New York State’s Climate Leadership and Community Protection Act (CLCPA) is transforming New York’s energy industry by relying more heavily on distributed energy resources (DERs). Shifting from central generation to a DER-based grid increases system efficiency and also presents challenges with respect to air quality. Incorporating zero-on-site emissions renewables such as solar PV and wind turbines will also provide emissions reductions and likely benefits regional air quality. However, increased use of hydrocarbon-fueled distributed generation (DG) units, that generally have shorter stacks than central station power plants and low exhaust temperatures, may have an impact on air quality in the local vicinity of the source especially when located near population centers. Air quality assessments are critical to evaluating the societal benefits of REV.
EERL is undertaking a comprehensive study on evaluating the air quality impacts of DG. Four types of DG were investigated, including diesel backup generators (BUGs), commercial-scale biomass-fueled heating systems, simple cycle natural gas turbines and distributed combined heat and power (CHP) facilities, through high-fidelity numerical simulations, integrated air quality/micrometeorology monitoring, stack monitoring and utilization of existing datasets. EERL has developed several novel methods and concepts in evaluating the DG impact. An integrated Gaussian dispersion-CFD modeling framework was proposed to evaluate the near-source air quality impact of the DG facilities. Specifically, the worst cases were efficiently captured by using a Gaussian-based dispersion modeling system as a screening tool, which then were investigated in detail using detailed computational fluid dynamics (CFD) simulations. The heat recovery amplified factor (HRAF) concept was introduced an indicator to characterize the near-source air quality impact of heat recovery, which increase the overall thermal efficiency of electric generation units (EGUs) but reduce stack exit temperature, resulting in lower effective emission heights and potentially higher near-source ground level concentrations (GLCs) of air pollutants.
This project has resulted in a number of important policy-relevant findings on siting combustion-based DG units. It has been showed that the siting of DG stacks should consider not only the interactions of fresh air intake and exhaust outlet for the building housing the backup generators (as recommended by ASHRAE), but also the dispersion of exhaust plumes in the surrounding environment. Otherwise, the environmental impact from diesel BUGs participating in demand response (DR) programs could potentially become an unintended consequence of DR programs, as they are traditionally perceived as clean resources for power systems. we proposed the concept of “Green” DR resources, referring to those that not only provide power systems reliability services, but also have verifiable environmental benefits or minimal negative environmental impacts. We argue that Green DR resources that are able to maintain resource adequacy and reduce emissions at the same time are key to achieving the cobenefits of power system reliability and protecting public health during periods with peak electricity demand. Urban DG units may contribute to the above-ground “hotspots” that would pose potential health risks to building occupants since particles could penetrate indoors via infiltration, natural ventilation, and fresh air intakes on the rooftop of multiple buildings. However, most permitting processes of new power plants in the U.S only consider ground-level concentrations, which could underestimate the health risk from above-ground pollutant “hotspots”. Moreover, considering the tradeoff between near-source environment and boiler efficiency, simply targeting on high energy efficiencies in distributed heating systems may deteriorate the air quality of surrounding environment. Overall, scientifically sound siting requirements have the potential to effectively mitigate the negative air quality impact from DG.
Currently, EERL is developing new algorithms to represent the local air quality of building downwash. A novel concept of sidewash and downwash has been proposed. The goal is to incorporate the new algorithm into the USEPA AERMOD modeling system.
Publications
Yang, B., Gu, J. and Zhang, K.M. Parameterization of the building downwash and sidewash effect using a mixture model. Building and Environment, 172: 106694, 2020
Bo Yang, Jiajun Gu, Tong Zhang and K. Max Zhang, “Near-source air quality impact of a distributed natural gas combined heat and power facility.” Environmental Pollution, 246: 650-657, 2019
Yang, B., Gu, J., Zhang, K.M., The effect of heat recovery on near-source plume dispersion of a simple cycle gas turbine, Atmospheric Environment 184: 47-55, 2018
Gu, J., Yang, B., and Zhang, K. M. Spatial-aware source estimation in building downwash environments, Building and Environment, 134: 146-154, 2018.
Yang, B. and Zhang, K. M. CFD-based turbulent reactive flow simulations of power plant plumes, Atmospheric Environment, 150: 77-86, 2017
Tong, Z., Yang, B., Hopke, P., and Zhang, K. M. Microenvironmental Air Quality Impact of a Commercial-Scale Biomass Heating System, Environmental Pollution, 220: 1112-1120, 2017.
Tong, Z. and Zhang, K. M., The Near-Source Impacts of Diesel Backup Generators in Urban Environments. Atmospheric Environment, 2015,109, 262-271
Zhang, X.; Zhang, K. M., Demand Response, Behind-the-Meter Generation and Air Quality. Environmental Science and Technology, 2015, 49 (3): 1260-1267
