On the role of surface roughness in the aerodynamic performance and energy conversion of horizontal wind turbine blades: a review

Renewable energy is one of the main pillars of sustainable development, especially in developing economies. Increasing energy demand and the limitation of fossil fuel reserves make the use of renewable energy essential for sustainable development. Wind energy is considered to be one of the most important resources of renewable energy. In North African countries, such as Egypt, wind energy has an enormous potential; however, it faces quite a number of technical challenges related to the performance of wind turbines in the Saharan environment. Seasonal sand storms affect the performance of wind turbines in many ways, one of which is increasing the wind turbine aerodynamic resistance through the increase of blade surface roughness. The power loss because of blade surface deterioration is significant in wind turbines. The surface roughness of wind turbine blades deteriorates because of several environmental conditions such as ice or sand. This paper is the first review on the topic of surface roughness effects on the performance of horizontal‐axis wind turbines. The review covers the numerical simulation and experimental studies as well as discussing the present research trends to develop a roadmap for better understanding and improvement of wind turbine performance in deleterious environments. Copyright © 2016 John Wiley & Sons, Ltd.     

Harnessing wind energy at Manjil area located in north of Iran

Manjil is located in north of Iran and is capable of harnessing wind energy for electricity purpose. There are about six different stations in that region which all of them have excellent record of wind speed in different months of the year. It is one of the best locations in the world for installing wind turbine and the utility department has invested a lot of money to establish wind farms in this region. Statistical analysis for six different installed stations show that it is one of the best locations in the world for establishing wind farms. In this paper, wind speed at different sites in Manjil has been analyzed and it shows that it has a great potential for harnessing wind energy. So far, there has been only 51 wind turbines installed in the area and there is a plan to increases that amount in the future.     

Wind power systems for zero net energy housing in the United States

This work investigates the feasibility of renewable energy housing development in the U.S. using wind power and solar thermal systems to attain zero net energy consumption. The over all objective was to determine how the wind power and solar thermal system designs and economics differ with various climates, wind and solar resources, energy prices, and state incentives, such as net-metering. Five U.S. cities, one in each of the five climate zones, were selected for this study based on their potential for wind power. A zero net energy housing design tool was developed in order to analyze and compare various system designs. The energy performance and economics of the designs were compared for various sizes of housing development, for seven turbine models, and selected heating systems. The results suggest that while there are some economical options for wind powered zero net energy housing developments, they are generally more expensive (except in the warmest climate zone) than housing with natural gas heating. In all of the cases, the economies of scale for large-scale wind turbines gave more of an economic advantage than net-metering programs gave small- and medium-scale wind turbines.     

Wind power development and policies in China

The People's Republic of China foresees a target of 30 GW for installed wind power capacity by 2010 (2008: 12 GW). This paper reports on the technical and economic potentials of wind power, the recent development, existing obstacles, and related policies in China. The barriers to further commercialization of the wind power market are important and may deter the 100 GW capacity target of the Chinese government by 2020. The paper concludes that the diffusion of wind power in China is an important element for not only reducing global greenhouse gas emissions, but also for worldwide progress of wind power technology and needed economies of scale.     

Renewable energy and macroeconomic efficiency of OECD and non-OECD economies

This article analyzes the effects of renewable energy on the technical efficiency of 45 economies during the 2001–2002 period through data envelopment analysis (DEA). In our DEA model, labor, capital stock, and energy consumption are the three inputs and real GDP is the single output. Increasing the use of renewable energy improves an economy's technical efficiency. Conversely, increasing the input of traditional energy decreases technical efficiency. Compared to non-OECD economies, OECD economies have higher technical efficiency and a higher share of geothermal, solar, tide, and wind fuels in renewable energy. However, non-OECD economies have a higher share of renewable energy in their total energy supply than OECD economies.     

