1. Operation modeling and comparison of actual multi-effect distillation and reverse osmosis desalination plants
Authors: Sebastian A. Romo, Michael Storch Jr., Jelena Srebric
Publication Date: 2024-02-01
Journal: Desalination, 2024
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► Abstract
Modeling actual desalination plants is often restricted by unknown parameters and system specifications that can be difficult to obtain or measure in the field. In this study, we propose an operational data recovery methodology to estimate unknown parameters and construct a simulation that accurately reproduces the operation of actual desalination systems. Furthermore, the data recovery methodology enables desalination modeling with a data-driven iterative sampling scheme to find the most plausible operation scenario. The complete models with data recovery are deployed in four case studies of desalination plants in the field: two multi-effect distillation with thermocompression (MDT) and two reverse osmosis with pressure exchange (ROX). The results show excellent agreement with actual plant operation data, reflected by the maximum difference between simulated and collected data of 5.5 % and 2.5 % for the two MDT plants as well as 6.4 % and 9.3 % for the two ROX plants. Importantly, this study introduced a new theoretical efficiency metric to define optimal operation of a desalination plant. This metric allowed to highlight two plants operating around 20 % below their theoretically achievable recovery. This efficiency calculation and complete models could help plant managers identify underperforming plants and evaluate potential upgrades.
2. A wearable micro air cleaner for occupant-oriented indoor environmental controls
Authors: Lingzhe Wang, Sebastian A. Romo, Elaine Sanico, Hevander Da Costa, Tong Lin, Nicholas Rabchevsky, Moritz Kern, Shengwei Zhu, Jelena Srebric
Publication Date: 2023-09-01
Journal: Building and Enviornment, 2023
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► Abstract
Centralized ventilation could be problematic in situations where individuals require specific air quality conditions for infection control purposes. Among other mitigation methods, masks may cause thermal discomfort, and personalized ventilation with a fixed position could lose its function with user's movement. This study developed a novel wearable micro air cleaner to provide personalized protection in occupant breathing zone. The device needs to provide effective protection while maintaining thermal comfort, therefore this study conducted the tracer gas and human subject experiments to investigate the protective performance and thermal comfort impact of this device. By successfully balancing the component performance and size, this device achieved the protective efficiency of 77% for mouth breathing and 63% for nasal breathing. Additionally, this device offered satisfied thermal comfort experience for users at indoor air temperatures higher than 25 °C. To identify the actual thermal comfort requirements of the user, this study also developed data-driven thermal comfort models utilizing collected physiological data. By considering the heart rate variability (HRV), the performances achieved by the developed data-driven thermal comfort models were higher than 0.9. Overall, the wearable micro air cleaner could be an effective occupant-oriented indoor environmental control method to promise the individualized air quality without limiting user's activities.
3. Mapping of a novel zero-liquid discharge desalination system based on humidification–dehumidification onto the field of existing desalination technologies
Authors: Sebastian A. Romo, Mohammed Elhashimi, Bahman Abbasi, Jelena Srebric
Publication Date: 2022-10-30
Journal: Water, 2022
Full paper
► Abstract
It is well-established that increasing demands for fresh water are paving the way for desalination technologies. However, this correlates with an increase in brine production whose treatment and disposal can be complicated and expensive. This paper presents a thermodynamic model to bound the operation and development of a novel Humidification–Dehumidification-based system featuring Zero-Liquid Discharge and off-grid capabilities. The model employs conservation laws to find feasible state points to meet a baseline operation of 10 kg/h of product water separated from a hypersaline feed stream with 100 g/kg salt concentration. The system incurs in a 1039 kWh/m3 energy intensity that can be supplied completely by an electric source or in combination with heating steam. Follow-up sensitivity analysis highlights the robustness of the system in handling variations of 25% in product flowrate and 75% in feed salinity, practically without incurring any additional energy demands. The proposed system operating costs between 72 USD/m3 and 96 USD/m3 are comparable to those of existing brine disposal techniques. Furthermore, an operational map of existing desalination technologies suggests a niche characterized by high recovery rates and high feed salinities that are generally unfulfilled by conventional desalination methods. Overall, the proposed system shows potential for off-grid hypersaline brine treatment. This study sets the stage for future development of physics-based and data-driven predictive models as the proposed system iterates into a pilot plant deployment.
