Effectiveness of Intermittent Personalized Ventilation Assisting Chilled Ceiling in Protecting Occupants Against Active Particles

2019 ◽  
Author(s):  
Douaa Al-Assad ◽  
Nesreen Ghaddar ◽  
Kamel Ghali
Keyword(s):  
Particle Diameter ◽  
Operating Conditions ◽  
Thermal Manikin ◽  
Breathing Zone ◽  
Pv System ◽  
Active Particles ◽  
Comfort Levels ◽  
Office Space ◽  
Personalized Ventilation ◽  
Chilled Ceiling

Abstract In this work, an intermittent personalized ventilation (PV) system was coupled with a chilled ceiling system in an office space. The ability of this system in protecting occupants from active particulate matter due to an indoor contamination source was investigated. To perform this study, a 3D transient computational fluid dynamics model was used to determine the velocity, thermal, and particle concentration fields in the space. The fluid flow in the space was experimentally validated in previous works in a climatic chamber equipped with a thermal manikin representing an occupant in an office space. The validated model was used to perform a parametric study varying the intermittent PV operating frequency as well as the particle diameter. The results were used to recommend PV operating conditions, which would ensure the protection of occupant against the contaminants present in the macroclimate and deposited on nearby surfaces. It was found that the intermittent PV should operate at an average flow rate of 7.5 L/s and a frequency of 0.73 Hz. These conditions provided acceptable values of intake fraction in the breathing zone and surrounding microclimate and acceptable deposited fractions. Moreover, these conditions provided good thermal comfort levels (0.86: comfortable) and good protection against passive contaminants (εv,BZ = 64 %).

Performance of Intermittent Personalized Ventilation Assisting Mixing Ventilation in the Presence of Indoor Disturbance

2019 ◽  
Author(s):  
Douaa Al-Assad ◽  
Kamel Ghali ◽  
Nesreen Ghaddar
Keyword(s):  
Ventilation System ◽  
Pressure Gradients ◽  
Breathing Zone ◽  
Dynamics Model ◽  
Pv System ◽  
Low Frequencies ◽  
Air Ventilation ◽  
Airflow Field ◽  
Personalized Ventilation ◽  
Ventilation Systems

Abstract In this work, an office space is considered, equipped with an intermittent personalized ventilation (PV) system assisting a conventional mixing ventilation system. In ideal offices with no disturbances, it was proven that an intermittent PV average flow rate of 7.5 L/s and frequency of 0.86 Hz could enhance comfort compared to a steady PV and provide protection against contaminants present in the macroclimate. However, office spaces are subject to many disturbances, which could deteriorate the performance of air ventilation systems. In this work, an office door is considered to open disturbing the flow field by establishing pressure gradients. To conduct this study, a 3D computational fluid dynamics model was developed to predict the airflow field variables as well as contaminants’ concentration in the occupant-breathing zone. The model was used to assess the ability of the ventilation systems in maintaining its optimal operating parameters (0.86 Hz) obtained in ideal conditions. Results showed that the optimal PV frequency did not assure the same level of air quality. In fact, ventilation effectiveness decreased by 18% due to the opening door which pulled the PV jet away from the occupant’s breathing zone (BZ). Therefore, in office spaces with high disturbance levels, it is better off to operate the PV under steady state conditions to avoid further disturbance of the jet, or to operate the intermittent PV at low frequencies of 0.3 Hz to 0.5 Hz to minimize turbulence intensities created by the jet fluctuations.

scholarly journals Different Techniques to Mitigate Partial Shading in Photovoltaic Panels

Energies ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3863
Author(s):  
Tiago Alves ◽  
João Paulo N. Torres ◽  
Ricardo A. Marques Lameirinhas ◽  
Carlos A. F. Fernandes
Keyword(s):  
Cell Model ◽  
Research Work ◽  
Experimental Tests ◽  
Operating Conditions ◽  
Pv System ◽  
Partial Shading ◽  
System Architectures ◽  
Pv Systems ◽  
Advantages And Disadvantages ◽  
Pv Panel

The effect of partial shading in photovoltaic (PV) panels is one of the biggest problems regarding power losses in PV systems. When the irradiance pattern throughout a PV panel is inequal, some cells with the possibility of higher power production will produce less and start to deteriorate. The objective of this research work is to present, test and discuss different techniques to help mitigate partial shading in PV panels, observing and commenting the advantages and disadvantages for different PV technologies under different operating conditions. The motivation is to contribute with research, simulation, and experimental work. Several state-of-the-artsolutions to the problem will be presented: different topologies in the interconnection of the panels; different PV system architectures, and also introducing new solution hypotheses, such as different cell interconnections topologies. Alongside, benefits and limitations will be discussed. To obtain actual results, the simulation work was conducted by creating MATLAB/Simulink models for each different technique tested, all centered around the 1M5P PV cell model. The several techniques tested will also take into account different patterns and sizes of partial shading, different PV panel technologies, different values of source irradiation, and different PV array sizes. The results will be discussed and validated by experimental tests.