Rapid sizing of a hydrogen-battery storage for an offshore wind farm using convex programming

This paper carries out a comprehensive analysis on an offshore wind farm equipped with a hybrid storage comprised of hydrogen and battery, from the perspective of economic effectiveness. To rapidly evaluate the system economy, a computationally efficient convex program that takes the nonlinear storage efficiencies into account is provided, which can simultaneously and synergistically optimize the storage sizing and energy management over a long offshore wind cycle. In the analysis, a case study on the optimal configuration and operation of the hybrid storage is thoroughly investigated, answering what the scalings are and how the storage functions in the offshore wind farm. Comparisons to other offshore wind farms with none or only one storage type further demonstrate the advantage of combining hydrogen plant and battery. Influences of the offshore wind electricity price of grid parity and hydrogen price on the system economies, in the terms of total annual cost, net annual profit and hydrogen production cost, are also discussed, revealing sensitivity and dependency of the scalings. Finally, this paper presents the future potential of applying hydrogen plant in the offshore wind farm, from the angles of hydrogen production cost and energy saving.     

葫芦岛沿海地区风资源分析

以葫芦岛市沿海三站(连山、兴城、绥中)2006年逐日逐时10min平均风速资料为例,计算几项风资源评估参数,结果表明:葫芦岛市沿海地区均属于风能可利用区;各站风资源月分布均呈现双峰型,第一个高峰为2、3、4、5月,第二个高峰在10月;目前葫芦岛市连山站的位置距海岸较远,但结果仍表明该地的风资源比兴城、绥中丰富。     

Collaboration in future coal trade in East and South-east Asia

Countries in East and South-east Asia plan to provide a considerable part of future energy supplies from coal. The coal must mostly be imported from countries outside the region. Considerable economies in the transport of coal can be achieved by using large ships. We examine the proposition that the economies of scale justify regional collaboration in one or more trans-shipment depots at which large loads from the supplier are broken up and distributed in small vessels to small consumers.     

Unleashing business opportunities for wind energy

Internationally successful models for the implementation of wind energy are presented and suggested for the Australian electricity supply systems. With Perth being the congress host and Western Australia’s known good wind resource, particular emphasis is given to the WA South West Interconnected System (SWIS). In the current framework, energy legislation is State Government’s responsibility. In the light of the Kyoto Protocol the carbon dioxide emissions of the SWIS are indicated, the associated external cost are estimated and the Greenhouse Gas emissions offset potential from wind power is outlined. The socioeconomic advantages of wind energy are depicted. Recommendations are made on how these sustainable advantages might be utilised to unleash business opportunities for the private sector, which is the cornerstone of free enterprise economies.     

What hinder the further development of wind power in China?—A socio-technical barrier study

Promoting wind power is a long-term strategy of China to respond to both energy shortage and environmental pollution. Stimulated by various incentive policies, wind power generation in China has achieved tremendous growth, with the cumulative installed capacity being the largest worldwide for five consecutive years since 2010. However, obstructed by various barriers, wind power provides only 2.6% of national electricity generation in China, despite the strong support from the government. From a socio-technical transition perspective, this paper aims to systematically analyze the barriers hindering the further development of China's wind power. A wind power niche model is established to illustrate the complex interactions among actors in the wind power industry and electricity supply regime. Then, qualitative content analysis is adopted to process the related evidence and data, and four categories of socio-technical barriers are identified, including technology, governance, infrastructure and culture barriers. The study shows that various interrelated barriers form a blocking mechanism which prohibits the further development of wind power in China. Policy suggestions are proposed to eliminate the barriers and further empower the wind power niche. The lesson learned from China can offer useful references for other economies to promote wind power industries of their own.     

A STEP toward understanding wind power development policy barriers in advanced economies

A widely accepted premise regarding wind power development policy is that implementation of economic policy instruments, which are designed to close the cost gap between wind power and entrenched fossil fuel power generation technologies, will significantly catalyze enhanced levels of wind power development activity. This paper contests this premise by arguing that non-economic barriers to wind power development have the capacity to significantly inhibit wind power development in industrialized nations despite the implementation of economic policy instruments. Forces which deter wind power development in four economically advanced economies that exhibit phlegmatic progress in wind power development – Australia, Canada, Japan and Taiwan – are identified and amalgamated into a STEP framework describing social, technical, economic and political forces that inhibit wind power development. The conclusions of this analysis are twofold. First, failure to mitigate these STEP forces may undermine the efficacy of any given economic policy instrument that aims to close the cost gap between wind power and entrenched generation technologies. Second, attempts to mitigate these impediments might represent a way to achieve better policy results with less government financial commitment.     

