Investigations of a building‐integrated ducted wind turbine module

So far, wind energy has not played a major role in the group of technologies for embedded generation in the built environment. However, the wind flow around conventional tall buildings generates differential pressures, which may cause an enhanced mass flow through a building‐integrated turbine. As a first step, a prototype of a small‐scale ducted wind turbine has been developed and tested, which seems to be feasible for integration into the leading roof edge of such a building. Here an experimental and numerical investigation of the flow through building‐integrated ducting is presented. Pressure and wind speed measurements have been carried out on a wind tunnel model at different angles of incident wind, and different duct configurations have been tested. It was confirmed that wind speeds up to 30% higher than in the approaching freestream may be induced in the duct, and good performance was obtained for angles of incident wind up to ±60°. The experimental work proceeded in parallel with computational fluid dynamics (CFD) modelling. The geometry of the system was difficult to represent to the required level of accuracy, and modelling was restricted to a few simple cases, for which the flow field in the building‐integrated duct was compared with experimental results. Generally good agreement was obtained, indicating that CFD techniques could play a major role in the design process. Predicted power of the proposed device suggests that it will compare favourably with conventional small wind turbines and photovoltaics in an urban environment. Copyright © 2002 John Wiley & Sons, Ltd.     

Experimental investigation of wind effects on a standalone photovoltaic (PV) module

The pressure field on the upper and lower surfaces of a photovoltaic (PV) module comprised of 24 individual PV panels was studied experimentally in a wind tunnel for four different wind directions. The results show that the pressure distribution on the module surface is symmetric about its mid-plane for head-on wind (0° and 180°) and asymmetric at other wind directions. The inter-panel gap (which is essential in large PV modules) is found to influence module's surface pressure field. Pressure magnitudes on the module surface were increased with the module inclination angle, as expected. It is also observed that the mean pressure magnitudes on the PV module under smooth wind exposure are higher than those under open terrain wind exposure.     

Research of a new photovoltaic module

In this paper, a new photovoltaic module was proposed, in which all cells were connected to each other like a fishing net. When any each cell of the whole module got out of order, the photocurrent could flow through the neighbor well‐worked cells so that the photovoltaic output loss of the whole module was minimized as much as possible; at the same time, the bad‐worked cell could be well protected because only little photocurrent need to flow through the bad‐worked cell. Multisim soft was used to simulate the photovoltaic output of the series‐circuit module (SM) and fishing‐net module (FM) under the various experiment conditions, such as incidental light power, contaminant degree, and area ratio and module dimension (cell numbers in one module). The simulating results show that the FM photovoltaic output is larger in varying degrees than that of the SM under almost all the abovementioned experiment conditions. In the extreme case, here, all cells in one row of the SM and FM were completely bad‐worked, the SM photovoltaic out was zero, and the FM one decreases a little. In order to validate the reliability of the simulating results, the real 6 × 6 array SM and FM (36 real cells) were tested and analyzed comparatively under the same experiment condition, such as incidental light power and contaminant degree. The experiment results well according with the simulating ones suggest, again, that the FM photovoltaic output is exactly better than the SM one.     

某风电场风力发电机组故障诊断

为了准确判断风电机组的运行状态及故障,提出了基于常规分析—振动幅值分析—波形频谱分析的故障诊断流程,阐述了针对风电机组的幅值分析方法和波形频谱分析方法,并通过对某机组异响的根源探究实例,准确地诊断出机组异响来源于齿轮箱太阳轮,可为风电机组故障诊断技术提供依据。     

Modelling of a double-glass photovoltaic module using finite differences

A simulation model of finite differences describing a double-glass multi-crystalline photovoltaic module has been developed and validated using experimental data from such a photovoltaic module. This simulation model is based on various thermal hypotheses, particularly concerning the convective transfer coefficients: thus, various hypotheses found in the literature have been tested and the best one has been accepted. Using this modelling procedure, the cell temperature is estimated with a root mean square error of 1.3 °C.     

