Engineering topics

Underhill, Ronald M.

Publications and source records attributed to Underhill, Ronald M..

7 records

DOE OSTI2022

Size dependent infectivity of SARS-CoV-2 via respiratory droplets spread through central ventilation systems

In this work, we evaluate the transport of respiratory droplets that carry SARS-CoV-2 through central air handling systems in multiroom buildings. Respiratory droplet size modes arise from the bronchioles representing the lungs and lower respiratory tract, the larynx representing the upper respiratory tract including vocal cords, or the oral cavity. The size distribution of each mode remains largely conserved, although the magnitude of each droplet mode changes as infected individuals breathe, speak, sing, laugh, cough, and sneeze. Here we evaluate how each type of respiratory droplet transits through central ventilation systems and the implications thereof for infectivity of COVID-19. We find that while larger oral droplets can transmit through the air handling systems, their size and concentration are greatly reduced with but few oral droplets leaving the source room. In contrast, the smaller droplets that originate from the bronchioles and larynx are much more effective in transiting through the air handling system into connected rooms. This suggests that the ratio of lower respiratory or deep lung infections may increase relative to upper respiratory infections in rooms connected by central air handling systems. Also, increasing the temperature and humidity in the range considered after the droplets have achieved an “equilibrium” size reduces the probability of infection.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2022

Experimental evaluation of respiratory droplet spread to rooms connected by a central ventilation system

This article presents results from an experimental study to ascertain the transmissibility of the SARS-CoV-2 virus between rooms in a building that are connected by a central ventilation system. Respiratory droplet surrogates made of mucus and virus mimics were released in one room in a test building and measurements of concentration levels were made in other rooms connected via the ventilation system. The paper presents experimental results for different ventilation system configurations, including ventilation rate, filtration level (up to MERV-13), and fractional outdoor air intake. The most important finding is that respiratory droplets can and do transit through central ventilation systems, suggesting a mechanism for viral transmission (and COVID-19 specifically) within the built environment in reasonable agreement with well-mixed models. We also find the deposition of these droplets on room walls to be negligibly small. Furthermore, the energy use impact of the different configuration settings is also quantified to help inform intelligent building operation that can simultaneously address energy use and occupant health.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2021

Prevalence of typical operational problems and energy savings opportunities in U.S. commercial buildings

In the United States, as much as 30% of the 19 EJ that commercial buildings consume is considered excess. Much of the excess energy is due to the inability to manage building operations efficiently. Because almost 20% of the total primary energy consumption is associated with commercial buildings, significant energy reductions in this sector are needed to mitigate climate change. Therefore, many cities and states are mandating periodic “tune-ups” of these buildings to eliminate excess energy consumption. Although the benefits of tune-ups and retro-commissioning are clear, focusing these mandates to look for specific opportunities has been a challenge because of the lack of studies that document the prevalence of opportunities. Therefore, we analyzed building automation system data from 151 buildings across the United States to document common operational problems and opportunities to improve building operations. This analysis showed that opportunities to improve building operations exist in almost every building. These opportunities were not strongly correlated with building vintage or size, but were reflective of how the buildings are operated. The prevalence of the top 20 opportunities ranged between 74% and 23%, with 40% of these associated with air-handling units. The rest of the opportunities are associated with schedules, chilled and hot-water distribution, and zone controls. Of the 151 buildings, 69 of them implemented corrective actions of some or all opportunities that were identified. Implementation varied across the Re-tuning categories, with 60% for schedule opportunities, 50% for zone opportunities, over 40% for the air-handling unit and hot-water opportunities, and 35% of the chilled-water opportunities. There was wide variation in whole building energy savings, ranging from 0 to 50% and 0 to 18 $/m2 with median percent annual whole building savings of 12% and median normalized annual cost savings of $1.75/m2. In addition to documenting these key findings, the paper provides a list of opportunities that can be automatically and continuously identified and corrected and offers a list of those opportunities that should be the focus of the mandates.