scholarly journals High Performance Multistring Converter Topology for Three-Phase Grid Tied 200 kW Photovoltaic Generating System

2017 ◽  
Vol 1 (2) ◽  
Author(s):  
Mohammad Rustam M. L. ◽  
F. Danang Wijaya
Keyword(s):  
Power Efficiency ◽  
High Performance ◽  
Reactive Power ◽  
Simulation Method ◽  
Operating Conditions ◽  
Total System ◽  
Voltage Reference ◽  
Pv System ◽  
Three Phase ◽  
Converter Topology

Under various external conditions, grid connected PV system performance is strongly affected by the topology that is used to connect a PV system with grid. This research aims to design a multistring based converter topology for three-phase grid connected 200 kW PV system that has a high performance in various operating conditions. Research was done by a simulation method using Matlab-Simulink with performance being evaluated including the generated power, efficiency, power quality in accordance with grid requirements, as well as the power flow. In the simulation, multistring converter topology was designed using two dc-dc boost multistring converters connected in parallel to a centralized of three-phase three-level NPC inverter with the size of the string being shorter and more parallel strings as well as the maximum voltage of the PV array of 273.5 V close to dc voltage reference of 500 V. Each dc-dc boost multistring converter have individual MPPT controllers. The simulation results showed that this multistring converter topology had a high performance in various operating conditions. This due to more power generated by the NPC inverter (> 190 kW) at the time of high power generation on the STC conditions (1000 W/m2, 25 oC), the lowest efficiency of the total system is 95.08 % and the highest efficiency of the total system is 99.4 %, the quality of the power generated in accordance with the requirements of grid, as well as the inverter put more active power to the grid and less reactive power to the grid. The response of the inverter slightly worse for loads with greater reactive power and unbalanced.

Performance of airflow distance from personalized ventilation on personal exposure to airborne droplets from different orientations

2020 ◽  
pp. 1420326X2095124
Author(s):  
Jingcui Xu ◽  
Sauchung Fu ◽  
Christopher Y. H. Chao
Keyword(s):  
Disease Transmission ◽  
Respiratory Activity ◽  
Personal Exposure ◽  
Healthy Person ◽  
Potential Method ◽  
Infected Person ◽  
Pv System ◽  
Testing Conditions ◽  
Proper Design ◽  
Personalized Ventilation

This study investigated the effect of airflow distance from a personalized ventilation (PV) system on the personal exposure of a PV user to exhaled droplets from different orientations. Constant and dynamic airflow from the PV system was studied. A PV system was designed to produce both constant and dynamic airflows with different periods. Thermal manikins were used to simulate a healthy person (HP), also the PV user, influenced by a respiratory activity from an infected person (IP) at different orientations. Results show that, with a short distance of 0.2 m between the PV and the HP, both constant and dynamic PV flow can effectively protect the HP at all orientations considered; with a longer distance of 0.5 m between the PV and the HP, at some orientations, neither constant PV flow nor dynamic PV flow could protect the HP from the IP under our testing conditions. PV is a potential method to prevent disease transmission. However, a proper design is essential, and the relative position of the PV terminal, the IP and the HP and the distance of the PV from the HP are important factors to be considered so as to achieve the best performance.

scholarly journals Design, Modeling, and Experimental Investigation of Active Water Cooling Concentrating Photovoltaic System

2020 ◽  
Vol 12 (13) ◽  
pp. 5392 ◽  
Author(s):  
Mohamed R. Gomaa ◽  
Mujahed Al-Dhaifallah ◽  
Ali Alahmer ◽  
Hegazy Rezk
Keyword(s):  
Thermal Energy ◽  
Thermal Power ◽  
Qualitative Evaluation ◽  
Operating Conditions ◽  
Photovoltaic System ◽  
Coolant Fluid ◽  
Working Fluid ◽  
Performance Study ◽  
Pv System ◽  
The Cost

This work presents performance study of a concentrating photovoltaic/thermal (CPV/T) collector and its efficiency to produce electric and thermal power under different operating conditions. The study covers a detailed description of flat photovoltaic/thermal (PV/T) and CPV/T systems using water as a cooling working fluid, numerical model analysis, and qualitative evaluation of thermal and electrical output. The aim of this study was to achieve higher efficiency of the photovoltaic (PV) system while reducing the cost of generating power. Concentrating photovoltaic (CPV) cells with low-cost reflectors were used to enhance the efficiency of the PV system and simultaneously reduce the cost of electricity generation. For this purpose, a linear Fresnel flat mirror (LFFM) integrated with a PV system was used for low-concentration PV cells (LCPV). To achieve the maximum benefit, water as a coolant fluid was used to study the ability of actively cooling PV cells, since the electrical power of the CPV system is significantly affected by the temperature of the PV cells. This system was characterized over the traditional PV systems via producing more electrical energy due to concentrating the solar radiation as well as cooling the PV modules and at the same time producing thermal energy that can be used in domestic applications. During the analysis of the results of the proposed system, it was found that the maximum electrical and thermal energy obtained were 170 W and 580 W, respectively, under solar concentration ratio 3 and the flow rate of the cooling water 1 kg/min. A good agreement between the theoretical and experimental results was confirmed.

