Wind energy in urban areas : Concentrator effects for wind turbines close to buildings

One often overlooked alternative to conventional large scale wind farms is to produce wind energy close to where we need it such as in the built environment. In this case we do not need to transport the energy and we keep rural areas untouched. However, the built environment has lower average wind speeds and higher turbulence levels. What means do we have to compensate for this? In this article, Sander Mertens, TU Delft, Holland describes some of the specific technology and design issues in the use of wind energy in buildings.     

扩散体建筑风能利用的风洞试验

扩散体建筑是用来汇集风能的建筑形式.通过风洞试验,研究了3种具有不同截面形状的扩散体建筑对增强风速及强化风能的效果.试验结果表明:截面形状为肾形的建筑其风力集结效果最好.可利用风能的高度范围较大;截面形状为椭圆形和扩压风道形的建筑也具有良好的效果.通过对试验数据与模拟数据比较分析可见,风洞试验得到的数据与模拟结果较为吻合,既验证了数值模拟结果的准确性,又为建筑环境中风能利用的研究奠定了试验基础.     

Airflow in courtyard and atrium buildings in the urban environment: a wind tunnel study

A wind tunnel study was carried out to investigate the airflow through courtyard and atrium building models located within an urban setting and exposed to an urban atmospheric boundary layer. Ventilation strategies resulting from the use of different courtyard and atrium pressure regimes (positive pressure and suction) were examined. The model buildings were monitored both in isolation and in idealised urban environments of varying group layout densities. The effect of wind direction was also observed. The results from the study suggest that the open courtyard in an urban environment had a poor ventilation performance whilst an atrium roof with many openings operating under a negative (suction) pressure regime was the most effective. Changing the wind direction from perpendicular to the building façades to a 45° incidence angle had the effect of making the differences in the observed flows between all the models much smaller.     

KiteGen: A revolution in wind energy generation

Control of tethered airfoils is investigated, in order to devise a new class of wind generators to overcome the main limitations of the present wind technology, based on wind mills. A model from the literature is used to simulate the dynamic of a kite whose lines are suitably pulled by a control unit. Energy is generated by a cycle composed of two phases, indicated as the traction and the drag one. The kite control unit is placed on the arm of a vertical axis rotor, connected to an electric drive able to act as a generator when the kite pulls the rotor and as a motor in dragging the kite against the wind. Control is obtained by “fast” implementation of Nonlinear Model Predictive Control (NMPC). In the traction phase the control is designed such that the kite pulls the rotor arm, maximizing the amount of generated energy. When energy cannot be generated anymore, the control enters the drag phase and the kite is driven to a region where the energy spent to drag the rotor is a small fraction of the energy generated in the traction phase, until a new traction phase is undertaken. Simulation results are presented, showing encouraging performances.     

建筑环境中的风能利用

城区建筑环境中的风场有紊流加剧、风速降低的特点.因此,风力强化和集中的问题需要得到解决.目前有非流线体型、平板型和扩散体型3种空气动力集中形式.文章应用CFD数值模拟软件分别对3种基本空气动力集中建筑模型的风速进行了模拟计算,探讨了最佳的风能利用形式.     

Technoeconomic analysis of electricity generation from wind energy in Kutahya,Turkey

Conventional energy usage has various environmental effects that cause global warming. Renewable energy sources are thus more favorable because they have nearly zero emission. Wind energy, among the various renewable sources, finds increasing usage, concurrent with developing technology. In addition, wind is an infinite energy source. In this study, the electricity-generation ability of Kutahya has been investigated. With this aim, wind data, from the measurement station located on Bunelek Hill, Kutahya, have been collected for a period of 36 months (July 2001–June 2004). From the collected data, the electricity generated has been calculated for different types of wind turbines. The calculations have been based on the electricity requirement of the main campus of the Dumlupinar University. Finally, the economic evaluation has been analyzed using life-cycle cost analysis. For the analysis of the economical aspects, the social and CO₂ costs have also been taken into account.     

