Increasing use of volatile renewable energy sources causes challenges in balancing supply and demand. Therefore, demand-side flexibility has rising importance for system operators and balancing ...authorities. Flexibility management methods are needed to integrate loads like ventilation systems of different buildings (e.g., residential and commercial) into flexibility service. However, the available methods described in research papers require further development for implementation in practice. Heating and cooling systems have received much attention from researchers, but the potential of ventilation systems has been left out of focus. Therefore, this paper provides a complete set of novel flexibility management methods for ventilation systems created from an aggregator's viewpoint. The flexibility is quantified through capacity (e.i. the amount of power consumption that can be altered), forced ventilation rate duration, and the tendered price for the service. The proposed methods were tested on a building model constructed and simulated in IDA ICE. The data processing and flexibility management methods were applied in MATLAB. Two types of ventilation systems with different sensor configurations were considered: constant and variable air volume. Forced ventilation rate duration is calculated using energy and mass balance analysis where the root means squared error was 10 to 33 min, depending on the system type, measured parameter, and sensor location. The flexibility service pricing model was tested on the 2022 years' manual frequency restoration reserve (mFRR) activation and balance energy market data.
Experimental and numerical investigations were performed in a research operating room to compare laminar air flow and turbulent mixing ventilation systems in reducing the concentrations of airborne ...germs and surgical smoke in operating room air. In addition, measurements at scattered positions were conducted to find positions that are suited best for airborne monitoring in real-time during surgeries. In the experiments, particle counters were used to sample tracer aerosols originating from the wound area and the facial area of the thermal manikins representing surgical staff. The results showed that it is important to perform monitoring close to the areas with high hygiene requirements. Increasing the air change rate with turbulent mixing ventilation significantly reduced the number of airborne particles, however, not in the surgical microenvironment. Our findings show varying results considering the particle concentration using laminar air flow compared to turbulent mixing ventilation. With laminar air flow, higher contaminant levels are obtained in the areas with a high demand for contamination reduction. In contrast, laminar air flow was more effective in reducing the concentration of surgical smoke in the facial areas of the surgical staff. Regarding airborne germs, monitoring should be performed at the instrument tables and close to the wound area to evaluate the risk for surgical side infections. These results can support the development of guidelines and best practices for operating room ventilation design and maintenance to improve patient safety and reduce the risk of healthcare-associated infections.
•OR air flow studied through experimental and numerical analysis.•Germs and smoke spread in realistic OR conditions examined.•LAF led to higher concentrations of airborne germs above the wound area.•No negative link found between ACR and particle concentration.•Live monitoring of airborne contaminations should be close to the protected areas.
Ensuring good indoor air quality is critical in hospitals. An environment free from airborne particles can prevent the spread of various diseases and improve patient health. In this study, the ...efficiency of a personalised ventilation supply system (PSS) and personalised ventilation extraction system (PES) for diluting and removing contaminants exhaled by a patient in a hospital bed was evaluated. These systems, which were integrated into the head and foot of a hospital bed, were combined with three general ventilation strategies in the room. Fifteen ventilation strategies were analysed experimentally. Two breathing thermal manikins (BTMs) were used to simulate a patient and health worker in a hospital. The breathing of each BTM was controlled by the patient (source) generating particles that can increase the risk of infection in a healthy person (target). Experimental results show that using a PES combined with general ventilation of the room reduces the exposure of the target manikin compared to general ventilation strategies alone. However, no marked improvement was observed when the PSS was activated. The reduction in exposure to the target manikin was considerable when the PES was located at the foot of the hospital bed, which is the preferred option for integrating personalised systems in a hospital bed.
Display omitted
•Assessment of exposure to exhaled contaminants in a hospital room was investigated.•Ventilation systems are used to reduce intake fraction in health worker.•Personalised ventilation extraction at head of the bed reduced intake fraction.•Personalised ventilation supply and extraction systems didn't reduce exposure.
•The proposed proactive 2-stage demand-controlled ventilation (P2S-DCV) method improves the DCV performance.•A deep neural network -based prediction model is proposed to predict future indoor CO2 and ...applies ventilation control in advance.•A reinforcement learning-based method is proposed to achieve accurate and rapid airflow control.•The fan pressure and damper positions are optimized to minimize energy consumption.•The proposed P2S-DCV method has good generalization ability under various conditions.
