Contribution of Offshore Wind to the Power Grid: U.S. Air Quality Implications.

Offshore wind is an established technology in Europe and Asia, but it has not yet gained market share in the United States. There is, however, increasing interest in offshore wind development in many coastal regions of the United States. As offshore wind grows in those regions it will displace existing and future electric generation assets, which will lead to changes in the emissions from the electric power sector. This research explores combinations of two electric sector drivers, offshore wind capital costs and carbon dioxide (CO2) caps, to measure the changes in the energy mix and quantify offshore wind's impact on electric sector emissions. An energy system modeling approach is applied, using a nested parametric sensitivity analysis, to generate and explore potential energy futures and analyze the air quality and greenhouse gas emissions benefits of offshore wind as an energy source. The analysis shows that offshore wind capacity was added due to cost reductions more than CO2 cap stringency, though both increased capacity additions. Capacity varied more by CO2 cap stringency at higher prices and less at lower prices. CO2 mitigation led to reductions in all five emissions investigated, regardless of offshore wind cost. Offshore wind-specific reductions were only consistent across all CO2 caps for CO2 and methane (CH4), though offshore wind-specific reductions were found for all emissions in the absence of CO2 caps. Results are presented nationally, analyzing the differences in adoption of offshore wind and how this technology provides a broader range of emission reduction options for the power sector.

Evolution of the United States Energy System and Related Emissions under Varying Social and Technological Development Paradigms: Plausible Scenarios for Use in Robust Decision Making.

The energy system is the primary source of air pollution. Thus, evolution of the energy system into the future will affect society's ability to maintain air quality. Anticipating this evolution is difficult because of inherent uncertainty in predicting future energy demand, fuel use, and technology adoption. We apply scenario planning to address this uncertainty, developing four very different visions of the future. Stakeholder engagement suggested that technological progress and social attitudes toward the environment are critical and uncertain factors for determining future emissions. Combining transformative and static assumptions about these factors yields a matrix of four scenarios that encompass a wide range of outcomes. We implement these scenarios in the U.S. Environmental Protection Agency MARKet ALlocation (MARKAL) model. Results suggest that both shifting attitudes and technology transformation may lead to emission reductions relative to the present, even without additional policies. Emission caps, such as the Cross-State Air-Pollution Rule, are most effective at protecting against future emission increases. An important outcome of this work is the scenario-implementation approach, which uses technology-specific discount rates to encourage scenario-specific technology and fuel choices. End-use energy demands are modified to approximate societal changes. This implementation allows the model to respond to perturbations in manners consistent with each scenario.

Effects of recent energy system changes on CO2 projections for the United States.

Recent projections of future United States carbon dioxide (CO2) emissions are considerably lower than projections made just a decade ago. A myriad of factors have contributed to lower forecasts, including reductions in end-use energy service demands, improvements in energy efficiency, and technological innovations. Policies that have encouraged these changes include renewable portfolio standards, corporate vehicle efficiency standards, smart growth initiatives, revisions to building codes, and air and climate regulations. Understanding the effects of these and other factors can be advantageous as society evaluates opportunities for achieving additional CO2 reductions. Energy system models provide a means to develop such insights. In this analysis, the MARKet ALlocation (MARKAL) model was applied to estimate the relative effects of various energy system changes that have happened since the year 2005 on CO2 projections for the year 2025. The results indicate that transformations in the transportation and buildings sectors have played major roles in lowering projections. Particularly influential changes include improved vehicle efficiencies, reductions in projected travel demand, reductions in miscellaneous commercial electricity loads, and higher efficiency lighting. Electric sector changes have also contributed significantly to the lowered forecasts, driven by demand reductions, renewable portfolio standards, and air quality regulations.

Analysis of alternative pathways for reducing nitrogen oxide emissions.

UNLABELLED: Strategies for reducing tropospheric ozone (O3) typically include modifying combustion processes to reduce the formation of nitrogen oxides (NOx) and applying control devices that remove NOx from the exhaust gases of power plants, industrial sources and vehicles. For portions of the U.S., these traditional controls may not be sufficient to achieve the National Ambient Air Quality Standard for ozone. We apply the MARKet ALlocation (MARKAL) energy system model in a sensitivity analysis to explore whether additional NOx reductions can be achieved through extensive electrification of passenger vehicles, adoption of energy efficiency and conservation measures within buildings, and deployment of wind and solar power in the electric sector. Nationally and for each region of the country, we estimate the NOx implications of these measures. Energy efficiency and renewable electricity are shown to reduce NOx beyond traditional controls. Wide-spread light duty vehicle electrification produces varied results, with NOx increasing in some regions and decreasing in others. However, combining vehicle electrification with renewable electricity reduces NOx in all regions. IMPLICATIONS: State governments are charged with developing plans that demonstrate how air quality standards will be met and maintained. The results presented here provide an indication of the national and regional NOx reductions available beyond traditional controls via extensive adoption of energy efficiency, renewable electricity, and vehicle electrification.