Local employment impact from competing energy sources: Shale gas versus wind generation in Texas

The rapid development of both wind power and of shale gas has been receiving significant attention both in the media and among policy makers. Since these are competing sources of electricity generation, it is informative to investigate their relative merits regarding local job creation. We use a panel econometric model to estimate the historical job-creating performance of wind versus that of shale oil and gas. The model is estimated using monthly county level data from Texas from 2001 to 2011. Both first-difference and GMM methods show that shale-related activity has brought strong employment to Texas. For example, based on the 5482 new directional/fractured wells drilled in Texas in 2011, the estimates imply that between 25,000 and 125,000 net jobs were created in that year alone. We did not, however, find a corresponding impact on wages. Our estimations did not identify a non-negligible impact from the wind industry on either local employment or wages.     

Indian wind power : Wind as a supplementary energy source in India

Wind energy programmes started in India during the 1980s and gained momentum during 1992–1993 mainly due to the participation of private developers who saw wind as a viable alternative source of power for their existing industrial activities. The liberal incentives provided by the Government of India like 100 per cent depreciation in the first year itself, a five year tax holiday; wheeling/banking, and third party sale by different state governments also gave a big boost to the establishment of wind farms. Dr A. Jagadeesh, Wind Energy Specialist and Consultant, India highlights the current status and actions needed for further development of a wind power industry in India.     

Fruitful symbiosis: Why an export bundled with wind energy is the most feasible option for North African concentrated solar power

The idea of generating electricity in North Africa using concentrating solar thermal power (CSP) has been around for some time now but has recently gained momentum through the Mediterranean Solar Plan (MSP) and the formation of the Desertec Industrial Initiative. This paper argues that while the large-scale deployment of CSP in North Africa does not seem economically attractive for either European or African institutions or countries on their own at present, combining domestic use and electricity exports could be profitable for both parties. A detailed economic portfolio covering both solar and wind power plants can achieve competitive price levels, which would accelerate the diffusion of solar technology in North Africa. This portfolio could be financed partially by exporting electricity from solar thermal plants in North Africa via HVDC interconnections to European consumers. Sharing the costs in this way makes it possible to generate solar electricity for the domestic market at a reasonable cost. Some of the electricity produced from the solar power plants and wind parks in North Africa is sold on European energy markets in the form of a long-term contracted solar–wind portfolio, which would qualify for support from the financial incentive schemes of the European Member States (e.g. feed-in tariffs). This transfer of green electricity could help to meet the targets for energy from renewable energy sources (RES) in the EU Member States as the new EU Directive of 2009 opened the European electricity market to imports from third states.     

Wind energy status of Iran: Evaluating Iran's technological capability in manufacturing wind turbines

Iran, as a developing country, will be confronted with a significant increase in electricity demand in future years. Being a petroleum producing country has resulted in extreme subsidies for energy production from fossilized resources such as oil and gas. This issue is one of the most important factors regarding underdevelopment of renewable energies in Iran. Expansive use of fossil resources in providing the necessary energy has resulted in Iran being among the 20 countries that have a share in the 75% spread of greenhouse gases. This issue has resulted in greater attention on behalf of the energy sectors policy makers regarding renewable energies, especially wind. Awareness regarding the current condition of each system is the first step for optimum policy making. On this basis, analyzing Iran's wind conditions and assessing its technological capabilities is considered a pre-requisite for the wind sectors policy making. This paper aims at studying Iran's wind energy status in the form of available capacities, power production, wind power plant characteristics, principal agents and existing protective laws. Also, the main focus of this paper is on evaluating Iran's potential and effective technological capabilities for producing the main parts of wind turbines in different sizes. In order to fulfill this task, sector-level technological capabilities are defined. Then by analyzing active organizations in this field, Iran's capability level will be determined and by comparing it with the ideal conditions, Iran's technological gaps will be identified. The reasons for the creation of such shortcomings will also be introduced from different aspects in the form of the Atlas model. Finally, Iran's potential capabilities in resolving technological shortcomings will be identified.     

