Unstable Wind Conditions Research Articles

A novel higher rotational speed maintaining control for wind power generation systems under unstable wind conditions

This study proposes the Higher Rotational Speed Maintaining (HRSM) control algorithm that is suitable for large wind speed fluctuations. One of the challenges faced by wind generators is operating with significant wind speed oscillations. A wind generator with a large moment of inertia increases the time constant in rotational speed control and delays the tracking of the optimal operating point. This delay could reduce generated power by up to 40% or more. There are numerous regions in Japan’s inland areas where average wind speeds exceed 6.5 m/s. However, frequent fluctuations in wind speeds make wind power generation challenging. Therefore, this paper proposes a control algorithm suitable for wind turbines operating under unstable wind conditions. Higher rotational speeds are required to convert sudden high wind speeds into higher power output, especially when wind speed oscillations are large. Hence, the proposed algorithm focuses on maintaining the rotational speed during periods of unstable wind conditions to improve generation efficiency. The effectiveness of the proposed control method for wind turbines is verified through numerical simulation results. The novel control algorithm aims to promote the spread of wind turbines in areas with unstable wind conditions by overcoming these disadvantages.

Interface of the Natural Ventilation Systems with Building Management Systems

The vertical city is increasingly being seen as the most viable solution for many urban centers. However, being vertical means constructing tall buildings which imply a large amount of energy requirement mostly due to the mechanical ventilation systems. Replacing these systems with natural ventilation is of importance on the way of achieving sustainable buildings and cities. However, there are many challenges in incorporating natural ventilation systems into tall office buildings. Because, having a far distance from the ground levels, tall buildings are exposed to turbulent and unstable wind conditions. Therefore, advanced technical systems to monitor/control a tall building is required even though natural ventilation is mostly considered a passive, low technological approach to condition a building. These systems utilize sensors to measure internal environmental conditions and external conditions of air temperature, humidity, wind velocity, and rain to utilize passive or active modes, based on the data received. To integrate such systems, in most cases, a hybrid approach is required to fill the gap between the natural and mechanical ventilation systems. Since, climate conditions may not be suitable for solely depending on natural ventilation throughout the year, using mechanical ventilation systems as a back-up to natural ventilation is mostly required. Based on this approach, this study presents advanced natural ventilation strategies of a number of buildings integrating Building Management Systems. Throughout the study, it is intended to guide further researches on natural ventilation and consequently to contribute to the environmental quality of urban areas and smart sustainable development of the cities.

A numerical investigation to analyze effect of turbulence and ground clearance on the performance of a roof top vertical–axis wind turbine

Recent attempts to discover energy–efficient and cost–effective power generation systems unleash tremendous capabilities of urban rooftops vertical–axis wind turbines (VAWT). Their advantages of Omni–directionality, low noise and less maintenance cost allow direct integration to urban neighborhood having unstable wind conditions. Despite continuous effort to investigate performance under a range of operating conditions, aspects such as Turbulent Intensity (TI) and ground clearance remain relatively less explored. Such effects originate either due to sharp topographical variations or placement of the turbine blades in proximity to the ground. In the present work, we perform a parametric study to quantify the performance of VAWT under various levels of TI and ground clearance. We conduct high fidelity Computational Fluid Dynamics (CFD) simulations using ANSYS Fluent and k−ε turbulence model. The H-type VAWT is employed having rated power of 1.5kW, diameter (D)of 2.5mchord length (c) of 0.2m and operates at prescribed wind speed (U0)of 12.0m/sand Tip Speed Ratio (TSR) of 1.5–4.5. We determine the performance of turbine under four levels of TI i.e., 0%, 5%, 15%25%at five ground clearance levels of 1.0c,2.5c,4.0c,7.5cand 10.0c. The results show a performance loss of 30.10%, 20.65%, 10.65% at turbine clearance heights of 1.0c,2.5c, 4.0c respectively. The height of 7.5c yield higher and more consistent performance under given operating conditions. The results for induced turbulence identify a decrease in the performance up to 45.42% corresponding to 25%TI level.

Improvement of High-Temperature Treatment Method using Solar Radiation under Unstable Wind Conditions

Open-top chambers (OTC) equipped with solar-heated double funnels (SDF) were tested for high-temperature treatments under unstable wind conditions. OTC-SDFs have two types of funnel-shaped tunnels attached on opposite ends; OTC-SDF-A had SDFs of the same width, and the OTC-SDF-B had SDFs that were twice the width of the open end. The temperature rise in these OTC-SDFs were compared with that in OTC with solar-heated air introduction tunnel (OTC-SAT). The temperature increase in the OTC-SAT during the daytime was small and not flat, whereas that in OTC-SDF-A was higher than in OTC-SAT and almost flat. The temperature rise was further enhanced in the OTC-SDF-B. An increase in air exchange ability at the intake may account for this enhancement. The drop in temperature at night observed in OTC-SAT was less prominent in OTC-SDFs. Based on these data, OTC-SDFs are considered useful in areas where the wind speed and direction are unstable.

Lifting Wing in Constructing Tall Buildings —Aerodynamic Testing

This paper builds on previous research by the authors which determined the global state-of-the-art of constructing tall buildings by surveying the most active specialist tall building professionals around the globe. That research identified the effect of wind on tower cranes as a highly ranked, common critical issue in tall building construction. The research reported here presents a design for a “Lifting Wing,” a uniquely designed shroud which potentially allows the lifting of building materials by a tower crane in higher and more unstable wind conditions, thereby reducing delay on the programmed critical path of a tall building. Wind tunnel tests were undertaken to compare the aerodynamic performance of a scale model of a typical “brick-shaped” construction load (replicating a load profile most commonly lifted via a tower crane) against the aerodynamic performance of the scale model of the Lifting Wing in a range of wind conditions. The data indicate that the Lifting Wing improves the aerodynamic performance by a factor of up to 50%.

COMPUTER VISION‐BASED ORTHOPHOTO MAPPING OF COMPLEX ARCHAEOLOGICAL SITES: THE ANCIENT QUARRY OF PITARANHA (PORTUGAL–SPAIN)

Ancient quarries are intriguing archaeological sites, but their detailed recording is complex. This paper presents a cost‐effective approach to mapping of the Roman quarry site of Pitaranha (Portugal–Spain). First, aerial photographs were acquired using a radio‐controlled digital reflex camera attached to a Helikite, which allowed the acquisition of the necessary low‐altitude aerial footage in the very unstable wind conditions above the quarry. Using computer vision algorithms, the resulting set of photographs was semi‐automatically transformed into a Digital Surface Model (DSM) and a corresponding orthophotograph. Besides focusing on the acquisition and processing method, this paper evaluates the accuracy of the generated products. The orthophotograph proved to be satisfactorily accurate for 1:200 hard‐copy mapping.

Dynamics of Short Sea Wave Spectrum Estimated From Microwave Radiometric Measurements

This paper presents some results of the experiment CAPMOS'05 performed on an oceanographic research platform in the Black Sea. The platform, located 600 m offshore, was equipped with a set of contact and remote sensing instruments. Conventional contact sensors were used for direct measurements of atmosphere and sea boundary layer parameters (wind speed and direction, air temperature, water temperature and salinity profiles, etc.), whereas microwave and infrared band radiometers were used for remote sensing measurements of surface temperature and wave parameters. In particular, microwave Ka-band radiometer measurements were applied for gravity-capillary wave spectrum retrieval using the original techniques based on angular measurements. The spectrum component evolution under unstable wind conditions has been investigated. It has been demonstrated that the spectral components in the vicinity of the maximum of the wave curvature are the most sensitive to the wind-velocity variations.