WIND LOADS ON ROOFING SYSTEM AND PHOTOVOLTAIC SYSTEM INSTALLED PARALLEL TO FLAT ROOF

2020 ◽  
Vol 7 (1) ◽  
Author(s):  
Tetsuo Yambe ◽  
Yasushi Uematsu ◽  
Kosuke Sato
Keyword(s):  
Time History ◽  
Photovoltaic System ◽  
Pressure Equalization ◽  
Pv Systems ◽  
External Pressures ◽  
Wind Actions ◽  
Strong Winds ◽  
Wind Pressures ◽  
Flat Roof ◽  
Roofing System

Mechanically-attached waterproofing system has become popular in Japan. Being vulnerable to wind actions, especially to suctions, this roofing system is often damaged by strong winds. Similarly, photovoltaic (PV) systems installed on flat roofs are often damaged by strong winds, because the PV panels are subjected to large wind forces in an adverse wind. In order to reduce such damage to both systems, the authors propose to install the PV panels parallel to the flat roof with gaps between them, which may reduce the net wind forces on the PV panels due to the effect of pressure equalization. In addition, the wind pressures acting on the waterproofing system will decrease significantly. The present paper investigates the validity of the above-mentioned idea. The wind pressures underneath the PV panels, called ‘layer pressures’, are evaluated by a numerical simulation using the unsteady Bernoulli equation together with the time history of external pressures measured at many locations on the rooftop of a flat-roofed building model in a turbulent boundary layer. The results clearly indicate a significant reduction of wind forces acting on the PV panels as well as on the waterproofing system. The use of PV panels for reducing the wind pressures on waterproofing system is quite effective to the corner region of the roof, where very large suctions are induced in a diagonal wind.

scholarly journals The Benefit of Horizontal Photovoltaic Panels in Reducing Wind Loads on a Membrane Roofing System on a Flat Roof

Wind ◽  
2021 ◽  
Vol 1 (1) ◽  
pp. 44-62
Author(s):  
Yasushi Uematsu ◽  
Tetsuo Yambe ◽  
Tomoyuki Watanabe ◽  
Hirokazu Ikeda
Keyword(s):  
Time History ◽  
External Pressure ◽  
Shielding Effect ◽  
Bottom Surface ◽  
Wind Resistance ◽  
Pressure Equalization ◽  
Pv Panel ◽  
Strong Winds ◽  
Flat Roofs ◽  
Roofing System

The present paper proposes a measure for improving the wind-resistant performance of photovoltaic systems and mechanically attached single-ply membrane roofing systems installed on flat roofs by combining them together. Mechanically attached single-ply membrane roofing systems are often used in Japan. These roofing systems are often damaged by strong winds, because they are very sensitive to wind action. Recently, photovoltaic (PV) systems placed on flat roofs have become popular. They are also often damaged by strong winds directed onto the underside, which cause large wind forces onto the PV panels. For improving the wind resistance of these systems, we proposed to install PV panels horizontally with gaps between them. Such an installation may decrease the wind forces on the PV panels due to the pressure equalization effect as well as on the waterproofing membrane due to the shielding effect of the PV panels. This paper discusses the validity of such an idea. The pressure on the bottom surface of a PV panel, called the “layer pressure” here, was evaluated by a numerical simulation based on the unsteady Bernoulli equation. In the simulation, the time history of the external pressure coefficients, measured at many points on the roof in a wind tunnel, was employed. It was found that the wind forces, both on the PV panels and on the roofing system, were significantly reduced. The reduction was large near the roof’s corner, where large suction pressures were induced in oblique winds. Thus, the proposed method improved the wind resistance of both systems significantly.

Comparisons of design wind pressures on roof-mounted solar arrays between wind tunnel tests and codes and standards

2020 ◽  
pp. 136943322096527
Author(s):  
Jingxue Wang ◽  
Qingshan Yang ◽  
Yi Hui
Keyword(s):  
Wind Tunnel ◽  
Experimental Results ◽  
Solar Panels ◽  
Wind Tunnel Tests ◽  
Pressure Equalization ◽  
Solar Arrays ◽  
Side Ratio ◽  
Design Values ◽  
Wind Pressures ◽  
Flat Roof

