An Analysis of Thermal Plant Flexibility Using a National Generator Performance Database.

Grid integration studies are key to understanding our ability to integrate variable generation resources into the power system and evaluating the associated costs and benefits. In these studies, it is important to understand the flexibility of the thermal power fleet, including how thermal plants operate at part load. Without a comprehensive understanding of thermal plant operation, we may over- or underestimate our ability to integrate variable generation resources and thus draw incomplete or inaccurate conclusions regarding their potential economic and environmental effects. The only public data source for understanding many elements of the operational characteristics of the thermal fleet is the U.S. Environmental Protection Agency Clean Air Markets database of historical power plant operation. However, though these data sets have been widely utilized, their use has proven to be difficult, and methods to clean and filter the data are not transparent. Here, we describe the database and a method to clean and filter it. We then use the cleaned database to demonstrate several characteristics of historical plant operation, including frequent part load operation. Finally, we provide a cleaned data set with heat rate curves and describe how to use it in general modeling activities and analysis.

Emissions reductions from expanding state-level renewable portfolio standards.

In the United States, state-level Renewable Portfolio Standards (RPS) have served as key drivers for the development of new renewable energy. This research presents a method to evaluate emissions reductions and costs attributable to new or expanded RPS programs by integrating a comprehensive economic dispatch model and a renewable project selection model. The latter model minimizes incremental RPS costs, accounting for renewable power purchase agreements (PPAs), displaced generation and capacity costs, and net changes to a state's imports and exports. We test this method on potential expansions to Michigan's RPS, evaluating target renewable penetrations of 10% (business as usual or BAU), 20%, 25%, and 40%, with varying times to completion. Relative to the BAU case, these expanded RPS policies reduce the CO2 intensity of generation by 13%, 18%, and 33% by 2035, respectively. SO2 emissions intensity decreased by 13%, 20%, and 34% for each of the three scenarios, while NOx reductions totaled 12%, 17%, and 31%, relative to the BAU case. For CO2 and NOx, absolute reductions in emissions intensity were not as large due to an increasing trend in emissions intensity in the BAU case driven by load growth. Over the study period (2015 to 2035), the absolute CO2 emissions intensity increased by 1% in the 20% RPS case and decreased by 6% and 22% for the 25% and 40% cases, respectively. Between 26% and 31% of the CO2, SO2, and NOx emissions reductions attributable to the expanded RPS occur in neighboring states, underscoring the challenges quantifying local emissions reductions from state-level energy policies with an interconnected grid. Without federal subsidies, the cost of CO2 mitigation using an RPS in Michigan is between $28 and $34/t CO2 when RPS targets are met. The optimal renewable build plan is sensitive to the capacity credit for solar but insensitive to the value for wind power.

Secondhand smoke exposure in the nonsmoking section: how much protection?

INTRODUCTION: Secondhand smoke (SHS) exposure continues to be a problem in bars and restaurants where smoking is permitted. This study measures the relative SHS exposure reduction in nonsmoking sections of establishments that allow some smoking. METHODS: Measurements were conducted simultaneously in the smoking and nonsmoking sections of 14 Minnesota hospitality venues. All of the 16 two-hr visits included photometer measurements of fine particles (PM2.5) and 12 of the visits also included measurements of 4 gas-phase tracers of SHS. RESULTS: The median ratio of nonsmoking/smoking section PM2.5 concentrations was 0.65 with an interquartile range (IQR) of 0.49-0.72. Measurements conducted after implementation of a smoking ban at 13 of the venues resulted in a smoking section PM2.5 post-ban/pre-ban ratio of 0.06 (IQR = 0.02-0.16). The median nonsmoking/smoking section ratios for gas-phase compound were 0.67 (IQR = 0.35-0.78) for pyridine, 0.52 (IQR = 0.30-0.70) for pyrrole, 0.43 (IQR = 0.35-0.84) for 3-EP, and 0.27 (IQR = 0.16-0.47) for nicotine. These results are consistent with the expectations of differential removal: the lowest ratios are for the least volatile, most strongly sorbing gases and the highest ratios for less sorbing gases and PM2.5. CONCLUSIONS: Designated nonsmoking sections in establishments that allow some smoking resulted in a median PM2.5 reduction of 35% compared with a 94% reduction after a smoking ban. The only adequate protection from cigarette smoke exposure is to eliminate smoking in indoor spaces.