scholarly journals Fuzzy Logic Control for Low-Voltage Ride-Through Single-Phase Grid-Connected PV Inverter

Energies ◽  
2019 ◽  
Vol 12 (24) ◽  
pp. 4796 ◽  
Author(s):  
Eyad Radwan ◽  
Mutasim Nour ◽  
Emad Awada ◽  
Ali Baniyounes
Keyword(s):  
Fuzzy Logic ◽  
Output Power ◽  
Single Phase ◽  
Reactive Power ◽  
Low Voltage ◽  
Operating Conditions ◽  
Pv System ◽  
Utilization Factor ◽  
Low Voltage Ride Through ◽  
Active And Reactive Power

This paper presents a control scheme for a photovoltaic (PV) system that uses a single-phase grid-connected inverter with low-voltage ride-through (LVRT) capability. In this scheme, two PI regulators are used to adjust the power angle and voltage modulation index of the inverter; therefore, controlling the inverter’s active and reactive output power, respectively. A fuzzy logic controller (FLC) is also implemented to manage the inverter’s operation during the LVRT operation. The FLC adjusts (or de-rates) the inverter’s reference active and reactive power commands based on the grid voltage sag and the power available from the PV system. Therefore, the inverter operation has been divided into two modes: (i) Maximum power point tracking (MPPT) during the normal operating conditions of the grid, and (ii) LVRT support when the grid is operating under faulty conditions. In the LVRT mode, the de-rating of the inverter active output power allows for injection of some reactive power, hence providing voltage support to the grid and enhancing the utilization factor of the inverter’s capacity. The proposed system was modelled and simulated using MATLAB Simulink. The simulation results showed good system performance in response to changes in reference power command, and in adjusting the amount of active and reactive power injected into the grid.

scholarly journals A Density Peak-Based Clustering Approach for Fault Diagnosis of Photovoltaic Arrays

2017 ◽  
Vol 2017 ◽  
pp. 1-14 ◽  
Author(s):  
Peijie Lin ◽  
Yaohai Lin ◽  
Zhicong Chen ◽  
Lijun Wu ◽  
Lingchen Chen ◽  
...  
Keyword(s):  
Fault Diagnosis ◽  
Local Density ◽  
Operating Conditions ◽  
Cluster Center ◽  
Pv System ◽  
Density Peak ◽  
Pv Systems ◽  
Distribution Features ◽  
Clustering Approach ◽  
Distance Vector

Fault diagnosis of photovoltaic (PV) arrays plays a significant role in safe and reliable operation of PV systems. In this paper, the distribution of the PV systems’ daily operating data under different operating conditions is analyzed. The results show that the data distribution features significant nonspherical clustering, the cluster center has a relatively large distance from any points with a higher local density, and the cluster number cannot be predetermined. Based on these features, a density peak-based clustering approach is then proposed to automatically cluster the PV data. And then, a set of labeled data with various conditions are employed to compute the minimum distance vector between each cluster and the reference data. According to the distance vector, the clusters can be identified and categorized into various conditions and/or faults. Simulation results demonstrate the feasibility of the proposed method in the diagnosis of certain faults occurring in a PV array. Moreover, a 1.8 kW grid-connected PV system with6×3 PVarray is established and experimentally tested to investigate the performance of the developed method.

Performance of Brushless DC Drive with Single Current Sensor Fed from PV with High Voltage-Gain DC-DC Converter

2018 ◽  
Vol 9 (1) ◽  
pp. 33
Author(s):  
G. G RajaSekhar ◽  
Basavaraja Banakara
Keyword(s):  
High Voltage ◽  
Operating Conditions ◽  
Current Sensor ◽  
Motor Drive ◽  
Voltage Gain ◽  
Bldc Motor ◽  
Pv System ◽  
Brushless Dc ◽  
High Voltage Gain ◽  
The Cost

This paper presents the performance of Brushless DC (BLDC) Motor drive with only one positioning sensor instead of three conventional sensors. The three sensor units are replaced with a single stator current sensor unit in DC bus which further reduces the cost increasing the reliability of the drive system. Using a single sensor in stator requires minimum electronic equipment for the purpose of measurement process. This paper evolves the BLDC motor drive fed from PV system. A high voltage-gain DC-DC converter is presented in this paper to step-up the voltage from PV system. The appropriateness of PV fed BLDC motor drive is verified for variable increamental speed with fixed torque and variable decremental speed with fixed torque operating conditions. BLDC motor drive performance is also performed for variable torque with fixed peed working condition. The proposed system and results are developed using MATLAB/SIMULINK software.

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