Field measurement and modeling of UVC cooling coil irradiation for heating, ventilating, and air conditioning energy use reduction (RP-1738)—Part 2: Energy, indoor air quality, and economic modeling

Ultraviolet germicidal irradiation of cooling coil airside surfaces is used to mitigate biofouling caused by viable microorganisms captured from the air. However, few peer-reviewed studies have investigated its effectiveness. Part 1 of this study presents the results of field measurements of changes in coil performance after treatment with ultraviolet germicidal irradiation. Part 2 reports modeled energy use and indoor air quality impacts of coil irradiation, as well as results of a life-cycle cost analysis that combines energy, indoor air quality, capital, and maintenance costs. Life-cycle costs with coil ultraviolet germicidal irradiation are compared to life-cycle costs with mechanical coil cleaning. Models from the U.S. Department of Energy Commercial Reference Buildings set were used to predict the benefit of ultraviolet germicidal irradiation treatment of fouled coils for 7 buildings in 16 climate zones using pressure drop reduction estimates bounded by experimental results from Part 1 and results reported in literature. Indoor air quality benefits were estimated using a stochastic implementation of the Wells-Riley equation to predict infection rates and monetized metrics appropriate to the various occupancies considered. Using lower estimates of ultraviolet germicidal irradiation energy use impact, ultraviolet germicidal irradiation was economically superior to mechanical cleaning only when collateral air treatment benefits were considered. At the higher level of estimated improvement, ultraviolet germicidal irradiation was superior even without consideration of air quality impact.