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  Cornell University

MAE Publications and Papers

Sibley School of Mechanical and Aerospace Engineering

New article: The Near-Source Impacts of Diesel Backup Generators in Urban Environments

Article:  Tong, ZM; Zhang, KM; (2015)  “The Near-Source Impacts of Diesel Backup Generators in Urban Environments”, Atmospheric Environment, 109:256-271

DOI

Abstract:  Distributed power generation, located close to consumers, plays an important role in the current and future power systems. However, its near-source impacts in complex urban environments are not well understood. In this paper, we focused on diesel backup generators that participate in demand response (DR) programs. We first improved the micro-environmental air quality simulations by employing a meteorology processor, AERMET, to generate site-specific boundary layer parameters for the Large Eddy Simulation (LES) modeling. The modeling structure was then incorporated into the CTAG model to evaluate the environmental impacts of diesel backup generators in near-source microenvironments. We found that the presence of either tall upwind or downwind building can deteriorate the air quality in the near-stack street canyons, largely due to the recirculation zones generated by the tall buildings, reducing the near-stack dispersion. Decreasing exhaust momentum ratio (stack exit velocity/ambient wind velocity) draws more exhaust into the recirculation zone, and reduces the effective stack height, which results in elevated near-ground concentrations inside downwind street canyons. The near-ground PM2.5 concentration for the worst scenarios could well exceed 100 mu g m(-3), posing potential health risk to people living and working nearby. In general, older diesel backup generators (i.e., Tier 1, 2 or older) without the up-to-date emission control may significantly increase the pollutant concentration in the near-source street canyons if participating in DR programs. Even generators that comply with Tier-4 standards could lead to PM hotspots if their stacks are next to tall buildings. Our study implies that the siting of diesel backup generators stacks should consider not only the interactions of fresh air intake and exhaust outlet for the building housing the backup generators, but also the dispersion of exhaust plumes in the surrounding environment. (C) 2015 Elsevier Ltd. All rights reserved.

Funding Acknowledgement:  New York State Energy Research and Development Authority (NYSERDA); Electric Power Research Institute (EPRI)

Funding Text:  The authors appreciate the primary funding support from the New York State Energy Research and Development Authority (NYSERDA), and supplemental funding support from Electric Power Research Institute (EPRI). The authors would also like to thank Drs. Steven Perry and David Heist at USEPA for sharing the experimental data described in the paper.

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