar energy systems using Sonoma County money is a viable option for helping to meet state mandated goals and should be further pursued.

The Food-Energy-Water (FEW) nexus is the interaction and the interdependence of the food, energy and water systems. These interdependencies exist in all parts of the world yet little knowledge exists of the complexity within these interdependent systems. Using Arizona as a case study, systems-oriented frameworks are examined for their value in revealing the complexity of FEW nexus. Industrial Symbiosis, Life Cycle Assessment (LCA) and Urban Metabolism are examined. The Industrial Symbiosis presents the system as purely a technical one and looks only at technology and hard infrastructure.

The LCA framework takes a reductionist approach and tries to make the system manageable by setting boundary conditions. This allows the frameworks to analyze the soft infrastructure as well as the hard infrastructure. The LCA framework also helps determine potential impact. Urban Metabolism analyzes the interactions between the different infrastructures within the confines of the region and retains the complexity of the system. It is concluded that a combination of the frameworks may provide the most insight in revealing the complexity of nexus and guiding decision makers towards improving sustainability and resilience.

Mitigation of urban heat islands has become a goal for research and policy as urban environmental heat is a rapidly growing concern. Urban regions such as Phoenix, AZ are facing projected warming as urban populations grow and global climates warm (McCarthy et al. 2010), and severe urban heat can even lead to human mortality and morbidity (Berko et al. 2014). Increased urban heat may also have social and economic consequences such as by discouraging physical activity, reducing outdoor accessibility, and decreasing economic output (Stamatakis et al. 2013; Karner et al. 2015; Obradovich & Fowler 2017; Kjellstrom et al. 2009). Urban heat islands have been well documented in academic literature (Oke 1982; Arnfield 2003), and anthropogenic waste heat is often a major factor. The American Meteorological Society (2012) has said that anthropogenic waste heat may contribute “15 – 50 W/m2 to the local heat balance, and several hundred W/m2 in the center of large cities in cold climates and industrial areas.”

Anthropogenic waste heat from urban vehicle travel may be a notable contributor to the urban heat balance and the urban heat island effect, but little research has quantified and explored how changes in vehicle travel may influence local climates. Even with recent rapid improvements to engine efficiencies, modern automobiles still convert small amounts of fuel to useful energy. Typically, around two-thirds of energy from fuel in internal combustion engine vehicles is lost as waste heat through exhaust and coolant (Hsiao et al. 2010; Yu & Chau 2009; Saidur et al. 2009; Endo et al. 2007), and as much as 80% of fuel energy can be lost to waste heat under poor conditions (Orr et al. 2016). In addition, combustion of fuel generates water vapor and air pollution which may also affect the urban climate. Figure 1 displays where a typical combustion engine’s fuel energy is used and lost. There has been little research that quantifies the influence of vehicle travel on urban anthropogenic waste heat. According to Sailor and Lu (2004), most cities have peak anthropogenic waste heat values between 30 and 60 W m-2 (averaged across city) and heating from vehicles could make up as much as 62% of the total in summer months. Additionally, they found that vehicle waste heat could account for up to 300 W m-2 during rush hours over freeways. In another study, Hart & Sailor (2009) used in situ measurements in Portland, OR to evaluate spatial variability of air temperatures on urban roadways. They found that air masses near major roadways are some of the warmest in the region. Although some of the warming is attributed to pavement characteristics (imperviousness, low albedo), an average increase of 1.3 C was observed on weekdays relative to weekends along roadways. The authors offer increased weekday traffic density and building use as the likely contributors to this discrepancy. These previous studies indicates that vehicle related waste heat could be an important consideration in the urban energy balance. If significant, there may exist viable strategies to reduce anthropogenic waste heat from urban vehicle travel by increasing the fleet fuel economy and shifting to electric vehicles. This could offer cooling in urban areas around roadways were pedestrians are often found. Figure 2 visually demonstrates waste heat from vehicles (including an electric vehicle) in two thermal images.