Robust pitch controller for output power levelling of variable-speed variable-pitch wind turbine generator systems

A robust pitch (RP) controller for variable-speed variable-pitch wind turbine generator systems (VSVPWTGS) is presented. The controller can not only level the wind energy conversion but also be applicable in a wide wind speed region even subject to large parametric or non-parametric disturbances. VSVP-WTGS consists of multi-subsystems with different time scales. The dominant `slow? dynamics are non-affine and high nonlinear. By considering `fast? subsystems as perturbations to the `slow? one, the dynamics of VSVP-WTGS can be represented by a nominal model and an error one. The RP controller is composed of a nominal inverse-system controller and a robust compensator. With the nominal inverse-system controller, the nominal closed-loop system can track its reference dynamics. With the robust compensator, turbine parameter uncertainties and non-parametric perturbations are tolerated. The performance of the RP controller is confirmed through theoretical analyses and computer simulations. Results show that RP controller can operate in a wider wind speed region robustly compared with a proportional-integral-derivative controller. Compared with other nonlinear controllers, the RP controller is simpler and can be more easily extended to other kinds of WTGS.     

Controllable and affordable utility-scale electricity from intermittent wind resources and compressed air energy storage (CAES)

World wind energy resources are substantial, and in many areas, such as the US and northern Europe, could in theory supply all of the electricity demand. However, the remote or challenging location (i.e. offshore) and especially the intermittent character of the wind resources present formidable barriers to utilization on the scale required by a modern industrial economy. All of these technical challenges can be overcome. Long distance transmission is well understood, while offshore wind technology is being developed rapidly. Intermittent wind power can be transformed to a controllable power source with hybrid wind/compressed air energy storage (CAES) systems. The cost of electricity from such hybrid systems (including transmission) is affordable, and comparable to what users in some modern industrial economies already pay for electricity. This approach to intermittent energy integration has many advantages compared to the current strategy of forcing utilities to cope with supply uncertainty and transmission costs. Above all, it places intermittent wind on an equal technical footing with every other generation technology, including nuclear power, its most important long-term competitor.     

Balance of power

Energy policy in today's world is directed essentially by three main objectives: security of supply, efficiency of supply, and social and environmental sustainability. But given the varied characteristics of the many societies concerned, the emphasis in a particular region may be quite different. In effect, energy policy means very different things to Latin American countries than to the developed economies of Europe and the United States. The countries in Latin America do not yet satisfy the energy needs of much of their people, who must often rely on burning wood for heating and cooking. The additional objective of social justice and social equity becomes relevant. While some countries in the region are still facing low levels of electrification, others are crippled by insufficient investment in energy infrastructure. Finally, the region is resource rich, with a diversity of energy options (coal, gas, hydro, biomass, wind) available but unevenly distributed among the countries. Hence, cross-border supply decisions to foster the development of given technologies are always being discussed. As energy demand increases with economic development, Latin American electricity growth rates have been greater than 5% per year during the last decade. Yearly needs for investment in energy infrastructure in the region are comparable with those of the United States and Canada put together. South America alone will require about US$90 billion of investment in the power sector in the next ten years.     

An analysis of wind power density derived from several wind speed density functions: The regional assessment on wind power in Malaysia

In wind turbine design and site planning, the probability distribution of wind speed becomes critically important in estimating energy production. The utilization of accurate distribution will minimize the uncertainty in wind resource estimates, and consequently, it will improve the result in the site assessment phase of planning. In general, different region will have different wind regime. Hence, it is reasonable that different wind speed distribution will be found for different region. In this study, the features of wind power density based on the dependency of the suitable wind speed density have been obtained analytically using transformation technique. Since the wind power density has been obtained, the mean power density which is referred as an important indices related to the estimation of potential wind energy have been obtained by using the concept of raw moment and Monte Carlo approach. An analysis of semivariogram indicates the lack of spatial correlation of the wind power in Malaysia. The map of the mean power density over Malaysia indicates that several regions such as northeast, northwest and southeast region of Peninsular Malaysia and southern region of Sabah are found as the best region to be further investigated in the future for the wind energy development.     