This paper presents a novel method, named proactive 2-stage demand-controlled ventilation (P2S-DCV) method, to maintain indoor air quality (IAQ) and reduce the energy consumption of multi-zone ventilation systems. The proposed P2S-DCV method applies a proactive control scheme, which predicts future indoor CO2 concentration and supplies proper ventilation to each zone. The method includes two stages. In Stage I, a DNN prediction model is established to predict the future CO2 concentration to calculate the corresponding demand airflow. In Stage II, a reinforcement learning method is designed to achieve rapid and accurate control, and further reduce the energy consumption by optimizing the fan pressure and damper positions. A 5-zone ventilation system is established to validate the proposed P2S-DCV method. The experiment verifies that: a) it can maintain comfortable IAQ via predicting the change of future indoor CO2 and applying effective ventilation control in advance; b) it can improve the control performance, the accuracy is maintained within 8 % (satisfied the ASHRAE Standards), and the control time is maintained within minutes. It can reduce the regulating time by 83.62 % compared with ASHRAE Ratio method, and up to 51.68 % compared with PID method; c) it can reduce the fan energy consumption by 16.4 % compared with ASHRAE Ratio method, and up to 21.8 % compared with PID method; d) it has good generalization ability for various IAQ requirements and ventilation systems with different topologies.
A VENTILATION INDEX FOR TROPICAL CYCLONES Tang, Brian; Emanuel, Kerry
Bulletin of the American Meteorological Society,
12/2012, Letnik:
93, Številka:
12
Journal Article
Recenzirano
Odprti dostop
An important environmental control of both tropical cyclone intensity and genesis is vertical wind shear. One hypothesized pathway by which vertical shear affects tropical cyclones is midlevel ...ventilation—or the flux of low-entropy air into the center of the tropical cyclone. Based on a theoretical framework, a ventilation index is introduced that is equal to the environmental vertical wind shear multiplied by the nondimensional midlevel entropy deficit divided by the potential intensity. The ventilation index has a strong influence on tropical cyclone climatology. Tropical cyclogenesis preferentially occurs when and where the ventilation index is anomalously low. Both the ventilation index and the tropical cyclone's normalized intensity, or the intensity divided by the potential intensity, constrain the distribution of tropical cyclone intensification. The most rapidly intensifying storms are characterized by low ventilation indices and intermediate normalized intensities, while the most rapidly weakening storms are characterized by high ventilation indices and high normalized intensities. Since the ventilation index can be derived from large-scale fields, it can serve as a simple and useful metric for operational forecasts of tropical cyclones and diagnosis of model errors.
•Mixing and displacement ventilation systems incorporated to a fitting room are investigated using computational fluid dynamics (CFD).•The air velocity and temperature distributions are analyzed to ...calculate the draft risk by means of the percentage dissatisfied (PD) approach.•The numerical results obtained are discussed and commented to highlight the efficient ventilation system that can provide an optimal thermal comfort.•The main findings showed very satisfactory results that agree well with those available in the literature. Comparing to the mixing ventilation system, the displacement ventilation system demonstrated a high draft risk, at the floor level.•In the breathing zone, the displacement ventilation system showcased a uniform temperature in the cubicles.
This study aims to investigate the mixing and displacement ventilation systems commonly used in buildings indoor ventilation by means of computational fluid mechanics (CFD). The study is carried out using steady-state methodology to examine the indoor air velocity and temperature distributions, which in turn, are used to estimate the draft risk with the percentage dissatisfied (PD) at different planes in a fitting room model in presence of five occupants. The results are analyzed and discussed to compare the two ventilation configurations in terms of pleasant air velocity and uniform temperature distribution for an optimal thermal comfort. The main findings are such as the displacement ventilation provides a uniform temperature distribution at breathing zone level, whereas the mixing ventilation performs best when it is a question of PD distribution.
•It offers a hierarchical scheme solution for the optimal control of multi-zone HVAC systems.•A deep reinforcement learning-based method is proposed to optimize airflow demands.•A genetic ...algorithm-based method is proposed to accurately track multi-zone airflows.•It achieves energy saving and good IAQ under dynamic environmental changes.•It exhibits good generalization under different occupancy schemes and system topologies.