The current codes and standards concerning wind loads on roof-mounted solar panels are discussed and summarized. Wind pressures on flat- and slope-roof-mounted solar arrays obtained from wind tunnel tests are compared with the recommended design values in ASCE 7-16 and JIS C 8955: 2017. Different parameters, including building side ratio, aspect ratio and parapet height, are examined. Results show that the largest wind pressures on flat-roof-mounted solar panels of all zones in ASCE 7-16 tend to be 10% to 26% smaller than the experimental results when normalized tributary area An is larger than 103. Uplift wind forces on flat-roof-mounted solar panels in downstream regions obtained from experiments can be larger than the recommended values in JIS C 8955: 2017 for adverse wind, but downward force coefficients are basically smaller than those in JIS C 8955: 2017 for fair wind. 40% to 60% increase on the pressure equalization factor for slope-roof-mounted solar panels is suggested for the potential refinement of ASCE 7-16 based on this study. Meanwhile, proposed pressures of slope-roof-mounted solar panels in JIS C 8955: 2017 might be too conservative according of experimental results.

Wind-induced internal pressures on large cooling towers

2019 ◽  
Vol 22 (15) ◽  
pp. 3249-3261
Author(s):  
XX Cheng ◽  
G Wu ◽  
L Zhao ◽  
PF Li ◽  
YJ Ge
Keyword(s):  
Internal Pressure ◽  
Cooling Tower ◽  
Dominant Factor ◽  
Cooling Towers ◽  
Theoretical Formulation ◽  
Internal Surfaces ◽  
External Pressures ◽  
Strong Winds ◽  
Wind Pressures ◽  
Internal Pressures

Effects of wind-induced internal pressures on the cooling tower’s structural performances are as significant as those of wind-induced external pressures. However, comparing to wind-induced external pressures, limited research focuses on wind pressures on the internal surfaces of large cooling towers. To fill up the scientific void, numerical analyses, physical model tests, and analytical studies are undertaken in this article. It is demonstrated that the draught ventilation ratio (i.e. the total area of the openings on the stuffing layer divided by the area of the stuffing layer) is the dominant factor for wind-induced internal pressures on large cooling towers, and 15% draught ventilation ratio can be regarded as the most unfavorable case. Besides, it is revealed that the theoretical formulation of the internal pressure on a single-cell building with a dominant opening and background porosity proposed by some other researchers can be applied to the case of a cooling tower subjected to strong winds. Using the validated theoretical formulation, the geometry of a large cooling tower is optimized with regard to the most favorable wind-induced internal pressure. The findings of this article are helpful for improving the current Chinese Code that governs the design of cooling towers.

scholarly journals A Grid-Supporting Photovoltaic System Implemented by a VSG with Energy Storage

Energies ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 3152 ◽  
Author(s):  
Huadian Xu ◽  
Jianhui Su ◽  
Ning Liu ◽  
Yong Shi
Keyword(s):  
Energy Storage ◽  
Synchronous Generator ◽  
Photovoltaic System ◽  
Voltage Source ◽  
Frequency Regulation ◽  
Pv System ◽  
Storage Unit ◽  
Support Functions ◽  
Energy Storage Unit ◽  
Pv Systems

Conventional photovoltaic (PV) systems interfaced by grid-connected inverters fail to support the grid and participate in frequency regulation. Furthermore, reduced system inertia as a result of the integration of conventional PV systems may lead to an increased frequency deviation of the grid for contingencies. In this paper, a grid-supporting PV system, which can provide inertia and participate in frequency regulation through virtual synchronous generator (VSG) technology and an energy storage unit, is proposed. The function of supporting the grid is implemented in a practical PV system through using the presented control scheme and topology. Compared with the conventional PV system, the grid-supporting PV system, behaving as an inertial voltage source like synchronous generators, has the capability of participating in frequency regulation and providing inertia. Moreover, the proposed PV system can mitigate autonomously the power imbalance between generation and consumption, filter the PV power, and operate without the phase-locked loop after initial synchronization. Performance analysis is conducted and the stability constraint is theoretically formulated. The novel PV system is validated on a modified CIGRE benchmark under different cases, being compared with the conventional PV system. The verifications demonstrate the grid support functions of the proposed PV system.

