10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
Air Quality Impact of Distributed Combined Heat and Power Facilities
BO YANG, K. Max Zhang, Cornell University
Abstract Number: 1637 Working Group: Aerosol Transport and Transformation
Abstract Distributed generation (DG) has been more generally used to supply energy to the end users. Compared with centralized generation, DG has many advantages. Generating power on-site eliminates the cost, complexity and inefficiencies associated with transmission and distribution. However, since on-site DG facilities are close to the end users, the hydrocarbon fuelled DG emissions could be an important health issue.
The on-site air quality impacts of two different DG facilities on university campuses were investigated. One is a biomass fuelled combined heat and power (CHP) system equipped with an electrostatic precipitator (ESP). The other is a natural gas turbine CHP system with duct burners and a heat recovery steam generator (HRSG). For the biomass system, two rooftop sampling stations with PM2.5 and CO2 analyzers were established in such that one could capture the plume while the other one served as the background for comparison depending on the wind direction. Four sonic anemometers were deployed around the stack to quantify spatially and temporally resolved local wind patterns. For the natural gas turbine system, the in-stack emission tests were conducted in 2010 and 2015. PM2.5, NOx and other gas emissions were recorded. The emission data over time were analyzed by comparing these two sets of measurements.
A CFD-based model, Comprehensive Turbulent Aerosol Dynamics and Gas Chemistry (CTAG), was employed to analyze the measurement data and estimate the spatial variations of near-source pollutants. The primary PM2.5 dispersion and chemical transformation of gaseous pollutants were simulate using the real terrain, local buildings, and meteorological data.
The simulation results demonstrated the near-ground “hotspots” would pose potential health risks to building occupants since ultrafine particles could penetrate indoors via infiltration, natural ventilation, and fresh air intakes on the rooftop of multiple buildings. Furthermore, spatial distributions of high ground level concentrations obtained by using CTAG were different from those by using a Gaussian-based parameterized model, AERMOD, largely due to that the CFD-based CTAG model can capture the building downwash effect much better than Gaussian-based models. Building downwash causes emissions entrainment inside wake zones next to buildings and lead to elevated local air quality impact, especially when the DG facilities have comparatively shorter stacks in an urban area. The implications on mitigating on-site air pollution and the suggestions on permitting DG facilities were discussed.