Baseload wind energy: modeling the competition between gas turbines and compressed air energy storage for supplemental generation

The economic viability of producing baseload wind energy was explored using a cost-optimization model to simulate two competing systems: wind energy supplemented by simple- and combined cycle natural gas turbines (“wind+gas”), and wind energy supplemented by compressed air energy storage (“wind+CAES”). Pure combined cycle natural gas turbines (“gas”) were used as a proxy for conventional baseload generation. Long-distance electric transmission was integral to the analysis. Given the future uncertainty in both natural gas price and greenhouse gas (GHG) emissions price, we introduced an effective fuel price, p_NGeff, being the sum of the real natural gas price and the GHG price. Under the assumption of p_NGeff=$5/GJ (lower heating value), 650 W/m² wind resource, 750 km transmission line, and a fixed 90% capacity factor, wind+CAES was the most expensive system at ¢6.0/kWh, and did not break even with the next most expensive wind+gas system until p_NGeff=$9.0/GJ. However, under real market conditions, the system with the least dispatch cost (short-run marginal cost) is dispatched first, attaining the highest capacity factor and diminishing the capacity factors of competitors, raising their total cost. We estimate that the wind+CAES system, with a greenhouse gas (GHG) emission rate that is one-fourth of that for natural gas combined cycle plants and about one-tenth of that for pulverized coal plants, has the lowest dispatch cost of the alternatives considered (lower even than for coal power plants) above a GHG emissions price of $35/tC_equiv., with good prospects for realizing a higher capacity factor and a lower total cost of energy than all the competing technologies over a wide range of effective fuel costs. This ability to compete in economic dispatch greatly boosts the market penetration potential of wind energy and suggests a substantial growth opportunity for natural gas in providing baseload power via wind+CAES, even at high natural gas prices.     

Paradigm shift in urban energy systems through distributed generation: Methods and models

The path towards energy sustainability is commonly referred to the incremental adoption of available technologies, practices and policies that may help to decrease the environmental impact of energy sector, while providing an adequate standard of energy services. The evaluation of trade-offs among technologies, practices and policies for the mitigation of environmental problems related to energy resources depletion requires a deep knowledge of the local and global effects of the proposed solutions. While attempting to calculate such effects for a large complex system like a city, an advanced multidisciplinary approach is needed to overcome difficulties in modeling correctly real phenomena while maintaining computational transparency, reliability, interoperability and efficiency across different levels of analysis. Further, a methodology that rationally integrates different computational models and techniques is necessary to enable collaborative research in the field of optimization of energy efficiency strategies and integration of renewable energy systems in urban areas. For these reasons, a selection of currently available models for distributed generation planning and design is presented and analyzed in the perspective of gathering their capabilities in an optimization framework to support a paradigm shift in urban energy systems. This framework embodies the main concepts of a local energy management system and adopts a multicriteria perspective to determine optimal solutions for providing energy services through distributed generation.     

Electric energy generation from small-scale solar and wind power in Brazil: The influence of location,area and shape

Power production from renewable sources is identified as one of the tools to attain sustainable development in economic and social terms in Brazil. Awareness of how to prioritize renewable energy sources and technologies becomes increasingly important. Solar and wind energy have been highlighted in this context as being clean, safe and also relatively mature technologies. In addition, they are also renowned for having great energy potential and allowing different mounting options for energy harvesting systems. This article seeks to contribute to the knowledge of the effects that the key attributes, location, area and shape, of a site can have on the potential of renewable generation. In order to incorporate these attributes into an integrated analysis, a comparison method is developed and subsequently applied in a case study for two Brazilian cities. Results indicate that the amount of energy obtained by a given power generation system can undergo large variations depending on the characteristics of attributes such as site location, area and shape. This variation may ultra-pass 200%, in some cases, which demonstrates the importance of a better understanding of the role of these attributes in determining energy production.     

A compact,high efficiency contra-rotating generator suitable for wind turbines in the urban environment

This paper is concerned with the design, development and performance testing of a permanent magnet (PM) generator for wind turbine applications in urban areas. The radially interacting armature windings and magnet array are carried on direct drive, contra-rotating rotors, resulting in a high torque density and efficiency. This topology also provides improved physical and mechanical characteristics such as compactness, low starting torque, elimination of gearboxes, low maintenance, low noise and vibration, and the potential for modular construction. The design brief required a 50 kW continuous rated prototype generator, with a relative speed at the air-gap of 500 rpm. A test rig has been instrumented to give measurements of the mechanical input (torque and speed) and electrical output (voltage, current and power) of the generator, as well as temperature readings from inside the generator using a wireless telemetry device. Peak power output was found to be 48 kW at a contra-rotating speed of 500 rpm, close to the design target, with an efficiency of 94%. It is anticipated that the generator will find application in a wide range of wind turbine designs suited to the urban environment, e.g. types sited on the top of buildings, as there is growing interest in providing quiet, low cost, clean electricity at point of use.     