scholarly journals Short and open circuit faults study in the PV system inverter

2021 ◽  
Vol 12 (3) ◽  
pp. 1764
Author(s):  
Mohammed Bouzidi ◽  
Abdelkader Harrouz ◽  
Tadj Mohammed ◽  
Smail Mansouri
Keyword(s):  
Short Circuit ◽  
Electric Utility ◽  
Open Circuit ◽  
Photovoltaic System ◽  
Pv System ◽  
Simple Method ◽  
Pv Systems ◽  
Pv Array ◽  
Main Component ◽  
Types Of Faults

<p>The inverter is the principal part of the photovoltaic (PV) systems that assures the direct current/alternating current (DC/AC) conversion (PV array is connected directly to an inverter that converts the DC energy produced by the PV array into AC energy that is directly connected to the electric utility). In this paper, we present a simple method for detecting faults that occurred during the operation of the inverter. These types of faults or faults affect the efficiency and cost-effectiveness of the photovoltaic system, especially the inverter, which is the main component responsible for the conversion. Hence, we have shown first the faults obtained in the case of the short circuit. Second, the open circuit failure is studied. The results demonstrate the efficacy of the proposed method. Good monitoring and detection of faults in the inverter can increase the system's reliability and decrease the undesirable faults that appeared in the PV system. The system behavior is tested under variable parameters and conditions using MATLAB/Simulink.</p>

scholarly journals Wind Loads on a Solar Panel at High Tilt Angles

2019 ◽  
Vol 9 (8) ◽  
pp. 1594 ◽  
Author(s):  
Chin-Cheng Chou ◽  
Ping-Han Chung ◽  
Ray-Yeng Yang
Keyword(s):  
Wind Wave ◽  
Aerodynamic Characteristics ◽  
Solar Panel ◽  
Photovoltaic System ◽  
Wind Loads ◽  
Solar Photovoltaic ◽  
Pv Systems ◽  
Proper Functioning ◽  
Extreme Wind ◽  
Solar Photovoltaic System

A solar photovoltaic system consists of tilted panels and is prone to extreme wind loads during hurricanes or typhoons. To ensure the proper functioning of the system, it is important to determine its aerodynamic characteristics. Offshore photovoltaic (PV) systems have been developed in recent years. Wind loads are associated with wind, wave climates, and tidal regimes. In this study, the orientation of a single panel is adjusted to different angles of tilt (10°–80°) and angles of incidence for wind (0°–180°) that are pertinent to offshore PV panels. The critical wind loads on a tilted panel are observed at lower angles of incidence for the wind, when the angle of tilt for the panel is greater than 30°.

scholarly journals Complete Procedure for the Economic, Financial and Cost-Competitiveness of Photovoltaic Systems with Self-Consumption

Energies ◽  
2019 ◽  
Vol 12 (3) ◽  
pp. 345 ◽  
Author(s):  
D. L. Talavera ◽  
E. Muñoz-Cerón ◽  
J. de la Casa ◽  
D. Lozano-Arjona ◽  
M. Theristis ◽  
...  
Keyword(s):  
Net Present Value ◽  
Photovoltaic System ◽  
The Novel ◽  
Training Requirements ◽  
Pv Systems ◽  
Profitability Analysis ◽  
Complete Procedure ◽  
Cost Competitiveness ◽  
Definition Of ◽  
Novel Concept

Nowadays, the integration of photovoltaic (PV) systems into the grid involves new and competitive ways to realize this. Thus, it is necessary to define procedures that not only include energy calculations but also incorporate economic and funding feasibility features. According to the literature review, there are numerous tools that are available to carry out a profitability analysis of a photovoltaic system. However, certain shortcomings have been identified, either in the definition of the economic and financial scenarios or in the results obtained, as they do not provide all the necessary information, do not use all the most common economic criteria, or in some cases the complexity and training requirements for their correct implementation may discourage their use. Therefore, in this paper a complete procedure that can be used as a preliminary decision tool prior to the design of an in-depth PV self-consumption system is proposed. Realistic input data makes it possible to not only obtain results for common economic and financial feasibility criteria (Net Present Value, Internal Rate of Return, Discounted Pay-Back Time and Net Cash Balance), but it also allow for a cost-competitiveness evaluation based on the Levelised Cost of Electricity (LCOE). The novel concept of the direct cost of PV self-consumed electricity is also introduced.

scholarly journals Study on Premature Failure of PV Systems in Malaysia using FMEA and Integrated ISM Approaches