Heating, ventilation, and air conditioning (HVAC) systems are designed to maintain a healthy indoor environment, where indoor air quality (IAQ) and energy use issues are of top concerns. This paper proposes a hierarchical optimal control method for multi-zone HVAC systems to improve IAQ while reducing fan energy consumption. The proposed hierarchical optimal control method consists of two levels. At the upper level, a virtual multi-zone HVAC environment is established and a soft actor-critic-based agent is trained under reinforcement learning framework to optimize the fan energy consumption while maintaining satisfactory IAQ in each zone. At the lower level, a “proportional balance + proportional recovery” strategy is devised to accurately track the terminal airflow via a hybrid search optimization method incorporating genetic algorithm and fmincon function. Compared with existing ventilation control methods, the proposed hierarchical optimal control method offers the following advantages: a) It can achieve good IAQ in multiple zones and low fan energy consumption by optimizing the demand airflow in response to the changes in real-time environment. b) It can accurately control the airflow with further energy saving, by optimizing the duct static pressure implicitly. c) Simulations demonstrate that the proposed method can achieve a maximum energy saving of 38.0 % and 43.6 % compared with two traditional methods, respectively. d) The proposed method exhibits good generalization ability under different occupancy scenarios and ventilation system topologies.
Introduction and purpose: The hospital wastewater plumbing system and ventilation systems can be possible routes of transmission of infectious agents, such as coronaviruses. Therefore, the purpose of ...this study was to review the conducted studies in this regard to determine the mechanism and possibility of transmission of coronaviruses through ventilation systems and wastewater plumbing in hospitals. Methods: In this narrative review, all the articles published in English since 2000 up to September 2020 on the possibility of transmitting coronaviruses, such as severe acute respiratory syndrome coronavirus 2, through ventilation systems and wastewater plumbing in hospitals were reviewed. These studies were obtained by searching the databases, including Google Scholar, ScienceDirect, and PubMed, using several keywords, such as “Coronavirus”, “SARS-CoV-2”, “COVID-19”, “Ventilation Systems”, and “Wastewater Plumbing Systems”. Results: Coronaviruses can enter wastewater through several sources, such as hand washing, sputum, vomit, and feces. Without proper maintenance and continuous monitoring, review, implementation, and update of building standards and practices, improper plumbing and sewage systems can continue to spread severe acute respiratory syndrome and some other infectious diseases. In addition, the factors, such as poor ventilation and recirculation, increase the potential for the viruses to spread indoors. Conclusion: The obtained results of the current study showed that the plumbing system is not a common method of transmitting the viruses, and the most prevalent route of transmission is considered respiratory droplets. Therefore, maintaining social distance and personal hygiene are among the most effective ways to prevent the transmission of coronaviruses.
The energy retrofit of existing buildings is a key strategy to reduce the energy costs of the building sector. Amongst the retrofit solutions, the adoption of mechanical ventilation systems ...represents a necessary approach for buildings with high crowding index, such as schools.
The air quality in schools is a main issue since children spend a significant fraction of the year in such microenvironments. To date, the scientific literature has carried out several studies concerning the air quality in naturally ventilated schools worldwide, nonetheless most of the studies performed a general evaluation of the air quality just using the CO2 as a comprehensive indicator. This is an oversimplified approach since the indoor air quality is affected by several pollutants, including airborne particles, whose behavior cannot be predicted by the CO2 one.
The aim of the research is the evaluation of the effect of the ventilation retrofit in a classroom on different indoor air quality parameters and energy consumption. To this end a mechanical ventilation system with a heat recovery unit was installed in a test-classroom and tests with CO2-based demand controlled ventilation were performed. CO2 levels and indoor-to-outdoor particle concentrations were measured and compared to the pre-retrofit ventilation conditions (i.e. manual airing procedures).
Results showed that mechanical ventilation systems have simultaneous positive effects on the different pollutants investigated as well as on ventilation heat losses: indeed, lower indoor-to-outdoor concentration ratios, with respect to the airing approach, were detected simultaneously for CO2, sub-micron particles and PM10.
•Indoor air quality and energy need in a classroom pre-/post-ventilation retrofit.•Indoor and outdoor measurements of CO2, particle number and PM10 concentrations.•Application of a mechanical ventilation system with energy recovery unit.•Improvement of indoor air quality and energy need with the post-retrofit solution.•Energy saving of 32% of the post-retrofit solution with respect the manual airing.
PDF