Katipamula, Srinivas↗

DOE OSTI2021

Investigation of potential aerosol transmission and infectivity of SARS-CoV-2 through central ventilation systems

Here we evaluate the concentrations and probabilities of infection for both building interior and exterior exposure sources using a well-mixed model in a connected multizone building. As a central hub of many community and economic activities, buildings provide social connectivity, but the COVID-19 pandemic has reduced social connectivity due to concerns of viral spread within buildings. Although single zone models of infectious spread are well studied, the impact of aerosolized spread of SARS-CoV-2 via air handling systems in multizone buildings remains unexplored. Here we evaluate the influence of filtration, air exchange rates, and the fraction of outdoor air on the probability of infection using the well-known well-mixed modeling approach for a multizone. We find filtration lowers the concentration and probability of infection in both source and connected rooms provided at least some air is recirculated, but that probability is not zero. Filtration has no influence without recirculation or unless the outdoor air contains virus. We find that increasing the air exchange rate removes virus from the source room faster but also increases the rate of exposure to connected rooms. Therefore, slower air exchange rates reduce infectivity in connected rooms at shorter durations, but higher air exchange rates reduce infectivity at longer durations. We further find that when outdoor air is virus free, increasing the fraction of outdoor air is helpful, but, when outdoor air is infective, pathogen exposure inside can persist for hours after a short-term release.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2020

Delivering Energy Efficiency and Grid Services for Commercial Buildings on an IoT-Platform: Field Evaluation Plan

In FY20, the Commercial Buildings Integration Program (CBI) within Building Technologies Office (BTO) has funded PNNL to conduct field evaluation of the AIRCx and intelligent load control (ILC) using an Internet-of-Things (IoT) platform, VOLTTRON. The primary goal of the project is to show that software solutions deployed and delivered through an IoT-platform can identify energy efficiency opportunities and manage peak load in commercial buildings. There are also two secondary goals: 1) show that the energy efficiency solutions will result in identification of significant savings (10% to 30%) opportunities as well as energy cost reductions (10% to 15%) by managing the peak load in commercial buildings, and 2) show that an IoT-based software solution is more cost-effective in meeting the Re-tuning mandates than traditional retro commissioning (RCx) and there is a pathway for broader adoption of this approach. This report details how the field evaluation will be conducted, including what enhancements will be made to the software technologies, how PNNL will recruit energy service providers, types of buildings where the technology will be evaluated, metric of success for the field evaluation, and how the metric of success will be measured.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

DOE OSTI2019

Highlights and Lessons Learned from Army Re-tuning™ Pilot Demonstrations

The Army has aggressively pursued policy and energy efficiency projects and programs in recent years to meet Federal mandates and reduction goals organizationally (EISA 2007, AR 420-1, 42 U.S.C. § 8253), resulting in a 9.6% reduction in energy use intensity (EUI) from FY2015 to FY2017. Despite these successes, the Army remains the largest consumer of electricity in the Federal government and spent approximately $1.1 billion in energy-related costs in FY2017. Many of the low-cost/no-cost conservation measures have been deployed, so finding additional savings and projects that either (a) are cost effective or (b) can be bundled with more costly capital improvement projects to improve life cycle cost effectiveness, is imperative for the Army. Leveraging building control systems (BCS) and optimizing building performance through re-tuning represents a great opportunity for the Army. In 2016, the Pacific Northwest National Laboratory (PNNL), in support of the Assistant Secretary of the Army (Installations, Energy and Environment), i.e. ASA (IEE), was tasked in 2016 with a multi-year study and pilot demonstration to develop a business case for the potential energy and cost reduction benefits from re-tuning efforts for the Army.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

DOE OSTI2019

Army Re-tuning™ Implementation Guides

The Army is a large, geographically dispersed organization with 156 installations and over 980 million square feet of building space to operate and maintain. The building stock spans a wide range of vintages and missions, with many serving cross-cutting functions and purposes. To meet Federal mandates and reduction goals organizationally, in recent years the Army has aggressively pursued policy and energy efficiency projects and programs resulting in a 9.6% reduction in energy use intensity (EUI) from fiscal year (FY) 2015 to FY2017. Despite these successes, the Army remains the largest consumer of electricity in the Federal government and spent approximately $1.1 billion in energy-related costs in FY2017 The Pacific Northwest National Laboratory (PNNL), in support of the Assistant Secretary of the Army (Installations, Energy and Environment) (ASA (IE&E)), was tasked with a multi-year study and pilot demonstration to develop a business case for the potential energy and cost reduction benefits from re-tuning™ efforts for the Army. Re tuning is a systematic process aimed at minimizing building energy consumption by identifying and correcting operational problems that plague buildings. The methodology was developed by PNNL research staff in an effort to improve building operational efficiency at no- or low-cost, primarily through building automation system (BAS) controls. The methodology is based on two basic principles: If the equipment is not needed, turn it off; and if the equipment is not needed at full power, turn it down. Implementation of identified low-cost/no-cost operational improvements through the re-tuning process results in increased building energy efficiency, reduced operating costs, and improvement to occupant comfort.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