基于风电机组功率曲线的故障监测方法研究

为了最大限度地减少风机停机时间和提高风机发电量,基于风机功率曲线特性,结合多元统计Hotelling T~2控制图,提出了一种风力发电机性能及故障监测方法。首先,根据SCADA系统历史数据集,应用粒子群算法(PSO)寻优最小二乘支持向量机的模型,构造风电机组参考功率曲线。然后,计算风场各风机功率特性的多元峰度、多元偏度,将其偏离参考曲线的程度作为评估风力发电机性能的指标。最后,监测风机发生故障的时刻,引入用于监测风机的Hotelling T~2多变量质量控制图。将该方法用于某风场1.5 MW级风力发电机,实例表明,该算法可以有效地对风电机组状态及故障进行监测,为风电机组的故障识别及分析提供了一种新的方法。     

某风电场风机基础故障分析及处理

某沿海风电场建成1年后,多台风机陆续出现报警停机情况,风机基础承台混凝土与基础环之间缝隙有大量灰浆喷出,部分风机基础上表面开裂。文章对风机基础破坏机理进行了较全面的分析,认为基础环与承台之间存在的缝隙导致混凝土受力状态异常,同时水从缝隙进入基础加速了基础的破坏。根据故障原因分析结果采取相应的处理措施,对风机基础进行加固处理,主要采取注浆方法将风机基础承台混凝土与基础环之间缝隙填实,取得了良好的效果。文章对风机基础设计及加固处理、基础环设计等提出了建议,可供风机基础设计及处理同类事故参考。     

Periodic pulsations from a three-bladed wind turbine

In this paper, periodic power pulsations from a three-bladed wind turbine are analyzed. The influence of wind shear, wind speed, turbulence intensity, rotor position and tower oscillation is investigated. No clear dependence between the periodic power components and the wind shear or turbulence intensity has been verified. The investigated turbine sometimes produces large power pulsations at the tower resonance frequency. These occur when the turbine oscillates in the sideways direction of the nacelle     

Three-dimensional thermal modeling of a photovoltaic module under varying conditions

Photovoltaic technology provides the direct method to convert solar energy into electricity. Modeling and simulation plays a very important role in the development of PV devices as well as in the design of PV systems. The objective of the current work was to develop a novel thermal model to simulate the thermal performance of PV modules with and without cooling. The model was sequentially coupled with a radiation model and an electrical model to calculate the electrical performance of the PV panels. Using the developed model, various studies were performed to evaluate the electrical and thermal performance of the module under different environmental and operating conditions with and without cooling. Results show that the performance of the PV panel with cooling had very little influence of increasing absorbed radiation (200–1000 W/m²) at a constant ambient temperature (25 °C) and increasing ambient temperature (0–50 °C) at an absorbed radiation of 800 W/m². For the same variation in conditions, the performance of the panel without any cooling reduced significantly.     

基于风机状态细分的风机运营可靠性考核算法

针对风电运营中对风机可靠性考核的多样性需求与国内对风机运营可靠性考核方式单一的现状,在综合考虑了所有影响风力发电因素的基础上,设计出了基于风机状态最小粒度划分的风机运营可靠性考核算法。算法与风机模型解耦,可根据不同需求精确合理地定制不同计算指标,满足了风电运营中对可利用率计算的多样性需求,其作为南瑞继保PCS9700风电监控系统的关键搭载功能,在风电监控和风电集控领域得到应用和推广。     

Maximum thermodynamic power coefficient of a wind turbine

According to the centenary Betz‐Joukowsky law, the power extracted from a wind turbine in open flow cannot exceed 16/27 of the wind transported kinetic energy rate. This limit is usually interpreted as an absolute theoretical upper bound for the power coefficient of all wind turbines, but it was derived in the special case of incompressible fluids. Following the same steps of Betz classical derivation, we model the turbine as an actuator disk in a one dimensional fluid flow but consider the general case of a compressible reversible fluid, such as air. In doing so, we are obliged to use not only the laws of mechanics but also and explicitly the laws of thermodynamics. We show that the power coefficient depends on the inlet wind Mach number , and that its maximum value exceeds the Betz‐Joukowsky limit. We have developed a series expansion for the maximum power coefficient in powers of the Mach number that unifies all the cases (compressible and incompressible) in the same simple expression: .     