Design of HAWT airfoils tailored for active flow control

This study describes a methodology for designing airfoils suitable to employ actuation in a wind energy environment. The novel airfoil sections are baptized wind energy actuated profiles (WAP). A genetic algorithm‐based multi‐objective airfoil optimizer is formulated by setting two cost functions: one cost function for wind energy performance and the other representing actuation suitability. The wind energy cost function compares the candidate airfoils' performance with ‘reference’ wind energy airfoils, considering a probabilistic approach to include the effects of turbulence and wind shear. The actuation suitability cost function is developed considering horizontal axis wind turbines active stall control, including two different control strategies designated by ‘enhanced’ and ‘decreased’ performance. Two different actuation types are considered, namely, boundary layer transpiration and dielectric barrier discharge plasma. Results show that using WAP airfoils provides much higher control efficiency than adding actuation on reference wind energy airfoils, without detrimental effects in non‐actuated operation. The WAP sections yield an actuator employment efficiency that is two to four times larger than those obtained with reference wind energy airfoils, at equivalent wind energy performance. Regarding geometry, and compared with typical wind energy airfoils, WAP sections for decreased performance display an upper surface concave aft region, while for increased performance, a convex upper surface aft region is obtained. The present study emphasizes that there is much to gain in designing airfoils from the beginning to include actuation effects, especially compared with employing actuation on already existing airfoils. The results demonstrate the potential of including actuation effects in the airfoil design process, thus enabling novel horizontal axis wind turbines control strategies. Copyright © 2017 John Wiley & Sons, Ltd.     

An economic perspective on experience curves and dynamic economies in renewable energy technologies

This paper analyzes dynamic economies in renewable energy technologies. The paper has two contributions. The first is to test the robustness of experience in solar photovoltaic, solar thermal and wind energy to the addition of an explicit time trend, which has been done in experience studies for other industries, but not for renewable energy technologies. Estimation is carried out on the assumption that cumulative capacity, industry production, average firm production, and electricity generation affect experience and thus the fall in price. The second contribution is to test the impact of R&D on price reduction. In general cumulative experience is found to be highly statistically significant when estimated alone, and highly statistically insignificant when time is added to the model. The effect of R&D is small and statistically significant in solar photovoltaic technology and statistically insignificant in solar thermal and wind technologies.     

Multi‐hazard reliability assessment of offshore wind turbines

A probabilistic framework is developed to assess the structural performance of offshore wind turbines under multiple hazards. A multi‐hazard fragility surface of a given wind turbine support structure and the seismic and wind hazards at a specific site location are incorporated into the probabilistic framework to assess the structural damage due to multiple hazards. A database of virtual experiments is generated using detailed three‐dimensional finite element analyses of a set of typical wind turbine systems subject to extreme wind speeds and earthquake ground motions. The generated data are used to develop probabilistic models to predict the shear and moment demands on support structures. A Bayesian approach is used to assess the model parameters incorporating the information from virtual experiment data. The developed demand models are then used to estimate the fragility of the support structure of a given wind turbine. As an example of the proposed framework, the annual probabilities of the occurrence of different structural damage levels are calculated for two identical wind turbines, one located in the Gulf of Mexico of the Texas Coast (prone to hurricanes) and one off the California Coast (a high seismic region). Copyright © 2014 John Wiley & Sons, Ltd.     

Future changes in wind energy resource over the Northwest Passage based on the CMIP6 climate projections

The preferential use of renewable energy sources such as wind power has been proposed as one of the most effective strategies in reducing greenhouse gas emissions in the energy sector. However, wind energy resources are vulnerable to climate change, which might have a huge impact on the area under consideration. In this research, we used the wind speed data obtained from the seven coupled global climate models in the Coupled Model Intercomparison Project Phase 6 (CMIP6) to quantitatively analyze the differences in wind energy resource (WER) between the future and the historical period, geared toward understanding the impact of climate change on wind energy sources. Relevant results show that the future WER would decreases below 20% in the region south of the Northwest Passage, while would significantly increase in the north region of 72°N (specifically in the Beaufort Sea). Further, reports predict that by the end of the 21st century, if no interventions are made to mitigate greenhouse gas emissions, the northern region's WER would increase even more with some grid points exceeding 30% and have a significant growth trend, but at the same time the intra‐annual variability in these region would also increase significantly with some grid points exceeding 140% of that in the historical period. Moreover, the maximum wind speed values would encounter a noteworthy increase of up to 20%, which will bring great challenge to the development of wind energy in these region. Although the current models still have great uncertainties in the future climate prediction, our work still has certain guiding significance for the future development of wind energy over the Northwest Passage.