4. Desalination metamodels and a framework for cross-comparative performance simulations
Authors: Sebastian A. Romo, Nicholas Mattise, Jelena Srebric
Publication Date: 2022-03-01
Journal: Desalination, 2022
Full paper
► Abstract
There is an opportunity to save energy and reduce operational expenses when choosing a suitable desalination method aided by computational modeling. Existing models are not conducive to generalized comparisons between different desalination methods. Therefore, this study developed metamodels for six desalination methods, grouped them into thermal and molecular transport families, and validated their predictive performance within 9% difference from published data. This validated framework allowed comparisons of desalination methods at their prescribed ranges of operational conditions that they were designed for. These conditions specify feed salinity ranges of 1.6 to 2.4 g/kg for Capacitive Deionization and Reverse Osmosis (RO), 2.8 to 4.2 g/kg for Electrodialysis, 28 to 42 g/kg for Thermovapor Compression and Humidification-Dehumidification, and 37 to 55 g/kg for Multi-Effect Distillation (MED). Despite different operational conditions, all models exhibit non-linear, positive correlation between energy consumption and system size in response to feed salinity and production rate. The framework is also employed in a cross-comparative analysis between MED and RO whose results suggest that energy intensity for MED is an order of magnitude greater than RO for the same operational conditions, but actual operational costs are comparable. Overall, the framework is ready for deployment in case studies of actual desalination plants.
5. Ventilation and laboratory confirmed acute respiratory infection (ARI) rates in college residence halls in College Park, Maryland
Authors: Shengwei Zhu, Sara Jenkins, Kofi Addo, Mohammad Heidarinejad, Sebastian A. Romo, Avery Layne, Joshua Ehizibolo, Daniel Dalgo, Nicholas W. Mattise, Filbert Hong, Oluwasanmi O. Adenaiye, Jacob P. Bueno de Mesquita, Barbara J. Albert, Rhonda Washington-Lewis, Jennifer German, Sheldon Tai, Somayeh Youssefi, Donald K. Milton, Jelena Srebric
Publication Date: 2020-04-01
Journal: Environment International, 2020
Full paper
► Abstract
Strategies to protect building occupants from the risk of acute respiratory infection (ARI) need to consider ventilation for its ability to dilute and remove indoor bioaerosols. Prior studies have described an association of increased self-reported colds and influenza-like symptoms with low ventilation but have not combined rigorous characterization of ventilation with assessment of laboratory confirmed infections. We report a study designed to fill this gap. We followed laboratory confirmed ARI rates and measured CO2 concentrations for four months during the winter-spring of 2018 in two campus residence halls: (1) a high ventilation building (HVB) with a dedicated outdoor air system that supplies 100% of outside air to each dormitory room, and (2) a low ventilation building (LVB) that relies on infiltration as ventilation. We enrolled 11 volunteers for a total of 522 person-days in the HVB and 109 volunteers for 6069 person-days in the LVB, and tested upper-respiratory swabs from symptomatic cases and their close contacts for the presence of 44 pathogens using a molecular assay. We observed one ARI case in the HVB (0.70/person-year) and 47 in the LVB (2.83/person-year). Simultaneously, 154 CO2 sensors distributed primarily in the dormitory rooms collected 668,390 useful data points from over 1 million recorded data points. Average and standard deviation of CO2 concentrations were 1230 ppm and 408 ppm in the HVB, and 1492 ppm and 837 ppm in the LVB, respectively. Importantly, this study developed and calibrated multi-zone models for the HVB with 229 zones and 983 airflow paths, and for the LVB with 529 zones and 1836 airflow paths by using a subset of CO2 data for model calibration. The models were used to calculate ventilation rates in the two buildings and potential for viral aerosol migration between rooms in the LVB. With doors and windows closed, the average ventilation rate was 12 L/s in the HVB dormitory rooms and 4 L/s in the LVB dormitory rooms. As a result, residents had on average 6.6 L/(s person) of outside air in the HVB and 2.3 L/(s person) in the LVB. LVB rooms located at the leeward side of the building had smaller average ventilation rates, as well as a somewhat higher ARI incidence rate and average CO2 concentrations when compared to those values in the rooms located at the windward side of the building. Average ventilation rates in twenty LVB dormitory rooms increased from 2.3 L/s to 7.5 L/s by opening windows, 3.6 L/s by opening doors, and 8.8 L/s by opening both windows and doors. Therefore, opening both windows and doors in the LVB dormitory rooms can increase ventilation rates to the levels comparable to those in the HVB. But it can also have a negative effect on thermal comfort due to low outdoor temperatures. Simulation results identified an aerobiologic pathway from a room occupied by an index case of influenza A to a room occupied by a possible secondary case.
