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Studying effectiveness of UV coil cleaning

Penn State alumnus Joseph Firrantello inspects the ductwork, pipes and controls of a building’s HVAC system. Photo: Penn State

USA: Researchers at Penn State University are investigating the effectiveness and safety of ultraviolet germicidal irradiation (UVGI) when applied to cooling coils.

The research involves the installation of sensors to collect temperature, humidity, air flow and pressure drop data on HVAC cooling coils before and after UVGI is used to clean away the build-up of microorganisms. The project uses the data collected from the field research to create models that estimate the potential energy and indoor air quality benefits of UVGI cleaning.

“UVGI has been used for water, air and surface disinfection for over 100 years, but applications to control indoor air quality have not been as well studied as they should, leading to questions about the effectiveness and safety of this technology,” explained lead researcher and professor of architectural engineering William Bahnfleth. “Through our work, we hope to answer important questions about how well UVGI works under different conditions, when its use should be considered, and whether there are safety issues associated with its use that need to be addressed.”

Ultraviolet irradiation in the UVC band is an alternative or adjunct to mechanical and chemical cleaning options. Bahnfleth admits that UVGI systems are currently available from many manufacturers but, due to the lack of independent research and analysis to document the effectiveness of UVGI coil cleaning, their use is limited.

The work is said to align with the ASHRAE Research Strategic Plan, which outlines the Society’s research goals for the next five years.

“The ASHRAE Research Strategic Plan represents the current priorities of the built environment industry to solve the most pressing problems related to providing a high level of indoor environmental quality while minimising impacts on the environment,” Bahnfleth said.

This research aims to provide the architectural engineering and building communities with a comprehensive analysis of the energy benefits of using UVGI to decrease the microorganism buildup on cooling coils, as well as an approach to use these results in a design application. Experimentally verified models have been developed to implement into practical design tools.

“Building designers and analysers need to be able to predict the effects of their choices on significant aspects of building performance, in particular, indoor air quality, temperature and humidity and energy use,” Bahnfleth said. “User-friendly tools for modelling the indoor environment and predicting its impact on occupants — acute and chronic health effects and productivity — are not available today.”

The field measurements have provided real-world data on the improvements to system performance due to UVGI cleaning and information on the method used to measure these improvements. Data is being applied in a range of building energy models to measure potential energy and IAQ improvements.

“The most important function of buildings is to provide a safe, healthy, and productive environment for occupants. It is clear from a large body of research that it is possible to do better than we are today,” Bahnfleth said. “Conservation of energy and other resources, and reduction of environmental pollution, are important related objectives that need to be addressed in parallel. Until we can provide high-quality indoor environments to all in buildings that make efficient use of clean energy, there will be work to do.”

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