2018 ◽  
Vol 225 ◽  
pp. 04004
Author(s):  
Tan Dei Han ◽  
Mohamad Rosman M. Razif ◽  
Shaharin A. Sulaiman
Keyword(s):  
Rural Areas ◽  
Cooling System ◽  
Photovoltaic System ◽  
Extensive Literature ◽  
Solar Photovoltaic ◽  
Pv System ◽  
Premature Failure ◽  
Pv Systems ◽  
Operation And Maintenance ◽  
Solar Photovoltaic System

Solar photovoltaic (PV) systems has the potential of supplying infinite electricity from renewable energy to rural areas around Malaysia. Various preterm failures happening frequently on the system lead to its drop in efficiency and breakdown. Lack of studies on the system in Malaysia hinders the development in terms of operation and maintenance. There is no proper documentation relevant to the premature failure of the system in Malaysia. The main objective of this project is to study the nature of premature failure of stand-alone solar photovoltaic system in Malaysia in order to improve the operation and maintenance of the system. The present study would provide reference for proper planning on operation and maintenance of the PV system. The study was conducted base on expert’s input and extensive literature survey. FMEA method and ISM approach are applied to analyze the data collected. Poor cooling system have the highest risk priority number. Poor workmanship is the least depending factor for premature failure to happen thus requires most attention. Highest driving force of premature failure is poor monitoring and maintenance. More focus should be given to these premature failure during the planning for operation and maintenance due to its severity and impact.

scholarly journals Methodology to Determine Photovoltaic Inverter Conversion Efficiency for the Equatorial Region

2019 ◽  
Vol 10 (1) ◽  
pp. 201
Author(s):  
Azhan Ab. Rahman ◽  
Zainal Salam ◽  
Sulaiman Shaari ◽  
Mohd Zulkifli Ramli
Keyword(s):  
Conversion Efficiency ◽  
Peak Power ◽  
Climatic Conditions ◽  
Equatorial Region ◽  
Photovoltaic System ◽  
Energy Yield ◽  
Peak Efficiency ◽  
Pv Systems ◽  
One Year ◽  
Equatorial Climate

Photovoltaic inverter conversion efficiency is closely related to the energy yield of a photovoltaic system. Usually, the peak efficiency (ηmax) value from the inverter data sheet is used, but it is inaccurate because the inverter rarely operates at the peak power. The weighted efficiency is a preferable alternative as it inherently considers the power conversion characteristics of the inverter when subjected to varying irradiance. However, since the weighted efficiency is influenced by irradiance, its value may not be appropriate for different climatic conditions. Based on this premise, this work investigates the non-suitability of the European weighted efficiency (ηEURO) for inverters installed in the Equatorial region. It utilizes a one year data from the Equatorial irradiance profile to recalculate the value of ηEURO (ηEURO_recal) and to compare it with the original ηEURO. Furthermore, a new weighted efficiency formula for the Equatorial climate (ηEQUA) is proposed. Validation results showed that calculated energy yield with ηEQUA closely matched the real energy yield of 3 kW system with only 0.16% difference. It is envisaged that the usage of ηEQUA instead of ηmax or ηEURO will results in a more accurate energy yield and return of investment calculations for PV systems installed in Equatorial regions.

An Innovative Structural Health Monitoring System for Large Transmission Towers Based on GPS

2019 ◽  
Vol 19 (04) ◽  
pp. 1971002 ◽  
Author(s):  
X. X. Cheng ◽  
Y. J. Ge
Keyword(s):  
Structural Health Monitoring ◽  
Real Time ◽  
Health Monitoring ◽  
Time History ◽  
Time Behavior ◽  
Structural Health ◽  
Transmission Towers ◽  
Strong Winds ◽  
Force Equilibrium

In this paper, we propose an innovative structural health monitoring (SHM) system for large transmission towers that are frequently subjected to strong winds. The system is based on the strategy of using a static force equilibrium equation to calculate the whole structure’s real-time stress distribution according to its real-time behavior, as captured by the global positioning system (GPS). The reason for adopting this approach is that large transmission towers are fundamentally quasi-static structures and they are not prone to resonance under wind excitations. A case study is used to present the SHM system, then its effectiveness is validated by comparing the simulated SHM results with the exact solution obtained by a realistic time-history dynamic analysis. Additionally, we discuss the use of a new reliability analysis method based on the Ditlevsen’s bounds to assess the real-time structural conditions.

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