AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
Abstract View
Building-Integrated Low-Cost Optical Particle Counters: Conceptual Framework and Field Measurements in an Occupied Office and Air Handling Unit
BRANDON E. BOOR, Donghyun Rim, Purdue University
Abstract Number: 623 Working Group: Indoor Aerosols
Abstract The evolving domain of low-cost (<$1,000) sensor technologies for the measurement of airborne particles and gases presents vast opportunities for real-time monitoring and control of pollutants in buildings. Research is needed to provide guidance to indoor air quality researchers and practitioners, along with the HVAC industry, on how to integrate low-cost sensors with building systems to reduce population exposures to airborne pollutants of indoor and outdoor origin. The objectives of this study are to (1) establish a conceptual framework for the integration of low-cost optical particle counters (OPCs) with building systems and (2) conduct field measurements with a commercially available OPC (OPC-N2 Particle Monitor, AlphaSense Ltd.).
The framework for building-integrated OPCs is based upon a material-balance modeling approach, whereby all processes that generate or remove particles from a spatial domain are accounted for, e.g. emissions, ventilation, filtration, deposition. The material-balance model can inform the number and location of OPC sensor nodes that are necessary to mechanistically evaluate indoor particle dynamics in each zone (room) of a building. Such an approach will ensure sufficient spatiotemporal input data are collected to identify (in real-time) appropriate control strategies to maintain particle concentrations below specified levels. We explore the application of our framework for building-integrated OPCs in an occupied office and air handling unit (AHU) in the new Living Laboratories at Purdue Herrick Laboratories. Five calibrated OPC-N2 sensors were installed to monitor particle number size (Dp, optical diameter) distributions (dN/dlogDp, cm$^(-3)) across sixteen size fractions from 0.38 to 17 μm at various nodes, including: (1) bulk room air, (2) AHU intake of outdoor air, (3) upstream and (4) downstream of in-duct filters, and (5) AHU recirculation. We studied the impact of modulating AHU settings, including fan speed and damper positions, via the NiagaraAX building automation system; manual-replacement of in-duct filters of varying MERV-rating; natural ventilation via a double-skin façade; and office occupancy on dN/dlogDp at each node. The dN/dlogDp data for each condition is then used in a material-balance model to estimate size-resolved indoor emission rates, in-situ filtration efficiencies, deposition loss rate coefficients, and indoor/outdoor ratios.