Overview of amorphous silicon photovoltaic module development

Amorphous silicon (a-Si) photovoltaic (PV) modules are generally manufactured in a single-junction p-i-n configuration and in sites ranging from a few square centimeters to about 4000 cm². These modules are being used in a number of both indoor and outdoor low wattage (less than 20 W_p (peak watt)) applications, but have not found widespread use in most higher wattage power applications owing to relatively low stabilized conversion efficiencies (approximately 4%–5%). The recent improvements in the performance and stability of a-Si based multijunction modules indicates that these modules should soon start to appear in the higher wattage outdoor applications. When multijunction modules are manufactured in totally automated facilities, the manufacturing costs should fall below $1 per W_p, and these modules should then start penetrating the grid-connected power generation markets.     

Life cycle assessment of a multi-megawatt wind turbine

At the present moment in time, renewable energy sources have achieved great significance for modern day society. The main reason for this boom is the need to use alternative sources of energy to fossil fuels which are free of CO₂ emissions and contamination. Among the current renewable energy sources, the growth of wind farms has been spectacular. Wind power uses the kinetic energy of the wind to produce a clean form of energy without producing contamination or emissions. The problem it raises is that of quantifying to what extent it is a totally clean form of energy. In this sense we have to consider not only the emissions produced while they are in operation, but also the contamination and environmental impact resulting from their manufacture and the future dismantling of the turbines when they come to the end of their working life. The aim of this study is to analyse the real impact that this technology has if we consider the whole life cycle. The application of the ISO 14040 standard [ISO. ISO 14040. Environmental management – life cycle assessment – principles and framework. Geneva, Switzerland: International Standard Organization; 1998.] allows us to make an LCA study quantifying the overall impact of a wind turbine and each of its components.Applying this methodology, the wind turbine is analysed during all the phases of its life cycle, from cradle to grave, with regard to the manufacture of its key components (through the incorporation of cut-off criteria), transport to the wind farm, subsequent installation, start-up, maintenance and final dismantling and stripping down into waste materials and their treatment.     

Study of aerodynamical interference for a wind turbine

A two-dimensional interference model of upwind wind turbine, based on NREL Phase VI, was simulated by an available Navier–Stokes solver under parallel process. The simulation domain was divided into a stationary tower domain and a sliding blade domain with varying geometric factors, including blade chord to tower diameter ratio and tower-blade gap to tower diameter ratio, to figure out the unsteady problem. The turbulence model was treated with SST k–ω turbulence model and the boundary layers around the solid walls were refined by the y⁺ value. The simulated results of velocity field were compared with the potential cylinder flow, and some phenomena were exhibited, including the movement of stagnation point of tower, the skewed wake of tower and the excess of velocity in the field. The lift force coefficient of blade was different from the ideal angle of attack for the blade passing in front of the potential cylinder flow.     

Innovative improvement of a drag wind turbine performance

Drag type wind turbines have strong potential in small and medium power applications due to their simple design. However, a major disadvantage of this design is the noticeable low conversion efficiency. Therefore, more research is required to improve the efficiency of this design. The present work introduces a novel design of a three-rotor Savonius turbine with rotors arranged in a triangular pattern. The performance of the new design is assessed by computational modeling of the flow around the three rotors. The 2D computational model is firstly applied to investigate the performance of a single rotor design to validate the model by comparison with experimental measurements. The model introduced an acceptable accuracy compared to the experimental measurements. The performance of the new design is then investigated using the same model. The results indicated that the new design performance has higher power coefficient compared with single rotor design. The peak power coefficient of the three rotor turbine is 44% higher than that of the single rotor design (relative increase). The improved performance is attributed to the favorable interaction between the rotors which accelerates the flow approaching the downstream rotors and generates higher turning moment in the direction of rotation of each rotor.     

LCA sensitivity analysis of a multi-megawatt wind turbine

During recent years renewables have been acquiring gradually a significant importance in the world market (especially in the Spanish energetic market) and in society; this fact makes clear the need to increase and improve knowledge of these power sources. Starting from the results of a Life Cycle Assessment (LCA) of a multi-megawatt wind turbine, this work is aimed to assess the relevance of different choices that have been made during its development. Looking always to cover the largest possible spectrum of options, four scenarios have been analysed, focused on four main phases of lifecycle: maintenance, manufacturing, dismantling, and recycling. These scenarios facilitate to assess the degree of uncertainty of the developed LCA due to choices made, excluding from the assessment the uncertainty due to the inaccuracy and the simplification of the environmental models used or spatial and temporal variability in different parameters. The work has been developed at all times using the of Eco-indicator99 LCA method.