Power conversion in renewable energy systems: A review advances in wind and PV system

Grid‐connected photo voltaic (PV) systems are being developed very fast and systems from a few kW to tenths of a MW are now in operation. As an important source of distributed generation (DS) the PV systems need to comply with a series of standard requirements in order to ensure the safety and the seamless transfer of the electrical energy to the grid. Multilevel voltage source converters (VSC) is a heart of the PV system and are emerging as an important power converter options for low, medium, and high‐power applications. These VSCs have bought numerous advantages, especially in renewable energy systems such as PV and wind energy systems. In this article, several topologies of VSCs, which brings together some concepts from traditional converters and multi‐level converters, are presented. Also, several control strategies for controlling current, voltage, active power and reactive power have also been reviewed. Various topologies with their technical aspects have been reviewed and the best suitable topology and control scheme for grid connected PV and wind energy systems has been suggested. Copyright © 2016 John Wiley & Sons, Ltd.     

储能电池在风光互补发电系统中的容量配置分析

储能电池是分布式发电系统的关键组件。增加储能电池的容量可以提高发电系统的可靠性,但会增加系统的投资和运行费用。基于上海地区全年8 760 h的气象数据,计算了风光互补发电系统在不同储能容量下的负荷缺电率和能量溢出率的变化。对于独立的风光互补发电系统,在满足能量溢出率小于0.3的情况下,如果系统缺电率维持在1%左右时,需要配置3天的储能容量;如果系统缺电率为0,则需要配置5天的储能容量。     

Saving energy is not easy: An impact assessment of Dutch policy to reduce the energy requirements of buildings

The Dutch Government stimulates the application of energy efficiency measures to reduce the energy requirements of buildings, which are responsible for about 20% of the Dutch CO₂ emissions. For our assessment, we followed a qualitative approach, due to a lack of data. We reviewed the mix of policy instruments and used stakeholder surveys and interviews. We found that energy use is not very likely to decline fast enough to achieve the Dutch policy targets for 2020. For new buildings, the policy mix works well, but its contribution to the policy targets is limited. For non-residential buildings the current Act, which obliges enterprises to take cost-effective measures, could be enforced to a greater degree. For privately owned homes a more compelling policy is needed. An alternative policy option would be to make taxation dependent on the energy label of residential houses. This would stimulate residents to take action while retaining the desired autonomy. For rental housing, binding agreements between municipalities and housing corporations may lead to more energy saving measures. Finally, we conclude that the Dutch energy tax is an important pillar of the current policy. It provides higher cost-effectiveness of energy saving measures and legitimates more strict energy efficiency standards.     

Wind energy deployment in wind farm aging context. Appraising an onshore wind farm enlargement project: A contingent valuation study in the Center of Italy

In many European countries, the most suitable onshore sites for wind installations are almost fully engaged. Furthermore, the existing onshore wind farm capacity should be replaced in the next 10 years because the existing wind power plants are progressively aging in terms of depreciation, degradation and technological obsolescence. Without an adequate policy intervention, the Italian installed wind power capacity would return to the size of 2011 by 2030. In this scenario, the main opportunity for further growth in wind energy generation is wind farm enlargement. The aim of this paper is to assess the welfare change due to the proposed enlargement project. First, we investigate whether existing wind farms affect respondents' attitude and perception toward the potential enlargement of the wind farm by using the contingent valuation method. Second, we investigate the perception of the risk associated with the enlargement of a wind farm. In this case, we explicitly consider respondents' heterogeneity in perceiving the new project externalities. To achieve this objective, we use willingness to pay and willingness to accept measure to appraise welfare change due to the enlargement project. Each of these measures has been elicited jointly regarding the respective appraised externality impact perceived by the respondents. The individual and aggregate findings of this research can offer useful insights for planning and design enlargement schemes to achieve further growth in wind energy generation.